Front End Shake

Danr55 · #1 (**permalink**) 03-09-2015, 07:32 PM

I have a mystery shake in the front end between 63 and 80 MPH. If I get on it hard getting on the freeway, the shake is terrible. If I push through it, it will eventually become manageable but still noticeable. If I ease onto the freeway, it still shakes but not as bad. I've checked everything to make sure it's tight. The front end has been aligned and is exactly where I've been told it should be. The wheels are balanced within a gnats butt. The shocks are less than three years old. I've run out of places to look.. The steering ins tight to the point where it's almost difficult to turn. Any suggestions?

vatdevil · #2 (**permalink**) 03-09-2015, 07:34 PM

Tires out of round or flat spotted?

joyridin' · #3 (**permalink**) 03-10-2015, 04:49 AM

It sounds like something with the tires, especially in that speed range.

Detroit Bill · #4 (**permalink**) 03-10-2015, 06:26 AM

I would locate someone with a Hunter Road Force wheel balance. It detects out of round or flat spots with the tires. Also no rim is perfectly round and no tire is perfectly round. If you happen to match the high spot of the tire and the high spot of the rim you get a shimmy. This detects the high spots on both and guides you to offset them. In the past you could only experiment to mitigate the high spots. It can be perfectly in balance and out of round.

Hunter GSP9700 Wheel vibration Control System solves wheel vibration and tire pull problems that balancers and aligners can't fix

After that I might look at the ball joints. I think Hi-tech makes that chassis, if so the Superformance chassis have been known to have stiff ball joints which can cause what you are describing. The "difficult to turn" comment also makes me think ball joints. Cobra Valley sells upgraded ball joints you could call them and see if they are the same. I'll bet they would know.

Good luck and report back.

Dwight · #5 (**permalink**) 03-10-2015, 06:37 AM

Check your pinion angle. Rear chunk 4 degrees down and 1 1/2 to 3 degree differents in driveshaft and chunk centerline.

Dwight

lnfletcher · #6 (**permalink**) 03-10-2015, 06:51 AM

I agree with D Bill.
I had this same problem and struggled with it for years. Mine was so bad the wheel would shimmy approximately 1/2 to 3/4 inch back and forth violently. Replaced bearings, ball joints, tighted everything way over what it should have been. I even adjusted toe in, and caster with little improvements. Each place I went to said they aligned and balanced the tires perfectly. I even swapped the tires from another car that I have with the same size tire without change. I even looked up a shop with a Hunter Road Force machine and told him that I thought it was the wheel because I had swapped the tires without success. After he tested my wheels and tires, he told me it wasn't the wheels and that I needed new tires as they were out of date, so I bought 2 new tires. No change!
I happened to be at a local Firestone dealer getting a trailer tire put on and mentioned it to the Manager and he said he would really spend some time on it. I brought my car in and left it with him for the day and he found one of the wheels runout out of specs. He worked the tire around on the wheel and minimized the effect. It is 95% better which I assume can't be fully fixed without another wheel. It's not bad enough now for me to spend the money on a wheel.
It just took the right person with the time to do it right! (He also had a Hunter Road Force machine)

Detroit Bill · #7 (**permalink**) 03-10-2015, 06:59 AM

So someone with a road force balancer was not able to detect and fix the problem?

Detroit Bill · #8 (**permalink**) 03-10-2015, 07:49 AM

I am sorry I miss read what car you have. Hi-Tech did not build the chassis. Ignore that theory.

okiedokie · #9 (**permalink**) 03-10-2015, 07:55 AM

I had the same problem with my car. It originally had Cooper's on it and then I changed to Mickey Thompson's SR's , tried 2 different sets , and still had the shake. Chased this problem for 2 years and can't count the number of times it was in a shop for balancing , including Road Force, moving tire around on rim, checking pinion angle, wheel alignments , having rims checked and straightened ( which were New and without defect ),having the car checked and worked on by " suspension experts " , some made it a bit better but overall, could not correct the problem.
Until a buddy let me borrow his 4 Hoosier's to try out . Guess what , no shake, and I took it up to 120mph just to be sure.
I know this is upsetting to many in this community but I went out and bought a set of B.F.Goodrich Radial T/A's and haven't had even a hint of tire/wheel shake since they were put on.
Good Luck.

streetrod1927 · #10 (**permalink**) 03-10-2015, 08:19 AM

Dana; Take a look at the tie rod ends on either side. They could be worn. I had a similar problem with mine. Once repaired a good front and rear alignment... problem solved.

cycleguy55 · #11 (**permalink**) 03-10-2015, 08:46 AM

Detroit Bill may be on to something with the ball joint issue - that would certainly be consistent with the stiff steering. Once you've ruled that out I'd take a look at the drive train.

I know you described it as a front end shake, but as these are simple, short wheelbase cars with no sub-frame isolation, even something in the drive train can feel like it's happening elsewhere. As it sounds like the intensity varies with power levels, I'd start with the slip yoke from the transmission, all the way back. It could be a problem with a yoke, u-joint, drive shaft or pinion angle (as noted by Dwight).

Danr55 · #12 (**permalink**) 03-10-2015, 10:33 AM

Thanks Guys. Sounds like I have some work to do.. I'll check out these things and get back with you.

bobcowan · #13 (**permalink**) 03-10-2015, 11:23 AM

Quote:

Originally Posted by cycleguy55

As it sounds like the intensity varies with power levels, I'd start with the slip yoke from the transmission, all the way back. It could be a problem with a yoke, u-joint, drive shaft or pinion angle (as noted by Dwight).

Get the car up to 80, and then put it in neutral. let it coast down through the range that you normally feel the vibration.

If it's speed sensitive, it's probably suspension.

If it only occurs under power, it's probably drive line.

Young1 · #14 (**permalink**) 03-10-2015, 05:14 PM

Mine started shaking at 70. Bad at 90. Front Firestone Indys visibly out of round. Went to BFG and my local tire guy, not a chain, bought 5 tires till he was satisfied my front was good to go. Soooooo I could have had bad tires replaced with bad tires if not for the owners integrity. He is an ex stock car champion. I gave the Firestones to an employee and he said they were fine on his mini van. Maybe these lightweight cars are more sensitive to tires?

Jerry Clayton · #15 (**permalink**) 03-11-2015, 06:40 PM

stiff steering could come from too much caster (makes the front tracking VERY STABLE) if from tracking is very stable from too much caster----------then the whole car skakes if ANYTHING is out of wack----------

and as for driveshaft angles----In a cobra with a very short drive shaft, it could be a sideways angle , not just a vertical angle---------

Danr55 · #16 (**permalink**) 04-06-2015, 11:30 AM

The final solution.. : I checked the thrust angle and reset both sides so they were closer to where they should be ( I have installed Watts Links from Mickmate to hold the rear end stiffer than before). I then made certain that both rear wheels on the Vintage Wheels adapters were running true and round within about .010 inches. With all of that done, there is no perceptable shake in the front end under any circumstances. It appears that the problem is solved.