TR5 rear trailing arm lateral location

[DenisMc]

Hi All,

I have just given my TR5 a service and a check over underneath whilst it was over a friend's pit. Last year I replaced the rear trailing arm bushes with blue poly bushes that I bought from Rimmer Bros. Their part number is 137599PBB. Before I pressed them into the arms I phoned the manufacturer, Polybush, to ascertain which way round the bushes should be fitted. I was told to fit them so that the conical ends faced each other. 

Looking under the car today I noticed that both training arms had shifted inwards on the bushes, presumably due to lateral cornering forces. In fact, they had shifted far enough for the face of the training arms to almost contact the inner face of the mounting brackets. Using a piece of wood and levering against the chassis it took very little force to re-centre them, but obviously they won't stay there. There are shoulders on the bushes but they are not large enough in diameter to stop the arm sliding over them.  

Is this normal?

I am concerned about the arms contacting the brackets and the effect on the rear wheel alignment.

Your advice would be most gratefully received!

Thanks,

Denis

Edited April 9, 2023 by DenisMc

[BlueTR3A-5EKT]

This sort of thing?  Your problem sounds like the wrong bush was used/supplied.

 

 

https://www.superproeurope.com/products.cfm?vehicleid=3886

[DenisMc]

Hi Peter,

Thanks for your quick response. If you go to the Rimmer Bros website and look up the poly bush 1375099PBB you will see that it is much the same as you have shown in your photo. The only apparent difference is that the Superpro bushes have the conical form on both ends. So, changing to the Superpro bushes might not make any difference, unless the outside diameter of the shoulders is larger...

Denis

Edited April 7, 2023 by DenisMc
Typo

[DenisMc]

An update.

I have just got back from a lovely drive out and sure enough both trailing arms have now shifted inward, towards the centre of the car. I'm wondering if the toe in is excessive and that is causing the wheels to turn inward, taking the arms with them. This make sense as when the car was restored in 2001 split trailing arm bushes were fitted that had large diameter flanges on them that would have constrained the arm to be equi-spaced within the mounting brackets. I'll see if I can find a DIY method to check the toe in. If anyone knows of a method I'd be pleased to hear about it.

Denis

Edited April 7, 2023 by DenisMc

[harrytr5]

You will need to remove trailing arms and replace the bushes with the correct items pronto.

They can be a bugger to press in and will not shift about like the ones that have been fitted.

Just change them.

Regards Harry

[DenisMc]

Thanks Harry,

However, I don't really see any visual difference between the Polybush Ltd bushes that I fitted and the Superpro bushes recommended here....I believe that the Polybush Ltd bushes are the correct items. I had a heck of a job drawing them into the bores in the arms.

I am going to check out the toe in first as I don't believe that it was set after the car was restored. Note that a new CTM chassis was fitted and there are exactly the same number of shims under each off the brackets. 

Denis

[Kenrow]

Besides the chamfer, is each end of the bushing the same diameter? What is that diameter?

[DenisMc]

Hi Ken,

I believe from memory that each end of the bush was the same size, I don't have a spare bush so can't say what the diameter is. I have just done a rough check on the toe in of the right hand rear wheel. I found a method of doing this using a string line. Measuring at the wheel rim I get a difference in the front and rear measurements of 8mm. It is supposed to be zero to 1/32" or zero to 0.79mm, so it is toeing in way too much. Before changing the bushes I am going to correct this to see if it overcomes the problem.

Denis

[Waldi]

Hi Denis,

I measured the toe-in and camber from front- and rear wheels with a laser straight-edge. And then corrected the wheels and measured again; it was a bit of an iterative process, and took me a couple of days (I like this sort of exercise, so did not bother about the time I spent). When it was later measured in a prof. shop for belts and braces my measurements appeared to be very close and no additional corrections were needed. It took me several measurements swapping from left to right and vice versa because I have only one laser.

Theoretically, the sliding of the TA over the bushes should not affect toe-in. I have “cheaper” PU bushes too, front and rear and regret I did not spend the extra cash for the ones recommended on this forum. Mine slided in relatively easy (too easy?). So I wonder what happens under load.

In your case, I would replace the 4 TA bushes by Superpro (or the other marque recommended on this forum) first, then measure and correct toe-in and camber as needed.

It would be interesting to hear it you find differences between the old and new bushes, if you decide to go that route.

The original rubber bushes had no shoulder and did not need these: these were fixed because they were vulcanised to the pins.

Another thought:
It makes sense to me to fit the bushes “face to face” (or is it “opposite orientation”) so they are fixed against axial movement in both directions, like you did. Maybe the shoulder on your bushes is too small?

Good luck,
Waldi

 

[harrytr5]

Something does not add up here. I have installed plenty of Superpro bushes supplied by the likes of Moss and never had a problem with them. I have no experience of the rimmers ones so can not comment.

Good luck and hopefully get back here when you have found the problem.

Four wheel tracking is the way to go and I use and trust my guys in Hemel Hempstead. Discount Tyre Services.

Regards Harry

[Bfg]

17 hours ago, DenisMc said:

I'll see if I can find a DIY method to check the toe in. If anyone knows of a method I'd be pleased to hear about it.

