Swimming Against The Tide - I Want Smaller Wheels!

[br1anstorm]

I have recently bought a 2002 IS300 SportCross. It is completely standard, and in good shape although the original 5-spoke wheels are showing some of the usual corrosion and paint bubbling.

I'm looking at alternative wheels, but not for the reasons you might think. The standard SportCross rims are 17" x 7.0 JJ (with 215/45 ZR17 tyres) at the front, and 17" x 7.5 JJ (with 225/45 ZR17s) at the rear. I think the offset is 50 for both front and rear rims, but I haven't yet checked.

But here's the thing. All the posts I have read so far are about getting larger wheels and lower-profile tyres. I want to go the other way. Not for looks or style but for other reasons.

I reckon - on the basis of a short period of driving - that the 45-profile tyres give a slightly harsh ride, and make the wheels vulnerable not only to kerbing but also to pothole damage (and where I live the winters cause lots of potholes!). So I'm prepared to lose a tiny bit of grip in extreme high-speed corners in order to gain a slightly better normal ride. I want to fit smaller 16" wheels with slightly higher profile - 55 or 50 - tyres. But I don't want to affect the height or the suspension geometry in any other way.

I believe some earlier IS200 saloons had 16" wheels as standard anyway.

I'd appreciate advice from the LOC tyre and wheel gurus about suitable alternative wheel/tyre sizes. I can understand the importance of making sure the rolling radius stays more or less the same so that the speedo etc are not affected - which is why I think 16" with 50-profile is the closest to the current 17" with 45-profile. But I'm struggling over rim width and offset. It doesn't help that on the SportCross the rear rims and tyres (7.5 and 225) are wider than the fronts (7.0 and 215). This is presumably on the assumption that the SportCross is more likely to be carrying heavier loads - but is the rear suspension set up differently as well?

So the questions are:

i) what width rims should I be looking for if I get 16" wheels? Still 7.0 and 7.5?

ii) should I stick with 215 and 225 width tyres, or come down to 205 and 215? Or....

iii) could I go for a set of four 16" wheels and tyres of the same width (say 215) all round, rather than having fatter ones at the rear?

iv) how much leeway do I have in terms of offset, assuming that all the existing wheels are 50?

Any expert comments would be welcome!

[ACLex]

I have recently bought a 2002 IS300 SportCross. It is completely standard, and in good shape although the original 5-spoke wheels are showing some of the usual corrosion and paint bubbling.

I'm looking at alternative wheels, but not for the reasons you might think. The standard SportCross rims are 17" x 7.0 JJ (with 215/45 ZR17 tyres) at the front, and 17" x 7.5 JJ (with 225/45 ZR17s) at the rear. I think the offset is 50 for both front and rear rims, but I haven't yet checked.

But here's the thing. All the posts I have read so far are about getting larger wheels and lower-profile tyres. I want to go the other way. Not for looks or style but for other reasons.

I reckon - on the basis of a short period of driving - that the 45-profile tyres give a slightly harsh ride, and make the wheels vulnerable not only to kerbing but also to pothole damage (and where I live the winters cause lots of potholes!). So I'm prepared to lose a tiny bit of grip in extreme high-speed corners in order to gain a slightly better normal ride. I want to fit smaller 16" wheels with slightly higher profile - 55 or 50 - tyres. But I don't want to affect the height or the suspension geometry in any other way.

I believe some earlier IS200 saloons had 16" wheels as standard anyway.

I'd appreciate advice from the LOC tyre and wheel gurus about suitable alternative wheel/tyre sizes. I can understand the importance of making sure the rolling radius stays more or less the same so that the speedo etc are not affected - which is why I think 16" with 50-profile is the closest to the current 17" with 45-profile. But I'm struggling over rim width and offset. It doesn't help that on the SportCross the rear rims and tyres (7.5 and 225) are wider than the fronts (7.0 and 215). This is presumably on the assumption that the SportCross is more likely to be carrying heavier loads - but is the rear suspension set up differently as well?

So the questions are:

i) what width rims should I be looking for if I get 16" wheels? Still 7.0 and 7.5?

ii) should I stick with 215 and 225 width tyres, or come down to 205 and 215? Or....

iii) could I go for a set of four 16" wheels and tyres of the same width (say 215) all round, rather than having fatter ones at the rear?

iv) how much leeway do I have in terms of offset, assuming that all the existing wheels are 50?

Any expert comments would be welcome!

The 16" wheeled cars were fitted with 6.5x16 alloys with a 50mm offset and 205/55R16 tyres and they were also fitted to the Sportcross in this size.

Andy

[Parthiban]

As above the IS200 Sportcross came with 16" alloys, so you may be lucky and find another owner on here who might be interested in a swap + a bit a cash or something?