A bit less scientific than I expected but the video shows the 'ding' was removed successfully and the repair looks substantial.

Thanks,
Graham

 

Bear in mind not all OR (out of round) wheels will show evidence of damage - curb shots, potholes, etc. So many wheels these days are highly offset and can have very long spokes. The center section can stretch/deform more easily than older styles and size rims. It doesn't take much of a shot to cause issues. You can spin-balance an egg but you can't make it roll smoothly against a flat surface.

 

The steering wheel still shakes at around 65-70MPH+ even after doing the following in hopes of fixing this annoying issue (most items needed to be done anyway):
Replaced front upper control arm bushings (both sides)
Replaced sway bar bushings.
Installed new Brembo rotors and pads on the front.
Had it aligned at two different locations, both agreed that alignment was not too far out of spec and had minor tweaking (I didn't tell them I just had it aligned about 100 miles ago).
Both alignment shops said the ball joints, side to side wheel test all appear ok.
Had tires balanced and rotated (twice-two different shops).
Swapped another set of wheels onto the car, no improvement.
I just installed two new front tires and still not improved. I am no better off than I was when I started.
Car runs ok through about 65mph on the highway, turning right or left makes no difference.
While the shaking is constant at 65mph+, it does seems to shake in a rhythm and gets worse, lightens up, gets worse, lightens up. This is a consistent pattern of shaking. It never just goes away and comes back. Same amount of shaking when cold or warm.
Any further tips? What else could it possibly be?? Car is a 98 XK8, 156k miles, no modifications.

 

If you haven't tried Road Force Balancing, you should give it a try. Only the top-notch tire shops have road force balancing equipment, but these cars are incredibly sensitive to this kind of thing, and the procedure solved a shake in my 1997 coupe.

Road Force Wheel Balancing can accomplish two things that may help...first, it checks the balance of the wheel / tire combination while under load, which sometimes finds imbalance where a traditional balancing machine does not.

Second, it allows for match balancing, which helped get rid of a vibration I had at 70 mph. All tires and wheels have slight "high spots" and "low spots," both in roundness and in weight distribution around the circle. Match balancing finds the "low" spot of the wheel and the "high" point of the tire, so these two points can be aligned to cancel each other out (somewhat).

Ever notice that little dot of paint near the rim of a new tire? That's the "high" spot, as detected by a machine at the tire factory.

The right tire shop with Road Force Balancing equipment just might help. Good luck.

 

Many times vibrations that increase/decrease are the result of two or more rotating masses coming into and going out of synch. (one tire is a bit taller than the other or slight turning causing one wheel to travel further, etc.)

I know that Ford and GM techs are trained to solve vibration problems, however finding one that is willing to put in the time it takes will be difficult as most customers don't want to step up and pay for 'however long it takes', especially at $100/hr.

I'll post some things that may or may not help you:

http://www.tirerack.com/images/tires/vibechart.pdf Layman's diag chart

Vibrate Software This is what the big boys use, along with a vibration/frequency/amplitude detector.

While at Vibratesoftware.com click on 'Tools Needed'. Probably the most 'popular' (in the wildest sense of the term) tool is the EVA as it's a required tool by most OEM's for their dealers. Around two large for a new box, you can find them for rent online (about $100/30 days) or pick up a used one on eBay for a couple hundred (then turn around and resell it when you're done with it.)

Also while you're at vibratesoftware.com click on the 'Diagnostics' tab to get an idea of what all of this is good for. I've had online NVH training at FLM, GM, SAAB and Isuzu and a three day class in Cleveland, OH at a Ford training center. Once we had a bit of experience I was able to find a 1/4oz weight the instructor had attached to the backside of a pulley in about 15 minutes.

Then, there's always the application of a bandaid with a shotgun method:

Tire Balancing Products
or
ESCO Liquid Tire Balance — One Case of Twelve 32oz. Bottles, Model# 20471 | Tire Equipment | Northern Tool + Equipment
or
any of several dozen of the same premise, whether it's liquid, beads, ***** in a raceway that bolts between the wheel and hub, etc. Nothing like smooth driving at 80+ then going around a tight curve and having all that crap run up the sidewall of the tire and instant vibration returning...

