Please help - Tire Pressure question

[kenchan]

hi guys. it's my first time using TR-Rated tires in 215/45/17 size. these are Bridgestone RE910's. it says that the max pressure it can handle is 40psi. I'm using 35psi right now (at cold) but not sure how much more psi I can put in w/o bursting it when it's hot. please let me know recommendations and or setup. I wanna try to feed it a little more psi since it squeels a tad on the corners especially with 3 people on board the P11. what is the max? ambient temperature is about 83F right now with strong sunlight.

on my ZR tires (same 215/45/17's) I use 37.5psi since the max is 44psi.

thanx for your input

[P10DET]

You don't say how wide your wheels are, and that is a factor. I would definitely not go higher than where you are at. I run 35/32 on my P10, but that's because I have a 205 tire on a 7.5" wide wheel. On my B13 with 215 tires on 7" wheels, I run the factory recommended tire pressures of 31/29.

The wider tires don't necessarily require a higher pressure. I think that's a bit of misinformation that is out there. You know, common knowledge that is wrong.

Some tires squeal, and some don't. You can't really change that with tire pressures.

The Summitomos I have on my P10 did very little squealing on the Summit Point Jefferson Circuit. I was amazed how quiet they are. I've had other tires that squeal like Ned Beatty in Deliverance. :right: My Yokohama A520s squealed like that when new. The Yoks are a much better tire though IMHO.

So, don't raise the pressures. If you have a 7" wide wheel, I'd recommend lowering the pressures. In fact, what little tire pressures affect squealing, it may actually help because you will increase the tire's footprint.

[kenchan]

thanx for the info. my wheels are 17x7's.

[G22DET]

37.5psi sounds really high, you might want to get it down to liek what P10DET said..around 30-32.
on the track, psi can raise as much as +10 for the summis that I had...i usually run 28psi cold...it raises to abut 34-36 which is ideal for the HZR II....but i dont like the tires anymore...not grippy enough...

[Kenny-G]

this is what I do after I upgrade my stock size to 205-55-15:

Set the tire pressure to a point which it "looks" right to you, then drive it for about 15 min ( without fast corning ), then put your hand across the tires to feel for the tempeture. If the center is cooler than the sides that tire pressure is too low, center is warmer than the sides then pressure is too high. If you get to the point when the tempeture feel about the same, your tire pressure would be about right. On mine I find that 40/35 to be the best.

[primera man]

37.5 seems high to me.
When i had this size tyre on another car i had the tyre people tell me i should only need between 30-32 max in them.

[P10DET]

Originally posted by Kenny-G
this is what I do after I upgrade my stock size to 205-55-15:

<snip>

On mine I find that 40/35 to be the best.

That's way high. I'll bet you a 6pack of Shiner Bock (best damned beer in North America ) that you will wear the center of your tread out prematurely.

[Kenny-G]

no it is not. The factor is...if you have two different brand of tires, even if the size is the same, the width of the contect patch may not be the same. So different tires can take different tire pressure. On mine ( Potenza RE730 205-55-15 ), after I put them on and set pressure to factory, I found that ride was "sloppy" until I set them to 40/35 ( I set the front 5psi higher than the back to get better balance on high speed turning ) I use this set-up for 15000 miles now and tires worn pretty evenly. And I am happy enough with this set-up and consider about not upgrade my wheels to 17 for the ride issue.


Is Shiner Bock the best beer in North America? How come I never heard of it?

[P10DET]

Originally posted by Kenny-G
no it is not. The factor is...if you have two different brand of tires, even if the size is the same, the width of the contect patch may not be the same.

I'll still bet that 6 of Shiner Bock.

Originally posted by Kenny-G
I am happy enough with this set-up and consider about not upgrade my wheels to 17 for the ride issue.

What ride issue? If you are thinking harsher ride, that's hooey. When I went to 215/40-16 on my SE-R (from 185/60-14) there was no degradation in ride quality.

When I went from 195/60-14 on my P10 to 205/40-17, not only was there no degradation in ride quality, a friend of my wife thought the ride was better. Now, my wife isn't an enthusiast and would be very honest about ride quality, and her friend even moreso. So, it's not just me saying so.

