I would like to hear from those of you who have experience with RF balancing.

I had new OEM size Goodyear Eagle GT's put on stock 17" rims 3300 miles ago. They were originally RF balanced out to about 17Lbs each. I had a slightly noticeable tire vibration meaning they were not as smooth as I would have liked but not bad by any means. I am critical of smoothness so noticeable could be a non-issue for most of you.

Fast forward to today. The car has developed a vibration under acceleration between 30-50MPH. I wanted to rule out wheels & tires. No curb hits since the tires were installed or any physical damage. (that I am aware of) When the tires (with only 3300 miles on them) were checked, they read at 25-35Lbs of road force. They also checked the wheels for runout & out of round and are OK.

??'s

Is 17Lbs high?
Should they have been lower than that when new?

Why would they change to 25-35Lbs after only 3300 miles?
Is this typical? (my first experience with RF)

I asked the dealer to make them the absolute lowest they can be, when done they got 'em to 9, 11, 12 & 20 Lbs of RF. I have a smoother ride but still curious why the change in so little miles?

 

I'll fess up that I had no idea what you were referring to when you described "road force balancing." I looked it up, and found some discussion on Tire Rack's web site. For other readers, the gist of it is that one particular balancing machine manufacturer has a proprietary balancing system that also includes a roller that sits against the tread to measure how far out of round the tire might be. Gimicky? Maybe. Does it provide some useful information? Probably, but without significant experience with the machine and what variances are typically seen on most tires, I wouldn't get too excited about variance figures. Unless a tire is drastically out of round, I'd be more concerned about proper balancing.

I should mention that I'm not a pro mechanic, just a backyard/hobbyist type who's had plenty of time in some fairly well-equipped school and military hobby shops. The point being that anyone with broader experience should please chime in here.

Balancing on any of the machines that I've ever used is typically measured within fractions of an ounce. With that said, you can bet that the proper use of wheel balancing weights will usually have more of an affect on tire vibrations than the out-of-round variations that most tires will experience in daily-driven use. If a weight falls off, either from poor adhesion or clamping (depending on the type of weight), or from curbing, or whatever, that's more likely to affect your vibration than being out of round.

Lastly, I should add one more observation: I have an older sports car that sits in the garage for weeks on end until I get around to driving it. Fairly frequently, I will notice that when I first start driving, there's a vibration that *is* clearly related to the tire flat-spotting on the section of tread that it was sitting on. In that case, the tire *is* out of round. But this typically only lasts for a few miles, until the tread heats up enough to return to its originally molded (round) form. Also consider that those tires are summer-only tires, with a softer rubber compound than most street tires, so they might be more likely to deform in this manner when sitting for an extended period.

The bottom line is that I'm skeptical that your tires became so significantly out of round to cause this. I think you've been sidetracked by the hype from the tire-balancer, pushing their "road force balancing" concept. Most likely, you lost a wheel weight. When the wheel was re-balanced, the problem was solved.

I hope that helps.

Comments - anyone else? Concurrence? Disagreement?

 

Tire balancing is art! I have owned a digital balancer for about 3 yrs now. Got a sweet deal on one and with 4-5 cars, 2 sets of snows, track tires, etc it is already paid for!
Here's the best trick I've ever learned and what is usually NOT done at Joe's Garage. Drive the car, fully warm up the tires, bring into garage, lift etc, and immediately unweight the tires before any distortion can occur while cooling off.
Second, balance precisely, release weigh from machine, spin on shaft, retighten and recheck. This will uncover, hub issues, improper positioning on machine etc. .25 gms is undetectable anywhere I've ever seen including my Lotus. But from a.5gm correction up, 2-3 tires all off .5gm can, if they get in sync, give you those annoying vibes that come and go.
Personally, I rebalance all tires at the end of each season. 5-1000 miles on a tire can alter their balance. Most tires tend to need less weight as they get more miles because they (if alignment is good) roll more true over time.

As said above, almost all high performance tires are terrible for ~5-minutes or 2-3miles till they warm up. That is equivalent to your car being driven down street to tire shop. or being move into a garage after you wait an hour.

 

Rothe, you make some good points. I am looking for others who have used RF balancing and what types of results their garage gave them. I didn't know what RF balancing was till I saw it on here. I did the research & decided to try it. RF is measured in pounds to the road but they balance them with weights in fractions of an ounce. Two different measurements.

