RQRA 4th Edition by BSolution

TRUCK TYRE MAGAZINE

ON THE MEND

Repairing a puncture in 10 simple steps with a Minicombi unit

PERFECT PIT WORK

How to safely detach and reinstall a wheel without causing damage

ISSUE 4 MARCH 2010

BRIDGESTONE

| CONTENTS

8 TRUCK TYRE MAGAZINE

ON THE MEND

Repairing a puncture in 10 simple steps with a Minicombi unit

PERFECT PIT WORK

How to safely detach and reinstall a wheel without causing damage

CONTENTS Choosing the right repair procedure

The pros and cons of the main forms of repair

Repairing a puncture with Minicombi ISSUE 4 MARCH 2010

real QUESTIONS real ANSWERS Bridgestone Middle East & Africa FZE P.O. Box 16813, Jebel Ali Free Zone Dubai, UAE For correspondence with this publication please write to us through our postal address or by email to realanswers@bridgestone.ae. An electronic version of this publication is available at www.bridgestone-mea.com

Perfecting pit work Mismatch spells trouble

For editorial enquiries, contact Oliver Ephgrave, Editor oliver.ephgrave@npimedia.com Tel: +9714 4243600

MARCH 2010 real QUESTIONS real ANSWERS

The importance of matching dual tyres

The truck drivers that make Formula One happen P.O. Box 500573, Office 704 Executive Heights, Dubai, UAE Tel: +9714 4243600 Fax: +9714 3908022

The correct way to detach and reinstall a wheel

Burning rubber Nicholas Publishing International FZ-LLC

How to ďŹ x a nail hole with a popular repair unit

BRIDGESTONE

| FOREWORD

FOREWORD Needless to say, the proper selection and usage of tyres is vital in reducing ﬂeets’ operating costs and downtime. Yet economy and efﬁciency can be improved further if tyres are maintained in the correct manner. Therefore, in our fourth issue of Real Questions Real Answers, we have focused on two crucial maintenance procedures: pit work and repair. Our opening article explains the various forms of repair, such as hot and cold vulcanisation. This is followed by a step-by-step guide to using the invaluable MINICOMBI repair unit. We would like to thank REMA TIP TOP Germany for their contribution on these two articles. Next, we outline the best practice guidelines for detaching and reinstalling a wheel, while the following article highlights the importance of matching dual tyres.

The magazine wraps up with an interview with James Sullivan, truck driver for Bridgestone Motorsport, who outlines the many challenges of transporting tyres to F1 races. As ever, we welcome your feedback and suggestions. Please send your queries to realanswers@bridgestone.ae and we will try to cover them in our forthcoming issues. Finally, we would like to show our appreciation to Hiroshi Nakanishi, who has recently transferred to Bridgestone Germany. Mr Nakanishi was instrumental in establishing and developing Real Answers in the Middle East and Africa region and we sincerely thank him for all his efforts. I hope you ﬁnd this issue to be an enjoyable and informative read.

Yuji Fushimi General Manager – Commercial Tyre Marketing, Bridgestone Middle East & Africa FZE

real QUESTIONS real ANSWERS MARCH 2010

BRIDGESTONE

march 2010 real questions real answers

| repair selection

BRIDGESTONE

| repair selection

CHOOSING THE RIGHT REPAIR PROCEDURE What is the best way to repair a puncture? Real Answers outlines the pros and cons of the main forms of repair What should be done if a tyre is punctured by an object such as a nail? There are two options when a tyre is punctured – either discard the tyre and replace it with a new one, or get the tyre repaired and reinstalled. Isn’t it easier to replace the damaged tyre with a new one? In some cases it may be more convenient to buy a new tyre, but repairs are more economical and benefit the environment by saving resources. Repairing a damaged tyre involves fewer CO2 emissions and less crude oil consumption than the tyre manufacturing process. Furthermore, the cost of repair is far less than the price of a new tyre. Can all punctured tyres be repaired? Not all damaged tyres can be repaired – it is important that the tyre is evaluated by a skilled professional. What’s involved in the evaluation procedure? The professional needs to judge whether the location and size of the injury is repairable and they must select the proper repair materials and apply the correct procedures. They must evaluate whether there are any internal damages to the tyre, such as belt separation, that cannot be repaired.

