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Discussion Starter #1
helping freind out with his small block mustang we are having horible tire shake issues. It is a 89 mustang back halved ladder bar, 2900 lbs total 33/16 tires. we run a 417 yates headed motor made 858 all motor, power glide. it has a plate kit/ and fogger. with 150 in the plate we are getting very light tire shake ok 60 ft 1.35 leaving at 4000 on trans brake.
tires set between 6 3/4 and 7 1/4. ran a 8.8 154. we tested yesterday
using the fogger many hits with 300 kit, we have a box we can delay hit up to 5 tenths with tires at 7 1/2-1/4 hitting 300 shot we would get horrible tire shake, ended up braking the yoke on the dana 60. i don't know chassis tuning the best, we just keep testing. the one hit we easied
it out with 5 tenths delay we got a 5.5 128 1/8 mile with a 1.37 60.
any suggestions would be apretiated.
walter grosse
the car can be seen on the web site below under rays coupe on the projects section.
 

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Are you sure it's tire shake you're feeling? A 60' time of 1.35 doesn't sound like a tire shaker. My car goes low 1.20's and I've never felt tire shake. Could it be a trans or converter problem? I'd rule that out first, then go to the ladder bar setup. I have felt a sort of "multiple launch" wherein the car loaded and unloaded the slicks (chassis) repeatedly upon launch. I suppose it felt a little like tire shake, just farther apart than the rattle of tires. I cured that problem with a little more pinion angle down. BTW, my car is 2700 lbs., N/A BBF, Glide, ladder bar, 9 in., 32 X 16 slicks. Hope I've helped. Good luck.
 

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Discussion Starter #3
no its tire shake i was on the starting line and it looks just like a bad prostock pass. it will pic the tires , then the side walls just start violenty shaking and
the whole car starts shuddering. he did get some digital video so we are going to watch it very close when he gets back from vacation.
we tried raising the wheelie bars but it would hit them so hard the tires would unload.
 

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Sounds like you already have plenty of pinion angle. Watch your videos carefully, and look to see if the rear end of the car squats on launch. If not, you might soften the shocks a little and let them take some of the hit. You can also soften the smack to the tires if you adjust the ladder bars to bring the pinion angle up a couple of degrees. It should let the tires spin just a little bit. Be careful here, though as a little adjustment goes a long way. Just take small steps, make one change at a time, and you'll do great. And don't forget, you can induce a little bit of wheelspin with tire pressure. At 2900 lbs., it's easy to run 'em too soft. I know that 6 3/4 lbs. of air is too soft for my 2700 pounder.
 

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For you car you are putting too much power to the tires too fast. Try going to the lowest power on the NOS. You do need to get the car up on the tire as soon as you can. Spin the tires a little. Think about a smaller tire, Set the plate up with about 100HP and the fogger at about 125-150 and use them as a duel stage system. Leave on the motor then at about 1.5sec into the run hit the first stage then at about 5-6 sec into the bring in the second system. Just some something to think about.
 

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Discussion Starter #6
we were just talking on phone tonight about stepping the systems. last week we ran with just the plate kit with a 175 and only saw a hint of shake once. 60 was still a little soft with a 1.34. the converter is way to tight on just motor but with plate is a little better. we got a 8.88 at 154 on the plate so i think next week we will jet down plate to 100 out of hole then bring in the fogger on gear change with 200. were hoping to do some 1/8 mile hits on plate and just work on suspenion 1 thing at a time, before out next headsup race.
thanks for the help
walter grosse.
 

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long

More info would help.

What is the drive shaft U-joint opperating angles at both ends (slip yoke & pinion)?

Single or double adjustable coil overs? Double adjustable coil overs (both extension & compression valving) are a helpfull tool to adjust more violent combos like ladder bar suspensions, and also can help cars with wheelie bars that unload & shake/spin.
If it's shaking because the inital ladder bar "hit" is too hard/violent, you can tighten/stiffen the "extension" (re-bound) valving. If it's shaking because the wheelie bars are un-loading the slicks because it's getting on the w/bars too fast & hitting them too hard, you can soften/loosen the "compression" (bump) valving. This will allow the suspension/wheelie bars re-compress easier while the front end is in the air & help stop the wheelie bars from "stiff arming" the suspension & lifting the slicks.

If the slicks are a soft sidewall, put in more air than the 6-7lbs that you have been using. You can keep adding air pressure untill they go from shaking to a flat-out spin, then back up the air a little. Also a stiffer sidewall and/or taller slick might help stop the shake without removing-reducing nitrous power.
 

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That's what I like........Tuning the car to use all the power it can make...rather than taking away power to get it 100' out of the hole. But then, I'm an old fart.
 

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Discussion Starter #9
wow thanks for the great info, i just was reading some suspension info on the net that is in the same thinking that you have pointed out.
if i remember we did loosen extension earlier in the year with our old combo on a crapy track to help with plant. with our violent hit now we could be hitting way to hard on intital hit and causing the shaking.
again thanks for the help ! walter grosse
 

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You know, I've seen it proved many times that all the power in the world with a lousy chassis setup will make you look like an idiot. A good chassis tune with so-so power can make you look like a genius.
 
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