Rear trailing arm adjustable brackets

[Kevin76]

Hi,

 

I am gradually getting my 1976 TR6 in shape and one of the last things to tackle is ( what looks like to me) excessive negative camber on the rear wheels. They are not cambered the same either.

 

I have read about shims and shimming combinations and was going to get into that when I saw in one of my catalogs that a company offers an adjustable rear training arm bracket. It sounds good in the blurb, but it is pretty pricey so I was wondering if anyone has used them and if they work before I plunk down the money.

 

I do plan on re-bushing the rear trailing arms and possibly new springs too.

 

Thanks, Kevin

[RogerH]

Hi Kevin,

the adjustables have a fan club who think they are very good. I still like the idea of the fixed units.

 

Somewhere within the forum there is a table of bracket combination (1, 2 & 3 notch, inner/outer) that will give you virtually anything you like.

But, I can;t find the table.

 

 

Roger

[jerrytr5]

They seem to evoke a bit of a marmite response - love 'em or hate 'em.

Original brackets have been known to fracture (one of mine did) so you might want to consider replacing all of them which might make the monetary outlay easier to justify.

Adjustable brackets will save you hours setting up the rear geometry, otherwise with fixed brackets you need to swap them round to achieve the same end. And if you change springs or ride height you will need to go through the same painful process again.

Unless you are an originality pedant, can't really think of any reasons not to use the adjustables.

Roger's mad - ignore him.

Jerry

[RogerH]

I'm not mad - just a little quirky

 

Have a look at this article - it may prove my sanity

 

http://www.buckeyetriumphs.org/technical/Suspension/AdjRS/AdjRS.htm

 

Roger

[Peter Cobbold]

Sort the springs first then the brackets. Tired springs, or wrong/unequal rates, or lost rubber seating shims can affect camber markedly.

If the springs are know to be the correct rate/ride height you can reduce neg camber with a polyproylene shim:

see Roger's link.

 

Peter

[Tony Millward]

I'm not mad - just a little quirky

 

Have a look at this article - it may prove my sanity

 

http://www.buckeyetriumphs.org/technical/Suspension/AdjRS/AdjRS.htm

 

Roger

 

If that doesn't convince you to use adjustable brackets then nothing will, saves heaps of time. I totally recommend them.

 

Cheers

 

Tony

[peejay4A]

I recommend them too. Didn't Kastner use them or something like them on his TR6? You still need to shim them to adjust the rear toe in but camber adjustment is easy.

[Peter Cobbold]

I'm wary of the longevity fo adjustable rbackets. They are are slotted vertically to allow the pin to be moved up and down.

 

I had a standard bracket fail with vertical cracks within mm or so of those slots, but in the same up-down direction as the slot long axis. The reason was a side-impact collision impact on the opposite sdie of the car that allowed a crack to start and propagate for a year or so until failure, of both arms of the bracket.

To my amateur eye the adjustment slot look to be in just the wrong place: cornering forces will tend to bend the bracket in and out horizonatlly, through the pin, and there's not a lot of solid steel above that slot to resist. Fine for race cars that never get dirty and are inspected regularly , and are lightweight. But a crack there is difficult to spot after muck has built up.

I missed the cracks - but wont again!!

Peter

[Guest ntc]

I refuse to fit them,not safe imho.

[Peter Cobbold]

When mine n/s bracket let go - it was the inner bracket - the wheel ended up at a ddrunken angle inside the wheel arch, tyre rubbing on it. Luckily it was a sharp left-hand low-speed turn.

No other damage. But a warning not to ignore anything that holds the wheels on on older cars.

Peter

[Tom Boyd]

Nothing wrong with them, fitted dozens!!!!

 

Why are they not safe?? I assume you have fitted them to your car and experienced problems Neil??????

 

Tom

[Guest ntc]

And there is a reason you have fitted them Tom ? yes I have seen the head on the main bolt knackerd indeed it was a mot fail.Not my car

Edited July 1, 2014 by ntc

[TRseks]

I just fitted adjustable brackets after fitting new slightly lower springs, the camber was far out even with the old springs so they had to be adjusted anyway. The steel that was used on the adjustable brackets was thicker then on the original brackets so looks very solid. The steel sleeve inside the bushings lock into the brackets when they are tightened just like on the original brackets so can't really see any problem with safety?

 

And it is really so much easier to adjust camber, done in minutes rather than possible many hours.

 

I did look at the webpage where all the calculations were done using standard brackets but I could not really see myself on my back under the car for many more hours trying different brackets that also would need to be bought after already spending weeks with rebuilding the suspension, brakes etc etc

Edited July 1, 2014 by TRseks

[Guest ntc]

Round bolt = round hole simples.This is a high stress point.

