Killer Tire shake Need Help.

[ricci32]

My friend has a former tf 2001 sterling chassis dragster he has raced the car for several years , this season he stepped up his engine program using a blown bbc 496 inch engine the car has always had a problem with tire shake but this year has been horrible. he runs a large rear tire set up, I will get the exact size. with the prior engine he ran mid 6's with a top speed of 210mph the car has always run a big block chevy. any idea on thing we could try or look for. the car looks like the tire rolls over its self and has bent and broken the wheelie bar in the past. the tire shake is so violent that it has damaged the car on several past runs. there is no driving through the shake. any suggestions would be appreciated.

[dreracecar]

Clutch or PG ?  Waiting on tire size(manuf) and rim width and tire pressure, launch RPM's?

[ricci32]

hoosier 33.5 17 16on a 16x16 rim 6psi launch  2500

[ricci32]

powerglide trans

[dreracecar]

Dont know about Hoosiers, but 1/2" increments with Goodyears  is a door car tire,  but besides that, trying to run a  fuel tire combo on a light weight dragster with a PG and low RPM launch does not work. Too much tire and no bottom end HP (@ 2500 rpm) is the problem.   I always recomend 12" on the tire width and keep the rim 2" narrower. He's not going to like what I said because it means he is going to spend money on rims and tires and will just try and make what he has work instead of fixing it. With todays racing surfaces and prep an tire compounds, 12" of rubber is more than enough.

[masracingtd1167]

Larry I am guessing that you are talking about Charlie Bensons car ? That is a really big tire that he runs . Dose it shake right at the hit or dose it spin into a shake . A lot of the guys with big HP Top Dragsters are running that Mickie Thompson tire with a lot of success . It would be nice if he could borrow a set from one of the Pro Comp guy's at Epping . What low gear dose he run . 

[ricci32]

not sure on gear but it shakes right at the hit violent shake.

[ricci32]

He likes the top end speed with the larger tires if he gets a good launch. Charlie does an amazing job for a guy who builds everthing himself motors trans and rears and the speed he runs is mind blowing. but he is still a budget racer pushing his equipment to the max.

[masracingtd1167]

Larry It sounds like it is dead hooking . The only thing that I can think of would be to lower the rear tire pressure like a 1/2 lbs and try it . The reason that I mentioned the Mickie's is we tried a set on my sons Top Dragster when we out at Norwalk I know it is not the same as Charlie's but we were spraying with 2 kits at 300 hp each and brought the m both in right at the hit and the tire was smooth as can be . It dose not wadd up like the Hoosier . He ran his quickest ever e.t. at 6.54 with no shake or Quiver . Scott Hall would be a good guy to talk to . He might have some good idea's . See you guy's at the Hot Rod Reunion we can b.s. a little !   

[dreracecar]

Rear motor top dragsters have different dynamics then a Front engine dragster

[rooman]

I agree with the "dead hook" assessment. That is a lot of tire to get slipping with 2500 rpm at the hit. Pump the tires up and / or lower the wheelie bar to get some wheel speed leaving (or do as Bruce suggests and put the right size wheel/tire package on the car). Bigger is not necessarily better.

Roo

[masracingtd1167]

Rear motor top dragsters have different dynamics then a Front engine dragster

I understand that but they both need wheel speed to go from a to b and the Mickie Thompson tire that I suggested is narrower than the Hoosier I think the tread width is 14 1/2 wide but I think the big difference is the side wall with the same air pressure as the Hoosier they are much smoother . 

[ricardo1967]

Rear motor top dragsters have different dynamics then a Front engine dragster

Would it make sense to think that, for comparable tires shakes, it would be felt more strongly in a FED than in a RED?

[dreracecar]

Has nothing to do with it.  RE dragster has all the weight in front of the rear axle and further out along with a much stiffer chassie because the rails are further apart. Tire plants harder because the chassie is stiff, Try pushing down at the motor and see how much chassie flex, again at the rollcage, again at the front of the footbox. Now with a FE dragster the motor is out the same  (relative), but nothing ahead of the motor and a fat ass driver counter-balencing the front weight by sitting behind the rear. Frame rails at the motor are narrower and the chassie will flex more. At the hit the tires are trying to drive under the engine on both cars, The FE will flex and arc in the middle to a point to where without enuff HP the flex will reverse itself and spring back unloading the rear tires, then tires catch up and frame flex/arc happens again, then guess what, back it goes into reverse and so on. If you have enough hp to maintain the arc till top HP is acheaved and carry it through its a good pass. A RE dragster does not flex as much so it does not unload the rear tires because the weight to the front is constant

[ricardo1967]

Has nothing to do with it.  RE dragster has all the weight in front of the rear axle and further out along with a much stiffer chassie because the rails are further apart. Tire plants harder because the chassie is stiff, Try pushing down at the motor and see how much chassie flex, again at the rollcage, again at the front of the footbox. Now with a FE dragster the motor is out the same  (relative), but nothing ahead of the motor and a fat ass driver counter-balencing the front weight by sitting behind the rear. Frame rails at the motor are narrower and the chassie will flex more. At the hit the tires are trying to drive under the engine on both cars, The FE will flex and arc in the middle to a point to where without enuff HP the flex will reverse itself and spring back unloading the rear tires, then tires catch up and frame flex/arc happens again, then guess what, back it goes into reverse and so on. If you have enough hp to maintain the arc till top HP is acheaved and carry it through its a good pass. A RE dragster does not flex as much so it does not unload the rear tires because the weight to the front is constant

Thanks for the lesson Bruce. Keep 'em coming.