DaveK

In my vibrating steering wheel problem I want to clean up the calipers and make sure the problem is not due to corrosion. I know this can be a common problem.

However - where am I looking / cleaning? As I understand it the problem is a reaction between the pad backing and the calipers? So I would expect the corrosion etc. to be where the pads sit / slide in the caliper?

If so, I would think that the checking / cleaning up should be quite easy. The reason I'm a bit dubious is because my mechanics did this a few years ago - and I'm sure it cost me something like £700 - which means I must be missing something?

Heirsh

If they charged you that much did they pull the plates in the calipers and clean them up?

Dave have you tried simply removing your wheels and cleaning the spots where they mate to the rotor and making sure they go back where they belong (red stud mated to the right hole in your wheel)?

DaveK

I don't know if they pulled the plates. But what plates are we talking about? When I replaced the pads I don't remember seeing any - the pistons pushes on the back of the pads. Were there plates at the sides of the calipers?

I could try cleaning up the wheels - but they were not off between it being OK / vibrating.

Heirsh

I was just trying to figure what could cost that much. I doubt those plates would be causing this. I think they align the pads, but I cant remmeber what they look like in my head at the moment.

Dave, I'll send you a pm with some of my thoughts on this. Take them for what they are worth. just thoughts.

I do think a skimming of the rotors on the car while mounted would solve this by minimizing the high and low spots on your rotor

Bill Verburg

This is a 993RS front caliper but all the 964, 993 calipers are built the same
3 things happen to interfere w/ the proper function of all of these calipers

• mung collects behind the black steel pad positioning plates mechanically forcing the guideplates out of true
• there are dissimilar metals bolted together, when combined w/ moisture and especially road salt this leads to electrolytic corrosion where they meet
• the sliding and guide surfaces should have a light coating of Optimoly HT or Plastilube, this also helps reduce issues from item 2 above

DaveK

Bill - excellent photo. Thanks. But - I'm still confused and will ask a stupid question.

Where are the "pad positioning plates" and "guide plates" above? I assume they can't be behind the pads since the piston pushes on that. So presumably these plates are at the side of the caliper - i.e. the side edge / shoulder of the pads slide against them?

jimq

I just had the same problem on my truck the last couple of months with the wheel shaking real bad while slowly coming to a stop. Changed out the front rotors and all is well again.

Bill Verburg

The red is the painted aluminum body, the pads are obvious(I think) the pad positioning plates aka guide plates are anodized black you can just see the ends under the pad(remember the pic is upside down)

here is a rear caliper w/o pads, the guide plates here are silver(covered in mung)

Heirsh

Good shot bill, thanks.

DaveK

OK - I've got it. Thanks a lot.

Will take a look at mine this weekend (although I'm not entirely sure what "mung" is - but I'm guessing if I've got it, it will be obvious ).

DaveK

OK - just took a wheel off and pulled one of the pads out of the caliper. Don't know if there is significant corrosion behind it - but there certainly is plenty of crud (which I guess is the same as mung) all over it. It certainly won't be helping smooth pad movement.

So - over the weeked, I'll clean them up and put some lubricant on them. Any tips on cleaning them up? Looks like it would be eaiser with the caliper removed from the disc?

Also - how difficult is it to take the plate off and make sure it's clean behind it? Would this be a good idea - and since it was only done a couple of years ago (10-20K miles probably) is it even worth it? I guess if it's easy to get off / on it would make cleaning it up easier.....

stuart1997

Its a pita m8,to remove the spring plates you must heat the reatining screws (if they are not little brown blobs) up untill they are cherry red cus the are fixed with special loctite stuff.
Pesty has done his calipers -search caliper repair
cheers stu

warmfuzzies

Dave,

Cleaning the corrosion is not a quick task. Especially if you want the repair to last, I did mine earlier in the year.
You may well find that the corrosion extends to behind the dust seals, it realy needs to be thouroghly cleaned back to solid ally. Then painted to protect this area from corrosion again, I used Hammerite paint in this area on mine.
This will make sure that pad changes are easier as the corrosion dosen't then nip the pads also making braking difficult....
I didn't use heat on mine, but a small chisel, and then a drift to drive the button head bolt round, I don't always agree with serious heat and vital rubber parts in close proximity....just a personal thing.

Kevin.

Pesty

Yep to get the plates off if they are a bad state is a real pain in the ***!
took me ages with heat and chissles and hole punches.
I have finally got off my **** and taken the calipers to be powder coated and have new seals fitted.

This is what happens. the corrosion gets behind the plates forcing them out. As you can see this means the pads will not fit unless you trim some off. Also notice teh corrosion at the side of the dust cover.


Dave if you do not want to tackle them yourself the place I took my to be coated will remove them obviously at extra cost but nowhere near £700. probably nearerjust over £200 with a powder coat

Wait a week or so And I will show you how mine have turned out.
Will update the other thread with prices of seals and dust covers.

DaveK

Mine are nothing like that bad - and my pads fit in easily. I think I can probably avoid removing them because they were done not that long ago so I don't think I'm suffering from that problem again (yet).

I will stick to cleaning the surfaces and a little lubrication. If that makes no difference (and I suspect it won't) then I'll look at changing the discs.