front brake imbalance

[lancialulu]

Bad news - my 1.3S failed its MOT yesterday on front brake imbalance! (by 30%). You dont notice it driving except ther is a slight pull to the left (similar to the effect of camber) on moderate braking.

Very odd as I had rebuilt the calipers 5 years ago. It passed with flying colours since then with actually the o/s being the stronger side (marginally). Any way the offending weak caliper (o/s) pushed out all pistons equally so not sure what the problem is (ie no stuck piston). Can also vouch that there is no air in the system.

Anyone had similar situation??

I guess I am looking to rebuild the offending caliper.

Tim

I can only think the the o/s piston seals have swelled up for no good reason and are resisting the hydraulice pressure more than the other caliper, albeit on hard braking this is not apparent. 

[chugga boom]

have you thought about the 2 flexi pipes to the caliper?, maybe 1 has collapsed restricting the flow of fluid or i have seen them swell up like a balloon under pressure again loosing pressure to the actual brake, has the car got rusty disks?? this to can affect the brake ballance if there is rust on either the pad or disk area, thats all i can think of thats fairly obvious, good luck and let us know the outcome james

[lancialulu]

James

Thanks for this. Both discs are original so have equal amount of pitting but not really worn or rusty. When I recommissioned the car some 6 years ago I replaced the hoses so I cannot see if this will be the problem - yes the 30 year old ones were a bit soft....

I have just been given the thought in re plumbing these I might have swopped the large caliper feed for the small on the rhs so will check tonight.

Tim

[roddy]

Hello Tim

You will probably know (?); but just to confirm :-  the front chamber of the M/C feeds the large pistons of the front calipers.   Also, the front flexibles on each side are of different lengths.   The arc from the upper union on the inner wing always stays to the outside to attach to the pipe on the swivel, and the converse for the lower flexible staying on the inside arc.   If when you overhauled the calipers years ago, you made new pipes between the flexible ends and the piston tappings, check they are the same on each side (!)              (See you at GNW.)

Regards - Roddy

[lancialulu]

Hi Roddy

Re piping, Martin Cliffe suggested maybe the same thing getting them crossed over. I would have killed my self metaphorically speaking if that had happened but I went to check anyway. Yes I am still alive! I also took both calipers off the hubs and carefully exercised them by pressing the brake pedal down a few goes at a time. The side that pulls seemed to be no different in piston extension than the offending offside.

I am resigned to rebuild the o/s caliper and put new oem girling pads in and take back to the testers. But not before the GNW, which I and Sarah will delighted to meet up with you again.

Actually if they still are in imbalance I may just swop the lines round!!

Tim

[rogerelias]

Tim ,lucky you, my brakes pull up fine, but am running out of bodywork for it to stop could be the last GNW for us for a while in the HF
see you all soon

[lancialulu]

Epilogue

After much testing of open clipers on both sides I could not see any difference in "static" hydraulic pressure.

So I cleaned both disks and put new Girling OEM pads in and took it for a test run.

It still pulled slightly to the left and had a tendancy to lock the left wheel.

Back at my garage I had no option to rebuild the offending rhs caliper.

This I did and took for a test run - now no sign of pulling to the left - indeed on an emergency stop (a pedestrian wanted to examine the lancia badge on the front of my car just to be sure it was a Lancia!) it pulled up dead straight.

So back to the MOT test station.

Tester said what had I done to the front wheel bearing? I said I had replaced with new one with difficulty and great cost.
I asked why he asked that. He said that the other side was now a bit noisey!!! (I gues he was hinting that he would fail that side next year if I didnt replace that bearing with great difficulty and cost.

On the brake test it seemed to go OK.

On asking if it passed he said yes but only just??? What??? Well now it appears that the righ side is now the stronger and imbalance was 23% (fail at 25% apparently).

So I have a ticket to ride for another year with another caliper to rebuild and a new wheel bearing to sort.

The only thing I could see "wrong" with the old caliper is the seals seamed softer than than the new ones leading me to think that the soft seals act as a brake on the piston under pressure.

Moral of this story is to do both sides not just the "offending" one.

PS Having dismantled a 40 year old bearing on a car that spends most of its time standing around waiting to be used, and where the grease is all dry and horrible, I doubt the theory that bearings fail due a ball bearing denting a race. It may be on small bearings on other cars but on Lancias these are so big!!! Anyway I saw no damage and after a thorough clean and reassembly it is like a new bearing. - I may just reuse that one on the left hand side....

Tim

PS will be in 1600 Sport for GNW....but wanted my 1300 ready for the weekend in case snow was forecast!!!

[fay66]

PS Having dismantled a 40 year old bearing on a car that spends most of its time standing around waiting to be used, and where the grease is all dry and horrible, I doubt the theory that bearings fail due a ball bearing denting a race. It may be on small bearings on other cars but on Lancias these are so big!!! Anyway I saw no damage and after a thorough clean and reassembly it is like a new bearing. - I may just reuse that one on the left hand side....

Tim

PS will be in 1600 Sport for GNW....but wanted my 1300 ready for the weekend in case snow was forecast!!!

I couldn't believe the size and weight of the bearing when Omicron replaced one of mine a couple of years ago! what a job though, Omicron wouldn't quote a price for the job as it's a "How long is a piece of string" type job, due to how easy, or how difficult it is to remove, certainly made a hole in my pocket as it was a right B-----d to remove.

Tim, My heart bleeds for your decision regarding what to take to the GNW
Brian
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