From Post #17:
From Post #12:
From Post #8:

w0z26,

Thank you for your offer to contribute your time and extensive experience to the forum. That's what we're all about here, and learning from one another helps all of us take better care of our Jags.

I was trying to think through your arguments about the Hunter Road Force system by visualizing the size of the wheel you state as a minimum.

In one post you state the wheel must have a 1.8m circumference and in another 1.8m diameter. Obviously, it can't be both. The former wheel is much smaller than the latter by a factor of pi. Which size do you mean?

Also, when you stipulate a contact patch the area of one's palm, do you mean the palm only, as in roughly 3 inches by 4 inches (12 square inches), or do you include the fingers, which would approximately double that?

Wouldn't we need some additional parameters, such as the pressure at which the "Road Force" wheel is applied to the tire? Given enough pressure and sufficient tire sidewall height, one could create a contact patch of up to half the circumference of the RF wheel times its width, the area of which would far exceed your stated objective of the area of one's palm. Of course, that wouldn't simulate most driving conditions, not even traversing speed bumps/humps.

For a Jaguar saloon, it would make sense to assume a typical vehicle weight on the axle of perhaps 1,000 pounds / 454.5 kg. More on a front axle, less on a rear axle, but 4,000 pounds / 4 axles is an average of 1,000 pounds per axle. Divided by 12 square inches of palm-sized contact patch, that's 83.33 pouds per square inch. Divided by 24 square inches of palm-plus-fingers, that's 41.66 psi. Determining the necessary pressure for a "Road Force" wheel of any diameter would simply require the appropriate math.

I can accept the concept that a smaller RF wheel must distort the tread of the tire more than a larger RF wheel in order to create a contact patch of any given area accepted as "typical." What I do not yet know is, ultimately, how much does this matter? If RF is a gimmick, it's one that has worked for me in the past.

Science is wonderful, but applied carelessly it's meaningless. In addition to wheel diameter, what other criteria or parameters do your calculations assume?

Cheers,

Don

 

Another positive vote here for Hunter road force balancing. A few years ago I purchased a second set of wheels with snow tires mounted from Tire Rack. Not really knowing what it involved, I got the road force balancing so when the wheels/tires arrived, they needed only to be put on the car. It may be hard to prove that the road force balancing was the reason, but for the three winters I used those wheels/tires, the ride was very smooth, and perhaps smoother than the all season tires, but that could have been from 19 inch wheels with all season tires to 18 inch wheels on the winter tires.

 

So when you guys drive on the road you inflate your tyres to the point that you have a 10 mm strip in contact across the tread of the tyre? it wont give a true simulation, In fact the main reason its only 10-15 mm is because to recreate the size of your palm would put so much resistance on the shaft that will then will grossly effect the sensors on the shaft and then of course your readings.
Using lasers that bounce of the tyre and rim is my way of achieving the best result, it just makes sense.
The rotation of the tyre is to save weight as it moves the heavy part of the tyre to match it with the lightest part of the rim, but can only do this on the static part of the procedure of balancing not the dynamic as you can't turn the tyre so much now, as the tyre's are mostly asymmetrical.
The rims rarely go out of shape unless accident damaged, granted you get flat spots on the inner part of the rim, but tyres aren't made with extra lumps to compensate for this, the moving of an out of shape tyre around the rim isn't going to remove the vibration as the out of shape tyre is still there.
If the rim is bouncing up and down then the incorrect cone is fitted, using the cone on the inner part of the wheel and a finger plate is the best way to balance wheels, unfortunately most balance with the cone on the outside of the rim.
The main reason your'e getting this right is because you have spent the money of the proper adaptor kit and using it properly, which I wish a lot more people would do.
The chalk idea is good, but it really would depend on how many pints you had the previous night.

 

I'm thinking sometimes is best to agree to disagree, if we all thought the same we would all have the same machines.

 

It is NOT to simulate road surface force but a name. It mearly measures the roundness of the tire rim combo slightly loaded. And yes we cone the inside and use the "finger" lug adapter which is about the true only way because cones can lead to slight slippage. Especially when the load rollers are used for measuring roundness. on car balancers have been found to not only be as good as current technology but very dangerous as the master tech next to me that ive worked with for 18 years. He's been here 40 years and lost his eye sight in his right eye 25 yrs ago from a on car balancer when a wheel weight came off at speed. The main point to derive from here IMO is that there may be differing ideas about what is the BEST or BETTER road force/roundness measuring device. But either one is FAR better than just a plain Jane balancer. And EVERY TIME I have a complaint about vibration I ALWAYS recommend starting(and usually finished at this point) Roundness/roadforce balancing. Vibration issues are not 9 out of 10 times tires/wheels but 99 times out of a 100. one las tpoint Ill make on this issue is this. Before I worked at the dealer level and modded vehicles I never thought there was much differance in quality between wheels the OEM manufacturers use and good/expensive after market wheels. There is a BIG differance. OEM wheels by far are rounder, lighter, and take less weight to balance than a vast majority of after market wheels out there. And I have done a ton of them all.

