Doh!!! Tire problem solved.

MReedBMWM3

MReedBMWM3

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I recently posted a thread about my exerience purchasing new tires. (Kuhmo Ecstas)
When I purchased my car it was equipped with Bridgestone SO3 Poles.

After installing the new tires I noticed a dramatic change in performance. The change was in handling, it was as if my bmw felt like a "floating boat".

Well, this weekend I tried an experiment and the results are awesome. My tires had 35 psi, so I put 47 psi in them and the results are tight and responsive handling. I am stoked!!! [driving2]

Well just had to tell all of you out there.

Cheers, Happy Halloween.
 
Kirby

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You're probably OK safety wise at 47 psi, but I suspect you will get faster treadwear in the center from ballooning the tire. Try it around 42 psi and see how it feels, the tires will wear more evenly.
 
MReedBMWM3

MReedBMWM3

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Kirby said:
You're probably OK safety wise at 47 psi, but I suspect you will get faster treadwear in the center from ballooning the tire. Try it around 42 psi and see how it feels, the tires will wear more evenly.
Click to expand...

If my max tire pressure is 50 would you still suggest letting the 5 lb. of pressure?
 
MrElussive

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MReedBMWM3 said:
If my max tire pressure is 50 would you still suggest letting the 5 lb. of pressure?
Click to expand...
It's still not a bad idea because the application of the tire (in this case, your M3) is still very related to how much air pressure to use. Try it out and see how it works out.
 
Kirby

Kirby

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MReedBMWM3 said:
If my max tire pressure is 50 would you still suggest letting the 5 lb. of pressure?
Click to expand...
Yep, the only thing the max 50 psi rating means is that the tire will not rupture, etc. at or below 50 psi. It has absolutely nothing to do with the proper or recommended operating pressure. That is always up to the car manufacturer to decide. In fact, it was the subject of a Ford vs. Firestone lawsuit, regarding the proper pressures of the tires on the Ford Explorer - remember the tire explosion recall that essentially killed Firestone?

I'm guessing BMW would strongly recommend NOT running that high of pressure due to reduced handling.

In autocross, the "ideal" pressure for a tire is determined by marking the sidewall tread with chalk, and then observing that chalk on the very edges of the sidewall tread are just worn off. This means that you are at the best pressure for creating a stiff sidewall, but still using maximum tread. Too little pressure and the tire rolls too much onto the sidewall, too much pressure and you actually REDUCE the tire to road sweet spot, and the car slides easier and the center of the tire wears faster.

I run my tires for AutoX around 40 - 43 psi depending on surface conditions. Sometimes I will run a little higher in the rear on a tight course to INTENTIONALLY increase rear end rotation, that is, make the rear a little loose to spin around a tight corner. But you don't want to do THAT on the road!!
 
MReedBMWM3

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Gentlemen.

Thank you for the input.

I will let out the 5 lbs. after work and post the results tomorrow.

I have a thirty mile drive home so I will be able to notice a change or not.

Thanks again.

~Matt
 
MReedBMWM3

MReedBMWM3

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Kirby,

Thanks for all the info.

After work I went out to let the air out of my tires, I checked each tire before letting the air out. I was surprised to find every tire was around 41 PSI. Sunday when I filled them up I am sure that I put 47 PSI in each tire. (well whatever)

I am very pleased with the results my mind is telling me that my car is producing. The mind is funny like that.

I can't thank you guys enough for the posts.
 
B

Bushwackbob

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Aren't you guys running way too much air pressure in your tires, if you're talking about the mid to high 40's range? I thought the car was rated at 35 rear, 30 front? I run my fronts at 33...
 
///M SPEED

///M SPEED

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Bushwackbob said:
Aren't you guys running way too much air pressure in your tires, if you're talking about the mid to high 40's range? I thought the car was rated at 35 rear, 30 front? I run my fronts at 33...
Click to expand...
I too run my fronts a 33 and the back at about 43 psi (this is for the 18" wheels). Seems to run pretty good, however I have never really messed around with different tire pressures to see what worked and felt best. I know I should, but it takes to much time and that is something I am always short on.....

P.S. BTW, welcome to the board Robert.....
 
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sly

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50 psi is probably the maximum pressure when your tires are hot. So I assume you are running with 47 psi cold which means you are exceeding the max pressure when your tires are hot. 47 psi is way too high. I wouldn't go much higher than 37 psi when the tires are cold.
 
MrElussive

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Yeah, I've never seen a car that is recommended to run more than 40psi of air pressure. The problem with running high tire pressures is that the tires are just so much more likely to blowout over road irregularities. And you do not want your tires bouncing up and down, losing grip, during hard cornering.
 
C

cristian1la

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I might not know alot about BMW's but tires is a different story.

The max PSI pressure on a tire size wall is usually the max pressure when cold. Tires are built to hold more pressure than the sidewall amount. So 47psi is okay. It all depends on your needs. You carry around more weight, you need more pressure to hold more weight. All tire manufacturers make tires different, so your owners manual will only work for OEM parts. I have a heavy chevy SUV with low profile tires 245/35r20 max psi rating 55 and only work well with 47 psi and up. Anything less than 45psi and the tires do not perform well at all. Its just the way the tire is made and the weight the tires are holding. Think about it like this. Mountain bikes use about 15-35 psi and sporty street bikes with skinny tires use 45-60 psi. Smaller the tire the more help it needs from air and rubber. Buy cheap tires, put max psi and kaput. So always spend the cash on good tires. No manufacturer will ever recommend more than 40 PSI on a stock tire unless you drive a ferrari or lambo. Hope this helps. And I am not putting any one down. Read the tire tech articles in tirerack.com. (Some proof that I am not BSing)
 
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