Hi just failed mot on back brake would not lock up wheel,checked caliper pistons move freely,bleed under side panel front caliper and rear caliper no air in system ,can lock front with back brake but not rear ,gonna fit new innards in rear slave cylinder anyone else had this prÃ³b thanks gonk2014-03-20 14:11:38
If the MOT place wasn’t used to Guzzis, it may have overlooked the different rules that apply to linked brakes; I gather that has been the reason for some MOT failures in the past.
Yep did say that they were linked ,but it locks the font left ,was wondering if the rear is meant to have less pressure or i have a problem gonk2014-03-20 15:10:10
common reading they have to add the front left to the rear to get full braking power its is correct that the rear will not lock
Thats what i thought ,problem is the new mot will only give you a percentage to reach ,my rear only feta to 14 % which is a fail as it needs to reach 25%,just strange ican lock the front left ,so as i say,i will rebuild master cylinder as if you pull the little bar out then stock yourlittle pinky up there you get a wet circle on your finger so it must have a tiny leak,but heh we have been standing on the brake
There is I believe a proportioning valve in the back brake line, which is intended to prevent the back wheel from locking. There certainly was on the Cali III.I am fairly certain the wheel does not have to lock to pass the MOT, the braking systems must be better than 25% and 30% efficient.One system is operated by the handlebar lever, the other by the brake pedal which of course operates on the front left and rear disc. The MOT place should add both together to get the final reading. Just measuring the rear is not enough. When I had this problem with an MOT I contacted VOSA and they were very interested to know which MOT station had done the test. However 14% does seem low. Maybe the proportioning valve is crudded up, or the rear calliper partially seized. If you can lock the front LH disc there is nothing wrong with the foot master cylinder. You can look at the motorcycle MOT regs here. Note there are several ways to test the brakes. These problems only arise when using the roller method. Using the gradient or floor methods, both brakes would automatically be taken into account on the linked system.
Brian UK2014-03-20 23:36:36
I think it only came in a 14% because it was weighed on bathroom scales total weight with sidecar came to 385kg,ter when i weighed it at sand yard on truck weigh bridge it was 310kg but try to explain that to a mot tester who only realy deals in sport bikes
As I understand it, the brake compensator on the back brake should limit the efficiency to around 25% on a solo model. Add the weight of a chair, and that efficiency figure must go down.
Thats the conclusion i got when you weigh back axel comes in at 180kg ,so vosa computer say no bugger gonk2014-03-21 12:40:01