Lotus Elan

Rear wheel bearing - "Knocking from suspension over bumps"

PostPost by: rgh0 » Sat Jan 06, 2018 11:00 pm

Hi Jon

Given the depth of the groove on the worn shaft I would replace it. The stresses are greatest at the edge of the bearing and the stress raisers induced by the groove will still be present even after metal spraying so a future failure at that point I would worry about.

I suspect the taper is also worn and you may find the hub also so that on reassembly the wheel hub moves to far in and either hits the bearing on the inside or the nut and washer bottoms out on the shaft on the outside. A new shaft and potentially a new wheel hub unfortunately

The strut bearing mount areas also look like they have worn and a excessive amount of anaerobic bearing retainer used (the red stuff is probably Loctiite). You need to clean out the strut bearing areas and measure the clearance with the bearings. It is supposed to be an interference fit which you clearly dont have.

Repair of the strut alloy castings is possible by welding and re machining the bearing areas but it may end up being cheaper to get a new or used strut.

cheers
Rohan
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PostPost by: alan.barker » Sun Jan 07, 2018 6:03 am

rotoflex-circlip-001.jpg and

When i remove rotoflexs/doughnuts i always compress them first so the bolts come out easier.
I also jack up under the chapman strut to have the drive shafts as horizontal as possible. That way the rotoflex/doughnut is not deformed/stressed.
Before i fit new doughnuts i remove the band and fit my device and compress the doughnut. I use the rear brake disk and the 3 screws in the clips to aligne the bolt holes perfectly.
I have found with new doughnuts they are supplied with a band around them but the alignment of the bolt holes is not very good. When i do it like this on assembly i can slide the bolts into the holes with my fingers and no bashing or swearing.
Alan
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PostPost by: JonB » Sun Jan 07, 2018 7:10 am

@Alan
Yes, I used the same rig to get the dog nuts out. Main problem was a bolt seized into the dog nut sleeve. I am thinking about CV joints so maybe I won't have to muck about with Rotoflex joints for much longer. On the other hand, I do have another set, used, but look to be in OK condition.

@Rohan
The outer bearing was a good tight fit in the carrier. I would reassemble with Loctite (which product would be best?) and get on with it. If the carrier really is toast we'll soon find out. What I'm saying is the old bearing was OK, even the inner race, and I think there is no need to go to all that expense if the carrier can be made to work with some Loctite. Would love to spend spend spend but there is a limit.

Regarding reassembly, should I use Loctite on the inner race too? And the inner bearing (it has an O ring round it to seal out muck)? I think I have concluded a new shaft is in order her by the way.
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PostPost by: alan.barker » Sun Jan 07, 2018 8:03 am

Jon for sure the best way is a new drive shaft for peace of mind and safety.
If i was you when you get the new drive shaft i would see if it's possible to set up between centers in a Lathe with the hub in place to see if the hub flange runs true.
It's the easiest way to resurface the flange on the hub if needed. You will need to remove the drive pegs and after assemble with Loctite only on the pegs.
In the past when i had a problem like this the shaft had been wobbling around so much the brake disk had broken. Lots of vibration felt on the brake pedal :shock: .
For the use of Loctite i see no problem, there are bearing fit Loctites to do the job with no worry.
Alan
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PostPost by: JonB » Sun Jan 07, 2018 8:30 am

Thanks Alan.

Funny thing is, I had no vibration in the brakes. I did encounter steering wheel vibration at motorway speeds but I attributed this to a loose front wheel bearing. After I'd adjusted this, it went away, then it came back after I'd put the new front uprights in. Again, I adjusted the front bearings but this time the vibration persisted.

Of course, the rear clonking that started this adventure was there all along, and I'd noticed it was particularly bad if I drove the nearside rear wheel over a bump. I double checked the offside rear bearing, it's got no discernible play.

I'm considering one of these: https://paulmattysportscars.co.uk/produ ... aft-steel/

The description says "Quaife" which I guess is a good manufacturer.
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PostPost by: rgh0 » Sun Jan 07, 2018 11:33 am

There are various Loctite grades for use with fitting bearings. In general i would only use them as a permanent fix when the interference fit is still there but not as tight as it should be so it helps lock the bearing and stop it spinning. The grade such a "quickmetal" that you can use when the interference fit has gone totally and you have a clearance fit should really only be considered as a temporary fix IMHO.

The Loctite information on the net gives details of the recommended use.

