12 replies to this topic

[Badger]

Hi All,

My problem began a few months ago when I fitted new front discs, pads & wheel bearings. Everything was OK for a week or so then gradually I began to notice a vibration through the steering wheel when braking. I checked brake disc run out & found one disc that was not within limits. I fitted another new disc & the problem went away for a few days but then returned with a vengeance.
I recently checked the disc run out again & found that the offside disc has a run out of 0.032". I index marked the hub, disc & shaft. I rotated the disc 180 degrees on the hub & checked the run out again. The high spot did not alter in relation to the disc but stayed adjacent to the hub index mark. I then removed the hub from the shaft & refitted it 180 degrees to previous position. The high spot has now moved to a position between the hub & shaft index marks. I am at a loss to explain how this can be & even more agrieved that I don't seem to be able to fix the problem.

Any sort of comments would be gratefully accepted, if any of the above made sense to you.

Cheers,

Nick

[Guess-Works.com]

The only possible thought would be the bearing race spinning in the hub which is causing the cv run out of true... Are you using Ball or timken ?

[Pavel]

If I were you i'd get a new hub and new bearings. Shouldn't set you back much more than 30 quid. Might as well fit two balljoints to it (7 pounds for a pair), and you've got a hub that's as good as new! At least it'll stop eating through your discs...

[Pavel]

P.S. I meant another used hub, and NEW bearings.

[dklawson]

I thought for disks you had to run the Timken bearings? (Except for 7" Cooper brakes... weren't they ball bearing hubs?)

Regardless, years ago I owned a Honda with a similar problem. I kept having the disks resurfaced and fitting them in different positions with similar results to what you're experiencing. In the end the problem was not with the brakes themselves but the hub/spindle. The CV joint passed through a splined hub pressed into the bore of the double row bearing(s). The hub had worn such that it was only supported on the "inboard" end. This let the outer portion of the hub wobble up and down, which it did with a vengance when the brakes were applied.

Your test method is excellent and does point to some form of problem with the hub.
You might find your Mini has problems similar to my old Honda. I'd take it apart and check everything for wear. (Including removing the outer race of the bearings so you can check them and the casting for wear).

[Guess-Works.com]

I totally agree DK, discs braked systems should use timken bearings, but there seems to be this growing school of thought over here ( on other forums ) that ball based bearings are stronger.... Where they have got this idea from I dont know but its getting ever more common..... hence the question.....

[dklawson]

Ball bearings are quite a bit over-hyped in almost all applications. The truth is that ball bearings involve point (Hertzian) contacts. These point loads cycle around the race and balls as the bearing rotates. They work great, with minimal friction, if the load is small. Exceed their design load and they fail quickly due to fretting of the mating parts, basically work hardening and fracture of the surfaces. The Timken (tapered roller) bearings have much more contact area and can support correspondingly higher loads. The advantage of ball bearings from a design standpoint is that you don't have to design in assembly tolerances to get the fit right. I guess that's why most modern front wheel drive cars use them... however, they typically use WIDE double-row single bearing setups that are quite a bit different than what the Mini uses. Given the choice I would never fit ball bearings to the front of my Mini.

by the way, I've always thought the way Mini bearings are assembled was ODD to say the least. Every other car I've owned used tapered roller bearings where you torque a spindle nut to some value, rotate the roadwheel by hand, then back off a single wrench flat to set the bearing pre-load and clearance. The Mini's roller bearings (or ball bearings) with their precision ground, matched spacers just seem odd to me.

[Dan]

Yup, I agree. Check your bearings for wear, and also the hub upright to see if the bearings are loose in it. If the hub upright is worn then new ones are currently on special offer at Mini Sport, 70 quid I think. I think this is quite likely to be the culpret as the position of the high spot has changed when you have released and then re-torqued the hub.

Edited by Dan, 14 January 2005 - 09:48 PM.

[Badger]

Hi Guys,

Thanks for all your replies, I am using taper roller bearings & the ball joints were all renewed when I did the original job a few months ago.

I'll strip it all down when I get the chance & have another look at it.

In the meantime I'll get another hub/upright ready to try as well, as that was what I thought would be the likely culprit.

Cheers,

Nick

[Badger]

Hi All,

Just to let you know the outcome of this little saga! Another new set of wheel bearings (taper) seems to have cured the problem.

Cheers,

Nick

[andyps]

I used to work for Timken and therefore know a little bit about tapered roller bearings. Basically, the use of a spacer helps ensure that during assembly the right loading is put on the bearings - small amount of end play if I remember correctly on the mini. Certainly all disc braked minis from the very earliest coopers on had tapered roller bearings, whilst drum braked ones had ball bearings.

Tapered roller bearings will always have a higher load capacity (and therefore life) than a ball bearing, and have the advantage over plain ball bearings of taking both radial (weight in a staright line) and thrust (cornering forces) loadings together. Angular contact ball bearings will do this, but only using point contact rather than full line contact along the roller.

Some car manufacturers have blamed tapered roller bearings (probably incorrectly) for brake judder.

If replacing the bearings has worked then it is likely that the bearings previously fitted were maybe not seated quite correctly - might have been a bit of dirt between the outer races and the shoulder in the hub.

[Verbree]

OK then, it is a while ago that you guys discussed this problem but: what do you mean by "HUB". Is it the main part where the 2 ball joints are screwed on or is it the part where the brake disc fits on? The latter is the FLANGE.

 

John (Holland)

reconsider Brexit...

[Rorf]

Simple google will give you the answer - yes hub has the ball joints on and the flange holds the disc and wheels on