Front brake caliper issue v8

cobraboy

Well-Known Member
#1
Evening all
Am trying to get to the bottom of a braking issue and wondered if anyone else was having, or has had problems.
Three years ago all the caliper's were removed and re sealed. Periodically the straight line stopping has been, well iffy ! the car will not pull up straight under hard braking.
Lots of time sent on all bushes, links. arms, idler, etc etc.
Now gone 360 and come back to front caliper's.

Have bought another seal kit and on fitting have found it impossible to fit the large piston by hand, it was tight to get out. I part pushed out the pistons on the car before removing the caliper and was surprised at the amount of pedal effort needed to move the pistons.

The small pistons can be pushed into the caliper by hand. Without the seals in the caliper all the pistons will drop into their bores.

So with a measuring stick I have found the large pistons measure 57.2mm and the small ones 40.4mm. I wondered if they were supposed to be 57mm and 40mm and the remanufacturer made them finished size and then when they were plated they ended up too big ?, as I threw my Girling pistons three years ago I guess I'll never know.

I telephoned a supplier today and he kindly measured his stainless steel pistons and the result was the large were 57.08mm.
I cannot do anything with a plated piston, but I can linish a stainless piston, so I think I will purchase two stainless pistons and get them to 57mm and see how they fit.

The other thought with this would be seal sizing, the seals are made by Nelson and the supplier who measured the pistons has said that they have used their kits for many years without issues, so I guess I have to discount the seals being too big. Although I did wonder about the material, it is not rubber, maybe its EPDM and maybe it is not as giving as rubber and the same section size is too big ?

If all this is making your head hurt spare a thought for me ! I need some positive vibes guys and a solution please :confused:
 

sdibbers

Well-Known Member
#2
Certainly sounds like an issue with plating making the pistons out of spec. So new seals and pistons in your future? If it were me I'd just try the new stainless pistons straight out of the box. If they feel tight in a trail fit then polish them down to 57.00mm dia. I've chased problems like this on the rear calipers on my car. Turned out they had been resleeved and were a little under on internal diameter. That and a tiny sharp edge at the face of teh sleeve that would damage the seals during fitting. I was able to ream the bores and make a tool to protect the seals during assembly, not had a problem since. But, like yourself, I was chasing hanging brakes and irregular brake feel for 2 years.
 

cobraboy

Well-Known Member
#4
Yes I would think at the time imperial measurements were used, but now the pistons seemed to be metric sized.

Brake Caliper Piston 57mm Girling Type

Anyway there is good news to report, the problem is solved, well bar road testing anyway.

The Nelson Stokes brand large seal supplied by Wadham's is incorrectly sized.
I visited the excellent Past Parts at Bury St Edmunds today and tried a stainless steel piston in my caliper fitted with the Nelson seal, it would not go in by hand.
During the day I had downloaded a Girling part number sheet for the Rover calipers and using the numbers the guys at PP tried to find what they had for that caliper. They turned up a pair of genuine large piston seals !!
It was possible to see with the naked eye that the section of rubber was smaller, measuring revealed the OEM seal to be 0.115" thick and the Nelson seal to be 0.130" thick.
I have come home and the pistons I have went right in with no trouble.
I have removed and measured the Nelson small piston seals and they are at 0.115" and these pistons are OK to fit, PP did not have any OEM small seals anyway.

So hopefully over the weekend if time allows I will fit and test.
Thanks for the reply's folks.
 

sdibbers

Well-Known Member
#6
I am afraid one or two items I have had from them have been proved to be suspect. I have had to turn bushes down to fit, conversely other items have been fine.
On their rebuilt rear calipers they've been known to just increase bore size for the hydraulic piston and make a larger piston and seal. It works, but it also changes the brake balance between front and rear. Not good, especially as you can do the right thing and sleeve the bore.
 

cobraboy

Well-Known Member
#7
Well the car is together, but unfortunately the weather has turned colder and there is salt on the roads, so testing will have to wait.
On the subject of rear calipers, whilst at Past Parts the other day I came away with a re sleeved rear caliper bare body for 40 quid ! to build up to replace my leaky one, very pleased with that for value.
 

