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      08-28-2013, 08:12 AM   #45
JimD
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Has anyone had a really bad experience while running Michelin PSS with a tire pressure of about 40 psi? It seems like the problem may not be the tire, it may be the pressure.

I tested various pressures on my OEM run flats in an autocross. I used the white material sold to mark your windows with the price when you are trying to sell your car on the triangles marking the tread to sidewall transition on the tire. I raised pressure until I was running on the treads and not the sidewall. I had to go up around 40 psi on the run flats to keep them off the shoulder. I haven't run the PSS at the autocross yet but hope to this fall. I would not go lower on pressure based upon the softer sidewalls. I may go up.

If you run 32 psi I can see why you had a problem. But why do that? A more scientific test is to measure tread temperatures but I don't have the equipment for that. A bottle of marking fluid is only a couple bucks. Why not figure out the right pressure before driving 10/10ths?
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      08-28-2013, 11:18 AM   #46
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Quote:
Originally Posted by JimD View Post
Has anyone had a really bad experience while running Michelin PSS with a tire pressure of about 40 psi? It seems like the problem may not be the tire, it may be the pressure.

I tested various pressures on my OEM run flats in an autocross. I used the white material sold to mark your windows with the price when you are trying to sell your car on the triangles marking the tread to sidewall transition on the tire. I raised pressure until I was running on the treads and not the sidewall. I had to go up around 40 psi on the run flats to keep them off the shoulder. I haven't run the PSS at the autocross yet but hope to this fall. I would not go lower on pressure based upon the softer sidewalls. I may go up.

If you run 32 psi I can see why you had a problem. But why do that? A more scientific test is to measure tread temperatures but I don't have the equipment for that. A bottle of marking fluid is only a couple bucks. Why not figure out the right pressure before driving 10/10ths?
Pressure has very little to do with it IMO. Optimal pressure on track should be 35-38psi HOT on track and slightly lower for autocross for most street tires. I believe most people that destroys the PSS have insufficient camber (stock alignment). Running very high pressures is nothing but a crappy bandaid for this. However, the OP had -3 degrees of camber, which still may not be enough but its not too far off.

Like I stated before, the PSS's casing and especially compound are for street use. The compound is designed to give peak performance at lower (street) temperatures and you will be way above the optimum temperature range after the first or second flying lap on track with a semi descent driver in a 135i. I believe the tires are getting really overheated and are just delaminating or chunking.
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      08-28-2013, 01:26 PM   #47
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Pressures could be a start. But it is still a nature of the tire.

I'm running -2* on my front, and -1.8*-ish on the rear with RS3s and run 30 front, 27 rear hot on autocross and 34 front, 32 rear cold on the track to reach my 38 PSI front and rear.

With a proper tire to handle these loads, with a designed sidewall, I've been able to push the tire hard without any fall back on my RS3s.

The nature lies with the compound. Low or high pressures, it isn't designed to deal with the stress people are doing to them
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      08-28-2013, 01:30 PM   #48
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Everybody is entitled to have an opinion but when it is uninformed..... I checked with other competitors and got the same recommendation for 40 psi from the more experienced ones. I did tests to determine my choice, anybody else have a supported opinion.

If you look on the sticker inside your door you are likely to find a higher pressure for heavy loads and/or high speeds. Racing loads tires thus it calls for more pressure. Racing sometimes involves high speeds which calls for high pressure. Running your normal back and forth to work pressure for racing doesn't make sense - if you expect your tires to work properly. Tires with stiffer sidewalls may tolerate this better but why do it? For normal driving you don't want high pressure because it wears out the center of the tread. I see no drawback for racing. You don't put enough miles on to worry about tread wear in a normal sense.
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      08-28-2013, 02:07 PM   #49
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I think what the above folks are saying is you want to achieve a proper hot psi. This is why you start lower when cold. the psi will rise as the tires get hot. Moisture in the air will expand and cause the pressure to go up.

Starting out at 40 psi may yield too high a pressure when hot. I have seen gains in psi by as much as 8-10 depending on the tire, temp and humidity.

