Hi to all:


I was wondering if any one has played with tire pressure to optimize for overall driving and handling. I am currently using the factory settings, and it seems to ok. Has any one got the ultimate balance between front and rear. BTW I am running standard 18 inch.


Thanks

im bumping this.



i got a question too. i have been embarassingly lax at checking the pressure in my tires. went out tonight and whoa! my front tires were at 26lbs and the rears were 30. I am running pretty thin tires on the 20's and the max psi is 50. i cant remember what the shop that put them on recommended but the stock 18's are listed in the door as many of you know at 30 and 37.



what would you that know....suggest i run them at?

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My Cayman may be gone...but not forgotten.

RR don't run them too hard you could bend them. I would contact dealer who sold the to you.
I would guess based on other 40 series tires and rims I had in the passed 28-32 psi would work well.

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I have the standard 18' CS wheels and tires and start out with 33 front and 36 rear for road driving. Increasing the front pressure helps to reduce the push Porsche apparently wants the car to have. I don't drive the car every day, but check tire pressures each day before I drive it.

The recommended pressures for the 19' tires/wheels is 32 front - 37 rear. I would guess that it would be in that neighborhood for the 20'. I usually run 35 front - 38 rear, and along with the re-alignment of the car I did, it works quite well for the road, and has worked well to dial out the understeer, although I don't use the car as a daily driver. For the track or AX I run 40 front - 38 rear (stone cold in the morning), and it seems well ballanced with good sharp turn-in with no rollover on the either front or rear. During the heat of the day and the driving, they com eout to about 43 front and 40 rear.



If you drive the car daily, you should measure your tire pressures at least once a week.



brad


Edited by - beez on 09/11/2006 12:42:28 PM

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21-year PCA Member
PCA DE Instructor

bobporsche,


That's probably a pretty tough question to answer, given thevariety of wheel sizes, tires, car set-up, and local driving conditions (types of roads, ambient temp, etc...) between everyone in the forum. It's also the topicof many discussions around the track.


Your best bet is to get your hands on a pyrometer and get out on the track (well, I guess you can try it on the street as well...). Though some use the laser-style pyrometer, you will get a more accurate reading with the pointy probe-style ones that you can sink into the tread a bit. After driving a bit and getting the tires good and warm, pull over and immediately (before the tires can cool much) use the pyrometer to measure the temperature of at least three spots across the tire to see if theyare roughly equal (or at least progressive from the inside to the outside). A higher temp in the middle will mean that your overinflated and running on a 'bulge' in the center of the tire (though this is sometimes desirable in rainy conditions). An underinflated tire will run on the sidewalls and have higher temps near the outside edges. Either of these scenarios means that you're not maximizing the contact patch between the tire and the road. Adjust the pressure a lb or two to compensate and re-test after another run.

I've been experiencing some vibration around 60-70 mph but goes away after a while. Could this be because my TP is low? I don't think it's alignment 'cause the car drives straight after the vibes go away.

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Mike
2006 Midnight Blue Cayman S

RedRocket,



You and me both! I forgot all about tire pressure since I bought my fancy new gauge!



Thanks for the reminder.



Russ

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I have the same thing. I read in a thread that it has to do with balancing. I had all 4 re-balanced and I'm still experiencing the vibration between 62 and 70. My dealership says it's normal.[img]/fckeditor/editor/images/smiley/MWPX/tounge_smile.gif[/img]

Tire Pressure -- this can vary greatly depending on when you measure it. The air in the tire heats up and expands when the car is run. I believe Porsche recommends checking pressure when cold. Their recommended inflation pressure should be right on and has been accurately relayed at 32f and 37r.


Vibration -- if you are like me, you park you car on a cold concrete slab everyday. It may sit there for a couple of days as well, but at least over night. When you take it out for a drive, the spot that was made flat by a few thousand pounds weighing down on it, and cold by the concrete, retains a little of its' deformation. That is until the tire heats up (see above).This can cause a vibration in your steering wheel. Balance, allignment, debris, inflation pressure, (I'm sure I'm leaving something out) can all cause steering wheel vibration and should all be monitored. I would suggest that if you are not consistently getting your vibration, that this is likely the culprit. Lastly, some one once explained to me that all cars have a transition speed, where different aerodynamic shifts occur as the air volume created by speed has to be shifted to a different flow around the body (car). During this transistion, the air can't make up its' mind which way to flow. The back and forth battle can cause a vibration. Maybe 60-70 mph is that point on the Cayman. It would seem we would all have the same issue if that were the case ans I definately don't experience it. Somebody gave a great explaination of CdA in another thread, maybe they can chime in on this.

Fadiboy, I think you hit the spot. I park my Cayman on my uphill driveway every night so your explanation does make sense to me.

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Mike
2006 Midnight Blue Cayman S

porsche does recommend on 18's ........30f and 37r. Does 32psi in front improve handling?