The red and/or yellow dots on tires can mean different things, depending on the tire manufacturer. It used to be some wheels were made with a .015" offset with the valve stem hole being the 'marker'. The dots on the tires represented the point of concentricity and the high weight point of the tire. Aligning whichever spot with the valve stem was to be 'more better' (nobody really gave us a clue as to which was supposed to be used, I think it was a 'try this first, then try the other if you have a problem.)

 

Have you checked the wheel bearings and steering rack for wear? Harmonic balancing will only be a temporary solution to this type of NVH problem.

NBCat

 

Thanks for all of the information.

I found a specialty tire shop that actually has two new Hunter RoadForce balancers in their shop. I will take it to them to have the wheels and tires balanced tomorrow and will report back.
If that does not cure the steering wheel shake, I'm going to look into replacing the front bearings and lower ball joints, that's about the only two things I have not yet replaced with new parts yet.

 

Sometimes you just never know what is causing such a problem.

Way back when I had my 340 Duster in around 1976 I had put on some new tires and for some reason, I had a strange vibration coming from the right front at highway speeds. I took it in and got the wheels re-balanced at least three times. I replaced bushings and bearings and all sort of stuff in the front end, and no matter what I did, it still had that vibration.

One day when I was heading back to college on a long road without much traffic, I leaned way forward in the seat and toward the middle of the car to see if I could figure out exactly where it was coming from.

This car had one of those solid stainless antennas that was mounted just at the base of where the passenger side front pillar came down. I looked over and saw that it was spinning around in an elliptical manner, instead of bending back, which I could not see when I was seated in the car normally. I pulled over and unscrewed the antenna with my pliers, got back in the car, and BOY, was it ever riding smoothly now! I flexed the antenna around a bit and put it back on and now it laid back instead of spinning around. Problem fixed.

I just bring this up because vibrations sometimes come from some very unexpected places.

 

UPDATE: I found a shop with the Hunter Road Force balancing machine. I had all 4 wheels/tires balanced. They said that some of the wheels were out of balance but that the runout was ok. They stripped all existing wheel weights and rebalanced them with the Road Force balancer. It was cheaper than I thought, they only charged $12.50/tire or $50/all 4. Once complete, I went for my road test, while the shake is still there around 70mph+, it is vastly improved. The shake comes on about 65mph (used to be around 55mph) and it is not as bad, and much more bearable. I would say it is about 50-60% improved from what it was. The $50 was well worth it.

Now that the balancing is done, the shaking has some different characteristics that I can feel now, mainly when I am at 65-70mph with accelerator down at a steady speed, the shaking gets a little worse when I let off the gas, but minimizes when I get back on the gas. Ball joints maybe? Note that I have all new brake pads and rotors.

In order to attack the remaining 40-50% of the shaking, I think I am down to either the wheel bearings or lower ball joints. The driver side lower ball joint has a little bit of play along with the rubber being torn. I just have to find a place to source the ball joint as a few places I called mention it is a non-serviceable part, but I figure it can be serviced with the right part.

I am on the right track. Thanks for everyone's suggestions as I attack this issue.

 

I've posted re: road force balancing in the past. To do it right takes either a lot more time than $12.50/tire allows or the person doing the job is incredibly lucky. I'm guessing the place that did your balancing is just making sure nothing horrible is wrong with your tires and wheels or they have no idea how to use their machine. I'm not trying to sound like a know-it-all but to properly use those machines takes more than a couple minutes for each tire. You can use them as a run of the mill balancer but what would the point be? Typically road force balancing four tires will cost $100 or more.

Also to consider is the fact that Hunter and tire shops both are fairly lenient in regard to how much road force is acceptable. When I worked at Lincoln tire sizes that fit Navigators were supposed to be o.k. @ around 35-40lbs. of road force but we found that our customers weren't satisfied until we set our specification to 15lbs or less. And that's on a huge tank of a Navigator! Can you see how 25-30lbs of road force would affect your car?

So maybe the peeps that balanced your tires couldn't care less about profitability and did actually want to do their job correctly. Maybe they are using the lenient recommended specs. The odds that you have four tire/wheel combinations that displayed less than 20lbs road force when first mounted are astronomically against you. I've road force balanced tons of tires, especially when I worked here: www.bluegrassauto.com , and I can't recall ever having an entire set of tires come out perfect without having to spin at least a couple on the rim. If I were you I'd probably go back to the shop and tell them that it's better but not quite right just yet. Then ask them how much road force they consider acceptable for your car. Showing that you have a little idea of what's going on might get them to step up to the plate and do a better job.

