Bicycle Mechanics - First Time Wheel Building - Need help with spoke length calculation

Hey guys..

I'd like to try my first crack at wheel building. I'm ok with the lacing, truing, dishing, etc, but the spoke length calculation is sort of concerning me.

I've gone over several sites showing how to measure the hub to get the various dimenions required for the spoke length formula, and I'm sure once I pick up a cheap caliper, I could probably pull it off.

The thing is.. I want to build this wheel with some heavy duty DT Swiss Alpine III spokes, and if I get the measurement wrong I could end up wasting a chunk of change on the spokes.

I have the factory measurements for the rim's ERD (Sun Rim Rhyno Lite), but unfortunately I can't seem to find the measurements for the hub.

It's a Shimano FH-M475 (pulled off of the stock rear wheel of the 2007 KHS Alite 3000).

Both the rim and hub are just spare parts I have kicking around.

I'm not sure if any of you pro mechs have access to any info that's not available to the public.. if anyone could tell me the proper measurements for this hub to calculate spoke length, I'd appreciate it.

You don't absolutely need calipers - a ruler with metric scale is sufficient. Measure from spoke hole to flat side of hub locknut. Then add 1/2 of whatever size the locknut is (what size wrench fits it). Finally double the result. Ex: spoke hole to locknut 30mm, locknut 17mm. (30+8.5)*2 = 77mm. Awkward but effective and accurate. Alternatively you can use a compass or any tool that can accurately span the distance between the opposite spoke holes.

I want to build this wheel with some heavy duty DT Swiss Alpine III spokes, and if I get the measurement wrong I could end up wasting a chunk of change on the spokes.

That being the case, you'll need hubs with 2.5mm spoke holes.

Thanks guys.

You'd think that this sort of data could be obtained from the manufacturer (Shimano). Can't seem to find the numbers anywhere.

I have had very bad experiences with M475 hubs, especially the rear. I have never had one of the freehubs last beyond 700 miles. I would not build a wheel with one.

Yeah... Im not wild about the hub either.

Hmmmrph..

Looks like PricePoint has a Rhyno Lite / XT Hub wheelset on for rather cheap (probably cheaper than what I would end up paying for the XT hub alone from an LBS).


BTW: Do you build wheels? Or is just from your personal experience with the M475? How many have you had?

My Lbs just put the model of hub and rim into the computer program with # of cross for build and it tells you what you need. Most shops must have this I would think.

Yeah, I guess I was sort of hoping one of you old salt mechs would do exactly that for me.

And no, my lbs doesn't have such a system. In fact, the last time I had to buy spokes from them, the mech kinda shrugged, handed me a spoke and said 'That should do it... check it out for yourself.'

Never again...

I used Spocalc from Sheldon's site for my first ever wheel build. Also http://www.dtswiss.com/ click on the spoke calculator link and use it as a guest. That's where I double checked my numbers before I ordered spokes. I just built the wheel and had no problems.

Both have listings of rims and hubs with their measurements already programmed. Maybe yours is listed.

Unfortunately, my hub is not on the DT list.. but I think I'm ok with the measuring now. I'll give it a crack tomorrow.

Sorry, I have too many threads on this.. forgive my spamming, but I'll cut and paste a question from the other...


Silly question.

From what I've gathered.. there can often be a need to use 2 different lengths for the left and right side spokes.

If the spoke length calculations turn out to say you need 260 on one side, and 261 on the other, is it cool just use one length for both sides? Is there a threshhold measurement difference between left and right that can allow one to use one length of spoke? 1 mm? 2 mm?

Yeah... Im not wild about the hub either.

Hmmmrph..

Looks like PricePoint has a Rhyno Lite / XT Hub wheelset on for rather cheap (probably cheaper than what I would end up paying for the XT hub alone from an LBS).


BTW: Do you build wheels? Or is just from your personal experience with the M475? How many have you had?

I do build. But also I have had personal experiences with two rear wheels with M475, and both had multiple problems with freehubs. I ended up junking the wheels and building my own. I use XT 6-bolt disc hubs which I have never had a problem with. By the way, the M475 is very common on LBS-bought complete bikes.
The XT hub with Rhyno Lite is an excellent combination, if properly tensioned. The XT hubs are not very expensive if you get them online.

Apple iPod, iPhone, iPad and Android version of the spoke calculator http://www.iforsw.com

http://www.mrrabbit.net/wheelsbyflemingapplications.php

Grab the spreadsheet...

=8-)

I purchased the same wheel, minus the alpine III spokes, for dirt cheap.

The m475, isn't something i'd spent the money on with those expensive spokes - though I think the measurements for the m475 are the same or quite close to the xt fh... i don't think those spoke holes in either hub are wide enough for alpine III.

From what I've gathered.. there can often be a need to use 2 different lengths for the left and right side spokes.

If the spoke length calculations turn out to say you need 260 on one side, and 261 on the other, is it cool just use one length for both sides? Is there a threshhold measurement difference between left and right that can allow one to use one length of spoke? 1 mm? 2 mm?

Get the correct sizes, try to round down the fractions. Never round up on the drive side rear spokes. The high tension needed for dishing the rear wheel can stretch the drive side spokes.

I buy all my spokes from my LBS, they sell any number of spokes at reasonable prices.