tire PSI- what PSI to use, side wall or door badge/ factory

ssnsltd · #1 12-10-2007, 02:43 PM

I have a set of /falken ZE912's and a set of Ecasta's for my SVX'x. I only have a few miles on the Ecastas, the ZE912's go on tommorrow.

the MAX PSI on both tires is 51 psi. I think that is a bit high, but I have always gone with max PSI on the side wall. the tire web site kinda waffles around with an answer but does't come right out and say anything specific.

anyone have an educated opinion on the subject -?

thanks!
david

SubaSteevo · #2 12-10-2007, 03:05 PM

Quote:

Originally Posted by ssnsltd

I have a set of /falken ZE912's and a set of Ecasta's for my SVX'x. I only have a few miles on the Ecastas, the ZE912's go on tommorrow.

the MAX PSI on both tires is 51 psi. I think that is a bit high, but I have always gone with max PSI on the side wall. the tire web site kinda waffles around with an answer but does't come right out and say anything specific.

anyone have an educated opinion on the subject -?

thanks!
david

Max PSI is exactly that, the maximum safe amount. You should NEVER fill a tire to the max as the air will expand as it heats.

I usually kept the tires around 36/32, I believe the factory specs are 33/28.

SVeXy96 · #3 12-10-2007, 03:16 PM

Quote:

Originally Posted by SubaSteevo

Max PSI is exactly that, the maximum safe amount. You should NEVER fill a tire to the max as the air will expand as it heats.

I usually kept the tires around 36/32, I believe the factory specs are 33/28.

Close! Its 33/29 which is what I keep my tires at all the time

Crazypolo95 · #4 12-10-2007, 04:55 PM

i have the SPT ones of thise but in 235/45/17 with the PSi at front 36 back 34

Quote:

Originally Posted by ssnsltd

I have a set of /falken ZE912's and a set of Ecasta's for my SVX'x. I only have a few miles on the Ecastas, the ZE912's go on tommorrow.

the MAX PSI on both tires is 51 psi. I think that is a bit high, but I have always gone with max PSI on the side wall. the tire web site kinda waffles around with an answer but does't come right out and say anything specific.

anyone have an educated opinion on the subject -?

thanks!
david

svxistentialist · #5 12-10-2007, 05:51 PM

Quote:

Originally Posted by SubaSteevo

Max PSI is exactly that, the maximum safe amount. You should NEVER fill a tire to the max as the air will expand as it heats.

I usually kept the tires around 36/32, I believe the factory specs are 33/28.

I'm totally with Steevo on this.

I keep mine on 35-31 or 36-32. Factory specs are too soft. It allows the car to wallow on the side-walls. Plus it makes the steering heavy for parking. Plus it wears the outsides of the tire tread.

Run 3 to 5 lbs harder than spec. No penalty, better mpg. No-brainer.

Joe

Wikedjuggalo · #6 12-10-2007, 06:58 PM

Quote:

Originally Posted by svxistentialist

I'm totally with Steevo on this.

I keep mine on 35-31 or 36-32. Factory specs are too soft. It allows the car to wallow on the side-walls. Plus it makes the steering heavy for parking. Plus it wears the outsides of the tire tread.

Run 3 to 5 lbs harder than spec. No penalty, better mpg. No-brainer.

Joe

o.k so I might have gone 5 over, 38 in front, 33-34 in back gauge kinda sucked. Is that too high? I just inflated them and I can feel the difference in handling

porschekiller · #7 12-10-2007, 07:32 PM

Door Badge!

Tim · #8 12-10-2007, 07:39 PM

I usually do 38f/34r on both my summer set of tires and winter set. The stock 33/29 felt underinflated to me.

Nevin · #9 12-10-2007, 08:14 PM

I run 40 in the front and 38 in the rear. I work at a tire shop and we normally just put in whatever the tire says. You'll get the best mileage that way, and your tires will last longer if you keep the pressure higher. The less a tire flexes the more life you'll get out of it, and since most often a tire is rated to run at 44 psi, it's best to just use that. I normally just run a couple pounds lower to improve ride quality.

The tires I currently have on the car are Michelin Pilot Exalto 225/50R16. 40f/38r psi. seems to work very well. I thought the car rode smoothe before with my potenzas, but it feels like I'm riding on a cloud now!

subarufamily · #10 12-10-2007, 10:37 PM

36 in front hot ,33 in back hot, found rides smoother better mpg open road 31 mpg. all my cars are set higher than what door badge says

svxistentialist · #11 12-11-2007, 02:44 AM

Quote:

Originally Posted by Wikedjuggalo

o.k so I might have gone 5 over, 38 in front, 33-34 in back gauge kinda sucked. Is that too high? I just inflated them and I can feel the difference in handling

It might be a little high, but you can see a few people run higher pressures than the door badge.

Running 44 is too high for me, too far off standard.

The possible downside is the centres of your tires may wear faster than the sides, and also you might not get good braking in extreme circumstances, so safety could be compromised.

Somewhere around 36-32 should be a good compromise.

Tim · #12 12-11-2007, 06:54 AM

Quote:

Originally Posted by svxistentialist

It might be a little high, but you can see a few people run higher pressures than the door badge.

Running 44 is too high for me, too far off standard.

The possible downside is the centres of your tires may wear faster than the sides, and also you might not get good braking in extreme circumstances, so safety could be compromised.

Somewhere around 36-32 should be a good compromise.

The other issue is that the ride may become bouncier.

svxistentialist · #13 12-11-2007, 07:05 AM

Quote:

Originally Posted by TE1221

The other issue is that the ride may become bouncier.

That's true as well Tim

Another issue with hard pressures is the suspension is getting more of a pounding if they are really hard. At closer to correct pressures there is bump absorbtion in the deflection of the tire. With very hard tires practically all the shock is transmitted to the dampers and the joints, with corresponding higher wear.

Joe

ssnsltd · #14 12-11-2007, 04:04 PM

thanks Guys!

immortal_suby · #15 12-12-2007, 06:08 PM

I have to jump in here (as a tire building/unformity technician)
The worst thing you can do for your tires and your safety is run too little air pressure.
Most air pressure ratings on the door jam are low. Car manufacturers often under inflate to soften the ride. The SVX inflation recommendation on the door jam is low.

You will get better on road handling and increase the life of your tires by putting more air in them. Every rotation of the tire causes flexing of the belts as they enter and exit the contact patch. Flexing of the belts causes heat. Heat kills tires. More air will give you a stiffer tire that may ride a little harsher but it should last longer, handle better, and actually increase your mpg. The worst part of a tire for heat is the edges of the tread (where the summit belt edges are) This is the part that take's the most beating from underinflation. This is the area where belt separation will begin from too much heat (see firestone/explorer)

I usually am within 5-10 psi of the max cold inflation on all of my cars with the rear around 3-5psi lower than the front. I've never worn out the center tread before the sidewall doing this.

Pump 'em up hard, drive it, and then lower the rears a few psi at a time until the handling feels right.