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antrx technical discussion => general technical discussion => Topic started by: rollaboy on Aug 7, 2005, 09:26PM

Title: how do wheel sizes work?
Post by: rollaboy on Aug 7, 2005, 09:26PM
pretty much what im wondering in my case is:

is a 17" 205/40 tyre the same size as a 16" 205/45 tyre?

how is the profile of a tyre measured?
Title: Re: how do wheel sizes work?
Post by: Jtas on Aug 7, 2005, 09:46PM
The profile is the sidewall height and is calculated as a percentage of the tyre width.

Sidewall height of a 17inch/205mm/40% tyre = 82mm
Sidewall height of a 16inch/205mm/45% tyre = 92.25
Title: Re: how do wheel sizes work?
Post by: rollaboy on Aug 7, 2005, 10:26PM
not sure i understand,

what do u mean by sidewall??

ill give it a google and see what i get.

but since u know what ur talkig about, is a 40 profile on a 17" wheel gona be close in diameter to a 45 on 16" ??? bigger or smaller?
Title: Re: how do wheel sizes work?
Post by: Jtas on Aug 7, 2005, 11:00PM
(http://www.etyres.co.uk/images/tyre.guide.gif)
(http://www.zymol.com/tiresafety_inside_diagram.gif)


http://www.needforspeed.co.uk/htmlpages/TechWheels.htm
(bottom of page)

is a 40 profile on a 17" wheel gona be close in diameter to a 45 on 16" ??? bigger or smaller?
Yes, it's the closest you'll get.  Your speedo will be out by about 1kmph

http://www.miata.net/garage/tirecalc.html
Title: Re: how do wheel sizes work?
Post by: noss on Aug 7, 2005, 11:24PM
there is a post in the faq section about this complete with a tyre size calculator
Title: Re: how do wheel sizes work?
Post by: rollaboy on Aug 8, 2005, 01:19AM
ok then yeah, might as well delete it.

i did sum googleing and worked it out.

thanks for ur help taz, much appreciated.

Title: Re: how do wheel sizes work?
Post by: KMA_TRX on Sep 5, 2005, 11:20PM
should i bother checking with nrma b4 getting new rims
Title: Re: how do wheel sizes work?
Post by: Kranzy on Sep 6, 2005, 12:39AM
Yes it would proabably be best to enquire with them so you dont get caught out by not being covered if you do have an accident.

Also try and keep the posts relivant to the section. Not many people would read your post here going of the heading which has been covered a lot therefore your better off starting a new topic with all your questions in there.
Title: Re: how do wheel sizes work?
Post by: roseremirez on Mar 25, 2014, 12:29AM
i think there is no need of any confusions because
Sidewall height of a 17inch/205mm/40% tyre = 82mm
Sidewall height of a 16inch/205mm/45% tyre = 92.25
if you are still confuse visit to R & R Certified Tire and Auto
Title: Re: how do wheel sizes work?
Post by: deviate on Mar 25, 2014, 01:27PM
This should help you keep your rolling diameter as close to the same as possible
Title: Re: how do wheel sizes work?
Post by: deviate on Mar 25, 2014, 01:27PM
http://www.carbibles.com/tyre_size_calculators.html