Hey everyone. Was just looking for a little advice from some of the commuter guys and girls on these forums. I am currently training to do a uni tour mid way through next year (details when it gets closer to fruition!).
I’ve got a nimbus 36" with t7, airfoil and 152 mm cranks. So far i have found it to be a really nice ride for hills, but a little cumbersome for flat sections that could be done easier with shorter cranks. I know people ride 110’s and even smaller for flat fast sections- but lugging around a crank puller and a spare set of cranks for a ride is not ideal. So i am asking if anyone has gone and got their commuter cranks engineered to take their pedals at different lengths?
The cranks i have at the moment are quite beefy but have fluted surfaces ( i assume to reduce the weight) on both sides of the crank. Do you think getting second pedal threads put in my cranks at the 110mm or so mark would reduce the cranks strength in a way that would cause problems when I’m cranking up hills on the longer 152mm option?
If the structural integrity of the cranks are in question, do you think that putting in a dummy pedal spindle in the 110mm pedal hole when riding the 152 option would help increase the strength? I’m thinking i could get something engineered that would be like a 15mm allen bolt that could be easily inserted and removed from the crank.
Any advice you could give me on this matter ( or even your preferred crank lengths for different riding terrain) would be really appreciated! I’ll attach some pics of my cranks for you to look at.
people have certinaly drilled prowheel cranks for an extra pedal hole, but I don’t think it will be possible with the cranks you have currently because of the large dish taken out of them. If you search for previous threads on the subject you might find someone in Oz who has the appropriate tools, unfortunately pedal thread taps are quite expensive.
Well, I have double-drilled cranks (on a 26er, but I hope that doesn’t make much difference), and yes, it’s a lot easier than using a crank puller etc. Nonetheless, it still takes me long enough to change lengths that I don’t bother for hills, only for on-road vs off-road sections - i.e. short for riding out to the trailhead, long for riding around the trail, then short for coming back. If I have to change crank length more times than that it starts to become annoying…
The other surprise is how much better I’ve got at riding off-road, and doing tricks and idling etc., with the short cranks, since I started - so I don’t use the long crank length as much as I used to at all. That may just mean I should shorten both - atm I’ve got 100/125 (on a 26), so maybe it’s time for 90/115 or something - but you do tend to get used to one length…
However if your main use is for commuting…I’d suggest you might be just as well off with a single crank length somewhere in the middle, say 130mm or so…???
Maybe some of the other listmates can add their source, but Mark Stonich of Bikesmith Designs in the States does this service. He can tell you what cranks are drillable and what are not.
Have the area where you want to tap the new holes built up with weld. Then drill and tap your new holes. This should be easy enough with steel. I haven’t experience with alum welding, but I think that should be do able as well, and lighter . Steel might be a good choice if you plan on moving the pedals a lot, the threads should last longer.
Plugging the unused hole will not add any strength, so don’t bother with that.
I don’t think it’s realistic to expect that you’ll be moving your pedals from one crank hole to the other multiple times every day on your commute. Even leaving aside the factors of hassle and grease, pedal threads are not really set up to take that kind of use; at some point you’ll cross-thread one and then you’re hosed.
I think your best bet is to get 125mm cranks, or at least 140mm, and just get used to climbing hills on them.
I went to an engineer that is a friend of my family today with my unicycle to ask his opinion on getting my cranks drilled. After a bit of a chat he was enthusiastic about giving it a go- we decided on getting a small cylindrical insert- threading the inside of it to take the pedal, then drill out a hole in the crank then weld it on both sides of the crank to hold it in place. I’m going to take the cranks there on monday (want to put in some km’s this weekend) and will hopefully have it done by Wednesday. I just need to make my mind up on my second crank length. At the moment my mind is leaning at something between 100- 110mm. I hear people get used to the shorter crank lengths if you use them a lot so i’m thinking of going shorter rather than longer and just using the 150’s when i get to a bitch of a hill. What do you think?
mark
I would stick with 110mm as a minimum. 110 is the shortest size that is sensible for most riding (except in very hilly areas). I’ve never felt safe in any kind of hill with shorter cranks. With 100 and 150, you’ll want to use 150 any time you went near the tinyest hill so it’d be annoying.
You might even find 125 is more sensible.
This is probably obvious, but don’t forget to make sure he knows that the left crank has to have a left hand thread.
125 is a nice go between crank size for any kind of riding. Most of the riders on MUT ran 125mm cranks for the whole thing.
I’m really partial to 110s though, because they’re fast AND you can crank up some pretty stupidly steep hills on them once you’re used to it. I don’t think I’d go for double drilled cranks on a pure road unicycle, mostly because I know I’d never really need above 110s to ride anything in my (fairly hilly) area.
How do you know that? I think it would add strength. I imagine that the crank would fail at the spot where the additional hole was drilled, and that the wall of the hole would buckle inwards in the process of failing, or at least become “unround”. Plugging the hole wil prevent its deformation and hence resist the failure to some degree. Napalm’s engineer friend might be able to say whether it’s enough to be worth it.
Ok well i got the cranks back form the engineer today and they look like they should work really well (have not been able to test them yet as my Uni is in the LBS getting a caliper brake and some other stuff put on it). Here are some pics for you guys and girls to look at if you are considering doing something similar to what i have done. Will give you an update on the whole setup after i have given it a considerable road test. You can see from the pics that he filled in the fluted part of the crank (front and back) where the new pedal hole goes. It seems as though this extra material will help strengthen the crank around the new hole. Oh- the crank length is set at 152 and 110mm.
Mark
- but you do tend to get used to one length…