For wheel tracking (checking and correcting toe-in) I use a piece of fine cord, taut around the four tyres (using 1/4" wood packers under the string on each side to correct the 1/2" difference in front and rear tracking of the TR4A)  and then measure from that to the wheel's rim < here >  It's a convenient method and accurate enough to measure (..if I'm wearing my reading glasses !) 

For the wheels camber angle I use a spirit level (positioned vertical against the wheel arch flare) and then measure from that straight edge to to wheel's rim < here > 

My own car's trailing-arm polybushes are red ones (branded 'polybush') which are not split in two parts like yours. I replaced a cracked trailing-arm casting but reused the bushes, from the old arm, in its (also used) replacement.  Even the one-piece polybush pulled in easily enough, and then the steel spacer tube was inserted < here >.  The polybushes have a flange at either end and the arms do not slip sideways on them. 

Hope that helps,

Pete

 

Edited April 8, 2023 by Bfg

[DenisMc]

23 hours ago, Bfg said:

For wheel tracking (checking and correcting toe-in) I use a piece of fine cord, taut around the four tyres (using 1/4" wood packers under the string on each side to correct the 1/2" difference in front and rear tracking of the TR4A)  and then measure from that to the wheel's rim < here >  It's a convenient method and accurate enough to measure (..if I'm wearing my reading glasses !) 

For the wheels camber angle I use a spirit level (positioned vertical against the wheel arch flare) and then measure from that straight edge to to wheel's rim < here > 

My own car's trailing-arm polybushes are red ones (branded 'polybush') which are not split in two parts like yours. I replaced a cracked trailing-arm casting but reused the bushes, from the old arm, in its (also used) replacement.  Even the one-piece polybush pulled in easily enough, and then the steel spacer tube was inserted < here >.  The polybushes have a flange at either end and the arms do not slip sideways on them. 

Hope that helps,

Pete

 

Thank you all for your most useful contributions. Pete, my blue Polybush branded bushes are not split in two, they are one piece like your red version. The difference is that the red ones are a harder competition bush. They are probably dimensionally identical. As mentioned, I have checked the rear toe in using the string line method suggested by Pete and others and both sides are miles out. I am going to correct this first to see if it has any influence on the shifting of the trailing arms as increasing the  amount of toe in increases the tyre lateral force. If it doesn’t then unfortunately I’ll have to do the job all over again using the Superpro bushes that have been recommended. The only good news is that they are on special offer from Moss right now! 

Edited April 9, 2023 by DenisMc

[Bfg]

[DenisMc]

Hi All. When I installed the Polybush bushes I used lots of the Superpro grease that is supplied with those bushes. I guess I should have looked before but have now found the Polybush installation instructions:

https://www.polybush.co.uk/polyurethane-suspension-bushes-components-fitting-instructions/

You will see that they recommend not using grease but soap and water that will dry out leaving the bushes held firmly in place. As mentioned above it took very little force to re-centre the arms in the mounting brackets so clearly there is still grease present. Could this be the cause of my issue? 

I drew the bushes into the arm using a hand press made up of a socket, a length of studding, nuts and washers. If I remove the road spring and the pivot bolts is it physically possible to lower the front of the arm on the car, push out the bushes, clean the grease off and reinstall them as per the Polybush instructions? I have the use of a pit to do this. I am still going to correct the toe in first. 
Thanks

 

Edited April 9, 2023 by DenisMc
Typo

[Waldi]

Hi Denis,

That’s a good finding; I hope this is the cause (but not sure).

I think if you support the TA after the spring, it should be possible to remove the brackets. Be careful with the brake pipe though.

Waldi

 

[DenisMc]

Thanks Waldi. I'll give it a try, carefully! I am going to phone Polybush on Tuesday to find out if they concur with my thoughts. 

Denis

[Bfg]

On 4/9/2023 at 8:45 AM, DenisMc said:

If I remove the road spring and the pivot bolts is it physically possible to lower the front of the arm on the car, push out the bushes, clean the grease off and reinstall them as per the Polybush instructions? I have the use of a pit to do this. I am still going to correct the toe in first. 

Yes.

Last month I replaced one of the trailing arm's notched brackets ..to correct the camber on one rear wheel of my 4A, and at the same time remove a shim on that one side to correct its tracking. I did it without removing the spring, hub, brake, etc. < here >.

I just needed to substitute the one bracket, and so although I slackened off the other bracket's through-the-chassis-rail bolts - the trailing arm was still attached and the trailing arm was safe from twisting on its support block, or otherwise naughtily falling off that block altogether with an almighty bong under influence of the spring's compression.  The front pivot of that side of the arm had to be pulled down / dropped low enough to extract the bracket's through-bolts and so it would have been possible to also have removed the polybush.  Do one side at a time (with the other pivot bracket holding the arm secure) and you should be OK.  However...

..because it is so easy to release the damper's drop arm link and to lower the rear end of the trailing-arm on a trolley jack, and then to remove the spring - if I were wanting to take the bushes out, even just to clean them - I would do just as you suggest.  It's the safer option and even with the drive shaft, hub and brake left in place / undisturbed (but do support the hub to prevent the arm lowering too far and the half-shaft pulling apart at its spline) - it would give you appreciably better access to the pivot bushes for your task. 

