Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Forums > 1- Porsche Technical Forums > Porsche Autocross and Track Racing


Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
jmz jmz is offline
Registered User
 
jmz's Avatar
 
Join Date: Feb 2003
Location: Taylor Lake Village, TX
Posts: 2,411
Garage
Any thoughts on tire pressure for Hoosier R7?

I cannot run anywhere near the recommended pressures from Hoosier without the car feeling like it is on ice. First time out I started at 22 with a target of 27. This past weekend I backed it down to a hot target of 25 and it seemed like they held up better during the 20 and 25 minute session but I'm still not sure I have it right.

Any thoughts? Car is a 914/6 GT at about 2100lbs without driver.

__________________
Jay
'74 Mexico Blue 911 3.0 EFI (Fast and Loud)
'70 914/6 Race Car (Faster and Louder)
'80 911SC Weissach 3.2 Short Stroke Hot Rod.
'71 Alden Caravelle 42'(Slow and Quiet)

Last edited by jmz; 12-13-2017 at 06:27 AM..
Old 12-12-2017, 05:38 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
jmz jmz is offline
Registered User
 
jmz's Avatar
 
Join Date: Feb 2003
Location: Taylor Lake Village, TX
Posts: 2,411
Garage
Am I the only one running these?
__________________
Jay
'74 Mexico Blue 911 3.0 EFI (Fast and Loud)
'70 914/6 Race Car (Faster and Louder)
'80 911SC Weissach 3.2 Short Stroke Hot Rod.
'71 Alden Caravelle 42'(Slow and Quiet)
Old 12-13-2017, 04:27 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)
jmz jmz is offline
Registered User
 
jmz's Avatar
 
Join Date: Feb 2003
Location: Taylor Lake Village, TX
Posts: 2,411
Garage
...Jeff at Hoosier is very helpful. I called and got some guidance but I'd still like to hear from anyone with experience here.

Cheers,
__________________
Jay
'74 Mexico Blue 911 3.0 EFI (Fast and Loud)
'70 914/6 Race Car (Faster and Louder)
'80 911SC Weissach 3.2 Short Stroke Hot Rod.
'71 Alden Caravelle 42'(Slow and Quiet)
Old 12-13-2017, 06:45 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)
Registered User
 
Pete R's Avatar
 
Join Date: Oct 2010
Location: New Hampshire
Posts: 2,331
Garage
I use them. I have a 3000lb fwd car. I have had good luck running the recommended hot pressure about 39-40. I think they are actually better at the higher pressure. I used to run them a bit lower (-5lbs) but I ended up at Watkins Glenn this year. I was worried about an under inflated tire through the esses at 100+ MPH so I pumped them a bit more. The car felt better to me and the wear is even so I'm going to stay there.
__________________
1979 928 85 Euro 2v motor,S4 Brakes and suspension, 1988 951 street legal track car(sold)
Neon SRT4 track car
Old 12-13-2017, 10:05 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)
Registered User
 
HarryD's Avatar
 
Join Date: May 2002
Location: Portland, Oregon
Posts: 9,657
Jay, I do not know the answer but a tire pyrometer will help you get to the correct place. You want the tires to be at the recommended temperature and even across the tread.

I have this one: https://www.amazon.com/Joes-Racing-54005-Pyrometer-Adjustable/dp/B005JVFTTM
__________________
Harry
1970 VW Sunroof Bus - "The Magic Bus"
1973.5 911T Targa - "Smokey"
2003 BMW Z4 3.0i
2009 MB C300
Old 12-13-2017, 09:12 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #5 (permalink)
Racer
 
winders's Avatar
 
Join Date: Oct 2010
Location: San Martin, CA
Posts: 3,662
Quote:
Originally Posted by HarryD View Post
You want the tires to be at the recommended temperature and even across the tread.
Only if you can measure the temps in real time......you can't with a pyrometer. If you measure and the temps are the same across the tire the inside part is not hot enough.
__________________
Scott Winders
PRC GTL #3
Old 12-14-2017, 11:12 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #6 (permalink)
Registered User
 
HarryD's Avatar
 
Join Date: May 2002
Location: Portland, Oregon
Posts: 9,657
Quote:
Originally Posted by winders View Post
Only if you can measure the temps in real time......you can't with a pyrometer. If you measure and the temps are the same across the tire the inside part is not hot enough.
Winders. Really? If you use a proper pyrometer like the one I posted, you do get the proper readings since it pushes a probe into to rubber at each point.

If you use one of the IR types then you are correct as they only measure surface temperature and you are never sure exactly which part you are measuring.
__________________
Harry
1970 VW Sunroof Bus - "The Magic Bus"
1973.5 911T Targa - "Smokey"
2003 BMW Z4 3.0i
2009 MB C300
Old 12-14-2017, 11:23 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #7 (permalink)
Registered User
 
Join Date: Jul 2016
Posts: 20
we run around 34 on our 87 911.

