Roll centres + Rubbish saloons

[greenamex2]

Is messing around with roll centers on some rubbish handling overweight saloon car (err like mine) really going to make any measurable difference?

I realise that on a finely tuned single seater it will but should put any effort into the subject on my piece of junk, or just concentrate on the easier stuff to fix.

Does have anybody have an example where they played with roll centres and nothing else and actually measured a change on the stopwatch?

Thanks for any input.

[Al Weyman]

Trouble is I guess Dennis is the centres are probably hard to change however on basically road modified cars. I did notice that by having to run my old Camaro on the lower original Diameter 15" rims and also having to raise it for the 4" required ground clearance putting the lower wishbones more level instead of at an angle it seemed to handle better than it did and that may well have been shifting roll centres on the front at least. I think on a road based car to is definitely possible to over lower the car and this can seriously effect handling and roll centres. I have noticed a lot of the quicker saloons in the CTRCC races are not seriously in the weeds.

[Goran Malmberg]

Originally Posted by Denis Bassom

Is messing around with roll centers on some rubbish handling overweight saloon car (err like mine) really going to make any measurable difference?

I realise that on a finely tuned single seater it will but should put any effort into the subject on my piece of junk, or just concentrate on the easier stuff to fix.

Does have anybody have an example where they played with roll centres and nothing else and actually measured a change on the stopwatch?

Thanks for any input.

We have had som delicate discussion on this forum about rollcentre. I have been studying the issue for a number of years and when brought up in a forum with a number of opinions I find it VERY difficult to come in with my opinion. I have been writing down what I think is the proper way of dealing with the Rc, and this is a 120 page A4 book.
What I am trying to say is that telling what to do with the Rc on your particular car is not easy explained. If the A-arm layout looks normal I should leave it alone. Maybe you should try to keep the lower wishbone near parallell to ground.
In my eyes, a very refined A-arm layout is only worthwhile together with a chassis constructed form a clean sheet of paper, as the A-arm layout is totally dependent on Cgh location, weight distribution and a few other parameters.
Springs, shocks and swaybars together with allignment pays of better in lap times in your case.
Regards
Goran malmberg

[phoenix]

IMHO I think it is good idea to at least know at what height your front and rear roll centres are, for a couple of reasons.

The first is so that you can have an idea where the roll axis runs and so can understand what is happening to the chassis in roll.

The second is so you can make some reasonable changes in the right direction if you don't like what you have.

For example:

Lowering a standard saloon car and making no other changes can often damage the camber correction that was designed into the suspension (which probably wasn't enough for racing purpose in the first place) and, depending on the design of the suspension, will often cause the roll centre to be lowered at the same time, which can lead to more body roll which will requires an increase in camber recovery, not less.

If the car has a live axle the negative effects on roll resistance and camber recovery will commonly be larger at the front than the rear, so the balance of the car can be changed considerably from the original - and not often for the better!

It may be determined that the front roll centre needs to be moved back closer to it's original position (before lowering) by some further engineering.

Without knowing where it was, and where it has moved to after lowering, the right corrections cannot easily be arrived at.

[Al Weyman]

I know a tweek on the old Mustang and any racing in a series where they must use the original suspension mounting points/positions will undoubtably be illegal (and I bet there are a few out there :-)) was to relocate the upper wish bone/suspension member point an inch lower. This effects the roll centre I believe and apparently gives a marked improvent. It is also possible to do this trick with the old camaros but it is very difficult as they do not hang the suspension off the fletch panels like the Mustang and the mod would be very easy(ish) to spot.

[greenamex2]

Originally Posted by Al Weyman

I know a tweek on the old Mustang and any racing in a series where they must use the original suspension mounting points/positions will undoubtably be illegal (and I bet there are a few out there :-)) was to relocate the upper wish bone/suspension member point an inch lower. This effects the roll centre I believe and apparently gives a marked improvent. It is also possible to do this trick with the old camaros but it is very difficult as they do not hang the suspension off the fletch panels like the Mustang and the mod would be very easy(ish) to spot.

This mod would also improve the camber curve, so was it the roll centre change, the improved camber control or both that made the improvement?

I think Goran is probably right. Get the basics right first then progress to the fine tuning.

My problem is there would be no point emulating the original Corolla geometry, it was rubbish.

Perhaps I need to find something else to move towards.

Any recommendations on a good handling front engined, RWD, macpherson strut front, five link rear cars?

[zac510]

What chassis Corolla is it?

