Author Topic: Tire shake.  (Read 2487 times)

Offline GlennLever

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Tire shake.
« on: November 14, 2016, 09:30:59 PM »
I have never had enough power to worry about tire shake.

Now I need an education.

Glenn
Glenn R. Lever
Rochester, New York 14617-2012
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Offline dusterdave173

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Re: Tire shake.
« Reply #1 on: November 15, 2016, 04:39:28 AM »
I experienced it once--and I have a pretty weak little 350--I promise I don't Ever want to feel it again!
Left the line with wheelie bar high and Max RPM I could muster--it hit the bar so hard that it must have unloaded tires is all I can figure--it was awful--almost knocked me out--
I have always had a fascination with fast cars at the expense of more normal character development

Offline rooman

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Re: Tire shake.
« Reply #2 on: November 15, 2016, 05:56:57 AM »
One thing that seems to help on Mark Vaught's car is the Goodyear tire. The Comp elim Goodyear is very light and thus has less mass if it does try to quiver. The trick is to not "dead hook" any tire--some slippage leaving the line is essential in most cases. On a really tight track I will lower the wheelie bar some to get that wheel speed.
   For example the car that Derek McCuistion purchased to replace the one that burned to the ground in his trailer fire is an older top fuel chassis and has the motor a little far back for his 7.50 driveline. At his first outing at Norwalk and also at Bowling Green he was fighting tire shake. He added some ballast in the nose after Norwalk but the car still had too much static weight on the rear as was rotating hard at the hit. At BG I had him lower the wheelie bar (a lot). The car still tried to rotate but it did not get a run at the bar and with the wheel on the ground early the tires spun just enough and the car went down the track.
  Glenn, as noted by Dave, tire shake is not necessarily a function/result of too much power as too little grunt can produce the same result. I will always remember a photo from back in the 70/80's of a home made sign on the door of a pro team's Chaparral trailer in the pits. It listed all the causes of tire shake:    Too much power
                                                Not enough power
                                                Too much clutch
                                                Not enough clutch
                                                Too much tire
                                                Not enough tire
                                                Too much track
                                                Not enough track  etc.

Roo
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Offline JrFuel Hayden

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Re: Tire shake.
« Reply #3 on: November 15, 2016, 02:41:45 PM »
I agree with Rooman, "Too much, not enough", etc.  Too much power= too much tire speed, Not enough power= not enough to get "Up" on the tire, Too much clutch= hitting the tire too hard, not enough clutch= not getting up on the tire, too much tire= again can't get up on the tire [ dead hook, like Super Comp, stop and go cars], not enough tire= too much tire speed will shake, too much track= hard to get enough tire speed, not enough track= too much tire speed.
Confusing isn't it, they all can be a reason why it's shaking your fillings out.
This is what I do; low wheelie bar 2" [ so your toe fits under the wheel], this allows the front wheels to come up some, but not enough to hit the WB hard and unload the slicks. We set the WB with the driver in the car, because of tire squat. We run the 31x12x15 Goodyear that are the lightest at 26lbs each, at 5 3/4 to 6 1/4 lbs on 11 or 12" wide wheels.
If you are lifting up the wheels hard and fast put at least 20 lbs on the nose. Car balance is a real trick, you have to work on it. RacePak even has a WB pressure sensor to measure how hard it's hitting the WB. Of course if you don't have a RacePak, just keep adding, subtracting ballast.I have seen cars add 20 lbs on the nose and pick-up a tenth.
We have one JrFueler take his WB off, but added 60 lbs to the nose, trying to get rid of the "J" Hook from the RacePak driveshaft curve. And they run 7.13-7.015 with an all iron non raised runner all iron SBC on alky. "J hook is where the driveshaft curve [ tire speed] shows the tire speed grow fast, then hook up, and bring down the g meter, and engine RPM.   
I relate to the too much clutch question to my stall on my converter, I have run a looser[ higher stall] converter so it hits the tires a bit softer, and still have 1.01-1.04 sixty foots. Also running a 1.68 first gear has helped hitting the tires too hard, for 4 years now.
I hope some of this helps guys.
Maybe Glenn will move this posting to "Jon's Wheel House"
Jon
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Offline coupemerc

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Re: Tire shake.
« Reply #4 on: November 15, 2016, 03:10:52 PM »
So...I have had two back operations (ruptured disks) and have limited movement of my left foot caused by tire shake from driving Top Alcohol Dragsters. I've temporarily lost vision, broken a chassis, broke a carbon fiber wing and blown a zoomie header pipe into the grandstands all due to tire shake.
I'd like to add one more thing to the great responses above. Running the fuel system too lean will cause shake too. Especially on blown cars with a lot of blower overdrive. On the starting line the boost can come up quicker than the fuel delivery and you go lean, hurt the motor and shake. Try to always run them slightly rich. Don't fall for that "lean and mean" crap. They run on fuel.

Offline wideopen231

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Re: Tire shake.
« Reply #5 on: November 15, 2016, 04:10:50 PM »
Agree^^^^.Folks have wrong idea about lean thing.Idea is to see how much fuel you can make it burn.As Rooman and Jon stated is abalancing act of power ,wheel speed and track.I always found that driveshaft speed would tell you whyich way to go.Most of the time I noticed dip is DS speed before shake,telling me more clutch was needed.Key word MOST.
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