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Old 7th December 2005, 13:50   #1
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Tire size and Speedo error calculator

This is useful for anyone looking at upsizing their wheel and tyres. What's different about this calculator is that it also show you you speedo error after the change.

The basic rule in upsizing is that you want to keep you overall diameter the same as the OE tyre.

Link: http://www.miata.net/garage/tirecalc.html
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Old 7th December 2005, 14:00   #2
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http://www.carbibles.com/tyre_bible.html


this also will help
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Old 7th December 2005, 23:16   #3
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these links are of great help for tyre upsizing...
Can anyone please enlighten on pros n cons of having different rim sizes while going for a tyre upsize...??


KP
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Old 8th December 2005, 09:51   #4
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kpzen, read through the link Satya has posted. It will tell you everything you need to know about tyre upsizing. It goes into great detail there, but if you still have some questions, post them.
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Old 8th December 2005, 11:04   #5
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keeping same OD ,smaller rim means higher aspect ratio or higher profile ...so this will give good ride quality but poor handling...
on the other hand bigger rim size means lower profile ...so this means harsh ride quality over bad roads ...but better handling when compared to the higher profile tires...
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Old 8th December 2005, 15:12   #6
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hey rtech

By different rim sizes...I meant having upsized tyres with different rim width size..
For eg. If we upsize the tyre of zen from stock 145/80-12 to 165/65-13...and use 13x 4j rims...wat are the disadvantages of this combination..?

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Old 8th December 2005, 15:18   #7
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As per the rim width calculator (check Satya's link again) you should use:

145/80/12: 4-5.5 J
165/65/13: 4.5-6 J

The upsize seems to be within limits though.

The disadvantge is that you are now running a lowr profile, so your ride will be way more harsh on a small car like the Zen.

Last edited by Rtech : 8th December 2005 at 15:20.
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Old 9th December 2005, 22:09   #8
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hey Rtech

I agree low profile tyres will give you a harsh ride.....
But... I'm facing a different problem with rim width size...
I upgraded my zen tyres to 165/65-13 with stock steel 13x 4j rims....I know the width of rim isn't correct as per rim size calculator...
My handling n braking become pathetic....and driving at high speeds have become scary to say the least...
I just want to know the how a wrong size rim affects the running of a car...??
Will it have any affect on any other parts like suspension and of course tyres..

KP
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Old 8th January 2006, 16:56   #9
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awesome link satya!!...hey guys..please check out the links...its got everythin you want know about tires..upsizin..etc..

Last edited by angelfire : 8th January 2006 at 16:58.
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Old 27th January 2006, 02:24   #10
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Whats the max difference(%) to be kept in mind while choosing an upsize?
Is it 2%??
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Old 27th January 2006, 03:40   #11
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http://www.1010tires.com/TireSizeCalculator.asp

This site also gives you a warning if your OD changes by 3% or over, which is the limit, according to them.
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Old 24th February 2006, 12:55   #12
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Can the difference also be in the negative (-3)%??
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Old 20th March 2006, 14:09   #13
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These links provided are of great for ppl to know about upsizing the tyres

thanks guys....
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Old 26th March 2006, 10:59   #14
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hey Rtech and Speedsatya, thanks for the links dudes.... until i saw these links i wasnt sure of the differences.... helping me a lot now....
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Old 5th April 2006, 22:35   #15
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Quote:
Originally Posted by v1p3r
http://www.1010tires.com/TireSizeCalculator.asp

This site also gives you a warning if your OD changes by 3% or over, which is the limit, according to them.
Ya the link is really helpful
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