One wheel spins more than other

[MakaveliX]

Mercedes C240 2002 32K miles. ( Rear Wheel Drive )

Noticed today that when jacked up, the passenger wheel moves more freely than the driver if I spin it by hand.
I have taken the brakes apart and thoroughly cleaned them and lubricated the sliders and put ceramic brake grease on the contact points but still seems to be the case.

Can't see any evidence of runout on the disc. No issues braking at all, no juddering or pulsing or vibrations etc, all lovely and smooth. Car drives great, no loss of speed or anything like that,

Could it be old and dry wheel bearings, possibly a stuck calliper? I have had the car sat cold for a few hours and still seems to have more resistance on the driver than the passenger.

Any ideas ? The only thing I noticed is the backing plate of the pads ( on the driver AND passenger ) had slightly come apart. Yet the only resistance appears to be on the driver, not the passenger.



Is it just me or does the pad wear look a bit wonky ?

Edited by MakaveliX on Saturday 22 June 21:13

[sf1969]

I suspect that the slider was sticking, that would cause the pad to wear at an angle. If it’s still dragging, is the piston really clean and going all the way home when pressed back? I had this with a Discovery 4 very recently and after cleaning the sliders and putting me pins in, one rear brake was still dragging and you could feel it was hotter than the other side. I was pleasantly surprised at the price of new calipers so replaced both sides. The issue is now cured. PS never been a big fan of single piston, sliding calipers for just this reason.

[InitialDave]

Did one still spin more easily when you had the brakes apart?

[MakaveliX]

InitialDave said:

Did one still spin more easily when you had the brakes apart?

That was what I was wondering. I didn't check this no, I suppose that's a good way to rule out the brakes isn't it.
Should I hang the calliper and then spin the discs to see if there is any difference in resistance with the brakes off ?

[InitialDave]

If it's quick to do, it'd certainly help make sure it is brake related, which is the most likely case.

[MakaveliX]

InitialDave said:

If it's quick to do, it'd certainly help make sure it is brake related, which is the most likely case.

OK yeah I will give that a go when I get a chance. Let's be honest the car is 22 Years old so things like this are probably likely. It's really a project car but I do have pride in keeping it running well.

Will also try properly cleaning the piston out too.
Thanks for the advice.

Will also see if I can feel more heat coming from the driver side tomorrow after a drive

[Smint]

Assume its a front wheel, have you exercised the pistons in their bores, leave a pad in and operate the brakes till the piston is out, push back in, rinse and repeat...choose whichever pad you want to remove to make levering the piston back easier.

After doing this a few times both sides you'll get the feeling if there's too much force needed both for pushing out (servo exhausted) and levering back in.

When the piston is extended you could peel back the rubber dust seal and judge the condition of the piston, also lubing piston with correct brake grease is permissable, i use a cotton bud for this.

Issue at rear? same method but also check the park brake isn't dragging.

[MakaveliX]

Smint said:

Assume its a front wheel, have you exercised the pistons in their bores, leave a pad in and operate the brakes till the piston is out, push back in, rinse and repeat...choose whichever pad you want to remove to make levering the piston back easier.

After doing this a few times both sides you'll get the feeling if there's too much force needed both for pushing out (servo exhausted) and levering back in.

When the piston is extended you could peel back the rubber dust seal and judge the condition of the piston, also lubing piston with correct brake grease is permissable, i use a cotton bud for this.

Issue at rear? same method but also check the park brake isn't dragging.

Thanks for the useful info, yes it's the front driver which has more resistance than the front passenger.
The inner pad on this car doesn't clip into the piston itself, it sits in the carrier. this style...


In regards to the first line of your reply, do you basically mean pump the brakes and keep pushing the piston back to ensure it is moving back and forth properly ? I usually work on my own so it would have to be doable myself.

In regards to brake grease, I could definitely try that. I do have ceramic brake grease which is specifically designed for the pads. I have silicone grease which from my understanding is the best stuff for anything rubber.

[E-bmw]

MakaveliX said:

Smint said:

Assume its a front wheel, have you exercised the pistons in their bores, leave a pad in and operate the brakes till the piston is out, push back in, rinse and repeat...choose whichever pad you want to remove to make levering the piston back easier.

After doing this a few times both sides you'll get the feeling if there's too much force needed both for pushing out (servo exhausted) and levering back in.

When the piston is extended you could peel back the rubber dust seal and judge the condition of the piston, also lubing piston with correct brake grease is permissable, i use a cotton bud for this.

In regards to the first line of your reply, do you basically mean pump the brakes and keep pushing the piston back to ensure it is moving back and forth properly ? I usually work on my own so it would have to be doable myself.

It is absolutely doable as a one man job.

Remove caliper, push pedal down, push piston back in, push pedal down, after doing it to all individually you will have a feel for how easy they are/aren't moving freely or not.

