Need assurance

Dougs260z

Club Member
I have purchased 15x8 et0 rotas, should i use 205x55x15 to the front and 225x50x15 to the rear? Car is 260z 2+2 and is lowered.

15' = 381+112.7+112.7 = 606.5 fronts 205x55x15
15' = 381+112.5+112.5 = 606 rear 225x50x15

or

15' = 381+102.5+102.5 = 586 fronts 205x50x15
15' = 381+101.2+101.2 = 583.5 rear 225x45x15

Obviously this will have an implication on gearing and speedo.
 
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jonbills

Membership Secretary
Site Administrator
People love a little stagger. But I'd be more worried about the rim size. something on the inches scale I think would be better. :)
 

Dougs260z

Club Member
The reason for the different tyre widths (staggered) on the same alloy 15x8 is that the rear arch is slightly larger than the front. Also because it is fixed the issue of turning the steering hitting the inner arch is less.
This is not because of aesthetics but rather to find the maximum combination that maintains the overall front and rear diameter of the wheel to be the same and maximizes tyre width that does not snag the arches.

The second number on the tyre size is a percentage of the width, therefore to maintain the overall diameter of the tyre if the tyre increases in width the second number must reduce.

Overall diameter match to original, thanks to Toopy
195x70x14 = 355.6 + 136.5 + 136.5 = 628.6mm = outer diameter
225 x 55 r15 = 381 + 123.7 + 123.7 = 628.4mm = this is the correct size for 15x8 however this may hit front arches on a lowered car and therefore an alternative maybe wise.

PS you need a 9" tyre for an 8" alloy, as alloys are measured to the inner face of rim and tyres are measured to the overall width of tyre.

http://www.tyresizecalculator.com/tyre-wheel-calculators/tyre-size-for-rim-size-width-calculator

This would be ideal as it matches the original outer factory wheel diameter
225 x 55 r15 = 381 + 123.7 + 123.7 = 628.4mm rear = outer diameter
205 x 60 r15 = 381 + 123.7 + 123.7 = 627mm fronts = outer diameter

Or to be safer, but the downside is that speedo and gearing will alter
15' = 381+112.7+112.7 = 606.5 fronts 205x55x15
15' = 381+112.5+112.5 = 606 rear 225x50x15

Or to be even safer, but the downside is that speedo and gearing will alter even more, perhaps too much
15' = 381+102.5+102.5 = 586 fronts 205x50x15
15' = 381+101.2+101.2 = 583.5 rear 225x45x15

https://www.tacomaworld.com/tirecalc?tires=195-70r14-225-50r15

https://www.tacomaworld.com/tirecalc?tires=205-60r15-225-55r15

I have just purchased yokohama A048 225x50r15 for my 15x8 rotas
 
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