shotchkiss

Given a choice of tires and rims for a C4, which would provide better grip:

315/35/17 Victoracers on 11" wheels
or
275/40/17 V710s on 9.5" wheels

Solo2GS

You will notice a considerable difference on turn in with the 315's copared to the 275's. I have run both and like 315's on all four corners.

However it really depends on the class you plan on running. SCCA AS you are stuck with the rim size your car came with. BSP you aren't!

tigerdrvr

I don't think anyone who hasn't run the two combos back to back can definitively answer your question. The V710 is a superior tire, but I don't know what the give up is in terms of total grip in running the smaller contact area. Also, the V710 is available in a 295/40-17 size, which fits fine on a 9.5" rim and might end up being a solution.

Umrswimr

Contact patch != traction, BTW.

Per the friction equation F=uN, a wider tire has the same friction force as a narrower one because the friciton equation is completely independent of contact patch. All that matter sis the coefficient of friction (a unitless number) and the Normal force (in our case, the mass supported by the tire).

tigerdrvr

That's what I was trying to get at...two very different compounds, one treaded, one not=totally different coefficients of friction i.e. too many variables to draw a conclusion based solely on contact patch...I think?

talon95

I'd guess they would be similar in performance. 710's are faster, but the Victo's are wider with a wider wheel. I'd be tempted to go with the Victo's as they'll last longer and not cycle out as fast.

Dave G.

Solofast

the 710's

Look at what the hot shoes in AS are doing on the 710's. With the car properly set up and dialed in they would be in a different time zone...

tigerdrvr

No doubt that, in comparable sizes , the V710 has more grip than the VR's...but, the question is whether 275 section V710's on 9.5" rims have more grip than 315 section Victoracers on 11.5" rims. I don't know how you can figure that one out, without back to back testing.
What I don't understand is why, if you're considering running 11" rims with 315's, you wouldn't just buy 315 section V710's

Solofast

Just basing it on experience with both,,, Don't get me wrong, the VR's are a good tire, but... The relative grip with the 710 is way beyond the VR, and, sometimes if you have enough tire, more doesn't help all that much,,, (I could go back thru about 4 generations of tires in three different brands where I have back to back test data, but it shows that if you have "enough" tire, more just doesn't make a big a difference.) So while the bigger VR's will probably be better than smaller one's I don't think they are gonna be as fast as a 710...

Look at folks running 710 295's on the front, versus the 275's... Based on what everybody is saying in this thread the 295 should be "hands down" the right choice, but it doesn't seem to really be any faster. There's a lot of "it depends" going on here, and I'm sure that somebody will eventually test it, but if it were my money going out on the line I'd go with the 710's.... It's an opinion, that's all

astock165

The only thing I'd like to add is I ran the 275/40/17 V710s on 9.5" wheels on all 4 corners last year (about 60 runs over 12 events, 2 drivers) and the turn in was much better than previous years (that may also be a function of moving from AS to BSP) but I did battle a snap oversteer problem (I spun a lot) all year long. BTW, my car has the FE1 suspension

Solo2GS

VR700 & V710's are like comparing apples to grape fruits even with the size difference I am going to say the V710 will out grip the V700. I used to run the V700 back in the day and can noticably tell the difference in grip between the two.

I asked this very same size question about 275 vs 295 fronts to Scotty McHugh (AS national Champion for several years now) and Tom McDaniel (AS Corvette that Scott & he co-drive together) the outstanding consensus was NO on the 295's.
The car is an 89 Z51 Corvette with 275's on all corners so 315's in AS are not an option for them.

I ran AS all last year (3rd place) and ran 275 in the front and 315 in the rear. I can say by going with the 315's in the front (BSP) the grip and turn in is much better than with 275's...

shotchkiss

Budget reasons. I plan to autocross the current car for 2 more years, and with the budget I have set aside, I could either buy 2 sets of 275 710s, one set for each year, or a set of 11" rims and a set of 315 VRs to run for 2 years, which is close to the lifespan my last VRs gave me.

Solo2GS

FYI, I go through 2 sets a season with a ratio of about 2 front tires per every rear tire replacement...

Our season is 12 events, not including National Tours or ProSolo's out here.