Bicycle Mechanics - Wheel build question.

Guys. I've just ploughed through Jobst Brandt's book and I'm ready to breakdown an old wheel and build it up again. I noticed he shows diagrams where the hub is laterally off-centre from the rim. Is this achieved and adjusted by different spoke tension on either side of the hub?

One of the hubs in the book shows different hub flange diameters, so but I can't work out if the spoke lengths would be the same or if shorter ones are used for the larger flange.

Comments appreciated.

I don't know too much about wheel building, but I believe the wheel that you first mentioned was a rear wheel and the one with a larger flange was more than likely a disk brake hub if it was off of a mtb. If not, it's just depends on the company that made the hub.

The amount of hub offset is called the dish of the wheel, and is quite usual. It is to allow room for a wide cog cluster. The rim should be centralised in the frame, but there is no need for the hub to be, although dishing does weaken the wheel. You set the amount of dish by altering the length of the spokes on either side, rather than differential tension.
Hi-low flange hubs are a real rarity. Stick to a conventional design to start with. JB is of the sensible opinion that a well built standard design is better than a fancy one.
You can get involved with differential spoke counts and tensions on either side , but why make life so complicated.

On a dished rear wheel the spokes on the drive side will be shorter and also at a higher tension. If the spokes had the same tension on both sides there would be no dishing.

Andrew is right. Since a spoke can pull only along its axis, since the horizontal components of these forces must be equal on the left and right sides of the wheel, and since the drive-side spokes are at a steeper angle than the others, the drive-side spokes must be tighter than the non-drive. On a modern 9- or 10-cog wheel, the tension difference can be large, although offset-hole rims will ameliorate this a bit.

I noticed you stated stated you were breaking an old wheel and building it up again. I've built my first wheels in January as part of a bike restoration project. I found great info on this forum and at Sheldon Brown's web site. If you are changing out the rims or hubs I found this spoke calculator at the address below easy to use and accurate.

http://www.damonrinard.com/spocalc.htm

Best of luck :)

I built my first set of wheels this past year.
One thing I noticed with the spoke calculator is
that some of the spoke lenghts were off.
I was using chorus hubs on GP4 rims and the
spokes were all 1 mm off on the rear wheel.
Measure drive and nondrive side spokes from
old wheel and get that size.
Most LBS have an online spoke calculator (which
we can't access?) so double check with LBS.

Bokkie, I'd bet Van Heerden can get the right spokes!

Marty

I use the spoke calculator from the DT spoke web site, it's continuously updated and accurate.

Originally posted by lotek
I built my first set of wheels this past year.
One thing I noticed with the spoke calculator is
that some of the spoke lenghts were off...

If I read this right, Marty, given a hub of fixed flange diameters and a rim of conventional 60cm (26") size, you could in fact use any spoke length that fits?

Going on from this, does the spoke calc workbook take optimal lengths into account to get round the problem where Xmm, Ymm, Zmm all fit but only one is ideal?

Or, is it based on experience and anecdotal evidence?

I know plenty of van Heerdens, but the one you mentioned was of the bike fame no doubt, but I'm not to familiar SA riders, except for Robbie Macintosh who's the only one I've heard of.

Bokkie,

(why do I always think of a pickup truck when I read that? :lol: )

No, there is one optimal size for any given rim/hub combination.
You could use spokes which weren't optimal but then your
wheel is either overtensioned, or never tensioned enough.
What I found is that what the shop had (maybe DT site?)
and what I got from Damon Rinard were different.
I used what the LBS came up with and have had no problems
in almost a year.

Yah, the Van Heerden is of biking fame, runs a very nice
LBS in Jo'burg.
Don't forget Robbie Hunter (rides for Rabobank) when
counting South African riders.

Marty