WR250X(R) mechanical notes from today

Weights:

Avon Distanzia 120/70R17.........8.5lbs (+/- 8 oz)

Bridgestone TW301 80/100-21...8.5 lbs (+/- 8 oz)

Bridgestone TW302 120/80-18..12.0 lbs (+/- 8 oz)

MSR HD 21" tube.....................20 oz

MSR UHD 18" tube...................36 oz

Rim strip..................................2 oz

Wheeling Cycle Supply 18x2.1 wheel

(R/X hub, no sprocket, no rotor).10.0 lbs (+/- 16 oz)

Wheeling Cycle Supply 21x1.6 wheel

(X hub, no rotor).....................9.0 lbs (+/- 16 oz)

TAG 47T sprocket.....................12 oz

Preload adjustment:

The spring preload adjuster threading is about 16 tpi. So one complete rotation of the adjustment ring changes the spring length by about 1/16 inch. So about 6 rotations of the ring take it from min preload to max preload. One complete rotation of the ring makes a reasonable adjustment amount, giving something easy to remember:

Preload

-------

0 (Min - about 8 threads showing above the top of the big locknut)

+16.7% (1 rotation)

+33.3% (2 rotations)

+50% ("Factory setting" - 3 rotations)

+67.7% (4 rotations)

+83.3% (5 rotations)

+100% (Max - 6 rotations)

What do y'all think about that as a rule of thumb?

Rear travel:

Shock free travel @ min preload = 2 7/8 in.

Shock free travel @ max preload = 2 1/2 in.

By "free travel" I mean the distance between the shock body bottom and the composite bumper. The bumper is 1 3/8" in height. Measured while uninstalled.

Available travel at rear axle, as defined by linear travel at axle center, from contact of chain with top chain roller then bottom chain roller. Rear wheel off, rear suspension linkage disconnected.

17" with axle at rear of adjustment range

16" with axle at front of adjustment range

Obviously I have a long way to go in figuring out the practical rear travel.

Questions:

The MSR tubes for the X "dirt wheels" - the valve stem has a dome washer and two nuts below the cap. The stock tires only have one nut. What's the scoop? (My first ever tire mounting experience)

Short-term plans:

- Paint bits of the rear suspension linkage, the gas reservoir, and the TAG sprocket black

- Paint a few bolt heads and other shiny spots on the chassis black

- Reassemble the rear suspension

- Mount the TW301/302 tires and get the new wheels installed

- Investigate and write up the sprocket size / chain length relationship

- Try the rear wheel axle max forward and max back, and measure the impact on sag and spring rate (not sure how to do this well)

cheers,

dh

Questions:

The MSR tubes for the X "dirt wheels" - the valve stem has a dome washer and two nuts below the cap. The stock tires only have one nut. What's the scoop? (My first ever tire mounting experience)

I would think the second nut is a jam nut. Tighten the first nut, and then while holding it with a wrench, you tighten the second one down on top of it.

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