[InitialDave]

I usually zip tie a block of wood into the caliper when doing that

[MakaveliX]

E-bmw said:

It is absolutely doable as a one man job.

Remove caliper, push pedal down, push piston back in, push pedal down, after doing it to all individually you will have a feel for how easy they are/aren't moving freely or not.

OK I get you, thanks ! Will give it a go when I get a chance.

Best to get a caliper rewind tool so as not to damage the piston seal right ?

[E-bmw]

MakaveliX said:

E-bmw said:

It is absolutely doable as a one man job.

Remove caliper, push pedal down, push piston back in, push pedal down, after doing it to all individually you will have a feel for how easy they are/aren't moving freely or not.

OK I get you, thanks ! Will give it a go when I get a chance.

Best to get a caliper rewind tool so as not to damage the piston seal right ?

If they are wind-back callipers yes.

[Smint]

MakaveliX said:

OK I get you, thanks ! Will give it a go when I get a chance.

Best to get a caliper rewind tool so as not to damage the piston seal right ?

Almost certainly they won't be wind back calipers, simple leverage will do the trick.
Wind back are usually found where the park brake operates on the same (typically rear) pads as the footbrake, adjustment via internal mechanism inside the caliper, its a cheap inferior design to what your Merc probably has fitted, ie the superior drum inside disc independent park barke...also wind back calipers make its difficult to exercise the pistons in the bores as we are talking about here, hence why calipers on such cars tend not to last the distance of other designs.

When exercising the piston on a single piston sliding caliper (which i think yours is) i usually leave the pad in place that's beside the piston, that way you can shove a tyre lever large screwdriver whatever in the other side of the disc and push the caliper back thereby pushing the piston back in.
Or if you have a suitable flat ended lever you could leave that in place beside the piston when pumping the piston out, that way the lever is already in place to squarely push the piston back.

Exercising the pistons and lubing sliders etc as part of proper annual or every other year (no longer imho) brake servicing will see calipers lasting decades, and you've got fully working brakes on all wheels at all times.

[MakaveliX]

Cool thanks for the useful advice

Just jacked the car up trying to diagnose something else and both wheels now seem to be spinning evenly and freely.
I will still check the condition of the pistons etc just for good measure as the sticking may come back in future or may be intermittent.

When you say simple leverage do you mean like getting two pry bars and pushing the pistons back ?

I was always taught to use a windback tool
Here on autodoc, they definitely use a windback tool...
https://www.youtube.com/watch?v=ea4xxt9IuMo&t=...



Here is the caliper

Edited by MakaveliX on Monday 24th June 21:22

[E-bmw]

That isn't a "wind-back" calliper, simple force with slip-joint pliers, a G-clamp or similar will work just fine.

Wind-back callipers always have locating holes/slots/lugs for the wind-back tool to fit into.

[Smint]

MakaveliX said:

Cool thanks for the useful advice

Just jacked the car up trying to diagnose something else and both wheels now seem to be spinning evenly and freely.
I will still check the condition of the pistons etc just for good measure as the sticking may come back in future or may be intermittent.

When you say simple leverage do you mean like getting two pry bars and pushing the pistons back ?

I was always taught to use a windback tool
Here on autodoc, they definitely use a windback tool...
https://www.youtube.com/watch?v=ea4xxt9IuMo&t=...



Here is the caliper

Edited by MakaveliX on Monday 24th June 21:22

You've triggered my OCD now, that caliper would have to be painted in black hammerite before refitting

You don't have to lever against the piston at all with that type of caliper, in situ you can lever the other side of the disc and the psiton will push back in, as a bonus the sliders get a good workout.

Never used a wind back tool on any of my own cars, but then none of my cars have had the type of piston crown in E-BMW's pic, i have a set but they only get used on family cars with suitable calipers.
Preferring levering because you can judge the pressure needed to push the pistons back in more accurately.
As noted in E-BMW's post i sometime use a huge set of adjustable water pump type pliers to push things home, they fit right round the caliper, again you can judge the pressure needed to push things home.

[MakaveliX]

Thanks! something new learned there, will get myself a G-Clamp.
How come on the Autodoc tutorial for my car they use a rewind tool though ?

To be honest the G Clamp looks more basic and simple to use so I'll get one of them.

[Maxdecel]

MakaveliX said:

How come on the Autodoc tutorial for my car they use a rewind tool though ?,

Probably the wind back kit they use is for front & rear (where the caliper mechanism has the piston adjustment rewind)
Here's another type.

[donkmeister]

If you find the brake fettling doesn't resolve it, Mercedes used "proper" wheel bearings that have adjustment. If it's nipped up slightly too tight it will drag slightly.

Adjustment isn't technically challenging, it's an hour's work with a dial gauge and magnetic mount (bet some do it by feel). However I found it annoying and frustrating.

If it comes to it, new bearings aren't expensive, and you get to use some funky coloured grease too. I used Febi Bilstein bearings on my W211 and it really wasn't hard.