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Box Stock Wheel Runout

Discussion in 'Ask The Pros' started by xtremethings, Sep 22, 2020.

  1. xtremethings

    xtremethings Pinewood Ninja

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    We’re running box stock rules at this year’s local Scout championships and I’m having a hard time getting a pair of good wheels together for the rear. The original set during the pack race back in February had less than a 0.0035 runout and matched in weight to 0.001 of a gram. We would have used those wheels, but one was damaged from being dropped by somebody working the pits just before the last run.

    I went through about 50 premium #15 wheels with consistent bores that were relatively true and couldn’t find anything with less that 0.005 runout. Not a huge deal, but the the weights weren’t dead on and spin vibrations weren’t the best.

    I’m thinking vibration is the biggest killer at this point, but what’s the thought on the maximum runout to not even consider using them?
     
  2. Jupiter 2.9

    Jupiter 2.9 Workshop Leader Pro Racer

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    If they were premium wheels why were they not true to start with ?
     
  3. xtremethings

    xtremethings Pinewood Ninja

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    Premium mold matched with zero machining.
     
  4. Roadrunner

    Roadrunner Pinewood Ninja

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    I’ve gauged many stock wheels in my search for good ones. The best I’ve found read .004 runout at center of tread. Most are much worse. That number doesn’t tell us if it is hop or wobble that we are seeing. That is worth knowing because much of the imbalance caused by hop can be corrected with a lathe ( if allowed ), you can’t fix wobble.
     
  5. Roadrunner

    Roadrunner Pinewood Ninja

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    Well, I don’t think it’s practical to fix a wobble. Maybe it could be done, but lots of things could go wrong...
     
  6. xtremethings

    xtremethings Pinewood Ninja

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    Since I’m basically dealing with Box Stock rules, any wobblers go directly into the future BASX machining bucket.
     

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  7. T-Bone Racing

    T-Bone Racing Pinewood Ninja

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    I have built a Box Stock before, but I have never raced it because of the wheels. I dislike the class because of this. I bought about 7 sets of wheels hoping for 3 decent ones. Not perfect, but decent. Al, of them either wobbled, or had runout. Some were as low as .002 in runout, but when I put them on the track, they wobbled. And some were probably even .008 as well. It’s a hard class to build for, but I’d look for ones with the least vibration first, then look for runout. Just my opinion.
     
  8. xtremethings

    xtremethings Pinewood Ninja

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    It’s a scout race so there’s no way to avoid this race. I’ve been doing rail riders for the last three years and this box stock thing is driving me nuts.

    The max diameter 0.089 BSA axle thing seems to contribute to the problem. I use a 3 degree drilled cant in the back and it seems like there’s enough bore/axle slop that the entire tread width seems to make contact. That’s based on a visual wear pattern after a few races. The wheels always migrate out so maybe it’s nothing to worry about.
     
  9. T-Bone Racing

    T-Bone Racing Pinewood Ninja

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    The axles don’t help, and I’m sure they cause some vibration. You also don’t want to over polish the bores. That will make even more bore/axle slop.
     
  10. xtremethings

    xtremethings Pinewood Ninja

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    I found that out the hard way unfortunately.
     
  11. T-Bone Racing

    T-Bone Racing Pinewood Ninja

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    Most of us have, Lol
     
  12. Loud2ns

    Loud2ns Rail Runner

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    Yep, that's the truth.
     
  13. xtremethings

    xtremethings Pinewood Ninja

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    I always try to triple what I’m working on and just except the fact that something is gonna get tossed. Now I have so much stuff that it only makes sense to move on to bigger things after the Scout racing is over.
     
  14. HurriCrane Racing

    HurriCrane Racing PWD Royalty 25+ Pro Race Wins! Pro Racer National Champion

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    .003 runout is realistic but you will have to sort through quite a few wheels. Make sure you are testing the wheel on the surface the wheel will ride on. Inner tread surface for rear wheels and outer tread surface for DFW.
     
  15. xtremethings

    xtremethings Pinewood Ninja

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    That’s exactly what I do and have had great success with it. I must say it’s a lot easier dealing with lathed wheels though.
     
  16. xtremethings

    xtremethings Pinewood Ninja

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    Thanks for all the help!!! Turning in the car tomorrow and fingers crossed for a win.

    07B77E3E-F49C-48BF-B5DD-5E7DC07B83BE.jpeg F5EA3141-1850-49ED-9F49-7132CFAF223B.jpeg
     
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  17. Loud2ns

    Loud2ns Rail Runner

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    xtremethings likes this.
  18. Ballistic Racing

    Ballistic Racing Workshop Leader #1 Ranked in the USA Pro Race Winner Pro Racer

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    That’s some SICK graphics! Gotta love the Big Boy serving it up proudly!
     
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  19. Mojo Racing

    Mojo Racing National Contender Pro Racer

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    That is my kinda car right there ! ! ! ! I dig cars that have cool graphics on them. I like for the car to say something other than, "I'm green."

    Very cool!
     
  20. xtremethings

    xtremethings Pinewood Ninja

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    My boy named his car Bob and it’s always fun building a killer looking car with him. He started off thinking form was more important than function until he realized what it would take to get a shot at the title, but it sure is nice when you’re able to print whatever he’s able to dream up.
     
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