ANTI ROLL BAR

[Lee Dutton]

I am considering fitting an anti roll bar to my 66 4a to improve the handling, and would be grateful for comments as to whether this is a worthwhile addition, if so

I would be pleased as to suggestions for sourcing or if there is one out there surplus to requirements.

Many thanks Lee

[Motorsport Mickey]

Do you need it ? Kastner raced his TR4as with no front bar and only a bar at the rear he said "Flat ain't fast"...I agree. 

If you must, fit 2 Lee, front and rear.

Manufacturers build cars with understeer as standard (it's safer if the car goes on straight rather than oversteering out), if you fit a front bar only your initial understeer will transform to UNDERSTEER (with knobs on).

Often owners on a TR4a will use a TR6 front bar and then someting like a Dolomite rear bar which gives a stab at making the handling more neutral. You alter the "lever" lengths of the horizontal arms of the Dolomite roll bar by either clamping the vertical link to it in a different place or drilling a hole in it's flat in a different position. Shorter arm length link to crossbar gives a stronger bar which at the rear means more balancing oversteer to the fronts understeer, hopefully approaching neutral.

Of course if you want grip you don't use ANY anti roll bars front OR rear,...like this

But you do have to equalise front and rear roll centres and have balanced soft springs to the maximised suspension and neutral bump steer. This is at Devils Elbow at Mallory Park which has a huge drop from outside to inside of the track, and the car above has just reached maximum inside wheel suspension droop even without anti roll bars. With them the wheel would be another 3 inches off the track waving to spectators, not good for grip.

Mick Richards  

Edited October 19, 2021 by Motorsport Mickey

[Hamish]

Lee i shall wait for Mick  to provide his advice on this one as don't have the experience with IRS cars.

but i think that you really need to be pushing it to get any advantage out of front and/or rear ARB's

 

edit

ha ha he is just quicker at typing than me !!!!

Edited October 19, 2021 by Hamish

[jerrytr5]

I wouldn't attempt to contradict Mick on race car suspension, but a road car needs to get over speedbumps and offer a semblance of a comfortable ride although Mick included soft springs in his set up, which is interesting.

The best handling mod I ever made to my 5 was to fit a rear anti-roll bar, but I already had a TR6 front bar fitted so as Mick says I was counteracting understeer. Maybe I should have tried disconnecting the front bar first but this was before the Forum.

Anyway, fitting anti-roll bars front & rear mean that you can use soft-ish, tall-ish springs so that in a straight line the ride is acceptable but roll is contained and speedbumps are not to be feared. I think in the end to get a good balance I ended up putting a thicker front bar on, so it is an iterative process.

Jerry

[john.r.davies]

Mickey,

This is a different way of controlling suspension, which I really don't understand, maybe you can explain?

"Zero Droop".     When I was at college, we were instructed to set up the Formula Ford for "zero droop" in front, while allowing 20-30mm of droop on the rear wheels.    I could never get our instructor to explain clearly why this was an advantage!      I caan see that under acceleration, zero droop might keep the fronts in tracton until they were both lifted off the ground, like a dragster.   But any cornering advantage is obscure to me.

JOhn

 

[Motorsport Mickey]

Not zero droop John..."maximum wheel suspension droop".

As you can see in the picture the inner wheel is in maximum droop allowed by the suspension. The set running clearance was 3" under chassis and we allowed the car full reign to use the suspension movements to the full without constraining them by anti roll bars. The roll centres front and rear were equalised and so the car didn't twist if the road surface was equal, but merely compressed the springs upon the outside, and the inner wheels were in full droop utilising the suspension movement to keep the tyres in contact with the road. Anti roll bars imparting extra stiffness across car impart excess weight transfer which cause the tyre footprint to deform, which reduces it's grip...and you understeer.

