Alignment settings & tires for racing

[jrtoffroad]

Hey guys,

I've been autocrossing my Z recently (details and vid's here: http://www.zr1.net/forum/showthread....592#post111592 ) and am just about ready to pull the trigger on a new set of Nitto NT01's. Any experience with these? I plan to run them in the stock size on my extra rims and use them only for racing. I'd love to know how the hold up, is the grip comparable to other r compound tires, and what pressures work well as a baseline for our cars.

I'd also like to step up to some more aggressive alignment settings. From what I've read I'm thinking:
Front: 1.5-2 deg negative camber, no toe in, and caster at stock specs
Rear: ~1 deg neg camber, 1/16" toe in

Thoughts? I do drive this on the street, and plan to use it for road course work as well as autocross and drag racing. I've read mixed opinions on caster but, from what I understand, to achieve significant negative camber on a C4 I'll likely have to remove all the shims and have no caster adjustment (my car is lowered, not sure if this still holds).

THANKS!
Jordan

[tccrab]

Here's a link to Dynomites solutions pages that address alignment:
http://www.zr1.net/forum/showpost.ph...59&postcount=2

Depends on what kind of racing you do:



TomC
'Crabs

[PhillipsLT5]

http://www.vbandp.com/Tech-Info/

[batchman]

Hey Jordan welcome to autoxing the Z. I run in BSP up in New England, the Evos have me pwned except on a small lot/1st gear course (the car is an absolute RIOT on one of those!).

I run (huge) a6's, can't comment on the Nittos other than I have used 555R2s before on another car, a good dual use tire but not competitive with full slicks. I gather the nt01's answer the same description. Probably a good choice for event day if you're not chasing FTD, and should work in some wet and some cold better than the true slicks (v710/a6/r6) and will last longer too.

I have my front as you describe, but rear at -2.5deg and about 1/4" toe in. I only got about -1.5 in front and need more, so it's offset bushings for me. Street manners are fine except for rut-worn roads will pull you around a bit. I found the rear bar was too big even with the wild alignment. Of course I've doubled the spring rates (and need to do it again LOL).

I found the slow rack to be an obstacle so I campaigned for an SCCA rules change and got it, now I run a quick rack from a z51 This gave me trouble with power steering pump and cooling, if you have issues get the Turn One ZR-1 "stock replacement for autocrossing" and you'll be good. I went through a whole lot to discover that .

I'd start with low 30s for tire pressure, start same all around and re-check them before each run as they will increase and heat-soak. Get yourself one of those cheapie IR pryometers and use it to check tire temps inside, middle, and outside - adjust pressures (and alignment) until you're as uniform across the tire as you can get. Decrease pressure at the end that loses grip first, try a couple pounds at a time. Don't go below 28 or so trying to fix the too-big sway bar though!

One other tip, these cars understeer under braking so get your braking done in a straight line! And make sure your brake fluid is fresh since once you find the right pedal you'll want the middle one soon after!

Best,
- Jeff

[lbszr]

Originally Posted by jrtoffroad

Hey guys,

I've been autocrossing my Z recently (details and vid's here: http://www.zr1.net/forum/showthread....592#post111592 ) and am just about ready to pull the trigger on a new set of Nitto NT01's. Any experience with these? I plan to run them in the stock size on my extra rims and use them only for racing. I'd love to know how the hold up, is the grip comparable to other r compound tires, and what pressures work well as a baseline for our cars.

I'd also like to step up to some more aggressive alignment settings. From what I've read I'm thinking:
Front: 1.5-2 deg negative camber, no toe in, and caster at stock specs
Rear: ~1 deg neg camber, 1/16" toe in

Thoughts? I do drive this on the street, and plan to use it for road course work as well as autocross and drag racing. I've read mixed opinions on caster but, from what I understand, to achieve significant negative camber on a C4 I'll likely have to remove all the shims and have no caster adjustment (my car is lowered, not sure if this still holds).

THANKS!
Jordan

It's good for the road track. The 01 has good longevity, but I'm running 2.5 up front and still have to flip the tires on the wheels to get all their life. Rear is 1.6 camber and they wear pretty even on the track. Cold 26 psi seems to give me the best traction when they get up to temp, with less camber, they need more pressure though (at least if your going for maximum tire wear). I don't think their the stickiest, but a good price. For competition, I see Hoosier and Kumho 710 used a lot. I don't know how the 01 would do for autocross, it might not get up to temp fast enough. Nitto might have some good suggestions, their nt05 might be good for autocross and the road track. If your driving to the track, the r compounds are not good.

With stock control arm bushings, 1.5, 2 is probably the maximum you'll get, maybe even less. Just match the other side to the side that has the least. I think 1.3 was all I could get from the drivers side on mine with stock bushings, the conical washers were even machined down as thin as possible, I forget what caster ended up at, I matched that to the other side also. The rear with the 1/16 toe in will make it handle really good.

I've only put about 3000 a year on mine, but I can't really say the camber is causing bad tire wear on the street, and if it did I would keep flipping the tire on the wheel. 0.0 toe on the front.

Hope some of this helps

[jrtoffroad]

Thanks for the advice!

Vette brakes advice seems to jive with what I was thinking. Interesting to see how little neg camber they recommend up front in a C5, wonder why....


Batchman,
Glad you weighed in, I've followed your autocross thread. I planning to stick with stock sizes front and rear (you're running 315's up front right?!), but still find the car to be a little tail happy. Although fun, wondering if it'd help to slap a 30mm bar up front.

Haven't had any real complaints with the steering ratio yet, but that probably means I'm just not fast enough .

I was running ~37 up front and ~36 in the rear with my street tires, but found a little better traction after lowering that to about 35 & 33. The pyro gauge is a great idea, afraid I'm not getting much out of reading the side wall.

lbszr,
Thanks for the input. I really like the price of the NT01...but have also been looking at the Hoosier, Kumho, and BFG slicks.

Guess I'll see how far I can go with stock control arm bushings, then figure out which tires are in the budget.

[lbszr]

Just had to put this eye candy on here in case you wanted to be able to dial in almost anything, from Guldstrand.

I did offset bushings. But after pricing, it wouldn't cost that much more to do these control arms instead. I'm not adding in new upper ball joints though, which might be needed.

I think the C5's run less camber in "theory" because the frames flex less. But I rode in a C5 Z06 with -3 camber up front with R6 Hoosiers, starting at 20 psi cold. His front tires were wearing even and that thing stuck to the track like glue, on a road course.

[lbszr]

Thought these specs were interesting from the General Motors ZR-1 dirvers manual.

[jrtoffroad]

Wow, those control arms are hot. Shouldn't tempt me with things like that

Thanks for putting up the pics of the drivers manual...I need to get one of those! Did those come with the car from the factory? Could you verify what it says for toe-in? It's a little hard to read.

-Jordan

[lbszr]

Originally Posted by jrtoffroad

Wow, those control arms are hot. Shouldn't tempt me with things like that

Thanks for putting up the pics of the drivers manual...I need to get one of those! Did those come with the car from the factory? Could you verify what it says for toe-in? It's a little hard to read.

-Jordan

The manual came from the zrnetregistry. I don't think they have them now. I'm not sure, but I think they did come with the car when they were new.

The manual lists 10' for the front toe in, and 25' for the rear toe in. Actually, I'm not sure what that means? If 25' means .25 inch, that seems like a lot to me.