Why is it so important that the tyre is dealt with by a professional? The main reason is safety – mistakes by unskilled staff can cause serious accidents. For instance, a tyre could burst if it is only repaired from the outside and then inflated. Tyres must be inspected on both sides, by looking, touching and, in some cases, smelling for burnt rubber. Does this mean that tyres have to be repaired from the inside? Yes but it is also necessary to prepare the injury channel or the damaged parts from the inside as well as outside. First demount the tyre from the rim and carry out the inspection procedure. Then, depending on the injury size and location, determine whether a fast repair system is sufficient or whether section repair has to be followed. If it is minor damage, like a nail hole, it should be repaired from the inside after the injury channel has been prepared. However, the tyre may also need to be repaired from the outside in the case of larger injuries or if it is damaged on the shoulder or sidewall area. Can’t you just plug one end of the injury to make it air tight? This is a common mistake – plugging the end of the injury is not a remedy. An injury weakens the tyre and it may fail eventually, unless it is fully repaired. The injury channel which penetrates the tread should be plugged, while the inside of the tyre should be supported/reinforced by a patch.

real questions real answers march 2010

BRIDGESTONE

| REPAIR SELECTION

Diagonal repair patch for bias tyres (suitable for hot or cold vulcanisation)

Sealﬁx

Special Cement BL (suitable for hot or cold vulcanisation)

IS THERE A QUICK FIX? Yes. Temporary repair, or ‘string repair’, is the easiest and quickest type of repair. But, just as its name suggests, it is a temporary measure that is intended for a quick intervention at site if a spare tyre is unavailable or there are no repair stations nearby. After applying the temporary repair unit, TIP TOP recommends that the tyre is used at a maximum speed of 80 km/h for a maximum of 100 km. WHAT ARE THE ADVANTAGES OF THIS METHOD? Temporary repairs can be carried out anywhere and can be completed in less than ﬁve minutes (therefore they are also called emergency repairs). In addition, the tyre doesn’t have to be demounted. However, this method is often wrongly used as a permanent repair – it’s vital that the tyre is properly repaired as soon as possible. WHAT ARE THE OTHER DRAWBACKS? As explained, this method is not a permanent remedy for the punctures; therefore there is a risk of total tyre failure and even tyre bursting. If the tyre fails then it is irreparable. Furthermore, the risk of tyre failure presents a hazard for the repairing mechanic and can cause a serious accident on the road, especially if the vehicle is travelling at a high speed.

MARCH 2010 real QUESTIONS real ANSWERS

Liquid buffer (suitable for hot or cold vulcanisation)

Thermopress Eco (suitable for hot vulcanisation)

WHICH TYPE OF REPAIR PROCESS OFFERS THE BEST QUALITY? Hot vulcanisation is the most sophisticated and professional repair technique. It is also suitable for repairing the tyre tread, shoulder and sidewall, and more severe damages. The hot vulcanisation process requires a temperature in excess of 95°C, in order to cure (cross link) the uncured filling rubber and create a perfect, permanent bond with the tyre. The process is suitable for much larger damages than fast repair or emergency repair systems. WHAT ARE THE BENEFITS OF HOT VULCANISATION? The process of hot vulcanisation requires a complete preparation of the damaged parts of the tyre to avoid failures in the future. Thus it allows a proper inspection and identification of the damaged parts. Rust, separations or loose wires can be easily identified and therefore removed. Another major benefit is that the filling material meets the specifications of the original tyre material. The repair personnel can also match the repair area to the original shape of the tyre. It’s worth noting that there are two types of hot vulcanisation: onestep repair and two-step repair.

BRIDGESTONE

| repair selection

MTR Rubber (suitable for hot vulcanisation)

Minicombi repair unit (suitable for cold vulcanisation)

Radial repair patches (suitable for hot or cold vulcanisation)

What is the difference between the two types of hot vulcanisation? One-step repair utilises equipment that can cure the filling material and the repair unit (patch) together. Two-step repair means that the filling material is first cured in a hot vulcanisation process and then the repair unit is subsequently cured in a cold vulcanisation process (for a minimum of 24 hours at 20°C). What are the drawbacks of hot vulcanisation? Hot vulcanisation involves investment in equipment and requires time for curing and preparation. When conducting a permanent repair, the tyre must be removed from the rim. This is because some damages cannot be detected from the outside. When is cold vulcanisation used? The majority of tyre damages are small punctures on the tread area and these can be permanently repaired using cold vulcanisation products such as REMA TIP TOP’s MINICOMBI. Cold vulcanisation products are usually only suitable for tread penetrations. In some instances bead rubber damages can also be repaired using this method. This is only possible if the bead area ply cables do not show any signs of damage, separation or rust.

What is required for cold vulcanisation? According to REMA TIP TOP, the process does not require heat yet a vulcanising time has to be considered and the ambient temperature should be a minimum of 20°C. Depending on the material of the repair unit and the ambient temperature, the vulcanisation time can be up to 24 hours. However, if the repair unit is made from rubber only (like MINICOMBI), the tyre is ready for use immediately after repair. This is because the unit vulcanises during the tyre run due to the generation of heat and pressure. What are the advantages and disadvantages of this method? It’s a quick and safe repair and no expensive equipment is required. However, it can’t be used on damages to the tyre sidewall or shoulder. Furthermore, the tyre has to be demounted from the rim as some damages cannot be detected from the outside.

