Anyone else use Bridgestone RE-11's?
 

Just wondering who else uses Potenza RE-11's and how you like to tailor your tire pressures for Autocross.

I've been told to run higher pressures (in the 35-40psi range) but I've found better luck with the RE-11 around the 25-30psi range. The lowest I've run them so far was 22psi and even then I still wasnt rolling the sidewalls according to the chalk marks.

I always had horribly mushy feel when I ran them that low. I was usually within a couple pounds of 35 on asphalt, 38 on concrete. I've run them in 255/40 two full years in a row. (Around 14 events a year)

My last few events I was dropping pressures each run; started around 35psi and worked my way down to about 25psi over the course of the day and was continuing to get faster. I did notice once I got below 28psi or so the car got a little less predictable, but my times were still getting faster. May have just been me getting more familiar with the course.
I have my first event [of the year] coming up on the 15th so I'll try to maintain 35psi and see how it goes.

No experience with this particular tire, but running any street tire at 22psi sounds unsafe. If it's not rolling over at that pressure you may not be driving to the full potential of the car. If you stay at that pressure, there's the potential for the sidewall to roll over so much it catches and flips the car.

It was only one run and more of a "lets see how stiff these sidewalls are" kinda thing...

Try the reverse to validate your data... start low and work your way higher. If you still get faster through the day then you know that pressure wasn't the factor, familiarity with the course was.

Quite over-dramatic there

There is a reason we tell noobs to put 40psi in their tires for their first autocross. Some people in my region have seen it happen first hand.

It's all fun and games until you have to crawl out of your own car and get help flipping it back over.

Also, I notice a lot of noobs (myself included, when I was in my noob stage) and even some more experienced people like to drop pressures and say that the car feels faster/better/insert improvement here/etc. What is actually happening is they are lowering the effective damping rate (yes, your tire sidewall acts as a damper in a way and is part of the overall suspension picture) of the tire, which makes it feel easier to drive. In general, lowering tire pressure actually reduces total grip available unless your starting pressure was so high that the tire was becoming a torus. See here: http://farnorthracing.com/autocross_secrets12.html

Would be epic if that's what actually happened

Please post a video of someone discussing how low tire pressure could result in flipping the car. Please please please.

It's more likely with a higher profile tire like a 195/60/15. If the pressure is too low and you're driving too aggressive you get an insane amount of rollover onto the sidewall, and then if you hit a bump or dip in the pavement just right that sidewall starts acting like tread and applies a force to the car, which (due to the insane sidewall rollover) is already in a pretty compromised position.

At low pressures on street tires you're also at risk of the tire bead separating itself from the wheel, and this I have witnessed first hand on a Subaru STi. Best case scenario you chew the hell out of the wheel lip. Worst case scenario is your wheel lip finds a bump, expansion joint, etc. Either the wheel breaks or the pavement breaks...if the inertia of the car does not provide enough force for either of those, you flip.

No, it's not super likely, but it isn't far fetched - if someone handed me the keys to autocross their street car on 22psi, I would refuse.

Come on dude...so it's not real unless there's a video on the internet saying it's true? The nice part about the laws of physics is they don't care if you believe it or not.

It is easier to flip a car than you think. That's why we wear helmets.

Sorry, this is a big fat bullshit sandwich you are feeding us.

Yes, yes it is far fetched. If your autocross tracks run on embankments it may be another story, but that would certainly be a special circumstance.

If you've been telling your newbies to run 40lbs of air in their tires to prevent them from tipping then you shouldn't be letting Rav4s and Smart cars into your autocrosses. Your average autocross car doesn't run any amount of measurable risk for what you're saying "isn't far fetched". Give it up.

So you're saying that everyone driving around in their street cars with ~32psi in their tires are constantly on the edge of rolling over?
The absolute worst that will happen is the tire will pop off the bead, and you will destroy a rim and a tire. Saw it happen to an s2000 locally. Can confirm the car did not roll over.

I autocross my Z2s at 28-29psi. Center of gravity and roll centers be damned, she's going over :lol:

So 35psi asphalt/38psi concrete then? :thumbup:

That isn't even close to what I said. Straw man arguments typically come from people who don't understand logic, or who are arguing from a losing position. Which one are you?

Try it out and see how you like it. Did you read the link I posted? As long as the tire doesn't start becoming a torus and lifting the edges off the ground you can add more pressure. If you have some white printer paper you can drive over it to see what your contact patch looks like. Regardless of whether you think a sufficiently rolled over tire can flip a car, the physics of higher tire pressures creating more grip are unchanged.

The car will be harder to drive with higher pressures, because the tire will be less compliant over bumps on the surface. My personal opinion is you should learn to drive this way. I'm not alone in this, I know a few people with multiple national championships under their belt who run higher pressures than everyone else. Maybe they're on to something.

From the site that you quoted (which I revisit every so often)


================

From all this, we can assume the following:

1. A tire will gain grip with increasing tire pressure until the internal pressure overcomes the strength of the carcass portions that keep the tire cylindrical, at which point the tire will start losing grip;
2. A tire with a fairly rigid construction (a DOT-approved tire) will want more total pressure than a tire with a floppy construction (race slick);
3. A wide tire (with a large unsupported beam section across the tread section area) will stand less total pressure than a narrow tire; and
4. A soft tire will need less pressure than a hard tire.

And this is pretty much what is observed in the wild. A wide, floppy, soft, and sticky race slick might use 15 PSI, but a narrow, stiff, hard, and smooth OEM street tire might use 55 PSI.

=============

this is why I'm fairly comfortable running 27~28 psi on a 235 R1R on a 2800 lb car. But will run higher on other tires like the RS3 or ZII




having said that, 22 psi on any street tire is suspicious..... No way that's enough air to support the carcass under comp use, it is bound to deform.

Thanks for all the responses, guys.

That link is awesome! A wealth of information; things I've known to be true but never quite understood until it was all laid out for me. Thanks for that.

While I have several RE-11 driver's in the house, how do you guys feel about doing an AutoX event or two with temps below 40*F? In November when I swapped back to my stock wheels I was noticing that the RE-11 (old 140TW version) was a bit slippery at ambient temps below 40*F...have 3 events in March alone and they're done in a beach parking lot on Long Island's south shore, so temps are generally between 28*F and 40*F for the month of March. Will I be struggling for grip or is one run enough to warm them sufficiently? Can't be worse than the OEM Michelins......can they...?

you're not really gonna have any of the high performance summer tires do well at 40*F, so really, everyone is on equal footing.

the best thing to do for those really cold days is have a smaller section width tire with taller sidewalls, they will heat up quicker

What 7thgear said is about right. Your all seasons will be on equal footing ( I would guess) as the ultra/extreme performance tires get really hard at temps that low, which is why tirerack lists min. temps. Your all seasons may actually be softer at that temp. Funny thing, has anyone tried a performance winter? They will be the softest of the bunch at that temp.

Yeah, the Nokian WRG3 supposedly started as a race tire for such conditions. Very good feedback on my wife's Prius, makes me want to get her better tires for the summer. And makes me wish I had them too, though I just don't drive much if at all in the winter.

I also have our first autocross event of the year this weekend. Temps in Charlotte are going to be around 25 to 37 degrees F. Should be quite interesting!

I am really debating if keeping my OE Michelins on would actually be any better than the RE11As.

Interesting…maybe I'll bring both my OEM Michelins and the RE-11's and do some testing...