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rim size and speed

 
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SAM 180
tinkerer


Joined: 06 May 2002
Posts: 482

PostPosted: Mon Dec 08, 2003 7:57 pm    Post subject: rim size and speed Reply with quote

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
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Gene FJ20DET
hod rodder


Joined: 06 Oct 2001
Posts: 9163
Location: brisbane

PostPosted: Mon Dec 08, 2003 8:22 pm    Post subject: Re: rim size and speed Reply with quote

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.

-----
forgive typos and spelling cos i cant be fucked proof reading
----
gene
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Racegem
backyard mechanic


Joined: 30 Jan 2002
Posts: 987

PostPosted: Tue Dec 09, 2003 1:12 am    Post subject: Re: rim size and speed Reply with quote

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.
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GROOV3
petrol head


Joined: 04 Oct 2001
Posts: 3682

PostPosted: Tue Dec 09, 2003 10:20 am    Post subject: Re: rim size and speed Reply with quote

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
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Poida
tinkerer


Joined: 29 Aug 2003
Posts: 303
Location: Vic/NSW border

PostPosted: Tue Dec 09, 2003 11:00 am    Post subject: Re: rim size and speed Reply with quote

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
hod rodder


Joined: 06 Oct 2001
Posts: 9163
Location: brisbane

PostPosted: Tue Dec 09, 2003 7:19 pm    Post subject: Re: rim size and speed Reply with quote

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

PostPosted: Tue Dec 09, 2003 9:20 pm    Post subject: Re: rim size and speed Reply with quote

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
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