[greenamex2]

Originally Posted by zac510

What chassis Corolla is it?

AE86

Fantastic for drifting and rallying, not much good at going round corners properly!

The problem is next year I am up against cars that weigh less, produce the same power, produce more torque AND go round corners better. I am trying to even the odds a bit with some clever (but legal) suspension reworking.

[phoenix]

Originally Posted by Denis Bassom

I am trying to even the odds a bit with some clever (but legal) suspension reworking.

At the front, do the regs allow you to move the inner pickup(s) on the chassis of the lower tca (or wishbone)? Do the regs allow you to have a re-designed lower tca (or wishbone)?

[greenamex2]

"Pick up points must be retained although not necessarily used. Otherwise suspension is unrestricted"

I can also change my rear axle for one from "any manufacturer"

A lot of scope for flexibility.

And expenditure.

I need the biggest gain for the least expenditure of cash, but expenditure of effort isn't an issue.

The issue with the car at present is oversteer. Anytime anyplace anywhere and you don't need to touch the throttle to induce it.

[phoenix]

Originally Posted by Denis Bassom

"Pick up points must be retained although not necessarily used. Otherwise suspension is unrestricted"

I can also change my rear axle for one from "any manufacturer"

A lot of scope for flexibility.

And expenditure.

I need the biggest gain for the least expenditure of cash, but expenditure of effort isn't an issue.

The issue with the car at present is oversteer. Anytime anyplace anywhere and you don't need to touch the throttle to induce it.

Sounds like the front is working well enough.

From memory, doesn't the car have an LSD as standard? Is it working? Or could it be jammed solid? Or could any of the 5 link pivots have become partially seized?

[Notso Swift]

Originally Posted by Denis Bassom

Any recommendations on a good handling front engined, RWD, macpherson strut front, five link rear cars?

Well, there is the Escort and there is your Corolla....

Why don't you put a 3SGE into it? Will not handle much better but a crap load more power

Check out the Toymods forum sort through the drift and street stuff and there are some genuine racers there.

We have a few Sprinters (AE86's) in IPRA in Aus and I can tell you, as they drive away from me (with 300 bhp/ton) they don't appear to have terminal oversteer problems! I know there is a mod to lower the car withou moving the front roll centre too much, as this is an issue effecting handling balance.
Try Bill Sherwood's page - billzilla.org I think he details it. He doesn't race an AE86, it is his road car, but he does race so he doesn't think "slamming" a car is all you need to do!

Justin McClintock and Chris OShannassy (sp) are to names you should google, both run lightning AE86's, but I am not sure if they have sites

[johnny yuma]

Do you have the fattest front ARB you can fit-helps stop oversteer.
Are the rear springs too hard-this creates oversteer.
Are any new rear axle location arms "binding"in conjunction with other arms? This can create oversteer by locking the rear spring rate.
If you have a rear ARB take it off.
Is it legal to have larger wheels/tyres on the rear COMPARED to the front?
small as possible DIAMETER wheels/tyres can lower car without upset front geometry as much.
Run higher rear tyre pressures.

[Notso Swift]

Coming back to this, since the AE86 was the benchmark group A U1600cc car I am sure that it can be made to handle, maybe you can adapt a Watts link at the back?

[zac510]

Originally Posted by Notso Swift

Check out the Toymods forum sort through the drift and street stuff and there are some genuine racers there.

We have a few Sprinters (AE86's) in IPRA in Aus and I can tell you, as they drive away from me (with 300 bhp/ton) they don't appear to have terminal oversteer problems! I know there is a mod to lower the car withou moving the front roll centre too much, as this is an issue effecting handling balance.

I think be careful with the Aus information. Didn't the Aus-spec Sprinter come with a live axle rear end as opposed to the 5-link Denis has?

[greenamex2]

Originally Posted by Notso Swift

Coming back to this, since the AE86 was the benchmark group A U1600cc car I am sure that it can be made to handle, maybe you can adapt a Watts link at the back?

Yes it was, but that was only because of what it was racing against. Mostly 1600cc Escort RS1600i's of a similar weight.

I will be up against 2100cc Pug 205's that are 100KG lighter.

[zac510]

Sorry I take back my previous post, for some reason I was thinking the Aus AE86 was leaf sprung. My bad!

[glenn22481]

Originally Posted by phoenix

The first is so that you can have an idea where the roll axis runs and so can understand what is happening to the chassis in roll.

Does it really matter what the chassis is doing? Knowing what tyres are doing is more important...

