what rpm are the front wheel/tires turn at say 50-53 MPH ( 25" diameter) got a "shake" I can't seem to find. (steering wheel) front end is new, tires were balanced. thanks
I guess what I'm wondering is: when they use the "computer balancers" in the tire shops, at "What Speed" are the tires Balanced at ?? are they being set to be balanced at 40 mph, 50, 60, 70 ?? Thanks
The tire balancer I use is a snap-on and the wheel gets spun by hand by means of a cranking handle. Not a big one, either. I was told to spin it by 3 full rotations to get enough momentum. I can't imagine it would be anywhere near 40 mph. Probably 20, if that. Looks fast, I guess. But really isn't. What kind of balance weights are you seeing? If they are the adhesive stick on type, where within the rim are they placed? IIRC, it matters according to the hub center and not towards the edge of the rim.
A 25" tire will rotate about 833 times within 1 mile. 60 MPH = 1 mile/minute = 833 tire RPMs. From there it is a linear relationship, so 30 MPH = 416 RPM and 120 MPH = 1666 RPM.
Wheel balancers typically spin between 100 to 300 RPM depending on sensitivity of sensors.
[This message has been edited by fieroguru (edited 09-02-2016).]
The majority of machines will detect any imbalance at lower speeds. I would start suspecting other areas, such as bearings or aligniments, at this point. Unless you have a single wheel with a disturbing amount of weights added.
I guess what I'm wondering is: when they use the "computer balancers" in the tire shops, at "What Speed" are the tires Balanced at ?? are they being set to be balanced at 40 mph, 50, 60, 70 ?? Thanks
The balance RPM doesn't matter.
If a wheel is balanced to be vibration-free at 200 RPM, it will be vibration-free at 1000 RPM (highway speed).
Conversely, if you have wheel vibration at 1000 RPM, the same vibration (just less strong) exists at 200 RPM.
Here are (IMO) the two most important problems with computer balancers: 1. Unskilled operators blindly following the machine, not knowing what they're doing. Also, balancing is typically charged a "flat fee", so going for multiple spins until the balance is excellent is unprofitable. 2. Balancer shaft wear. When a balancer is heavily-used, its wheel mounting shaft becomes worn. Then, the wheel centering cones develop play with the shaft. Therefore, the wheel can be installed off-center on the balancing machine, balanced to zero-zero, then when the same wheel is installed on a car, but properly centered, it vibrates.
I always considered balancing by garages to be troublesome... thus balancing is now something I DIY.
If you want to test the quality of the balancer's centering, take off the wheel once it's balanced to zero-zero, and then re-mount it on the balancer's shaft. Run a balance cycle again; the result should again be close to zero-zero. If re-mounting changes the result by more than lets say 1/4 oz (that's the smallest counterweight increment), then the balancer's (and operator's) centering is no good. So if the balance changes by just re-mounting the wheel on the balancer, expect that the balance can change by re-mounting the wheel on a car.
[This message has been edited by pmbrunelle (edited 09-03-2016).]
If it is more pronounced a specific RPMs, then it is likely a small imbalance, but at the right frequency (speed) it matches the resonance frequency of the suspension and excites it. Similar to exhaust drone being worse at a specific RPM range, some imbalances are worse at a specific vehicle speed (wheel rpm).
If you can rotate the wheels, the resonance frequency of the front and rear suspensions is different, so will move the rpm range where the imbalance excites the suspension. Or you could take the car back and get them re-balanced.
Many shops also have available "Road Force" balancing, but it usually costs more to start with. They balance the wheel/tire combo with a force applied, similar to being on the car at speed. They can find the balance of the wheel vs the tire, and can spin the wheel inside the tire for a more precise balance.
More than likely though, if the tires are new, and it started right after install, is that a weight has come off ( or a bad tire). This is especially true of the stick on weights for me- I can never get them to stay on. I've gone back to regular weights. Take it back, or swap the wheels front to rear, and see if it changes. If you suspect one tire, you can also stick a spare on there and see if the vibrations goes away.
It does static or dynamic balancing (user-selectable).
There's nothing wrong with a bubble balancer; it is equivalent to (with the right skills/patience I guess) static balance on a spin balancer. Bubble balancing was the standard method for a long time. For my parents' Suzuki Sidekick with narrow wheels, a plain static balance (with my spin balancer) is quite good enough. They rarely take it on the highway; mostly town driving.
My Fiero (especially with the 8" wide rears) gets the full dynamic balancing though.
I wouldn't recommend building your own balancer unless you're nuts; you could look for a good used spin balancer from a garage that's closing down, for example. I got my engine hoist for a good price from a garage that was closing its doors.
The other way is to pay a garage (with good-condition equipment) their hourly shop rate so they take the time to do the balancing well. On the last spin, the machine must show zero-zero on its display. I'm pretty sure I've seen shops slap on the weights, and then not perform a confirmation spin to make sure everything is okay.
Ive known people with brand new cars that had out of round OEM tires. One friend bought a new Magnum right after I bought one and it had 3 defective tires from day one.
I dont like computer balancing. If I have a choice id rather bubble balance them over the computer. Now the BEST way to balance them, and ive done it with a few of my high speed cars, is to find someone that balances them ON THE CAR while theyre spun. Its hard to find them these days when everyone wants fast and easy computer. There is one place in all of the Columbus area that does this. They jack up the front and have a motor that spins the front tires to any speed, say 120, and the tech puts his hand on the fender, or a glass of water, and adjusts the part mounted on the rim till it has no vibration. Then it shows him where and how much weight to add. Rears they just spin buy putting it in gear and spinning the tires up and doing the same thing. It also immediately identifies any bulges or out of roundness too. Tires can be trued by spinning them on like a special lathe that shaves tire tread. Ive had impossible to get balanced tires done and they were perfect. My Ferrari kit tires ran perfectly smooth up to 160mph. They did it once and they remained true for 6-7 years. With it this way, everything including lugs, hub and rotor are all balanced as a unit. If you rotate or move a tire, you may mess it up. I even marked one lug and associated stud so if it was ever removed, it went back on exactly the same. Like I said, theyre hard to find nowadays and place here charges $30 per wheel because it may take 30 mins for one wheel. The old saying, you get what you pay for applies here.
yea, I saw one of the "Balance on the car" setups about 15 years ago in a different city. I will inquire to see if anyone has one in Ocala. thanks for reminding me. I also suspect out of true rotors. seems there's no end to what this car has needed since we got it.
yea, I saw one of the "Balance on the car" setups about 15 years ago in a different city. I will inquire to see if anyone has one in Ocala. thanks for reminding me. I also suspect out of true rotors. seems there's no end to what this car has needed since we got it.
A dragging pad /frozen caliper, a bent rotor, worn rack bushing, worn tie rod ends, worn ball joints or a slightly bent aluminum wheel can also produce a vibration. I had an over 70 mph front end vibration on my 87 that I just could not cure. Finally it was time for new tires and wheels on all four corners, spin balanced and mounted by the Tire Rack. I just bolted them up. That cured it once and for all..
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
In the past, I would get rotors (for a different car altogether) that were made from cheap steel. I would mount them up, run them for a few days until they were plusing.. take them back off, have them cut straight, and put them back on. Smooth as silk. So they will heat set at a warped angle, and then you cut them to get them straight again.
