puncture repair advice sought. - Page 4

06-09-2013, 06:50 PM

This doesn't make sense to me - you say this:

1. The same tyre when new, required only 10g, according to the tyre fitter at the time.

2. The imbalance does not seem to correspond with the additional weight of the repair mushrooms either.

3. The conclusion seems to be that the tyre has developed a significant imbalance during its 6000 miles or so of use.

I have checked the balance of wheels if I have removed them for any reason and yes, the balance has altered as the tyre wears but not very much.
You are suggesting that the tyre now requires 73g compared to 10g when fitted, purely due to wear - I just don't believe it!

I don't know what you do for a living but if you need to travel and are in the Peterborough region in the near future bring the wheel to my place and I will balance it for you using proper weights (not roofing lead) and it will not cost you anything.
I am concerned at you fitting a whopping 73g of weight!

(I reuse weights and find Sellotape Outdoor Sticky Fixers work well.

utopia · 07-09-2013, 01:50 PM

Yep, I agree. It didn't make a lot of sense to me either.
And there are no signs of any weights having come unstuck since the tyre was first fitted.
Also don't forget that I've minimised the weight needed by careful positioning of the tyre, so 73g is the least possible weight needed to balance it.
However I do have confidence in my method and, as I explained previously, I reckon that a more accurate method would merely find that more weight was needed, not less.
But I share your unease at both the high imbalance and the apparent changes over the life of the tyre.

Thanks for your offer, but I'm unlikely to be able to get the wheel over to you.

Maybe I should get the balance checked professionally.
I probably wont though, as I don't believe there is an error in my balancing, but if I do I would be prepared to bet you a whole half pint of beer that it needs at least 65g...and that's playing safe.
Note that my results were repeatable on two different days, starting from scratch each time. And the wheel bearings appear to be in perfect nick. Also the "pile of bricks" was a bit of a fib ...my setup was actually much more rigid than that sounds, and horizontal too.

One possibility is that the original balancing was inaccurately done, but these guys are bike-only specialists of long standing, so its unlikely unless I was just unlucky and got "the lad" on that day.
Another might be that the tyre has slipped around the rim, but since the bare wheel has been shown to be in good balance, and the original imbalance was (apparently) only 10g, I don't find that particularly convincing either.
Is it worth considering that this is a double compound tyre, and could uneven wear be the result of uneven spread between the two different compounds somehow ?
Or is it all just slightly on the extreme edge of normal wear characteristics ?

This tyre has done quite a few miles by some people's standards ..6,500 so far, and I'm expecting 8,000 or more before its even lost a useable profile.
Lets say a minor imbalance occurred early in the life of the tyre, either through inaccurate original balancing or simply through wear.
That will then cause a wheel vibration resulting in uneven loading of the tyre's contact patch over each rotation.
Is it fair to assume that this would result in uneven wear, which would in turn worsen the vibration ? ...resulting in further uneven wear ...and so on.
That sounds to me like a system that doesn't just get worse at a steady rate, but accelerates.
Exponential tyre wear.
.....which increases massively in the later stages.
.... but is not seen on most tyres because they simply don't often do such mileages, or if they do they certainly aren't rebalanced before going in the skip.
Then again, your own experience, Zhango, goes beyond this, I guess.
I dunno. Its certainly a surprising situation.

The roofing lead was fine once I sussed that blu-tac was the magic ingredient which allowed me to position it exactly where I wanted. For test purposes only, obviously.
I was going to buy some proper weights, but mostly they're "lead free", and thus even more bulky, particularly 73g of them.
Also, the lead is nice and soft, so it moulds nicely to the curve of the rim. I might try it with your sticky pad idea ...or my own version involving double sided tape and a layer of inner tube rubber.
....you have to laugh, eh ?
Ultimately, neatness may demand proper weights.

07-09-2013, 04:03 PM

Quote:

Originally Posted by utopia

Maybe I should get the balance checked professionally.

That might be a good idea - it would prove that your method is absolutely brilliant or complete ****ing ****

It would be nice to know, and then if it is brilliant you will have the confidence to use it again and not take my advice about getting a balance shaft with low friction bearings.

