Reading Slicks.

[JustenGT8]

Now i know i should have had a pyrometer for the day but i didn't so this is the best info i have. 250mm wide slicks (Ex Porsch Cup tyres). An easily felt temp difference by hand with outer 1/3 hotter than inner 3rd.

Both front tyres had a clean outer 2/3 surface and the rippled/balled rubber collecting on the 1/3 inner surface (not picked up off road but 'swept' across from working outer face). I run 2.5 neg and 350lbs/inch double tapered front springs.

It looks to me as if i'm only getting good tyre contact on the outer half face of the tyre? Am i not running enough camber, are my springs too soft (hence reducing camber with body roll),, a bit of both.....or is it a tyre pressure issue? (aimed for 30psi hot).

I have cornerweights for the car if that helps.

Experience appreciated as no point only 'using' 2/3 of the tyre you have

[Celica RA45]

i would go spring rates normaly 250 for road tyres 500 for slicks with different valveing in shocks this is for mc pherson struts
try 500 lb on front ,350 lb is ok for car club tyres
on the group c celica we ran anything from 500 to 600 lbs on front and anywhere from 250 to 400 on rear

[RobertoX]

Did you try adjusting tyre pressure? That wear pattern sounds like a classic low pressure pattern. (too much you tend to get more wear in the middle, too little you tend to get more on the outsides).

Does the tyre have wear indicators accross the face? Did you compare the depth of them? You may be getting this type of wear pattern but the 'meat' of the tyre being taken off evenly,

[rolleraction]

-2.5deg is not enough by the description provied. For reference, Many ipra cars run closer to -5. I'd try going to -3.5 and see how it looks. (and borrow a pyrometer to check for even temp across the tyre) Although as yours is a road car, you would then have to crank it back to circa -2.5 for the street.. -3.5 may be unsafe of a public road in the wet etc?
My experience was that playing with camber noticably improved grip in high load corners using the same spring rates. I assume youd have a bit of body roll with the v8 up front? If thats the case, then my opinion is that you need some suspension give with a decent amount of neg camber, not too stiff in the springs.
My 2c...

[IN 05 NT]

i woulda thought 350's would be very soft for the track in the gt8, i run 450's in teh front of the 23...... and 1.8' neg camber...all i can get out of the strut tops....

[JustenGT8]

Cheers guys, a heap of suggestions from here and anoither thread so i'll run thru a list of responses.

The V8 up front makes the car lighter than a stock GT4

Already has larger custom swaybar, major major PITA to change

Pressures are close as had success with this psi before and is what other cars of similar weight with similar rubber run eg STi and Porsche GT3. 2 psi can make a huge difference though so figured tyre condition would provide cluse to either up or down a little in pressure?

I need pyrometer yes

Castor is factory fixed. Zero toe front, 1.5mm toe in a side on rear.

I suspect camber too. I'm maxed out on strut tops but have some camber pins to throw in as well... so will set them up so as to have between 2.5 and 5 deg adjustment from the strut tops.

The Teins originally came with 500Fr and 350 Rr so might look to throw them back in?

[JustenGT8]

I had a bit of a google sniff around and came across this useful rule of thumb:

For Slicks, you want a a spring rate that gives you a wheel rate equal to corner weight.

No i can't recall off the top of my head what my wheel rate is but it's very close to spring rate i would have said based on design....a bit less?

Makes my current spring rates a tad low but i have a 410 now for the fr and will chuck the 350 into the rear. Combine with and deg of neg camber and see how we go on the 7th

[Draven]

interesting... spring rate in lbs/in should be the same as corner weight in lbs?

350 is too soft. I run 14kg/mm in the front (~700lbs/in) and 8kg/mm in the rear (~450), which is just how the teins come. in an ideal world those front would be a little softer, but I drive a pretty fat bitch

[oldcorollas]

doesn't the suplah have "levered" springs tho?

Justen, you can get really cheap infrared sensors (like $20-30 cheap) which will be enough to give you a good idea of the temp, and the temp difference.
something like one of the generic copies of these http://www.montanatest.com/tr-images/89f.jpg
http://www.techgadgets.in/images/inf...hermometer.jpg
was abotu $20 here

does jaycar have anything?
edit: something liek this.. but cheaper http://www.jaycar.com.au/productView...Max=&SUBCATID=

[JustenGT8]

Cheers Stew i'll have a look around but even the Jaycar one is cheap enough

[MY Racing 221]

I reckon you need more Camber too. As a rule of thumb, as your tyre gets stickier, you need more camber for it to work properly. Also possibly the easiest to change. Try and ramp it up to 3.5deg and see what happens.

And get one of those cheapo IR thermometers to get a bit of an idea of your tyre temps.

Have a chat to the people you bought them from and see if they will tell you what they consider the operating temp to be.

[SilverRA23]

Definitely sounds like not enough camber.

Doing tyre temps is a fair bit of hocus pocus for most punters.. by the time you have done a cool down lap, trundled down pitlane, got yourself out of the car and checking tyre temps, the outer edge will have cooled off significantly and you will be getting a false reading. You are better off reading the tyres as you are doing.

[rolleraction]

No cool down laps thanks.. straight into the pit lane and mate waiting with pyro in hand to record the 3 readings from each tyre asap. Do the 2 fronts first of course, and the pressures also...But I'm sure you know that.. lighter than a 3s engined jobby, wow thats IS impressive.....

[JustenGT8]

Yup, just keep engine running, do quick tmp check and head out to road asap before pads start smoking

Yup car is 80kg lighter than stock overall (could be lighter still since i last measured as interior now gone) and Fr/Rr weight balance improved appreciably as well No lead tipped arrow here mate

[Rodger]

Justen,

Do you know the castor settings? Have you got power steering on it?

Keep in mind the current spec slick the V8 boys run has very very soft side walls so they need a lot of camber to off set the side wall flex.

I'd reckon go to 2.5-3 negative camber, but seriously look for more castor, up to around 4-6 positive.

This will keep as much rubber on the road in a straight line to give you as much rubber for braking.

The castor will allow the wheel to camber up as you turn in and it will add more weight on the tyre (work the tyre harder) without the body roll taking the weight transfer.

Regards

Rodger