Another factor would be how hard you are driving the tires along with alignment, track surface, temp and suspension set up. To name a few.

I have not driven on street tires for a long time while on track so take with a grain of salt. I'm not saying what you propose will not work. So it's best if you just try it out and see what the out come is.
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      08-28-2013, 07:16 PM   #50
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Quote:
Originally Posted by JimD View Post
Everybody is entitled to have an opinion but when it is uninformed..... I checked with other competitors and got the same recommendation for 40 psi from the more experienced ones. I did tests to determine my choice, anybody else have a supported opinion.

If you look on the sticker inside your door you are likely to find a higher pressure for heavy loads and/or high speeds. Racing loads tires thus it calls for more pressure. Racing sometimes involves high speeds which calls for high pressure. Running your normal back and forth to work pressure for racing doesn't make sense - if you expect your tires to work properly. Tires with stiffer sidewalls may tolerate this better but why do it? For normal driving you don't want high pressure because it wears out the center of the tread. I see no drawback for racing. You don't put enough miles on to worry about tread wear in a normal sense.
I can see where you're coming from but it is not the correct way to think about tire pressures on your car for track use. Tire pressures are are supposed to be fine tuning, after the rest of the alignment has been sorted out, to maximize contact patch. Look at anyone running level 1,2, or 3 r-compounds and you will find most hot pressures around 27-35 psi HOT for most sized tires on most platforms. You almost never find anyone (experienced) using 35 or higher. Street tires require a little more pressure but 40 psi hot is about the maximum. Ive run my R-S3s at 40 psi hot (I know different tire, but they have really soft sidewalls similar to PSS) and liked the feel best compared to lower pressures, but the stopwatch was telling me 36-38 was faster.

Each tire near 135i sizes should have a load rating of around 1,300 pounds, which is conservative for what the tire is actually capable for short periods of time. Since a 135i weighs around 3,400 pounds you aren't even close to having to worry about increasing pressure for load related reasons. Running too high of a pressure on track will cause you to overheat the tire faster and could have a few other negative effects depending on the specific tire, size, vehicle weight, alignment, ect.

Lighter cars running EPS or R-comps may sometimes use higher pressures (high 30s to mid 40s hot) to get and keep heat in the tires.

I daily drive my tires at 45psi cold simply for maximum fuel mileage and have never had issues with the center wearing out faster. Modern radials, especially performance tires with low aspect ratios don't "ballon" like older tires or much larger truck tires when pressures get high.

Last edited by MMisencik157; 08-29-2013 at 01:45 PM.
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      08-28-2013, 08:29 PM   #51
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Quote:
Originally Posted by JimD View Post
Everybody is entitled to have an opinion but when it is uninformed..... I checked with other competitors and got the same recommendation for 40 psi from the more experienced ones. I did tests to determine my choice, anybody else have a supported opinion.

If you look on the sticker inside your door you are likely to find a higher pressure for heavy loads and/or high speeds. Racing loads tires thus it calls for more pressure. Racing sometimes involves high speeds which calls for high pressure. Running your normal back and forth to work pressure for racing doesn't make sense - if you expect your tires to work properly. Tires with stiffer sidewalls may tolerate this better but why do it? For normal driving you don't want high pressure because it wears out the center of the tread. I see no drawback for racing. You don't put enough miles on to worry about tread wear in a normal sense.
Sticker on your door goes right out the window when it comes to high performance driving.

The pressures need to vary based on rollover.

When you run proper pressures, your tire will look like this:



and this



and this



Yay for tire deformation!

And this is what the tire looks like when unloaded



Anyways, the tire NEEDS to do this in order to get full grip. If you run high pressures, you get no rollover, which means you don't get grip.

Those pressures are 30 front, and 27 rear.

So who is to say the pressures are high or low?


Running correct pressures while driving the tire at the limit is EXTREMELY important. The explanation on not putting enough miles on tires for wear is completely incorrect. I flipped my tires for Mid-Ohio and had fresh unworn shoulders. By the end of the second day they were worn down to the point where they looked like before I flipped.

