Hot answers tagged

11

A wheel could theoretically be trued by tension alone if you started with a perfectly manufactured rim, hub, spokes and nipples and you were building a perfectly symmetric wheel. The reality is that there are minute differences and that tolerances are not all that tight. Not to mention that ultimately the wheel has to go into a frame that also may not be ...


10

If the tension is too high, the drivetrain will bind. If it is too low, the chain will drop (which is dangerous on a fixie, since it can catch and lock up the rear wheel relatively easily). You basically want the highest tension such that the drivetrain doesn't bind. See Sheldon Brown on how to set chain tension properly.


10

The grooves/enlargement shown at the hub are all normal. The path to a wheel that doesn't break spokes is use premium quality spokes (DT, Sapim, and Wheelsmith are the usual poster children), set their line properly at the rim and hub, and stress relieve them properly during building. Fatigue breakages are almost universally the result of one or more of ...


9

They look like you want those "in" the horizontal dropout. The bracket should cover the frame and as you tighten the bolt it will pull the axle further away from the cranks, tightening the chain along with it. Be careful to not over tighten as you want a little 'slack' in the chain. Also, it is very easy to tighten one side more than the other resulting in ...


8

Another common cause for spoke breakage at the J bend is low spoke tension, or preload. As you ride, the bike momentarily "hangs" from the topmost spokes on the rim. Because its a dynamic changing system, this load hands off to the next spokes around quickly. So every wheel revolution, a spoke is pulled tighter and then relaxed. If the spoke is ...


7

Looks a little tight. There should be +/- 0.5 inch vertical movement of the chain possible halfway between the sprockets. Park tool has a great video on single speed chain replacement: (link starts the video at the tensioning segment.) Readjust tension and see if it makes a difference. Also make sure the wheel is parallel ...


7

The rim manufacturer should have this information. It depends a lot on the number of spokes, if the holes have eyelets (metal grommets) and the material of the rim. Lower spoke count wheels need more tension. Generally eyeleted wheels can handle more tension. As for symmetrical tension, that also depends. If the wheel is asymmetrical then your tension ...


7

The side with the disc is dished in more than the other (that is, the spoke flange is closer to the hub's centerline), so yes, I would expect it to have higher tension.


7

Kilograms force. It is tension equal to a weight of that many kilograms pulling on the spoke under earth gravity.


6

You started with too much slack for the barrel adjuster(s) to take up. Note you have one on your derailer and one on your shifter, and they both do exactly the same thing, so maybe by using both you'll have enough adjustability, or maybe not. It doesn't matter because you don't really want to be maxing them out anyway. You need to re-anchor the cable in a ...


6

As you noticed the derailer moves when you push at the arrow. That is the spot where the rear cable housing sits. In the photo below the rear cable housing is the black loop that runs from the bracket on the chain stay just forward of the dropout to the barrel adjuster on the back of the derailer. The housing is flexible, but it doesn't compress (much), as ...


6

I believe DT has a blanket recommendation of 1200Nm for all their rims, or 122 kg-f. You could email them to corroborate but that number should be safe. Use the tensiometer chart for the thin section of your spokes. By the same token, always position the tensiometer such that you're isolating a thin segment for measurement. If you had any of the thick ...


6

The left to right side tension numbers you have are thoroughly normal. 70%-ish is where a lot of disc wheels land. Once you're actually building the wheel, as opposed to planning it, you're only looking at the more tensioned side to see how close you are to your target tension. The other side falls where it falls. Since you're within the recommended range ...


6

I will focus on the chain tension part of the answer, as your big chainring is clearly worn out. However, do note that increasing the derailleur spring tension wouldn’t stop the chain skipping on the worn chainring. Therefore, this answer is mainly for the sake of interest. By chain tension, I believe you actually mean the tension in the rear derailleur ...


6

I suspect the symptom of slipping could be mitigated for a while by increasing chain tension, but it would only be a short-term fix. Here's a trace of one of your photos highlighting the teeth. See how the grannie ring has nice fat teeth, with a pronounced width and a curve over the top of each tooth? This ring has seen little use and is perfectly ...


