Mc2

I have new Campagnolo Record hubs and old Mavic Monthelery tubular (sewup) rims. I worked through the spoke length calculation shown at Park Tools, but my spokes seem to be 2 or 3 mm (or more?) too short to properly do a 3 cross, 32 hole lace up. Do tubular rims require longer spokes? Do the nipples seat that different than clinchers?

79pmooney

Tubular rims. all else being equal, are shallower so yes, the spokes ore typically longer but a solid ERD measurement should take that into account. Did you do your own ERD check? I don't have any faith in the printed numbers. I also run the check both from valve to seam (vertically) and at right angles (horizontally) to take into account any "egg-shaping" in the rim. I averaged the two numbers.

3X 32 spokes with Monthelery rims and low flange hubs should be around 302 mm for front and left rear and 300 right rear if those Monthelery rims have similar depths to the old, shallow GP4s; (I heard they are shiny GP4s.) The newer GP4s made from a "U" extrusion and a arced "cap" are deeper and require spokes 2 mm shorter. (I just finished building 2 sets of GP4 wheels, one old and one new, Those numbers are solidly planted in my brain.)

A hands on ERD reading will account for nipple seat. I never measure from anywhere on the rim. Just use the spoke lengths and the distance between J-bends. So, whether the nipples sit differently? Who cares?

Andrew R Stewart 

How did you determine the rim's ERD? Back when i was riding Monthelerys we used the charts in our Sutherlands Manual. As I recall these charts often placed the spoke end at the rim bed's surface. Not where in the spoke nipple you expect to see it. These days I just measure the ERD directly and in at least 3 locations around the rim and use the average.

While there were sew up rims with very specific nipple seating these were usually the filled ones like the foam filled Ukai (as was OEM on my first two Fuji Finests). The Monthelerys were made offered with or without double nipple hole reinforcing eyelets. At around 400ish grams these rims were on the edge of not needing nipple washers. But this was pretty much the common way back then. Many rim makers offered a common rim in a new bike spec (as low cost as possible) and an aftermarket/upscale version (eyeletted, anodized) based on the same extrusions.

What can and does come into the lacing up is are the spoke holes offset to each other and which way does this happen at the valve hole as the point of reference. If the hub has spoke bedding wear and you want to mimic that with the new spokes but the rim has the opposite nipple hole off set the spokes will cross over the valve hole. When the hub has a wear pattern in it I follow that as my first priority and would live with the valve access as the hub determined.

But the nipple will seat in the rim's nipple hole just like any other rim with the same nipple bed treatment. The Fiamme, Rigida, Weineman, Nisi, Araya, Ukai (foam filled excluded), Mavic and other brands all had the same spoke/nipple/rim design as your Monthelerys. Andy

Kontact 

How are you measuring 2-3mm too short? Is the wheel built?

oldbobcat

Here's a suggestion for measuring ERD accurately. Thread a nipple onto an old spoke and cut the spoke off 2-3 inches above the nipple. Now the nipple is your rim depth gauge and the clipped spoke is the handle. Insert the nipple into the spoke hole, with nipple washer if necessary, and mark where the nipple protrudes from the inside of the rim. Remove gauge and measure from the mark to the butt portion of the nipple. Add twice this measurement to the inside diameter of the rim for an accurate ERD.

79pmooney

Or - insert two spokes into opposite (spoke number divisible by 8) or almost opposite holes (not divisible by 8). Thread nipples onto the spokes. I thread the nipples down to just below the nipple top but above the screwdriver slot. Now, pull the spokes together and wrap a rubber band around the J-bends. Measure from inside of elbow of one spoke to the same on the other. (The same points you measure spoke length from. I bet Park or DT has a diagram spelling that out.) Now simply add the two spoke lengths and your measured distance. ERD. That simple. No cutting. Nothing wasted. I do this in two directions and take the average. Andy above uses three directions. (Rims may be a little egg shaped but pull easily to round.)

Advantage of this method is that it reflects where you want the spoke end to be in relation to the nipple top. (The spoke will stretch perhaps a mm depending on both tension and spoke diameter.) I want room on both sides of my target so with variations in spoke length, hub flanges, rim seats ... I do not run out of threads or have a spoke below the nipple head. Yes, I have run out of threads and simply forced the nipples another turn or so but mickey mouse and not doing the next person who needs to true the wheel any favors. Too short = nipple busters. And an excellent chance that nipple top will be lost forever inside that rim to bug someone for years if the rim does not have ferrules.

Oh, and the math is really easy!

grumpus

Did you use the internal rim diameter rather than the "effective rim diameter" so failing to add the thickness of the rim?

FBinNY 

This brings up anissue I've had and posted (ranted?) about here for years.

The math in spoke calculators is pretty standard, but there's a question about the ERD dimension used, and how it's factored.

Some people measure ERD to the nipple seat, others to where they hope the spokes end, ie. shy of the nipple,'s top.

That makes for 3mm difference.

I NEVER use a published ERD spec. I measure ERD as follows.

1. overall rim diameter to outer edge, measured in 3 directions and averaged.

2. drop a nipple into the hole and use a depth gauge to measure to the top.

3. subtract twice the depth, plus 2mm from the rim diameter to get my ERD for spokes ending 1mm shy of the nipple's top.

Then I use a calculator that reliably has spokes end exactly at my entered ERD.

SurferRosa

Will Sapim 18mm nipples correct your erd error?

Kontact 

Making the nipples longer will not prevent their heads from breaking off.