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Old 12-29-2002, 02:51 PM   #1
extraducksauce
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Default Wheel WIDTH Play?

My new thing is watching Best Motoring and I noticed that with FR and 4WD layouts they play with the wheel sizes; e.g., narrower rear wheels. Doesn't this decrease the amount of understeer, and allow you to slide the rear with more ease? Have any of you tried this? I'm seriously considering using their technique.
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Last edited by extraducksauce; 12-29-2002 at 02:57 PM.
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Old 12-30-2002, 01:53 AM   #2
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Not recomended. Different weights/sizes on different wheels with FWD can cause damage to the differentials.

If you can afford differentials at will, then be my guest
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Old 12-30-2002, 06:15 PM   #3
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decreasing traction in the rear tires to get oversteer is a last ditch effort.

in theory the car shouldn't be any faster around a course. youve only got less traction.
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Old 12-30-2002, 06:42 PM   #4
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Running wider tires in the front seems to be common for FWD cars in auto-x, I know that ITRs in DS use this approach. For our cars, you would want to make sure that the diameters are very close, but I think that for example 245/40/17 in the front and 225/45/17 in the rear would probably be ok, and a potentially interesting setup.
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Old 12-31-2002, 04:32 AM   #5
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You would likely have better luck running the same size tire on different width rims, i.e. 235x7.5R and 235x8F.



SLR-
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Old 12-31-2002, 10:12 PM   #6
extraducksauce
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Quote:
235x7.5R and 235x8F.
??
i'm confused here. 235, isn't that tire width??? and what's 7.5 and 8, is that wheel width? if don't change tire width in accord to wheel specs your going to be in a world of hurt; furthermore, if the tire widths are equal (e.g., 235) you aren't changing the capacity of the car to oversteer . . . 235 in front and rear will create more understeer, which is inherent with 4wd and FWD cars.

my suggestion for wheel/tire size combo is this:
225 45 17 (front)
205 55 16 (rear)

using the same type of wheel and maintaining equal wheel/tire diameters will allow relatively even rotational forces, e.g., 45 17 vs/ 55 16; using narrower tires (205 vs. 225) in the rear will decrease the coefficient of friction aft of the car, and will thus create, in theory, more oversteer.
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Old 12-31-2002, 11:56 PM   #7
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Quote:
Originally posted by extraducksauce
??
i'm confused here. 235, isn't that tire width??? and what's 7.5 and 8, is that wheel width? if don't change tire width in accord to wheel specs your going to be in a world of hurt; furthermore, if the tire widths are equal (e.g., 235) you aren't changing the capacity of the car to oversteer .
Yes, actually you are changing the footprint of the same tire by wrapping it around a different width wheel and is a somewhat common yet subtle tuning trick. A 205 rear 225 front would be a bit extreme and if you are worried about tire to wheel specs you shouldn't even mess around with different size tires on an AWD vehicle.

My 2 cents.
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Old 01-01-2003, 12:06 AM   #8
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Let me make this a little clearer, I have a tendency too assume everyone is in my head...


Tires:
4X 235/45 17
( Same size tires all the way around )

Wheels:
front- 17x8 ET 48-53
rear- 17x7.5 ET 48-53


Here you are simply perturbing the protuberance ( sry bout' the alliteration ) of the tire patch a bit more on the rear to induce a slightly lower friction coefficient that graduates with speed.
The elegance of this set up, as apposed to different tire widths, is that it can be controlled much better with tire pressure and it is speed eccentric. At slower speeds, where the understeer is less apparent both front and rear rubber will remain close to traction balance, at higher speeds, as the tire wall flexes and the contact patch convexes the rear will loose more surface than the fronts due to its stretch over the wheel width, helping to offset the F/R dissidence. I do, however, feel there are better ways to balance your car than fussing over the tire/wheel size.



SLR-
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Old 01-01-2003, 08:29 AM   #9
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Best Motoring is not always the best display of driver talent or car setup. Were they racing on a track or "drifting"? Most of that drifting stuff is just for show, and doesn't have much to do with traditional racing (trying to get around the track as fast as possible).

JGTC is a much better show for racing setup & technique.

-scott-
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