Originally Posted by phoenix

Without knowing where it was, and where it has moved to after lowering, the right corrections cannot easily be arrived at.

so true.....

You say it oversteers everywhere, bit strange as normally it would be better somewhere and bad everywhere else, do you have another problem that more rear toe-in, softer shock/arb settings, LOWER tyre PSI, or perhaps dialing out some grip at the front couldnt sort out? Sounds like a balancing issue.

Have you actually removed the springs/shocks and gone through the various degress of bump/droop/roll at a static ride height with center line and reference strings etc and gauges or whatever means you have? - are you really at a time when you feel the need to alter the RC's... I know i'm stating the obvious but Ive had some shockingly bad handling issues in my car that a small tweak of a shock setting and an extra deg of wing sorted it out after a long time of going getting nowhere and wasting time cutting and fabricating parts that just dont work..

If you do alter the RC you will be spending alot of time measuring anyway, so you might as well do it now. Like Phoenix says you need to base/compare results against the previous setting.

[phoenix]

Originally Posted by glenn22481

Does it really matter what the chassis is doing? Knowing what tyres are doing is more important...

Yes it does - the tyres do not decide the weight transfer of the car in roll - but they have to deal with the consequences, if they can.

[Notso Swift]

Originally Posted by Denis Bassom

Yes it was, but that was only because of what it was racing against. Mostly 1600cc Escort RS1600i's of a similar weight.

I will be up against 2100cc Pug 205's that are 100KG lighter.

Fair Call,
With a 3SGE there will be little power difference (presuming the Pugs are M16 powered, if the are 8v you will crap all over them) and you should be able to developed better traction and balance. Putting the power of an high spec 2 litre motor through the front wheels is a big call, even with slicks (if you use them). The BTCC cars had trouble and the rule makers thought the chassis was worth 50 kg, so I wouldn't despair. Weight transfer and only asking the tyre to do one thing at a time (steer or power the car) will be your friend!
That is providing you can get some balance in the handling!

[Al Weyman]

Thing is Notsoswift Dennis and I have already been up against these Pugs and they are like quick quick. I don't know why they go so well but they do especially around a tight circuit and will beat my 500bhp plus car.

[johnny yuma]

Originally Posted by Al Weyman

Thing is Notsoswift Dennis and I have already been up against these Pugs and they are like quick quick. I don't know why they go so well but they do especially around a tight circuit and will beat my 500bhp plus car.

Sounds like the old days whem Cooper Ss could beat all but the best Mustangs --because the damned things weigh nothing.Weight is the enemy of performance is the truest adage in motorsport.

IF a fwd is 2 litre but it weighs nuthin,the outcome of least resistance
will be forward propulsion,from a faster cornering speed than a heavy car can sustain.If a fwd car has too much mass more bad stuff happens-they dont go around the corner as quick or accelerate out properly or brake as late.

anyhow I'd still rather drive a Camaro I think !!

[johnny yuma]

Dennis:Google "craigslist oahu auto parts battle version".Corolla AE86 good PART available for camber/roll centre improvement $100 US.

and soften up the rear suspension

[coln72]

Had similar probs with my Corolla on dirt. It would snap oversteer in third gear (from a pushrod 1.5!). Ended up removing the rear ARB initially, then softened the rear leaves to try and get some moe bite in the rear end.

Another mod that I did was to change the mounting points of the front control arms, approx an inch out and up. The difference between my car and another Corolla set up identically (springs shocks etc) was chalk and chese. dont know why but it was effective in reducing understeer. This was well before the rear was modified.

[greenamex2]

Originally Posted by Notso Swift

Fair Call,
With a 3SGE there will be little power difference (presuming the Pugs are M16 powered, if the are 8v you will crap all over them) and you should be able to developed better traction and balance. Putting the power of an high spec 2 litre motor through the front wheels is a big call, even with slicks (if you use them). The BTCC cars had trouble and the rule makers thought the chassis was worth 50 kg, so I wouldn't despair. Weight transfer and only asking the tyre to do one thing at a time (steer or power the car) will be your friend!
That is providing you can get some balance in the handling!

As already said by Al, the Pugs are 8v and I can't even come close to keeping up with them in a straight line with my 1.6. Whilst the BHP is the same (circa 220BHP) they have 20% more torque AND are 20% lighter.

Fitting a 2l 16v would give me better straight line speed than them but I am not allowed to change the block so can't.

My only hope is that they all go out and convert to 16v, jump up a class and are no longer a problem!