Dec-09 brret ds
RETRO-FITTING OF Mk3 BRAKE SETS TO A Mk2 BROMPTON. This kit is for use only with M-type handlebars (formerly Brompton L-type or T-type): the cables are not suitable for use with a P-type or S-type. If Mk3 Brompton calipers are used, then Mk3 levers must also be fitted, which in turn require the use of Mk 3 cables. NOTE, in January 2004 we introduced a new Brompton frame with the wheel base increased from 1015mm (swb) to 1045mm (lwb), the most obvious difference being that the main hinge on a lwb bike is cast iron rather than forged steel: if two rear cable outers are supplied, use the shorter one for a swb bike, and the longer one (packed separately) for a lwb bike (if in doubt, use the longer cable). Fitting the brakes is straightforward, but when removing the old rear caliper, it's best to leave the Lower stop disc, LSD, attached to the rear brake nut, RBNUT. when exchanging the lever, you can usually avoid removing the handlebar grip by leaving in place and re-using the original clip band: it should fit the new lever housing. replace washers in the same position in each stack. Note however that an extra one or two washers may be required at the rear if you are retaining the mk 2 lower stop disc (LSD): the reason is that the spindle is slightly longer on some of the Mk 3 brakes, and the screw retaining the lower stop disc may "bottom" against the end of the caliper spindle inside the RBNUT before this RBNUT is tight. Insert one extra washer next to W1, and if a second is needed, put it next to W2. the cables must be routed as described below. the outer part of the front cable is in two parts: the shorter part must lie between lever and cable gatherer, CABGATH, and the longer part below: the metal ferrules should respectively enter the lever and the caliper. Check the fit of the new cable-outers (the ends without the ferrule) in the existing CABGATH: they should bottom cleanly in the sockets. If they are a tight fit, replace the old CABGATH with the new one provided (which means disconnecting the hubgear cable). after fitting the new rear brake, the lower stop disc has to be reset (maybe unnecessary if you have a Mk3 lower stop disc). See next sheet. for each caliper, a rubber boot and its adaptor should be fitted over the cable, where it runs between the two caliper arms. For a dual-pivot caliper, there is a cutaway at C, this to clear the surface B on the lower brake arm (no cutaway is needed for the "high-leverage" caliper, normally fitted at the rear).
subtext cable routing
Correct routing of the control cables is essential if these are not to be damaged during folding. All cables MUST pass in front of the handlebar, to the left of the handlebar stem and to the right of the main frame tube. The front brake cable must pass: a) through the body of the cable gatherer, CABGATH (outer cable in two parts) b) through the forward cable guide, CGF, and c) to the left of the front mudguard (for a C-type, see note below). The rear cable(s) must pass: a) through the ring on the cable gatherer, CABGATH, b) through the centre cable guide, CGC, c) inside the tube TT, d) through the rear cable guide, CGR, as shown, and e) for the brake cable, BRCABR, inside the tube SS
fig CR1
CABGATH CGF
The gear cable(s) GCAB should lie below the brake cable, BRCABR. If there are two gear cables, then the derailleur cable should lie below the hub-gear cable. When replacing the front brake cable outers, leave the CABGATH on the rear cable(s), and then feed the new outers (shorter part on top) onto the CABGATH. When replacing a cable to which a dynamo wiring loom is attached, cut the tie wraps holding the loom to the old cable, and re-tie the loom (at the same spots as before) to the new cable: on a rear cable the rearmost tie must lie just aft of the CGC, not in front of it. (If the loom is a Mk 2 type, which reverses inside a rubber sleeve just under the CABGATH, use two tiewraps here, and pull them extra tight to prevent slipping.)
BRCABR SS
GCAB TT
CGC
CGR
Note re bikes without mudguards: the LH front fork will either have a fender disc or a brazed-on wire loop: the brake cable must pass outside these (and not through the loop). Dual-pivot calipers, CENTERING. These calipers are not self balancing, and need to be trimmed so as not to exert side force on the rim. Apply the brake and watch for any trace of sideways motion of the rim or tyre as the pads engage: adjust the M5 set-screw (visible on top of the caliper - use a 2.5mm hex key) in order to get the caliper properly balanced. (If after doing this, the caliper appears "lop-sided", with one arm lower relative the rim than the other, then the whole caliper assembly needs to be re-positioned in the frame: slacken off the main nut (10 AF) which holds the brake spindle, adjust the M5 set-screw to get rid of the uneven look of the brake, and do up the main nut again while pulling on the brake lever. Finally, re-trim the brake to centre it using the M5 set-screw.) Dual-pivot calipers, PAD POSITION. As these wear down, or after any adjustment as above, the pads may no longer bear centrally against the braking surface on the rim: re-position as needed.
subtext lsdadj
The Lower Stop Disc, its role in the folding process: when you pick up the folded bike, the rear wheel cannot unfold because the lower stop disc, LSD, butts against the "folded" seat pillar, SP. The LSD can be adjusted to obtain the correct gap between itself and the SP: if the gap is too small, then the SP may foul, irritatingly, against the LSD during folding: if the gap is too large, then the rear wheel will drop away too far when the bike is picked up, so that the hook retaining the front wheel slips off the chainstay tube (CHS) on the rear frame. On bikes shipped from our factory before March 2000 (Mk 2 bikes), the lower stop disc is an eccentric, and calls for a different approach from those fitted on later Mk3 bikes. Setting the Mk3 Lower Stop (fig LS1) The lock-nut should be slackened off. Fold the bike completely, and spin the LSD along the thread to give the correct gap of 1-2mm. Finally, using 2 spanners, 19 AF and 15 AF, tighten the lock-nut: do not overtighten, correct torque 8NM. fig LS1
Setting the Mk2 Lower Stop (figs LS11 & LS13) The rear brake nut, RBNUT, must be well tightened, torque 14NM: if it is not secure, the brake caliper may move off centre when fitting the lower stop disc, LSD, to it, and the RBNUT (together with the LSD) may come loose in use. To set the lower stop correctly, partially slacken off the retaining screw so that the LSD is not loose, but can be moved by hand: fold the bike completely, and move the LSD to give the correct gap of 2-3mm. The LSD should be disposed to lie towards the LH side of the bike (fig LS13), not towards the right. Finally, re-tighten the retaining screw firmly. fig LS11
fig LS13