cobraboy

Well-Known Member
#8
Spoke with Nelson Stokes today regarding the seals, they were interested in my findings but said as I had bought the kit from Wadhams the correct thing to do was to go back to Wadhams and raise a customer complaint, then it would work back to Nelson that way.
So I called Wadhams, and the response I got ……………. " We sell hundreds of those mate "

Now when someone responds with that line you know you are on a hiding to nothing !
Life is too short for a crusade over a brake seal, so the best advice I can offer is, if you cannot get a caliper piston to go in with reasonable hand pressure then measure the seals.
 

quattro

Well-Known Member
#9
So I called Wadhams, and the response I got ……………. " We sell hundreds of those mate "
Really, and he's usually so helpful [/sarcasm]

I had problems with some re-chromed pistons from another supplier. They leaked and upon close inspection, they were ribbed. I replaced them with some stainless ones but didn't get much back up from the supplier.

Richard
 
#10
So I called Wadhams, and the response I got ……………. " We sell hundreds of those mate "

Now when someone responds with that line you know you are on a hiding to nothing !
Life is
Spoke with Nelson Stokes today regarding the seals, they were interested in my findings but said as I had bought the kit from Wadhams the correct thing to do was to go back to Wadhams and raise a customer complaint, then it would work back to Nelson that way.
So I called Wadhams, and the response I got ……………. " We sell hundreds of those mate "

Now when someone responds with that line you know you are on a hiding to nothing !
Life is too short for a crusade over a brake seal, so the best advice I can offer is, if you cannot get a caliper piston to go in with reasonable hand pressure then measure the seals.
sounds about right, ive had similar and then some.

re caliper seals ive also had the opposite , when i got some for some mk2 zodiac calipers, pistons went in great, but seals were too small and calipers leaked instantly, fitted some second hand seals (not recomended i know) calipers perfect and still going strong a couple of years later!
 

cobraboy

Well-Known Member
#11
Well …. not uncommon then. I guess it is check and check again when buying repro brake stuff.
I have now acquired a NOS genuine front caliper seal kit which is in perfect condition. I have always been hesitant about buying safety critical stuff that has been stored for so long, I don't think I would trust a NOS flexi hose, but having said that why would you trust a knock off one ?

I have also just got two new hydraulic piston lip seals for the rear calipers that I have just taken off, these are not genuine so will be checked for size and stored so that I have a rear caliper set ready to go right on.
 

cobraboy

Well-Known Member
#12
Well..... many more hours have gone into this since I last wrote.
The weather has been kind, so I have been out testing..... and still the car was not behaving satisfactorily.

The more testing I have done, the more I have realised that the pull to the left is more of a twist through the car. So I have spent time lying underneath looking at the rear caliper's.
With Harvey's advice ringing in my ears that both handbrake levers must be resting on their stops when the handbrake is off I was looking and they were - all OK.
I then got my feeler gauges and checked the gap between pad and disc as best I could, and they appeared even at around 0.007", all good.

Now the car had just passed its MOT and I used the rollers as a balance test and both axles were well balanced !

So back to the handbrake levers, I noticed that there took more travel to pinch on the disc on the off side caliper then it did on the nearside ? odd !
I then looked carefully at the inside pads that have the mechanical piston pushing on them and saw that the nearside pad had the piston tab at 12 o' clock, whereas the offside piston tab was rotated to nearly 2 o' clock.
Is anyone still awake ?

So with a long screwdriver I pushed the offside piston round so the tab was at 12 o'clock thus winding out the piston a bit, this made an equal amount of movement on the two handbrake levers.

I got in the car and the handbrake lever had a noticeably shorter travel.

The pad backplates are the stock ones re lined but the piston tabs seem to have a big gap over the top of the backplate allowing the piston to avoid clicking up when auto adjusting, I will make the tab a closer fit to the backplate in the future.

So to a road test...…..
Braking sharply from a low speed - straight and true !
Braking from a HIGH speed strongly down to a stop - straight and true !

The nearside front wheel still bobs out when the brakes are stabbed to dip the front down hard, but this does not seem to affect braking in the course of normal driving.
Of course I found all this out on the day that the new braided hoses I ordered for the fronts turned up :rolleyes: so I have nice shiny hoses there too now !

Its been a long journey this one, I hope the saga may prove useful reading in the future to anyone with a similar issue.
 
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