Tire Shake

Discussion in 'The Comp Buzz' started by Rob Harrison, Sep 4, 2011.

  1. Rob Harrison

    Rob Harrison Well-Known Member

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    What is tire shake? I have never had the same answer from anyone I thought would know. There seems to be a belief that clutch operation has something to do with it, but what about shake with a converter or does it happen with a converter?

    Seems to be a more common problem in Pro Stock, now, for whatever reason. What causes it would be tough to avoid, if you don't know what it is in the 1st place and there may be no way to avoid it.

    I've heard people say, that car used to shake all the time, this new car doesn't shake at all.....no wonder you don't get the same answer about what it is.
     
  2. B/AA 529Y

    B/AA 529Y Member

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    Rob, it definitely happens in auto cars because both my 700 in and 500 in stuff shook at various times, almost always at low wheel speeds. I've got numerous Racepak run graphs showing shake of various magnitudes. Of course in a 4-link car, too much bar can cause shake.

    If I really wanted to find out about shake, I would find an expert at Goodyear and ask them.
     
  3. Ray Hadford

    Ray Hadford Member

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  4. Rob Harrison

    Rob Harrison Well-Known Member

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    From what you are suggesting, Steve, and the video, "tire wadding up", not to over simplify, seems like a tire pressure, rim width, trip?
     
  5. comp 670

    comp 670 Active Member

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    I can only speak from my experience with the Thunderbird.. It's seems to be all about wheel speed.Too much or not enough and you get tire shake. Most of the time it is not enough wheel speed and you actually "run over" your own tire. I have vid of the t-bird doing that. The tire wads up in front of the contact patch and then rips itelf loose from the track and thats the "shake" you see and feel.The rim actually starts and stops instead of spinning at a constant rpm.....

    Keeping the tire "round" is what wheel speed seems to be all about. To little and you run over it,to much and you "square off" the tire and then it shakes.
     
  6. Rob Harrison

    Rob Harrison Well-Known Member

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    So what is the shake, tire biting then releasing then biting, or the out of shape tire vibrating, or the power trying to overcome the bite and the transition is screwed up. Still, what is vibrating the hell out of the car.......welds break....
     
  7. comp 670

    comp 670 Active Member

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    If you look at a slo mo vid it looks like the actual "shake" is the tire and rim starting and stopping,then the tire starts bounceing off the track as it gets worse.

    It is BRUTAL on stuff,I have ripped a rear housing in half,broke brand new wheelie bars in half,had the "X" brace under the trans snap,come thru the tinwork and hit me in the chin,broke driveshafts,innercooler,chunked tires and a bunch of other stuff I prob forgot about....

    I know my new car will still shake sometimes but I am sooooo looking forward to not having the t-bird rattle me to death anymore...
     
  8. Rob Harrison

    Rob Harrison Well-Known Member

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    300 inch 2500 lb + cars, N/A, don't shake, but they all run more tire pressure. Would it be safe to say, if you put more air in your tires, the tire could not distort and cause the shake. You may blow the tires off, but you wouldn't shake, there's some message here, maybe tire design (sidewall) has more to do with it than anything, we can't run more than 5 lbs or the car will jump off the ground, shake sometimes but can't cure it with more tire pressure.

    So the tire shake mystery continues......
     
  9. Adger Smith

    Adger Smith Member

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    Rob,
    A long time ago.. Back when ... I saw a list on Garlits trailer door that explained tire shake. I think I saw it later in a magazine, too.
    It was two lists
    1 Too much clutch Too little clutch
    2 Too much air pressure Not enough air pressure
    3 Too much power Not enough power
    4 too much bite/traction Not enough bite/traction
    5 Ect Ect
    6 Ect Ect
    7 Ect Ect

    The lists went on and on...
    Can't remember it all, hence the ECT's.
    You get the idea...
    You think Big Daddy had it figured out? :~)
    Good Luck!
     
    #9 Adger Smith, Sep 5, 2011
    Last edited: Sep 5, 2011
  10. Bruce H

    Bruce H Member

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    Saw the same door. At the bottom of the list in big letters was the word ME.

    Bruce H.
     
  11. caveman

    caveman New Member

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    First time post here. I can share some of my 2nd hand experience with tire shake. For a few years, I sold tires at the Division 6 divisionals. As others have mentioned here, the cause of tire shake is complex and while reducing tire pressure will help one racer, raising the tire pressure could help another. I personally believe that stiffer sidewalls can help reduce tire shake. For top alcohol funny car teams, there was a big push to move to beadlocks and tubeless liner wheels (maybe there still is, I haven't been "involved" for a couple of years) because of the reduction in rotating mass. In any event, the few teams that I helped to make the switch had big problems with tire shake. I believe that this is because the tube and liner combo supports a significant portion of the sidewall. Once that support is gone, a new tuneup is required to get the car to launch "happily". They all ended up going back to their liner/tube setups.

    I had one comp customer that tried virtually everything, more air pressure, less air pressure, stiff tires, saggy tires. That vehicle shook hard and often and in almost every perceivable way (at the hit, out 50', top of 1st, etc.). I think the only thing that solved the problem was a slighter smaller motor and then he was good to go.

