Tom Bombadil

Got my recumbent back from the shop today. I had my FSA triple crankset with 170mm crank arms replaced with a Shimano 105 triple crank with 155mm arms (I supplied the new crank). While 170's work fine on my upright bikes, I had a hard time maintaining a steady cadence on my bent with them. I either was reaching too far on the downstroke or my knees were coming up too high on the upstroke.

Did some reading over the winter on other bent forums and a number of articles in bent magazines and found that many others had the same issues and had found relief with shorter crank arms. There's something about the recumbent riding position, where you aren't pushing down with your weight on the cranks, where many find the shorter arms easier to spin.

Had to readjust my seat again and after a couple of tries, all seemed well. So I took it out for a little spin, just 4 miles around the neighborhood. It made a big difference ... it was much easier to stay in cadence. And much more comfortable to ride.

The jury will be out until I can take a couple of 25-30 mile rides, but so far, so good.

Have to put in a kind word for my LBS. In addition to replacing my bent's crankset & swapping the pedals to the new one, they replaced my hybrid's chain (I supplied the chain) and adjusted the rear derailleur. They took both on test rides and pumped up my tires to full pressure. The total bill was $30. I would have paid that just for the crankset swap. I know I wasn't going to try to do it.

I thought it was particularly low given that I had bought all of the parts elsewhere.

10 Wheels

The cranks on my new Felt are 1/2 longer and are more to my liking from the Nishiki.

Tom Bombadil

I was going to drop down just a bit to 165mm. But the more I read on the recumbent forums, the more support I found for going down to 145 to 155. A bike mechanic has a web page on how he can redrill many existing crank arms to drop them by 22mm, so a 175 goes to 153, a 170 to 148. I found a number of people who had used his service and loved the results.

So I decided to take the plunge and go to 155. If I had 175mm arms to begin with, I would have opted for the redrilling, but with 170s, going 148 seemed so drastic that I couldn't go there.

Bill Kapaun

It's amazing what even a 5MM decrease can do for cadence, especially if one has bad knees!

Tom Bombadil

Yes on my test rides on upright bikes, I could tell a big difference between 175 and 170. The bike I purchased had 175 installed and I had them swap in 170s. Would have gone to 165 if that had been an easy option.

Retro Grouch 

Interesting. Now that you mention it it makes sense to me but it's something that I've never had a reason to think about.

Are 155mm crank arms difficult to find? I don't think that I've ever seen them listed from any of the sources that I typically use.

Tom Bombadil

I've seen a lot of them from BMX parts dealers. Apparently short cranks are common on those bikes.

In my case, I found a guy in Minneapolis who specializes in this sort of thing. Caters to the recumbent market. I went with his Forza/105 triple crank. He offers a few different cranksets that he's pieced together over the years.

https://bikesmithdesign.com/

RoMad

What did you do with your old one? I would like to replace my double with a triple on my old bike and I like the longer ones. If you decide you like what you have let me know.

Tom Bombadil

I am planning to keep the old one, as it is nice quality triple w/170mm arms. That's what I'm using on four of my other bikes, so it gives me a replacement option, an upgrade option for one of them, or even something to throw onto a new frame if I ever go that route.

That was one aspect that I liked about going this route. Put the new 155mm on my bent and then have something I can use on one of my other uprights / diamond frames.

bkaapcke

I was much more comfortable on a LWB 'bent once I changed to 160 cranks. Definitely easier on older knees. bk

Tom Bombadil

It would be nice if most cranksets enabled one to easily swap different crank arms onto them. It would be fun to try a few different lengths on different bikes.

Bill Kapaun

Your link kind of got me thinking-
I wonder what a weldor/machinist type would charge to shorten my old steel (FC-200) arms? It wouldn't have to be pretty As long as the length matched and the pedals pointed the right way....

BTW, I'd addressed this topic sometime back-
https://www.bikeforums.net/fifty-plus-50/361045-your-cranks-too-long.html

The 165MM cranks I'd ordered "fell through the cracks, but I'd like to keep the Bio Pace rings on a budget.

Tom Bombadil

The problem is that your present crank arms have holes drilled in them. That's why the guy in Minnesota is limited to redrilling at no less than 22mm shorter than your present arms. That's how far down the arm he has to go in order to leave an adequate amount of metal at the end so that pedal won't break off if you hammer down on it.

Thus the longest a 175mm crank arm can be cut down to is 153mm. And not all can be drilled that long. Their are some, that have thick ends but are thinner up the arm, that cannot be redrilled at all.

