I have two 1980 Triumph TR8’s. One of them develops a slight front wheel shimmy at around 100 kph (60 mph) which is very noticeable on the steering wheel. Its not too bad but is still annoyingly noticeable. I’ve thought of everything including all these things and it all seemed to check out fine.
Wheels bearings
Alignment
Tire Pressure
Ball joints
Tie rods
Front bushings
Steering rack
Steering shaft u-joints
Steering shaft firewall bushing
Tire issues
Rim bent / warped
I’ve had the wheels balanced but only statically. Should I try dynamic balance? Is it that much superior to static balancing.
Am I missing anything? I realize its a 33 yr old classic car but is in great shape and mechanically A-1. I just can’t figure out this shimmy thing. The other car is 100% perfect.
I have two 1980 Triumph TR8’s. One of them develops a slight front wheel shimmy at around 100 kph (60 mph) which is very noticeable on the steering wheel. Its not too bad but is still annoyingly noticeable. I’ve thought of everything including all these things and it all seemed to check out fine.
Wheels bearings – you’d feel “loose”
Alignment – can cause uneven tire wear, and wonky handling, but shouldn’t cause shimmy unless extremely off.
Tire Pressure – unlikely, unless obviously way off
Ball joints *-- you’d feel “loose”*Tie rods *-- you’d feel “loose”*Front bushings *-- you’d feel “loose”*Steering rack *-- you’d feel “loose”*Steering shaft u-joints *-- you’d feel “loose”*Steering shaft firewall bushing *-- you’d feel “loose”*Tire issues – likely culprit. Try rotating them front to back and see if that helps.
Rim bent / warped – extremely likely culprit if tires recently balanced. Front/back rotation would check this also.
I’ve had the wheels balanced but only statically. Should I try dynamic balance? Is it that much superior to static balancing.
Dynamic balancing is really only beneficial for very high speed/high performance tires, or if there is some defect in the tire (e.g. a bulge that manifests while spinning). But if you do have a defective tire, dynamic balancing is not the solution.
Am I missing anything? I realize its a 33 yr old classic car but is in great shape and mechanically A-1. I just can’t figure out this shimmy thing. The other car is 100% perfect.
What kind of shape is the rubber itself in? Worn treads can (and often do) introduce unwanted feedback.
man i follow these things on tech threads religiously
My first guess would be the balance of the wheels themselves–and are they cast or wired? Some swear by dynabeads but i prefer to have my wheels balanced the old fashioned way with weights.
If not wheel/tire problems then you know you have to start looking at the front end with all that that British Leland engenders.
GL, post pics and let us know out it turns out?
v/r
If I’m wrong then ignore the rest, but the TR8 was a V-8 rear wheel drive car, correct?
I had a “built” 79 Z-28 that would do that at about 65 mph and then again at 130 mph. At the time no one wanted to help me because I was 22 and the “grown ups” didn’t think I should be going that fast anyway. I did everything I could think of with the tires, wheels, suspension, and steering system. Nothing. Turns out that the drive shaft was out of balance.
I had put bigger U-Joints in the car to hold the torque of coming off the line in second gear and during the modifications to the drive shaft to accept the jionts I had knocked a balance weight off the shaft at the front joint. Got the shaft balanced and … problem gone.
Damn I wish I still had that car!
I’m beginning the think that it could be a fault in one of the wheels. They’re 6 x 13 Shelby’s that were originally on a Sunbeam Tiger. A lot of owners are now going to the 15" wheels since its getting very hard to find 205/60/13 tires in this day and age, so that’s something I’ll have to look at. The V8 engine is jacked up with cam, headers, higher CR pistons and Quick Fuel 4 bbl carb replacing the Holley I had on it. My wife’s TR8 is prepared similar but has 7 x 13 Panasports and her car rides perfectly. I guess the next step is to just swap wheels with the wife’s car and see if the problem goes away and then I’ll know its a wheel problem. Duh, I just thought of that now.
You have two… swap the tires and see if the problem moves. If so swap one back at a time.
I’m betting a tire, I went crazy trying to trouble shoot a niggle and ended up getting a two new tires, problem gone. Went through, balanceing, bearing replacement, and alignments. damn tires looked to be in good shape too.