I am not saying my tires became out of round, the "vibration" was negligible. I am just fussy. What I am wondering is why the change in readings. I am curtain I didn't throw a weight and am familiar with stiff tires needing some miles on them to smooth out so I ruled those possibilities out.

You gotta try it on your next new set of tires. I had a Suburban work truck that just had tires put on it, left the shop had a vibration so I took it back. They re-spun 'em and said they were the best they could get them. The machine was in calibration and they started blaming wheels, driveshafts etc. They said there was nothing more they could do for me. I left with the same vibration and went to a place who could fix both wheel/driveshaft problems AND had a RF machine. The RF machine solved the problem because they had the right tool to place the heavy spot of the tire on the light side of the rim. Rides like it's on glass now.

 

Some good ideas also DD. I like your idea to spin on the shaft & re-check because after I return to a shop for a shoddy balance I ask if they did this. None ever do. When I request they do then they dig a little deeper to get things a little more precise. I even ask them to turn the rounding function off so they can read the exact amount of weight needed!

I run from a place that says spinning them on the shaft to recheck them will not yield any better results than the first balance. I just think it reveals the machine is out of calibration or the user does not have the correct attachment to the machine.

 

First, vibration that only occurs under acceleration is probably not wheel/tire vibration - unless you're experiencing 'slot vibrations' (vibes that occur at particular speeds as you would accelerate from, say, 0 - 100.) Vibes that occur during accel from, say, 0 - 40 would more than likely be a result of drive joints, etc.

I've been a pro tech for 41 years and have seen all the wrong ways (I think) to balance tires. It mostly comes down to tire busters are given a two minute intro to tire balancing when they begin working at a tire store - mount the tire and wheel to the balancer, spin it and slam the weights on. Spin it a second time to check. Nail the wheel on with an impact wrench and you're done. It's a numbers game, they need to move as many tires out the door as possible. Take the money and run. For most peeps that's good enough, for those that come back they'll spend a few more minutes re-doing the job, maybe a bit better.

There's a number of reasons why balancing the second time works better. First, the tires have been stacked in a back room, on their sides or in racks. They take on a 'set' that is not even close to how they will eventually 'set' once mounted. Secondly, a newly mounted tire has (hopefully) been lubed to facilitate mounting to the wheel. The tire will assuredly slip around the wheel over the next several days as it seats in on the rim. This slippage will obviously negate any prior balancing. So much for buying tire and wheel combos online and paying for road force balancing (although the load roller will aid in seating the tire to rim - more on that later). Thirdly, that new tire has nice soft rubber with cords inside that can shift. Driving cycles will allow the tire to warm and cool, resulting in the rubber and cords hardening in a particular position. Sometimes, the second time the tire is balanced they will still be warm from driving (tire stores typically don't want a complainer sitting in the office talking to other customers) and in a better state of concentricity. As stated in a previous post, performance tires are more susceptible to this than common tires as most performance tires have Nylon in them and Nylon is notorious for flat-spotting when parked on a cool surface. (The reason Nylon is used is to control tire diameter. Think of a nylon windbreaker, when you heat a loose thread with a lighter/whatever the thread shrinks. With wide performance tires there is a problem with centrifugal tread growth at speed, resulting in the tire's tread wearing prematurely in the center. Nylon is used to control the phenomena as it shrinks when it warms and tightens the center tread diameter.)

Another balancing issue is the wheel, is it hub-centric or or lug-centric? These terms relate to how the OEM intended the wheel to be concentrically located to the hub. Some, the wheel center is snug to the hub's raised area, other's are located by the hub to wheel studs. You can almost bet 99.9% of every tire store will mount every wheel to their balancer using a centering cone. That's just fine as the majority of wheels are located this way but some are not and that will cause a real problem. Some OEM wheels and a lot of custom wheels are lug centric, if you're having problems getting it right it's a good idea to check with the manufacturer(s).

