I've just finished building a front wheel with a bulb hub and an ex721 rim but I had a bit of a problem. The same 9 spokes (36 hole) on each side were a lot slacker than the spoke it is paired with.
At first I thought that when I put the second row of spokes in on each side that i'd put the driveside spokes in the disc side and visa versa. So I stripped the wheel down and re-laced it but I had the same problem. I used a 'nipple driver' and bent the outside spokes at the elbow but it didn't make any difference.
Is this a characteristic of the front bulb hub? I've re-built a few sets of wheels before but this is the first time i've done a new build or had a problem. It would be good to know if i'm doing something wrong?
"Perfect" spoke lengths on a bulb differ slightly from 1 side to the other, I think
Is that what you mean ?
No. If you just look at one side of the wheel, the spokes cross in pairs around the wheel. One spoke out of each pair was a lot slacker than the other spoke. It looked like I had used two different spoke lengths on one side of the wheel. Both sides had the same problem.
Sorry, it's quite hard to put in to words.
Have you mixed up the spoke lengths ? (Thinking perhaps you've reached for the wrong pile when you've laced the other way after rotating the hub...)
That's assuming you've used different lengths because of the extra dish on the braking side).
To be honest I wouldn't worry, providing you get no issues when you equalize the tensions. I did a Pro2 front & couldn't get the dish spot on. The wheel has gone on to do 100's miles with no issues, & that's an exploding 29er build.
Have you mixed up the spoke lengths ? (Thinking perhaps you've reached for the wrong pile when you've laced the other way after rotating the hub...)
Thats what I thought i'd done so I stripped and re-laced it but it was the same.
Your right I shouldn't let it bother me, it is what it is. I was happy with the build in the end but it did take a lot longer. It's a good job it's not my proffesion, i'd starve!
Its not the hub or the rim. You need to back them off carefully and get back to a point where you can evenly match the tensions before finishing the wheel build.
Its nothing to do with the hub or the spoke lengths getting mixed.. its the time you have spent getting the tensions higher but also not taking note of how even they were from the beginning of the build. Early on in the build you can do this easily to a point by grabbing spokes by the thumb and forefinger to give you a rough idea of which ones definitely need tensioning.Once you reach a certain tension this will obviously become useless!
Take more time concentrating on getting the wheel true whilst matching each spoke tension as you bring the tensions higher. Once you stress the spokes in different ways you will soon find that you can overcome the problem earlier on in the build.
Grab a spoke tension meter if you can afford one.
If you like messing around with wheels and dont want to fully back them off to start again you could maybe try (one side of the wheel to begin with) backing off the higher tensioned 9 by 1/4 turn.. and increase the lower tensioned 9 by 1/4 turn. Then switch to the other side and repeat. Then check dish,stress,true,repeat etc. Not quite sure what the outcome would be like initially but at least you will know that out of the 36 spokes.. as a bunch,they would be sharing the load a lot better than the 18 that are possibly doing most of the work meantime.
See how you get on with that. You obviously know how to get it to a ridable state so if you have the time and patience you could give this a go to see if you can improve on it.
It was at the start of the build, I hadn't started adjusting the tension. All the spokes were at the same point because I had put them in with a 'nipple driver' as per the 'Wheelpro' book. The tension should have therefore been the same on all the spokes but it wasn't, for some reason 9 of the 18 on each side were a lot slacker, hence my question.
I have got a tension meter and I adjusted all the spokes to the same tension and then carried on building the wheel as normal.
I seem to remember seeing this once or twice-you've dealt with it correctly imo (tho I never bothered with a tension never)
I'm struggling to understand your problem (I'm tired).
When you say
If you just look at one side of the wheel, the spokes cross in pairs around the wheel. One spoke out of each pair was a lot slacker than the other spoke. It looked like I had used two different spoke lengths on one side of the wheel. Both sides had the same problem.
This is ringing alarm bells with me - I've built [b]a lot[/b] of wheels in my time and all of mine are 3-cross pattern. I'm thinking you may be one hole out on each "pair", meaning one of the spokes isn't having to reach as far, so irrespective of the number of turns on the nipple, if its the same amount it will be slacker than some of the others. Does that make sense?
Send a picture to my email in profile and I'll do a quick check if you like? Alternatively, send me the wheel & I'll build it for you (at modest outlay 😀 )
Wondering if you might have just crossed 2 rather than 3. When i was learning this year to build i kept doing this wrong.
hard to say without seeing though.
