Bicycle Mechanics - My Kinlin XR-200 Rim is Suddenly Flexing
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09-19-12, 08:44 AM
I had a Kinlin XR-200 20 hole rim built up with Sapim CX-Ray spokes and a bikehubstore lightweight hub and it's performed very nicely for the whole spring/summer, but in the last month I've noticed what I believe to be some significant flexing.
Both the rear and the front also went significantly out of true and after having both re-aligned, I still hear brake rubbing when I get up and sprint hard out of the saddle.
I'm not the lightest guy but I'm also not a clyde. I weigh 155lb and I hadn't had any issues like this for the entire time I had them until now.
Any ideas? Thanks for any help.
09-19-12, 09:15 AM
1. Pic of the front and rear hubs showing the lacing would be nice.
2. Pic from the side across the surface of the inner wall of each rim would be nice as well - to check for any indications of spoke pull through.
3. What was the original tension of the 20 hole front when finished?
4. How many holes is the rear - and what was the tension of the drive side rear when originally done?
09-19-12, 08:55 PM
Hope these are of some help. The rear was a 24 hole, laced 1 cross. The front was laced radially.
I honestly don't know the tensions they were built to as I knew barely anything about wheel building when they were built. I just figured out what I needed and handed them over to the head mechanic at my LBS :-( Sorry I can't be more detailed. Any info or opinions you might be able to share would be greatly appreciated! Thanks!
09-19-12, 09:12 PM
Okay, I'm looking at that rear wheel and I personally don't like what I see.
That lacing used - is what many would call machine built lacing.
Normally when I custom build a wheel - I'll lace one of two ways...
1. ALL pulling/trailing spokes heads in.
2. ALL pulling/trailing spokes heads out.
One or the other, not a mix of both.
Right now you have heads in - elbows out pulling/trailing on the non-drive side and heads out - elbows in pulling/trailing on the drive side. When a sudden application of torque is applied, that can result in those spokes pulling the rim 1-2mm toward the left brake pad. The other spokes are going slightly slack and letting the rim "go" a little so to speak. It can get worse if your spokes have lost some of their tension over time.
Currently you have your rear at 2X, not 1X as you stated. So your crossing is fine.
As to tension - your low spoke count forces higher tension - regardless of whether the rim can handle it or not. You'll need your front 20 hole wheel tension up into the high 100's or even slightly above 110 in terms of kgf. The risk caveat though is you are going radial - you run the risk of tearing the flange. See below regarding Spoke Prep...
The rear drive side will need to be up in the 120-130 kgf range. That's what I typically find with pre-built 24 hole wheels from proprietary sources - Park has a chart that shows that tendency as well.
Some members here will suggest Spoke Prep on the threads as well....
Bottom line though is consider re-lacing the rear so that ALL pulling spokes are either ALL heads in or ALL heads out. And have your LBS wheel builder finish off with a tension meter just to be sure you're in the ballpark tension wise.
Once again, careful with the front...
ps. Some flex is frame related, nothing I can suggest for that...
09-19-12, 09:19 PM
About to board my last flight to Vegas for Interbike, back in a few hours...
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