PrevPrev Go to previous topic
NextNext Go to next topic
Last Post 20 Jun 2014 07:36 AM by  TedDBere
C5 Z06 Optimal Wheel and Tire Sizes for 2015 rules
 11 Replies
Sort:
You are not authorized to post a reply.
Author Messages
blake.wilson@pmcs.com
New Member
New Member
Posts:2


--
19 May 2014 04:04 PM

    I picked up a 2003 C5 Z06 and am trying to figure out how to set up the tires/wheels for Solo 2.  I went to an event this weekend and saw someone running stock 17x9.5 F and 18x10.5 R wheels with 255/40/17 front and 315/30/18 rears with BFG Rivals.  The fronts are limited in width by sizes that BFG makes for 17 inch wheels.

    Since we can change wheel diameter by +/-1 inch I'm thinking to buy some wheels that are 18x9.5 F and 18x10.5 R which opens up the front tire options.

    If I do that, then BFG Rival 275/35/18 or 295/35/18 look possible.  Tirerack's data shows the 295/35/18 should only be mounted on a 10-11.5 inch wide 18 inch tall rim.  Has anyone tried the 295/35/18 Rival on a 9.5 inch wide front wheel?  Or is 275/35/18 optimal for the front?

    It seems Kumho Ecsta XS are 180 treadwear (not legal in 2015) and not available for purchase anyway.

    Is there a better tire/wheel combo for C5 Z06 in A-stock on street tires?

    blake.wilson@pmcs.com
    New Member
    New Member
    Posts:2


    --
    19 May 2014 11:08 PM
    http://forums.corvetteforum.com/aut...ivals.html
    It took a while searching but found a related thread. Others are thinking abou this.
    talon95
    Veteran Member
    Veteran Member
    Posts:1924


    --
    20 May 2014 06:11 AM
    More links,

    B-street (somewhat related): http://forums.corvetteforum.com/aut...build.html

    Long more general thread: http://forums.corvetteforum.com/c5-...thers.html

    And an interesting data point that I linked to in the first thread:

    http://www.roadraceautox.com/showth...ost1419669
    z06fun
    New Member
    New Member
    Posts:47


    --
    28 May 2014 05:08 PM
    One thing that can be a problem when trying to find street tires for the vettes is tire diameter ratio and how it plays with the cars abs and other systems. You may want to do some reading on the road race forums on the corvetteforum to try to find info on your year as it varies as to what works with out problems for each year. Its not just problems with abs that can arise with a diameter ratio that is way off from stock, there is this "engine drag" error that I've seen some mention, I guess it can't simply be gotten around by simply turning off active handling and such.

    I *believe* the C5Z can tolerate equal diameters front and back, even though its a bit far off the stock staggered diameter. If you could find enough front bar (call Strano as he has several to choose from), you could run the 18" 315 rivals all around if they clear in the wheel well in the front (they clear fine on my C6 grand sport). I can tell you that the 315 is only mildly punched on a 18x9.5 that you could use in front in the A-street class.

    Something also I should mention, the rivals need more temperature (maybe as much as +30 degrees more) to get to there sweet spot vs. a direzza ZII or the new Hankooks. I have a hard time getting the 315's up anywhere near where they need to be on the front of my grandsport at events, but I am also in the northeast and its not quite summer yet.
    edfishjr
    Basic Member
    Basic Member
    Posts:283


    --
    28 May 2014 05:40 PM
    Keep the front tire diameter at least slightly less than the rear and  you will be OK. I've run it bigger and had to turn off traction control, but slightly smaller was no problem. Even with turning off traction control it autocrossed well with no other issues. ( I do not have active handling, so that could be different.) I run 275-18 Rivals on the 8.5" C6 wheel on my BS corvette and it is better than 255-17. I run the 295 in the rear on the 9.5" wheels... no issues, good traction. 

    If it were me, I'd try 295/315 on a C5Z06, especially if I didn't have Active Handling. (I can't remember, did all C5Z06's have AH?) You will have to turn off traction control at all times due to the front being bigger than rear in diameter. People have cracked their fenders squeezing 315's (Hoosiers) on the front, but some do so with some rubbing of the fender liner. They may have had a spacer of some sort, as well.  (You may have to replace the liner every year or two.) You'll have to find a legal 18" 9.5" wide wheel. And, you will have to tune the handling for this setup.
    12secondscooby
    New Member
    New Member
    Posts:4


    --
    28 May 2014 11:16 PM
    All c5zs had active handling/traction control, but it is easy to disable and is useless at autocross anyway. Stock C5 base rear wheel is legal for use on the front with a 4mm spacer (IIRC the rule is within 1/4" so 7 mm?).
    edfishjr
    Basic Member
    Basic Member
    Posts:283


    --
    28 May 2014 11:29 PM
    Posted By 12secondscooby on 28 May 2014 11:16 PM
    All c5zs had active handling/traction control, but it is easy to disable and is useless at autocross anyway. Stock C5 base rear wheel is legal for use on the front with a 4mm spacer (IIRC the rule is within 1/4" so 7 mm?).

