joseph mitro

You wanna buy my 235/40s RA-1s with no shaving and 1 heat cycle? I'll be at TWS in two weeks and didn't like the first session i used the RA-1s for. maybe they'll get better, but they felt worse than either the hoosiers or the hankooks

Greg Smith

That's your problem. Get them shaved to 4/32 and then see what you think of them. At full tread they're like a street tire. Dave says the RA1's(once the tread blocks are gone of course) are faster than the hankooks. Ofcourse Hoosiers are gonna be better than both.

joseph mitro

i figured that was part of it, but it felt like i was driving on balloons. floating all over the place

Veloce Raptor

Yeah, what Greg said. When full tread, they are great in the rain, but in the dry, they get way too hot way too quickly due to all the tread squirm. You have to sort of underinflate them until a bunch of the tread wears away. The Kooks are even worse in this regard. I started the Kooks at 23 front cold & 21 rear cold at Barber last weekend, and they were they best they ever got. Anything higher, and they went ****-up after 2 laps.

Hoosiers will be slightly quicker than RA1's, IMO, depending on car set up (it will be slightly different for them vs. RA1's), but much less predictable after the first heat cycle, and much shorter lived. The R6's are, I hear, much better than past Hoosiers, but still the above remains true. If you want that extra second & have $$$, buy Hoosiers. If you want to win an enduro, especially in warmer weather, use the RA1's or the Kooks.

Bonster

As well, the RA-1s can chunk in dry conditions when at full tread. Either save them for wet weather track days or just have them shaved.

smlporsche

Bonni-

I think the target temps for RA-1's are somewhat car dependent. On my S2 I find that 37 PSI is perfect for me with 36 to 38 being my envelope. At 39 I start to get serious squirming under threshold braking and turn in. Depending on the track and ambient temps I usually start out at about 30 PSI.

Of course, like everyone has said I have them shaved to 4/32" to start and use alot of negative camber in my setup.

Bonster

That's REALLY good to know, Eddie, as I have had a lot of Porsche students lately for some reason. So is this on full treads or shaved? Is this true for just 944s or all Porsches? Would it be true for both the turbo and non-turbo 944s? 944s are front engines, if I've done my homework. So would this target psi tend to also be true for mid or rear engined cars? Most of my students don't run RA-1s but it's still really good knowledge to have under my hat. Thanks!

Bull

I beleive you will find the target pressure to be similar for different models, but the cold starting pressures will vary by car...weight, tire size, engine placement, set-up, etc.

Veloce Raptor

I never worry about hot pressures any more. I take hot tire temps with a probe pyrometer, adjust pressures accordingly, and viola! Perfect GTG set up!

Bonster

Well, here's a bit of irony for you. You know how the psi's that I suggested were apparently too high for Porsches? Well, it worked like a charm in a Corvette Z06 that I instructed (and was "forced" to drive). It's also worked in a number of other cars, actually. However, most of those cars were front engine. Weird. No matter, it's very useful information and I'll remember to ask my Porsche students to start at a cold temp more around 30 from now on and just work from there. Thanks again! This is good information, indeed.

smlporsche

Bonni-

Here's a good setup guide I found a year or so ago for Toyo's..

http://www.toyo.com.au/Pit%20Lane.ht...on%20Pressures

Bull

With MPSCs or Hoosier Daddys, I could never start at 30psi with either of my 993s nor my current car. For days around 80 degrees ambient, I start at around 26-27psi in order to get to 35-36psi. As VR said, the prob pyro is the best for me to get them right.

Astroman

Great link. Thanks.

Bryan Watts

That sounds sorta backwards to me...I make sure that I'm always at the correct hot pressure and then use alignment to get the temps correct across the tire. If the tire is too hot all over, it means you need a harder tire or to adjust the suspension or your driving so that you're not overheating the tire. Race tires can be VERY picky about what pressures you run...a Yoko slick is amazing at 39 psi, and AWFUL at 41.

How are people adjusting tire pressure based on temps? i.e. what sort of temps cause you to make a change on your pressures? Radial race tires are usually stiff enough that pressures don't seem to affect the difference in temperatures across the tire.

Veloce Raptor

Bryan, I am lazy. I have no interest in changing my alignment or camber at the track. Thus, I change tire pressures to get no more than a 10 degree F variation between inner tread, center tread, and outer tread when I come into hot pits at full pace. Seems to work pretty well, and I am getting such even tire wear that I never rotate the tires. I run them until they cord, and they usually cord 3 or 4 at the same time.

For your 2nd question, if, for instance, I see the center tread is 20 degrees higher than inner or outer, I lower pressure on that tire.