I've got 17x7 racing harts and 205/40/17 Kumho Ecsta All Season Tires. When I got them they had something like 25-30 psi and they looked flat, and they looked flat untill I put about 42-46 psi in them but from what I've done with cars that seems reallllly high!!!! please let me know what ya'll are running

 

Whats the max tire pressure for your tires? I would pump up your tires to half of what the max tire pressure is. I think 32 PSI is good for you.

 

Oh wow, ok. The max is like 60 or 50psi. When I was below 40 they looked flat almost!

 

I had the same problem. The max PSI is 60, but nothing is said on the tire as far as normal pressure. The tire manufacturer said to go by the vehicle specs, but I am running different sizes than stock...I have been keeping them between 32-35 PSI. I have no clue where else to run them...LOL

 

well you could always stop into a tire service place that you are comfy wit hand ask them. That would be my guess. Maybe they could help.

 

Thanks all, I am going to try the tire shop when I get a chance, I just wanted a quick solution.

 

I was told by Tire Rack if I was running 205/40/17's to keep the pressure 40 psi or higher because that size tire doesn't have a high enough load rating. If you had 215/40/17's you should be safe with 35 psi and up. Hope this helps clear up your problem.

 

Thats good to know. I am running a 205/45-17 ( I think...LOL) I did notice that at 35, it rides a lot rougher compared to 30-32 PSI.

 

Wow great info thanks!

 

I usually put in 10% less than the max that's printed on the tire. Just my rule of thumb. I'm sure someone will satte otherwise, but like I said, its just MY rule of thumb.

 

i was told by two tire/rims shops that because of the low profile tires, it should be at 40-42 lbs.

I have kept mine at 40 lbs since having my rims/tires...

 

Will the center wear out quicker by running it that high?

Squirrel, my max is 60...and 10% less would be 54? I ran mine at 40 for 3 days and was worried...LOL. The ride was horrible too!

If it works, then I'll do it!

Nobody, including the tire manufacturer, could tell me where to run the pressure. They all said to run the factory PSI stated in the manual or in the doorjam. But I am not running the OEM size tires...

 

So with my tires at 42 front and 46 back my ride is so flippin hard it rattles my teeth out, but it definitely has better gas mileage then when it was at 32 and 36

 

my dad who is a certified ase master mechanic for over 30 years told me to pressure should be ok at 40-45 for my 215 45 17 tires. but if you want better traction lower the pressure. i lower it during snowy weather.

 

I run 10% less because it has always worked for me. The S-03s on the Matrix lasted over 28k miles, pretty good in my book, considering a buddy didn't have his last past 15k miles.

Another thing thing about ride comfort, the shorter the side wall, the rougher the ride. Why? Less sidewall for cushioning.

I know from experience the ride w/ 215/40-17s were alot better than 205/40-17s. Everytime I hit a pothole w/ 205/40s, I thought the car was going to break. It was much better when I went to the 215/40s. Plus 215s were closer to the OEM rolling diameter.

Sometimes you have to play w/ different pressures to find what works best for you and the conditions you drive in.

Over-pressured tires will have a contact patch of only the center of the tire, too low pressure has only the edgesin contact w/ the pavement.

When I first started auto-x'ing(in 1982), I would buy a can of the spray on window tint, spray it on my tire, and the roll the car over a piece of paper to see which tire pressure gave me the best contact patch.

 

That's some MacGyver chit right there! I feel you on the 205s being harsh... but I need the lowness. Doesn't that suck!

Dave, I would keep it around 38-40 psi. Too much more than that & you'll have stage-coach suspension!

 

Good info guys...Thanks to you all and the thread starter!

BTW...squirrel....GREAT way to see the contact patch of the tire, but does it change at higher speeds? Probably not enough to matter though.

I will put mine back at 40 PSI. I know it'll help my mileage.

On our Matrix XRS, we traded it in at 37,000 miles and still had decent tire tread on them. Granted, we DID notice a BIG difference between the winter of 2004 and 2005. We didn't get 'stuck' as much in '04.

 

Excellent I dont feel so lost now, I'll go drop the fronts to 40 and the rears to 38 and see how much better it drivers.