I do like the amount of thought you give to problems and challenge conventions though. The downfall of the great British Motorcycle Industry was the opposite - copy what has always been done because it worked and don't bother about trying anything else.

06-09-2013, 06:50 PM	#46
zhango Guest Posts: n/a	This doesn't make sense to me - you say this: 1. The same tyre when new, required only 10g, according to the tyre fitter at the time. 2. The imbalance does not seem to correspond with the additional weight of the repair mushrooms either. 3. The conclusion seems to be that the tyre has developed a significant imbalance during its 6000 miles or so of use. I have checked the balance of wheels if I have removed them for any reason and yes, the balance has altered as the tyre wears but not very much. You are suggesting that the tyre now requires 73g compared to 10g when fitted, purely due to wear - I just don't believe it! I don't know what you do for a living but if you need to travel and are in the Peterborough region in the near future bring the wheel to my place and I will balance it for you using proper weights (not roofing lead) and it will not cost you anything. I am concerned at you fitting a whopping 73g of weight! (I reuse weights and find Sellotape Outdoor Sticky Fixers work well.

07-09-2013, 01:50 PM	#47
utopia No turn left unstoned Join Date: Jun 2010 Location: leicester Bike: M750 Posts: 4,546	Yep, I agree. It didn't make a lot of sense to me either. And there are no signs of any weights having come unstuck since the tyre was first fitted. Also don't forget that I've minimised the weight needed by careful positioning of the tyre, so 73g is the least possible weight needed to balance it. However I do have confidence in my method and, as I explained previously, I reckon that a more accurate method would merely find that more weight was needed, not less. But I share your unease at both the high imbalance and the apparent changes over the life of the tyre. Thanks for your offer, but I'm unlikely to be able to get the wheel over to you. Maybe I should get the balance checked professionally. I probably wont though, as I don't believe there is an error in my balancing, but if I do I would be prepared to bet you a whole half pint of beer that it needs at least 65g...and that's playing safe. Note that my results were repeatable on two different days, starting from scratch each time. And the wheel bearings appear to be in perfect nick. Also the "pile of bricks" was a bit of a fib ...my setup was actually much more rigid than that sounds, and horizontal too. One possibility is that the original balancing was inaccurately done, but these guys are bike-only specialists of long standing, so its unlikely unless I was just unlucky and got "the lad" on that day. Another might be that the tyre has slipped around the rim, but since the bare wheel has been shown to be in good balance, and the original imbalance was (apparently) only 10g, I don't find that particularly convincing either. Is it worth considering that this is a double compound tyre, and could uneven wear be the result of uneven spread between the two different compounds somehow ? Or is it all just slightly on the extreme edge of normal wear characteristics ? This tyre has done quite a few miles by some people's standards ..6,500 so far, and I'm expecting 8,000 or more before its even lost a useable profile. Lets say a minor imbalance occurred early in the life of the tyre, either through inaccurate original balancing or simply through wear. That will then cause a wheel vibration resulting in uneven loading of the tyre's contact patch over each rotation. Is it fair to assume that this would result in uneven wear, which would in turn worsen the vibration ? ...resulting in further uneven wear ...and so on. That sounds to me like a system that doesn't just get worse at a steady rate, but accelerates. Exponential tyre wear. .....which increases massively in the later stages. .... but is not seen on most tyres because they simply don't often do such mileages, or if they do they certainly aren't rebalanced before going in the skip. Then again, your own experience, Zhango, goes beyond this, I guess. I dunno. Its certainly a surprising situation. The roofing lead was fine once I sussed that blu-tac was the magic ingredient which allowed me to position it exactly where I wanted. For test purposes only, obviously. I was going to buy some proper weights, but mostly they're "lead free", and thus even more bulky, particularly 73g of them. Also, the lead is nice and soft, so it moulds nicely to the curve of the rim. I might try it with your sticky pad idea ...or my own version involving double sided tape and a layer of inner tube rubber. ....you have to laugh, eh ? Ultimately, neatness may demand proper weights.