Uneven Brake Pad Wear

[ArthurH 7]

I'm hoping someone may have an idea as to what is causing the pads to wear unevenly on our race 205.  It has to run standard calipers and we run Ferodo pads.  The pads in each caliper are evenly worn but the nearside pads are wearing at twice the rate of the offside.  This has been the case for several sets of pads.

 

The pistons seem free, and so do the sliding 'pins'.  The nearside caliper is very recent - it was replaced to replace a stripped bleed valve.  I would have thought a sticking piston may cause uneven wear within a single caliper, but both pairs of pads are evenly worn.

 

I'm informed that our master cylinder is the 406 type (4 outlets).

 

[Thijs_Rallye 87 4 Cars]

Put it on a brake analyser. I assume it being a track car the brake hoses are braided ones, therefore my first suspect would be one of the brake limiters.

[Richard309Sri XU5JA 205GTi 8]

are they girling calipers? unventilated type? does it have new discs on both sides? 

 

 

[ArthurH 7]

Thank you for your suggestions - sorry for the delay in my response, I hadn't realized I didn't have a notification of reply set  (I have now)

 

They are Bendix (OEM) calipers, yes the disks have been recently replaced and are in good condition.  It does have braided hoses, and an adjustable brake bias valve to the rear brakes.

 

TIA

[welshpug 1,657]

sounds like a 1.6 gti?

 

how is the master plumbed?   pair for front and single output to the rear?

[ArthurH 7]

Hi Mei, yes it is a 1.6GTI (racing in the 750MC CSH).

 

Exactly as you say, the two most forward of the master cylinder outlets are used for the two front brakes.  One of the other rearward outlets goes to the bias valve and then on to the rear brakes, the other outlet is blanked off.

 

I should have said in my first post, it is only the huge difference in wear that is a problem (specifically the expense...) as my son (whose car this is) is not detecting any pull to either side while braking.

[Richard309Sri XU5JA 205GTi 8]

On 9/18/2021 at 9:11 AM, ArthurH said:

They are Bendix (OEM) calipers,

are they unventilated? 

 

I declare an interest as I have been doing a lot of work on my brakes recently. I just keep wondering what's

causing this problem is this topic now. 

 

I found some of my old brake pads. I attach pics. I have the girling type calipers. 

 

Looking at them again I now noticed that I have also got uneven wear on these old ones.  

 

So on these I think the "outside*" pads on each side are more worn than the inside. 

 

I think this is the same as what you are saying is happening with DBA bendix calipers?  

I am not sure now which is nearside and offside - and in the posting - I'll just check that again in a minute. 

 

*so for me Im saying the inside pads are next to the caliper pots. The outside pads are the ones nearest the wheel. 

 

I know that on these pads the anti knock spring - I think it's called - is on the inside on both sides

ie next to the brake caliper piston(pot) 

 

The see saw type spring is on the outside on both sides - ie next to the caliper "g clamp" body 

 

I did a video on the brake calipers working a few weeks ago as I just was interested, and looking again I noticed that the inside pad is doing 95% of the movement.The pads are sliding along two pins on these girling ones. 

The sliding part of the caliper doesn't seem to be moving. That I mean which is connected to the strut - there

are two seem to be movement covers for the whole thing to move back and forward relative to the strut. 

 

Just interested to know if anyone else is having the same wear patterns? Is this normal and is this how these all work? I'm not a pro. mechanic so I don't see these coming and going day in day out. 

 

Could be this is normal wear and this is how they work generally on all calipers? 

[DamirGTI 342]

Not normal ... should wear near identical amount inner/outer .

 

If it's the outer which wears more , then it's the sliders/guide pins holding the pad on the disc after the pedal release .

If it's the inner , commonly piston/square cut seal problem .. if severe piston/square cut seal problem , could wear both pads but you'll notice hot rim/smell/grinding/pulling at one side .

If it's wear at an angle , sliders/guide pins on one side bad , need greasing etc. ..

 

IR thermometer is handy tool for checking the brakes .. if they're dragging , which one which side and how much .

 

Also , plugged rubber flex hose will act as an check/non return valve , holding the pads onto the disc after releasing the pedal .

These can also be very dangerous during hard/emergency braking from high speed particularity if on one wheel only , will lock and can spin you over off the road into the ditch (had that happened years ago on one rear wheel , it spun me around instantly nearly ended up in the river deep down the road in bits and pieces).

If in doubt , and especially if no known history of them hoses being replaced , replace all of them at once front and back .  

 

Other , disc out of round or bad wheel bearing ... that needs to be checked with the dial gauge .

 

D