[Nick Hedges]

I really can't see any issues with these adjustable brackets, although I have no experience of them myself, from what I have seen they appear to be well engineered and I would certainly consider them. most modern vehicle with independent rear suspension units have adjustable toe/camber ect using an elongated hole with an eccentric washer fitted to the bolt head. IMHO if these parts are engineered properly the round bolt/round hole argument is not necessarily correct.

[Peter Cobbold]

Modern suspension designs have the benefit of computerised FEA. I doubt that the after-market brackets have been through similar stressing.

 

The slot looks to me to weaken the bracket. The bolt head only clamps the inner side of the slot over about one quarter of its diameter, half the bolt head area is clamping air in the slot, and the outer quarter of the bolt head clamps a steel strip that is separated from the bracket/chassis bolts by air.

There are just two bolt heads ( or nuts) resisting all the lateral forces during hard cornering, axially along the bolt.

 

The bolt in the outer bracket will be levered outwards as the trailing arm pivots on the inner bracket, best visualised in this photo:

http://4.bp.blogspot.com/-R_HXXj6Fwlg/TgAAr3fIpDI/AAAAAAAAAQQ/chKZPTXLLbY/s1600/DSCN0201.JPG

(visualise pushing inwards where the hub fits)

The only material resisting that force is the outer strip of steel which is separated from the bracket body and chassis by air over most of its length. The inner bracket pin compresses against the bracket body, so that's less of a concern.

To me, that outer bracket just doesnt 'look right'. My guess is that's where issues will appear. At least its easy to see.

Peter

[RogerH]

Hi Folks,

I can see the arguments both ways. More interestingly has there been a failure of the adjustable item??

 

Roger

[Tony Millward]

I couldn't find any references to a failure anywhere Rodger and loads of these brackets have been sold. I can't understand people knocking their safety without any facts to substantiate their argument.

 

Cheers

 

Tony

[foster461]

I've had them on my TR6 for years. I had the front end and rear end aligned last week when I had some new tires fitted and the rear end has not moved since I had it checked the last time. There are a lot of these brackets in use over here and I have not heard of any failures. The one weak point in the design is the adjuster. It is not meant to move the TA under load from the spring, only to hold it in position while you clamp everything up with the pivot bolt. If adjustment is required the TA needs to be levered into position and then move the adjuster.

 

I used Richard G's poly TA bush kit that comes with metal tubes and shims that allow the interface to get clamped up pretty good. The brackets themselves are substantial.

 

Stan

[Peter Cobbold]

The force acting on that outer rear hub in a 0.75G turn is, for a 1000kg TR with 60/40 F/R weight distribution and 75% of the cornering force taken on the outer wheels is

400x 0.75 x 9.8 x 0.75 = 2205 Newtons. That's 495 lbs force acting on the hub. The lever effect in the trailing arm will increase that force on the outer bracket towards 700 lbs.

 

I look at it this way - would I hang a 700lbs mass off an engine crane - using that bracket as a link ? I dont think so.

 

To me its question of how many hard cornerings will it take before the slit disorts?

 

Peter

Edited July 2, 2014 by Peter Cobbold

[littlejim]

On the 4A I wasn't expecting the shims to affect camber noticably, just the toe in.

For camber Iwould have had to look at spring lengths, thickness of the pads the springs sit in etc.

Edited July 2, 2014 by littlejim

[peejay4A]

I got it wrong. They were fitted to Paul Newman's Group 44 TR6. I think that cornered quite hard.

[Peter Cobbold]

Yes but over a tiny mileage compared with road cars. They wont let go immediately or we'd know. "TR keeps falling on me 'ead"

[Tony Millward]

Yes but over a tiny mileage compared with road cars. They wont let go immediately or we'd know. "TR keeps falling on me 'ead"

 

Yes, but they haven't failed at all have they?. If you have information of one of these 'letting go', please share it with us Peter.

 

Tony

[TRseks]

The force acting on that outer rear hub in a 0.75G turn is, for a 1000kg TR with 60/40 F/R weight distribution and 75% of the cornering force taken on the outer wheels is

400x 0.75 x 9.8 x 0.75 = 2205 Newtons. That's 495 lbs force acting on the hub. The lever effect in the trailing arm will increase that force on the outer bracket towards 700 lbs.

 

I look at it this way - would I hang a 700lbs mass off an engine crane - using that bracket as a link ? I dont think so.

 

To me its question of how many hard cornerings will it take before the slit disorts?

 

Peter

 

Well, looking at the the brackets I installed on the car I think it is capable of such a load.

 

It would be interesting to see how much weight it would accept before it breaks, I would actually guess a lot more than 700 ibs, but as it is mounted in a harsh environment with water, rust, vibrations etc to cope with as well it has to...

Edited July 2, 2014 by TRseks