That's why you can crudley reduce understeer by pumping up the front tyres. the tyre carcass is stiffened and doesn't have as much tyre slip (not skid) where the wriggling of the carcass deforms the tyres road grip. Likewise a car which oversteers can be made to be more neutral by pumping up the rear tyres, and stiffening the tyres and retaining more grip. As you know however once you obtain the best handling from the suspension, and measure the tyre temperatures as being about the same across the tyre, you should stick with those tyre pressures. You can still increase or decrease the tyre poundages but that then changes your handling by making the grip worse at one end of the other, a case of one change making a change in two parametres...that never works out well.

Your Formulae Ford with Zero droop was controlling weight transfer front to rear, the 20-30 mm droop at the rear allowing the suspension to compress and with the tyre deformation gain maximum traction off the line and out of corners. The Formulae Ford has anti roll bars front and rear and so it's suspension works conventionally. 

Mick Richards      

[Lee Dutton]

Thanks for all the comments suggestions advice, very detailed description by Mick Richards sure we all learnt something thank you so much.

Not sure what to do now. this all started when I noticed one of the guys at the club had an anti roll bar fitted at the front of his 4a he told me it had improved the handling

by a lot however before going to the expense time etc. I thought it a good idea to get advice from members of the club and have learnt a lot maybe better to leave

well alone for the time being.

Thanks to all Lee 

[john.r.davies]

Just for comparison

 

 

 

Ken Miles

[Hamish]

lee drive that other car and see if you noticed a difference

of course if you both have the clubs A plan insurance you are both covered.

H

[Lee Dutton]

Cheers H good idea

 

regards Lee

[Lebro]

I found that fitting a front bar only certainly reduces roll, but when "pushing it" the understeer is a problem. Adding a rear bar improved things a great deal, allowing oversteer when required by applying more throttle.

I cannot comment how things are when pushing to the limit.

Bob

Edited October 20, 2021 by Lebro

[Motorsport Mickey]

2 hours ago, john.r.davies said:

Just for comparison

 

 

 

Ken Miles

That’s a good comparison John, you can see with the Cobra the track there is substantially flat. At that same point my TR 7 would have been almost level there with the inside wheel contributing to grip and steering.

Mick Richards

[Rockie51]

Jerry

By fitting an anti roll bar, you are increasing the single wheel spring rate. When the wheel hits a bump, it is compressing the spring at the wheel and also partially compressing the spring on the other side through the ARB, thus negating the effect of softer springs.It is only in pitch, ie when both wheels move at the same time, that the ARB has no effect. Following Mick’s philosophy, I fitted higher rate springs front and rear but no roll bars. Most of my driving has been on long trips with full tank, full luggage behind the seats, two people and a full boot, so the ride is very good despite the stronger springs. My favourite TR mechanic who is also a successful racer, described the handling as very good on his favourite winding test road.

Lee, I would check that the springs and bushes on your car are in good condition before trying an ARB.

[john.r.davies]

The Cobra pic just struck me as it was almost the same angle from the camera and depth into the corner.   But I think that the suspension situation is bit different, as Miles is drifting it, with power to lose rear traction and  induce oversteer, with some correcting opposite lock.

Definitely near the limit, Bob!

[Motorsport Mickey]

I think that corner for the Cobra has a resemblance to the downhill section at Oulton Park before the Caurosel.

Mick Richards

[john.r.davies]

Do you mean Cascades, Mickey?  The Shell Hairpin has a dead leval approach.

Ken Miles raced Cobras exclusively in the US.  His career with that particular car is detailed here:  https://www.shelbyamericancollection.org/cobras-coupes/1964-usrrc-cobra-roadster-csx2431

The pic could be several courses - I don't know any of them!

John

[Motorsport Mickey]

Thanks John...yes Cascades was the name I couldn't quite recall.

Mick Richards

 

 

[Andy Moltu]

Some of it is about how you drive and the feel of the car.

I have driven the 6 with and without its rear anti-roll bar and much prefer it with it. Had a brief spell without it after one of the clamps was damaged so removed it whilst awaiting some new bushes.  Less understeer. It has a front one as standard.

The 4A had already got a front one when I bought it and certainly more understeer of the two but also on different tyres so not an exact comparison although the springs and bushing set up is very similar.