Why can’t shoulder areas and sidewalls be repaired with cold vulcanisation? On the tread area, the belts provide a reinforcing support for any repairs. However, the belt edges are located in the shoulder area – this is therefore a sensitive portion of a tyre and any repairs in this location will require hot vulcanisation to prevent belt separations. Rubber plugs cannot provide the strength requested to support this particular area. The sidewall is an area which contains no reinforcing belts to support a repair through cold vulcanisation. It is also the area where most of the flexing occurs while the tyre is running. Unless hot vulcanisation is undertaken for sidewall injuries, there is high risk that the rubber will subsequently tear or rupture. Is it possible to install a repaired tyre at the front of a vehicle? You should check the regulations in your country but REMA TIP TOP does not advise against installing a repaired tyre on the front of a vehicle, as long as the repair complies with industry best practice. Real Answers would like to thank REMA TIP TOP for their support on this article. Details on how to conduct a repair using MINICOMBI are contained in the next feature.

real questions real answers march 2010

BRIDGESTONE

march 2010 real questions real answers

| minicombi repair

BRIDGESTONE

| minicombi repair

FITTING A MINICOMBI REPAIR UNIT Following the previous article on repair types, Ronny Dietsch, Area Manager for REMA TIP TOP, explains the best practice procedure for cold vulcanation using the popular MINICOMBI repair unit What is MINICOMBI? MINICOMBI, or MC for short, is a one-piece repair unit for punctures inflicted by an object on the road, such as a nail. It features a metal pilot guide for easy installation and seating. The unit’s name refers to the fact that it is a combination of a plug and a patch. What are the functions of the plug and the patch? The plug is the filler for the injury channel while the patch is the sealing unit applied to the inside of the tyre which keeps the repaired area airtight. MC units are used in conjunction with REMA TIP TOP’s Special Cement BL, and the two products ensure a virtually indestructible bond with the tyre. How does the cement work? The cement is the accelerator which starts the cross linking process once in contact with the sulphur contained on the patch bonding surface. The full vulcanisation process will occur during the running of the tyre. (For an explanation of vulcanisation, read the article on pages 4 – 7.)

Can MINICOMBI be used on any form of nail damage? It depends on the location and size of the damage. MC can only be used for tread punctures. Damages on other areas of the tyre will require the use of other products. In the case of trucks, if the area of damage is above 10mm, or the angle of the injury is above 15 degrees, then MC should not be used. Why can MINICOMBI only be used on tread punctures? The rubber plug should be contained within the belt package as it provides support to the plug. If the MC is installed in the sidewall, for instance, there is a high risk of the rubber tearing and rupturing. Why is MINICOMBI unsuitable for punctures over 10mm? The patch unit of the MC is made from rubber and doesn’t contain any supporting layers. Punctures in excess of 10mm have a negative effect on the load capacity of the tyre, and this means that the original load capacity is reduced. For punctures over 10mm we recommend that the tyre is supported with patches that contain reinforced layers in order to maintain the original load capacity.

Why is MINICOMBI not suitable if the angle of the injury is more than 15 degrees? While pulling the MC into position, if the injury-causing object entered the tyre at 15 degrees or more, there is a good chance that one side of the unit’s circular base will touch the liner first. This will lead to an unevenly seated repair unit which can trap air beneath the patch base. Furthermore, as the MC is made from rubber only, if the plug is excessively stretched in one angle/direction then this may result in a tear between the plug and the patch. Does MINICOMBI meet the required international safety standards? REMA TIP TOP standards meet all international safety and road requirements. Thorough tests in the development and testing centre ensure that the end user is using always the best possible quality.

real questions real answers march 2010

BRIDGESTONE

| MINICOMBI REPAIR

HOW TO FIT A MINICOMBI UNIT IN 10 STEPS

Not repairable

STEP 1 DETERMINING THE SUITABILITY OF MINICOMBI Demount the tyre, remove the external object and use a piece of chalk to mark the area of damage with cross marks (on the outside of the tyre). Next, use an awl (tyre probe) to probe for unseen internal damage and determine the direction of the puncture channel. You should also check that the tyre is in a ﬁt state to be repaired – check the level of wear on the tread and the general state of the tyre. You must also ensure that there is no damage to the tyre in other locations. MC is only suitable if there is no evidence of separation between the tread components, such as belts or belt and casing (body ply) etc. Measure the size of the puncture inside and outside the tyre. If the damaged area is 10mm or less, and the angle of the puncture is less than 15 degrees, then the puncture can be repaired with MINICOMBI unit.

Section repair required

MINICOMBI

STEP 2 CHOOSING THE CORRECT MINICOMBI SIZE If the damage can be repaired with MC, choose the proper repair kit by using the following chart.