Correct your toe-in first ..and then also check the rear wheels camber (with the car loaded to simulate driver & passenger weight) otherwise you may be under there again to correct those.   

Hope that helps.  

Pete

 

Edited April 12, 2023 by Bfg

[DenisMc]

Hi Pete, thanks for your useful reply. An update. I phoned Polybush and they told me that I shouldn't have used the Superpro grease. They recommend using water and washing up liquid as it will dry out and a good grip will then be created between the bushes and the arm bores. Today I got the car over a pit and to my horror the righthand arm was starting to rub against the inner face of the mounting brackets! I centred the arms on the bushes and then removed two shims from the righthand inner mounting and one shim from the same mounting point on the lefthand side. I then checked the toe in using the string line method. Both wheels were still toeing in with the difference in the measurement to the wheel rim being 2mm on the righthand side (was originally 8mm) and 3mm on the lefthand side. There is obviously a little way to go on this as it should be 0-0.8mm. After a run out I was pleased to find that the righthand arm had remained largely central in its brackets whereas the lefthand bracket had shifted inward a little. 

I have had to move to other things but when I get a chance will try removing further shims. Whilst I was under the car I measured the shoulder diameter of the Polybush bushes. I got this to about 38.8mm at the non conical end. Does anyone know what the shoulder diameter of the Superpro bushes is? 

Regards,

Denis

 

[DenisMc]

Hi All. 
I have now corrected the toe in the best I can using the string line method. I ended up with 3 outer bracket shims and one inner bracket shim on both sides. I’ll arrange to get a four wheel alignment check done in due course. After a run out the trailing arms are fairly central in their brackets. I am going monitor this for a while before taking any further action.  Superpro helpfully informed me that the diameter of the shoulders on their bushes is nominally 40mm so potentially very slightly larger than the 38.8mm that I measured for the Polybush bushes. 
Denis

[Bfg]

Well done Denis. That's a good result. 

Have you check / are you happy with the rear wheels camber angles. ?  I use plywood pads on one side (due to a very slight incline in the patio slabs where I park) to level the ground, and then load the seats with night storage heater bricks to the prescribed weight and rolled the car forward to its parking spot (two wheels on ply pads), and then use a spirit-level, set vertical, to measure to the rims ..in the same way as when measuring to the string.  I guess a plumb line would work instead of the spirit level.  My car's wheels were a tad positive (leaning out) on the LHS rear and similarly on the LHS front wheel.  Changing one trailing arm bracket corrected the rear, and shimming under the front suspension bottom wishbone brackets mostly sorted out the front.  

Pete

[DenisMc]

Hi Pete,

Thanks for your reply. I should mention that I set the toe in with the car unladen as I don't have a ready means of loading it. Do you know if this would make much difference? It was clearly well out as the rear tyres are both scrubbed on the outside. I have now checked the rear camber with the car unladen on my flat and level garage floor. I measured horizontally from a builder's spirit level, resting against the centre of the hub cap and held vertically, to the upper and lower wheel rim. The difference in the measurements were approximately, RHS 13mm and LHS 8mm, with the camber negative. Assuming that the diameter of the wheel rim is 405mm, then using the Sine function this gives the camber as negative 1.82 degrees and 1.13 degrees respectively. Is this useful information?

Denis

Edited April 20, 2023 by DenisMc
typo

[Andy Moltu]

Should the trailing arm brackets not constrain the bushes and the stainless inserts. 

When the through bolts are tightened there should be no scope for lateral movement as the bolt clamps onto the stainless insert.

If the bushes are able to move, either the through bolt is loose or they are the wrong bushes.

If you think polybushes are tricky to fit, you should try and get hold of a set of the old uprated rubber ones. Unsurprisingly they have fallen out of use!

[stuart]

1 hour ago, Andy Moltu said:

If you think polybushes are tricky to fit, you should try and get hold of a set of the old uprated rubber ones. Unsurprisingly they have fallen out of use!

Not with good prep and a large press theyre not difficult.

Stuart.

[Andy Moltu]

I'm referring to the ones of 25+ years ago. 

Apparently there were reports of trailing arms being broken trying to fit them.

I got a local engineering shop to do mine. I don't give in easily and they had a struggle.

Fitting poly bushes is straightforward - easier than the chappy "original/standard" ones.

 

[DenisMc]

Hi Andy M,

Thanks for your reply. If you read from the start of this thread you will see that my issue was nothing to do with the poly bushes moving in the brackets. As you state when the through bolts are tightened up the stainless steel tubes are clamped hard against the inner faces of the brackets. My issue was with the arms moving laterally inward on the bushes themselves. 

Having corrected the rear toe-in, which was way more than it should have been, I shall now be monitoring the situation on the next few drive outs. I did consider changing the Polybush bushes that I fitted to the Superpro bushes recommended here. However, I am not convinced that they would be any better, with regard to the arms sliding on them.

Time will tell...

Denis