Getting power down out of corners.

[burninator]

Over the winter I sectioned my struts, installed Koni Yellows, EMI camber plates (front and rear), 350 lb/in front springs, 300 lb/in rear springs, and urethane bushings on the whole suspension (except the rear bushings on the t/c rod which are replacement rubber). It has no rear sway bar and the stock front sway bar. My car now handles a billion times better than it did last year. I have a 240 with that's totally stripped out on 205/55/14 Nitto NT-01 tires front and rear.

 

I only use this car for autocross.

 

I'm trying to perfect the setup. First I reduced the damping in the front, then I raised the front ride height a bit, both of these changes were to reduce the oversteer I'm getting. It feels better now, and is fairly neutral, but I'd like to be able to get back on the gas sooner out of corners. Right now when I start getting back on the throttle the inside tire spins and the car will oversteer.

 

I've thought of trying to raise the inner front LCA pivot thinking raising the (geometric) roll center might make it roll less in the front and keep the rear more planted giving me better traction in the rear. But I know this will also reduce the bump-steer which I think might be keeping it stable earlier in the turns. This may also give me a better camber curve (for what little roll I have, I'm not sure how much affect this will have) which might give me more traction in the front causing more oversteer.

 

I may not know enough about suspension to even be asking questions like this but I'm learning. Also, I have searched a lot and it helps but leaves me with more questions.

 

Anyone got any advice for me?

[JMortensen]

Don't rely on bumpsteer to keep the front end stable. Fix it (meaning get rid of it). Keeping the tire pointed where the wheel is pointed will do more to make the front end stable than toeing out on bump in my opinion. There are different ways to fix it, I think slotting the front crossmember is pretty easy to do and mine never slipped in the 6 or 7 years that I daily drove it and autoxed and did track days.

 

As for traction, I think the easiest thing to do would be to get a wider tire. 205 is pretty small, especially for an autox Z. If you want small diameter for less rotating mass you might try to grind calipers for clearance and run some 13" rims so that you can find some wider tires. I think tire sizes are very limited for 14's, or were last time I checked.

 

EDIT-- The other obvious solution is a limited slip.

Edited July 12, 2010 by JMortensen

[johnc]

 

EDIT-- The other obvious solution is a limited slip.

 

Ding, ding, ding, ding! We have a winner!

[burninator]

Probly right about the lsd, and I've thought about it. But from what I can tell it's a fairly expensive modification. I just can't see spending that right now.

 

Wider tires are definitely in the cards, also expensive though. I think I'll burn through these first... they'll last the rest of the season.

 

I am still hoping to find a solution that will help (even if it's not the ultimate solution) by making changes to my current setup. After spending so much on the suspension parts I just put in I can't start spending big dollars again right away.

 

What am I likely to notice by moving the inner pivot up? Is my theory about less roll in the front keeping the rear tire planted (like adding a larger front bar) at all sound, or am I way off base? If moving the inner pivot up is likely to give me more grip in the front and change the balance back toward more oversteer I can't see it being beneficial at this point. But, if all I have to do is add a little more static toe out and have it reduce my roll (thus helping the rear grip) then I'll jump right on that.

 

Thanks for the suggestions.

[JMortensen]

If you're running an R180, then it is an expensive modification. With an R200, not so much. You can get the OBX diff for ~$400, and a used Nissan LSD for $300 to $500, depending on where you get it used. Depending on your cost for the other parts to actually get it in the car (R200 mustache bar, the diff itself, bushings for mustache bar, etc), it might be significantly cheaper than the R180. If you don't have a lot of parts resources it's going to be expensive. If I had an autox car that was right at the weight minimum and had the money for an R200 swap with LSD but not the R180 LSD, I'd do it despite the weight penalty of probably 50 lbs. The ability to put the power down out of a corner is pretty crucial in autox.

 

Raising the front roll center will increase roll stiffness and that should mean that it's easier to put power down. If it causes too much understeer, dial in more toe out. The primary concern is the bumpsteer though. Bumpsteer is bad, and getting rid of it might make more of a difference in the handling than raising the roll center. If it were a road race car I would say definitely will make more of a difference. Bumpsteer is more important on rough surfaces and at higher speeds, but certainly it is going to change the handling of the car, just as changing the static toe will.

Edited July 12, 2010 by JMortensen

[johnc]

Solving traction problems by compromising handling, not so good. Solve traction problems by adding traction. Start searching for used LSD R180s. They are out there. I've also started another production run of the STi side axles if you are lucky enough to find a cheap R180 out of the back of a WRX STi. It takes some searching but they are out there too.