Repairable area in

of the tread width

Maximum damage size

Minicombi

3 mm 4.5 mm 6 mm 8 mm 10 mm

A3 A4, 5 A6 B8 B10

MARCH 2010 real QUESTIONS real ANSWERS

80%

70%

BRIDGESTONE

| minicombi repair

Step 3 Preparing the damaged area (cleaning) Start by preparing the tyre’s inner surface (i.e. not the tread side). Spray the area around the damage with liquid buffer. Make sure that the surface is thoroughly wet and that the spray covers an area about twice as large as the MC unit base. Allow the spray to stand for a few seconds but do not allow it to completely evaporate. While the sprayed area is still wet, use a scraper to scrape an area larger than the base of your chosen MC unit. Next, use a vacuum to thoroughly clean the area. Use chalk or a rubber pen to mark the damage with cross marks on the inside of the tyre. What is the purpose of the liquid buffer? The liquid buffer is not really a buffer in the conventional sense – it’s a chemical solvent which helps to remove all silicone, graphite or other mould lubricants which have a negative effect on the bonding of the repair unit. Scraping the sprayed area will remove lubricant residues more efficiently. Why should the sprayed/scraped area be larger than the repair unit base? As the patch is made from rubber, it will always be stretched slightly during the stitching process. In addition, during the mechanical buffing process (step 6), the buffing tool may come into contact with the area surrounding the mark. If this area is not clean then mould lubricants may be transmitted to the buffing area.

Step 4 Clearing the puncture channel Select the appropriate cutter according to the size of the damage (see chart). We recommend using a carbide mill cutter, as supplied in the MC pack. Note that safety goggles should always be worn when working with buffing/cutting tools

Size

MINICOMBI Unit

3mm 1/8" 4.5mm 3/16" 6mm 1/4" 8mm 5/16" 10mm 3/8"

A3 A4,5 A6 B8 B10

Carbide Cutter

595 4900 595 5019 595 4962 595 4948 595 5060

Use a pneumatic buffer or an electric drill (max 2000-3000 rpm) to even out the damage from the inner wall of the tyre, observing the direction of the puncture channel. It’s important that the incision is circular, rather than square, in order to prevent the injury from spreading. Next, insert the mill cutter all the way through the puncture from the inside then fully remove the cutter to clear the debris. Now use the same cutter to even-out the puncture from the other side of the tyre (the tread side). Repeat this step two or three times. Remove any material which may be detrimental to the body (such as rust). Why should a mill cutter be used? A mill cutter is able to cut or mill away the destroyed wires inside the injury channel; essentially it cleans the channel. The cleaner the channel, the easier it is to insert the MC unit. Why should the injury be drilled from the inside and then the outside? It is recommended to drill from the inside first. This procedure will help to prevent any damage to the body ply cable from being extended or drilled twice.

real questions real answers march 2010

BRIDGESTONE

Step 5 Mechanical buffing On the inside of the tyre, draw an outline the size of the MC unit base, with the puncture in the centre. Add cross marks. Use a pneumatic buffer/electric drill – and an appropriate contour wheel or a wire brush – to buff the marked area. Work from the centre to the outside and buff just until the surface has a smooth, uniform texture. Buff the entire outlined area but avoid over-buffing or gouging. Next, clean any rubber dust left from the buffing process, first with a brass cleaning brush and then a vacuum cleaner.

| minicombi repair

One of the previous steps involved the use of liquid buffer. Why is it now necessary to mechanically buff the liner? The liquid buffer is used as a cleaner only, and the cleaning process should be finished before buffing. The mechanical buffing process creates a texturised area to allow greater adhesion between the patch and the tyre. Should liquid be used to clean the area after buffing? No. It is important not to apply liquid buffer to the surface area that has already been buffed. Remove any buffing dust/dirt without using any liquid; for example, use a brass cleaning brush and a vacuum cleaner.

Step 6 Applying cement to the buffed area It’s now time to apply Special Cement BL to the buffed area inside the marks. How should the cement be applied? Spread the cement evenly and thoroughly then allow it to dry naturally until it is slightly tacky. Do not use blow driers, heat lamps or compressed air. How long should you wait for the cement to dry? We recommend waiting for ten minutes to allow the solvents – which keep the solution flowing – to evaporate. If the tyre is positioned so that the puncture is at three or nine o’clock then this will aid drying.

march 2010 real questions real answers

Step 7 Applying cement to the puncture channel Position the tyre so that the puncture is at roughly seven or eight o’clock (the tyre must be upright, not flat on the ground). On the inside of the tyre, place the tip of a tube of cement at the mouth of the puncture channel, and squeeze cement into the puncture until it is completely filled. Do not lubricate the already coated inner tyre or the MINICOMBI stem.

BRIDGESTONE

| minicombi repair

Step 8 Inserting the MINICOMBI unit Before the Special Cement BL dries in the puncture channel, insert the MC repair unit through the puncture from the inside of the tyre until the metal pilot comes all the way through the tread side. On the tread side, grip the MC unit firmly with pliers, and pull it straight through the puncture as far as possible. Take hold of the MC stem and pull it until the unit’s base is flush with the buffed and cemented tyre inside. Why should the cement that has been filled in the puncture channel remain wet? It’s a lot easier to insert the MC unit into the injury channel if the cement has not dried. It’s also less likely for a stem breakage to occur. It should be noted that cement must never be applied to the plug or stem of the MC. This is because most of the solution will flow down to the patch and could create a separation between the patch and the buffed area.

