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Gold TX Sleeper
backyard mechanic
Joined: 05 Feb 2002
Posts: 509
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 Posted: Mon Apr 15, 2002 6:07 am Post subject: Wheel & Tyre diameter measuring |
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G'day, can someone please explain the maths to working out your tyres rolling diameter ? I dont know how to work it out, is it something like 195/70/13 = 195+70%X13. Or is it totally different. I'm getting a set of 14's off a BMW and want to know what tyre size i need to keep my speedo as close as possible to actual speed. I have the stock 165/70/13's at the moment, and the new rims are suposed to be 14"X6.5".
Cheers,
Jasyn... |
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Gold TX Sleeper
backyard mechanic
Joined: 05 Feb 2002
Posts: 509
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| Posted: Mon Apr 15, 2002 6:19 am Post subject: Re: Wheel & Tyre diameter measuring |
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| Forgot to add that i'd like to run 205's as well, so i'll need the maths to work out the tyre height i need... |
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Racegem
backyard mechanic
Joined: 30 Jan 2002
Posts: 987
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| Posted: Tue Apr 16, 2002 12:34 am Post subject: Re: Wheel & Tyre diameter measuring |
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Not trying to be a smartarse, but I have answered this question on here before. If you can't find it on search, let me know.
Yonnee. |
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Gold TX Sleeper
backyard mechanic
Joined: 05 Feb 2002
Posts: 509
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| Posted: Tue Apr 16, 2002 3:31 am Post subject: Re: Wheel & Tyre diameter measuring |
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I tried the search before i posted the question, i have been using the search function before i post any questions for almost four weeks now. That's why i haven't posted in a while - i keep finding the answers therefore no need to ask. So obviously i couldn't find the formula for this. I did find your posts to another guy asking a similar question, you basically told him what tyre size he needed, and explained to him how far his speedo would be out as well. But i never came across the actual maths to work it out for any wheel/tryre combination.
Search words i used were - wheels, diameter, rims, tyres, etc. But unfortunately i never came across it. So yeah, whats the formulae ?
Jasyn... |
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Racegem
backyard mechanic
Joined: 30 Jan 2002
Posts: 987
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| Posted: Wed Apr 17, 2002 1:16 am Post subject: Re: Sorry J..... |
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Yeah I tried the same search myself AFTER I posted the message. I'd forgotten I'd only given the answer.
So here goes...
Let's take an example; 195/60R14.
First let's get the rim diameter.
14" x 25.4 = 355.6mm
Now the tyre height.
195mm is the tyre width accross the tread.
The tyre wall height is the second number, expressed as a percentage of the width,
so.. 60% of 195mm.
195 / 100 = 1.95 x 60 = 117mm (60% of 195)
Multiplied by 2, (top and bottom of rim) = 234
Add the rim measurement, 234 + 355.6 = 472.6mm overall wheel and tyre diameter.
Yonnee. |
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