[260DET]

One problem with a S30 is that its very difficult to get big, say 8 degrees, caster at the front which would help turn in. The better the front works from tweaks like that the more the other various settings can be biased towards helping rear grip which is where later model Nissans like the S14 are strong and for example can carry a large front ARB which of course helps rear grip.

 

Got rear toe in? Maybe 5mm? And a bigger front ARB. Its intructional coming from a S30 background and seeing what the later model strut front suspension Nissans can do out of the box.

[burninator]

I don't like compromising handling to keep balance, but I'd still rather not add traction and make the car harder to handle. Everything is a trade-off. I'll see what happens with the pivot relocation. It would be nice to have an LSD if not for the cost a couple hundred dollars might not be much to some people, but to me... well, someday it'll happen. I'll keep my eye out for some used parts.

 

Got rear toe in?

Rear toe is non-adjustable.

[260DET]

I don't like compromising handling to keep balance, but I'd still rather not add traction and make the car harder to handle. Everything is a trade-off. I'll see what happens with the pivot relocation. It would be nice to have an LSD if not for the cost a couple hundred dollars might not be much to some people, but to me... well, someday it'll happen. I'll keep my eye out for some used parts.

 

 

Rear toe is non-adjustable.

 

The S30 needs rear toe in, end of story and everything is not a trade off which is what I tried to explain eg front caster. If you are going to put limitations on what you are prepared to do then its a bit pointless asking for advice and then in effect rejecting it, if I may be blunt

[Drax240z]

I've got an R200 with a Quaife in it I might be willing to part for the right price. Shoot me a PM.

[burninator]

One problem with a S30 is that its very difficult to get big, say 8 degrees, caster at the front which would help turn in. The better the front works from tweaks like that the more the other various settings can be biased towards helping rear grip which is where later model Nissans like the S14 are strong and for example can carry a large front ARB which of course helps rear grip.

 

Got rear toe in? Maybe 5mm? And a bigger front ARB. Its intructional coming from a S30 background and seeing what the later model strut front suspension Nissans can do out of the box.

The S30 needs rear toe in, end of story and everything is not a trade off which is what I tried to explain eg front caster. If you are going to put limitations on what you are prepared to do then its a bit pointless asking for advice and then in effect rejecting it, if I may be blunt

Well, excuse me for being blunt back. I have some caster with the EMI plates, more would be difficult. However, you can't say caster isn't a trade off in a car with sticky tires and manual steering that's already a pain to steer at low speeds (a real ***** when stopped), more caster would increase the steering effort. But your talking about increasing turn in and front grip in a car that already oversteers so I can do "various other settings" to bias the car more towards rear grip, but your not giving me much there. You mentioned rear toe in which I did address, and I'd have to modify my rear LCAs or puchase completely new ones to accomplish edit - forgot about camber bushings, I just explained that I can't do that right now. There are also trade-offs to rear toe-in it may reduce oversteer but it can also reduce turn-in. A big front roll bar is a good suggestion is also something I've thought of, but it's not without tradeoffs either, in exchange for altering the balance it can reduce grip in the front by lifting the inside front tire. I'm obviously not an expert, but to the best of my knowledge handling balancing is full of compromises.

 

I'm not sure there is 1 right answer. Sorry if I seem defensive here. If you have any suggestions I'd still like to hear them. I wasn't trying to knock the suggestions you made, but you've offended me by suggesting that I'm arbitrarily rejecting the perfect solutions I'm being offered (but maybe I'm reading too much into your comment). I thought maybe my existing setup could be changed to improve it. I'm not putting limitations on what I'm willing to do, except that I don't have the money to start buying new parts right now.

 

I've got an R200 with a Quaife in it I might be willing to part for the right price. Shoot me a PM.

A Quaife?! Sounds Expensive. Thanks for the offer, but unless the right price is right around a 1 followed by 2 (but only 2) zeros I'll have to pass. I'll keep it in mind if I come into some extra cash and you haven't sold it yet.

 

Thanks again everyone for your help. I have some things to try out and some things to save my money for.

Edited July 13, 2010 by burninator

[JMortensen]

Camber bushings work for toe adjustment in the back and aren't nearly as expensive as control arms.

[jt1]

My thoughts:

 

Softening the damping on the front usually makes oversteer worse. Have you tried stiffening the front?

 

Rear toe in is a good thing, I added some at JohnC's suggestion and it made a noticeable difference. The MSA bushings are a cheap way to do this without expensive arms. You can also increase rear camber and that will help too.

 

Raising the front pivots is almost always a good thing in general, especially if you're running the car pretty low. After raising them, work on the bumpsteer to get it to a minimum. This probably won't help the oversteer but will improve handling overall.