    The rule will be 7mm. Next year, I think. 6.35mm right now.

     

    So, a C5 magnesium rear and a spacer would be cool on the front. They are pretty easy to find.


    rickmartinez
    New Member
    New Member
    Posts:43


    --
    29 May 2014 12:07 PM
    Something also I should mention, the rivals need more temperature (maybe as much as +30 degrees more) to get to there sweet spot vs. a direzza ZII or the new Hankooks. I have a hard time getting the 315's up anywhere near where they need to be on the front of my grandsport at events, but I am also in the northeast and its not quite summer yet.


    Interesting. Everything I heard pointed to keeping the Rival's stone cold and we watered them down between drivers at the MW Pro. That said, I didn't really feel much of a difference run to run as they heated up, good or bad.
    edfishjr
    Basic Member
    Basic Member
    Posts:283


    --
    29 May 2014 02:35 PM
    Posted By rickmartinez on 29 May 2014 12:07 PM
    Something also I should mention, the rivals need more temperature (maybe as much as +30 degrees more) to get to there sweet spot vs. a direzza ZII or the new Hankooks. I have a hard time getting the 315's up anywhere near where they need to be on the front of my grandsport at events, but I am also in the northeast and its not quite summer yet.


    Interesting. Everything I heard pointed to keeping the Rival's stone cold and we watered them down between drivers at the MW Pro. That said, I didn't really feel much of a difference run to run as they heated up, good or bad.
    My experience is also that they work good cold and get slightly better warmed up, but no big differences with temperature. Unlike RS3 V1 which were horrible cold. I have been able to overheat them with back to back to back runs at a warm-day/sunny test & tune. We'll see how they do in the full summer, but from what I've seen I plan to water early on a really hot day.

    blake.wilson@pmcs.com
    New Member
    New Member
    Posts:2


    --
    01 Jun 2014 06:44 PM

    I ended up getting Hankook RS3, version 2 tires.  I stuck with stock wheels (17x9.5 F and 18x10.5 R) because i'm cheap .  I shod them with 255/40/17 F and 285/35/18 R.  I got an alignment done and went off to an event in Stockton at San Joaquin Fairgrounds this Saturday and Sunday.  I ran 38psi F and 34psi R on Saturday and 35psi F and 30psi R on Sunday.  I was looking out for rollover and got scrubbing on the tires close to but not quite at the little triangle/arrow on the sidewall of the tire.  I think those are where you don't want to wear beyond.  I think I'll run them at the lower pressures as I think I PAX'd better on the second day with the reduced pressure.  I haven't seen the results posted online yet but my ballpark assesment is the lower pressures resulted in the faster PAX'd results.

    The run group had ~25 cars, course was short (~43sec, 2 cars on course at a time) and the air temp was 85-90F with full sun.  I didn't notice much difference in grip between the runs.  The Hankook's grip didn't seem to vary too much across this temperature range from first to last run.  I guess that means the V2's do get to heat quickly which was their design intent, from what I hear.

    This is all on a stock 2003 C5 Z06 running AS.

    Next year, or when I wear out these Hankooks, i'll try to find some magnesium C5 rears to run with a spacer on the front and then I can pack on bigger tires up front.  But for now these are lots of fun!

     

     

    Steve A.
    New Member
    New Member
    Posts:19


    --
    17 Jun 2014 11:51 PM

      Can you take a stock C5Z06 rear wheel and have it cut down to a 9.5" width for the front?

    thanks,

     

      

    TedDBere
    Veteran Member
    Veteran Member
    Posts:1821


    --
    20 Jun 2014 07:36 AM
    No
    You are not authorized to post a reply.


    Leroy Engineering Micro Button Sunoco 88x31 Button
    Woodhouse Motorsports
    SPS 88x31 Button G-Loc Button
    Vorshlag 88x31 Button

    Advertise on SCCAForums.com and reach thousands of visitors per day!

    SafeRacer FREE SHIPPING over $99

    Shop for Pirelli tires at Tire Rack. blank



    Sunoco Bottom 468x60 Banner