 

The on car balancers, meant to be the answer to every vibration issue from prop shafts issues hub issues etc, well thats how they sold them. How did he lose eye, wow hope he got compo.

 

A weight flew off at speed and not one he put on. And no he didnt sue, not his style.

 

(Warning - long-winded post)

Just for preliminary information, my car has 235/50/18 Falken tires with approximately 85% of tread remaining. It has American Racing wheels (like this: American Racing - Wheels) on it.

To carry on from my original post, I had a nine o'clock appointment on Saturday (yesterday) at my local Goodyear dealer to do road force balancing on all four tires. When I arrived at the counter, the lady waited on me, found my appointment, and began to process my order. I asked to be allowed in the shop to watch the balancing and to see the car without the tires on it, especially the rear axle. (I wanted to see the condition of the boots on the half-axles, bushes, brake pads, etc.) She said I could probably be escorted out to see the car, but she was pretty sure I wouldn't be allowed to watch the balancing itself.

The store manager came over and asked me why I was willing to pay the additional cost to get road force balancing. After I explained my earlier adventures with trying unsuccessfully to balance them, the previous owner running after-market wheels without hub adaptor rings, etc., he suggested we go out and take a look. He asked if we could take a test drive (which surprised me). I happily agreed and away we went with him driving. During the drive, I learned that he had been working in the shop at the local Jaguar dealer during the first few years of the X350 and so was familiar with them. We took a much longer test drive than I ever imagined - on local neighborhood streets, smooth four lanes, rough pavement, and at every legal speed limit from 20 mph to 70.

He concluded that the vibration that we were feeling was tire/wheel related, but that there were strange things going on. For example, the right rear was consistently the worst and most obvious offender. But at any given speed, slow down or speed up and then return to that same speed on the same pavement, the vibration seemed to move and/or get stronger or weaker. He said that he would not be surprised to find water in the tires - not much, but just enough to affect the balancing. He explained that he had seen cases wherein a person would air up a tire using an old compressor or one without a proper water filter and in the process spit very small amounts of moisture into the tire - not much, but enough to affect the balance. The tire would never be successfully balanced because of the water moving around in the tire.

When he returned, he said that since I was willing to pay the higher price for road force balancing, he would just have the tech pull it in the shop and "have at it, whatever it takes." He told me that for insurance reasons, the company would not allow me to stand in the shop and watch, but that he would keep me posted about anything they found and that when they were finished, he would escort me out to the see the car without the tires and show me what they had done.

For nearly two hours, they worked. The manager would come in to the waiting area and tell me how far off that right rear one was and what a fit it was giving them trying to get it right. He updated me several more times along the way. They broke down every tire to check for water inside and found none. When he took me out to the shop, the tires were finished and each one had been marked across the tread with chalk how much road force the tech had gotten the machine down to on that tire. The lowest was 10. The others were 11, 14, and 15.

The one that was 15 was from the right rear and was still on the machine. He said that, according to the machine, the tires were already in the best possible position on the car. He showed me the force measurement on the screen, then asked me to stand in a certain position and watch the tire. He told me where to look. As I watched, he spun the machine up just a tad so that I could see that the tire had a slight movement when I watched along the inner side wall. I did so, then he asked me to watch from a different angle. He spun the tire up again slightly. There were low spots when I watched from the side, across the tread. The tire was not perfectly round. He said that more than one of them had that same issue. I asked if that could be caused by belts inside the tire that had broken.

The manager said that he believes the belts are okay, but that the tires have permanent damage, like flat spots, from sitting too long at the dealer where I bought the car. (We had previously discussed that the dealer had the car for a long time and that it never moved, except to take pictures for the ad that I later bought the car from.) When I test drove the car before buying it, it had horrible flat spots on all four tires. They finally settled down after several miles of driving, but not completely. But, for the price I was paying for the car, I accepted that.

