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      07-12-2011, 03:15 PM   #1
persian54
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DD Tire pressure for R Compounds?

I don't have the time (nor the physical ability due to my back) to change wheels out before each track day.

If I was tracking once every 2-3 months, sure, but I'm going to have about 4 track days, maybe 5, in the next 2-3 months alone

Thus I can't keep switching wheels

I was informed I should run about 29 PSI cold to achieve 36 PSI hot max for track driving
But no advice for Daily driving.

My guess is 34 cold? It shouldn't get over 36 hot for daily driving (I don't do spirited runs on the street)

I was informed that if I were to go over 36 hot psi, these tires wouldn't perform well.

Obviously these tires will be toast before 'rainy' season comes to SoCal, so I don't need to worry about driving in wet conditions.

Thank you
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      07-12-2011, 03:44 PM   #2
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      07-13-2011, 11:25 AM   #3
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Set your pressures to whatever seems reasonable, go for a normal drive (at least a few miles) & check your tire pressures. You're still going to want something in the mid 30s hot, so you need to find what cold pressure gives results in an appropriate hot pressure.
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      07-13-2011, 07:45 PM   #4
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i would say whatever BMW says, which should be in the 30s
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      07-15-2011, 02:32 AM   #5
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Quote:
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i would say whatever BMW says, which should be in the 30s
BMWs don't come with R comps...
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      07-15-2011, 03:32 AM   #6
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Quote:
Originally Posted by persian54 View Post
BMWs don't come with R comps...
30s like any other street tire
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      07-15-2011, 11:51 AM   #7
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Quote:
Originally Posted by smmmurf View Post
30s like any other street tire
R-comps aren't really street tires though.....


I'm going to be running 34 cold.

I'll check it after a day of driving.

If it went up too much for whatever reason... I'll just start running 33 cold

These tires shouldn't last more than 2k miles or so, so yeah lo
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      07-15-2011, 11:48 PM   #8
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Man, how do you handle the track with a bad back?
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      07-16-2011, 04:13 AM   #9
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Man, how do you handle the track with a bad back?
M3 is a very smooth car

If I had a S2K or something I couldn't do it

This is also why I haven't done KW CS, cause it'll make the M3 too rough IMO
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      07-16-2011, 10:32 AM   #10
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Quote:
Originally Posted by persian54 View Post
M3 is a very smooth car

If I had a S2K or something I couldn't do it

This is also why I haven't done KW CS, cause it'll make the M3 too rough IMO
Agreed on the m3 being very smooth. But the thing that gets me when an injury is acting up (have a few) is the lateral g's.

Anyway, back on topic : )
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      07-16-2011, 11:14 PM   #11
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Daily driving with a real R compound tire is a bad idea. Not sure which you're going with, but not all are proper R compounds. Toyo RA1s are belived to be the "best" for street use, but even then, it's marginal. You'll have trammlining issues, but also you'll likely never get the tire to its proper operating temperature, and in some cases, you might end up with less grip than a proper summer tire because you're not in the tire's proper operating temperature.

Anyway, aside from any safety issues, you're likely going to destroy the tire very quickly by street driving it. R compounds are EXTREMELY sticky, so your car is going to pick up every pebble and other FOD (screws, nails, etc.) out there and wedge itself deep in your tire. When you hit the track, these items are going to get wedged even further into the tire as it heats up and becomes even "gummier."

As for pressure, F=PA (pressure*area). The force, in this instance, we're treating it to be the static weight of the car, is the same as before, as the weight of your car hasn't changed. The contact patch of the tire hasn't changed either, at least not significantly, so the area hasn't change either. Therefore, the pressure should remain the same, that is, whatever is recommended by BMW, as written somewhere on your car (door sill IIRC).

Super sticky tires aren't necessarily the be all, end all, when it comes to tracking. They are certainly required if your competing, or are really looking to run faster lap times. But if you're looking at having fun and improving your driving skills, then they're maybe not such a great idea. Having a tire that communicates well is more crucial to learning to drive properly. R compounds tend to not give you much warning before they go off, so if you're an inexperienced driver, that might catch you by surprise. A good summer tire would give you much more warning before reaching its limit, and thus allows you to better understand what's taking place as you're cornering, and as a result help improve your driving. Also, your R compounds are going to need a couple of laps to get to temperature, so you'll have to keep that in mind when you hit the track.

Lastly, if you do get R compounds, make sure you heat cycle them first prior to using them. This will require running them lightly after first being installed, and them letting them sit for 24-48 hours.
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      07-17-2011, 06:41 PM   #12
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Quote:
Originally Posted by persian54 View Post
R-comps aren't really street tires though.....


I'm going to be running 34 cold.

I'll check it after a day of driving.

If it went up too much for whatever reason... I'll just start running 33 cold

These tires shouldn't last more than 2k miles or so, so yeah lo
34 sounds reasonable

I've driven on a variety of r compound tires and they aren't really a true slick, so you treat RA1/R888/NT01/etc. almost like you would a Neova Ad08 or RE11 on the street. Hoosier is totally different as is Hankook Z214

On the track it's different, they tend to prefer lower hot pressures. RA1 39-40 hot in my experience. Street tires like to be above 40 especially on camber challenged cars.
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Last edited by smmmurf; 07-17-2011 at 07:16 PM.
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      07-17-2011, 06:54 PM   #13
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Quote:
Originally Posted by persian54 View Post
R-comps aren't really street tires though.....


I'm going to be running 34 cold.

I'll check it after a day of driving.

If it went up too much for whatever reason... I'll just start running 33 cold

These tires shouldn't last more than 2k miles or so, so yeah lo
Cold pressure is totally immaterial to performance, and is only mentioned as a general reference. You need to determine your preferred pressure at the anticipated operating temperature. The optimum pressure will probably be the same for street or track, but your starting point (cold temp) will be very different. You may find your pressure increases only 2-3 pounds from cold to operating temp on street, but 7-8 pounds on track, so your cold/starting pressure may be 35 for street use, and 30 for track. The variables involved (tire, ambient temp, driving style, desired handling balance, etc.) can be evaluated only by the driver.
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