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#46
01-22-2017, 01:24 AM
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Finally got around to fixing the Alpha 340 rear wheel. I never previously checked the tension, the DS tension was literally off the charts for the TM-1 tool. All averaged 19-20 on my TM-1, the Park chart stops at 17 at 163 KGF. I can't imagine I am reading this right, but the Sapim site puts CXrays as .9 X 2.2 so unless I was reading this wrong the DS spoke tension was crazy high. So I de-tensioned the wheel and started again, and I wanted to try wheel building tip #6 from Wheel Fanatyk site anyway before I build my next set of CX/Commuter wheels. It came together fairly easy, although I imagine the real test will be whenever they get back on the bike and see if they hold true or I snap another spoke.
The tension chart is attached, tension went a bit higher than I wanted again but still much lower than before on the DS. The broken spoke was #22 on the attachment. 
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#49
01-22-2017, 01:42 PM
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Quote:
Thanks, I hope it remains straight while on the bike. I didn't see any cracks, but the tension was so high I can't imagine it didn't damage anything. Tony, Thanks, I will have to improve my search function. I checked a few sites, but could only find people mentioning the stock sizing. Sent from my iPhone using Tapatalk
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#50
01-22-2017, 01:53 PM
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"Sapim publishes the CX-Ray thickness as 0.9mm. Many would admit this is often 0.95mm. Such variation is within normal spec but wreaks havoc on tensiometer accuracy." — http://www.wheelfanatyk.com/blog/tension-inaccuracy/So, since you said you "went a bit higher than I wanted" with .90mm, if the spokes are actually .95mm then you are really closer to your target tension then you thought. (I measured about 20 CX-Rays and measured mostly @ .95, some a mm or so thinner but none at .90) Also the TM-1 is reported to read a bit high (10% higher for my wheelset when compared to the wheelfanaytk tensiometer — and the wheelfanaytk tool only has an accuracy of +- 10%). As weisan said, your wheels look solid. Last edited by Tony T; 01-22-2017 at 02:14 PM.
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#51
01-22-2017, 03:47 PM
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Highly appreciate the info, definitely makes me feel more comfortable with the tension. Thanks again. Sent from my iPhone using Tapatalk
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#52
08-22-2017, 08:08 AM
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Quick follow up to the Stan's A340 rear wheel, I only recently put the wheels back on the bike. They only made it two rides and my rear tube blew out. Didn't puncture, it literally blew the drive side bead off the side of the rim. It looks like the rim strip shifted or folded over after I installed the tire, maybe scraped the tube and blew it.
After I stopped I realized the rim lost true again. One spoke lost all tension and would barely go through the brakes, must have happened when the tube blew since I was at the end of my ride. Any ideas on what could have happened? Or what would have caused the rim to bend after the tube blowing?
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#53
08-22-2017, 08:58 AM
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Not really able to help much. I'll say that now having built around 12 sets of wheels over the last few years (using a DT Swiss meter), I won't mess around with anything below 28 spokes (now I'm 6'3" and weigh 220 so nor will I ride anything with low spoke count except factory wheels such as a Campy). It seems that my miscalculations have been within acceptable limits, I've only had one wheel that I needed to significantly retrue and tension and it was from my very my first pair after a year of commuting in Boston. That said, with low spokes I imagine that each spoke is working significantly harder and user error is magnified.
Not saying you won't get it eventually, but it seems that getting the science down on higher spoke count wheels will eventually get you to building strong and reliable low count wheels. I trust my 32 spoke builds on my bikes (road, gravel and MTB), my wife's bikes, and my brother-in-law's bike, and he's bigger than me, lives hours away, and can't even change a tube and (knock on wood) all seems stable.
__________________
Friends don't let friends ride junk!
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#54
08-22-2017, 02:39 PM
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The next set of wheels that I am putting together are 28/28, so definitely going with a higher spoke count for these. Although I am only 150 pounds, so not quite sure I need the extra spokes. However, the one set of 20/24 that I put together are still riding solid. It seems to be only this rear wheel that I bought used and had to re-tension previously on this thread.
Sent from my iPhone using Tapatalk
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#55
08-22-2017, 04:07 PM
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What many people seem to miss is that selection of the number of spokes isn't a single variable decision. You can't just say, "I weigh X, therefore the number of spokes I need is Y." Other factors need to be considered.
First and foremost, what has to be understood is that only a few spokes in a wheel are actually bearing the wheel load at any given moment. Which is okay, as each spoke is quite strong - but you still need a more than one spoke to bear the largest loads. What determines how many spokes actually bear the load? Primarily, it is the rim stiffness. Loads are passed from the ground contact to the rim over a small area, which concentrates loading to the spokes near that area. But if the rim is very stiff, it can act to distribute loads to spokes that are further from the ground contact point. And the more spokes bearing a load, the lower the load concentration on each individual spoke (and the more durable the wheel). What makes a rim stiff? partially it is the cross sectional area, but a bigger factor is the rim shape - the deeper and wider the rim, the stiffer it will be (this is similar to frame tubes, where diameter plays a large factor in tube stiffness). A flexy rim will not be able to transfer loads very far from the ground contact area, so for strength/durability, the spokes need to be closer together to ensure enough spokes are sharing the load. This means more total spokes. A stiff rim can transfer loads a longer distance from the ground contact area, so the spokes can be further apart - in other words, fewer spokes. So, the upshot is that a shallow, lightweight rim will require more spokes for the same strength/durability than a deeper, heavier rim. A 15mm deep 280 gram rim may need 36 spokes for any kind of durability (and even then, it won't be all that durability), whereas 30 mm deep 560 gram rim may be so stiff that it can work reliably with 18 spokes. There are other factors too, which play a factor in selecting the number of spokes - in particular, the flange offsets, spoke thicknesses, and wheel diameter. But the number one factor will be rim stiffness.
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#56
09-28-2018, 06:54 AM
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Long term follow up on an old thread.
The Stan's Alpha 340 rear wheel will not maintain true, I've completely de-tensioned and re-trued it about 3-4 times. I believe the rim is damaged. I stopped riding the wheels a couple of months back, but want to rebuild the rear. I am not impressed with the Stan's Alpha 340 rim and would like to re-use the spokes if possible. The only rim I could find with the same ERD (592) was the HED Belgium. I know I should measure the rim first, but worth the risk and worse case scenario I have to buy new spokes. Anyone know of another rim that measures 592? Or should I just stick with the Belgium?
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#57
09-28-2018, 07:06 AM
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Some rims are close to 592, Velocity Quill, H+Son Archtype, DT460 but not 592. Belgium great(but expensive) rim. This guy for spokes or me for black or silver Sapim Race.. marcus@yojimbosgarage.com
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Chisholm's Custom Wheels Qui Si Parla Campagnolo
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#59
09-28-2018, 08:02 AM
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Thanks,
The H-Plus Sons are tempting, especially the price. It may even be cheaper to use that rim and purchase new spokes. I'll have to check the cost of both and go with either the Belgium or Sons. thanks.
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#60
09-28-2018, 08:03 AM
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Quote:
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Chisholm's Custom Wheels Qui Si Parla Campagnolo
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