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      07-09-2014, 03:49 PM   #1
irablumberg
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Quick thought for improving traction

Has anyone with the 19" wheels tried moving the rear tires to the front and putting 295s in the rear? While getting near the limit for wheel width, I believe these tires are still specified to fit on 9" and 10" wheels respectively. I don't know if the wider tires would rub on any body parts, but that and slightly increased weight would be the only potential disadvantages that I can see.

On the other hand, the added tread width particularly in the rear should help with traction and letting us get more of the new engine's power to the ground.

Assuming I don't discover any problems, this could be my first mod.

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Ira
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      07-10-2014, 07:15 PM   #2
kitw
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a 295/35r19 is likely too tall and a 295/30r19 is a little bit too short. a 275/30r19 / 295/30r19 should be an ideal ratio but the 19x9 / 19x10 are too narrow to be ideal for those sizes. I need to get off my lazy butt and try my Forgeline 19x10 / 19x11 with 275/30r19 / 295/30r19 AD08R on my F80.
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      07-10-2014, 11:18 PM   #3
irablumberg
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I just double checked with Tire Rack for the specifications on the stock 19" tires. They are listed as follows.

255/35-19 = 26" diameter, 9.2" tread width, fits rims 8.5"-10"

275/35-19 = 26.6" diameter, 10.2" tread width, fits rims 9"-11"

Thus, moving the rear tires to the front would entail a 2.5% increase in rolling diameter. Is this too much?

Proposed new tires for the rear are

295/30-19 = 26" diameter, tread width 11.5", fits rims 10"-11"

These new rear tires would have a 2.5% smaller rolling diameter than stock. Again is this too much?

I would hope the car can handle this much variation as tire wear and inflation differences can likely cause this much deviation. However, I guess we won't really know until some brave soul tries it.
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      07-11-2014, 05:35 PM   #4
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As long as the diameter variance is under 3%, you will be okay!

-Frank
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      07-18-2014, 11:42 PM   #5
kitw
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Quote:
Originally Posted by irablumberg View Post
I just double checked with Tire Rack for the specifications on the stock 19" tires. They are listed as follows.

255/35-19 = 26" diameter, 9.2" tread width, fits rims 8.5"-10"

275/35-19 = 26.6" diameter, 10.2" tread width, fits rims 9"-11"

Thus, moving the rear tires to the front would entail a 2.5% increase in rolling diameter. Is this too much?

Proposed new tires for the rear are

295/30-19 = 26" diameter, tread width 11.5", fits rims 10"-11"

These new rear tires would have a 2.5% smaller rolling diameter than stock. Again is this too much?

I would hope the car can handle this much variation as tire wear and inflation differences can likely cause this much deviation. However, I guess we won't really know until some brave soul tries it.
On the e9x platform, I ran a square setup. Was great when the traction control was off and actually worked ok on the street, but traction control was very instrusive. I suspect ABS would be affected too, increasing stopping distances slightly (because the rear is smaller diameter than stock, it is spinning slightly faster, which would make the ABS more aggressive)

For normal street driving, I would not only keep the difference less than 3% overall, but I would strive to keep the ratio of overall front to overall rear as similar to stock as possible. Stock rear is a bit more than 2% larger than the front.
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