03-25-2015, 06:15 AM
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#1
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Registered User
Join Date: Oct 2014
Location: Fort Collins, Co.
Posts: 74
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Air pressure
I have an 01 S model with the 18" staggered wheel option. My question is what do you guys do for air pressure? I know the plaque says 29 front and 36 rear but with the extra load tires that are so common in these sizes that still feels like a lot. There is ZERO sidewall bulge at that pressure and the front end feels nervous. Has anybody experimented with lower pressures? Thanks
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03-25-2015, 07:34 AM
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#2
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Registered User
Join Date: Jun 2012
Location: Little Switzerland, north carolina
Posts: 551
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Quote:
Originally Posted by bwillia080261
I have an 01 S model with the 18" staggered wheel option. My question is what do you guys do for air pressure? I know the plaque says 29 front and 36 rear but with the extra load tires that are so common in these sizes that still feels like a lot. There is ZERO sidewall bulge at that pressure and the front end feels nervous. Has anybody experimented with lower pressures? Thanks
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If anything, I put in a couple pounds more. I think with less you are going to see uneven wear from the sides and middle. My wheel man says a little extra helps keep from bending a rim on the many potholes we seem to have also. Not much rubber there for cushion.
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03-25-2015, 07:41 AM
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#3
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Registered User
Join Date: Aug 2013
Location: Ottawa, ON
Posts: 452
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I run about 30/31 in the front and 38/39 in the rears
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DrCactus
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03-25-2015, 08:03 AM
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#4
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Registered User
Join Date: Dec 2012
Location: Jackson Hole, Wyoming
Posts: 800
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I have the same size rims. I like 30 F/34 R.
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03-25-2015, 08:06 AM
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#5
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Registered User
Join Date: Oct 2013
Location: San Jose, CA
Posts: 583
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Quote:
Originally Posted by bwillia080261
I have an 01 S model with the 18" staggered wheel option. My question is what do you guys do for air pressure? I know the plaque says 29 front and 36 rear but with the extra load tires that are so common in these sizes that still feels like a lot. There is ZERO sidewall bulge at that pressure and the front end feels nervous. Has anybody experimented with lower pressures? Thanks
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I like the numbers posted here. I go a little higher for daily driving as well. AX and Track days, whole different story!! I assume you ARE talking street driving, not racing pressures...
__________________
2000 S - Borla Exhaust, TS Cat Deletes, RSS UDP, B&M Short Shift, T96 Steering Wheel, Potenza RE-71R's,
Mantis 2.0L Deep Sump, de-snorkeled, Bilstein PSS9 Coil-Overs, Rennline lug studs, and auto crossed regularly.
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03-25-2015, 08:07 AM
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#6
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Registered User
Join Date: Oct 2013
Location: San Jose, CA
Posts: 583
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Quote:
Originally Posted by Joe B
I have the same size rims. I like 30 F/34 R.
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Joe - not to get off topic, but what are the rim sizes on your 18's?
thanks!
__________________
2000 S - Borla Exhaust, TS Cat Deletes, RSS UDP, B&M Short Shift, T96 Steering Wheel, Potenza RE-71R's,
Mantis 2.0L Deep Sump, de-snorkeled, Bilstein PSS9 Coil-Overs, Rennline lug studs, and auto crossed regularly.
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03-25-2015, 08:26 AM
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#7
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Registered User
Join Date: Sep 2012
Location: S. New Jersey
Posts: 1,239
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I have tried up and down, winter time summer time
I have settled on the recommend 29/36 on my 18" staggered.
Tires wearing evenly
+ psi harsher ride
- psi a bit squirmy
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2002 S - old school third pedal
Seal Grey
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03-25-2015, 08:53 AM
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#8
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Registered User
Join Date: Jan 2014
Location: Albuquerque, NM, USA
Posts: 730
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It's my personal policy to never have less than 30 psi in any tire on any vehicle.
Therefore I do 30 and 36.
This said, there really is little reason to doubt the Porsche recommendation.
__________________
Kent Christensen
Albuquerque
2001 Boxster
2007 GL320 CDI, 2010 CL550
2 BMW motorcycles
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03-25-2015, 10:42 AM
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#9
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Registered User
Join Date: May 2011
Location: Johnstown, PA
Posts: 195
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Quote:
Originally Posted by lkchris
It's my personal policy to never have less than 30 psi in any tire on any vehicle.
Therefore I do 30 and 36.
This said, there really is little reason to doubt the Porsche recommendation.
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yup, 30/36 here.