The manager gave me a discount on the balancing, I think because he just wasn't convinced that the tires were completely smoothed out. He asked me to call him after I had driven it for 20 or 30 miles at highway speeds and let him know how it did. The car is definitely improved, but there is still a noticeable vibration. It is basically the same feeling, sometimes in the steering wheel, sometimes in the body, but at a much lower intensity. More tolerable, but still there. At some speeds it almost goes away. At 74 mph, it smooths out like glass.

He told me that sometimes, after dismounting and remounting, moving on the rim, etc, tires such as mine will "settle" into their new positions and may improve slightly after being driven for a while. He said whether I buy from him or someone else, he thinks that I will eventually wind up having to replace the tires in order to solve the problem completely.

I asked if they had found any issues at all with the wheels. He said that all four wheels had run out as straight as they possibly could have, and that with the hub rings in place, it was his opinion that the entire issue was tire-related.

They used the Hunter GSP9700 machine. I believe these guys knew what they were doing and that they did everything they could. They even cleaned the hubs between the wheel studs and around the hubs, then the back side of the wheel where they mated with the hubs so that they would have as perfect a surface to bolt together as possible. He said they wanted to eliminate every possible issue that they could think of.

It looks like new tires are in my future. The good news is that everything looked good on the back axle except one bushe on the right side that still seemed tight but that had the rubber cover split. it will need replacement one day. The front brake pads are okay, but not the same quality as the back ones. Hence the brake dust that coats my front wheels, especially when it rains. When brake time comes for the front, I'm not sure the rotors will be thick enough to turn.

 

In the time since the balance was done, I've driven the car probably 60 to 70 miles and it does seem that at some speeds the vibration is decreasing. For example, at 50 to 55 it was barely noticeable last night. It had been fairly obvious at that speed just after leaving the tire shop. I drive about 40 miles per day round-trip to work and back. I'll see how it does over the course of this week.

 

Those are well within specs of 27 for a passenger tire. Obviously the lower the better but those numbers are good. You may want to "detune" your butt and hands alittle

 

I have wondered if I might be feeling something related to worn bushes, etc. Is that possible? What I feel is very similar to slight tire imbalance.

 

Yes you can as any slight in balance with be transmitted through worn bushings etc. As can leaking transmission and engine mounts. Then you can always try another set of tires wheel from another car. Earlier this year i kept telling a customer he had bad tires creating his roaring noise and vibration. But he had a ext warranty and didnt want to pay out of pocket expenses. The first visit i told him tires not bearing etc. He went to another shop and they said bearings... So i took a set of tires off another stype i just put on the day before and swapped to his car. Oh guess what no noise and no vibration. Made him his wife and my boss all go ride since no one wanted to believe me. (im from the show me state so you know how we can be) was asstonished how quiet it was. Okay now you owe me diag time. He wasnt happy about that. But he i told you the first time what you needed for free and you didnt want to do it or believe. Now i had to show and prove to you. I would just want to swap wheels and tires to to see, you either eliminate a suspect or you found the guilty and arrest em

 

Funny you should suggest trying other tires. I don't have access to another whole set, but just before I read your post I suggested to my Honey that I try the spare tire in place of that right rear tire. The spare is a good tire mounted on a genuine 8 spoke Jaguar wheel. Couldn't hurt to try it, I told her.

 

Do low road force numbers (less than 27) necessarily indicate perfectly balanced tires?

 

Off the subject a bit, but reading the post where the gentleman talks about the "size of ones palm", reminds me of a film I once saw in Germany back in the early 70's.


The film was about the use of winter tires and in particular, winter tires that used metal spikes to grip the ice.


They took a section of their test road and replaced it with a section of clear glass. Under the glass section, they placed a very high speed camera.

They then equipped a car with the spiked tires and drove it over the clear glass at varying speeds and recorded how many of the spikes were actual touching the road. I don't remember all the speeds, but at 30k, an area of about the size of the palm was covered with the spikes--say about 15 to 20 spikes. At 50k, there was only about half of that amount touching the glass. This was the shocker--to me at least, because I used the spiked tires---at 100k, only two spikes per tire-- in an area the size of the palm of ones hand, was touching the glass.


So basically the four tires were riding on 8 total spikes. I never drove over 50k with the winter tires again.


I guess my point is this. Unless one would have the same type of set up to view how much an area a tire is covering the highway, at any given speed,
that mental picture could control ones driving habits.


I think that film was put out by the German auto safety industry and possibly with a little digging by our German forum friends, maybe it can be found.

 

no not balance. ROUNDNESS. Like I said you can balance a brick