5

"Chain binding" occurs when the chain is really tight around the sprockets. No set of sprockets is perfectly round and centered (especially if worn a bit), and if the chain is tight at one spot in the rotation it likely will become too tight with another half-turn or so. The pressure of the chain on the sprockets makes the crank more difficult to turn, or, ...


5

If you fasten the cable anchor with the quick release at its "tight" position and then it's able to slip into a "loose" position, that sounds like a likely culprit to me. I haven't encountered a misbehaving BR-5800 QR yet so I don't actually know what to tell you there, but I think either the silver part in front comes off and is covering a bolt head that ...


5

Chain tension is set by the springs in the derailleur. Some derailleur models have a tension adjustment in the upper B-pivot, but I think this is to adjust the range B-screw rather than change the overall force the derailleur puts on the chain.


4

Given the age of the wheel, you're going to continue to snap older spokes from time to time. Don't worry about the gauge of the replacement spoke. Assuming it's within the range of appropriate tension, as long as it pulls true there's not much to be concerned about. I have multiple wheels with some of the thinnest gauge spokes available (Sapim CX Rays) with ...


4

I'll note even some potential problem causes that might sound stupid, but in my experience, even a quaified mechanic can sometimes make a mistake, and not take something trivial into consideration, so not wanting to insult anyone's intelligence by stating some "stupid", or "I obviously checked that" potential problems, it is what it is: a simple ...


4

The photos show that the contact surfaces of the cogs have been worn to match the old chain. The new chain does not match them perfectly, which is the reason to the noise. For some reason singlespeed seems to be much more sensitive than derailleur cogs. The good news is that if you can tolerate the noise and vibration for a while, the new chain and old ...


4

Yes, overly tight chain does accelerate wear on other parts of the drivetrain. The rear hub bearings are not designed to work under the load described here and if ridden like that for extended periods, it will likely show significant wear. Chain wear would (and will) cause your chain to gain that desired slack again, but I wouldn't rely on it happening soon ...


4

The hub holes are elongated a little bit but I would not be concerned. It seems to me a pretty typical amount of deformation. I would reuse the hub but I would re-lace the hub with the same pattern. It's hard to say why the spokes failed but unless it happens repeatedly I would chalk it up to poor quality or defective spokes, or spokes that got unevenly ...


4

Yes, it's normal and you correctly understand why. Some straight pull hubs can create more variance in bracing angle per side than a j-bend hub would. Other straight-pull designs (Velomax/Easton comes to mind) put the spokes in a straight line, creating the least of this variance possible. On a j-bend hub, there is also some amount of this effect. But, it's ...


3

The chain was not straight: wrong rear wheel hub size for my frame! By calculating the chainline of my crankset and the rear frame dropout I noticed it was off by 5 mm. My frame has a weird 126mm dropout so I had to add some spacers/washers to my 120mm rear wheel so that the chainline was off by 2 mm


3

In short no. I actually took a true wheel that I had built and carefully equalized all the spokes on each side with a spoke meter. This actually put the wheel slightly out of true. Rims, spoke nipple rim interactions, hubs, etc., are all imperfect. How you place the tension meter on the spoke will be imperfect. All of these little errors can add up to ...


3

Over-tensionning the chain is never a good idea. Except maybe for the unscrupulous mechanic who will be the first to make some profit. It puts a lot of strain on the chain and mainly on the bearings.The system should have enough slack. And since chains have tolerances, slack should be tested with the chain at different positions. I can only advise you to ...


3

Yes, it’s normal for spoke tension to decrease when the tire is inflated. First of all I’d use much more tension and try to get it more even. Currently you have about 30% difference between slackest and tautest spoke, which is a lot (I’d aim for ~10%, but I’m a perfectionist in that regard). 540N on the slackest rear spoke before you’ve even inflated the ...


3

What you describe suggests friction in the rear housing loop. It fits with the problem getting progressively worse, and with the apparently slack cable, presumably along the downtube or chainstay. This can happen from corrosion, contamination, kinks in the cable/housing, or the housing or cable fraying or coming apart. It might need new cable and housing. ...


2

The problem was with the cable/housing. I would probably pinpoint the source as the housing which goes from the frame to the caliper. I could probably have done a cheaper fix by replacing just the last cable housing, but I have replaced all the cable and all the housings of the rear brake. It is working smoothly now.


Only top voted, non community-wiki answers of a minimum length are eligible