mosef45

Hey guys,

Sorry for the long post but I thought the detail was important.

So I'm building my first set of wheels using Sun Rim CR 18s (27”) and two old French Maillard hubs for my vintage Peugeot P-9. I went to my LBS and they measured the spokes and gave me 302mm (front wheel), 298mm (drive side) & 300mm (Non Drive Side) spokes. I own a truing wheel and a centering gauge and I'm doing a 36 hole, 3 cross. I followed the wisdom of Sheldon Brown and Roger Musson and after the initial lacing of the front wheel tightened the nipples until the threads just disappeared. The spokes were still loose at this point, very easy to squeeze with my hand. I then worked from the valve turning each nipple one full turn and then repeated once more. After this I put the wheel in the truing wheel and with some patience was able to get the wheel in nice shape for a novice.

This was not the case with the rear wheel. After the initial lacing of the wheel I found extreme disparity in spoke tension on both the drive and non-drive side; some so high that I could not tighten the nipples equally making the spoke thread disappear as I did the front. Some spokes were only laced about 1/4 on their thread and were already much tighter than spokes on the same side of the hub whose nipples were laced to the end of the thread. I took the wheel apart, re-laced, and had the same issue. I then decided to measure all the spokes. Turns out when I measured the spokes using my park ruler the lengths were 297 (DS) and 299 (NDS).

I then did some research and from what I found 1mm in spoke length is forgivable. I then thought possibly the mechanic at the bike shop made an error in calculation. I decided to take the measurements myself. Instead of using the ERD on the sun rims website I measured it using the 200mm spoke method by Musson and found the ERD to be 622 not 620. When I redid the calculations using the new ERD my spoke length was 299 (DS) and 301mm (NDS)… 2 full millimeters off. I know that once the rear wheel is properly dished the drive side spokes will have a higher tension than the non-drive side but at the initial point of lacing I wasn’t sure this is the case.

So I’m wondering if anyone has had the same situation happen to them. Wrong ERD on manufacture website?

Also if 2mm in spoke length is enough to get the results I’m having.

And any other additional suggestions or recommendation or observations would be helpful. I’ve been working on these wheels for a while now and would love to get on the road.

Thanks!

mrrabbit 

Manufacturers published ERD's engender the following problems:

1. Typically they don't provide a reference for their number: Where were they aiming in regards to the ends of the spokes in a given nipple?

On my spreadsheet, I'll report something like: "584" "~" "Flat of 12mm"

In other words, 584mm as-is when aiming for the screwdriver flat of a standard profile 12mm nipple.

This way you can either use what I provide - because you are doing the same - or adjust to suit YOUR preferences for what YOU are working with.

2. Rim productions fluctuate...Mavic Open Pros can be had as low as 600mm and as high as 604mm when using the same measuring reference.

Sun MTX33 26" when measured floats between 532mm and 534mm. And the label says, "536mm".

This is why wheel builders here and elsewhere always say: "It's best to measure your own ERD's." It keeps you out of trouble...

=8-)

mrrabbit 

Turn your NDS spokes into drive side spokes. Order more for the NEW NDS measurement you arrived at.

=8-)

Kimmo 

Sounds like a common lacing error. Try re-lacing one side another hole along in the hub.

mrrabbit 

...worth considering.

=8-)

Retro Grouch 

The cause of the problem you are experiencing isn't spoke length. If it were, all of the spokes on either the drive side or non-drive side would b e either too long or too short.

My guess is your wheel had a pattern of 2 short spokes followed by 2 long spokes all the way around. That's fairly common. What it means is that the two sides of the wheel are off by one hub hole relative to the other side.

mosef45

So I re-laced and attached pics. As far as I can tell the lacing for a 3 cross 36 hole is right. Also there is a pic of the protruding spokes. Turns out every protruding spoke on the DS is a Key spoke and on the NDS is a leading spoke if that info is helpful to anyone. Does that ring a bell to anyone? Retro Grouch I haven't tried your theory yet.

cny-bikeman

Go back to this part of Sheldon's instructions. You did not correctly place the first spoke on the opposite flange, so every other one on that flange is wrong as well.

The second group
"Now turn the wheel over and examine the hub. The holes on the left flange do not line up with the holes on the right flange, but halfway between them. If you have trouble seeing this, slide a spoke in from the left flange parallel to the axle, and you will see how it winds up bumping against the right flange between two spoke holes. Turn the wheel so that the valve hole is at the top of the wheel. Since you are now looking at the wheel from the non-freewheel side, the key spoke will be to the left of the valve hole.

If the key spoke is next to the valve hole, insert a spoke into the left flange so that it lines up just to the left of where the key spoke comes out of the hub, and run it to the hole in the rim that is just to the left of the key spoke."

ksisler

All -

Thanks...after building a number wheels successful now and then for 30+ years (mostly by carefully cloning good wheels I trust on another bike) I have now learned several new and useful things from this thread. Much appreciated.

/K

mosef45

cny-bikeman thanks! You were right. The first spoke in the opposite flange was incorrectly placed. After relacing the nipples sit completely in the rim. Many many thanks!

mrrabbit 

Yay!

=8-)

Kimmo 

*cough*

I was right first...

mrrabbit 

Wasn't aware that BF was a competition to be first...I thought that was the old FC website...

=8-)

cny-bikeman

Yes you did, but sometimes it takes saying something in a different way to make sense to the OP, and one often cannot tell ahead of time what will work best.

Kimmo 

Bah, OP owes me a gold star, dammit

mrrabbit 

All you get is what you deserve on BF:

$postcount = $postcount + 1;

It's called being humble!



=8-)

reddog3

If I were you Kimmo I'd call Al Gore and complain. After all, he invented the internet.

mrrabbit 

He would just give him a hockey stick.

=8-)

cny-bikeman

...by unauthorized proxy

mrrabbit 

Um...that's bronze, not gold!

=8-)

Cross Creek

Whenever I haven't built a wheel in some time, on the first of the pair I always seem to mis-position the spokes and have the same problem (which is at least easy to diagnose and correct once you've ever done it). Practice may make perfect, but gaps in practice definitely do not!

cny-bikeman

Well the original name of the file is gold-star, and I think you'd have to agree that the pic below it is "gold," and besides, it's not your star!