on-car lathe or on-car brake rotor resurfacing for VWs?

I have heard about on-car lathes for resurfacing brake rotors on American-built cars such as GM and Ford.

Does anyone know if there is a lathe that can also be used on VWs? Do you know of a shop in Madison or Milwaukee, WI that can do this job?

A brief explanation of my problem; I have a 1995 Passat GLX VR6 that appears to have a slightly bent front spindle. I have replaced or turned the rotors a few times and a pulsation returns after a few weeks. I dial indicator shows me .009in of axial runout on the (new) rotor. Another symptom is that this wheel consistently runs 5 to 10 deg F hotter than the other wheel. I have estimated that the runout must be wearing flat or low spots into the rotor and the resulting thickness variation is what causes the terrible 'warped rotor' feel.

btw, the 'Good' side rotor has only .001in axial runout which I think must be quite good.

I have tried using shims to correct the runout but this did not work at least on the first try. I am going to try with shims again this weekend but I think my chance of getting close to .001 runout is low. I am quite confident that if the rotor could be turned without removing it from the spindle then everything should be golden.

appreciate any help!

Mark

1995 Passat GLX VR6 (165k miles)
Reply to
Mark
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have you considered that it could be caused by a defective wheel bearing?

Mark wrote:

Reply to
nathan

"Mark" wrote

Have you considered removing the knuckle and have a new bearing pressed in at a local auto machine shop? A damaged steering knuckle casting? You have anyone in the family driving the car capable of hitting a curb or something and not tell? You might want to consider swapping the knuckle with a used one from a yard and while it is out have a new bearing pressed in. Cut the rotor and try again, imo.

Harry

Reply to
Harry

Yes, that is a good thought.

I think I have eliminated this possiblity for a few reasons.

- There is no noise coming from this wheel

-I have measured the temperature of the wheel and the brake rotor with an Infrared temp sensor and the 'bad' rotor is always hotter than the good rotor. The 'bad' wheel is always hotter but not by as much. This tells me that the heat is originating at the rotor.

- I once backed off the brake pad with a piston retractor and then drove 48 miles without touching the brakes at all (do not try this at home!) This was all freeway driving during non-peak times of course. Both wheels ran colder and both were the same temperature. I have a manual transmission and I did the final stop using the E-brake; gently.

Thanks for the suggestion, I do not mean to sound so smarty-pants but like I said in the original post, that was the short story. I have been analyzing this problem over a period of many months and I make the same long commute every day so I get a chance to check things a lot of different ways.

Thanks again!

mark

Reply to
Mark

I just checked the Bentley manual. I was trying to solve the problem without disassembling the pressed parts and without visiting the shop. After viewing the exploded diagram, I think the 'Hub' is the part that is likely damaged. Perhaps it was damaged by a shop changing the wheel bearing. The bearings have each been replaced at least once. The bearings in the front wheels are a weak point on this car.

If I do not find an on-car lathe and If I am unable to fix this with shims then I will pursue a new hub and bearing at the shop down the road.

Thanks for the help!

mark

Reply to
Mark

"Mark" wrote

Here you have to wonder about heat deformity causing the rotor to be out of flat. Have you looked at the caliper to make sure it is not binding? Perhaps the caliper is holding pressure via a blockage. To pretty much guarantee a fix if you get used parts that are cheaper when you buy more in a package, especially cheap if you pull the parts off yourself, I would pull a caliper, steering knuckly (hub), buy a new bearing and press that into the the used steering knuckly that should be like new when you are done, then, cut the rotor and try again.

Buying the caliper should guarantee it to be fixed since you replaced everything. THIS could be a legit approach to a person who has spent an unbelievable amount of time troubleshooting without solving. You may buy the knuckle to find out later it is the caliper so replace everything especially while you are there (if by chance you do this) pulling used parts will take

5 more minutes to pull off - AND I would get used parts except a new bearing that should be new and easy to do with the hub (knuckle) out. If you really wanted to go budget you could try the donor bearing (used) in the hub (knuckle).

In my local yard they only charge about 10 to 15 dollars for a used caliper if you pull it yourself. Knuckle would be 15 to 25 dollars. Cutting the rotor if it has clearance would only be 10 dollars or less SO you could replace everything for less than a hundred dollars (depending where you bought the bearing) and be done with the problem.

Harry

Reply to
Harry

Now that's the correct way to fix it! Yes, the hub can be bent if not done with caution when replacing the bearings. I have seen a fellow worker in our shop bend one.

Reply to
Woodchuck

Reply to
nathan

Thanks for spending the time to write this well thought out approach, Harry.

I forgot to mention that I have already replaced the entire caliper assembly including the guide pin and carrier via my VW dealer. I also replaced the flex hose at this wheel. Now that I have done both those things and have exactly the same problem I am confident neither of these was at fault.

I think I have a consensus that the hub/bearing/knuckle assembly is the source of the problem. I personally believe that the last shop to replace a bearing did the bending. My only confusion is how I could have gone this long without such problems. All I can think is that the same shop may have somehow corrected their error with the old rotor via shims or the lathe I asked about and when I replaced the rotor the problem returned. Come to think of it, I should call that shop! I can tell them "remember me? You replace my wheel bearing 4 years ago and now I have a problem with it!"

Seriously that shop can have the job if my 'home grown' shim fix does not work.

Thanks to all for all the help.

Mark

Reply to
Mark

"Mark" wrote

Yeap, as I said before, looks like the hub (knuckle)

I just wanted to say one last thing, probably silly to mention as surely you would know this, that, I am sure you were cautious about and perhaps should have reread you original post as you may have said it, but

I assume your rotor on that side was not cut, if cut, previously below the minimum specs and if it was cut it was miced because if the rotor was cut (obviously) below specs of allowability of thickness it very well may warp from heat and become deformed and would be hotter.

Harry

Reply to
Harry

Yes, that is worth mentioning.

I have been through this sequence.

  1. new rotors (ATE), went bad in a few weeks on the bad side
  2. recut these rotors, smooth as silk at first but went bad again in a few weeks.
  3. new rotors (ATE) again; trying to find the fix before this one goes bad as well.

note, I have been replacing parts on both sides the same even though only one side is bad. I do not want any uneven performance.

btw, the ATE rotors are good. the problem is apparantly with the hub of my front-left wheel as indicated in the other messages in this thread.

Reply to
Mark

Are you correctly tightening down the wheels? Are you overheating the brakes and not allowing for proper cool down?

Reply to
dave AKA vwdoc1

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