Step10 Final touches & remounting The finished repair should show no peeling or lifting at the edges and should neatly cover the area of damage. It’s now time to mount the tyre and inflate it to the correct operating pressure. Using a skiving knife, trim off the excess MINICOMBI stem on the tread side of the tyre, to bring it level with the tread surface without stretching it. The tyre can be returned to service immediately.

Step 9 Securing the unit The unit needs to be stitched then sealed. Use a thin stitcher to stitch the base of the repair unit to the prepared area. Stitch from the centre outwards and go over the entire MC unit base to force out any trapped air. After you have finished stitching the centre, be sure to stitch all the way around the edge of the repair unit. After stitching, apply a generous coating of Innerliner Sealer to the edge of the repair unit base and to the buffed area around it. What is the purpose of the Innerliner Sealer? The Innerliner Sealer is used to cover and seal the edges of the MC patch to avoid potential air penetration. Furthermore, the coat is used to seal any additional buffed area against oxidation, which could occur if the buffed rubber is left exposed to air.

For more information on MINICOMBI and other REMA TIP TOP products, go to www.rema-tiptop.com

real questions real answers march 2010

BRIDGESTONE

| Maintenance

PERFECTING PIT WORK Detaching and reinstalling a wheel is a routine task for many fleets, but an incorrect procedure can cause damage and increase the risk of an accident. Real Answers outlines the best practice guidelines for pit work

march 2010 real questions real answers

BRIDGESTONE

| MAINTENANCE

WHEN DETACHING A WHEEL, WHAT IS THE BEST WAY TO ‘JACK UP’ A TRUCK? A truck, of course, is an extremely heavy object, and lifting it with a jack can lead to a serious accident if the correct procedure is not followed. First of all, the hand brake must be on and the engine switched off. Stoppers should be set on the tyres that are not being jacked up (1). SHOULD THE JACK BE LOCATED IN A SPECIFIC PLACE? Yes, it is important to check the vehicle’s manual and place the jack at the speciﬁc position. Generally speaking, the jack should be placed around the area where the axle and leaf spring meet (2). It should be noted that some vehicles have recessed areas near the jack-up point – if the jack is placed here then the vehicle may slip off (3). Avoid jacking up around areas such as the differential gear box and radius rod as this may cause damages to certain makes and models of vehicles (4). It is extremely important not to jack up the front end of the vehicle with the jack placed in the centre of the front axle as it may cause the vehicle to fall over on its side (5).

WHAT HAPPENS IF YOU HAVE TO JACK UP BOTH SIDES OF THE VEHICLE? If you need to jack up both sides of the vehicle (e.g. when rotating tyres) place the jacks at the set points for both the left and right side wheels (6). WHAT SHOULD BE DONE IF THE JACK DOES NOT FIT UNDER THE JACKING POINT? Sometimes when a low-platform four-axle vehicle has a puncture, it is not possible for the jack to go under the jacking point (7). In such a scenario, place a jack in the jacking point for the opposite tyre, followed by another jack in the centre of the axle. Finally, place a third jack in the set jacking point for the punctured tyre (8). WHAT IS THE CORRECT PROCEDURE BEFORE DETACHING A WHEEL? First of all, check that all the nuts and bolts are present. Look for any rusty liquid coming out from the wheel, bolts or nuts, and then check if there are any loose nuts or cracks in the wheels. Check the length that each bolt protrudes from the nuts (9). If there are any differences then the bolt holes or hub could be worn, or the bolts or bolt threads could be damaged.

real QUESTIONS real ANSWERS MARCH 2010

BRIDGESTONE

THE NUTS ARE NOT UNIFORM – DOES THIS MATTER? Yes. Be careful not to mix different types of nuts, or use steel nuts on aluminum wheels or aluminium nuts on steel wheels. This practice is dangerous as the nuts will not be tight enough and the bolts can become damaged. IS THERE A WAY TO CHECK WHETHER THE NUTS ARE LOOSE OR DAMAGED? Put your finger under the outer nuts and tap the top surface with a hammer (10). If one or more of the nuts makes a vibration or sound that is different to the others, there is a possibility that the nuts are loose or the bolts may be broken. If necessary, the nuts should be replaced and rechecked. If the problem persists, the bolts should be changed. THE NUTS ARE ALL FINE. WHAT IS THE NEXT STEP? The tyre should now be detached from the vehicle. To do so, first loosen the nuts with an impact wrench (11) but finish loosening by hand, in order to avoid damaging the threads of the bolts and the inner side of the outer nuts. Care is required throughout – if the tyres are detached in a rough manner, the bolt holes of the wheel and the bolt will come into contact and may become damaged.

| MAINTENANCE

WHAT NEEDS TO BE DONE ONCE THE TYRE HAS BEEN DETACHED? The surface of the hub that comes in contact with the wheel must be clean and free from dirt or rust (12). This is an important safety consideration – if the hub does not adhere to the wheel disc properly then the bolts can break and the wheel may drop off. HOW SHOULD THE HUB BE CLEANED? A wire brush should be used to remove the rust and dirt from the hub. At the same time, the hub needs to be checked for any damage or wear – a broken hub will need to be changed. The bolts and the nuts should also be checked while cleaning (13), and any rust or dirt must be removed with a wire brush. If there is any damage to the threads or extended bolts then this may signal broken bolts. Check whether there is damage or wear to the inner threads of the nuts. Also inspect the surface of the nut 14 which comes into contact with the wheel surface. Nuts with a rough contact surface will become loose and need to be changed (14).