As I said, I'm tired - bikechain is saying same as me but in a slightly more succinct way.
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Sorry about the quality but i've only got a rubbish phone camera.
I'm as sure as I can be that i've built it correct. I did the back first and that was ok and the wheels i've done before have been ok. I've got two sets of wheels to check against, one factory built and one hand built. They are correct to the factory build but I think the hand built set have been built incorrectly.
When I lace the first 8/9 spokes (drive side) I pass the spoke through the hub from the outside, as per the Wheelpro book. When I do the next 8/9 on the disc side I site the hole to the left from the drive side. Then pass the spoke through from the outside (disc side) so that the spokes are a mirror image of each other. On the hand built set the spokes aren't a mirror of each other, the disc side spoke has been passed through the hub from the drive side.
Hopefully that makes sense, it's hard to put it in to words.
Edit : The front bulb hub has different size flanges if that makes a difference?
I can't really tell from the pics. Follow this for a standard 3 cross wheel:
1) Place the rim in your lap with the valve stem hole directly across from you. Hold the hub in the middle of the rim with it axle vertical.
2) Drop a spoke though every other hole in the upper flange of the hub. Then insert one spoke in the hole which is immediately to the left of the valve stem; this hole may be offset upward. Thread on the spoke nipple a few turns. Continue to insert one spoke in every [b][u]fourth[/u][/b] hole, threading on spoke nipples as you go.
3) Flip the wheel over and put in the next set of spokes. Each spoke should fall just to the right of the spoke on the opposite flange. Insert the spokes into the rim holes which are to the immediate right of each spoke in the first set. Thread on the spoke nipples a few turns.
At this point you should have 9 spokes per side (or 8 for 32 hole rims), loosely threaded a few turns onto the nipples, with a very floppy partial build. Next bit is important:
4) Twist the hub. Looking at your pics you need to twist the oppoosite way so the rotor side elbow-out spoke is facing forward. This makes the wheel stronger on the braking side (counteracts the braking forces). For the rear you do the same - you cannot replicate the force of braking with your legs whilst pedalling.
5)Turn it over again. Start placing the third set of spokes through the remaining holes in the upper flange; these will be pushed through the holes from the lower side. Do this ONE AT A TIME to save the other dropping out, and if you make a mistake you don't have as many to remove again.
7)Cross this third set of spokes over the 1st spoke (which is the next hub spoke hole along), over the 2nd spoke (which is the 3rd hub spoke hole along), then under the last (which is the 5th hub spoke hole along).
8) Screw this spoke into the rim at the 2nd spoke hole along from that last spoke (I'm struggling to explain this but some rims have holes that are offset which helps).
9) turn the wheel over and repeat step 8 for the 4th and last set of spokes.
This'll give you a floppy but correctly laced wheel.
It looks fine. If you were a hole out, it would have been severely wrong. Going by what you said in the first post it was obvious you finished the wheel to a point where you were happy with it. If you got the holes muddled or something.. it wouldnt have been possible to be happy with it!
I have experienced what you wrote about a lot. Winding nipples on at the thread might feel like they are all going on the same amount/number of threads going by the nipple driver but its only to wind them down to begin with. More often than not you will find at this point that every 2nd spoke will feel a world apart from its neighbour. Dont worry though.. the build has only just began!
RE: The disc side lacing choice. You have built it asymmetrically with the disc side laced the opposite to what most folk would do in their builds/factory builds. Chris King would choose your style (what you have done on the disc side in the pic) for his reasons but you will find the other way a lot more common. Dont worry.
Thanks for the replies. I think I was over thinking it and worrying about nothing as you said martinxyz.
I've just been reading up on the lacing patterns and i've done it correct to the wheelpro book. I have built it symmetrical but with the elbow out spokes facing away from the braking forces which as you have both said is not the more common approach. My factory set are the standard way but the handbuilt set I thought were wrong are in fact correct. As the hub is a shimano disc the builder has built it asymmetrical which is the way recommended by shimano(and as martinxyz said chris king).
I understand the theory of it a lot better now, i've found it quite interesting, sad I know! But as they say 'the proof is in the pudding' and i'll find out how they hold up tomorrow. Well the rear only as i've just found play in the front bearings so they need replacing.
I'd guess that it was the inner sets of spokes that were slightly loose, this would be normal if you were tightening them to a set length, as the inner spokes have a slightly shorter route to the rim(even shorter with a thicker hub flange). Once you've tightened them to a torque rather than a length it'll sort itself out and be fine.