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    Results 1 to 14 of 14
    1. #1
      Join Date
      Feb 2007
      Posts
      1,402
      Country Flag: United States

      275 to a 315 front tire more spring rate?

      Im going from a 275 tire to a 315 tire on the front of my 79 camaro. I currently have the single adjustable ride tech coil overs and will be going to triples.

      Will I need to increase the spring rate with a wider tire? The weight of the car will stay close to the same other then the added weight from the wider rim and bigger tire and also I will be adding a 3 gallon 3 stage dry sump.

      Thanks

      Brandon Slater

      1979 Z28
      1972 Nova
      2015 2500 silverado crew cab duramax


    2. #2
      Join Date
      Aug 2004
      Location
      Boston MA
      Posts
      686
      I wouldn't expect a need for more spring but you may want more rebound in your shocks to control the increased unsprung weight of the tire.
      1967 #s RS

    3. #3
      Join Date
      Nov 2006
      Location
      Hildebran, NC
      Posts
      992
      Country Flag: United States
      .....somebody is getting serious!!!

      Good luck..

    4. #4
      Join Date
      Aug 2011
      Location
      Connecticut
      Posts
      927
      Country Flag: United States
      What spring rates are your running currently?


      1967 Firebird "Poor-Boy Build"
      New updated thread
      https://www.pro-touring.com/threads/...bird-(Updates)
      Follow me on Instagram @NaturalLivingMan



    5. #5
      Join Date
      Feb 2007
      Posts
      1,402
      Country Flag: United States
      Im running a 650 front spring from what I remember off the top of my head
      Brandon Slater

      1979 Z28
      1972 Nova
      2015 2500 silverado crew cab duramax

    6. #6
      Join Date
      Aug 2011
      Location
      Connecticut
      Posts
      927
      Country Flag: United States
      Quote Originally Posted by brownz View Post
      Im running a 650 front spring from what I remember off the top of my head
      I honestly think triple adjustable coil overs are going to be absolutely useless unless this is a competition track car that requires the fine tuning. 650lb springs seem really soft id at least run 800lb springs


      1967 Firebird "Poor-Boy Build"
      New updated thread
      https://www.pro-touring.com/threads/...bird-(Updates)
      Follow me on Instagram @NaturalLivingMan



    7. #7
      Join Date
      Oct 2004
      Location
      Indiana
      Posts
      1,371
      The reason you might consider a stiffer spring is that with a wider tire you will potentially have more lateral grip. More lateral grip will load the suspension harder. To optimize this situation you would typically have to increase spring rate and/or swaybar rate to resist excess body roll. With the extra spring and/or swaybar rate, more shock rebound force will normally be required to control this extra energy.

      Having said all that theroretical stuff...you won't magically get 2 seconds faster on the autocross just by installing an extra 3+" of tire on the ground. As you sneak up on your lateral grip limits [and driving ability, just be aware of some of the refinements you might have to make to optimize the combination. Changing one thing at a time typically works the best.

      As was suggested above, the triples are a fine tuning tool, useful mostly to those with the talent and ambition to test their combination and log the changes to optimize their particular car. Although we will cheerfully cash your check, I might recommend spending some time optimizing your current combination before making that change.
      Bret Voelkel
      Director of Innovation Fox Powered Vehicles Group
      Founder/ Former Owner
      RideTech/Air Ride Technologies, Inc.

      How do you spell Impossible?

    8. #8
      Join Date
      Aug 2004
      Location
      Boston MA
      Posts
      686
      I'm "on the ropes" regarding this site but Bret's post certainly helps. Rational and well tempered.
      1967 #s RS

    9. #9
      Join Date
      Feb 2007
      Posts
      1,402
      Country Flag: United States
      Bret,

      Thanks for your reply. I am wanting to get more involved with the tuning and adjustments on the car. I do not have much experience with this but would like to become more educated. I do need a TON more seat time and I know for a fact the car will not get better with just a bigger tire. If it was that easy we all would run huge tires lol.

      Would you recommend any literature on suspension/shock adjustments ans setups? Maybe a training course?
      Brandon Slater

      1979 Z28
      1972 Nova
      2015 2500 silverado crew cab duramax

    10. #10
      Join Date
      Sep 2010
      Location
      Beach Park IL
      Posts
      2,838
      Country Flag: United States
      Quote Originally Posted by brownz View Post
      Will I need to increase the spring rate with a wider tire? The weight of the car will stay close to the same other then the added weight from the wider rim and bigger tire and also I will be adding a 3 gallon 3 stage dry sump.

