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RogerH

Back to Back Taper Bearings

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Hi Folks,

        the last couple of weeks I have been (unsuccessfully) playing with a TR4A diff.

The pinion bearings are quite big and are positioned back to back. They have a preload (18 inch.lbs) - not a lot.

 

My concern is with front  and rear hub bearings that have the same configuration.

Both have a apprx 0.004" play.  No preload.

 

The hubs use grease and the diff uses thick oil. 

Does the liquid lubrication of the diff allow for the preload.

 

Roger

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A should be IRS? Actual diff itself pretty much the same I think?

Roger, without digging into the SKF manual......

Best bearing life is reached with light to moderate preload. This ensures all rollers are in full contact with the races even when under load, this distributing load evenly.

Also preload minimises deflection (more pre-load less deflection, within the bearing loading limits), which is obviously important for gear mesh in this case. 

Preload also helps keep deflection low even as the bearings wear.

As used in front wheel bearings, as I understand it is a bit of a compromise to keep costs and maintenance skill requirements down. Because the inner races are a sliding fit on the stubs, they must be run loose to minimise the spin of the inner races and consequent wear to stubs. The better solution is shimmed spacer tunes and set to 0 - light preload as per early MGB. James Shackford sells kits for this.

Oil lube is always superior - but only if the installation allows it!

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Hi Nick,

         thanks for that. I'm nearly convinced but as I do not have an answer I shall go along it .

I may have a play with the front wheel bearings and put a few thou of preload and see what happens. He he he!!!

 

Roger

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31 minutes ago, RogerH said:

I may have a play with the front wheel bearings and put a few thou of preload and see what happens. He he he!!

If you do that without spacers it will spin on the stub axles and wear them rapidly.

https://www.ebay.co.uk/itm/Triumph-TR2-TR3-TR4-4A-TR5-250-TR6-Front-Wheel-Bearing-Anti-Knock-Off-Spacer-Kit/183404904328?hash=item2ab3c8bf88:g:DL8AAOSw-ctbhnKz:rk:10:pf:0

 

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2 hours ago, RogerH said:

Hi Nick,

         thanks for that. I'm nearly convinced but as I do not have an answer I shall go along it .

I may have a play with the front wheel bearings and put a few thou of preload and see what happens. He he he!!!

 

Roger

Hello Roger

                     Do as nick says and fit or make spacers to achieve 0,000 to 0.002"

I did Spitty 2 years ago it stops pad knock back and inners turning on stub axle.

I checked mine last winter after about 6/7000 miles and adjusted one by 0.002"

Roger 

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Ok.  I do recommend the spacer kits though.  Have them on the Vitesse and fitted them to my PI also.  I understand they are even more worthwhile on the TRs with their big wheels and dinky little Herald sized bearings...…  Plus it lets me eliminate the free-play in the front wheel bearings without fear or ruining the stub axles and prevents the annual argument with the MoT man who is young enough to think that no wheel bearings should have any free-play!

Nick

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4 hours ago, RogerH said:

Thank you Nick & Roger,

         I will leave well alone.

 

Roger

Hello Roger

                       When you have time and the inclination fit a set for above reasons.

I think the bearings on your TR4a are the bigger onesits the TR6,s that have the same as Spitty (and with a lorry engine at the front and add some 205 sticking tyres!!!!!) no wonder they are all paranoid about front wheel bearings!

Roger

ps I found it improved the brake pedal slightly as there is no knock back.

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Hi Roger,

   thanks for that. I have never had a noticeable brake pedal problem (clearly I am not trying hard enough).

Next time I strip the front end down I will investigate more closely.

 

Roger Roger 

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On 12/11/2018 at 9:11 PM, Nick Jones said:

 

As used in front wheel bearings, as I understand it is a bit of a compromise to keep costs and maintenance skill requirements down. Because the inner races are a sliding fit on the stubs, they must be run loose to minimise the spin of the inner races and consequent wear to stubs. The better solution is shimmed spacer tunes and set to 0 - light preload as per early MGB. James Shackford sells kits for this.

James doesn't sell the kits for the TR's....

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13 minutes ago, tr4tom said:

James doesn't sell the kits for the TR's....

Yes, I worked that out afterwards. Should have corrected to sat that TR Enterprises sell the TR kits........... He does the Vitesse/GT6/Big saloon ones. He did do Herald/Spitfire ones for a while but may have given up on those as I’m not sure how well they sold.

Roger, I presume that the potential issue with TR brakes is the same as that on the big saloons and mainly that manoeuvring at low speed, using lots of lock, causes the stub axles to flex a little which in turn makes the brake discs move and push the pads back a little, giving a long brake pedal next time you want the brakes, sometimes alarmingly so.  Worse on cars with big wheels and tyres, especially if the bearings are also a little slack.

Vitesse and GT6 have the same beefier bearing and bearing spacing as the saloons and are much less affected by the pad knock-back effect.

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Oooops!!  Just spotted this reply.

 

I have the standard bearing/axle set up on  my 4A and have never noticed knock back etc.

I find it hard that a 1" diameter lump of steel can flex enough to give any odd indications.

 

Roger

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36 minutes ago, RogerH said:

Oooops!!  Just spotted this reply.

 

I have the standard bearing/axle set up on  my 4A and have never noticed knock back etc.

I find it hard that a 1" diameter lump of steel can flex enough to give any odd indications.

 

Roger

Roger, I agree on the flexing, and blame knock-back, which I've sometimes had on the 6 after going in reverse, on the taper rollers needing a nip up. Peter

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Oh, they do flex. Doesn’t need to be much as considerably amplified by the diameter of the brakes disc.

However I would completely agree that the effect goes hand in hand with and serves to add to any effect from bearing slack.

The bearing spacers help twice by stiffening the stun axle and also allowing the bearings to be set a bit tighter without fear of them spinning on the stub.

My impression has always been that it was mainly cars with big, sticky tyres that suffered flex and then only when driven really hard (track) or manoeuvring with lots of lock applied.

Was certainly the case with my PI.

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Hi Nick,

             I will happily accept that a spacer tube would seriously help hold the bearings in a constant position and allow minimal play.

This would have a major effect on the disc play (stopping it) and thus knock back.

As for the stubby flexing - I'm not party to that one..  i will accept that all things will and can flex  - but to what degree.  Not for me.

 

But I do like the idea of the bearings not spinning.

 

Roger

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