DO THE WHEELS NEED TO BE CHECKED AND CLEANED? 15

Welded part

Of course. Check if there are any cracks on wheel holes and other areas. If a wheel has welded parts (15) check for any damage. Dirt on the surface of the wheel disk that attaches to the hub will cause looseness, so the surface of the wheel needs to be cleaned. Make sure that the thickness of the wheel holes that attach to the nuts are not less than 2mm (or 4mm for aluminium wheels) (16). This scenario may lead to a loosening of the bolts and therefore the wheels will need to be changed. It should be noted that some wheels, particularly second-hand ones, are heavily painted to match the body colour. Too much paint will result in looseness, so only install the tyre after removing the paint from the contact surface of the wheels with the nuts. 16

WHAT IS THE NEXT STEP? The tyre should be inflated. Caution is required, irrespective of whether the tyre is new or already in service, and the use of a tyre cage is always a must. You should be extremely careful when inflating a tyre that has been in service, as internal tyre damage – caused by punctures, run flats or other factors – could result in the tyre exploding. Furthermore, internal damages may not be clearly visible from the outside of a tyre.

MARCH 2010 real QUESTIONS real ANSWERS

BRIDGESTONE

| Maintenance

18 25 22

when is it safe to inflate a tyre That has been in service? The first and foremost step is to check with the driver – if the tyre was driven for a long period with a puncture, or driven at zero pressure, then it should not be inflated. When inspecting the tyre, start with a visual check of the sidewall and the inside of the tyre. If you find any wrinkles or cracks on the inner surface, there is a possibility that the tyre has been run flat. Always check the inside on both sides thoroughly under adequate lighting. Always check the bead areas even if they are not punctured (17). If there are ring marks by the wheel, or wheel encroachment is severe, there is a possibility that the tyre has been used with low inflation pressure. In such a case, use extra caution when inflating the tyre. I can’t see any of these problems. Is it fine to inflate the tyre? Even if you can’t find any abnormalities by sight, it is very important to run your hand along the sidewall and the inside of the tyre (18). If you feel waviness or an unusually soft section, or hear a creaking sound, then the tyre may be flat and must not be inflated. What is the correct method of inflating a repaired tyre? Take the utmost care when inflating a punctured tyre that has been repaired. If you hear a creaking noise while filling the tyre, stop the procedure immediately as it indicates signs that lead to an explosion.

The tyre has been inflated. How should it be prepared for installation? After inflation in a safety cage (19), the tyre should be put onto a wheel balancer (20). This will adjust any imbalance between the two sides, which can cause vibration. Next, the nuts and bolts should be lubricated (21). Be careful not to get any oil on other parts of the wheel apart from the nuts and bolts. A convenient way to evenly lubricate the contact surface of the nuts is by pressing the nuts with an oil-soaked sponge (22). Do not use oil and grease containing molybdenum disulfide, as it may cause overtightening which will damage the bolts. Tighten the nuts as far as possible by hand (23). If the new nuts don’t screw in smoothly then this is a sign of damaged bolts. Now temporarily tighten the nuts to around 100 Nm using an impact wrench. Is there a specific order in which to temporarily tighten the nuts? Yes, the nuts should be tightened in diagonal order. If there are 10 holes then the nuts should be tightened in the following order shown below, left. However, if there are eight holes then they should be tightened in the order shown below, right.

What happens after the nuts have been temporarily tightened? The nuts require further tightening, two or three times, after the vehicle has been lowered from the jack. As with the temporary tightening, further tightening must be done in diagonal order. Is any more tightening required? Yes, there is a final stage of tightening. First, set the torque valve to the level specified by the vehicle manufacturer (24). The final tightening must be done in diagonal order (25). After tightening the last nut, check if the first nut is still tightened to the set torque value. If you use the preset tyre torque wrench, hold the handle in the designated area and slowly pull down on the bolt. When you hear the snap of the signal sound, the tightening is complete. Is it a good idea to make a record of all the work that has been carried out? Absolutely. It is best practice to write a report on all the pit work and to keep this on record so that it is clear what was done and when. It is also important to clean around the area that was used for the work. The machinery should be well maintained to be ready for the next job. Will any further work be required? The nuts may loosen after they adjust to the surface of the wheels. Therefore, it is necessary to retighten the nuts after a certain amount of time or mileage.

