Toyo tire pressures

[Jack Olsen]

Got a track day on Monday, and I'm using R-compound rubber for the first time.

What's a good starting (cold) air pressure for Toyo Proxes RA-1 tires on 7x8x16 Fuchs on an early car? How high should
the pressures get on a track with 85-degree ambient temps?

Thanks.


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Jack Olsen
My Rennlist page • My Pelican Gallery page • My Porsche Owners Gallery page

[campbellcj]

Jack,

I have zero experience with the Toyos, but with the Kumhos and Hoosiers, 40psi hot seems to be a good target. This means starting around 30-34psi cold.

Somebody might have a pyrometer you can borrow to take some temp readings. That's the best way to home in on the right pressure (and camber) settings. I've got one on order but it won't be here in time.

I will be really happy if it's only 85 out there Monday...last time I was at the Streets (a couple weeks ago) it was well over 100 I think.



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Chris C.
73 914 2.0
70 911E Targa
campbell.chris@gte.net

[Clark Griswald]

I haven't run the Toyos either but I have run Kumhos DOT R, which should be similar.

You didn't identify the tire width. That will make a difference. In general the wider the tire, the lower the ideal pressure at that end (recall earlier tombs about tire width / contact patch size).

Assuming your running 225 front and rear, I would initially target a hot pressure of 30 front, 35 rear. If you are running wider rear rubber, go a little lower in back. Start about 8 lbs lower when cold.

[tobluforu]

Om my 72, i was running 31, 35 cold. Listened to randy well's advice and lowered them 5lbs all a round. Much more grip now. These are on r compound tires.

[Jack Olsen]

Thanks. I'll try starting out on the low side, maybe 27/30, and I'll chalk the things to get an idea of how I'm doing.

Chris, I've got a pyrometer, which I'll bring. But I've never used it to check the tires. Anybody care to share the procedure?

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Jack Olsen
My Rennlist page • My Pelican Gallery page • My Porsche Owners Gallery page

[This message has been edited by JackOlsen (edited 10-14-2001).]

[campbellcj]

Originally posted by JackOlsen:
I've got a pyrometer, which I'll bring. But I've never used it to check the tires. Anybody care to share the procedure?

Here's one write-up on pressures & temps -

http://www.turnfast.com/tech_handling/handling_pressure2.lasso

HTH,
Chris

[Drew_K]

Jack, please share any insight about tire pressures after you run the tires. I'm having Toyo RA1's mounted on my extra rims tomorrow and am very curious about a good pressure for front and rear.

[Lawson]

I have the toyos on with 225's in front and 245's in back on a 78sc. I have been running 35psi cold on all 4 tires which gives me 40psi hot. The handling is well balanced with those pressures.

[Jack Olsen]

After a 90 minute drive to the track, I lowered the cold pressures to 28F/31R. After the first session on the track, I checked hot pressure: 38F/44R. I vented the rears down to 41, and it seemed to work very well at that level for the rest of the day.

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Jack Olsen
My Rennlist page • My Pelican Gallery page • My Porsche Owners Gallery page

[This message has been edited by JackOlsen (edited 10-15-2001).]

[Jack Olsen]

I'll also say it in pictures. Click a thumbnail for a larger version.

Here's the Toyos on the car:



Why is it so dirty? Well, here's a clearer view of how the car looked after I asked an instructor to see if he could find the limits of the tires -- and we ended up spinning off the track:



Note the reverse-rooster-tail pattern on the side. That's from spinning and shooting backwards over the desert.

Check out that 67 912 next to me, though. Nice.

And here's what the new tires helped produce. My previous best time at Willow Springs had been a 1:46. New rubber meant a full three seconds quicker around the track:



And here's the happy owner with his stealth-fighter-styled 911 (and a bad case of helmet hair):



I got to meet fellow Pelicanite Chris Campbell at this event. A really nice guy. I don't have pictures of his 914, but I do have it in video, I think. In a few days I'll try to post it.

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Jack Olsen
My Rennlist page • My Pelican Gallery page • My Porsche Owners Gallery page

[This message has been edited by JackOlsen (edited 10-15-2001).]

[Saffs]

Very cool, Jack.
Sounds like a great day....


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'75 911S Targa
'81 BMW Alpina C1 2.3

[campbellcj]

In typical fashion, I shot a few pics yesterday too:
http://www.nosubstitute.org/events/TracQuest15Oct01

I just couldn't bring myself to shoot any pics of BB after she'd been "soiled"

Great day...this stuff sure is addicting!

Chris C.
73 914 2.0
70 911E Targa
campbell.chris@gte.net

[This message has been edited by campbellcj (edited 10-16-2001).]

[CamB]

Chris or JAck

How well did the 912 run - I am always curious as to how a light, low 912 (or, say, my 69T - not an aweful lot more power) would go on the track?

I do plan to do my own, ah, research on that, of course.

Cam

[campbellcj]

Originally posted by CamB:
Chris or JAck

How well did the 912 run - I am always curious as to how a light, low 912 (or, say, my 69T - not an aweful lot more power) would go on the track?

I do plan to do my own, ah, research on that, of course.

Cam

We weren't being formally timed (this was a pure "DE" event) so it's hard to say, but he did seem to have a great time and do well out there. The car was running lower profile (than stock) Kumhos IIRC, which makes a BIG difference. Not sure if it had any suspension mods. Nice little 912.



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Chris C.
73 914 2.0
70 911E Targa
campbell.chris@gte.net

[motion]

OK Jack - What does your license plate read?

Chris - nice pictures. The engine compartment on the Modena makes me go ga-ga. Is that upholstery on the sides? Unbelievable.

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Let's Roll!
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-Richard
'84 Carrera Cabriolet
'74 911 Widebody 3.6 Project

[tobluforu]

So, what tire pressures did you end up using? What did you and the instructor think about the toyo's?
I bet for a split second there you were thinking the worse. I spun my 72 at sears during a nasa event. Ended up about 6 inches from the tires. All I thought there for a second was there goes my car..

[BRAINIAC]

1:43! Nice job Jack! Wish I coulda been there.

Wonder why it's always instructors that take the car on Safari. Let me guess. It was turn 9, right?

I just did a non-PCA auto-X on race tires for the first time. It made the car stick so well that my suspension now feels like mush. Since the event, I cranked in more negative camber due to some handling problems with the higher G's generated by the new rubber. Did you experience any of this?

It seems that with more corner power comes more body roll. (Naturally) More body roll means more camber loss. I'm sure you didn't have as much of a problem since you are set up pretty damn stiff already.
But I bet you'd benefit even more from some more aggressive alignment specs to fully utilize that race rubber. Your camber looked pretty tame last time I saw it.

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Tyson Schmidt
72 911 Cabriolet
92 C-2 Cabriolet