      Thanks
      Yes you will need more spring. Like Bret said, more tire = more grip = equals more spring. That said, how much track time do you have on the car now?

      Quote Originally Posted by wendell View Post
      I wouldn't expect a need for more spring but you may want more rebound in your shocks to control the increased unsprung weight of the tire.
      Compression controls unsprung weight, rebound controls the sprung weight. It's more technical than that, but that is the easiest way for me to grasp it.

      Quote Originally Posted by Buryingthesun View Post
      I honestly think triple adjustable coil overs are going to be absolutely useless unless this is a competition track car that requires the fine tuning. 650lb springs seem really soft id at least run 800lb springs
      The triples are fantastic shocks even if your car never sees a race track. The roadster in the avatar is a perfect example. That car is light at 2400 pounds, but still carries a full size 9" rear end and a ridiculous wheel and tire package bringing unsprung weight in the rear to over 300 pounds. It takes a lot of spring to control that but a lot of spring in a light car rides like poop. Enter high speed compression adjustment. Soft springs and dial in the high speed and no more bottoming out, still rides nice. WIN!

      Quote Originally Posted by wendell View Post
      I'm "on the ropes" regarding this site but Bret's post certainly helps. Rational and well tempered.
      It is VERY hard to find good tech on any forum. It doesn't matter if it is cars, quilts, or photography. The tech here is as good as it is anywhere.
      Donny

      Support your local hot rod shop!

    11. #11
      Join Date
      May 2006
      Location
      Barrington, IL 60010
      Posts
      206
      Country Flag: United States
      Rides like 'poop', you say? Hmmm...
      Rich

      'Wicked Witch'...1969 Camaro, Mast Motorsports LS-3, Magnum T-56, DSE suspension & BFG Rival-S on Forgeline wheels.
      A herd of stock #'s-matching '69 Camaros.

    12. #12
      Join Date
      Feb 2007
      Posts
      1,402
      Country Flag: United States
      Donny

      Thanks for you input.

      I know things will need to be changed wit the wider tire. I hope to get a good idea off my current setup and maybe get some feed back off some friends I have local to me on what would be the best way to go. I do want to have the adjustable with the car. Like you said a ton of factors and having ride quality on the road is also what I'm looking for as I do drive the car as much as I can. WHEN its not apart lol

      as for track time I have only had the car out a few times and each time have changed something. That is another reason that I would like to go with the triples is so that I can start to tune the car knowing that I will not have to change the shocks again
      Brandon Slater

      1979 Z28
      1972 Nova
      2015 2500 silverado crew cab duramax

    13. #13
      Join Date
      Dec 2006
      Location
      Barrie, Ontario, Canada
      Posts
      108
      Country Flag: Canada
      I have 315 on the front the ride is ok except when you get into ruts, like from transport trucks. You get busy on the wheel at that point.

      Used to be known as 455regal

    14. #14
      Join Date
      Aug 2010
      Location
      now In Dandridge, Tn.
      Posts
      1,301
      Country Flag: United States
      I'm going to preface this with a disclaimer, that, what I do, almost in no way is equitable information to anyone. When I asked about wide front tires (335) all I heard was "bumpsteer" "trammelling" ...bla bla bla. Have no fear, front grip pays off. From my own experience, spring rate is the same. But, add twice the % of bar rate as you do tire size. From 275 to 315 is roughly a 15% width increase, so add 30% bar rate. Don't know the bar rate? scrap the bent bar and set up a tuneable splined bar. study the rate charts from Speedway Engineering and you get a close estimate of your current bar. To me, sway bar tuning is a big deal, but, I'm a "soft-spring / big bar" guy. Reduce static camber, increase static caster. As to shocks and the like. I run ridetech Triples. Donny is right about controlling unsprung wt., and seat time pays off over all else. What would I do? Get the tires in with what you got. Buy a heat gun and a caster/camber gauge. Maximize the current parts. THEN, try a bigger bar, then a bigger one, until it has a nasty push. - then back up a bar. By this time you will have a shock setting that has become a standard with the single adjustables, and if you are pushing the edge, you may be out to the limit of the shock. Then, call the guys at ridetech, discuss what you have. Un-bolt a front and rear shock and sent it to them. You want new shocks valved so that the "middle" setting is close to what you run by then, with your corrections factored in. (like "I maxed out front rebound") Yes, this is the fine tuning at the end, but it makes all the difference. Go in one step at a time and take notes and it will all pay off. Take note that Brett was trying to un-sell you a set of shocks. He wants you to succeed. There are great guys here willing to help, just ask. Good luck with the car.





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