I had constant issue with my Fulcrum 700/7 DB rear wheel spokes snapping. Always on the NDS at the nipple. So after the fourth went i decided to get a truing stand (tacx), tension meter and managed to find some cheap aero spokes (Pillars for 25p each). I then found they didn't quite fit my hub...
I then noticed that Evans Cycles offer a full rebuild with double butted sapim race spokes included for £40 - Bargin.
I now have my wheel and it is true but i thought i would check the spoke tensions as they seemed very flexible. I input these into the park tools spoke tension app:-
https://drive.google.com/file/d/1PGj76uYRJ4afhOlAW4FIuRYrTbD1MR3X/view?usp=sharing
https://drive.google.com/file/d/11FgVVGnZZYXoJOv6-ow1tyHkxU4djXFf/view?usp=sharing
All tensions were taken from right to left starting at the spoke to the right of the valve.
Surely this build is true but kinda wrong??
Can't open pics here?
Hmm, should be ok.
Note- Left is NDS with 8 x radial spokes, right is drive side with 16 three cross spokes.
They look all over the place.
If you pluck them do all the spokes on each side have the same pitch?
IANAPWB.
All tensions were taken from right to left starting at the spoke to the right of the valve.
That doesn't sound right, but your graph is way off surely.
On the left side, hole 1 is the spoke to the right of the valve going CCW.
On the right, hole 1 is to the right of the valve but now counting clockwise.
Otherwise you're not matching spoke hole pairs.
Right? Pair 1 being the space filled by the valve. The graph doesn't help of you're not seeing the wheel tension as it's built.
Two thoughts:
1) are you using the tension meter correctly? Release the handle slowly and consistently on each spoke so the needle doesn't bounce. And make sure it's as close as possible to the same place on each spoke. A drop of oil on the pivot and a bit of grease on where the spring mounts helps keep it consistent. It'll quite happily read double/half the true figure if you don't do it as consistently as possible.
2) It's a used rim, it'll be a bit bent in all directions, it'll therefore take uneven tensions to get it straight (note that at about the 2 o'clock position the drive side and none drive side are correspondingly high/low, that's an obvious bend).
It is possible to build a bad wheel that's straight with uneven spoke tension, I've done it when I built my first set of road wheels without a tension meter. But I would hope that a shop would do a better job and there's other reasons (see above) why you'd get different tensions.
TBH I wouldn't have rebuilt a rim, or paid someone to do it, it's a PITA and never works as well as you'd hope.
Ha, pics work now!
On the left side, hole 1 is the spoke to the right of the valve going CCW.
On the right, hole 1 is to the right of the valve but now counting clockwise.
This is how i measured them. So i'm not sure if one of the graphs will make more sense flipped?
Thisisnotaspoon - I did check the front wheels tension on both sides and all the spokes were spot on '25' on both sides (although, i understand the disc side should be more taught?
I've had the bike just under a year and no big collisions to the wheels so the rims should be in good condition. I think the spokes went due to tension and my weight on them. 17st limit and i am 15-16st.
Just watched the video. I need to reverse one side..
Look.. better?
https://drive.google.com/file/d/1hGUF2TpwsXdOfjmc1wXIWC5LPAMiy_aK/view?usp=sharing
On the left side, hole 1 is the spoke to the right of the valve going CCW.
On the right, hole 1 is to the right of the valve but now counting clockwise.
Sorry, misread, i went CCW on both wheels. The above graph should be correct now.
I did check the front wheels tension on both sides and all the spokes were spot on ’25’ on both sides (although, i understand the disc side should be more taught?
Spoke tension is whatever it needs to be to get the wheel centered. Assuming the flanges are either evenly spaced (unusual) or the disk side is taller, you get similar angles and therefore spoke tensions. If you went arround it and added half a turn on the disk side you would up the tension on that side, but the wheel would become dished and the disk side spokes would be at less of an angle.
Front wheels have a much easier time than rears, they get about half the weight (66/33 would be about average weight distribution) and when they ping off rocks the handlebars twitch. Conversely the back has twice the weight and when it gets knocked sideways theres nowhere to go.
If they've done a good job on the front then that suggest they were competent and then id suspect the rear is as good as its likely to get, the rim just isnt naturally straight anymore.
It'll probably still last a good while yet, just not as long as perhapse a new rim would.
25 is high, but not unusual for low spoke count factory wheels. Conversely the limit for Stans rims is about 18! Which makes rear wheels a PITA as on some hubs almost any non drive side tension means too much drive side and makes them an utter shit to get the tensions close to even.
If the wheel is true then going by the high/low tensions that overlap on the diagram that the rim is bent.
I’ve not looked at the graphs as have never used them. But I’ve built 3 sets of mtb wheels from scratch and rebuilt a 24 spoke road wheel with new spokes as I had exactly the problem as you with snapping spokes.
Imo it’s a balancing act of getting a wheel as true as possible whilst tensions are as even as possible. If the tensions per side (I wouldn’t compare side to side) of the wheel are quite different per spoke I’d try and get the tensions a little more even and accept a tiny bit less true a rim.
Unless you are on rim brakes of course (all mine are disc wheels including the road bike) where the rim being true is more important.
Just a thought - have you eased / de-stressed all the spokes yet?
I was wondering if this was a something the bike shop would have done (destressed and retensioned). With the wheel true (ish) and tensions all over the place i went on a long ride today. Around 20 miles in the wheel was all over the place and the spokes on both sides had lot tension. The radial ones had hardly any tension at all.
Luckily, i had a spoke key on me so tightened the loose ones on both sides to around the same tension, then rode another 30 miles 😛
I will get the wheel on the trueing stand tomorrow and aim to get the drive side to 22 and the disc side to around 21 (see above chat for sample tensions).
Below are the recommended tensions from a Fulcrum approved reseller.
Front Right
100-140
Front Left
90-130
Rear Right
85-130
Rear Left
100-140
If the spoke tension meter is a Park Tools / X Tools cheapie one don’t take the reading as absolutely correct. They aren’t that accurate.
Just get the spokes to where they feel quite taught by hand (compare them to another wheelset you have) - then even them all out tension wise and see how wayward the wheel true is. Then go round and tension up spokes to get the wheel true ish.
In terms of tension it’s not riding to relieve it - I found a video where you put the wheel on the floor lying down (on thick cardboard) and then bounce / stand on each pair of spokes as you go round the wheel. Then flip it and do the same on the other side. Then re-visit tensions and trueness.
Tension meters unnecessary mostly and a risk of anxiety in uninformed hands imo
Get someone who know wheels to have a look/feel.
I found a video where you put the wheel on the floor lying down (on thick cardboard) and then bounce / stand on each pair of spokes
😬 Wow! I just put on a pair of gardening gloves & squeeze a pair of spokes at a time
I’ve done the spoke bounce thing with a foot on all 3 sets of wheels I’ve built plus the rebuild one. Seems to have done the job and it makes some amazing noises.
The tension meter is a cheapie one but the tension does seem about right. The front wheel is has not been rebuilt and is the same as i got it. Every spoke both sides is 25, pretty much spot on which matches the tensions suggested for these wheels.
I think my plan was to loosn both sides a little, get the DS to a certain tension and then work on the NDS, then true.