Hello All, First I have to say that this is my first post on the Forum but I have been reading and learning for a couple years now. I have a problem with my 1967 Bonneville. I disassembled the rear wheel for new stainless spokes without measuring the offset first. Dumb mistake but there it is. The Triumph manual says 1 3/4 inches with my WM3 rim but how is it measured and from where?
Hey Kev, never mind. I did a search on wheel lacing and found a thread where this was discussed. It's 1 3/4 inches measured from the face of the brake drum to the edge of the rim. Thanks for the help. Roger
For a 1967, with the spool steel hub, the offset from the surface of the brake drum to the center of the wheel is 89mm. If the drum is off, then from the drum mounting surface on the hub to the wheel center the measurement is 44mm.
"Rim offset", .... hmmm. It would seem to me the only person needing "offset" values would be a mechanic you Take your wheel to have it laced and trued on his truing stand. Otherwise the wheels should be trued and aligned on the bike seems to me.
Front wheel: Merely center the front rim between the fork sliders. I measure this using a little tapered gauge I've made. An inside caliper works too. Support your magnetic base dial indicator on a largish piece of steel on the shop floor. Then true and center the rim. Axial and radial runout less than 15-20 thou is great. Less than 40 is OK.
Rear wheel: The plan is to have the rear wheel spokes adjusted so the rear wheel is in alignment and tracks in line with the front wheel. "Close enough", may be OK with you, but I like to measure and align the wheels on the bike. Here's the procedure ... as old a method as motorcycles.
You will need a pair of straight edges to clamp on either side of the front rim that will extend beneath the bike and straddle either side of the rear rim. I use 1" x 1" alu tubing. Nice and straight. I've seen steel tube and light angle stock used OK. No no, you'll never be able to find two pieces of wood that are straight enough. And forget the silly idea of using long easily broken floresent tubes.
If your front rim is narrower than the rear, shim the tubes with something. I use lengths of 1/4" trim wood taped to the tubes. Drill the tubes for 'all thread' or wire, etc. and clamp the tubes to the front rim extending beneath the bike supported with both wheels off the floor. Use your caliper and insure the tubes are parallel their full length. Adjust your clamps as required.
Now finnish aligning your rear wheel rim with the rim centered between the tubes. Make your final spoke torque adjustments for minimum axial and radial runout while keeping the rim centered. Less than 15-20 thou error is great. Less than 40 thou is OK.
If the ears on your swing arm are bent side to side you will notice this when trying to center the rear rim. Don't despair, bend them back straight and parallel to each other.
Something worth checking while working on wheels, is to check if your swing arm arms/tubes are true. Using shims block up your bike so it's level side to side using a carpenters level held verticaly against the trued front rim as your reference. Now hold the level against your trued up rear rim and it should indicate true and vertical. The level laid across the swing arm tubes should also check true. The swing arm tubes can also be checked by using a level reference from near the pivot bolt and then measure across the ends of the tubes near the axle tabs.
A difference found between the two methods when checking the swingarm could indicate the frame is tweaked/twisted at the steering head. This is a fairly common affliction with a frame that's ever been endoed. BTDT .. got the shirt.
BTW, I have a nice (expensive) Rowe truing stand as used by wheel builders. I seldom use it except to hold a wheel when doing a rough build up. I would use it however to build up a duplicate wheel if needed. Oh, I forgot to mention ... There's a critical amount, not too much, but enough Budwieser that will make wheel building go more smoothly. Works for me. heh.