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  1. #1

    Default RR Mod question.

    In general. What are some things that can be done to help the car scotch up on the RR.

  2. #2
    Join Date
    May 2007
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    Batavia, OH
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    Are you referring to the Lr getting up, but using the Rr as a pivot, instead of compressing the Rr a bunch like the old days?
    Droop isn't the problem.

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  3. #3

    Default

    Thats what i am talking about.

  4. #4
    Join Date
    May 2007
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    Your rr has to be dynamically stiff. The rear of the car needs the necessary cg height and instant center location. (light lr wheel rate)
    Droop isn't the problem.

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  5. #5

    Default

    Do u think running a xmas tree style bump would help it as far as planting the rr or do you think it would end up being loose off. Say 175 or 200 rr spring letting the car get over and as it gets into the bump wheel load spikes

  6. #6
    Join Date
    May 2009
    Posts
    1,319

    Default

    The Xmas trees bumps need a pretty deep engagement before they add much rate, IMO we arent traveling the RR as far as years past not sure it would be effective!

  7. #7

    Default

    My car travels about 3.5 inches on the rr. I was thinking about putting a bump on there and setting the gap about 1 inch at ride height. With the xmas tree bump it should hit the bump pretty quick but not react until the car has almost travelled the max. Just thinking outside the box not sure what effect if any there would be

  8. #8
    Join Date
    May 2007
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    Default

    Quote Originally Posted by racer22 View Post
    My car travels about 3.5 inches on the rr. I was thinking about putting a bump on there and setting the gap about 1 inch at ride height. With the xmas tree bump it should hit the bump pretty quick but not react until the car has almost travelled the max. Just thinking outside the box not sure what effect if any there would be
    I would start at 2" Gap, then adjust from there.
    Droop isn't the problem.

    Arizona Speedway - 2 ........ Brushcreek -1
    Alltech -1 ........ Eldora -4
    East Bay - 6
    Florence -1
    Atomic -4
    Tazewell -1
    Moler -1
    Portsmouth -1

  9. #9
    Join Date
    Jan 2021
    Posts
    3

    Default

    If rules won’t allow the use of a bump stop on RR are there other ways to achieve a rr to be dynamically stiff. Seems like the fast way around now days is to get car to pivot off rr and not flop over. Would a greater split in rr bar lengths help?

  10. #10
    Join Date
    May 2007
    Location
    Batavia, OH
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    Stiffer spring, move roll center, start with more load at ride height. Stiffer shock. More rr bar angle works if on gas. More bar split is a lot like a stiffer spring.

    All these suggestions have side effects. But, they are different.
    Droop isn't the problem.

    Arizona Speedway - 2 ........ Brushcreek -1
    Alltech -1 ........ Eldora -4
    East Bay - 6
    Florence -1
    Atomic -4
    Tazewell -1
    Moler -1
    Portsmouth -1

  11. #11
    Join Date
    Jan 2021
    Posts
    3

    Default

    Quote Originally Posted by MasterSbilt_Racer View Post
    Stiffer spring, move roll center, start with more load at ride height. Stiffer shock. More rr bar angle works if on gas. More bar split is a lot like a stiffer spring.All these suggestions have side effects. But, they are different.
    Really appreciate the advice mastersbuilt-racer. If I started with more Load at ride height would that make car want to tail out off turn? And if so, to compensate would it be a good idea to take some rear steer out?

  12. #12
    Join Date
    Jan 2014
    Location
    Johnson Creek, WI
    Posts
    116

    Default

    Also remember that if you go to a stiffer spring or more load on your current spring you will not travel as much so you dynamic bar angles will be higher. That could end up making you looser on corner exit so you may want to adjust accordingly.

  13. #13
    Join Date
    May 2007
    Posts
    2,855

    Default

    More bar split will decrease indexing, a little.

    Can you run a bump stop? If so i would do that for sure.

    If not, you could play with chaining the RR down to ride and preloading a 150 lb spring, and let it coil bind at the bottom of travel. This would be dicey thou, and not recommended.

    At the end of the day thou, dynamic stiff is not the same as starting out stiff. Make yourself a X Y chart, travel vs load and look at the curve of a simple 200lb spring (linear, or so) vs a 150lb and a bump. The secret is in the curve, but finding the right point can be a uphill battle.

    Just say no...

  14. #14

    Default

    Weight placement can have a good result in getting rr to scotch.

  15. #15
    Join Date
    Jun 2007
    Location
    Wisconsin
    Posts
    270

    Default

    If you get some good practice sessions where you can go in and out freely. You could try some spring doughnuts. Keep adding them, taking a couple of laps in between without changing anything else. You should be able to see if you are going in the right direction.
    If you are then start stiffening the spring itself.
    I've always like keeping the bar split on the right rear consistent; moving them both at the same time.

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