If it has disc brakes, check the rotor for runout (out of true for us bike nerds).
Checked the brakes already. They seem good.
I looked at everything but maybe not closely enough at the obvious - wheels/tires.
Maybe see if one of the tire shops local to you does road force testing.
I had a Lexus RX330 with a pretty bad speed wobble at about 60 or 65 MPH. Had it dynamically balanced and it went away. That’s my N+1
I’ve had the wheels balanced but only statically. Should I try dynamic balance? Is it that much superior to static balancing.
Absolutely. I can think of many configurations of masses that would balance when static but be horribly out of balance when rotating…
What tire shop doesn’t dynamically balance these days anyway? I can’t remember the last time I saw a static balance tire rig.
I’ve had the wheels balanced but only statically. Should I try dynamic balance? Is it that much superior to static balancing.
Absolutely. I can think of many configurations of masses that would balance when static but be horribly out of balance when rotating…
What tire shop doesn’t dynamically balance these days anyway? I can’t remember the last time I saw a static balance tire rig.
I think they’re confusing a dynamic balance with a road force test, the last time we used our static balancer was in 1997 and that was by a tech that was to cheap to pay for a dynamic balance from the tireshop down the street as we weren’t doing tires anymore.
“What tire shop doesn’t dynamically balance these days anyway?”
I do most of the work on my classic cars myself, but there is a small one man shop locally who is very good with older cars who I think is a great mechanic, but he doesn’t have a dynamic balance machine. I’m in a village of pop 1800 so I’ll have to take the car to the “big city” pop 110,000 about half an hour away. 
Out of balance tires usually become apparent at right around 55-60mph. So, that is consistent with what you are experiencing. The benefit of a dynamic balance is that it balances the tire and wheel in two rotational planes instead of one. As the wheel is turning, the inside of the tire/wheel combination and the outside of the tire/wheel may not have exactly the same mass. At speed, these heavier and lighter portions of the tire/wheel can cause the steering wheel to shimmy back and forth.
Second more remote possibility: Has the car been parked for a long time? Do the tires have nylon belts? The belt type should be on the sidewall. If they have nylon belts and the car has been sitting for a while, you might have flat spotted tires. If that’s the case, they should smooth out after 400-500 miles, at the most. However, flat spotted tires usually reveal themselves at pretty low speeds and you would sense it on all four tires. This doesn’t usually cause the steering wheel to shimmy, per se, but it will kind of vibrate some.
I wouldn’t suspect a U-Joint since they usually create a much higher frequency than rotating wheels because the driveshaft is turning much faster than the wheels. Also, they usually do not vibrate when you let off of the gas. If it’s a driveshaft weight that has been knocked off, the vibration is pretty unique and most mechanics will identify it right away. I would suggest checking the half shafts, but I think that car has a solid rear axle and it sounds like you are sure the shimmy is definitely in the front end.
You could jack each front wheel off of the ground and spin them to see if you can spot any high spots on the tires, irregularities in the sidewalls as a result of potholes, warped or bent wheels, etc. It would be easy to make yourself a simple device to position against the rims, sidewalls, and treads while spinning the wheels to check for abnormal runout.
I am betting it’s a tire issue of some sort. Probably hit a pothole and damaged the sidewall. Look for bulging areas on the inside and outside of both front tires.
FWIW,
Greg
Under normal circumstances wouldnt the sensation of a driveline vibration present itself in the seat? IIRC vibrations that are felt in the steering wheel are steering / front suspension / tire & wheel related.
Thanks guys. Love the LR. It amazes me that I get better responses here on car stuff than on the car forums.
Under normal circumstances wouldnt the sensation of a driveline vibration present itself in the seat? IIRC vibrations that are felt in the steering wheel are steering / front suspension / tire & wheel related.
Yea, but sometimes people focus on the steering wheel even though it is the entire car that is vibrating. When the driveshaft is out of balance, the vibration travels into the differential and then to the rear suspension into the chassis mostly. It also travels through the transmission, engine and motor mounts into the chassis.
I believe the same thing as you do about cervelo’s problem. It’s almost surely a tire/wheel problem.
Greg