Please read my post again . . . I was specific about having 275/40s on 17" rims. I was also specific that I have "another" set of 18" track rims. Yes, I have two sets specifically for autocross. And I have a 3rd set which is my '06 rims as daily driver.

To Spike100 -- you are spot on with your assessments, which like many autocrossers in this forum, are basing their feedback from experience. It still amazes me how many poseurs in this forum base their posts on what they've read somewhere. But for some of us, "real-world" experience matters more than "cyber" knowledge.

 

z-u-later,

I appreciate your participation here and value your advice. I notice lately that a few of the guys who track avoid the Tires & Wheels sub-forum for the reason we just saw on this thread. I think that’s regrettable.

Nothing wrong with a spirited discussion… enjoy reading your posts.

--Spike

 

Spike100 great job on composing the posts to try make it easier for others to understand.

 

I appreciate everyones help with this topic. however i have found many more R comp tires that come in 245-40-17 and 255-40-17 than i have with 45 aspect ratios. my new question is that if i chose to go with a set of these 40 aspect tires, what complications would i have? I plan to only use these tires for AutoX events and i plan on only driving these tires a few miles to and from events of dry sunny days. so what would happen or may happen if i chose to go with a 245-40-17/ 255-40-17 rather than a 245-45-17 and 255-45-17 setup?
Thanks, Jim

 

With VDC off(if equipped) The 40 series will actually be better for autoX because the shorter sidewalls will have less flex and the shorter overall diameter will have quicker acceleration effectively giving you a higher final gear ratio, but limiting your speed in each gear to a lower mph.

 

I do have VDC so would this be the only down side or are there more, IE hazards that could result in my or my precious Z's harm????? i doubt it but just want to make sure.

 

There's nothing to worry about with the 40 series tires all around (either 245 or 255 are fine). With same size on all four corners, you will have more balanced and neutral handling. In addition, the lower profile of the 40 series (vs 45 series) will give you a smaller rotational mass, hence, theoretically, you will be much quicker on the course. Most autocrossers will use 35 or 40 series for this reason, even 30 series at 285/30/18s. Now, that's fast!

 

Arnie,

When I initially read the OP’s first post (#1 on this thread), I made the same misread as you describe because of interference of the Smart Ad feature. Initially I also thought the OP was asking about tires for street use.

But, go back now and read Post #1 on this thread. Mysteriously the confusing Smart Ad underline/arrow has gone away.

What the _?

I guess a Moderator must have seen what you described, realized the problem, and fixed it.

So… don’t beat yourself up on this one.

--Spike

 

it doesn't matter if you have vdc because it should be off whenever these tires are one for autox

 

No problem driving to the event , even if its turned on. Your completely within limits.

 

Thanks for the replys, I mentioned i have vdc because i can turn it off. i dont run Auto x with it on. and i think Zulater mentioned that i should try to go with a square setup, should i go with 245 all around or can i fit 255's in the front?

 

I run 275/40/17 on all 4 corners

 

For autocross, a "square setup" is the most ideal. The 255/40s will just be slightly taller but will give you more grip (wider contact patch).

If this is your 1st time autocrossing, I recommend you don't jump into r-compounds immediately. They tend to "hide" the weaknesses on your driving skills and car's capabilities. Purchase street tires that are commonly used for autocross also. There are several threads already on this site that have discussed this same topic in the past. Falken Azenis are good along with a couple of Kumho tires.

But if you're set on getting r-compounds, try a used set first. Get a feel for how they handle first before splurging on an expensive new set. John Berget at JB Racing Tires can help you with a used set (Google it). G/L

 

last year i ran 255/40/17 on all 4 in autocross and had 0 problems.

 

Whoa, that's weird. I wonder if mods have control over that or if it automatically stops highlighting after a certain amount of time.

Edit: Actually, I think it's because it highlighted "Auto" in my post. LOL. And now it's switching between the OP and mine.

 

This is not my first time doing autox, i have autoxed for one season so far and have taken many driving courses at mid ohio race track in ohio, I used street tires last year and i think i learned a lot on how to improve my driving and where my strong and weak points are, this is my first season using R comp tires and so that is why i want to be sure to have all of the information possible before i invest in r-comp tires, as for you suggestion of used tires, I have looked into that previously but i have chosen to purchase a new set. thankyou for your help, you have all answered my question about tire sizing. Thanks, Jim

 

I’m not sure how the Smart Ad thing works… I only see it as an annoyance. The worst part of this is what we saw in this thread. It made the OP’s good question difficult to read correctly.

--Spike

 

ok so i dont want to drag this thread out that much, but i have narrowed my search down to the yokohama Advan A048, and the new Toyo R888's. does anyone know what has better grip? im not interested in other tire suggestions because i have already done a lot of searching for tires already and i have my reasons for choosing these two options, so does anyone have experience with these tires, and could you tell me what you think of them? Jim

 

^^ Jim,

You are not “dragging this out.” You started a great thread, and I hope it goes for awhile since the responses have been very good and informative. When you attract the attention of members like z-u-later, terrasmak, redlude97, and Fluid1… you get some interesting opinions and mostly “outside the box.” These guys "know," and offer advice on personal experience.

Subscribing....

--Spike

 

I'm slightly biased but the 245/40s on my 18" track rims are Toyo RA-1s. RA-1s are one of the best r-compounds in the market BUT they are actually more suited for road courses. However, one of its advantages is they last longer compared to softer autocross-specific tires produced by Hoosiers or Kuhmos. And one of the best traits of Toyo tires (for whatever reason) are they are very light compared to similar sized tires from other brands.

As for the R888s (beautiful thread design), they are fairly new on the market. I've been waiting for someone to review these tires so I look forward to your comments if you go this route.

Oh BTW, I drove with my RA-1s in last weekend's autocross and I ran faster times than a Z06 . . .