95jersey

Here are the specs for the Hoosier R6. I am currently running 285's on a 9.5" rim and 325's on a 12" rim (OEM C6Z06 rims). I am trying to figure out if there is any benefit to running a 295 on the front. The chart states a 9.5" rim is OK for a 295, but notice the specs compared to the 285...rim width, tread width, overall diameter. It seems while the 295 tire is wider, the tread is somewhat narrower?!? Also notice the larger diamter of the 295 tire...does this mean the tire has a higher profile than the 285 (which would not be a good thing?). My simplistic though is bigger is better and fit the largest tire recommended for the rim size and room under the fender.

For the extra $5 per tire, I am trying to figure out if moving from a 285 to a 295 (front of C6Z06) would have any benefit or perhaps a negative impact? I am already going with the larger rear (345 vs 325), as the specs make it a no brainer, but I am confused on how the tire is wider, but the tread is narrower and how is the diamer larger?

Size
Service Description
Load Rating UTQG Max
Load Max.
Inflation
Press. Tread
Depth Tire
Weight Rim
Width
Range Meas.
Rim
Width Sect.
Width Tread
Width Overall
Diam. Revs
Per
Mile


285/30ZR18
SL 40 C A
1168 lbs.
44 psi
4/32"
24 lbs. 10.5-11.5"
11.5"
11.5"
10.9"
24.6"
NA

295/30ZR18
LL 40 C A
1235 lbs.
44 psi
4/32"
24 lbs. 9.5-11"
10"
11.6"
10.8"
25.3"
NA

325/30ZR19
LL 40 C A
1477 lbs.
44 psi
28 lbs. 0-0"
13"
13.6"
11.9"
26.8"


345/30ZR19
LL 40 C A
1653 lbs.
44 psi
4/32"
30 lbs. 12-13"
13"
14.1"
12.8"
26.8"

TedDBere

Since your fronts are 18s you're having the same problem I had with the 295s on the rear of my C5 coupe 9.5 inch rims. Not only are they taller, I think they're a smidge heavier too.

I ended up staying with the 285s on the rear because of gearing, but you'll probably stay with them because the shorter sidewall should be more responsive on turn-in. IMHO. The widths are identical...go figure.

95jersey

That is what I am thinking...that the tire would actually be less responsive and I don't even get the benefit of a wider tread. While the widths are identical, you'll notice the actual tread width of the 295 is smaller...can this be right? Why would they even sell a 295?

gkmccready

Look at the measured rim width. It's hard to see from the way your chart got pasted, but I bet they put the 285 on a nice wide rim, and the 295 on a narrow one for the measurements. But to see 0.7in difference in height with only a 10mm increase in width at the same aspect ratio -- somebody is playing games...

TedDBere

People were always staring at those 285s on my rears!

Here's an old picture I dug up. Yes those are 18s in the rear and 17s with 275s in the front:



Looked funny, but for a coupe it went like crazy. You can see how short the sidewalls are!

ghoffman

I am running the Hoosier R6 345-18 rear and 295-18 front on 18x11 fronts, 18x13 rear CCW Corsairs They are almost perfect OE diameters so the computer is happy. The balance and grip was fantastic at NHIS on August 16, at least with our Penske coil over setup.
Before I had them mounted I made a few measurements. The 345's had the following:
Max section width= 364mm
Max section height= 108mm
Weight= 29 lbs
Durometer=64

The front 295's had:
Max section width= 304mm
Max section height= 93mm
Weight= 24 lbs
Durometer=64

Pic of this setup exing turn 6 (the bowl) at NHIS:

astock165

Wow! You're one hell of an engineer to get a 295-19 tire to run on an 18" wheel.

Sorry Gary, couldn't resist.

ghoffman

Ok, so I am a lousy typist and I don't have my reading glasses on! It fits, you just need really thick N2 to stop the leaks!

95jersey

So, is the consensus that 285's would be better to run than the 295's? Gary, is there any reason why you don't run the 285's if they are slightly wider and lower profile? I need to order a new set from the rack ASAP.

John Shiels

new HARDBAR rim spacer which is titanium


me either

ghoffman

I am not sure who's consensus you are speaking of, but don't forget I have 11 inch front wheels and 13 in the back. The sidewalls of the 295 and 345's are almost exactly perfect with those wheel widths. I think with a 9.5 inch rim the 295 would be too big. My car was as perfect as it could get last time out (after some adjustments in the pressures and compression damping settings).

ghoffman

Yes, it is Ti, the secret is out, but only because I ran out of silicon carbide reinforced beryllium!

95jersey

We'll according to Hoosier, the 285 tread with is wider than the 295. The treadwidth is 10.9 for the 285 and 10.8 for the 295 while the overall tire width (sidewall to sidwall) is 11.5 for the 285 and 11.6 for the 295 (go figure), BUT the 295 (25.3") is 0.7" taller than the 285 (24.6"). So according to this measurments the 285 is as wide or wider AND has MUCH less sidewall (which is a good thing).

I guess I am trying to make sure if my rationale of the numbers is correct, and that for the OEM rim the 285 is a better choice? I notice that the 285 is definately shorter than the stock GY 265 (25.6 compared to 24.6), so am I throwing of my rake by going with an full 1" shorter tire in the front? That might explain why I am scraping the front undertray.

ghoffman

Well, I measured the section width above at 304mm (11.96 inches)and the diameter is very close to the OE runflats on the front and rear, so the computer is happy. It works very well forme is all I can say.

gkmccready

I'll say it again: if you're looking at http://www.tirerack.com/tires/Spec.j...irePageLocQty=
pay close attention to the "measured rim width."

The 285 is stretched on to an 11.5" rim to measure while the 295 is "pinched" on to a 10" rim. Numbers can say a lot of things if you don't read them carefully.

XPC5R

As you are seeing, mounting the 295 on the front wheel is not an issue, just need to decide if you you want the slightly taller front tire (it is a bit wider in the flesh, Hoosier's specs are not exactly on the mark). The 285/18 is a great feeling tire (crisp), but the car will likely be faster on the 295's.

Benefits of the taller tire - longer contact patch to improve braking performance. Also reduces a bit of the front brake bias, which will improve turn in. Less likely to overheat if abused over a couple of corners also. If you pick up enough grip to get some oversteer, you can increase the front bar rate slightly, and that will shift some cornering force off the rears, and allow you even stronger corner exits.

Different application, but we went from 285 A6 fronts to 315's, the car lost some of the nimble feel, but went faster and never cooked the front tires. Just look at the F1 cars and their large fronts.

John Shiels

I am putting 305 18's on today and hope I don't have a fender problem. Fenders are alreay cut up 1/2" but I won't really know till I track it to see under compression. Hoosiers look big.

95jersey

I finally called Hoosier directly, which is what I should have done sooner. They actually agree that the 285 is a wider tire than the 295 and is lower in profile. They said in the case of the 285 vs 295, the 285 was produced on the largest side of the width range that can receive the 285 rating. They also said the 295 was on the smallest side of the width range required to receive the 295 rating. In the end you have a wider tire, but with a smaller width rating.

He completely recommended the 285 and said it was definately wider and lower in profile providing better grip and crisper turn in. So, not to go against any of the comments already stated in this thread, but this was the recommendation directly from Hoosier. So, it seems only in this case the 285 is the better choice. As stated above, I think if you were going to go as far as a 305 or 315, even though the sidewall is higher, the extra width in those tires will definately win over the 285's lower profile...but unfortunately niether of those tires will fit on a 9.5" rim. So they are not options for me.

Axelrod

you'll always find a great disparity in advice in these replies... after a while you know who you should believe.