Wheel balance machine calibration
Discussion
I've just had my front wheels balanced again due nagging high speed vibes - I was all set to get the tyres replaced. They were out by 20g each side which is fairly significant apparently. The fact they were out the same each side seems rather a coincidence. They were balanced not long ago by a major servicing chain. The chap who did them this time (different organisation) reckoned the balance machine used previously was not properly calibrated. Has anybody else experienced similar or gone so far as to ask to see a recent calibration certificate? Do they hold such things? Cheers.
I don't know enough about how these machines work but I would have thought a calibration problem would result in the wrong amount of weight specified.
Though that's stating the bleeding obvious, bare with me a bit.
Once they have banged the weights on, they should do a final test to make sure it's balanced. If the calibration is out by say 10% then so long as the final test shows it's within a few grams then 10% of not much is square route of F'all.
Another way of putting it is that if the system is perfectly calibrated then it should get it right first time. If it's out then you might need to add a second smaller weight which actually indicates the magnitude of the calibration error. If the gumby technician can't be bothered to do the final check then your stuck with the calibration error.
It is most likely that these systems are capable of self calibrating. The much more likely problem is operator error or, I couldn't give a flying fukc 'cause I'm on minimum wage and don't take pride in doing a job properly.
What got me thinking about this is I used a cheap local one man tyre fitting company and had vibration issues. I remembered thinking he must be confident in his balancing machine as he didn't check the results! It wasn't confidence it was apathy. Still he's out of business now so no one will have to contend with the poor workmanship!
Though that's stating the bleeding obvious, bare with me a bit.
Once they have banged the weights on, they should do a final test to make sure it's balanced. If the calibration is out by say 10% then so long as the final test shows it's within a few grams then 10% of not much is square route of F'all.
Another way of putting it is that if the system is perfectly calibrated then it should get it right first time. If it's out then you might need to add a second smaller weight which actually indicates the magnitude of the calibration error. If the gumby technician can't be bothered to do the final check then your stuck with the calibration error.
It is most likely that these systems are capable of self calibrating. The much more likely problem is operator error or, I couldn't give a flying fukc 'cause I'm on minimum wage and don't take pride in doing a job properly.
What got me thinking about this is I used a cheap local one man tyre fitting company and had vibration issues. I remembered thinking he must be confident in his balancing machine as he didn't check the results! It wasn't confidence it was apathy. Still he's out of business now so no one will have to contend with the poor workmanship!
Just as a point of interest, I fitted my last tyres on a manual/home made tyre machine (used a compressed air bead breaker though), and my nearside front had 60g, and I assumed this was a dinked wheel.
Took off the Eagle F1, replaced with new, lots of soap, levered it on smoothly without stretching, sat the bead with 15psi, ran upto 40psi to bed it. Smooth as silk on the road! No weights at all.
So, 60g of weight, purely because the tyre fitters use bugger all soap, use an automatic machine which rips tyres onto the rim, and bed the bead by letting it pop on a 50psi! And that was one of the better places!
Alot is down to the fitting of the tyre. My brother and I have no fit 8 Eagle F1's to our wheels and not one has needed blancing even upto 1.2 units of speed, just a smooth transition with no vibration! Find a better fitters!
Dave
Took off the Eagle F1, replaced with new, lots of soap, levered it on smoothly without stretching, sat the bead with 15psi, ran upto 40psi to bed it. Smooth as silk on the road! No weights at all.
So, 60g of weight, purely because the tyre fitters use bugger all soap, use an automatic machine which rips tyres onto the rim, and bed the bead by letting it pop on a 50psi! And that was one of the better places!
Alot is down to the fitting of the tyre. My brother and I have no fit 8 Eagle F1's to our wheels and not one has needed blancing even upto 1.2 units of speed, just a smooth transition with no vibration! Find a better fitters!
Dave
I spoke to a small indy years ago after I had problems which I was sure were related to wheel balance. The big chains said they were fine. The wee man said that his machine was calibrated to +/- 5 grams, whereas the big chains don't.
He balanced them and they were fine.
I once balanced the wheels on a Passatt with one of those wee Gunsons kits, where you balance the wheels on a calibrated gauge on top of a milk bottle. Even that was better than the big chain's attempts.
He balanced them and they were fine.
I once balanced the wheels on a Passatt with one of those wee Gunsons kits, where you balance the wheels on a calibrated gauge on top of a milk bottle. Even that was better than the big chain's attempts.
tvrgit said:Interesting. I did a quick Google search on "gunsons wheel balance" and didn't turn up much. I'll keep looking but in the mean time do you have any more information on this?
