First the disclaimer, please take the hub to a bike shop if you are not familiar with the inner workings of shimano rear hubs. I am not responsible for any damages if you can’t reconfigure your powertap hub. I am just sharing my personal experience.
Just got a new powertap pro wheel to train on, works great except for 2 things that bothered me: 1. when I spin the wheel in a stand, there seems to be a wobble to the hub and cassette even when the rim is perfectly true; 2. the wheel doesn’t ride as well as my other rear wheels, it feels sluggish and soft even with high spoke tensions. I fixed both problems over the weekend.
Heard many people complain about the quality of bearing/cone in the powertap, so I decided to change them out to dura-ace (more on this process later). After I finished the installation, put the wheel back on to find the rim wildly out of true. Took me a while to find the cause, but as I changed positions of the freehub engagement to the powertap hub, the rim came back to true. Two things I noticed: 1. when the rim is true, the hub and cassette wobbled; 2. when the rim is out of true, the hub and cassette wobble was largely eliminated.
My conclusions:
1. The contact surface between the powertap hub and the freewheel isn’t exactly perpendicular to the axle axis. A problem with manufacturing tolerances.
2. My rim was laced and trued to an off-axis hub/freehub. So when the hub/freehub was aligned to the axle axis, the rim went out of true.
3. Since the drive-side cone is threaded to the axle, and the bearings are in the freehub, if the two are out of alignment premature wear is bound to happen. It only makes sense.
4. If the bearing/cone assembly is changed to DA or ultegra quality without fixing the mis-alignment, this problem will continue unless the freehub bearing contact surface is grooved to the off-center rotation.
To fix:
1. Put your wheel in a stand and spin it. Pay close attention to see if the cassette cogs wobble when you spin the wheel. If not, your powertap hub was assembled correctly and do nothing (maybe 1 in 10 will come this way from the factory as I will explain later).
2. If your cassette cogs wobble like mine did, you have a mis-alignment between the hub and axle. To fix, you can follow my instructions or take it to a bike shop.
3. If you decide to fix it yourself, please take the time to read the next section “For campy users, or shimano 10-speed conversion” before proceeding. Trust me, you don’t want to go through steps 4-6 and realize you want dura-ace internals for the powertap pro.
4. Remove cassette, undo the non-drive side locknut (if you care about cosmetics, best to take off the battery cap and use a 17mm cone wrench for slots unaccessible with the cap on. The outer exposed surface is too soft to wrench and will dent). Remove the axle assembly through the drive side, watch for loose bearings.
5. The freehub engages the hub through a paw that has 10 notches. Therefore, the freehub can sit on the hub in 10 different positions. 1 of these positions will result in the closest alignment between the hub/freehub assembly and the axle (perfect alignment may not be possible). Here comes the painful, but necessary part of the fix. You must loosen (but not remove) the freehub fixing bolt with a 10mm hex wrench (this bolt is very tight, I used a long torque wrench to loosen it counterclockwise). Do not remove the freehub after loosening as you will lose your position. Loosen the fixing bolt only enough so you can lift up the freehub, turn it clockwise slightly (counterclockwise will not work well). Now it will sit on top of the paw, continue turning slowly until it sits back down and you will have changed the engagement position by 1 notch. Make a note each time you change a notch so you know the order. Tighten the fixing bolt, reassemble the axle and put on the cassette. Put the wheel back on the stand and check for cassette and rim wobble. Depending on how much patience and time you have, there are 10 different positions to test, so I turned two notches at a time for each test, and fine tuned once I got close. If you started with true rim and wobbly cassette, what you want to end up with is a true cassette and wobbly rim.
6. Once the best position is found, true and re-dish your wheel and you are good to go. Besides better machine tolerances during manufacturing by Powertap, I don’t know a better way to get this alignment done correctly, but theoretically this is essential for getting better life out of your cone/bearing assembly. And I assume that a correctly aligned wheel will perform better than a wheel with a wobbly hub.
For campy users, or shimano 10-speed conversion:
I run campy 10-speed with wheels manufacturing conversion cassette (don’t have the spare cash for the new SL). But for those who have problems running shimano 10sp on the powertap pro, this fix might work for you as well. What has always bothered me with my setup is how close to the spokes my 23 on a 11-23 get. More spacers behind the cassette and the 11 is too close to the dropout for the chain to get by. Not to mention I have to change my rear derailleur alignment switching between the powertap and my other campy wheels. Found a perfect solution, through some trial and error.
Buy a 9-speed dura ace or ultegra rear hub (used ones on ebay are cheap, I got the DA version for the titanium freehub). You can completely rebuilt the powertap pro hub with a high quality shimano rear hub. The free hubs on the DA or ultegra extends longer towards the non-drive side, makes it much more 10-speed friendly. The quality of the freehub, seals, bearings, and cone are all better than the originals on the powertap, and the only down side I can see is that more dish is needed to properly center the rim. But if you run 10 speed and is running out of room for the cogs, you may want to try this.
1. Disassemble both hubs, including freehubs (don’t have to removed bearings).
2. Set all spacers aside, from both hubs, you will not need them.
3. Start from the drive side, assemble as follows: put the locknut, freehub cap, and driveside cone from shimano hub together on the short-threaded side of the powertap axle (no spacers, so grease the contact surfaces, and shimano axles are not compatible with sealed bearing on the non-drive side of powertap). After assembly, the exposed axle (to engage dropout) should be around 5.3mm.
4. Go to instructions above and start from step #5. Use the shimano freehub. When reassembling the axle, on the non-drive side, don’t use the powertap 10mm spacer and you will end up with exposed axle of around 5.3mm, same as the drive side.
5. By my calculations, this entire assembly which uses dura-ace freehub/bearing/cone/locknuts, is only 0.3mm wider than the original powertap hub. No problems with setting this wheel into the dropouts on my road frame.
6. Your rim dish will be off by as much as 10mm. Take your time and redish the wheel, or take it to a shop. Now you will have much more room on the drive side to run 10 speed. In fact, the cassette spacing is now identical between my powertap and campy wheels.
Took the reconfigured powertap out for two 25 mile test rides. Runs perfectly. The readings are consistent. The wheel is now much more responsive, due to a straighter hub? or dura-ace complete rebuilt? I don’t know, but it worked out very well.