Last edited by Kgolf31; 08-28-2013 at 08:35 PM.
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      08-29-2013, 08:01 AM   #52
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I don't think we are in complete disagrement but I also think your pressures are low for track use for many tire/cars/drivers. Here is an article recommending 38-45psi:

http://www.motoiq.com/MagazineArticl...-Pressure.aspx

I also think we all agree it varies by car, driver, and tire (and I agree the tires in the pictures above seem to be properly inflated). But increased pressure will deal with the exact issue that OP had. It decreases understeer, decreases driving on the shoulder of the tire and decreases temperature minimizing the potential for chunking. If you google something like "tire pressure for racing" you will find several articles, all recommending increased pressure for racing. The Tire Rack article recommends up to 50 psi for Hoosers. There was also a good article about using tire temperature as the way to judge correct tire pressure. I got the idea of using white compound on the thread to shoulder juncture out of the Roundel. It isn't the best method but is better than just blindly guessing or assuming normal inflation levels are correct.

The only real point I am trying to make is that the evidence of tire damage is consistent with running too low a pressure on the track. With higher pressures, I think the results would be different but I haven't tried it yet to know for sure. That is why I asked if anybody had damage at higher pressure. Even better would be for somebody to test different tire pressure to see what it takes to keep the tread (and not the shoulder) on the track when racing. I will probably run 40 or maybe 42 cold with these tires my next autocross. I won't get more than one or two tries to adjust pressure so it won't be a great test but I am confident I will have better results than if I ran 32psi. I'm running a square setup with stock suspension and may or may not run the fronts 2-4psi above the rears. If I was still staggered, I think I would definitely increase the fronts a little. That seems to be the recommendation from those with more experience than I have.
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      08-29-2013, 12:41 PM   #53
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Quote:
Originally Posted by JimD View Post
I don't think we are in complete disagrement but I also think your pressures are low for track use for many tire/cars/drivers. Here is an article recommending 38-45psi
*** HOT ***
And yes, we totally disagree

Quote:
will probably run 40 or maybe 42 cold with these tires my next autocross.
I don't have time to argue all the points you've made in this thread so far, so I'll just point out two things:
  1. As the "OP", I'll have to point out that the tire damage is not fro running too little pressure. If anything, these tires got too hot from too much pressure at times since it's hard to control their temp on track, especially compared to RS-3s or Star Specs.
  2. As an autocross instructor with our local BMW CCA chapter, I hope that non of my students show up with 40-42 PSI of pressure in their 3500lbs+ cars... Unless it's drift day! Which it never is
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      08-29-2013, 09:02 PM   #54
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Quote:
Originally Posted by JimD View Post
I don't think we are in complete disagrement but I also think your pressures are low for track use for many tire/cars/drivers. Here is an article recommending 38-45psi:

http://www.motoiq.com/MagazineArticl...-Pressure.aspx

I also think we all agree it varies by car, driver, and tire (and I agree the tires in the pictures above seem to be properly inflated). But increased pressure will deal with the exact issue that OP had. It decreases understeer, decreases driving on the shoulder of the tire and decreases temperature minimizing the potential for chunking. If you google something like "tire pressure for racing" you will find several articles, all recommending increased pressure for racing. The Tire Rack article recommends up to 50 psi for Hoosers. There was also a good article about using tire temperature as the way to judge correct tire pressure. I got the idea of using white compound on the thread to shoulder juncture out of the Roundel. It isn't the best method but is better than just blindly guessing or assuming normal inflation levels are correct.

The only real point I am trying to make is that the evidence of tire damage is consistent with running too low a pressure on the track. With higher pressures, I think the results would be different but I haven't tried it yet to know for sure. That is why I asked if anybody had damage at higher pressure. Even better would be for somebody to test different tire pressure to see what it takes to keep the tread (and not the shoulder) on the track when racing. I will probably run 40 or maybe 42 cold with these tires my next autocross. I won't get more than one or two tries to adjust pressure so it won't be a great test but I am confident I will have better results than if I ran 32psi. I'm running a square setup with stock suspension and may or may not run the fronts 2-4psi above the rears. If I was still staggered, I think I would definitely increase the fronts a little. That seems to be the recommendation from those with more experience than I have.
I don't think you understand my point I'm trying to make, is that you're running too much pressure regardless of what tire.