...I once balanced the wheels on a Passatt with one of those wee Gunsons kits, where you balance the wheels on a calibrated gauge on top of a milk bottle. Even that was better than the big chain's attempts.
I can't find any mention of it on-line either.
Now that I think about it, I must have bought it about 20 years ago - I had the passatt in 1989 and that wasn't the first car I used it on.
I'll take a pic of mine - once the 4-foot drift against the shed door goes down a bit.
>> Edited by tvrgit on Sunday 12th March 12:39
Now that I think about it, I must have bought it about 20 years ago - I had the passatt in 1989 and that wasn't the first car I used it on.
I'll take a pic of mine - once the 4-foot drift against the shed door goes down a bit.
>> Edited by tvrgit on Sunday 12th March 12:39
Found it!
It was called the Gunson Wheelrite. You bolted it to the back (or front) of your wheel, depending on the offset. The instructions told you what pair of holes to use, for your car - for example the VW Passat might have been "pair No 4".
Then you put the wee metal plate on top of a milk bottle or upended brick, and on the other side of the bubble is a small pointed dimple that you put in the centre of the metal plate. Then you
placed weights on the rim until the bubble was centred. Then you stuck the weights on.
It sounds crude, but it was surprisingly accurate and solved a wheel vibration problem that I had following a couple of attempts by a big chain with a crap machine.
I still can't find any reference to it online though - perhaps it's been discontinued.
It was called the Gunson Wheelrite. You bolted it to the back (or front) of your wheel, depending on the offset. The instructions told you what pair of holes to use, for your car - for example the VW Passat might have been "pair No 4".
Then you put the wee metal plate on top of a milk bottle or upended brick, and on the other side of the bubble is a small pointed dimple that you put in the centre of the metal plate. Then you
placed weights on the rim until the bubble was centred. Then you stuck the weights on.
It sounds crude, but it was surprisingly accurate and solved a wheel vibration problem that I had following a couple of attempts by a big chain with a crap machine.
I still can't find any reference to it online though - perhaps it's been discontinued.
Well done that man.
I also couldn't find any direct reference on the internet but I did learn some useful stuff whilst surfing.
1.You can balance a wheel by placing it on an axle and spinning it. When it stops the light point is at the top so place a weight here. Grossly simplified buy explains the principle.
2.Though with a little care the above method can be very accurate it won't correct for a side to side imbalance (shimmy)
3.Unless you are into engineering something quite exotic then you are unlikely to DIY a dynamic balance anywhere near what is possible from the professional equipment. Though even the proper kit is limited by operator error and poor maintenance/calibration. Best solution is to find a tyre fitter who gives a dam. How you do this is anyone's guess though!
I also couldn't find any direct reference on the internet but I did learn some useful stuff whilst surfing.
1.You can balance a wheel by placing it on an axle and spinning it. When it stops the light point is at the top so place a weight here. Grossly simplified buy explains the principle.
2.Though with a little care the above method can be very accurate it won't correct for a side to side imbalance (shimmy)
3.Unless you are into engineering something quite exotic then you are unlikely to DIY a dynamic balance anywhere near what is possible from the professional equipment. Though even the proper kit is limited by operator error and poor maintenance/calibration. Best solution is to find a tyre fitter who gives a dam. How you do this is anyone's guess though!
leorest said:
I also couldn't find any direct reference on the internet but I did learn some useful stuff whilst surfing.
1.You can balance a wheel by placing it on an axle and spinning it. When it stops the light point is at the top so place a weight here. Grossly simplified buy explains the principle.
Provided that there is no friction in the axle!
leorest said:
2.Though with a little care the above method can be very accurate it won't correct for a side to side imbalance (shimmy)
Surprisingly, side to side balance isn't that important, especially with alloy wheels - do they stick weights on both rims? No. I have had wheels balances with weights on the inside rim only, or with stick-on weights near the hub centreline, and never had a problem - IF it's done accurately.
leorest said:
3.Unless you are into engineering something quite exotic then you are unlikely to DIY a dynamic balance anywhere near what is possible from the professional equipment. Though even the proper kit is limited by operator error and poor maintenance/calibration. Best solution is to find a tyre fitter who gives a dam. How you do this is anyone's guess though!
That wee Gunsons kit was as accurate as it needed to be - dynamic wheel balance = shimmy, that kit = smooth. You're right - best bet is to get somebody who knows what they are doing. I had to when I bought a Granada - the Gunsons kit doesn't work on 5-stud rims (you can't centre it properly).
tvrgit said:I did say gross simplification. From what I've read a slight amount of friction can be overcome by vibrating the assembly or failing that rolling the axle along two level beams.
