Sunday, June 28, 2009

Truing a wheel with bladed spokes

...I have recently purchased a second-hand Zipp 202 wheelset with bladed spokes. The rear wheel was a bit out of alignment so I quickly trued it and went for a ride this morning. When I got home I was a little disappointed to see that at least half the bladed spokes were almost 90 degrees out of alignment...

Let me preface this by saying that I am not Jobst Brandt, nor do I wrench for a living. I don't own a wheel truing stand nor a bike work stand. Heck, I don't even own a spoke key! However I do have a very high quality adjustable wrench, a good quality broad-nosed pliers and a bike stand that support the front or rear wheel. Not particularly refined but seems to do the trick.
The method
1. set the wheel that is not being adjusted into the bike stand
2. it goes without saying, but the brake blocks should be adjusted so that the tops are close to the outer edge of the rim and parallel when looked from the front/back (toe in when looked from the top does not make any difference for wheel alignment). The brake blocks are the wheel alignment guides and should be centred on the frame.
3. lightly lube the spoke nipples with a penetrating lubricant (eg WD40) and the point where the spokes enter the hub flange (if the spokes are straight and without an elbow then they will twist here as well)
4. this is the important bit - correct the spoke twist by detensioning the spoke - this is done by grabbing the rim and pulling it towards the seat stay on the same side using one hand. The spoke can be aligned by twisting the spoke flat using your fingers, turning the spoke nipple with a spoke key or fine adjustable spanner, or using a pair of pliers (make sure the grasping edges are parallel) and a cloth to twist the spoke at the round portion where it meets the rim or the hub flange. Often a combination of all three is required. Do not twist the spoke flat with anything other than your fingers!!
5. spin the wheel to identify the lateral wobble
6. correct the wheel wobble as you normally would. Spoke wind-up is easily seen on bladed spokes as it twist out of position. This is again easy to correct by detensioning the spoke by the method above. Often an overcorrection is required (eg half turn clockwise with 1/4 or 1/8 turn anticlockwise) to maintain spoke alignment. Indeed I have since discovered that spoke wind-up should always be corrected even if the spokes are the conventional round shape with an elbow...
7. basic check of spoke tension using fingers
8. take the bike out for a spin and check that alignment is maintained

Good luck and ride safely!