Will this size work well/ok and not bump me out of BS? Also, I am running them on the stock 18" rims is this going to be a problem? Should I consider going 17"? What are the pros/cons to 18" vs 17"? Will going to 17" bump me out of the class?

 

It's the wheels size that is the restriction for the class, not the tire size. If your stock wheels are 18", then switching to 17" or 19" would bump you from BS to BSP. If you can fit 285's then yes, you can use those. From what I recall, I think 275's are the largest you can fit up front.

 

285's will not fit on the front with the stock offset. To give you an example I have the Enkei RPF1's 17x9 35ET with 275/40/17's all around, and up front you can literaly only fit a piece of notebook paper between the tire and the control arm (not even a thick piece of paper would fit in there). The guys at VTR have fit 285's up front on a Z, but you have to get the offset just right, which I doubt you will be able to do given the BS offset tolerances. Hope this helped.

Vince

 

But they WILL fit within the PERMITTED Stock class offset (+/- 0.25 inches from OEM offset).

 

+1 on fitting...

But mounting the Kumho's will be a stone cold B$tch... the rumor was that Carter Thompson had a set of 275s mounted for a couple of pro events but getting them mounted took 4 hours...

Hoosiers will be a lot easier to mount and are just as fast as the Kumhos (some people say faster).

 

285*

not a rumor!

 

Hmm... Interesting on the wheel size, I wasn't sure if they would catch it since some of the other year Zs come with 17" I believe, not trying to be sneaky just thought other years come with 17” and 18” were an upgrade option.

Sounds like 285 or even 275 which I can't find would be a PITA to fit. I'd like to be able to rotate them but that means going to less meat in back; any suggestions? What are a good set of Hoosiers to go with.

I forgot to ask about tire wear on the r-compound tires. "about" what is the life expectancy of these, just autox, not sure about road courses (HPD) at this point. They are not cheap is why I ask.

Thanks for all that replied!

 

Okay, curiosity has got the best of me. Why would it take so long to mount Kumho's versus anything else?

 

the kumhos don't have a lip where it sits on the wheel. i don't know if that makes sense or not, but the hoosiers do. all tires i guess technically do, but mounting a hoosier on a 8" is easier bc the visible lip makes the 285 feel smaller.

kumhos v710 - 60-80 competitve runs. 300-450 miles depending on your driving style.
hoosiers a6 - 40-50 competitive runs.
hoosier r6 - ?!?!

 

2003-2005, the Base and Enthusiast (and auto Touring) came with 17" wheels. Performance, manual Touring and Track came with 18" wheels (Track is 18x8F, 18x8.5R). There were no factory "upgrade options" for wheels.

I ran the Hoosier 275/35R18 on my track model last year (S04s, then S05s for San Diego this year). Hoosiers have an "offset bead" which allows them to be easily mounted on smaller width wheels. The Kumhos don't have this "offset bead" so it can be more difficult to squeeze wider tires on narrower rims.

The Kumhos also have a stiffer sidewall and shoulder than the Hoosiers. Kumho sidewalls don't like to flex too much, so they tend to fold in and not want to seat the bead easily (maybe they're a bit smaller in wheel diameter too, all it would take is about 1/64th of an inch to make them difficult).

You want to use the same size all the way around, since some of the understeer built-in to the Z was simply that the front tires were narrower than the rear. Putting the same size tires all the way around helps to alleviate most of the understeer.

As far as wear, on my S04s I got well over 100 runs, the S05s were done in 33 runs (including flipping at 18 runs!). The Kumho 710s that I've been running I purchased used from Rob Hines after a full T2 race weekend, and I've been running on them since late April. They've probably got another 60-70 runs on them after I got them, and they are only down 0.1 g from a brand new set. These "well used" ones were what I had on my car for the Packwood ProSolo. I had the new ones on the car for the Packwood National Tour.

DOT-R tires will wear better in high-lateral-load (Solo, race) conditions than street tires. This is because the tread flex of street tires causes them to heat the tread rubber and literally "melt" the tread blocks off of the carcass ("chunking").

 

I watched the America's Tire store in Chino Hills, CA mount a number of the 285/30-18 V710s on various sized wheels (I have a few race customers that run that size tire). Here are some of the tricks they do:

1. They put the tires in the sun for about an hour before mounting.
2. The tire mounting area of the rims are cleaned and lightly brushed with 00 steel wool.
3. The tires are mounted on the rims with a pretty trick mounting machine.
4. A big ratchet strap is placed around the center of the tire tread and tightened down.
5. The valve stem core is removed.
6. A Nitrogen bottle is hooked up and a big blast from the bottle seats the beads of the tire on the rim.
7. The valve stem core is installed, the ratchet strap removed, and tire inflated.