Road force balancing, what is it? Hunter Manufacturing pioneered the modern road force balancer. There may be other manufacturers now (I haven't checked lately) but Hunter has been regarded for many years as the premier balancing and alignment equipment company. While newer models have additional innovations and features, basically road force balancing is a balancer that includes a roller that can apply up to 1250 pounds of pressure against the tire's tread. This does a number of things including seating the tire to the wheel (as best possible without first mounting the wheels to the car and driving on them) and allows the machine to measure and record deflections caused by soft/hard spots (density variations in the rubber's composition, high/low spots in concentricity, etc.) As a mounted tire and wheel assembly it also measures deflections from the wheel as it is passed through the tire to the tread. The amount of deflection is measured in pounds. While the exact numbers may escape me at the moment, I seem to recall some manufacturers considered 40 pounds to be acceptable - that says a lot about their engineering... When I worked at a Lincoln dealer we found that tire/wheel assemblies on Navigators in excess of 15 pounds to be noticeable by most of our customers. Sometimes it is a matter of the actual vehicle's refinement, that Lincoln owner is going to expect a better ride than someone driving a clapped-out Chevy.

So, I have a tire/wheel combo that shows 32 pounds of road force, what is done to correct it? The balancer has two arms with rollers that extend to contact the wheel rim. As the rim is slowly rotated the arms measure the wheel's concentricity/deflection. The balancer then computes how much the assembly deflected and where and how much the rim deflected. It then assigns a number to each, representing severity of deflection. Let's say, for example, the 32 pound total deflection has a rim that measures 16 pounds at zero degrees away. The assembly is removed from the balancer, the beads broken and the tire rotated on the rim 180 degrees. Air it back up and remount on the balancer. In a perfect world the 16 pound tire deflection will now be opposite the 16 pound wheel deflection and everyone is happy. A quick spin balance and the problem is solved.

As you can see, the previous example worked out nicely because the offsetting weights were close enough to cancel each other out. What would you do if the wheel were only 2 pounds off? You see, this is the rub. How much time does a man (let's say you want an actual mechanic that understands all of this vs. a kid that had a choice between working at a tire store and McDonald's) that makes a living on commission spend sorting all of this out? First he mounts all your tires and wheels. Then he mounts each assembly on the road force balancer and records both the total and wheel deflections. Next he sorts through the measurements to make sure each tire is mounted on the wheel that will yield the best reduction of deflection. Then he dismounts whichever assemblies require attention, remounts them on their best mated wheel and proceeds to recheck them all on the balancer. Would you be willing to pay him $100+ per hour to perform this service as required with no estimate of how long it will actually take? I didn't think so. I used to work in a shop with customers that had the cars, ***** and money to drive @ 200mph. $4000+ tire sets on wheels that cost $8000 each. Yeah, they'll pay another $400 labor to have them mounted this way. If I elected to do this on my own car I would have to go in on a Saturday in order to have enough time to do it.

So, is road force balancing worth the expense? Sure, just don't expect all that work for $100. What you'll get is a measurement of how good/bad each assembly is and if it isn't a drastic number you'll get the same balance job a regular balancer provides. If it is way off, they'll probably spin that one tire on that one wheel. If it continues to be bad, and the wheel isn't whacked, they'll either try to sneak it past you, blame it on your 'bad' wheel or toss another tire on. Props to Tire Rack - whenever I've had a tire that had a bad number they never questioned it. They simply send out another tire with a return label for the defective one (of course, that bad tire had never been 'on the ground'.)

I know this is a long post. There is a lot more I could include but this should provide enough info for now. The best advice I can provide is to have the tires balanced at mounting, drive them for a couple weeks then have them rebalanced. And as for why they go out of balance, as they wear any density variations wear away - sometimes for the good, sometimes not. Sometimes little impacts can cause slight damage to the carcass or wheel. Poor alignment wear can cause issues. Etcetera, etcetera, etcetera...

 

I had vibrations with the Eagle GTs on an XJ8. After all sorts of balancing and even unnecessary rim balancing, and new sets of Eagle GTs from Goodyear, I replaced the tires with Continental Extreme Contact DWS and the vibrations went away. Goodyear was kind enough to take the tires back. These tires unfortunately are unsuitable for the Jaguar.

 