Provided that there is no friction in the axle!
tvrgit said:What makes an alloy wheel more tolerant of imbalance? The requirements for side to side balance does seem to be far less than the static balance, but the fact that "they" don't stick weights on both rims doesn't mean it's not necessary. I grant you that in most instances a wheel/tyre can be balanced within acceptible tolerances from one point (I've had this done in the past as well) but there has to be a case where it goes outside acceptable tolerances and when this happens you either have to correct it or replace the wheel or tyre.
Surprisingly, side to side balance isn't that important, especially with alloy wheels - do they stick weights on both rims? No. I have had wheels balances with weights on the inside rim only, or with stick-on weights near the hub centreline, and never had a problem - IF it's done accurately.
I did see a video where a suspended wheel was spun up to speed and a laser pointer, which was attached, traced a shape on the wall corresponding to the type of imbalance. Vertical line means a simple imbalance. Horizontal line means shimmy and a circle is a combination of the two. I'm just off to the garage to try and knock up one of these..... I might be some time
leorest said:
What makes an alloy wheel more tolerant of imbalance?
It's lighter for a start, and also (because it's cast rather than pressed) more likely to stay in shape than a steel wheel.
Sticky-on weights work with alloy wheels, eez all I know!
That wee Gunson gadget thingy works perfectly with alloy wheels, I know also, and certainly better than a gibbon working his (possibly poorly-calibrated) dynamic balance machine.
The full story is available here:
[url]www.haggishead.myby.co.uk/complain/tyres.html[/url]
Anyone ever blanced a wheel on it's own, sans tyre?
I have fitted several tyres now, and the more you have to stretch them to fit them (manually), the worse the wobble when they are on the car!
Also, as tyres wear, they can become unbalanced.
My current tyres run upto 1.1 Leptons at the front with very VERY minor vibration through 0.8>0.85 leptons, then subsides to nothing (could very well be natural frequency vibration)... I fitted them manually, loads of soap, cleaned the rim bead seat thoroughly, sat the tyre onto the bead at 15psi and then bedded them @ 40psi before reducing to running pressures.
From my example above / / going from 60g weight to 0g weight and it being perfect I do worry about how agressively some people fit tyres!
Considering my brother and I are on our 12th Eagle F1's in 195/50R15 and ALL the ones we've fitted have been good enough to not need balancing, I can pretty much say the other tyre was likely not a one off, but was fitted badly at a proper place that I went to!
Even an automatic machine can fit with 0 balance needed on good straight rims. My brother worked at a fitters and the manager guy used to have competitions when they fitted tyres on quiet days, to get 0,0,0 on the blancing machine.
But why bother doing a good job for twice as long when you can just balance a badly fitted tyre twice as quick and get 2x more work and charge the same?
Just like all car stuff, you'll never get more care than if you do it DIY or get a very trusted place to do a proper job imho!
Dave
I have fitted several tyres now, and the more you have to stretch them to fit them (manually), the worse the wobble when they are on the car!
Also, as tyres wear, they can become unbalanced.
My current tyres run upto 1.1 Leptons at the front with very VERY minor vibration through 0.8>0.85 leptons, then subsides to nothing (could very well be natural frequency vibration)... I fitted them manually, loads of soap, cleaned the rim bead seat thoroughly, sat the tyre onto the bead at 15psi and then bedded them @ 40psi before reducing to running pressures.
From my example above / / going from 60g weight to 0g weight and it being perfect I do worry about how agressively some people fit tyres!
Considering my brother and I are on our 12th Eagle F1's in 195/50R15 and ALL the ones we've fitted have been good enough to not need balancing, I can pretty much say the other tyre was likely not a one off, but was fitted badly at a proper place that I went to!
Even an automatic machine can fit with 0 balance needed on good straight rims. My brother worked at a fitters and the manager guy used to have competitions when they fitted tyres on quiet days, to get 0,0,0 on the blancing machine.
But why bother doing a good job for twice as long when you can just balance a badly fitted tyre twice as quick and get 2x more work and charge the same?
Just like all car stuff, you'll never get more care than if you do it DIY or get a very trusted place to do a proper job imho!
Dave
A perfectly made point RE: DIY
Now when I googled "define Lepton" it returned fundamental particle? Am I missing something here or are you balancing them wheels mighty fine to the sub-atomic level
If so then you sound like the sort of man I need to call upon when I fit the next set of boots
Now when I googled "define Lepton" it returned fundamental particle? Am I missing something here or are you balancing them wheels mighty fine to the sub-atomic level
If so then you sound like the sort of man I need to call upon when I fit the next set of bootsGassing Station | Suspension, Brakes & Tyres | Top of Page | What's New | My Stuff