How 'bout this for a race setup?

[panchovisa]

Adjusting in more rear brake bias may also help free the rear on corner entry. Weight jacking on stockers works because of only left handers and because the chassis is STIFF. If you don't have a stiff car you will only get more lost.

Still recommend running on a skid pad. Get a tire pyrometer, the tires don't lie. If all else fails use some driving tricks to hustle the beast the best you can. Good luck, and remember not to throw every tweak at the problem all at once. One change at a time.

[dspillman]

If it still wants to understeer no matter what you do with setup, try some light left foot braking through the problem corners, keeping the power on though and assuming that the brakes can take the extra work.

And let us know how it all goes, fascinating stuff.

SOPwith21,

You gonna have to be under power to get her to turn with that welded rearend....BTW, keep a eye on those stub axles as well for breakage....Something has to give or slip for you to turn with the locked diff.

I ran with welded rear ....350f/250r rates with rear sway bar Koni D/As...Once I swapped in Quaife, the rear bar had to go.

David

[panchovisa]

Have to work on my reading comprehension, missed the whole thing about welded rear.

Never going to get rid of understeer with locked rear unless you drift the back end around.

Think of your "wedge" analogy. The inner rear tire describes a smaller arc than the outer rear tire going around a turn. For the CAR to follow a smooth arc the outer rear must travel farther then the inner rear. With a welded diff both wheels TRY to travel the same arc. In effect the inner rear steers the car to a larger arc (and is born chronic understeer).

Got to go now ,wife says I have to get up in 5 hours.

[sopwith21]

I ran with welded rear ....350f/250r rates with rear sway bar Koni D/As...Once I swapped in Quaife, the rear bar had to go.

David

Please tell me more about how your car ran with this specific setup... its critically important to what we're doing. What kind of track did you run, what speeds, and how did the car handle? Anything and everything you can tell me will help because this is almost exactly what I've got to work with. Also, I don't get all the lingo yet... like D/A and Quaife? Many thanks.

[sopwith21]

Think of your "wedge" analogy. The inner rear tire describes a smaller arc than the outer rear tire going around a turn. For the CAR to follow a smooth arc the outer rear must travel farther then the inner rear. With a welded diff both wheels TRY to travel the same arc. In effect the inner rear steers the car to a larger arc (and is born chronic understeer).

Got to go now ,wife says I have to get up in 5 hours.

Never argue with the wife! :laugh:

Yup, I know I'm stuck with some balance problems until we can upgrade the rear end (what do I want... a stock limited slip setup?).

Here's how we got where we are now: though race prepared with a cage and good motor, the car had basically a stock suspension when I bought it. It ran reasonably well and, believe it or not, we won three races with it this season until the front springs collapsed. Then, of course, it began pushing like crazy in the corners for all the obvious reasons.

Rather than replace the springs with stock parts, we wanted to upgrade the suspension and try to go faster. So we consulted with ProShocks and some racing people that I know (hadn't discovered this site yet) and came up with a set of parts that we thought affordable and reasonably close to what was needed. So here we are. I guess we'll know in ten days. If we can just get close enough to be able to adjust and make some corrections, we'll be alright. Its a quick car and we don't need a miracle overnight... we just need to get close on the basics.

[dspillman]

Sopwith21...

D/A..double adjustable, work good, but I've had the upper bushing fail repeatedly, forcing rebuild. 5 times in 3 years.....

Quaife...Type of LSD .....kinda like a torsion/gleason diff...bunch of gears that prevent light inside tire from spinning.....as long as there is some resistence on the light side, off the ground all bets are off, its gonna spin.

My car at the time had excessive understeer when off the gas in a turn, gotta stay in the gas to cause slippage, as well as keeping suspension loaded.

But handled fairly neutral while under power.....BUt really There's a lot of varibles in this, other then spring rates....

You really need to invest in a track day to sort out your driving style with diferent combos of suspension tweeks.

Also invest in a limited slip diff of some sorts..that welded stuff robs a ton of power...every where your not running straight . get toe in zero'd at both ends as possible for the same reason...so long as you can still drive it....soft or worn bushings can make it scary with zero toe.

david

[260DET]

Ooooh, I missed the CIG locker (welded up) diff bit too :stupid: In that case I-know-nothing

[dspillman]

Sopwith 21,

Camber in front at least 2 1/2 neg...more if you can get it....

In the rear...2 1/2 neg more if ya got it..keep check on the wear, and temps

My car seems to handle better at 5 3/4" rocker panel height then 5" ...too low can screw up the geometrys

Go out and have a blast!

David

[sopwith21]

Thanks, David. I'm really at a disadvantage because I live 700 miles from the race track and make special trips there to drive each event. But, we're in the points chase big time and every little bit helps.

Important note: I have no camber plates installed. Maybe later, but for now, we have no camber adjustment (there's no camber adjustment in the stock suspension is there?) and the car has not been lowered.

Important questions: So... with the 350fr/250rear spring setup, you understeered badly... right? Until you learned to keep your foot in the gas in the corners, and that helped it go nearly neutral? You mentioned 5 3/4 rocker panel height... will I have any trouble achieving this height using the coilover adjustment, and is that where you would recommend starting? Remember, I have no camber plates (yet) and have not lowered the car, so that's a factor.

Is there any preload adjustment in the front sway bar if the bar is still stock? Taking out some preload might help the push.

Thanks again. Big race this Sunday... next to last show of the year and we're only leading by 95 points. Eek.

[dspillman]

Your gonna have trouble getting much negative camber without camber plates....lowering the car will help some, but without more camber your tires aren't gonna provide max traction...what tire/wheel combo you using? Excentric bushings, and a couple of other tricks can also give additional camber...

Without adjustments at swaybar ends, you will most likely have some preload, which amounts to more spring rate at that end of car...I think. I've always set up alignment, corner weights..all adjustments with sway bar un-hooked, then adjusted swaybar end links so there is no preload while sitting. No adjustment on stock bar.....You have looked under there? :classic: ....

The end links really needs to be adjustable....to avoid preload. Different attachment points on sway bar can be welded on as well to allow changiong lever arm length.

david

[jmortensen]

Here's a 1/2 assed preload removal procedure for normal endlinks. Been using it for years now...

Driver sits in car on alignment rack or with car on 4 blocks so that the other person can get to the end links to adjust. Disconnect the driver's side of the sway bar, loosen the other side until there is no compression of the bushings. The bushings are just barely touching the control arm and the bar. Add washers to the drivers side in the middle of the end link until the bushings just touch on that side. Tighten bar evenly.

I'd suggest that sopwith switch the front and rear springs, especially with a welded diff.

If it's legal for your type of racing you could drill new holes in the front crossmember to get some neg camber up there. My experience is that a lowered Z will have too much neg camber in back and not enough in front.