    Tire shake seems to be more prominent in clutch cars, but as Mark noted, once you start putting down stoopid power, I don't think the method of delivery matters anymore. I believe that is also why tire shake seems to be more prominent in pro stock than it used to be. Power levels continue to increase.

    Best of luck to everyone, still my favorite class to watch!

    --Bob
     
  12. Rob Harrison

    Rob Harrison Well-Known Member

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    I was lucky enough to talk to Bob Glidden about this.....at the 1978 Fallnational's in Seattle, he was kicking everyone's ass, and I asked him, what would you consider the most important thing a drag car needs to do when leaving the line? He said without hesitation, spin the tires. I never did get what he meant by that, but I think I'm starting to get it, when you spin the tires....with some % of bite, the car is accelerating at an efficient rate. If they bite too much.......maybe THAT is shake. Doesn't appear to be any clear formula here, seems kind of silly, such a high tech sport with no way to pinpoint the issue.
     
  13. TobyG

    TobyG New Member

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    From my experience if you don't keep the tire round, you have a pretty good chance to shake the tire. There are thousands of variables to consider but the bottom line is you need spin.

    I worked with Kurt Johnson for almost ten years doing his data. He could make a car go into tire shake while it was still sitting in the pits. Of course that is a joke but he was always one of the guys that could make a car shake. You would not believe the difference in tire speed between his good runs and shake runs. It was always at the point we thought it was almost out of control but that car would haul ass when he kept it up on the tire. If he hit the wheelie bar to hard and set the tire, he was screwed.

    I worked on the Winston TF car for four years doing the same. We would never have any violent tire shake but more often than not, our tire smoke runs came from tire shake. Not overpowering the track and immediately smoking the tire. The tire would first shake and then lose grip while we were applying more clutch, not a good scenario.

    One thing we did on both cars was have alot of counts per revolution of driveshaft and sample as fast as we could. We had a Pi Research data system that would let us sample 500 times a second and we had 20 counts per revolution. You will shit the first time you see dsrpm sampled like that. The first time I did it on the Winston car, you could see the dsrpm start to shake when the clutch started to lock up. AJ thought I had bad data and didn't believe me until I showed him the inline accel that we also sampled at 500hz. Right when the dsrpm started to shake the inline accel dropped.

    I don't know how you have your data acq system set up, but the first thing I would do is sample as fast as you can and give the recorder as many counts as it will handle. I know the V300 can only handle 4 counts per rev. I am pretty sure RacePak fixed that with the SD.
     
  14. Patrick Hale

    Patrick Hale New Member

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    Top Secret Tire Shake Formula

    Rob - the formula is tire speed at the contact patch vs. ground speed . . . also known as the "slip ratio". When the tires are "dead hooked" the slip ratio is 1.00. When the tires are going 10% faster than the ground speed the slip ratio is 1.10.

    Many, many years ago I worked with a couple of world champ Pro Stock tuners who put "radar systems" on their cars to measure ground speed . . . very high tech. I'm sure better systems are being used today since front tire RPM sensors don't work well when the front tire is off the ground. Look at all the high speed video cameras being used to "digitize" the Pro Stock car launch. :rolleyes:

    Patrick Hale
    www.DragRacingPro.com
     
  15. comp 670

    comp 670 Active Member

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    Toby, is increasing the count rate on the driveshaft just as simple as a new ring with more magnets and then resetting the parameters that the racepack counts at?
     
  16. comp 670

    comp 670 Active Member

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    Just looked at Racepaks website and they show a 8 magnet ring as a option instead of the standard 2 mag ring.They list it for "auto equipped" cars to pick up the driveshaft speed sooner.... They also have 4 mag rings.

    So I assume you put the 8 mag ring on then reprogram the Racepak and your good to go?

    There is prob a bunch of guys on here going Sh@!,why are they talking about this? This is a secret!! lol....

    I've allways wondered about doing this,now I am going to do it for sure with the new car before Vegas...
     
    #16 comp 670, Sep 6, 2011
    Last edited: Sep 6, 2011
  17. TobyG

    TobyG New Member

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    Exactly. Get away from the magnets and make a steel toothed ring. When you do, make sure you design it so the two bolts that clamp the ring together is away from the sensor or use stainless bolts, otherwise the sensor will trip on the bolts too. If you have a reed switch style dsrpm sensor, with a two pin connector, you will need to change to the hall-effect style sensor. It has power, ground and signal.

    Pat makes a good point about matching tire speed to ground speed too.

     
  18. TobyG

    TobyG New Member

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    Don't worry about it, they will just think you are running traction control :p

     
  19. comp 670

    comp 670 Active Member

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    Will the 8 magnet Racepak ring at least be some improvement over a two mag setup?
     
  20. comp 670

    comp 670 Active Member

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    I'm used to that...Every time I made a good clean run in the T-Bird(and that was not often) they would stop me at the scales and make me pull all the tin out to check for traction control....
     

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