Suspension Experts - autocross/Track/swaybars etc (pics up)

[Bazda]

When I ran 8kg in the front on my car, once the front rolled over like that I had no turn. I possibly run my car lower than you though.
If I jacked the height up it actually was alot better. This is why i'm doing the RCA on mine. I compensated for this by running 14kg front springs but at low speed corners not so great, the car would push alot, esp around Taupo.

Whiteline front sway bar helps alot. I would start there and see how that goes.

[pc]

Give the suspension more droop, that'll keep the wheel on the ground for a while longer.
Should be able to do it using keeper spings so that the springs remain captive when the weight is off the wheels.

[FANGIN]

O/T, but when was that Auto Cross? Would have been in the last 8 weeks judging by how far along the building in the back ground is? Keen to attend the next one.

[strx7]

Sunday 31st october.

[KinLoud]

Ok.
Question
- what is the car doing when you lift a wheel? understeer or oversteer?
it is probably power understeering

There are several ways of reducing understeer - usually you increase the roll rate (spring or swaybar rate) at the opposite end of the car.

Perhaps your problem is a result of several things adding together so you might need to try a combination of things.

Read Carroll Smith Tune To Win - you might need to read it several times to get the most benefit from it

My suggestions:
- raise front ride height to raise roll centre - this will reduce body roll and understeer. Also consider rca adjusters.
- higher spring rates all round to reduce body roll
- consider increasing rear spring rate relative to front and then reduce rear swaybar rate - this will help keep inside rear on the ground longer (as Matt Dunn said)

You can probably optimise handling for the slow sharp corners of an autocross but may affect handling in faster corners.

Does it lift a wheel turning both ways? - maybe check your corner weights OR adjust one spring height to balance out the left/right turning (make small adjustment maybe 2 turns then see if its better worse/try adjusting the other way.

Good luck - Ken

[edwagon]

Ok.
Question
- what is the car doing when you lift a wheel? understeer or oversteer?
it is probably power understeering

There are several ways of reducing understeer - usually you increase the roll rate (spring or swaybar rate) at the opposite end of the car.

Perhaps your problem is a result of several things adding together so you might need to try a combination of things.

Read Carroll Smith Tune To Win - you might need to read it several times to get the most benefit from it

My suggestions:
- raise front ride height to raise roll centre - this will reduce body roll and understeer. Also consider rca adjusters.
- higher spring rates all round to reduce body roll
- consider increasing rear spring rate relative to front and then reduce rear swaybar rate - this will help keep inside rear on the ground longer (as Matt Dunn said)

You can probably optimise handling for the slow sharp corners of an autocross but may affect handling in faster corners.

Does it lift a wheel turning both ways? - maybe check your corner weights OR adjust one spring height to balance out the left/right turning (make small adjustment maybe 2 turns then see if its better worse/try adjusting the other way.

Good luck - Ken

This has jogged my memory - either that book or "How to make your car handle" has a heap of info about Auto-cross setups.

Pretty sure one of his points for setting up fwd cars to avoid power understeer was to set the rear up with toe-out (or less toe in), but makes the point that its only useful for lower speed stuff - too hairy for higher speed corners.

Are you using good tyres? Possible to run grippier tyres on the front than the rear for autocross to adjust the handling? Obviously want to increase overall grip rather than reduce it at the back, but if the car handles better it may well be quicker (and more fun!), even if overall grip is slightly lower.

[strx7]

it is power understeering VERY minimally.

The main thing it is doing by lifting the wheel is loosing fowards drive. The actually turn in/turn out I'm happy with, I just want to keep all 4 wheels on the ground to get more acceleration out of the corner.

I'm thinking I look at say 500lb front springs and 350lb/375lb rears.
and possibly try a heavier front swaybar.??

[Truenotch]

Have you got standard bars on it at the moment? I think a bigger bar would be helpful.

And it's dipping quite a lot in the front, so you might want to try even harder than 500. Maybe 550-600, but this could be a bit hard if you intend to use it on gravel.

Have you got any friends with race cars that might have extra springs? Having a few different rates to borrow for testing is helpful.

[fxgt race]

Basically what is happening is what you want. Lifting a wheel is what you want in order to keep the car flatter on the corners and help with understeer. I run the rear bar solid between my rear wheels in my race car to get the inside wheel to lift. I've you put a heavier rear bar in it will lift the inside wheel even more, thats what i would change first, one change at a time to see whats going on. If you change to harder springs it will be to hard for the ruffer courses thet you may do. New rear plate diff is what you want, Having less drive in the rear could be a good thing as don't 4wd tend to push understeer around corners. The last 4wd i drove on i track was terribe, had to give it a boot full mid corner to give oversteer to get around corners otherwise it would understeer like a pig.

[strx7]

i'm currently running 225/50/16 toyo r888's i want to go to 215 or 205 17's that way i will get rid of the rear guard rub, and will have the clearance required to fit my 310mm front discs.

for what its worth, i was 1st 4wd car and 2nd overall at the autocross.

[Bazda]

I run 225/40/16.. 50 profile is pretty tall!

I agree with fxgt race, you want the rear to lift a bit and also agree that you dont want as much lsd effect on the rear end being 4wd.
When I raced gas RC cars we all ran diffs that locked under accl in the fronts and minimal lsd effect on the rear diffs (plate lsd but very mild). The front would unlock the lsd when deaccl.
This was perfect and stopped all that understeer you get with 4wds.
And the rc car used to lift the inner rear wheel as well .

[Bomis]

Sounds and looks like you would need to set it up like a FWD, with a hard sway bar on the rear. Hard to know what a stiffer LSD would do in the rear, if its lifting a wheel and your loosing drive out of that wheel, then a stiffer LSD would force more drive to the contacting wheel and fix that, but then if it fails to lift a wheel you may get understeer, or if you can get enough power to the rear, oversteer.

Wonder what a LSD in the front would do? How did they set up celicas for road racing?

Also, have seen you/this car at a few MBOP events, was pissed I missed this event last weekend, is one of my faves!

[pc]

I've found when cornering hard on tight AutoXs that once a back wheel lifts significantly, the rear end skips about as the rear wheel with contact grips and then slides.
Having 2 rear wheels on the ground would be better.

[strx7]

I did wonder if i should get the std corolla 4wd diff, weld it up, and try it at an autocross with a locked rear diff.

I have an LSD which I will try to put into the front at some stage, but that wont be for 12 months or so.

[strx7]

I run 225/40/16.. 50 profile is pretty tall!

I had these tyres to go on my RX7. With the open centre diff i was running, traction was the biggest issue. i thought that 225's would be worth a try in an attempt to get as much contact with the road as possible. now with a viscous centre diff 205 or 215's would be adequate.