My latest MOT tester just failed my car on 'excessive' rear wheel bearing play. Anyone knows what should be considered excessive? Just had the whole thing apart and there is maybe 1mm max play at 12-6 hour only(when I rock the wheel up and down), looks to me like it might be in the outer bearing. There is of course zero noise or roughness in the bearing itself and car drives absolutely fine. U joints are fine, output shaft bearing play seems barely detectable. Its a bit cold and wet atm to deal with this so I'm just hoping its a douche mot tester(there are plenty of them here) and I'm seriously considering 'special-no problems' retest now.

Of course the front wheel bearings play always go on advisory list, even though they are perfect and up to spec, it seems there are very few testers these days who know how to assess play in front wheel bearings

 

Katar,
Having been down this path with an MoT examiner a few years ago and spent some time looking into the position, I concluded that the type of wheel bearings fitted at the rear should have no play. Upon further investigation, it emerged that the play in the 12-6 axis was actually coming from the fulcrum bearings, where the hub assembly is attached to and pivots on the lower suspension arm. These are taper roller bearings, and hence a little play is tolerable/ desirable. Not a view shared by the MoT tester in question. When I took the assembly apart, my bearings were completely goosed, so although he was wrong , he was right. I viewed it as a score draw! There was no discernible difference in driving the car, but the MoT was passed and the issue has not reared its head again (touchwood!)

 

Luckily and surprisingly fulcrum bearings are fine on this one, I've inspected them properly in the summer when I had the whole rear suspension upgraded and no damage and no play there atm. My previous LWB though had these completely destroyed with disintegrated bearings and still passed the MOT easily as fulcrum bolt hold it stuck enough in the wishbone to not show too much play unless wheels were on the ground
I've ordered some SKF bearings and will tackle them eventually, I'm still annoyed though as 1mm in my opinion should not be considered excessive play, nor an MOT fail, but maybe I'm wrong?
By the way, whoever will have to tackle this in the future, its much cheaper to look for SKF part number when searching for these bearings instead of going Jag part numbers/shop/dealers, I think VKBA3473 are correct part number, that way I got 4 SKF bearings, to do both sides, at just over £25 altogether. Normally they would be at least 4-5 times that.

 

1mm is a huge amount of end play. The usual range is 0.002" play to 0.003" preload. To put this into comparison, a typical sheet of office copier paper is 0.004" thick. 1mm is 0.039", so about 20 times the usual amount of clearance.

 

If it was in the bearing itself then yeah it would be huge amount of end play, I was talking about bottom of the wheel tyre so will be greatly exaggerated, I don't have a dial to check anywhere close to the center but would be of course considerably less in there, not to mention 0.002" would be ok just for the output shaft bearing and you have two u-joints and another two bearings in the 'system'. So far the only info I've found on this was on Jag-Lovers where someone mentioned exactly the same play in the wheel top/bottom and he took it to a Jag dealer and they said its absolutely fine so still unsure on what should be considered excessive but pretty certain now it should not be an MOT fail.

 

Just to add to a great discussion, the end-float spec for the differential output shaft bearings is 0.001 - 0.006 in.

The wheel bearings are under preload set at the factory by the "adjustable spacers" and the very high torque of the one-time-use axle nuts, which off the top of my head is in the range of 230 - 250 ft. lbs. There should be zero detectable play at the wheel bearing, and only barely discernible play at the diff output shaft bearings.

 

Thanks Don, 0.006" would be 0.1524mm and I'm pretty certain mine is less than that when I pull/push the halfshaft so I'm sure that's fine. I've tried crowbar there too and I'm certain its within spec as its barely detectable by feel. My maths tell me that I should be expecting another 0.001" play in each u-joint as they are after all kinda bearings too and minimum play is expected and another 0.001" to 0.006" play in each of the two wheel bearings, which gives me up to 0.5mm play in the wheel bearing that should be considered acceptable. Anymore than that and its most likely too much and should be fixed whether its output bearings, u joints or wheel bearings. 0.5mm at the wheel bearing should be around 3mm play at the 12-6 hence I've concluded that mine is ok at most 1mm at the tyre and therefore MOT tester was just overzealous. Annoyingly MOT book doesn't specify what excessive wheel bearing is in any unit so its purely up to tester to pass or fail it in that department.

