No noticeable change in rubbing or clearance, probably a little better with the F-sport shocks firmer damping. Less body roll too!

 

sorry to revive an old thread but would there be problem running a one inch shorter tire at the back with the 255/35/18 setup?


255/35/18 diameter is 25" while stock 255/40/18 is 26" diameter

 

Previously I would have said that would be no problem at all, and on an IS250 it wouldn't be, but ever since switching to an IS350, the traction control is much more sensitive to tire size variations! I am currently running a square setup on mine and it takes very little to get traction control to engage (it's seeing almost 4% slip at all times, so pushing it past that is very easy). The RWD IS250 on the other hand came with a square or a staggered setup, and it appears that the programming was very lax because of that. I had a square setup (245/40R17) for years on my IS250 setup.

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Jeff

 

Time to step up the tire sizes for the tree-fiddy then! Like you I run 17" wheels, my tires now are 245/40 on the front and 265/40 on the back. Seems to be close enough to stock diameters that I don't have an issue with traction control. I plan on stepping up to 255/40 and 275/40 next spring, we'll see how that goes.

 

As I don't have staggered wheels (as of yet), I will likely be doing 245/40 front and 245/45 rear, just to get the diameters corrected. If I get the staggered wheels at some point, I may do 245/265.

Jeff

 

I started out with those same sizes on OEM 17" rims. IIRC you are running RE-11s on your car? I think they come in 245/45 so that should work well.

 

I'm running RE11A's, yeah. The RE71R is also available now, though I have been considering going to something a bit more street and less track such as the RE760 or Pilot Super Sport. It's up in the air, lol. The ZII Star Spec is also available in the sizes I am looking at.

Jeff

 

Back when I had the 245/40 and 245/45 combo I had Pilot Stupid Sports. Great tires for what they are, despite my making fun of them. I would love to put RE71s, Star Specs, or Rivals on my car, but even with 17" rims they are going to be HARSH, even compared to the RE11s. My wife wouldn't appreciate that move.

 

I found the biggest difference going from the Z1 Star Spec to to the RE11A to be a reduction in noise. The harshness wasn't that much different. But memory is a fickle thing anyway, so who knows, lol.

Jeff

 

Thanks for the info. So does it mean that if I run the shorter than stock rear tire, I will see the VDIM system kicks in more frequently? And if I completely disable the system, there should be no difference?

 

Yes, with 0% difference F/R, I am seeing the TRAC/VDIM kick in around slight corners, etc. Once I turn TRAC off, of course things are normal.

Jeff

 

Following up on this, it actually looks like the 245/40 and 245/45 combination is actually a larger difference F/R than stock. Did you have any issues at all with this setup and traction control/VDIM? In theory it would cause the traction control to kick in slower than stock, but I don't want to regret buying them, haha.

Jeff

 

I don't have any quantifiable way to tell if there was a difference or not, but seat of the pants, and number of times I've had the light blink at me... I can't tell a difference.

 

Sounds good, thanks!

Jeff

 

I see
In this case if I don't want it completely off, will it help if I get a isf steering ecu and use the isf sport vdim setting so it would kick in later?