 

A larger front roll bar would be pretty cheap and good to try, and would probably work well with raising the pivots.

 

Throttle modulation is important. A fairly "slow" linkage is a big help here, along with good tip in response, to avoid shocking the tires and suspension.

 

A LSD would be a big help, but cost more than all the other stuff together. If it's not in the budget, you could weld up the rear end. This is cheap but is pretty much a track only mod, as it will be pretty ugly on the street. Some guys run them on the street, so it's possible.

 

You are exactly right when you say any change affects other stuff. You're looking for the optimum point somewhere in between that yields the best times.

 

jt

[FlatBlack]

My $0.02

 

Installing an LSD helps out in so many ways. After I put mine in, I wondered why I didn't do it much much sooner.

 

Are you N/A?

Edited July 13, 2010 by FlatBlack

[burninator]

Camber bushings work for toe adjustment in the back and aren't nearly as expensive as control arms.

I had forgotten all about those as an option.

 

My thoughts:

 

Softening the damping on the front usually makes oversteer worse. Have you tried stiffening the front?

 

Rear toe in is a good thing, I added some at JohnC's suggestion and it made a noticeable difference. The MSA bushings are a cheap way to do this without expensive arms. You can also increase rear camber and that will help too.

 

Raising the front pivots is almost always a good thing in general, especially if you're running the car pretty low. After raising them, work on the bumpsteer to get it to a minimum. This probably won't help the oversteer but will improve handling overall.

 

A larger front roll bar would be pretty cheap and good to try, and would probably work well with raising the pivots.

 

Throttle modulation is important. A fairly "slow" linkage is a big help here, along with good tip in response, to avoid shocking the tires and suspension.

 

A LSD would be a big help, but cost more than all the other stuff together. If it's not in the budget, you could weld up the rear end. This is cheap but is pretty much a track only mod, as it will be pretty ugly on the street. Some guys run them on the street, so it's possible.

 

You are exactly right when you say any change affects other stuff. You're looking for the optimum point somewhere in between that yields the best times.

 

jt

You may be right about stiffer compression damping being the way to go (if that's what you meant), but the dampers are rebound adjustable only. I did try going the other way (stiffer rebound) on a buddy's suggestion and that didn't help (might have made it worse). Softening the rebound on the front makes it transfer more weight to the rear and helps it hook up.

 

I think the only way to know about the rear toe thing is to try it out and see how else it affects the car. I'll look into the price of those bushings and put them on my list along with the big anti-roll bar and the lsd.

 

I don't know about welding the diff. On a tight autocross course it seems like it would make it pretty hard to turn.

 

Are you N/A?

Yeah, my car is N/A. All 122 hp of it.

[FlatBlack]

Yeah, my car is N/A. All 122 hp of it.

 

Well your springs are hugely stiffer than mine, but I've never have issues with oversteer. [i have a bit over 122HP ]

 

How long have you been autocrossing? Also, are the courses really fast with long straights or mostly tight corners?

[burninator]

Well your springs are hugely stiffer than mine, but I've never have issues with oversteer. [i have a bit over 122HP ]

 

How long have you been autocrossing? Also, are the courses really fast with long straights or mostly tight corners?

We get a mix of different course types. They are probly a little tighter than what others are used to because we only have a few places close by to use and the lots are fairly small.

 

What spring rates and tires are you using? Any other relevant mods?

[jt1]

My mistake, I thought the yellows were double adjustable.

 

I think you'll like the bushings. You can add some toe and camber both, and that's almost certainly going to help.

 

Welding the diff with almost certainly cause a turn in push that you'll have to drive around or tune out otherwise. But it's cheap and can be dealt with.

 

When you get a chance, read thru some of Cary's (tube80z) posts. He's done a lot of autocross chassis tuning and has some good ideas. Some of which are over my head.

 

jt

[FlatBlack]

What spring rates and tires are you using? Any other relevant mods?

 

Tokico red springs [185/200 IIRC?] HP Blue struts

15x8s with 225/50/15 G-Force Sports

Helical LSD [modified OBX]

Suspension Techniques front sway bar, stock rear sway

Poly bushings

 

I don't find the car hard to turn at all. I used to have 205/55/15s. Bigger meat won't make much harder to turn, especially at speed.

 

I'm running at an AutoX this Sunday with my new S12+8 Calipers [never used them on-track]. Can't wait.

 

How long have you been racing?

Edited July 13, 2010 by FlatBlack

[burninator]

How long have you been racing?

This is my 4th year autocrossing.