Announcement

Collapse
No announcement yet.

how much tire is too much

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • how much tire is too much

    Could a 375mm rear and 325mm front tire be run on a s chassis? Would scrub radius cause linkage damage or failure of other parts?

  • #2
    I'd be more worried about wheel bearings personally. But that said, I'd never want more rear tire than fronts on our cars. They already tend towards nose heavy, so same tire width all around is a must.
    '18 Chevrolet Volt - Electric fun hatch for DD duty!


    DefSport Koni Sleeve and Spring Perch Buy!!!
    http://www.nissanroadracing.com/showthread.php?t=5902

    Comment


    • #3
      With the preference of running the same size tire all around, do you think that the performance a 375 width front tire would be past point of diminishing returns?

      Comment


      • #4
        do you mean a 275 front?

        Many people on this site think that if you run tires that are too large, they may not come up to temp.

        I run larger tires on the back because I have more power. It also depends on if it is for track or street: their respective heat tolerances and performance are quite difference.

        Comment


        • #5
          Get rhino tires...... Wider than they are tall.

          Comment


          • #6
            Unless you're autoxing or running 600+HP, then that much tire will only slow you down. You can't get the tires up to proper temp, and the rolling resistance is so high, you lose more time on the straights than you gain in the turns.
            Originally posted by SoSideways
            I don't care what color they are as long as they are LONG AND HARD.
            '04 G35 Sedan 6MT- The DD
            '96 240SX- The Track Toy

            Comment


            • #7
              Originally posted by Matt93SE View Post
              Unless you're autoxing or running 600+HP, then that much tire will only slow you down. You can't get the tires up to proper temp, and the rolling resistance is so high, you lose more time on the straights than you gain in the turns.
              Even with a ton of HP, you can only really hook up what your rear wheel weight + aero can give you for normal force on the tire. And aero downforce should roughly follow your static weight distribution.

              That's why static weight distribution drives tire width more than most realize.


              A 375 front tire on an S chassis with stock suspension is going to be so bad it's not even funny. It's just way too wide to have anything but a huge scrub radius and give all sorts of odd jacking effects due to camber change I'd imagine.
              '18 Chevrolet Volt - Electric fun hatch for DD duty!


              DefSport Koni Sleeve and Spring Perch Buy!!!
              http://www.nissanroadracing.com/showthread.php?t=5902

              Comment


              • #8
                Heh.. kinda related... Was watching a GTA stock car today at MSRH coming out of t17.. soon as the car was pointed straight, the guy would lay into it at about 70mph and leave marks for at least 100yds... fook.
                Originally posted by SoSideways
                I don't care what color they are as long as they are LONG AND HARD.
                '04 G35 Sedan 6MT- The DD
                '96 240SX- The Track Toy

                Comment


                • #9
                  Originally posted by Matt93SE View Post
                  Unless you're autoxing or running 600+HP, then that much tire will only slow you down. You can't get the tires up to proper temp, and the rolling resistance is so high, you lose more time on the straights than you gain in the turns.
                  That is the application, although I will probably be a few hp shy of the 600 mark. I was thinking about running a A11 Avon compound, it seems to be tire that can't handle much heat.

                  Comment


                  • #10
                    Yeah, for autoX applications, the tire width becomes MUCH different equation. since you have much more torque to the ground and less aero drag at <70mph, you can handle much higher rolling resistance.

                    the basics are this:
                    wider tire = better corner speed, better corner exit, slower end-of-straight speed. (better grip, more rolling resistance)
                    narrower tire = slower corner speeds, less exit traction, faster straight speeds.


                    Case in point for road race application:
                    at my race at MSR Houston this weekend, I had the choice of 2 sets of tires:

                    BFG R1, 225/45/17, 24.8" dia. roughly 20 heat cycles. Production date 05009. (5th week of 2009- 4 years old!) Tread is beginning to crack from dry rot.
                    OR
                    Hoosier R6, 245/40/17, 24.5" Dia. about 5-6 heat cycles. 01312 (~april 2012). tread is notably softer and stickier using thumbnail test.

                    I swapped back and forth with both sets all weekend, running the BFGs on Fri and Sun, and Hoosiers on Sat.
                    My fastest lap of the weekend was in Sat qual on the Hoosiers with a 1:50.1.

                    The Hoosiers felt GREAT through the corners and I was able to carry more speed through the carousel- an ~85mph 300deg sweeper.. Exit speed was 92-93mph at a point about 100ft past track-out, and ~112mph at end of the front straight.

                    The BFGs felt like crap through the corners and braking so I had to modify my driving style and line just a touch for a slower entry and later apexing to get drive out. This resulted in slightly higher exit speeds at beginning of the straight and end-of-straight speeds were about 5mph higher.
                    At the same reference points as above, I was doing ~80mph through the carousel, but 96-97mph exit speed, and ~115ish at the end of the straight.

                    This allowed me to outrun a couple cars on the straights, and it's a lot harder to pass me in the turns.



                    for an application where ultimate time is the priority, then go wider and stickier. for an application like road racing, the stopwatch may not be the best tool to use- have to count being able to work through traffic and end-of-straight speed is nearly king on that regard when you're talking less than 1/2 sec difference in lap times.
                    Originally posted by SoSideways
                    I don't care what color they are as long as they are LONG AND HARD.
                    '04 G35 Sedan 6MT- The DD
                    '96 240SX- The Track Toy

                    Comment


                    • #11
                      The other thing with autox is tires can overheat due to the rapid inputs compared to a track. Figure you have 2-3x more corners per time period in autox with much less cooling in between due to the lower speeds.


                      That said, I still don't think super wide tires are going to work well unless you can monkey with the suspension geometry. The whole tire is basically going to be a scrub radius, then you get lots of jacking as you get camber changes which then messes with your instant centers and geometry there as well. This is one of those cases where more probably doesn't always equal better after a certain point.
                      '18 Chevrolet Volt - Electric fun hatch for DD duty!


                      DefSport Koni Sleeve and Spring Perch Buy!!!
                      http://www.nissanroadracing.com/showthread.php?t=5902

                      Comment


                      • #12
                        How feasable would it be to pull the strut inboard to be able to pull the tire inboard? Of course maybe at the time when strut towers starting getting hacked up, it may be better to s%# can the mcphearson setup.

                        Also wouldn't the lower amount of caster needed with the bias tire help the jacking?

                        Comment


                        • #13
                          If it's legal in XP you could switch to an SLA setup, but it would probably have to be custom to handle rims/tires that wide and maintain zero scrub. As Def has also pointed out, you'd need to re-think pretty much everything about the suspension. A tire that wide wil neither need, nor tolerate much static camber, or dynamic camber change from SAI/Caster/jacking
                          Don Johnson (really!)
                          Just so you know.

                          Comment


                          • #14
                            PJ was running 335/18s in the rear and 295/18s in the front IIRC on his S14. I know there is more room in the rear for tire on the S14. You'll have a lot more power and instant torque so you may need more tire. That said, it is always good to be able to rear steer a bit if necessary.
                            Chicago Region SCCA SM # 688 http://www.scca-chicago.com
                            TSSCC SM # 688 http://www.tsscc.org

                            Comment


                            • #15
                              They fit.

                              Comment

                              Working...
                              X