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tyre question

Posted: Fri Jun 26, 2009 11:16 pm
by BrixhamBongo
dont know much about wheels and tyres , :? but can you put std tyres on rx8 alloys ?
just thinking about saving money on tyres

Re: tyre question

Posted: Sat Jun 27, 2009 12:14 am
by scanner
BrixhamBongo wrote:dont know much about wheels and tyres , :? but can you put std tyres on rx8 alloys ?
just thinking about saving money on tyres
If you mean std size tyres off steel wheels, no.

Re: tyre question

Posted: Sat Jun 27, 2009 9:47 am
by BrixhamBongo
well i kind of meant not low profiles

Re: tyre question

Posted: Sat Jun 27, 2009 10:53 am
by scanner
BrixhamBongo wrote:well i kind of meant not low profiles
Well the answer is still no because if you don't fit low profile tyres to bigger rims (such as the RX8s) you will increase the diameter of the whole wheel (rim & tyre) and that will raise your gearing.

That might not be much of a problem where I live - here a railway bridge is a "hill" and a 1:100 slope is "steep" - but imagine trying to drive around your area with 2nd gear being the lowest one you've got.

For instance if your rim diameter goes up from 15" to 16", the tyre profile (for a 215 tyre) has to come down from 65 to 60 if you go up to 17" rims it has to come down to 55 and 18" down to 50.

The trouble is that a 215/50 - 18 tyre is unlikely to have a high enough load index, so you have to go for a wider tyre and to maintain the right diameter you then have to go for a lower profile.

Re: tyre question

Posted: Sat Jun 27, 2009 8:30 pm
by the janner vanner
It looks like you are running on RX8's at the mo, what size tyres are you running on now and what is you load rating? You should be on 225/45/18 with 92 loading on the front and 96 on the rear. I can get this size new for £75 a corner here in Plymouth. I did manage to get one for £60 when I had a punchture at the Poole day meet last year.

Re: tyre question

Posted: Sat Jun 27, 2009 8:45 pm
by mikeonb4c
BrixhamBongo wrote:well i kind of meant not low profiles
I know where you're coming from.. I didn't want low profile tyres on my 17" wheels and fitted 225/55/17s. They work great. The gearing business doesn't seem to have been an issue and I think that the autobox will simply shift down to match engine revs to load. It also has S and L settings as well as D which ought to cover all the pitches. Deeper profile tyres stop the ride from getting too harsh which is why I wanted them. the RX8s are 18" aren't they? Maybe see what is out there that will go on an 18" wheel. One thing I do know: if the overall diameter on the front gets too big the wheels will foul the front bumper stays (look inside wheel arch at front to see these) when turning. The Russian bongo peeps sorted this by cutting off the stays, with no ill effect they said (and they seem to know their stuff with Bongos) 8)