# Bicycle Mechanics - Building Wheel with Offset Rim Question

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Fissile
04-04-08, 02:56 PM
I've built quite a few wheels over years, both motorcycle and bicycle. I actually learned on motorcycles and came "back" to bicycles. All the wheels I've built had symmetrical spoke hole drillings. Now I'm attempting to build a wheel using a rim with asymmetrical spoke holes.

Here are the particulars:

1) Velocity Synergy 700c OC rim.

2) NOS 2002 Vintage Campagnolo Veloce 9/10 rear hub.

3) 36h 3X Cross.

I used two spoke length calculators:

1) Roger Musson's "Wheelpro" Spoke Calculator

Here are the results:

Wheelpro:

Left Spoke Length -- 292.4mm Right Spoke Length -- 290.7mm

Spocalc:

Left Spoke Length -- 292.7mm Right Spoke Length -- 290.9mm

The average difference between the left and right spokes is 1.75mm.

Here is my question:

With both spoke length calculators, I entered a rim offset of zero. I went to the Velocity Rim site, but could not find any specs for the offset of the OC rims. Will the rim offset make much of a difference in spoke length calculations, and if so, how do I measure the rim hole offset?

Any help will be greatly appreciated.

alecw35
04-04-08, 03:08 PM
Build the wheel with 293 spokes throughout.
be easier.

Al1943
04-04-08, 03:25 PM
I don't know how to account for the offset rim but I do know that you should not order longer spokes. Always round down once you've determined the correct length. If the numbers you've calculated are correct then 290 for the driveside and 292 for the non-driveside. If the spokes are too long you could easily run out of threads before reaching the target tension, especially if using double butted spokes.
Have you tried the DT Swiss calculator, it's the one I trust the most.

Al

TurboTurtle
04-04-08, 04:11 PM
The offset is 4.0mm. Enter that into the spocalc spreadsheet. - TF

Bottom spec

http://www.velocityusa.com/default.asp?contentID=591

Fissile
04-04-08, 04:28 PM
The offset is 4.0mm. Enter that into the spocalc spreadsheet. - TF

Bottom spec

http://www.velocityusa.com/default.asp?contentID=591

Thank You!! That's what I was looking for.

Scooper
04-04-08, 04:31 PM
FWIW, I agree with Al1943. Round down to 292 and 290 for the reason Al1943 stated; if the spokes are even a smidgen too long, you run the risk of running out of threads before achieving the desired tension, but you can be a millimeter (or even 2) short and it won't hurt a thing. The offset will result in (very) slightly shorter spokes anyway.

dbg
04-04-08, 05:10 PM
So are there updates to the spocalc database? I have done a few Velocity Aerohead OC's, but they were listed in the spocalc database of rims (including the 4mm offset). I don't see Synergy rims in my database but it was downloaded several years ago.

Fissile
04-04-08, 05:21 PM
FWIW, I agree with Al1943. Round down to 292 and 290 for the reason Al1943 stated; if the spokes are even a smidgen too long, you run the risk of running out of threads before achieving the desired tension, but you can be a millimeter (or even 2) short and it won't hurt a thing. The offset will result in (very) slightly shorter spokes anyway.

Yup. That's how I usually do it. Better a bit too short than too long.

Fissile
04-04-08, 05:26 PM
So are there updates to the spocalc database? I have done a few Velocity Aerohead OC's, but they were listed in the spocalc database of rims (including the 4mm offset). I don't see Synergy rims in my database but it was downloaded several years ago.

I downloaded it this morning, and there is no listing for the synergy rim in the db.