real questions real answers march 2010

BRIDGESTONE

| MATCHING DUAL TYRES

MISMATCH SPELLS TROUBLE It is important that the two tyres in a dual assembly have matching attributes. Any mismatches can cause severe problems, such as rapid and irregular wear, and even tyre failure

MARCH 2010 2010 real real QUESTIONS QUESTIONS real real ANSWERS ANSWERS

BRIDGESTONE

| MATCHING DUAL TYRES

MARCH 2010 2010 real real QUESTIONS QUESTIONS real real ANSWERS ANSWERS

BRIDGESTONE

| MATCHING DUAL TYRES

OVERALL DIAMETER

WHAT IS A DUAL ASSEMBLY? A dual assembly is when two tyres are mounted together. In such a set-up it's crucial that the two tyres have the same diameter.

WHAT IS THE DIAMETER OF A TYRE? A tyre’s diameter – also referred to as the overall diameter – is the distance from one tread surface to the other. The diameter is measured while the tyre is inﬂated but not loaded.

HOW IS IT POSSIBLE TO HAVE MISMATCHED DIAMETERS? Mismatching can occur if one of the tyres has a higher inﬂation pressure, or if one tyre is more worn and has a shallower tread depth. It is also important that the tyres are the same size, are made by the same manufacturer and contain the same pattern. A use of different products could result in mismatched diameters even if the tread depth and air pressure levels are the same.

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| MATCHING DUAL TYRES

OVERALL DIAMETER

WHAT IS A DUAL ASSEMBLY? A dual assembly is when two tyres are mounted together. In such a set-up it's crucial that the two tyres have the same diameter.

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BRIDGESTONE

| MATCHING DUAL TYRES

WHAT HAPPENS IF THERE IS A MISMATCH IN DIAMETER? It depends on the level of the mismatch. As dual tyres are bolted together, when one makes a revolution the other must also make a revolution. If the circumference of one tyre is smaller, its tread is dragged against the road surface. In a test, a ﬁve psi mismatch in inﬂation pressure resulted in around

WHAT HAPPENS TO THE TYRE THAT IS BEING DRAGGED? The dragging will create some seriously rapid wear and severe irregular wear. Of course, rapid wear on the smaller tyre then makes the mismatch worse, because now the tyres will be mismatched in both pressure and tread depth. Plus, once irregular wear gets a foothold it tends to continue, even if the inﬂation pressure is corrected. IS THE LARGER TYRE AFFECTED? Just as the larger tyre tends to drag the other, the smaller tyre exerts a slight braking force on the larger one, which can increase the rate of wear. Of course, the difference in load will increase as the difference in diameter becomes greater. And if the overloading on the larger tyre exceeds a certain level, the tyre will suffer internal damage, even if it seems to be unaffected externally.

DRAG

BRAKE

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8mm difference in tyre circumference. This may seem small but if you consider that in operation a tyre can make 310 revolutions in one kilometre, after 100,000 kilometres a tyre will experience 31 million times worth of 8mm drags. It is as though the smaller tyre is dragged, not rolled, at highway speed for 248 kilometres.

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WHAT KIND OF INTERNAL DAMAGE CAN OCCUR? Running overloaded causes massive heat build-up in tyres and this leads to all sorts of problems. For example, the belts can actually detach from each other which may not be visible at ﬁrst, but the result is a ruined tyre that cannot even be retreaded.

SO DOES THAT MEAN THAT DUAL TYRES MUST BE EXACTLY THE SAME DIAMETER? It may not be possible to match the diameters exactly. Accordingly, there is a small degree of tolerance.

| MATCHING DUAL TYRES

WHAT HAPPENS IF THE DIAMETERS ARE WITHIN THE TOLERANCE LIMIT BUT THE TYRE BRANDS/PATTERNS ARE DIFFERENT? If the tyres are different brands/patterns then the load/deﬂection characteristics may be different and this will result in one tyre carrying more load than the other. This overloading can lead to internal tyre damage, as explained earlier. Different patterns also have different handling characteristics and a mix could impair safety.

WHAT HAPPENS IF ONE OF THE TYRES BECOMES ‘FLAT’? If one tyre becomes flat then it can suffer from multiple problems. Yet in addition, the non-flat tyre may be so overloaded that it too will suffer internal damage that can cause it to fail catastrophically at a later date. WHAT SHOULD BE DONE IF A FLAT OCCURS? If a driver experiences a flat in a dual pair, the best strategy is to pull off the road at once and immediately call for help. However, this may not always be possible. In an extreme case – if the driver must continue to a dealer or truck stop, at the risk of tyre failure – they should note the mileage when the flat occurred and when the tyre is fixed. Following this, a skilled tyre technician should carefully examine both tyres – inside and out – to make sure they are fit for continued service.