These tires are designed to run at higher pressures.
Old 12-16-2017, 03:40 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #8 (permalink)
Racer
 
winders's Avatar
 
Join Date: Oct 2010
Location: San Martin, CA
Posts: 3,662
Quote:
Originally Posted by HarryD View Post
Winders. Really? If you use a proper pyrometer like the one I posted, you do get the proper readings since it pushes a probe into to rubber at each point.

If you use one of the IR types then you are correct as they only measure surface temperature and you are never sure exactly which part you are measuring.
Really!!

Think about it. With the camber we run these days with radial tires only the inside third of the tire is on the ground unless we are cornering. As soon you stop corning the outside 2/3rds of the tire is starting to cool...even the tread below the surface.
__________________
Scott Winders
PRC GTL #3
Old 12-16-2017, 04:50 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #9 (permalink)
Registered User
 
HarryD's Avatar
 
Join Date: May 2002
Location: Portland, Oregon
Posts: 9,657
Quote:
Originally Posted by winders View Post
Really!!

Think about it. With the camber we run these days with radial tires only the inside third of the tire is on the ground unless we are cornering. As soon you stop corning the outside 2/3rds of the tire is starting to cool...even the tread below the surface.
Funny, I see them used in all sorts of tracks.

I know these guys may know a thing or two about about such things:
https://www.elephantracing.com/tech-topics/reading-tire-temperature/

Or perhaps these fellows:
http://www.hoosiertire.com/images/content/files/TCTR7_A7.pdf

But believe what you wish. OK by me.
__________________
Harry
1970 VW Sunroof Bus - "The Magic Bus"
1973.5 911T Targa - "Smokey"
2003 BMW Z4 3.0i
2009 MB C300

Last edited by HarryD; 12-16-2017 at 06:29 PM..
Old 12-16-2017, 06:21 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #10 (permalink)
Registered User
 
Join Date: Apr 2003
Posts: 122
Ditto what Winders said. Infrared or a direct probe, doesn't change the fact that going in a straight line a cambered tire's inner shoulder stays hot from the uneven load/flex, while the outside cools. You want linear temps not even. And don't trust everything you read on fancy websites, talk to the actual people that actually race ;-)

Spec 911 just started running the R7, 2350 lbs with driver and everyone seems to like around 33-35psi.
Old 12-18-2017, 09:36 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #11 (permalink)
jmz jmz is offline
Registered User
 
jmz's Avatar
 
Join Date: Feb 2003
Location: Taylor Lake Village, TX
Posts: 2,411
Garage
Interesting that the 914 driver feedback I've received considerably lower than what is being reported here which is inline with what I was feeling. ...24-27 hot seems to be the consensus that I received on the 914world forum.
__________________
Jay
'74 Mexico Blue 911 3.0 EFI (Fast and Loud)
'70 914/6 Race Car (Faster and Louder)
'80 911SC Weissach 3.2 Short Stroke Hot Rod.
'71 Alden Caravelle 42'(Slow and Quiet)
Old 12-19-2017, 05:56 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #12 (permalink)
Registered User
 
Cory M's Avatar
 
Join Date: Oct 2004
Location: San Diego
Posts: 3,574
We run them near the Hoosier recommended range on our 2450 pound 911, 33-37 pounds depending on conditions and age of the tires, usually around 2 pounds more in the rear.
Old 12-19-2017, 08:06 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #13 (permalink)
Registered User
 
HarryD's Avatar
 
Join Date: May 2002
Location: Portland, Oregon
Posts: 9,657
Quote:
Originally Posted by Phil Gilsdorf View Post
Ditto what Winders said. Infrared or a direct probe, doesn't change the fact that going in a straight line a cambered tire's inner shoulder stays hot from the uneven load/flex, while the outside cools. You want linear temps not even. And don't trust everything you read on fancy websites, talk to the actual people that actually race ;-)

Spec 911 just started running the R7, 2350 lbs with driver and everyone seems to like around 33-35psi.
Agreed that interpreting the results is the big deal.

For I, who Autocrosses, I find that trying to get a flat temperature profile works best.
__________________
Harry
1970 VW Sunroof Bus - "The Magic Bus"
1973.5 911T Targa - "Smokey"
2003 BMW Z4 3.0i
2009 MB C300
Old 12-19-2017, 12:49 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #14 (permalink)
Administrator
 
Jack Olsen's Avatar
 
Join Date: Feb 2000
Location: Los Angeles
Posts: 13,099
Right. There's nothing wrong with using a probe-type pyrometer, but (as Winders points out), as soon as you head into the pits, your outside half is going to be cooling down faster than the inside half. Especially if you're checking your own temps, you have to adjust your results for the change -- you won't want to see the same temps outside/middle/inside anymore, but something that reflects having been in the neighborhood a short time ago.
Old 12-20-2017, 10:28 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #15 (permalink)
Reply

Thread Tools
Rate This Thread
Rate This Thread:

 


All times are GMT -8. The time now is 09:14 PM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.