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03-25-2015, 11:06 AM
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#10
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Registered User
Join Date: Dec 2012
Location: Jackson Hole, Wyoming
Posts: 800
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Quote:
Originally Posted by Dlirium
Joe - not to get off topic, but what are the rim sizes on your 18's?
thanks!
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Well, I know the rears are 18x10, and although I'm pretty sure the fronts are 18x8, I'm not near the car to check, and I'm not positive. 225/18 F and 265/18 R tires (I remember that much). They're the 996 Carrera 5-spokes, optional on the 2003 Boxster S.
Last edited by Joe B; 03-25-2015 at 11:08 AM.
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03-25-2015, 11:25 AM
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#11
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Need For Speed
Join Date: Feb 2013
Location: Funville
Posts: 2,112
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Quote:
Originally Posted by Joe B
Well, I know the rears are 18x10, and although I'm pretty sure the fronts are 18x8, I'm not near the car to check, and I'm not positive. 225/18 F and 265/18 R tires (I remember that much). They're the 996 Carrera 5-spokes, optional on the 2003 Boxster S.
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Did your car come with those wheels or did you buy them and install them? For the Boxster the Carerra Light wheels are Fronts 18 x 7.5 Rears are 18 x 9. The size you posted are from the wheels used on the Carerra.
__________________
2003 Boxster S
| 987 Air Box | K&N Air Filter | 76mm Intake Pipe| 996 76mm TB | 997 Distribution T | Secondary Cat Delete Pipes | Borla Muffler | NHP 200 Cell Exhaust Headers |
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03-25-2015, 02:21 PM
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#12
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Registered User
Join Date: Dec 2012
Location: Jackson Hole, Wyoming
Posts: 800
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Previous owner installed them.
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03-25-2015, 02:38 PM
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#13
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Registered User
Join Date: Oct 2013
Location: San Jose, CA
Posts: 583
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Quote:
Originally Posted by KRAM36
Did your car come with those wheels or did you buy them and install them? For the Boxster the Carerra Light wheels are Fronts 18 x 7.5 Rears are 18 x 9. The size you posted are from the wheels used on the Carerra.
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ah - that is what I was looking for. So 18" wheels on a Boxster as a factory option was 7.5" wide in front and 9" wide in back...great!
I'm trying to figure out if my wheels on my 2000 S are stock or not!!
__________________
2000 S - Borla Exhaust, TS Cat Deletes, RSS UDP, B&M Short Shift, T96 Steering Wheel, Potenza RE-71R's,
Mantis 2.0L Deep Sump, de-snorkeled, Bilstein PSS9 Coil-Overs, Rennline lug studs, and auto crossed regularly.
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03-25-2015, 08:04 PM
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#14
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Certified Boxster Addict
Join Date: Nov 2010
Location: Los Angeles
Posts: 7,669
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The stock tire pressures were defined to ensure that the car has understeer and not oversteer. This is also the reason for the staggered tire widths (narrow in front, wider in rear).
Thus, generally the goal of tire pressure changes to a stock Boxster is to decrease the amount of understeer inherent in the design. To achieve this, slightly increase the front pressure and decrease the rear pressure. 31 front and 33 rear is a good starting point.
__________________
1999 996 C2 - sold - bought back - sold for more
1997 Spec Boxster BSR #254
1979 911 SC
POC Licensed DE/TT Instructor
Last edited by thstone; 03-25-2015 at 08:08 PM.
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03-25-2015, 08:17 PM
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#15
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Registered User
Join Date: Apr 2014
Location: new orleans
Posts: 249
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the vehicle's manufacturer's recommended inflation is to provide you with the optimal straight line braking for the car, lessening the potential for a collision. of course when you are looking for other optimal characteristics the pressures will vary, but the short line braking is the factor which incurs the highest amount of liability to the manufacturer.
__________________
2005 Porsche Boxster S, 2000 Porsche Boxster 2.7L Base, 2000 Mazda Miata LS Supercharged, 2010 Toyota Tacoma TRD Off Road
Previous Vehicles: 2005 Ford Mustang GT, 1986 Alfa Romeo Spider, 1971 Alfa Romeo GTV, 1999 Ford Mustang
1977 Toyota Celica GT
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03-26-2015, 10:48 AM
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#16
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Registered User
Join Date: Oct 2014
Location: Fort Collins, Co.
Posts: 74
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Quote:
Originally Posted by Dlirium
I like the numbers posted here. I go a little higher for daily driving as well. AX and Track days, whole different story!! I assume you ARE talking street driving, not racing pressures...
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Yes, absolutely, just street driving.
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