RA1 tire press?

[CoryM]

Hey guys.

I've been autoXing the yaris through winter on my very non-performance tires. I am attending a driver training course on Sunday and I am going to throw the 205/50R15 toyo RA1s on for that so I am not held back by tires (also because they will be less noisy than the screaming street tires ;) ).

Anyhow, stock yaris other than roughly -1.0° camber up front. I've been running 42/40psi and the wear looks about right. If I drop the back pressure it starts to get a little tail-happy (although I probably brake later than I should).

Any idea where I should start with the RA1s? They are on 15x6" rims with a 42mm offset.

Thanks.
Cory

[ilikerice]

I would stick to what you're running now. 42/40 is fine. Just check pressures between runs and adjust accordingly. It really is how a person drives. I can not speak for RA1 tires, I have not used them. I run Hankook RS-3 225/45 on a 15x7 wheel. Just my 2 cents. someone can probably speak better

[thebarber]

I ran 38/36 f/r last week on a road course....not tail happy unless I braked while turning

[Blown_xa]

Tire pressure is preference, and varies per tire... Varies by condition of track, and alignment. Best thing to do is start same front and rear. The 42psi may have been fine on the old tires you were on, because they were not performance tires. They have a soft sidewalk, and higher pressure helps... However it is a "band aide" fix for competing on non performance tires IMO.

I run 32 in my front, and 27 in the rear... With my Hankook z214's (cold pressure). A performance tire has stiff sidewalks, so you don't have to jack up the pressure to keep it's shape under load.

My Toyota R1R's were probably most comparable to Ra1's, I ran those 31psi all around. Since you don't have much camber in the front, I would run a bit more to start.

Try 34 all around and go from there. If you are understeering, bump up the rear pressure. If the slalom transitions feel sluggish, bump up the front pressure.

[racerb]

I raced on RA-1s for close to 10 years, although it was with a 1980lb. racecar, our road course pressures varied from as low as 31 to as high as 38 front. With the rear pressures anywhere from 18 to a high of around 32, all dependent on camber, toe, and spring rate. One of the best ways the check for proper pressures on a stock suspensioned car, like our old Showroom Stock racecars, is to simply put a little white shoe polish on the tires edge. Start out around 36-38 front and 32-34 rear and when you come back from a run be it auto-x or road course, see how much if any shoe polish is scrubbed off. If none is gone lower your pressures, if too much is gone like over onto the sidewall raise your pressures. Do all 4 tires and remember these pressures can vary from tire to tire, side to side, front to back.

RA-1s are super forgiving tires, but can sometimes snap loose on you, so work up to speed slowly and find your comfort zone, then try different lines to see what works best for your car and it's performance limits.

racerb

[CoryM]

Thanks guys.
Looks like Sunday is going to be pretty wet so hopefully no hydroplaning.

Cheers.

[ilikerice]

when playing with tire pressure, make sure you use some tire chalk. will help visualize how much sidewall your using. mid 30s seem a bit low for autocross to me. maybe when your tires are cold on your first run, but thats just my opinion. Its trial and error per driver. wet weather is the most fun in autocross. lol. good luck, hope to see some videos

[CoryM]

Threw the toyos on this morning and gave them a quick try. I've never driven on comp tires before so was excited to try.

-Can sure tell the Yaris has no sound insulation in the rear wheel wells. eesh.
-Took longer than I expected to warm up, although could just need to burn off the release agent? Next time may be faster.
-Stock Yaris definitely has some body roll Still feels stable once it flops over but the stickier tires sure make it roll quick.
-They are pretty good so far, but they aren't magic. Can still spin the inside tire and understeer.
-Drove at 42/42psi and still managed to get right to the edge of the tread. I think I will keep the pressures up high to start and see where I go. Steady state cornering felt pretty good.

Regarding wet weather, I live in what would have been a rain-forest. It rains...... a lot. That being said, the winter series had me hoping for rain as my other tires do better in the wet

Thanks again guys.

Cory

[ilikerice]

Yea.. Good to hear..

Only way to clear up that inside wheel spin in slaloms and turns is an LSD. I have tried so many things, my best was removing the front sway bar, but even then.. still spins when really pushing the car to its limits.

Understeer, gonna have to tighten up the rear end a bit. Try the 23mm UR sway bar or the 22mm adjustable sway bar. U can do that in stock class still. Try either upping the PSI in the rear or dropping the front PSI a bit. But I'd recommend the rear sway bar first

[CoryM]

OK, so the day came and went. Ended up being dry and fairly warm (15C ambient or so). Ran the tires at 42/40. I probably could have dropped the rears a bit though. I don't have anywhere near enough neg camber up front for these tires so didn't want to lower the front any.

Anyhow, event went well and I learned a fair bit. It was a bit tricky getting used to being more aggressive with the comp tires, while trying to smooth out my driving. I ended up doing a run I was pretty happy with. A little too fast into the sweeper, but other than that pretty good. The instructor ( a skilled fwd guy who is 2011 FSP Canadian National Champion) did a run with my car and it was nice to see I am driving the car reasonably close to how I should. I was even able to beat his time by around a tenth later on. Although keep in mind he only drove my car for one run, and had a 180lb weight penalty (me!).

Vid of my best run here:
http://www.youtube.com/watch?v=V8UNe...GT3YXn5nyj0ZQ=

Cheers.
Cory