If I want to ride with two different crank sizes, I can buy double-hole KH Moments, either 125/150mm or 137/165mm.
But what if I want some other combination?
I could buy the the two sizes I want separately, but what if I want to swap them often… say daily?
Are there any problems with this?
It’s a pain, but there’s not a mechanical reason why this should be more of a problem than changing pedals. Unless they’re Qu-Ax cranks, which won’t hold up to much messing around with them.
A pain? Truing a wheel is a pain, or at least time consuming. Switching cranks takes about 3 minutes (5 tops) per crank and three tools. 8mm hex key or socket, Crank puller, and pedal wrench. I keep a complete set of uni tools in a small tool box so I don’t have to hunt for tools in my other tool boxes. Makes job like this go much faster.
With that said, nothing is going to be as simple as dual hole cranks (and you only need one wrench) and then there does not have to be any concern about taking them on and off and its effect on the splines. IIRC there are people here who don’t advocate taking cranks on and off a lot.
Wear and tear from taking cranks on and off: CrMO not so much, Aluminum… a little more so. They both will wear out, and you have to be careful that you don’t ruin the splines to much. With CrMO you may get a little slop from lots of on and offs, not a huge deal besides making an awful creaking sound.
With Aluminum it is much easier to mess up the splines since the metal is much softer than the steel axle. This is not a problem at all if you are running your setup without spacers(the cranks can just sit further and further on the axle as they need), however if you need spacers and you start to get slop in your aluminum cranks you will run into the snowball effect. The most common problem Ive seen is that the cranks will have enough slop that they loosen themselves up creating more slop and rounding the splines even more. It can get worse as the crank gets looser, and the crank will get looser as it gets worse.
With that said, I have neever seen complete crank failure do to this… just something to keep in mind.
I personally change my cranks quite often, with little to no problems. Although it is not nearly once a day.
The reason I asked about this is because I am thinking about getting a new uni: a KH24 with a Schlumpf.
For the trails:
24 for technical trails
schlumpf for flatter trails
longer cranks for powering up hills
For the road (really just casual neighborhood riding with the family):
schlumpf for speed
shorter cranks for speed
I’d only change cranks at home, and so, I could just have two pairs of pedals and keep them on the cranks.
Is that logic sound?
Are there other concerns to consider when changing cranks regularly on the Schlumpf?
That’s a good thing to know. Because when I ride trials, I put my tensiles on my uni. And durring the week I ride more flat/street because all the good trials spots are still a little bit snowy so I put my Moments on. But I have another 20" trials uni witch is more crappy than my “Custom KH with my Ti hub” and it doesn’t have a CF base so I dont want to ride it. So I always end up by changing my cranks. Who would want to ride a crappy uni when you have another really good uni just beside it?
EDIT: 1400th post!
Another option could be self machined dual hole cranks. I have no experience with this but maybe someone else has. Moment cranks would be ideal for this because they are very strong. I too think changing cranks is some kind of work you don’t want to do every day.
In my opinion 125/150 cranks are very good for a geared 24" uni, so why not stick with that?
The problem with the Schlumpf is that in theory you should use loctite and let it settle over night before using it with the changed cranks. Personally I decided not to use loctite but to check and retighten the bolts very frequently (before every other ride). When I change cranks on a geared uni I retighten them after 5, 10 and 20km with the torque wrench. Better safe than sorry… I’ve had lots of unpleasant surprises already. (Still waiting for my Schlumpf replacement, it feels like it’s been years now…)
I figured dual hole cranks are not made with a wide range because at the small setting the unused length of crank would interfere at the top of your pedal stroke. Maybe knock your ankle or push your foot off?
I have very little experience with different crank arms. I know my current 24" Onza muni has 165mm cranks, and I know I like to climb hills on the trails. I am concerned I’ll lose an advantage with 150’s. But I really don’t know.
That only helps a little bit since to remove the cranks the pedal have to come off to use the crank puller. I got pedro crank puller because it was shorter, but even with 165’s the wrench is not short enough to spin all the way around with the pedals on.
So you are spinning pedals off and on at some point no matter what. But by putting the pedals back on when you take them off would save some time (and one less tool needed) when you want to swap them out again. But I find it easier to do that work with the pedals off so I can swing the 8mm hex tool all the way around. Also the uni lays flatter and doesn’t pivot around on the pedal while you are trying to work on it.
If my pedal is already on, I just use the long end of the hex key to screw in the axle bolt. I think it comes down to what tools you are using and how you like to work. But pedals on is not going to be a miracle time saver. Its just do you want to spin the pedals on after you remove them or when you are putting the cranks on.
I like to experiment with different crank lengths and drastically change my uni to match the conditions on a regular basis. Therefore have changed my cranks quite often but keep going back to my echo 160mm cranks. I do not use spacers and I have noticed that the cranks seem to sit further and further on the spline every time. They have been put on an taken off over a dozen times and are just about at the point where they will bottom out when tightened properly. They were a bit oversized to start with.
It is evident to me that changing my cranks often is definitely wearing out/stretching the spline interface on my cranks. I haven’t had problems yet but I might after another 10 or so changes.
I currently have KH 137/165mm cranks on my 26 I am not sure how much I like the 165mm hole (funny how much difference 5mm makes in feel) but the second hole (137) is great for taking the pavement home without having to carry a second pair of cranks with you.
I have noticed the same thing and I only have a few changes. It looks like im hitting the stop on some of my cranks as well but the crank bolt seems to still go on nice and tight. I don’t sense that anything is bottoming out.
Not sure what the long term outlook is.
I can’t believe that crank removal should degrade the splines in so few removals. I have new cranks coming tomorrow or tuesday. When I have the cranks off I’m going to look at the splines in good light.
Just keep your crank puller lubricated, otherwise you will destroy it.
Thanks for pointing this out! I hadn’t thought about interference with the crank puller.
This is not very encouraging.
I think I’m just about completely turned off to the idea of swapping cranks for muni and road. I was hoping ISIS was actually engineered completely different and didn’t even use tapering. But it sounds like it is the tapering that is the problem here. Wedging a softer metal against a harder metal… it’s just not designed for wear and tear.
Maybe I just need to settle for a dual hole crank.
On my 24" MUni I have already tried 137, 150 and 165mm cranks, both for downhill and uphill. Finally I went back to the standard 150s because to me they seem to be the perfect size for MUni when using a 24" wheel. After a quite short amount of time you can climb quite well with the 150s and on downhills you can ride without using the breaks most of the time. And with 125/150 dual hole cranks you would also have the option for the shorter and faster cranks.
Yeah, I’ve been searching and reading about cranks lengths and hills. It’s tough to figure this out for me.
I’ve read similar comments to yours. Riders with 165s finding the 150s worked well for them, though they suggest that experience and improved skill may be the reason.
But have you/they ever gone back to 165s? I mean, if your skill has improved, then maybe 165s would make you a hill climbing god.
ISIS does use tapering, but the specification calls for the primary force to be the pressure of the crank against the crank stop, not the pressure of the splines against the hub.
Unfortunately, our parts do not meet the ISIS spec very well. The use of a spacer as a crank stop on some configurations is fairly questionable, and other configurations (like the Schlumpf) don’t have a crank stop at all. Additionally, the dimensions on the hubs or the crank splines tend to be off; often a set of KH Moments doesn’t sit properly against the crank stop the first time they are installed.