My bike (S2R) is currently in the shop getting new tires among a list of other things. I checked in today to see how it was going and my mechanic pointed out that when fitting the rear tire, an excessive amount of wheel weights were needed to balance the rear wheel/tire. I'm no mechanic so I can't provide specific weight details but let's say it's a strip of wheel weights about three inches long on both sides of the wheel. It looks...well...odd.
I asked if it was perhaps the new tire I had purchased that was so woefully out of balance and was informed that when it became evident that so many weights would be needed to balance the wheel/tire, they removed the new tire and put the wheel itself on the balancer which indicated that the wheel was off itself and the culprit, thus requiring the use of so many wheel weights. I also got the impression that this situation was very unusual.
A quick bit of history: I was rear-ended at a stop light at what I would consider a very low speed collision about a year ago. I was able to keep the bike upright and it only lurched forward maybe a foot, if that. It was a tap more or less. At the time and being cautious, I took the bike to another local shop which gave it a going over and found everything to be true and undamaged. Fast forward to now, my current mechanic ran a dial indicator on the rear tire and also found it to be true. I questioned this but was assured it was true.
So my question is, if the original stock wheel/tire only required a couple of weights on the rear wheel (and never exhibited any type of vibration, etc.), why now would it require so many weights (assuming that both mechanics are correct in their diagnosis that the rear wheel is true to form)? Has anyone seen anything similiar? Thanks in advance for your input and expertise.
If the wheel comes up way out of balance with no tire on it there can only be four causes:
Wheel out of true.
Incompetent mechanic.
Wheel balancer out of whack.
Really bad wheel bearings (see #2).
Wheel bearings wouldn't be the culprit on an SSSA bike.
Factory wheels aren't perfectly balanced BTW. How much weight did 'just' the wheel take?
Did they try un-inflating and breaking the beads of said tire, rotating it 180' while on the rim and then re-inflating and checking balance again? That's saved me a lot of extra weights when I run into a situation like that. (I used to work on bikes full time BTW)
Also, certain tires are more out of balance than others (just how it is). They also put a mark somewhere on the tire indicating (and here's where it gets odd) either the heavy spot of the tire, or the light spot of the tire depending on the manufacturer. Perhaps the shop got it wrong and put the heavy spot with the heavy spot of the wheel.
Lastly, in my experience the heavy spot of the wheel is where the valve stem is but your shop should know this.
If just the wheel needs an excessive amount of weights, IMO the wheel is probably bent.
Somewhat related...I know a mechanic who will turn the tire around the rim multiple times so he can use the least amount of weight on the rim. This guy is very anal about his work. It takes him forever to mount/balance a tire, but it makes for a cleaner looking job.
"Wheel bearings wouldn't be the culprit on an SSSA bike."
Doh! Correct you are. New wheels out of balance normal? Yes, more so if cast. Way out of balance? No.
Quote from: mojo on October 24, 2009, 09:24:16 AM
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Somewhat related...I know a mechanic who will turn the tire around the rim multiple times so he can use the least amount of weight on the rim. This guy is very anal about his work. It takes him forever to mount/balance a tire, but it makes for a cleaner looking job.
I love mechanics like that - they're trustworthy because you KNOW they will never do half a job. Probably good business as well - I know that I'm happy to pay guys like that, it's a win/win.
I've seen significant out-of-balance of a naked wheel, but it was a very old wheel.
The newer wheels seem quite good.
SSS wheels require a *good* adapter fit to balance properly.
A customer came in with an SSS wheel that had a *lot* of weight on it, turns out he had used a socket to 'adapt' it to the balancer shaft.
If the wheel has very little runout, it shouldn't require much (if any) weight to balance it without the tire mounted.
If the tire isn't uniformly seated on the rim, it can need a lot of weight to balance it.
I *always* spin a wheel with a freshly mounted tire and visually confirm that the tire has minimum runout, so that I'm balancing the best possible.
i don't think i've ever spun a tyre on a wheel after fitting and had it make a great deal of difference to balance. i did a dunlop slick on a mv wheel last week that needed about 70 grams. so i spun it 180 and it needed the same in exactly the same spot of the tyre. luckily the owner was watching and he supplied the tyres, but many owners are not so understanding of excess tyre fitting costs, especially when local competition fits them for free.
Thanks, I really appreciate everyone's input.
Duck-Stew - Unfortunately, I wasn't educated enought to ask those questions at the time. I'll be taking my bike to another dealer next week for my plastic tank replacement. They're going to take a look at the rear wheel. I'll let everyone know what they come up with.
Thanks again!
If it rides smoothly, don't sweat it...
Q
Quote from: Benjamin5150 on October 25, 2009, 09:21:17 AM
Thanks, I really appreciate everyone's input.
Duck-Stew - Unfortunately, I wasn't educated enought to ask those questions at the time. I'll be taking my bike to another dealer next week for my plastic tank replacement. They're going to take a look at the rear wheel. I'll let everyone know what they come up with.
Thanks again!
Yes, please let us know what they find. This is interesting and something isn't right.
I'll confirm Stuart / FlightCycles comment on balancing of the rear wheel if they don't have the right adapter.
Second -- check your swingarm around the welded section in the main tube if you were hit from the rear as a preventive measure. I've seen numerous "rear hits" where the rear wheel wasn't damaged but the swingarm itself bent or the (HAZ - Heat Affected Zone) area of the weld sheared (swingarm breaking) or small cracks develop. Not a common problem but I've seen it on 3 S*R series swingarms before with rear hits: 1) complete shear; 2) bent swingarm still being ridden; 3) cracks that were starting and it was still being ridden.
Thus take a very close look at it if/when the rear wheel is off. Again -- not a common problem but something folks should be aware of if hit from the rear.
We need to know how much weight is a lot.
Thanks again everyone for the input and interest. I still haven't gotten my bike back. As soon as I have and can give specifics, I'll post up before I take to the next dealer for the tank replacement.
Thanks again to everyone.