Increasing pressure for racing is to save their butts for when someone doesn't properly monitor their tires, and ends up destroying them.

No Hoosier tire will ever run 50 PSI, period.

There is NO way you can conclude that low pressure is to blame. You can argue that he ran too much pressure, and the tire wasn't gripping, was skipping across the ground (which it will with too much pressure) causing the chunking to happen.


Running such high pressure is limiting the tire to do what it wants, which is load up. When you prevent it from doing so, it will not like it, and you'll chew the tires in an unfavorable way.


Here are my tires running at "low" pressures, if you want to call that. I can update this with another picture as my tires are now past the wear bars if you really want, but you can see that with a proper tire...you will not see chunking of any kind. 30 PSI HOT fronts in autocross, and 38 HOT on the track.

My tires are monitored with chalk for rollover. I'm past the arrows, but the tires like the low pressures and grip, so I run them as such.



In addition, I'll leave you with this, the new BFG Rivals. They LOVE low pressures, you wanna know why?



Let me introduce you to Sam Strano. Multi-Champion SCCA National driver. This is on his FRS, in the rain. These pressures are actually increased due to the rain.

Are you going to tell a National Multi-Champion he is wrong with his pressures because the door sticker and Tirerack said 40 PSI? I thought not...
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      08-30-2013, 07:56 AM   #55
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^^ you see, this is what I'm taking about when it comes to your posts.. Your tone is just so condescending. Like you're a know it all. And here is some advice: No one likes a know it all.
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      08-30-2013, 08:09 AM   #56
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Quote:
Originally Posted by jordantii
^^ you see, this is what I'm taking about when it comes to your posts.. Your tone is just so condescending. Like you're a know it all. And here is some advice: No one likes a know it all.
who are you to speak?

I'm trying to save people's tires because of blatant misinformation. I don't see you doing anything to help besides follow me around.

Thanks
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      08-30-2013, 08:50 AM   #57
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Kgolf31 is giving you guys the proper information as to how it all is supposed to be done. Appreciate good information for what it is. Thank somebody for sharing knowledge and helping you. It's the internet here, tone is text is very difficult convey. How you read something doesn't necessarily mean that's how it was intended. Give the OP the benefit of the doubt.

FWIW i set my tires this past weekend at 30psi cold b/c to start the day when it 60 degrees out. When they were hot they were up to 39 by the time I got off the track and I had to drop a 1.5 psi out of each tire. I run a square Yoko AD08 setup.
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      08-30-2013, 08:54 AM   #58
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Oy, enough of the 8th grade girl babble. Great info in this thread - thanks to everyone who is adding experience/info/perspectives!
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      08-30-2013, 10:54 AM   #59
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Quote:
Originally Posted by Kgolf31 View Post
who are you to speak?

I'm trying to save people's tires because of blatant misinformation. I don't see you doing anything to help besides follow me around.

Thanks
You just keep doing it. I gave my input and even validated what you were saying in prior posts. But then you use the multi champion deal and make a snide comment to the OP. valid info can be given without jabbing someone because they may not have all the info. It's called manners and politeness.

And as far as the other thread, I believe I made my point that brake ducts do exist on a 135i and when I posted that fact you could have said "wow, I did not know that, good to know". Instead you just left the argument because you were wrong and that is hard for you.

So, if the OP wants to give it a try, let him do it. At least he will come back with some data points that might be useful. Maybe not, but...

Follow you around? Weird.
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      08-30-2013, 02:07 PM   #60
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Quote:
Originally Posted by jordantii View Post
You just keep doing it. I gave my input and even validated what you were saying in prior posts. But then you use the multi champion deal and make a snide comment to the OP. valid info can be given without jabbing someone because they may not have all the info. It's called manners and politeness.

