HJK

Just started racing my 944S2. So far been using Nitto NT01 in 235/40 and 275/35 x18 and MPSC in 235/40 and 265/35x18 and having a lot of fun. Now I'm chatting with people about slicks and what I hear all the time is this; "if you switch to slicks your whole set up has to be adjusted".

So i've been trying numerous searches here and on the web in general and I do find the expression but I cannot find concrete set up changes required for slicks.

Am i just plain stupid? What set up changes are necessary, assuming that once you have slicks on the car you check your temps, adjust camber when and where required to get the temps where you want them, what else is there to "change the whole set up"????

I'm running on KW competition shocks with 120N (680lbf) in the front and 220N (1200lbf) rear, torsion delete, lightweight rear axle.

The car weighs in at 1120 kg (2460 lb) with me in it and 25 liters of fuel.

Please let me know what I'm missing, I'd love to go out and try real slicks, but I don't want to be way off.

I've tried a set 24/64/18 porsche cup front tyres all around and knocked off4 seconds on a 1.30 lap and didnt have any trouble I thought with handling except for getting the rear tyres upto a good temperature.

Suggestions and ideas welcome, thanks

henk

joseph mitro

i'm still on the learning curve myself, but a few pointers i've learned:

differentiate between radial slicks and bias ply slicks....setup will be markedly different as biasply need less camber I'm told

spring rates may need to change. i'd talk to a professional suspension guru to set an ideal setup. in my case, i used the same spring rates as when I used the Hoosier DOTs. is the car ideal? I'm sure it's not, but given that i'm a one-man team, i'm more focused on the driver right now.

333pg333

Still amazed at your spring rates Henk!! I can't help you with the slick setup, but you want to seriously consider dry sumping.

Can you get Hoosiers where you are? Not a bad stepping stone to slicks.

North Coast Cab

What is that?

Really? That would be a dry car around 2200-2250lbs?

joseph mitro

Hoosiers make slicks.
they also make DOT tires.
are you confused?

333pg333

No, sorry I meant the DOTs in this case. Just as a stepping stone to the slicks. Go for the full slick by all means but I know what the OP is driving and my impression is that this would also be a good move up from R spec. In terms of Henk saying that he has heard the the whole setup has to be adjusted, well many slicks are a taller tyre so perhaps that's what these people were alluding to apart from any handling differences.
In saying all this, I'd like to hear what can and should be done on a similar setup vehicle for slicks. Considering it myself.

va122

you need a lot more camber for slicks and a higher spring rate.

SundayDriver

Personally, I don't feel the answer can be generalized. I have seen this comment a few times and don't understand the logic/physics behind it - can you explain please?

va122

I may not understand the physics behind it, I'm just gong on the manufacturer's recommendations. Michelins and Hoosier slicks like a lot of -camber. The spring rate thing is also per Hoosier. To get as much heat in the tires as possible.

TheOtherEric

There's clearly some confusion here about the term "slicks". The word itself is vague. Generally, slicks refer to bias-ply tires that have no grooving in them; and are not DOT tires. But there are exceptions. When people say "Hoosiers" for our cars they generally mean DOT R tires that are radial, not bias ply.

So when you ask about camber for slicks, you're asking if switching to bias ply should impact camber. And the answer is yes, just google and you'll see people run closer to -1 camber on bias ply slicks but more like -3 or -4 on radial ply Hoosiers.

Confused yet?

va122

Hoosier makes a non dot racing slick and it's a radial slick. Bias slicks are old news

Larry Herman

I agree. To say that you just can't put a set of racing slicks on your car is silly, of course you can. And if you drive them right, they will be faster. I used to run slicks on my stock GT3 with no problems and no modifications other than alignment.

That being said, they will be better, but they may not be optimal. The added grip of the slicks will cause additional body roll and suspension deflection, which can mitigate their overall performance, and so this should be taken into account, especially in cars with rubber bushings and softer springs. If your car already has solid bushings and spring rates north of 800 lbs/in, save for optimizing the camber, you are certainly good to go for slicks, IMHO.

333pg333

Guys, Henks build is very well done. There wouldn't be much rubber left in that car I suspect and his spring rates are 628 f/ 1256 r. I know this sounds crazy unbalanced but that's what he was recommended by the supplier of his suspension.
So on a contemporary Michelin slick are we saying that you don't have to run as much camber as a Hoosier DOT or Nitto Nt01 Rspec? We tend to run about 3.5 / 2.5 neg f-r.
Build is here:

https://rennlist.com/forums/924-931-...4-project.html

va122

no, you need more camber then a dot-r

333pg333

So is that an absolute? In other words if you are already at -3.5 neg are you saying that just by virtue that you shift to a full slick that you have to run more neg by default?