That said I've received my SKF wheel bearings and will attempt to replace it when weather allows. Annoyingly I've realised that I can't just fit the new bearings with the old spacer and anyone doing it, is doing it wrong or is just lucky and that's probably why we hear on various forums from people doing the job twice when using various bearings manufacturers as tolerances will vary greatly from one to another.
The Jaguar clearance(usually SKF or Timken used) specified is two to three ten thousandths of an inch if I got this right from the manual and the manufacturing tolerance of bearings could be more than this in a new set. To compensate I need to use a specific size spacer(Jaguar have them in various sizes) and neither I have tools to check it at the moment and/or honestly I'm to lazy to do it, especially in this weather

So, considering that my current bearings are I think SKF, and the ones I've purchased are too, I'm hoping they are very similar and going to cross my fingers, reuse current spacer and hope for the best. If that wont work I'll then purchase a dial and do it properly in the summer, with correct Jag spacer. I'm hoping replacement bearing will last at least that much as its 2C atm and that is way too cold to sit on a half frozen ground for 2 hours or so.

 

The rear wheel bearing specification is not a clearance or end-float, it is a pre-load, meaning the bearings and hub are pulled together until they touch, then further compressed so tightly that there is zero play. The specification is a minimum preload of 0,025 mm and a maximum of 0,08 mm, or 0.001 to 0.003 inch.

Here is the section from the Workshop Manual that gives the pre-load spec and calculation for shim thickness (for some reason all of the pdf versions of the manual that I have are missing the first part of the sample calculation in the upper left field):



The good news is that the manufacturing tolerances of the top tier bearing makers like SKF, Timken, Toyo, Koyo, NSK and NTN are so precise that we can almost always just clean and reuse the old shims with the new bearings and all will be well.

Most of the accounts of problems after rear wheel bearing replacement are from folks who discarded their shims or didn't keep track of their correct positioning during disassembly and then assembled them in incorrect positions.

With SKF bearings you should be just fine and don't sweat the shim calculation (SKF makes bearings for the Ferrari Formula 1 team - think of the precision tolerances required in that business).

The large images at Jag-Lovers have still not all been transferred to the newer servers, but the thumbnails and descriptions at these links may be helpful:

Rear Wheel Bearings Part 1 of 4
Rear Wheel Bearings Part 2 of 4
Rear Wheel Bearings Part 3 of 4
Rear Wheel Bearings Part 4 of 4

Do remember to use new axle nuts - the nuts have helical coil inserts that completely deform at the high torque specified by Jaguar and cannot be reused. At least two members of the Jag-Lovers forum who re-used their old nuts later reported the nuts loosened and fell off while they were driving their cars. (!)

Cheers,

Don

 

Well, just replaced these bearings and that did absolutely nothing, ok it maybe improved it by 20% but still get a noticeable play at 12-6(I say noticeable but its under 1mm in and out at the ends of the tyre). Had a second person rocking the wheel in and out and there is still a bit of play in the hub so I assume I will need a larger spacer. Annoyingly they are £22.50 from Jaguar so I need a reliable way to figuring out exactly which spacer I should go for. Of course couldn't find my caliper to check current spacer thickness but it looked to be under 3mm.
So what's the way to figure this out and what tools I might need for this? Or should I just pick half a mm thicker one and start there? I suppose could always sand it down if I need a thinner one?

 

The formula for calculating spacer thickness is shown in my previous post, but part of the example is missing in the chart from the manual. The full description probably exists elsewhere in the documentation. If I get a chance I'll see if I can find it.

My brain is tired, but I think that if you have excessive play and everything is properly assembled and the axle nut is properly torqued, you need a thinner spacer, not a thicker one. A thinner spacer will allow the roller bearing cones to squeeze more forcefully against the bearing races, increasing preload and eliminating play. A thicker spacer would prevent the cones from making firm enough contact with the races.

I'm sure you didn't make this mistake, but it is easy to mistake deflection in the rubber tire for movement in the hub. It's better to use the rim of the wheel as your reference since it is rigidly bolted to the hub and will not deflect.

Cheers,

Don

 

I was thinking about your extra play. Is it possible one of the new bearing races did not get fully seated in the hub due to corrosion in the bore? This could prevent the axle nut from pulling the assembly together as tightly as it is supposed to.

