D'oh

I picked up my race wheels and tires today. I can't wait to try them out. Next AutoX is Sept. 21, but I may need to do a couple mountain runs just to make sure everything is working.

I ended up with the following:
Wheels = Enkei RPO2J 18x8x35mm offset
Tires = Kumho V700 265/35-18

I'm running the same size wheel and tire on all four corners.

Here are a couple pics.

-D'oh!

D'oh

Closeup of the rim and tire edge to show the overhang.

-D'oh!

Z350Lover

iTrader: (2)

would it be safe to drive with the tyre wall like that????? wouldn't tyres got separated from the wheels while they are running?

cheers,

richie

FLY BY Z

I would be more concerned about that when tires are stretched to no end over a rim.

Blue Liquid

A 265 width tire on an 8 inch wide wheel is fine, he'll have no issues with the tire coming off the rim! However, I am interested to see how his ABS/TC/VDC is affected by the fact that he is no longer running a tire stagger front to rear (car's computer is expecting a stagger). Let us know if you think you notice anything unusual D'oh!

Apexi350z

iTrader: (3)

Since this is his race tire setup, I don't think he is concern with VDC.. That's the only thing will be affected with wrong tire size.

droideka

You're certainly entitled to that thinking, but you are wrong. I can't believe a vendor actually sold that ****ing size combo.

KUMHO SPECS:
265/35WR18 93W SL Heat Cycled 50 AA A
RIM RANGE = 9-10.5"
OPTIMUM RIM WIDTH = 9.5"

I WOULD NOT trust that size on an open track. Parking lot, maybe, but I don't auto-x.

webcarconnection

I have Kumho Ectra Supra in that size for the rear... what are you think about the tires the Kumhos, they are good?

thanks!

D'oh

Thanks for the questions and comments.

Here are a couple of clarifications:

The purpose of these wheels and tires was to get as much tire as possible on the stock size wheel so I could AutoX in the stock class. I understand that I am running a pretty aggressive tire size compared to the wheel width, but hey, that's how we find the limits. I may use these on the track as well, but I'm not sure yet about that. If, for some reason, these tires don't work well, I can always drop back to a 245 Hoosier. Problem is they are another couple hundred dollars for four tires.

I'll be racing with VDC off, so I'm not worried about problems during the race, but I will be driving to events with the race tires, so I can test out how TCS/VDC responds on the street. That will be interesting.

I know quite a few people using Kumho race tires for AutoX, and they all seem to like the tires. However, I think most people feel that Hoosiers are better. They are also more expensive, so for many, the Kumho's are simply "good enough"




And what the hell is this response:
Why all the hositlity? Do you have any experience or knowledge about this, or are you just regurgitating the MFG specs? You of all people must know that MFG's are very conservative in their specifications (after all, I see that you have the S-Tune on a VDC equipped car ), so just having that MFG info is not enough for me. I realize I'm on the edge as far as tire sizes, but that doesn't mean failure is eminent. Thanks anyway for your OPINION.

-D'oh!

PS - If my tires do fall off, you guys will be some of the first to know. I'll be sure to post about it here.

-D!

failsafe

Hey D'oh- where is the event on the 21st?

zoasis

I think they'll work wonderfully! Let us know.

droideka

This is where you are wrong, IMO. Because of the Firestone fiasco, tire mfg'ers are VERY specific about how their products should be used. As far as hostility goes, I don't see it, but maybe I just don't like to see my fellow owners **** around with something as important as tires. You are a full inch smaller width-wise than the recommended rim size. To me, that's beyond pushing it.

Good luck with it regardless.

D'oh

There are a couple events,

One is the SCCA AutoX @ Golden Gate Fields in Albany

The second is a private group that I run with as a guest.

I think I'll end up running with the private group because I know more people there. Also, I've heard that the parking lot at Golden Gate Fields has a significant amount of gravel and is therefore not a very good place to run on race tires. I've never run there before, so it will be difficult for me to compare performance other than a simple "seat of the pants" feeling. Since I have more experience with the private group, I think I'll be able to get a better idea of the difference in performance between the street tires and the race tires.