good post beav, with a couple exceptions. or Hunter rf balancer does not show measure pounds, but inches of deflection. .026" spec for P(passenger car) tires and .039" front LT(light truck) you can do 2 types of measurement for rf correction. tire mounted or bare rim. its nothing more than the machine showing the low spot in the rim and the high spot in the tire. you mark both the tire and rim and then let the air out, break the beads. no need to dismount. you just spin the tire on the wheel till the high and low marks line up for the "roundess" matching of that tire and wheel combo. then air back up and rebalance. yes obviously the low the number the rounder the tire. No perfection in balancing will correct an out of round tire it is NOT A GIMMICK. For an extreme example, I can drill a hole in a square block of wood and balance it to perfection. now how will that ride on the road..........exactly its not a gimmick. I have seen rims bent I would swear looking at then but to rf the assemblies they are within .026 spec or lower.
to answer the original posters question on why 3300miles down the road....pothole, railroad tracks, rough roads, and 2 ton vehicle at 70mph, steering, acceleration, braking, tire wear etccc all this contributes to tires "breaking in" the oils in rubber, the set of the belts etc all shift and move and can/do change balance and roundness. this is why many raceteams "breakin tires" BEFORE they actually race them. having sets for practice and race.
when I put new tires on wheels, or when I buy new wheels. I spin them bare before I mount tires to find the rims low spot, and I paint a stripe on the inside that I will then use as a refferance for the bare rims low spot incase I have a high spotted tire out of spec then I know the bare rims low spot and can rotate the high spot of the tire over the low spot of the rim, and then balance. and while this is being discussed in the X forum, if you have a xk or sport tired XJ or R, you can expect about 20k out of a set of tires. So at 3300 miles youve worn 20% of tread off. Higher numbered rf tire/wheel assemblies should be put further away from the driver to minimise the feel of the tire that higher than the rest but maybe is fine for its spec. Our new Hunter even has a measurement to find the pull of a tire and cen tell you which spot on the car to minimise or stop a tire pull issue. No I havent used that yet. I find the better the tire, the weight and rounder the tire is. PS2's 3's, Michelin pilot sports are a couple that come to mind right away that are very well made taking little weight to balance and are more round than others. And just cause a tire is NEW does NOT meen they will be in spec for roundness as Ive seen on occassion.

 

Yeah, I kinda took liberty with not being totally specific, i.e. using the word 'deflection' for both weight and distance measurements. Obviously, distance/'run out' deflection would be measured in inches, weight deflection/'road force' being measured in pounds.

Maybe the newer model Hunters do not reflect road force in weight but the ones I used at Ford/Lincoln/Mercury/Isuzu/Saab/Porsche did. Road force was displayed in pounds. Maybe it's a difference in software provided or a little smoke and mirror/song and dance Hunter told us but we can both agree that whatever the case may be it works very well.

We could measure the bare rims, mount the tires and see the results. The closer the wheel measurement was to the tire measurement the greater the ability to counteract the road force. But if you had a 3 wheel and mounted a 29 tire to it you were going to look for a wheel with a higher number and probably end up dismounting/remounting at least two tires. Plus, with low profile performance tires it's usually difficult to spin a tire just by breaking the beads.

Anyway, my original point was road force is good, but don't expect it to be any better than the amount of time and effort a well trained tech is willing to invest in it, for what you're willing to pay. There's a lot more to it than slapping a weight on the wheel while the customer isn't looking...

 

I was hesitant to return to GY but I had a couple of recommendations from guys with 'em on the X. Now that I have run them for almost a year I know why they liked 'em. They stuck to the roads in winter here in Michigan and on dry pavement they are braver than I am!

Was all of your balancing done RF?

 

Yes they were. The following day after the tire purchase, the car was taken to the dealership because of the vibrations. Three of the tires were found to be out of specification with the road force machine. Jaguar's recommendation was to replace the tires with the Continentals. The tires were reinstalled and balanced with particular attention paid to the alignment of the heavy side of the tires to no avail. Filed a complaint with Goodyear and they agreed to replace all four tires. Over a month afterwards, got the new tires installed, same problem. Went to a different tire shop, after two or three balancing sequences, I was told to try a rim shop. The rim shop had no way of telling me the condition of the rims without putting them on their machine at a cost of over $500. Paid and was then told that the rims were not bad, still vibrations. Had enough, time and money wasted. Got the Continentals installed and the vibrations went away. The following summer, I needed tires for my Rolls, called Goodyear, and was told to take the tires to a Goodyear center. The manager of that particular center here in Massachusetts, is extremely knowledgeable. She took a look at the tires, measured the tread depth and offered to just give me four new tires for the Rolls. I now buy all my tires from her. The side walls of the Eagle GTs are stiffer than that of the Continentals, hence nuances of the road were transmitted to the car, but it felt as if the car was being driven on rails, very precise steering. In the heavy snow we had that year, the tires were useless, skidded everywhere. Even though the Continentals side walls are softer, they performed extremely well in the snow, rain and dry roads. The DWS designation means Dry, Wet and snow. My experience is with an XJ8, so it may not be applicable to other models.