Cut a long story short, got new tires and had the wheels balanced. Steering wheel wobbled at 55 - 70 mph. Had the wheels RoadForced ($79 lifetime - life of the tires that is), this moved the wobble to 60-75. In addition the Tech said that nothing in the front end is worn.

Took it back to a different store and Re-RoadForced. This time it moved the wobble to 70-75 mph, but reduced the wheel shake by 75%. So, I'm taking it back in this weekend for a Re-ReRoadForce.

Are the Tire Techs simply balancing within a tolerance and figuring out that +5% (say) is good enough for most cars, whereas the Jags are more sensitive? Or is there a more stringent spec that they should balance to?

I did find out during my research that the Jag wheel are "lugcentric", which means that the wheel is located on the hub by the lug nuts and not the hub center itself. So when they balance the wheels, they have to use a lug adapter on the Hunter and not balance the wheel using the center holes (covered by the plastic Growler). Thirty plus years of cars and bikes and I'm still learning....

Cheers,
Hamish
2001 MY

 

I did not know that, but will ask my tire installer next time. I have a slight vibration at 70mph, but I was told I have a small ding in my wheel to that they believe is why it is shaking at that speed. The balance (roadforce also) was spot on like I requested. We'll see...I am fixing the right side in a couple weeks.

 

I went through a similar process of tire replacement, balancing, vibration, road force balancing, with similar results.

In the end, two wheels had to be sent out to be repaired because of slight bending, (trued and re-painted). A company in Indiana picks up the wheel from local tire dealers and repairs/returns it for about $175 each. This in the Milwaukee/Waukesha WI area.

Also, I installed General Exclaim UHP tires. They are EXCELLENT and showed NO out-of-round condition (Road Force Imbalance) on the Road Force Balancer.

Now have NO vibrations at any speed.

 

Hammish-- Went thru to same drill you did. Found out that the training of road force bal techs is critical to the outcome. Also, at some level of bal weight, my tech de-mounts the tire and spins it 180 Degrees on the wheel. That really cuts down on the total weight to bal and some how improves the end result.
Did not know about the lug centrict issue either. Wow! Am I glad my tire guys didn't charge me to re do this work. That explaines why my guys had such a hassel getting it right too. I looks like they just closed in on the problem by trial and error. Holy Cow. What a great thing to know!!!!!

 

For those of us with no time commitments or lives, here is the link to the Hunter demo videos:

http://www.gsp9700.com/pub/images/demo.cfm

The "Operation Technique" shows how the machine works and how the wheel should be balanced. In a nutshell, it's worth the few minutes to watch so that when you next go in for balancing, you have an idea of what they should be doing (and not doing).

The video references using different settings for "Car" and "Off-road" which leads me to think that there is some kind of "standard" applied; question is, how high does the standard need to be to get it right.......

Cheers,
Hamish
2001 MY

 

I had my front wheels spin-balanced on the car. Smooth as glass!!

 

I bought new tires for my 2001 two years ago. I've not experienced and issues with wobble or vibration. I bought the tires from Tire Rack, and they were shipped to my mechanic for mounting. I don't know what equipment he uses, but he's very careful with the rims.

 

Say Hamish,
I called 2 local Jag dealers and they are adament that XJ Jag wheels are "hub centric" and not "lug centric". How did you develope this info?
Thanks in advance

 

From the definitions posted on the web:

Hubcentric is when the wheel locates itself on a protrusion on the hub and therefore cannot be moved either up and down or from side to side (due to the hub protrusion). On the XK8, there is nothing on the wheel to locate itself onto the hub. The only physical part of the wheel that touches the hub is the flat area where the lugs are, so the wheel can actually be moved around on the lugs and it is the lug nuts that locate the wheel. If it was hubcentric, there would be no lateral, side to side play.

Now, I could be wrong....(wouldn't be the first time)....anyone care to share their knowledge?

Dunno about XJs, they could be different.....

Cheers,
Hamish
2001 MY XK8

 

hubcentric as you describe it, sounds exactly like the XK8. With the exception of , the hub center does protrude thru the wheel, and it is very tight. So much, that after a wheel refurbishing, my wheel would not fit w/o sanding down the interior of the wheel and getting the film of rust off of the hub. See the pic?

 

Hamish,

I hope I can explain this.

Wheel centricity is a function of the wheel design and manufacturing process - not the way the wheel is mounted. With a "hub centric" wheel the hub is the center and the lug holes and wheel circumfrence are off set, drilled, cast or punched, from the this hub center. Most car wheels, including XJ Jags are hub centric.
A "lug centric" wheel is manufactured with the circumfrence of the wheel off set from a circle formed by the lug bolt holes.
Just because the wheel hub on the car makes no provision for the use of the center hub hole on a wheel, it does not change the centricity of the wheel if that wheel was manufactured as hub centric.
Therefore, a hub centric wheel on a bal machine needs only a centering cone thru the center hub hole for the wheel to be mounted with all points on the circumfrence equal distant from the center.
A true lug centric wheel mounted on a bal machine will have some sort of appliance that utilizes all lug wholes to center the wheels.

 

Interesting stuff!! If I get the chance this weekend I'll pull the wheels and investigate further. From recollection, H20 is bang on about the rears, but I'm not so sure about the fronts, which is where I am getting the wheel wobble. My focus is to make sure that when I get the wheels balanced, that the shop is using the correct tools/methods/diagnostics to minimize the REPEATED journeys myself an others seem to have due an apparent lack of either training and/or knowledge of the RoadForce technology.

I can find no authoritative definition, beyond those of various wheel manufacturers and tire shops. But Hunter has this: http://www.gsp9700.com/pub/technical/4202T/6GLOS007.cfm

The curious part was that when I had the front tires RoadForced and had the shop use the tool for balancing lugcentric wheels, the difference was amazing; at least a reduction of 70% (by the Seat-of-the-pants method). Of course, this could be Alpha/Beta error, but that's another issue......

I'll throw this out to the Techs - what is the best method / set-up for a Hunter GSP-9700 when having your tires RoadForced?

Cheers,
Hamish
2001MY XK8