I think it was the use of "****ing" as well as the attitude of "You're certainly entitled to that thinking, but you are wrong" that seemed a bit hostile. I definitely am not "****ing" around with tires; after extensive research into what people are actually running, I actually believe strongly that this combo will work fine.
Regardless of that, I appreciate your concern but hope you are wrong, for no other reason that if things don't work out, it will be an expensive lesson for me . But at least we will all know what that tire/wheel combination is capable of. I don't mind being the guinea pig on this. Stay tuned for an update in a little over a week.

-D'oh!

2003z

iTrader: (7)

Carter Thompson is running 275s on his 7.5"/8" 17s and if he cant make a tire come off a rim, noone can.

Blue Liquid

One thing I worry about though, is the ABS system. I really wouldn't care too much about TC or VDC, but I definitely don't want my ABS modulation to suffer because of uneven stagger or a wheel diameter that is too far out of spec. D'oh, that's what I'm really talking about. What are your thoughts on this?

2003z

iTrader: (7)

I run the same size all around to and from autocross and at the autocross, and have no abs/tcs/vdc issues. Of course VDC is off on the track.

MY350Z.COM

iTrader: (2)

D'oh, I think he meant hostility towards your vendor, not to you. He is just concerned for his fellow members.

Victor

Buub

iTrader: (1)

No, the ABS will also be affected. It needs to measure relative wheel speeds to determine if a wheel has locked up.

GaryK

People often run tires on rims that are not at least the minimum spec'ed width. The 265 on 8" rims shouldn't be a problem. I've seen 275's on 8" rims with no problems, track and autox. I do however question the advantage you get by doing this since the wider tread is not supported as well as it would be on the properly sized rims. I have tried some different combos in the past on a car that was limited to 8" wide rims in stock class, and I always felt like the narrower tires (245mm) worked better than the wider tires (265 and 275mm). But that was just my own experience, it could work out differently with all the variables involved like suspension geometry, tire construction, car weight, etc.

D'oh, good luck with the new tires. I don't know if you've run a new set of tires at the autox before, but it would help to scuff them in a bit before the event. If you don't, you'll waste a run or two just getting all the mold release compound out of the rubber.

jackwhale

Do'h: Golden Gate does have more gravel but the view of the Bay is so much better...and I don't even know where the private autocross is being held.

I put 265/35/18 (Bridgestone SO3) on my rear Volk wheels. The rears look similar to the picture you posted...slightly more bulge than the stock 245. No problems at all so far. There were many posts with similar warnings about my 265s being out of spec on a 8.5" wheel, and I did decide that I will buy 255s next time around.

For autocross or track I also had planned on having same tire size front and back. So I'll be interested in your experience. There is a fellow, Kevin (Blue Z) who competes in SCCA autocross. All four tires + rims are the same size (don't know what size however) He's quite experienced and does well--keeping up with the S2000s in BS.

I ran at Thunder Hill in July. I don't have anything negative to say about the ride or handling of the 265 on the rear...big improvement over stock. I did notice that the ABS activated rather easily at the track unless I eased up on the pedal pressure. I assumed that the problem was from my overzealous pedal pressure. (i.e. braking from 115 to 35) rather than ABS being confused by the difference in tire sizes.

I don't think that ABS kicks in unless there is an abrupt change in rotation of one wheel. So long as the tires are sticking to the pavement the ABS should not be working. Your Kuhmo autocross tires are stickier than road tires.

On our stock tires the front wheel goes around 1.026 times for every revolution of the rear wheels (based upon circumference of our stock tires). Your front wheels and rear wheels have the same circumference so there would be no difference between the front and rear wheels. I would guess that it would take more than a difference of 1.026 to have the ABS kick in.

I would be interested in hearing from people with more experience figuring these things out.