225/45/17 Kumho Ecsta V700s on ASA FR1 17x7s

[DistantTea]

So it looks like 225/45/17 Kumho Ecsta V700s will fit on a 17x7 wheel.

Is there any reason I shouldn't choose this setup for autocross this season in my MSP?

-Tom

 

[macklum]

At that width of a tire u will have to watch the rears under load when cornering ,they may rub . You might be better with a 215/45/17

 

[rowan]

Unfortunately, 205/40 is the only other 17" size for r-compounds that is even close to fitting.

 

[scapamouche]

The 225/45 is the NARROW choice for Falken Azenis.

I have a set in the mail, I'll let you know how they work out...

 

[DistantTea]

I'm only really worried about rubbing... but aren't there some people who have put 18" wheels on their cars yet?

I just want to know if a 225/45/17 is going to rub or not.

-Tom

 

[scapamouche]

I'll tell you in a week

 

[DistantTea]

Make it a point to keep me updated please. I'd hate to get 225's and have them rub off my wheel well.

Thanks!

 

[cjstringer]

I wouldn't use them for autocross. You will be getting a LARGER diameter tire. This will weigh more, increase your unsprung weight, and hurt your acceleration. Rubbing or not, I'd go with the 205s. I run Kuhmo 205/40/17 V700s on ASA JS1 wheels and I can notice the difference between those and my street tires for acceleration. The lighter weight and smaller diameter are helpful.
Just a word from experience. I'd never autoX'd before last season, and I won a regional championship and took third in a region I couldn't make all the events. (just stating results to show I'm not blowing smoke)
Hope that helps!
I've run 205/45s up til now on the street, but I'll be putting on 215/45s next week. Worse for acceleration, but good for what I need.

 

[DistantTea]

But don't you think that the advantages of having an extra 20mm of width way overshoots any acceration differences between the two tires? I'd rather corner at my hardest than accerate even 2% faster right?

Thats alot of meat you're giving up to go 205.

 

[dmitrik4]

the point is that the last thing you want to do is increase your overall diameter. that kills your acceleration and your braking. being able to corner faster does no good if you can't get up to that max speed.

true, 20mm is a lot of rubber to give up, but in addition to the larger overall diameter, you'll be working with a taller sidewall on 225/45s than with 205/45s, also not something you want.

is there a 225/40 tire? i've spent all my time looking at 16s, so i don't know.

also, kumho is not the only R-compound maker out there. take a look around, you might spend a few $$ more, but you'll probably find the right size.

 

[rowan]

Remember to check the actual contact patch specs as well. Just because a tire is 20 mm wider, doesn't mean it will give 20 mm extra contact patch.

 

[DistantTea]

the point is that the last thing you want to do is increase your overall diameter. that kills your acceleration and your braking. being able to corner faster does no good if you can't get up to that max speed.

true, 20mm is a lot of rubber to give up, but in addition to the larger overall diameter, you'll be working with a taller sidewall on 225/45s than with 205/45s, also not something you want.

I seriously doubt that an extra two tenths of an inch larger diameter than my stock tires is going to cause much, if any at all, loss in acceration. So I'm going from a tire that has a 24.62" diameter to a 24.97" diameter... whoo I bet that will cost somewhere in the .00005% range for acceleration.

The added width in the 225/45 is going to pay off in spades when it comes to cornering. The added tiny diameter difference will make no difference whatsoever and the added weight is less than 1lb of rubber.

Its not like we're talking about wide 15" hoosiers verses wide 18" Kumho's... we're talking decimal places here. Use an online calculator and see the difference... its all negligible at best.

Now the difference between the 205/40s diameter and the 225/45s are slightly greater... almost a full 1.5 inches. But again that is going to make less than a 2% difference in acceration... but the big thing there is thats a 6% drop in gearing speed. So I'm going to have to shift out of first about 4mph sooner than with the 225s. Plus I'm on a narrower tire so I can't corner quite as hard as the 225s.

On an autocross course, where its all corners with tiny straights I'm going for the beefier tire over the lower profile tire.

 

[dmitrik4]

hey, whatever floats your boat...you asked for people's advice, and you got it. geez.

all i was saying is that, given the option, i would choose a smaller overall diameter if possible...diameter is not the only issue, and neither is weight. but do what you want, they're your results.

 

[scapamouche]

Alas, the smaller diameter is not a choice for Azenis I have the 225s, and they do rub (see post in MSP section.) The rub is not bad, and won't damage the tires.

 

[cjstringer]

Just for reference, if you think 2% isn't a bad thing, on a 60 second course, 2% is 1.2 seconds. Tell me that's not big in autocross.
Just my opinion. What do I know. My championship in my first year proves I know nothing about it.

 

[DistantTea]

A 2% difference in acceleration does not equate to 2% of your total autocross time. Hell an H Stock mini cooper has a 0-60 of 8.2 seconds and a D Stock WRX has a 0-60 of 5.4 seconds. Thats a 34% difference in acceleration. So according to your math the WRX is 20 seconds faster on a course. Not a good enough compairison? The point here is the car that wins at an AutoX is the one that can carry the fastest speed through the corners, since the straights are so small a 2% difference in acceration verses a 5mph greater speed around corners is irrelevant.

I'll take stick over quick...

 

[dmitrik4]

Just for reference, if you think 2% isn't a bad thing, on a 60 second course, 2% is 1.2 seconds. Tell me that's not big in autocross.
Just my opinion. What do I know. My championship in my first year proves I know nothing about it.

if you are pretty new at autoX, then the wider tires will likely make a huge difference for you, while they probably wouldn't make such a difference for an experienced ax'er.

just do your thing and let us know how it turns out. like i said before, they're your results, not mine or cj's.

 

[DistantTea]

Its cool either way I'm sure.

(thumb)

 

[blynzoo]

Just for reference, if you think 2% isn't a bad thing, on a 60 second course, 2% is 1.2 seconds. Tell me that's not big in autocross.
Just my opinion. What do I know. My championship in my first year proves I know nothing about it.

Oh hey, man, I forgot to tell you. Good luck on the Indy and CSCC titles this season.

 

[dmitrik4]

Re: Its cool either way I'm sure.

(thumb)

yep. good luck d00d. (rockon)

(blackpro)