BeeRich

Hi folks. Just wondering how to properly tension a replaced spoke while on tour.

I have a cyclocross bike that was repurposed by MEC (mec.ca) as a touring bike. Love the thing. Anyway, it has disc brakes, which means braking tension for my tank is put upon the hub, not the rim. So rim gets yanked on when braking, which turns into high tension on spokes, and hence breaking of said spokes.

At least that's my theory.

I have to replace broken spokes on the run, when I have time. I don't have enough space for any tension tester of any size (the tank is heavy enough without specialized tools), so I was thinking someone might know how to test the spoke tensions while on the run.

Also, how to best optimize spokes while on the run, as I want to avoid the odd tight or loose spoke so I don't get any breaking at all. This is a tough one as I know little about wheels.

Cheers. Enjoy the pics.

My fix-it kit, on a ferry from St. Malo, France, to Portsmouth, England.


The path from Bordeaux to Carcans and the west coast of France. Nice playground.


MEC 2011 Cote touring bike. It's an aluminum cyclocross bike with braze-ons. I replaced the handlebars with proper touring round bars. Also replaced toe clips.


The small number of spokes I've had break on me, did so at the nipple here. Smells like a tension problem.

cyccommute 

First, if your spokes are breaking at the nipple, the problem is that the spokes are too short. I’ve been seeing this problem on a number of bikes with OEM wheels, especially if the wheels have aluminum nipples. They aren’t making the wheels with the proper spoke length so the threads aren’t buried in the nipple. They only go down about 1/2 way. That stresses the spoke at the nipple and makes it prone to breakage. Adjusting the tension won’t fix anything. The only thing to fix the problem is to rebuild the wheel with the proper spokes.

As for tensioning a replacement spoke, learn how to do it by ear or by feel. If the spoke is feels like it is about the same tension as the spoke around it (and the wheel is true), the tension is close enough. You can also hit spokes around the replacement...a spoke wrench makes a handy mallet...and listen to the sound. If it doesn’t sound the same, tighten or loosen to get the same tone.

Tension meters are good and all but you carry a pretty good one around with you all the time.

BeeRich

Wow that's probably the last thing I would want to be hearing. Heh. Is thing something I could do on my own? Is this recommended? So many questions. If I had the right tensioner and knew what size spokes I should have, is this something I should undertake? I'm guessing doing these one by one is the approach.

I guess my first question is how do I know how to measure proper spoke lengths?

Cheers

JohnDThompson 

The easy way is to use one of the on-line spoke length calculators, or download the spocalc.xls spreadsheet, find your hub and rim in the database, decide on a cross pattern, and let the software do the math.

Failing that, a little algebra and trigonometry and a few measurements to plug into the formula:


Source: Sutherland's 4th Edition

Bill Kapaun

IF replacing ONE spoke, you's simply bring the tension up to get the wheel true again.
That assumes it was true before you broke the spoke.

If you are constantly breaking spokes, they are at the end of their life. ALL the old spokes have the same number of fatigue cycles.

BeeRich

Oh screw that. LOL. Is that in metric? There are no units.

BeeRich

Ya one spoke at a time.

dsbrantjr

Units? Trig don't need no steeking units!

BeeRich

Hub width does.

BeeRich

Ah I guess if all measurements are same units...I quickly skimmed over the formula. Ya I might talk to a local wheel builder about doing this.

dsbrantjr

Yes, the thread valleys make nice stress risers. The threads are rolled into the spokes and I'll bet they have all broken right at the point where the first thread reaches full depth

BeeRich

They all seemed to break right at the nipple, as per the images in the OP.

fietsbob

My Touring bike build, I built a 48 spoke rear and a 40 spoke front, 10 years 3 long tours , only 1 spoke spare needed..

I just bought 2 more spokes in the 3 lengths of the wheels built..

If they break at the nipple they may be too short ( head un supported by the spoke in the center )





....

2old

Ear, feel, and most important (for me) straight wheel.

berner

The gentlemen posting above offer good advice. Regarding spoke tension read up on tuning by ear in an article from Harris Cyclery. There is a wealth of knowledge at the website so it is worth while spending time there and reading up on subjects of interest. I tune by ear with very good results. With a bit of practice, perhaps even using a pitch pipe if no other spokes present for comparison you will will get good results also. https://www.sheldonbrown.com/spoke-pitch.html Mr. Brown built a well regarded website for cyclists. He is no longer riding with us and is missed even by those who never met him.

CliffordK

I think it depends a bit on how long your tour is.

I'm generally not out for more than a week or so so at a time.

I've done roadside spoke replacement, or even trued a wheel one spoke short in a pinch.

Finish the ride, then deal with the big issues when one gets back home. Truing a 36 spoke wheel with 35 spokes was easy enough, but a major hassle to get back to normal.

It is easy enough to true the wheel on the bike.

I don't know, if you're out for more than a week. I suppose if one had a layover day, one could do a complete teardown and rebuild.

BeeRich

Hah ya I don't doubt it. I just didn't want this to turn into a wheel rebuild. I current tune by ear, as that's all I got on the road. I've been on Sheldon's site many times before. Thanks for the post.

BeeRich

Tour can be up to 75 days. Truing is one thing, but then I'm nervous about the weight and load on a rim missing a single (or two) spokes. I've never done a rebuild and I wouldn't want to do that on a tour. At least not now.

BeeRich

Just in case someone's interested, these are from my notes:

• Left (front & rear): 15G*292L (1.8mm)
• Right (front & rear): 15G*290L (1.8mm)
• DT Champion Stainless Black (brass nipples)
  

headasunder

Save your self the pain and get the wheels rebuilt with double or triple butted spokes for a 2/3 month loaded tour your rig is too light weight + broken spokes are a pain on a loaded rig when you are miles from anywhere and as you have found out once one goes another will follow its just the when you don't know.

BeeRich

OK, sounds good. You recommend 2.0mm spokes plus triple butted?

Gresp15C

It can be in any units, so long as you use the same units for each symbol. For instance, measure everything in mm, and your spoke lengths will come out in mm.

I've used this formula with success for building wheels.

davidad

Spokes that are tensioned properly can last through many rims.

davidad

This is a sign that the tension was too low. I would go with double butted spokes to minimize any problems.
Are you running 32 or 36 spokes? 36 is the minimum for a loaded tourer.

BeeRich

I don't know. I just bought the bike as it was sold as a touring bike. It's upside down in my garage. I will have to think about all this.