102mm cranks on a 29er...good idea?

OK, I had 127mm cranks on my 29er. The left one went kaput, so I decided to go a size smaller. I ordered some 102mm cranks. Looking at them side by side, there doesn’t seem to be much of a size difference. I mean, how much can 1 inch throw it off? Well, come to find out, ALOT!!!

I got them put on thru the LBS. Got home, aired up the tire, and tried unsuccessfully 4 times to do a static mount. Normally, on my old cranks, I’d nail it each time. Not so much with these. First thing I noticed, leverage. Or should I say, the lack there of. When I would get up and in the neutral position to start going, there wasn’t much to get me going, takes a little more umphf to get going. I rode down the street and back, and it felt a little wobbly, but fast. I came in for a stop, tried my usual maneuver, but the uni wanted to keep moving forward. I hop off, and the uni keeps going for about 15 ft. Hmmm, seems like all I’ve learned with my 127s is now out the door. I’m not sure if or when I will tackle a hill or two with this thing, how it will perform.

Now, was it worth it for me to move down a size to 102? Or should I have kept it at 127? I know it will take me a bit to relearn mounting and stopping with the 102, I just wanted to progress to the next step.

Just take some time to get used to it. It’s much faster than 127’s and 150’s. I rode Uninam on it (www.uninam.net). It climbs pretty well.

Hi Rubix,

It certainly all depends upon the type of ground you usually ride (roads or off-roads), as well as the elevation delta in your region.

I actually use my 29er off-road mainly, and am very happy with the dual-hole Moment cranks 125/150 - however the area here is made of hills and mountains! So I would not go below 125mm myself.

Now, I tried some 100mm cranks this week-end on my 29er, just to validate that the Qu-ax cranks were indeed compatible with the Moment hub from KH (anticipating my order of the new KH36 this Summer!).

Well, even though I am very used with 102mm cranks on my 36er (being my daily commuting friend) - I for sure felt pretty strange on my 29er with 100mm cranks.

But as GizmoDuck said, that’s, before anything else, largely a matter of getting used to it and practicing. And then, a matter of adequateness with the ground you usually ride (i.e. you may eventually master the 102mm cranks, and yet want to stick to 127mm ones).

Which cranks did you choose, BTW? Are you ISIS or square-tapered (I mean… not yourself… your 29er :wink: )?

Cheers, MadC.

I am square-tapered hub for the time being. I want to get an ISIS, but then again, who doesn’t? I got the pro-wheel 102s. Not sure if these are good, but they were who made the 127s I had, so I figured why not?

Yeah, I am gonna try a few mounts today on my ride. Static, rolling…maybe a rolling hop, all depends. My typical ride is road, but I may want to have a second wheel set for when I get the itch to Muni. My climb is this bridge here…

I’ve made the climb before, as climbing from one side is relatively easy compared to the climb from the other side. You are right, as I may go back to 127s as my prefered length. But I am willing to give these a couple of months to see how I cope…only time will tell at this point.

102 vs 125

I tried my 102 on my 29" for one week.

Here’s my notes:
Daily commute to and from work ok, but static mount harder.

Marginal higher speed but coming down hills harder to slow down.

Feels smoother peddling at high speed with less wobble affect.

Forget about riding off road, couldn’t get enough leverage (sticking with 125 here).

For my riding requirements I’ll stick with the 125 for both off road and communting. I even use the 125 on my 36"

127-102 is really a drop of two sizes, so it’s not unexpected that you’re finding it a bit challenging. One thing to remember is that you need to raise the seat an inch to get proper height with the new cranks; that might be one thing that’s throwing you off.

Just practice with it, you’ll get it.

You know, raising the seat one inch never really occured to me. I will try that this afternoon when I wake up (been up since 2 am). And I said I went a size down since that brand goes from 127 to 102…I guess 114 fits in there somewhere. for all you smartasses, i know it falls between 113 and 115

I bought some 100mm cranks a few months ago. I usually ride 125s. I wanted the extra speed. I tried them for two days, and although they were great on the flats, it was hard to maneuver around obstacles and make really tight turns around campus. I UPD’d a few times in front of a lot of people, and haven’t used them much since. I wanna try and get more used to them this summer, though.

I raised up my seat about an inch or so, and it was better. I noticed with the seat down, I wasn’t sitting in the seat like I was suppose to. I still need to practice my static mounts, and I’m about 30% successful right now. So I figure about another week or two and I will be ready to head downtown and try them out there.