Tyre Size Circumference - How Much Variance Is Too Much?

[GC8E2DD]

If you start with 205/50/R16 having a circ of 75.6 inches, how far can you reasonably go?

215/40/R17 is 74.7 inches

225/40/R17 is 75.7 inches

215/45/R17 is 77.3 inches

225/45/R17 is 78.5 inches

According to the magical calculator, 225/45/R17 will read ~3.7% slow. The OD is only 1 inch difference (which I believe satisfies WOF requirements). I guess it will also negatively affect acceleration to some degree. But, are these figures negligible? Experiences anyone?

[funkytown]

5% in rolling diam i think is the wof requirement, least what the tyre guy told me.

[ODB]

i thought it was 5" aswell.

Do not quote me on that though.

I changed from a stock wrx 16 rim to the v7 sti rims and nothing bad happened and the wof place didnt say shiz

[Todd]

Top 3 will be sweet as, 4th just but the last a no go. Puts your speedo out if diameter is too much out and can also mess with your ABS. Used to use this calculator in my old job works a treat. Just put in your original size and the ones you are looking at and it spits out everything you need to know.

http://www.1010tires.com/tiresizecalculator.asp

[Guest loren]

I think you'll feel the difference going to 225/45/17, but with your low ration gearbox it shouldn't be an issue.

The difference between 205/40/17 and 235/40/17 in my car is noticeable... I think of it like the difference

between driving hard on a really cold day versus a cold day...

[GC8E2DD]

Ok no problem. Don't have ABS, so that is not an issue. Just looking at some wheels to buy that currently have 225/45/R17's on them. I think I would eventually swap them for 215/40/R17 but that wouldn't be for a long time unless I could sell them on.

[ODB]

yeah you would be sweet.

just rotate tyres to maintain equal wear and replace all 4 together with your ideal size.

[Guest loren]

you may like the higher ratios anyway... Jeff and Al both seem to like 225/45/17.

[albaru]

Well they're actually the same tires. I bought them from Jeff. He made an offer I couldn't refuse!

For me, ideally, I'd prefer some slightly smaller rolling radius, so I can drive quicker out of the ridiculously tight corners that appear in autocrosses designed by people who don't like the 4WDs.

[GC8E2DD]

Sounds good. Time to hit up the IRD for some funds.

[Guest loren]

 al said:

Well they're actually the same tires. I bought them from Jeff. He made an offer I couldn't refuse!

For me, ideally, I'd prefer some slightly smaller rolling radius, so I can drive quicker out of the ridiculously tight corners that appear in autocrosses designed by people who don't like the 4WDs.

lol.

for autox a smaller radius couldn't hurt... Jeff said he prefered the bigger tyres for

sprints on his car... he considers the ratios of the R/RA too low... but he didn't have any trouble at slipway with the bigger tyres... and nor did you

[albaru]

They've done well. Have helped me do quite well at the Slipway