Have an RB5 and it's almost time for tyres to be replaced - currently have Toyo 215/40/17 tyres but have noticed the following -

a) Speedo is MASSIVELY over-optimistic, I reckon it's in the region of 10%+ out

b)Comparing the diameter of them to my dad's Scoob which has 205/50/16, the Toyo's are about an inch smaller.

So, rang up my local decent tyre outfit and have been told that I should really be fitting 215/45/17.

I'm aware that this is the std fitting to the Fugly and that classic owners have put fugly wheels on their cars but does this size of tyre cause any problems when fitted to a classic?

Any thoughts much appreciated,

Phil



[Edited by drumsterphil - 1/23/2003 7:56:02 PM]

I've been told otherwise mate! I was incorrectly quoted for 215/45/17 - and discovered that the tires wouldn't clear the arches when I did tight turns (rubbing). 215/40/17 is the correct fitment for classic imprezas.

BTW, how do you know your speedo is out?
:)

I doubt the speedo's wrong, you're just going faster than it feels, the correct size for 17's on a classic is 215/40 17.

If the diameter of the wheel and tyre is smaller then obviously the speedo will read too high!!

Phil,
if you're really concerned, take your car, put a chalk mark on a tyre sidewall, then role the car a complete revolution of the tyre, then do the same with your dads, it ain't much different I can tell you, esp if you take into account tread depths!

Cheers for the comments guys!:)

I don't want to be a muppet but anything that puts undue strain on transmission (i.e. fitting too big tyre) is of concern but seen as my RB5 goes in for full decat fitment etc tomorrow, perhaps that's a mute point!:rolleyes:

Given the amount of wheel arch space that I have at the moment I had not considered wheel-arch rubbing to be likely although car will also be having Eibachs fitted as well.

Correct size for the RB5 17" is 205/45/17 but until a tyre manufacturer other than Pirelli makes a tyre of this size then 215/40/17 it is by the looks of things.

The speedo is definitely highly optimistic (experience from driving for 13+ years now and the relative speed of other vehicle's indicates this). I have a friend who's a PC so might ask him to procure a speed gun just to find out how much out it is.........

Phil

Have a look here it allows you to compare wheel/tyre sizes and then calculates the difference including speedo readings

Hope it helps.

http://www.miata.net/garage/tirecalc.html

215/40x17 is just over 1% smaller than OEM 205/50x16, IIRC. I think 215/45x17 is approx 2.5% bigger?

The 40% profile obviously compounds speedo over-reading slightly. I have 17in Goodyear F1 tyres as above and, according to my Road Angel (claimed dead accurate) an indicated 30mph is an actual 27.
100mph is an actual 94 and 130 indicated is an actual 122. Car is UK00.

Fitting 215/45x17 will get the speedo quite a bit closer to actual, but I prefer the safety margin. You should not have any wheel rubbing problem with this size (it's the width that's the problem, not the height) assuming your wheel off-set is 50mm or more. Some tyres rub with 48mm off-set, while others don't - the marked tyre size is nominal rather than actual. Prodrive recommended off-set is 52mm.

But as I say, I like a little safety margin and the 45% profile will lose you some steering sharpness, which is the main reason for going low-profile in the fist place ;) Could be a mite more comfortable, though.

Richard.

[Edited by Hoppy - 1/24/2003 1:10:38 AM]

Cheers Hoppy:)

Phil

Oops:D

Double post! D'oh ;)

[Edited by drumsterphil - 1/24/2003 7:58:14 AM]

drumsterphil,

I've had 215/45 R17 tyres on my MY98 for almost two years and 15k miles with no problems. The suspension is standard and I've had no rubbing. The car is also has a slightly more comfortable ride too than with 40's. As for the speedo accuracy, I'm not sure.

I'm soon going to be replacing them with four more.

Hope that helps,

Gavin

on the sti v8/v7 they fitted 225/45/17's as standard!