rim size and speed

SAM 180 · tinkerer Joined: 06 May 2002 Posts: 482

if you were to have 16s or 17s on ya gemini, would this mean that you would run slower times down the strip, if this is the case ill have to use my 15s. Thanks Sam

Gene FJ20DET · Posted: Mon Dec 08, 2003 8:22 pm Post subject: Re: rim size and speed

nice story

but if u use the right tires for the rims your rolling diameter will be the same, there for no difference in gearing or speed at all

15's with 50 series , 16's with 45 series and 17s with 40 series all have the same rolling diameter give or take 1%

and it u used bigger rims with bigger tires ie 17's with 50 series tires your 1/4 time will most probably be quicker as u will have a hight top speed and top end power (hardly noticable but in theory thats how it ill work)
cos ya axel is sping the same speed and the bigger cercumference means u will cover more disatance with each revolution of ya axels

ie
smaller rolling distsance = quick of the line but less top end
bigger rolling distance = slower ofthe line but more top end.

1/4 cars u want more top end, street u want bottom end.

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forgive typos and spelling cos i cant be fucked proof reading
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gene
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Racegem · backyard mechanic Joined: 30 Jan 2002 Posts: 987

Nice idea Gene, but not all the same series tyres for a given rim diameter are the same. A 205/40R17 is smaller than a 235/40R17. The "40" is the side wall height which is a percentage of the width.

A smaller overall diameter wil give you better launch, but you'll lose top end speed. And vise-versa, the bigger the diameter, top speed will be better but it'll be slower off the line. Two identical cars with different tyre diameters could, in theory, have the same 1/4 mile ET, but one will have a quicker 60 foot time, the other will have greater terminal speed as it plays catch up.

GROOV3 · petrol head Joined: 04 Oct 2001 Posts: 3682

a mate was telling me last night they had a work van top speed was about 70kmh it had 13's
so they put 14's on it and it then got up to about 85

they were cheering

lol at boonga work vans

Poida · Posted: Tue Dec 09, 2003 11:00 am Post subject: Re: rim size and speed

Um, I find it easier to use a calculator to match things up....

http://www.miata.net/garage/tirecalc.html
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Gene FJ20DET · Posted: Tue Dec 09, 2003 7:19 pm Post subject: Re: rim size and speed

yeah i know the side wall is a percentage, was easyer just to explain it that way
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SAM 180 · tinkerer Joined: 06 May 2002 Posts: 482

cheers poida, turns out if i was doing 100km/ph on stockie 165/75/13 i would be doing 98.8km/ph if i had my 205/40/17 therefor it wouldnt change fuckall. cheers. Sam