Wheel and Tyre calculator

Technical Guidance for doing those Tricky Jobs

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aka_juffa
Racing Driver
Posts: 1005
Joined: Wed Dec 14, 2011 2:40 pm
Vehicle: NA8
Location: SE Melbourne.

Wheel and Tyre calculator

Postby aka_juffa » Tue Apr 17, 2012 10:25 am

Very handy calculator. It allows you to see the affect of changing wheel/tyre size on your actual speed v speedo reading, and provides information on how much closer/further the outside edge of the tyre will be from the inside of the wheel guard/fender when compared to your current wheel/tyre combination....very handy when upsizing your wheels/tyres

http://www.rimsntires.com/specs.jsp

J.
Motor Neurone Disease chose me, I choose Voluntary Assisted Dying.

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hks_kansei
Speed Racer
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Joined: Tue Feb 03, 2009 10:43 am
Vehicle: NB8A
Location: Victoria

Re: Wheel and Tyre calculator

Postby hks_kansei » Tue Apr 17, 2012 10:56 am

Tyre section width = T
Tyre aspect/profile = A
Wheel Diameter = D
Wheel Width = W
Wheel Offset = O

Rolling diameter = (D*25.4)+((T*(A/100))*2)

Wheel inner barrel = ((W*25.4)/2)+O
Wheel Outer Barrel = ((W*25.4)/2)-O
If new wheel Inner barrel > OEM wheel, new wheel closer to guard liner/suspension
If new wheel Outer barrel > OEM wheel, new wheel closer to outer guard.


Track change = oldO - newO



Formulas for those who may want to just plug it into excel to compare bulk wheels/tyres/etc.
note: I haven't had a chance to double check my formulas yet, but they should be fine.
1999 Mazda MX5 - 1989 Honda CT110 (for sale) - 1994 Mazda 626 wagon (GF's)

Jace
Racing Driver
Posts: 661
Joined: Fri Oct 24, 2008 7:47 pm
Vehicle: NA6
Location: Geelong

Re: Wheel and Tyre calculator

Postby Jace » Sat Apr 21, 2012 4:47 pm

mr mathamagician up here ^

i like this one because it gives a rough idea of tire stretch/bulge and i think it's a bit clearer as well

http://www.willtheyfit.com/


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