If the axle is not correctly aligned in the strut housing then the brake disk and wheel will be misaligned also. Without an interference fit it is inevitable the axle will be misaligned to some degree as you cannot guarantee the Loctite will fill the gap evenly when you don't have an interference fit

cheers
Rohan
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PostPost by: JonB » Sun Jan 07, 2018 5:44 pm

Hi Rohan

I had considered the possibility of off-centre mounting, but I will not commit to replacing the carrier unless absolutely necessary. It is to be observed that it apparently worked with Loctite for what looks like many years, so I would expect to see many more years of service. Moreover, I have no evidence that the carrier is actually damaged. I could imagine this seating compound being used as a matter of course when putting in new bearings.

I could leave the layer of Loctite as-is and fit the new bearing with a smear of additional compound. As it is, I have no way to accurately measure the housing save the bearing fit, and there was definitely interference when I drifted the old one out, and that was with a good whack or two.

The old bearing is a little free running, but has no discernible play. It fits quite well on the remaining bit of ungrooved driveshaft. So I am wondering how the shaft became so badly grooved? I might expect this if the bearing had siezed, but it hasn't. Perhaps it was damaged by a previous bearing, not enough to be a concern, but enough for there to be a tiny amount of free play (allowing the axle to rattle about a little, leading to more damage). I'll never know. The bearing seals are both intact, and the inner race looks undamaged. Must be very hard steel indeed...
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PostPost by: rgh0 » Sun Jan 07, 2018 7:36 pm

To me it looks like a bodge repair. A previous bearing had siezed and worn both the carrier and shaft and some one has refitted with lots of Loctite :roll:

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PostPost by: alan.barker » Mon Jan 08, 2018 8:56 am

If it was my car i would leave the Loctite as is and wipe around with some acetone. Then fit new bearing with aditional Loctite. For sure DO NOT remove the old Loctite because you will make the fit worse.
For sure this is what i would do if it was MY car.
Alan
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PostPost by: JonB » Mon Jan 08, 2018 10:49 am

I've chosen Loctite 641 for the bearings and a new billet shaft from Spyder.

@Alan, the Loctite cures on contact with metal according to the documentation. Just a thought - maybe this would be inhibited if I leave the old stuff on there?
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PostPost by: alan.barker » Mon Jan 08, 2018 11:47 am

Hi Jon,
your bearing is in metal i hope :? so that should i think activate the Loctite.
I thought it was the absence of air that activates it.
When i was in the Aero Space Industry in my former life we used a special Loctite Primer also.
Maybe with the modern Loctites this is no longer required.
When you fit the outer bearing into the housing with the Circlip nicely in place i'm sure it will be ok.
You can leave it for a day before you assemble the Drive assembly with the inner bearing and Dustshield.
Make sure there are no burrs anywhere in the Circlip grooves so they will clip into place nicely.
When you assemble the Drive Shaft + inner bearing(the correct way round :wink: ) + NEW Dust Shield put pressure on the centre part of the bearing not the outer part.
Sorry if i am trying to tell you how to suck eggs
Alan
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PostPost by: JonB » Mon Jan 08, 2018 1:59 pm

Hmm, inner bearing "correct way round". It has a seal like an O ring which is biased towards one side of the outer race. Does that go toward the wheel or away from it?
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PostPost by: alan.barker » Mon Jan 08, 2018 3:21 pm

On the inner drive shaft bearing the large dia is narrower than the small dia.
Just double check fit dust shield then bearing correct way round before pressing onto shaft.
If you need to remove from shaft because it's wrong bearing gets damaged.
Alan
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PostPost by: JonB » Mon Jan 08, 2018 4:33 pm

Alan, I do not understand what you said, sorry. I kept the old bearing on the shaft as it is all tatered, so perhaps I should fit it like that? Only thing is, it may be wrong...

One other point about the dust cover / washer thing. The one Sue Miller supplied is thicker than the one already fitted to the old shaft. If I cannot get the outer circlip in I will be properly stuffed, no?
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PostPost by: alan.barker » Mon Jan 08, 2018 5:34 pm

Hi Jon sorry,
what i'm trying to say is the width of the bearing where it fits on the shaft is wider than the outside dia.
Maybe the inner race is about 3mm wider than the outer race. The extra width of the inner race needs to face the center of the chapman strut. I hope you can understand with my bad description.
For the dust shield perhaps you need to use the old one if you can. It would be a problem if you can't fit the Circlip.
The last thing you need is a problem to fit the Circlip.
Have you got a photo of old shaft with bearing in place.
Alan
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