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The mkiv Supra Owners Club

Help With Wheel Calculations Please


SupraAyf

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Fellas,

 

Can one of you help me calculate what size wheels I would need for my car. My Supra is 50mm wider either side at the rear than a standard Supra and 33mm wider either side at the front.

 

I have read this:

 

http://www.usacomp.com/terms.htm

 

but it has advice like the following extract which means bugger all to me:(

 

 

OFFSET

 

The offset of a wheel is the measurement of the hub surface contact area in offset from the center line of the overall rim width of the wheel. A wheel whose hub surface contact area sits further towards the outside of the wheel than the center line has a positive offset. A wheel whose hub surface contact area sits further towards the inside of the wheel than the centerline has a negative offset

 

 

 

 

..

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This will hopefully make it clearer........

 

If you fitted wheels with the same spec as stock 17's (8" ans 9.5" and 50 offset) then you would need to order them with a offset on the front of 17 and an offset on the rear of 0, to get the same look.

 

if you fitted say 9" and 10.5" wheels then you'd need.....

 

29.7mm offset fronts (12.7mm re half the extra inch wider front)

12.7mm offset rears (again the same additional half inch width)

 

 

consider the effect of extra wheel width and the change in offset sperately and then add the effects together...........do the current wheels not have offset and width info on them? If you know that and want them in or out a little bit more that should be easy to work out.........

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Thanks Scooter;),

 

I think it makes sense but I'll sit down and read it a few times. My car is not in the same country as me at the moment but I will check it out when I get back mate.

 

I'm going to have to get a pen and paper and draw a diagram or something (simple minds and simple things:D).

 

Thanks for your help - much appreciated indeed!

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Can one of you help me calculate what size wheels I would need for my car. My Supra is 50mm wider either side at the rear than a standard Supra and 33mm wider either side at the front.

 

Are those widths the increase in distance over stock of the inner arch or the outer arch? Also, how low is the car?

 

If you can confirm I'll stick it into the tyre size calculator and see what it provides.

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Are those widths the increase in distance over stock of the inner arch or the outer arch? Also, how low is the car?

 

If you can confirm I'll stick it into the tyre size calculator and see what it provides.

 

Homer, the sizes refer to the outer arches only. The standard arches have been fully cut away and the bodykit has been blended on top - I hope that makes sense.

 

I'm not exactly sure on heights but the Hyermax II suspension system is set at approx 1-inch lower than stock.

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Homer, the sizes refer to the outer arches only. The standard arches have been fully cut away and the bodykit has been blended on top - I hope that makes sense.

 

I'm not exactly sure on heights but the Hyermax II suspension system is set at approx 1-inch lower than stock.

 

Do you happen to know if there is a lip on the inside of the new arch? If there is, is it any deeper than stock?

 

I'd imagine it's less or has almost none, which should help give a bit of leeway

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The pic Jamie posted is very helpful :)

 

19 inch wheels yes?

 

Using the terms from that diagram, if you want to retain the stock inboard width (best to avoid rubbing issues on the inner arch), the closest rear wheel size would be:

305/30 x19 tyre

11x19 -28 wheel

 

Front:

275/35 x19 tyre

9.5x19 -38 wheel (10x19 also should work, but might rub on the inner arch)

 

The offsets with these sizes will help stop screwing up the suspension geo too much.

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Id go with a 12" rear to get some more rubber on the floor, to late to get my head round them numbers Homer but have you worked that out so the wheels sit in the arches the same as stock? if so id go another 15-20mm on them offsets to give a nice aggresive look.

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Id go with a 12" rear to get some more rubber on the floor, to late to get my head round them numbers Homer but have you worked that out so the wheels sit in the arches the same as stock? if so id go another 15-20mm on them offsets to give a nice aggresive look.

 

Yep, the sizes are worked to be as close to stock with the same arch clearance. As you say, they can be increased for a more agressive look, but run a greater risk of rubbing.

 

Best to wait until the car arrives until ordering anything as it'll give a better idea what to go for and how much room there is to play with.

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