Then again, they may have done a fantastic job and it's something else. I'm just tripping over RF balancing @ $12.50/wheel - that's about average for a 30 second 'spin n' slap' around here.

 

I spoke with the tire shop this morning and they gladly offered to perform a roadforce balance to stricter specifications at no additional cost. This time I will watch the person doing the balancing.
Do you have a recommendation for the amount of road force that would be best/acceptable for a stock XK8 wheel and tire? As I understand from your other posts a lower measured pounds is the goal. Maybe when I get it done this time the shake will be gone. I will be going back on Saturday.

 

Personally, I wouldn't want anything over 20lbs on any of my own tires. I'd be shooting for 15lbs or less, especially with low profile tires that don't have any sidewall to flex and absorb/dissipate the transmission of motion. However, if they didn't sell you the tires, you may have to settle for the 20lb figure.

If you get to watch there will be a lot of numbers. The numerically larger numbers will be the weight required. What you really want to look at is the total roadforce. If it exceeds the 20lb parameter the rim should be measured. To do this the tire will be rotated by the machine while the operator holds the arm against the rim. Once that has finished there will be a number for the rim offset and another for the tire offset (interchanging 'offset', 'roadforce', 'deflection', etc. as all being the same thing here.) The closer these two numbers are numerically the better. Rotating the tire on the rim so those numbers offset each other is what you're trying to accomplish. If they are vastly different it's better for the operator to mark the tire and wheel, with the numbers, and set it off to the side. Then continue with the other wheels - there may be another tire/wheel combo that better matches those offsetting numbers. If that's the case the tires should be swapped between those two rims and the marks aligned - are you catching on now?

 

Personally, I wouldn't want anything over 20lbs on any of my own tires. I'd be shooting for 15lbs or less, especially with low profile tires that don't have any sidewall to flex and absorb/dissipate the transmission of motion. However, if they didn't sell you the tires, you may have to settle for the 20lb figure.

If you get to watch there will be a lot of numbers. The numerically larger numbers will be the weight required. What you really want to look at is the total roadforce. If it exceeds the 20lb parameter the rim should be measured. To do this the tire will be rotated by the machine while the operator holds the arm against the rim. Once that has finished there will be a number for the rim offset and another for the tire offset (interchanging 'offset', 'roadforce', 'deflection', etc. as all being the same thing here.) The closer these two numbers are numerically the better. Rotating the tire on the rim so those numbers offset each other is what you're trying to accomplish. If they are vastly different it's better for the operator to mark the tire and wheel, with the numbers, and set it off to the side. Then continue with the other wheels - there may be another tire/wheel combo that better matches those offsetting numbers. If that's the case the tires should be swapped between those two rims and the marks aligned - are you catching on now?

 

Perhaps you need to look further afield as you still have a problem. Check the propshaft rubber doughnut and that the bolts are tight. Check the front subframe mounts to the body with the body supported and subframe hanging. Check the rear axle especially the inner fulcrum bushes but also the mounting bushes. You can check the fulcrum by supporting the body and then trying to push and pull the wheel towards the front & back of the car. Admittedly this tends to knock but may upset the way the car is tracking.

I've 18" Goodyear Eagle GSD3 tyres and the car has been left for a month before now with no problem of flat spots. Same on my x300.

Regards
John

 

A step beyond roadforce balancing is to have the front wheels trued. Piedmont Wheel Repair in Moorseville NC does an excellent job at a very reasonable price. 704-664-9771

 

Upper bushings, ball joints, and fulcrum pin didnt cure it for me (did stop "Clunking"). I next replaced lower bushings, lower ball joints and shock bushings and it dissapeared.

 

I have this clunking/ shake too. What did the parts cost? I will have to order them and have them sent to me in Mex...

Meanwhile the local Continental tyre balance guy said the rims were dented, so I am going to see the wheel techs tomorrow. Might be interesting!

 

ding ding ding!! Winner

 

I had the same issue at about the same speed. I had my small ding in the wheel fixed and it took care of the problem.