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Old 09-20-2001, 12:40 PM   #1
WR-REX
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Default Weight of stock WRX wheels, P7's, and how much difference does it make?

How much do the stock 16" wheels weight. What about p7's? And how much difference does this make anyhow?
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Old 09-20-2001, 01:00 PM   #2
mav1c
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I know the P7's are about 21 lbs. Pretty heavy. Don't know the weight on the WRX wheels, but I would guess in the 16-17 lb range. With heavier wheels, you'll get slightly worse accelleration, a little bit "heavier" handling, a little worse braking distance, and a little worse gas mileage. The plus side is the shorter sidewall tires will perform a little better, especially compared to the RE92's. But the additional weight would be worse than than added performance. Generally, try to keep the wheel weight as close to stock as possible.
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Old 09-20-2001, 01:20 PM   #3
duckboy
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Default no no no...

i beg to differ! if you've ever spent any time on a track or autocross course, you'd know that a bit more wheel weight poses no detrimental effects in comparison to the benefits of much shorter & stiffer tire sidewall.

when i put the P7's & 215/45/17 tires on my car i did NOT see any drop in gas mileage or performance. you have to remember that on a torque meager honda, YES, a lightweight wheel and tire combo are a must. but, come on folks, our cars are pumping out 227 ft-lbs of torque stock!!! just about twice the amount of torque that my '99 civic si had. TWICE. the added weight of a P7 did not adversely affect the car. plus, if you look at the construction of a P7, the bulk of the material is concentrated in the spokes and hub section, NOT in the rim of the wheel. this centralizes the mass and reduces the wheel's polar moment of inertia. albeit, yes, the unsprung mass increased but there was no perceptable decrease in suspension performance. plus, the rims are as strong as iron.

tire feedback and handling jumped up dramatically. no question about which system i'd rather take on the track or use for canyon driving.

but if you're going rallycrossing, that's a whole nother issue...

duckboy
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Old 09-20-2001, 05:54 PM   #4
gtguy
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Right, keep in mind that car wheels are much the same as bicycle wheels. A bike wheel like a tri-spoke can be heavier than a traditional wheel and yet be easier to accelerate and stiffer. I don't know if there's a hard and fast rule for wheel weight.

My car actually felt much, much better when I put the P1s on my Legacy GT wagon vs. the lighter stock wheels, so I'm sure that there are some other equations working on that mojo.

Kevin
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Old 09-21-2001, 12:05 PM   #5
Conduit
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The words mentioned above are the end-all be-all here:
polar moment of inertia.

BTW, no matter how much you want to believe that the larger, heavier P7s don't affect you, you are deluding yourself. You are increasing the lever arm, and the majority of the rim surface material is constant from rim to rim. If you notice, the stock rims are very thick in the center, too. They are actually excellent wheels for cast aluminum. Anyway, I've ridden in a car with CP-035s (replacing older 23lb mille wheels) and the difference was _obvious_. Put some on your car back to back with the P7s and then tell me what you think.

And for the track? Run some race tires and you can forget about your sidewall concerns. I challenge you to flex the sidewall of 225/50/16 R-compound tires with your hands.
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