 

If it's a wheel bearing, it should be similar no matter what the clock position. If it's in a vertical plane only, it could be bad U joints in the halfshaft, output bearings in the diff (a known weak spot), or the lower fulcrum shaft bushings are worn.

 

That's not really correct as wishbone keep the hub static at 9-3 clock position so even if bearing would be completely shot, it would only move at 12-6.
Anyway, finally decided to tackle it today, took everything apart again just to see how this 'adjustable spacer' function, I've removed it completely and tightened everything up and that worked, no play other than a tiny bit from the output bearings. That kinda confirmed that I needed a smaller spacer. I've checked mine and it was most likely 2.97mm, I took maybe 0.2mm off with a grinder, a bit crude but didn't have any other way, put everything back together, tightened up main bolt as much as I was able to and play is gone.
Retest hopefully on Friday.

 

Sounds like maybe the 'stub-axle' diff output shaft deep groove ball bearing is worn?
There is a tolerance for that bearing. (it is NOT zero)

The axle halfshaft is the upper control arm.

 

See post #6 - I gave the tolerance for the diff output shaft bearing end-float.

Cheers,

Don

 

Ok, quick update.

I lose the will to live with these testers, it failed again, this time on left side headlight pattern, apparently leaky power steering hose and he wasn't happy with the 'rear wheel bearing' again. What I confirmed is that they cant tell the difference between rear wheel bearing and output shaft bearing, I literally had to get under the car, stick a crowbar between output shaft and flange to show him that wheel bearing itself is perfectly fine and there is 0 play in it and the only tiny play is in the output shaft bearing, which suppose to be there anyway. As soon as he understood what was happening with it he of course passed it.
While waiting for replacement headlight(it separated at the bottom so had a bit of condensation inside so I thought I'd get it replaced) I've decided to swap the output shaft bearing because it seems it will always be an issue going forward and I don't feel like educating mot testers every time I take it for the MOT.
Getting out the 4 nuts holding the shaft was an absolute PITA, think took me almost 2 hours to get them off, not only they were super stuck but of course needed a super long 11/16 ring spanner to even start them moving, rest was easy, although getting off old collar took a lot of brute force and cutting. Pressing them in wasn't a problem, think it only needed just over 6 tonnes to get both in but I did heat up the collar first.
With the new bearing in, end float is still at the higher end of the Jag spec. Is this in anyway further adjustable going forward? I'm just worried I'll have to deal with another overzealous tester next year.
Anyway, popped in new light and it passed the MOT with no issues.
Oh and the leaky power steering wasn't leaking, maybe a bit of engine oil on the high pressure hose but just cleaned it up and no leak whatsoever. There you go.
Also, of course they've put the front bearings as advisory, even though its barely detectable and well within spec. If you ever need an MOT in UK, make sure to stay clear of Cambridge

 

My X330 has just passed its MOT with two observations "Nearside rear outer (hardy spicer has slight play), and Wheel bearing has slight play nearside front."

 

Quick update as I think I've finally solved this little mystery, a year later, just before another MOT. So the 12-6 play is basically on ALL x300. I've checked three, all had play in the wheel with the outer pivot pin nut slightly loosened. There is one additional factor here that 'deletes' this play and its nothing to do with actual wheel bearing itself, neither with the output shaft bearing. Its all to do with adjustable spacer for the fulcrum bearings. These come in various sizes from 3.9mm to 5.5mm and set a 'hub preload' and basically 'lock' the hub. Honestly I'm not sure which thickness I've used while transferring rear suspension parts from my old to new x300 few years back(I might have mixed them up completely) but all I had to do was to fit a slightly thicker spacer and torque the big bolt to spec and that was it, there is 0 play in there in both wheels and its been like this for a few months now.
So if you have an overzealous MOT tester to satisfy, simply make sure the bearings themselves are fine, then tighten it up a bit more or fit a slightly larger spacer. No idea how Jaguar measure what spacer suppose to be in there in the first place.

 

I Have Recently been down this path with a WOF inspector in New Zealand . ( WOF is what they call it here but its the same thing ) Ended up tracing the source of the play to the Diff outputs which measured double their end float with a dial Indicator on a magnetic base. The Inspector failed to understand how the rear suspension worked but upon presenting him with the Jaguar Specs and a video of my readings he passed the car.

A tiny bit more at the diff stub makes for a lot more movement at the upright !