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Old 07-11-2006, 08:11 AM   #1
daytona
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Got a question regarding tires..

my car normally runs on 205/55/16 would there be any issues I have to worry about going to 205/45/16?..
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Old 07-11-2006, 08:38 AM   #2
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Not really you are just going to have a smaller sidewall. Instead of having a 55% side wall(of 205mm) you'll have 45% of 205mm. Also check inside your door for the recommended tire sizes on stock rims.
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Old 07-11-2006, 09:19 AM   #3
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Your spedometer will be off by about 7%, which is somewhat significant. The ride will be harsher. You will also have a greater chance of bent rims. It will probably also look quite funny, since the wheels will probably look too small. In short, you should probably stick with the proper size for your car.
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Old 07-11-2006, 09:44 AM   #4
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It will also have an adverse effect on your ABS and DSC (or ASC+T...whatever you've got) because the overall diameter will have changed significantly from what they've been programmed to recognize.

I would suggest 225/50R16
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Old 07-11-2006, 01:45 PM   #5
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OTOH you will get better acceleration and higher highway cruising rpm
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Old 07-11-2006, 01:57 PM   #6
NOTORIOUS VR
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Quote:
Originally Posted by Godspeed
It will also have an adverse effect on your ABS and DSC (or ASC+T...whatever you've got) because the overall diameter will have changed significantly from what they've been programmed to recognize.

I would suggest 225/50R16
it won't effect anything... as long as all 4 tires are the same size, the ABS and DSC units will never know the difference.
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Old 07-11-2006, 02:08 PM   #7
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It really won't matter, but you've got a 6.5% difference.

When your speedo reads 60mph (96.5KMH), you are going 56.1mph (90KMH)

I wouldn't do anything more than a 3% difference.
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Old 07-11-2006, 02:16 PM   #8
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Oh, the odometer would be reading wrong as well.

If you drove about 64,200KM on your car with the smaller tires, you actually only drove 60,000KM on it, but the OD would be off.
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Old 07-11-2006, 08:39 PM   #9
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Besides speedo and odo issues, it will look terrible.

Don't do it.
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Old 07-13-2006, 04:13 PM   #10
BennyL
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hrm... never though of all these issues.

so can i ask a question... i've got 15 inch rims right now. 205/60/15. if i go to an 18 inch rim, which tire size will be correct for my speedometer and odometer not to screw up?
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Old 07-13-2006, 04:20 PM   #11
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according to what Nascar318is said, my sidewall is 60% of 205 mm, which is 123 mm. i calculated that a 15 inch rim = 381 mm. which makes the overall diameter 504 mm.

i was going to go with a 225/40/18 tire on the new rims, but according to my calculations, 40% of 225 is 90, and 18 inches = 457 mm. which makes the overall diameter 547 mm.

thats 43 mm's bigger! is that bad?
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Old 07-13-2006, 10:53 PM   #12
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You give me headaches.

http://www.miata.net/garage/tirecalc.html

Anything within 3% is fine.
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