And as far as the other thread, I believe I made my point that brake ducts do exist on a 135i and when I posted that fact you could have said "wow, I did not know that, good to know". Instead you just left the argument because you were wrong and that is hard for you.

So, if the OP wants to give it a try, let him do it. At least he will come back with some data points that might be useful. Maybe not, but...

Follow you around? Weird.
Get your facts straight.

I quoted JimD, who keeps on trying to tell OP to over inflate the tire.

I'm pretty sure OP wants to get his pressures right the first time around, and no end up chunking another tire. Correct me if I'm wrong, but all of the info I've suggested will help prevent this.


As for the brake ducts, it was a worthless conversation because you fail to realize what is a brake duct, and what is not.

The E82's ducts dump air into the wheel well, it doesn't go directly onto the tire like my E86 does, but it doesn't direct air towards the brake. You don't realize that there is still a heat shield blocking all of the airflow to the brake. And still, the caliper is on the other side of the ducting, so there is no DIRECT contact with air to the caliper. Sure, one could argue that you can get some radiant heat transfer from the heat shield to the caliper, but the heat from the rotor would overcome this, IMO.

Google Brake Duct and look at the images, you'll see that all brake ducts via the internet dump air DIRECTLY onto the calipers.


Anyways, call me whatever you please. It's difficult to get the point across when people don't realize the big picture I'm trying to explain. This isn't my first rodeo, and I believe I've answered all the questions in this thread with my best accurate answer.

It always seems like you want to give me trouble, so be it. But you're the one that seems to instigate everything so please continue on ruining threads. I'm not going to change.
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      08-30-2013, 03:16 PM   #61
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Quote:
Originally Posted by Kgolf31 View Post
Get your facts straight.

I'm not going to change.
I know...

http://www.realoem.com/bmw/showparts...=51&fg=75&hl=5

Last edited by jordantii; 08-30-2013 at 03:35 PM.
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      08-30-2013, 04:12 PM   #62
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kgolf31,

I posted one reference, I can post several more if you like. If it was just my opinion or one drivers opinion, regardless of how skilled, that the OP's symptoms are consistent with under inflation for the usage, I wouldn't be posting again. But it is several well respected organizations (including tire rack who tests things, doesn't just state opinions).

I am happy that you like the effects of running lower pressures and driving somewhat on the shoulders. Your tires seem to tolerate that well so I am not suggesting you change. But I am suggesting that people running low pressures on Michelin PSS tires and having bad experience try higher pressure. Again, it is not just me and my friends, it is also several well respected national organizations.

You also seem to dislike Michelin PSS tires and want to use negative experience at low pressures to validate that opinion. That's OK with me too. But I like my Michelins and intend to use them on the track and I further expect good results. But I will not be running low pressures. We all have the right to select the tires we want to run and if you make tolerance for under inflation one of your criteria you can. I just want a good tire and will use the pressure the tire wants to do it's best. I think the evidence is that Michelin's PSS tires want more pressure than you or the OP want to give them.

Jim
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      08-30-2013, 05:22 PM   #63
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Quote:
Originally Posted by jordantii View Post
Ahh, for some reason with your "race car" and brake ducting...you would realize what is a brake duct and what is simply a hole in the bumper

Here is a brake duct kit developed for the 1M. Looks exactly like the realoem image, doesnt it?



Quote:
Originally Posted by JimD View Post
kgolf31,

I posted one reference, I can post several more if you like. If it was just my opinion or one drivers opinion, regardless of how skilled, that the OP's symptoms are consistent with under inflation for the usage, I wouldn't be posting again. But it is several well respected organizations (including tire rack who tests things, doesn't just state opinions).

I am happy that you like the effects of running lower pressures and driving somewhat on the shoulders. Your tires seem to tolerate that well so I am not suggesting you change. But I am suggesting that people running low pressures on Michelin PSS tires and having bad experience try higher pressure. Again, it is not just me and my friends, it is also several well respected national organizations.

