1984 RT front brake problem

jgr451

Active member

• Jul 24, 2003

• #1

I have a 1984 R100RT ,great bike.It has double Brembo disc brakes up front.This year it acquired the nasty habit of having the calipers seize to the rotors.I rebuilt the master cylinder but it did it again.Any ideas?

 

jgr451

Active member

• Jul 24, 2003

• #2

oops, BRAKE problem.I am a dummy.

 

kbasa

Well-known member

• Jul 24, 2003

• #3

Do you have rust and crud on the pistons on the calipers?

 

jgr451

Active member

• Jul 24, 2003

• #4

The mechanic told me there was a slight corrosion in the bore of the master cylinder when he replaced the piston and the rubber,which he honed out.He didn't say about the bores in the calipers;worth a look.I have focussed on the master cylinder because both brakes seized,not just one,and I thought it too coincidental that both sides would give the same problem at the same time.Thanks for the thought.

 

lkchris

Active member

• Jul 25, 2003

• #5

Seems a little difficult to determine both brakes are seized at once without careful visual inspection, but nevertheless if your bike has been exposed to conditions that will create corrosion in the master cylinder, the same conditions were present to affect the calipers as well.

You'll find hardly anyone that recommends rebuilding a master cylinder and new ones are relatively inexpensive. Calipers are probably another matter.

 

jgr451

Active member

• Jul 25, 2003

• #6

Hi Kent,thanks for your reply.First time it happened I knew it was both sides because both rotors were smoking and blue!!The second time, I noticed the onset as the lever got stiff, so I stopped before the seizure was complete.
I have been afraid to ask for the price of a new or used master cylinder,and anyway,I am not sure that is the problem yet.I asked the mechanic whether the bores in the calipers could be the problem.He saud no,or the brake fluid would not have released from the bleeder.
It seems to me there is a logic here that is escaping me.I feel like I should be able to figure out the problem!!

 

LORAZEPAM

leave my monkey alone

• Jul 25, 2003

• #7

Even if the caliper siezed you could still get fluid from the bleeder. I think that the mechanic had better think that one over. I once had a sticking caliper on my cage, and the culprit was a bubble inside the brake hose that attached to it, maybe a set of brake hoses will help. Just a thought..

 

LORAZEPAM

leave my monkey alone

• Jul 25, 2003

• #8

this was a bubble in the lining, not an air bubble, It kept the fluid from traveling back to the master cylinder after the brake pedal was released. I switched the caliper first, and should have tried the cheaper hose before I did that.

 

jgr451

Active member

• Jul 25, 2003

• #9

Hi Lorazepam(great handle by the way).The mechanic suggested there might be a problem with the brake hose.How would a guy find out whether it is master cylinder,brake hose or caliper?Short of changing everything out,one piece at a time.Plus there are 3 fron brake hoses...

Thanks for your advice,I appreciate it.

 

LORAZEPAM

leave my monkey alone

• Jul 28, 2003

• #10

I would say if both calipers are sticking, then the hose leading from the master cycinder to the manifold is the culprit, if it is just one caliper sticking, I would try that hose first.

 

jgr451

Active member

• Jul 28, 2003

• #11

Kay thanks Lorazepam!!