Two weeks ago I replaced my standard KH splined cranks with a pair from DM Engineering.
You may have read on rsu that the KH splined cranks are not for everybody. This is mainly due to the fact that they have no Q in them whatsoever. If you unfamiliar with what a Q-factor is then you can find a clear definition here:
Because the KH cranks are perfectly stright some people (like myself) hit our heels on the cranks where they attach to the hub. More often than not this will cause a upd. I found that I had to place my feet perfectly on the pedals during a freemount or I would knock my heel and upd. To resolve this issue I had purchased some large pedals (Mosh) which allowed me to place my feet further out away from the cranks. This helped somewhat but was not the answer.
After bantering back and forth with users of rsu, I concluded (thanks to Frank A.) that there is only one set of 170mm cranks that will fit the KH24 8-spine hub. The DM Engineering cranks. Basically there are two reasons for this:
BMX cranks cannot usually be found in 170mm. They are typically only available in 175mm or 180mm which is just too long for a 24" unicycle wheel and average sized rider.
Most of the low-end splined BMX cranks are fluted for a 10 spline axle rather than the 8 used on the KH hub.
Now comes my delime… should I spend with shipping $230.00 (USD) for the DM crank arms or should I do as Frank has done and build or purchase a new Profile wheelset? I’m not much of a mechanic so building my own wheel is not likely, and buying a new Profile wheelset would set me back about $500.00 (USD). I decided to pursue the DM cranks.
The first thing I did was call Jordan at unicycle.com. Frank A. had mentioned that Jordan fitted the cranks to the KH hub, but I wanted to be certain they fit well before I put my money on the table. I was reassured by Jordan that they fit just fine but they would only be held on to the axle by the pinch bolts and not the end bolts. The spline flutes on the DM cranks run all the way through the cavity preventing the end bolts from fitting. The plastic collar on the bolts also prevent a fit but are easily removed. Using just the pinch bolts is fine from a tightness reliability standpoint, but I was concerned that water and grime would enter and settle in the axle’s threaded cavity if the hole was not covered. Jordan thought the standard dust covers would fit so I purchased a pair but they didn’t fit- (shaking fist) damn you Jordan!!
I wasn’t going to let this spoil my fun so I installed the cranks anyway. First, I lathered the splines with a fresh helping of copper anti-seize to prevent creaking, then I slid the first crank arm on to the axle and tightened the pinch bolt. Look’n pretty sweet! I started to install the second crank arm but it was too tight to simply slide on to the axle. I remembered reading that the Profile cranks are difficult to slide on sometimes and that they had to be whacked on with a ‘rubber’ mallet and that’s just what I did. It required very little striking force to get the crank arm in place. I tightened the bolt, put on the pedals and went for a test ride.
My neighbor is an aircraft machinist so I had him take a look at the end bolt situation. Originally I thought I would have him grind out the spline flutes to allow the end bolts to fit. Later I decided it would be better to go the other way, taking down the flange on the KH bolts instead. He agreed. Why not, after all the only purpose for the bolt is to keep mud and gunk out of the axle.
I’ve been riding with DM cranks for almost two weeks now and I really enjoy them. I’ve not hit my heel a single time on the crank and in my opinion the added Q-factor actually make riding more pleasant. The pinch bolts have adequately secured the crank arms to the hub and I’ve not had to tighten them at all. A strange observation is that the added Q seems to give me more torque for things like climbing hills. It could be that my legs are getting stronger or that I’m becoming more comfortable and accomplished with the unicycle. Either way I’m pleased.
If you have a KH24 and you’re unhappy with the cranks there’s an alternative for you- DM cranks. The plus side is that the DM cranks are solid, proven to work well and cost less than a Profile setup. On the minus side it’s still an expensive solution. I think if I were capable of building my own wheel I would have spent $300.00 (USD) on the Profile hub and cranks instead. However, as I stated before I’m not much of a mechanic so I would have had to purchase a pre-built wheel for around $500.00 or have one built locally. This solution has worked well for me and I’m happy with it.
My neighbor still has the bolts. He was conservative when taking down the bolt’s flange on the first run and needs to take a bit more off. When the bolts are returned and in place I’ll take some photos and post them to the gallery site for anyone who would like to check it out.
If anyone knows of any other 170mm cranks that fit the KH 8-spline hub you should post about it. I’m sure there are others like myself looking for an inexpensive alternative to the KH cranks.