You also seem to dislike Michelin PSS tires and want to use negative experience at low pressures to validate that opinion. That's OK with me too. But I like my Michelins and intend to use them on the track and I further expect good results. But I will not be running low pressures. We all have the right to select the tires we want to run and if you make tolerance for under inflation one of your criteria you can. I just want a good tire and will use the pressure the tire wants to do it's best. I think the evidence is that Michelin's PSS tires want more pressure than you or the OP want to give them.

Jim

Since the tread tear away isn't consistent throughout the shoulder, I find it hard to believe that under inflation is to blame.

Here is a case where the cold pressure was 37.5, and the tire failed:

http://www.1addicts.com/forums/showt...light=PSS+tire

There is another thread which shows the tire failing yet again, from heat cycling out. As you heat cycle a tire, the compound will harden and grip will drop off a cliff. Of course depending on what tire some will heat cycle more/less than others

http://www.1addicts.com/forums/showt...light=PSS+tire



I'll fall back to my statement that these tires are just not the correct compound who wants to push their tire.

I've ran a E46 before with all-seasons when I started autocrossing and destroyed my tires. No matter what pressure, or how I/or anyone else drove the car I ended up with pieces of rubber on the side of my car. The compound is simply not made for it.

PSS great DD tire? No doubt, I'm not arguing that at all. For a HPDE or autocross event? There is plenty of other tires at similar, or cheaper price range that can complete the job without any headaches.
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      08-30-2013, 06:13 PM   #64
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I've had a bad experience with Michelin PSS's chunking at AX as well; some of you may have seen the thread. Underinflation definitely wasn't the issue, as I generally ran 38-40 (hot) because I was attempting to compensate for the soft sidewall. I recently purchased a set of Dunlop ZII's, which should be a much more appropriate tire, based on my experience with the old Star Specs.

My question now is what tire pressures should I be running on the new Dunlops? I've found a few references to a Grassroots Motorsports article claiming that 38 PSI was the "sweet spot" for ZII's at AX, but hearing about people running in the low 30's, and even 20's, has me questioning this. Unfortunately, I haven't been able to find the actual article - I went as far as ordering a back issue of the magazine, but it ended up being the wrong one.
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      08-30-2013, 08:47 PM   #65
jordantii
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Yup had them on my e30 M3 and another race car. And yes, that is a brake duct set up that cools the brakes directly with an inlet and hoses. And the pics I posted and what BMW states in their parts catalog are also in fact brake ducts. Just not the same as you pictured. Open wheel cars don't have hoses, but they have brake ducts. I know, I know, you are gonna say thet throttle air directly on the brakes. I get that. But what is in a 135 are brake ducts. And do have an effect in cooling. Regardless of what you say.
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      08-30-2013, 11:21 PM   #66
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I've always favored as low tire pressure as the car allows.

With the 1er. I've run it on 255/40 17s for 3 years. This was with -2.5* camber up front with stock suspension with the exception of camber plates. Went through 4 sets of Star Specs. My best results were always:

Auto-x F- 35 hot (30 cold)
R- 32-33 hot (29-30 cold)
Track 37-38 hot all around (used to start as low as 30 all around)

A lot of the tire pressure has to do with the suspension set up and the weight of the car. Also wheel width adds to it a lot. Running 255 on 8.5" wheel is a bit too much of a tire for the wheel. In order to run 255 efficiently it should be mounted to a 9" or a 9.5" wheel.

My current car rolls around on 295 square and is under 3K pounds with me in it, and I get best result when working with 30psi or under. Most of the time I start around 25 psi cold or less. I know a lot of miata guys will start with 20psi cold pressure and will steal the FTD.

Higher pressure is more for beginners as they tend to overdrive the front end a lot. Running higher pressures will simply help preserve their sidewall, for all the punishment they put their tires through.

Michelin PSS is an awesome all around summer performance tire. Sure it is able to handle abuse here and there from occasional event, but in the end there is a reason why no competitive or frequent attendee of auto-x or track day is running that tire.
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