Make sure the ball joints, trunnions and bushes are in ip top order before adding further to the suspension as judgement of what it feels like to drive may not be valid if, for example the trunnion bushes are shot and the wishbone bushes soggy.

[TR4Tony VC]

Hi all

Just to add to the mix, the works TR4’s didn’t run any anti roll bars and having rallied 3VC quite and enjoyed its fabulous handling, it seems clear to me that it’s not needed. The front suspension is basically the same.

By comparison, I’ve tried front anti roll bars between 1inch and 9/16th inch on my other TR4 and with the fattest front tyres and the ‘stickiest’ set up, the 9/16th gives slightly better precision in steering when really cornering hard - so long as the rear is loose and baggy and can slide round. Understeer is worse, but with a compliant rear end it can be managed.

Im sure that others will disagree, but I don’t think ARB’s on a road car will help you.

If you’re track racing I’m told that matching / balanced ARB’s do work but a lot of tuning needed, especially on the rear and very much linked to spring and shock rates.

Regards

Tony

[Ocheye]

I removed the front ARB that was fitted to my 62 TR4 and, wow, what a difference. I don't hit speed humps any more!

TBH I changed to a larger circumference tyre at the same time and also changed the geometry back to standard. I have no handling issues to report now and have felt no need to restore the front ARB.

I now have an ARB in my garage that I do not require if anyone is interested. It will need some work to the drop links (if that is the correct term) and probably new rubbers.

Andy

[Drewmotty]

Lots of racers don't use anti roll bars or sometimes just a rear to allow easy adjustment of the balance but they also tend to use much stiffer springs which may bring the roll rate close to that of a road car with softer springs and anti roll bars which will soak up the bumps better in a straight line.

17 minutes ago, Ocheye said:

I now have an ARB in my garage that I do not require if anyone is interested. It will need some work to the drop links (if that is the correct term) and probably new rubbers.

 What size is your ARB Andy?

[Ocheye]

I think it is 11/16" or approx 17mm. Sorry no caliper to hand so can't be 100% accurate

Andy

Edited November 24, 2021 by Ocheye

[Peter Cobbold]

The difference between Mick's 7 and the 4A is the semi-trailing arm on the 4A. Unlike the 7's axle the TAs go through a range of  toe angles, form toe-out when the spring is compressed to toe-out when at full droop. These toe changes, along with camber changes that are somewhat negated by chassis roll, leads to uncertain rear grip. The only answer (short of converting to a solid-axle 4) is to stiffen the  rear springs and add a rar, and then to maintian front-rear roll stiffness stiffen the front too. On a smooth surface the handling is improved, but hit a bump in the road and the road-holding and ride suffer badly. The trailing arm is not really a race-worthy design. Peter

[peejay4A]

With front and rear arb on Eric, and lowered a touch, I can resonate to the above. On a decent road surface I like the handling but a few days on the NC500 got a bit choppy. 

Edited November 24, 2021 by peejay4A
lowered too

[Peter Cobbold]

4 hours ago, Peter Cobbold said:

The difference between Mick's 7 and the 4A is the semi-trailing arm on the 4A. Unlike the 7's axle the TAs go through a range of  toe angles, form toe-out when the spring is compressed to toe-out when at full droop. These toe changes, along with camber changes that are somewhat negated by chassis roll, leads to uncertain rear grip. The only answer (short of converting to a solid-axle 4) is to stiffen the  rear springs and add a rar, and then to maintian front-rear roll stiffness stiffen the front too. On a smooth surface the handling is improved, but hit a bump in the road and the road-holding and ride suffer badly. The trailing arm is not really a race-worthy design. Peter

correction: toe-IN when spring is compressed.

Semitrailing arm geometry principles here, based on a BMW:    http://www.e30sport.net/tech_articles/susp-tech/rear_curves/page-3.htm

Dont know of calcs for the IRS TRs, but it is clear that camber and toe wander around unless the suspension is made very stiff, and lowered to bring t/a to near horizontal.

 

Peter