Low profile tires causing a harsh ride is very old school. Modern ultra low profile tires are not harsh. I'm sure it depends upon the tire, but most 40 profile tires are modern designs and as such are not harsh.

Originally posted by Kenny-G
Is Shiner Bock the best beer in North America?

You betcha!

Originally posted by Kenny-G
How come I never heard of it?

Can't help you there.

It's a regional beer, but some of the SE-R guys in SoCal have been getting it. In fact, the hotel for the SE-R National Convention in Washington, DC had it. You might have to really look for it. Yum yum.

[kenchan]

for those of you dat say 37.5 is too high, it wasn't out of the ordinary for canyon carvers in the malibu mountains to use this psi on their ZR tires. there were others using 39psi (cold).

the RE910's (TR-rated) are on my P11 and using 34psi. anythine less seems to be sloppy on the corners. I measured the psi a couple days ago and it was 32-33psi. but again, not sure could be dat it's just a cheap tire, so the sidewalls just don't have wat it takes to be a performance tire. just worried about it bursting... anyone ever burst a tire from over pressure?

thanx,

[P10DET]

Originally posted by kenchan
for those of you dat say 37.5 is too high, it wasn't out of the ordinary for canyon carvers in the malibu mountains to use this psi on their ZR tires. there were others using 39psi (cold).

the RE910's (TR-rated) are on my P11 and using 34psi. anythine less seems to be sloppy on the corners.

Good gravy, that's as high as we go with our SCCA ITS SE-R. This is a dedicated race car that is turning into turn 1 at 125 mph! It also is with 205/60-14 tires on 7" wheels.

At the SE-R National Convention, I ran 40/38, but that is lapping at 9/10 on a race track. I think that's way too high for normal street driving.

The sloppiness you are talking about is probably just turn-in. Some tires turn in more directly than others. Some just feel better than others. But, that is only part of the handling equation. You are probably giving up some ultimate grip. The turn-in feels better at higher pressures because the sidewall doesn't flex as much.

[kenchan]

humm...oh ya? hummmm... so I should use like 32psi? confused: it felt so sloppy though on the corners squealing and stuff. at 34psi, doesn't do either.

[P10DET]

Originally posted by kenchan
humm...oh ya? hummmm... so I should use like 32psi? confused: it felt so sloppy though on the corners squealing and stuff. at 34psi, doesn't do either.

Well, ever set-up is different. You may indeed be correct, but it would surprise me. Be sure what you feel as sloppiness isn't just turn-in. That is what I suspect, and as I said, some are more direct than others.

What tires are you using?

I've read articles where drivers felt sure one thing was faster than another (such as you are experiencing with your car at higher pressures) and in fact it wasn't. It just felt better.

I'm not going to deny what you are experiencing. You're there and I'm not. Just be sure you can differentiate between all the things the car is doing.

Also, some of my response is for the benefit of others who are reading. On a public forum, sometimes you have to consider how others may use the info.

So, what I'm saying is you may be correct, but I suspect it may just be the tires. I've been wrong before though.

:jump:

[kenchan]

so basically wat you're saying is that you don't know wat the hell ya talking about. ghaahahhaa!!! j/k

ok, so here it is. zr tire 37.5psi good, hot weather still good.

tr tire 34psi- probably kinda high, going to lower to 33psi all around.

:frog:

[P10DET]

Originally posted by kenchan
so basically wat you're saying is that you don't know wat the hell ya talking about. ghaahahhaa!!! j/k

ok, so here it is. zr tire 37.5psi good, hot weather still good.

tr tire 34psi- probably kinda high, going to lower to 33psi all around.

Basically I'm covering my a$$. :jump:

TR vs ZR speed rating doesn't matter.

I'd be really surprised if 37.5 psi was really a good pressure. I cannot say that you are wrong since I haven't tested your set-up. But, I'm more inclined to believe your tires are sloppy on turn-in and that is why the higher pressure feels good to you.

You didn't answer what tires you are using.