MOVING AWAY FROM MISMATCH, WHAT ELSE HAPPENS IF DUAL TYRES HAVE LOW INFLATION PRESSURE? Low inﬂation pressure on one or both of the tyres can cause the sidewalls to touch and rub against each other, which is termed ‘dual touching/kissing’. This causes excessive tension and compression and can result in tyre failure due to a break-up of the tyres’ ply cords. Other causes for dual kissing are incorrect rim use, overloading or the road conditions. WHY DO DUALS HAVE LOWER LOAD LIMITS THAN SINGLES?

IN SUMMARY, WHAT ARE THE MOST IMPORTANT THINGS TO REMEMBER WHEN IT COMES TO DUAL TYRES? The key is to match the tyres as closely as possible – this includes the size, manufacturer, pattern, construction, tread depth and inﬂation pressure.

TOLERANCE LIMIT SECTION WIDTH RADIAL BIAS >=9.00 INCH (255MM) <=8MM <=12MM <=8.25 INCH(245MM) <=6MM <=8MM

For a radial tyre size of 9.00 inches or more, if one tyre in a dual assembly has an overall diameter of 1,050mm then the second tyre can have a tolerance limit of anywhere between 1,042mm and 1,058mm.

According to JATMA* standard guidelines, a minimum spacing between duals has to be maintained under standard loading conditions, primarily to avoid dual kissing. However, different operating conditions can lead to a shift in load between the tyres; for instance, the road crown can put more load on one tyre than the other. Therefore, dual tyres have slightly lower load limits than single tyres, to compensate for small differences in tyre loading which could cause dual kissing.

* Japan Automobile Tyre Manufacturers Association (JATMA) – Standards of Selection Usage & Maintenance – Truck & Bus tyres

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| transporting f1 tyres

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| transporting f1 tyres

Burning rubber Although not the most high profile aspect of Formula One, the transportation of racing car tyres involves a great deal of planning and expertise. James Sullivan, truck driver and technician for Bridgestone Motorsport, outlines the many challenges of his job What is your role within the Bridgestone Motorsport team? Iâ&#x20AC;&#x2122;m an LGV 1 driver and tyre technician for Bridgestone Motorsport in its Formula One/GP2 programme. Iâ&#x20AC;&#x2122;ve held the position since February 2008. What does your job involve? Bridgestone Motorsport has 13 articulated (38 tonne) and three 7.5 tonne trucks, all Mercedes Actros. I am responsible for driving one of these trucks to the tests and races, cleaning the trucks on arrival at the circuit and helping to set up the tyre fitting equipment. At the tests and races themselves, I help to coordinate and check tyre distribution and I inflate and balance the Bridgestone Potenza race tyres. During the sessions I work in a team

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| transporting f1 tyres

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pit garage taking tyre temperatures and pressure and assisting the Bridgestone tyre engineer. At the end of the test or race I help to remove the tyres from the rims and pack down all of the equipment. What are the main challenges associated with your job? Driving the vehicle for Bridgestone Motorsport is different to driving a vehicle for other logistics or delivery companies. Firstly, most of the driving we undertake is in Europe; therefore we need to consider the driving laws in a range of countries. Throughout the F1 season there may be back-to-back races, therefore we need to pack down the equipment on a Sunday night and ensure the trucks are at the next circuit by the following evening. Most importantly, if we do not arrive on time then the Formula One drivers will not have tyres to race on. On some occasions we will use two drivers for a journey, taking it in turns to drive the truck. This will generally happen for long or complicated journeys such as the three to four-day drive from our UK

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base to Hungary. Although we need to make a quick turnaround to arrive at the circuit on time we must stick to speed limits and follow all of the necessary driving laws. Apart from speed limits, what other driving laws apply? In Europe the maximum we are legally allowed to drive is 4.5 hours followed by a 45 minute break, then an additional 4.5 hours and a 45 minute break, with one extra hourâ&#x20AC;&#x2122;s driving time allowed if required. We are only allowed to drive this shift pattern twice in one week, due to the European tachograph laws. When driving the trucks we will always stick to the national speed limits and the vehicles are limited to 90 kilometres per hour. Are drivers required to do anything before a journey? Before each journey the Bridgestone Motorsport truck drivers are required to carry out detailed and thorough checks on their vehicles. This includes checking the indicators, lights, tyre pressure, etc. Throughout the journey and during

breaks we will also carry out checks on the vehicle to ensure everything is still in working order. We follow all road traffic laws including our legal break requirements and will wear a seatbelt at all times. How are the trucks transported from the UK to mainland Europe? The trucks go via either the Channel Tunnel or a ferry to mainland Europe, and we follow set routes to each circuit. The journeys are planned ahead of departure, which gives us plenty of time to get to a hotel should we require an overnight stop. Do you have any advice for other truck drivers? My advice to any truck driver would be to always ensure your vehicle is fit for use on the road and always check your tyre pressure. Tyres that are maintained at the correct air pressure will last many more miles before they have to be replaced or retreaded. In addition, correctly inflated tyres are less likely to become damaged and fail on the road â&#x20AC;&#x201C; this is a vital safety consideration.

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