As to covering the topic before, I believe we covered it in 50+ at least 2 other times since I've been on BF. Topics repeat over time - which is fine as there are almost always new ideas and experiences each time. In this case, I wasn't trying to address the topic broadly, just reporting on my experience on a long'ish 'bent.

Bill Kapaun

I didn't mean to redrill the arms, although one could weld up the holes and redrill/retap. Of course that would require both RH & LH taps.
What I meant was to physically cut the arm in 2, remove the desired amount and weld back together.
I'm talking about a cheap STEEL crank (the kind with the riveted rings).
It shouldn't take too much effort to rig up a holding fixture to keep things aligned for rewelding. It'd be a bit of a pain for a "one of", but maybe not too expensive.
Hmmm, I've got a friend who has a friend... I sold my arc welder a couple months ago because I was getting too blind to use it.

stapfam

I don't ride a recumbent- But I have had bikes where the leg travel has been too great to feel comfortable and be efficient. On mountain bikes-I have used 170 and 175 cranks and can't tell the difference- The road bike is different. I now have 165 on one and 172.5 on the other. Same Compact gearing but I find that I spin faster with the 165's. The longer cranks do not feel any different to me and I notice no difference in the speed- but Cadence is definitely higher with the shorter cranks.

And on the seat adjustment- Found the same in that I had to alter the saddle height to accomodate the shorter cranks. When I carried out a test by swopping cranks on the bike- I forgot to do this and wondered why I felt uncomfortable.

BlazingPedals

I bought a set of 155s two years ago and used them for about 2 months. They came off because I couldn't climb a hill with them. I found myself walking up a 6% grade because my 30/32 wasn't low enough. My training was at a low point that year, so I may give them another chance some day.

Bill Kapaun

As I pointed out in my link above, 5mm difference totally changed my gearing dynamic. Basically I'm running the same cogs with a 38T ring that I was running with a 46T. AND, with a bit more speed and a lot more stamina.

Tom Bombadil

Bill,

I see you live in "Orygun." The next town over from where I live is Oregon - pronounced Or-re-gone. It took me about 3 years after moving here to pronounce it that way. If you say "Or-re-gun" you are quickly corrected. But now I'm ruined when I go to national conferences and run into people from the state of Oregon.

bobkat

I have Mark Stonich's (bikesmith) 155's on one of my bents and knee pain in theleft knee went promptly away. Love em!
I just bought a Rans V3ti and the only thing I'm not sold on is the long cranks. They are carbon fiber cranks so they can't be shortened. If I start getting any knee pain I'll have to look into switching. I'm hoping this bike will be so light and nimble that my knees can take the 175's supplied with it.
If not, I'll have to call Mark back. He's sure a great guy to talk with! He has lots of advice.
I think one of the reasons long cranks work OK on uprights is that on an upright your body is continually more or less bouncing up and down and compensating for the length, in fact, taking advantage of it with the weight of your body. But you can't do that on a bent! So knees tend to pay the price.

JanMM

If I had a different 'bent, I might try shorter cranks, but I'm about at the limit of seat travel. A shorter crank than the current 170 wouldn't work for that reason. I did resist the urge, when I put a new Truvativ crankset on last year, to go with the 175 that is my norm on "normal" bikes.

Tom Bombadil

Time for a ride report.

I had the Bikesmith 155 Triple Crank installed on my recumbent, replacing the original 170mm crankset. Haven't put too many miles on it, but have had it out for three rides, totaling about 40 miles.

The shorter crank really helps me to maintain a smoother, higher cadence. Wherein I couldn't find a seat position with the 170 that was right for both my maximum and minimum extension, the 155 is much better. With the 170 I was only able to spin at around 70-75, losing contact with the pedal on the downstroke. With the 155 I was able to apply power throughout the entire revolution and got my cadence up to 85-90.

This translated to a gain of about 2 mph, going from 12 mph on flats to 14. A modest speed for sure (my bent is known as one of the slower ones) but it felt good to me. The overall riding experience was much more positive, just spinning and cruising along. Going up hills was much improved too, powering smoothly up a few modest slopes.

I'd like to compare the 155's vs 160's, as I feel I could handle a little more extension, but that's hard to say. I find it very interesting that I do fine on 170s on my upright / diamond-frame bikes while struggling with the same on my bent. However it is a much different pedaling motion.

Now I need to change the tires, as it has off-road knobbies that feel like they provide constant rolling resistance.

Beverly

We have a similar problem around here with Russia, OH. You better pronounce it "Ru-she" or the locals will quickly correct you.

bobbycorno

My first 'bent (a used VRex) came with 172.5's - shorter than the 175s on my df's, but not radically so. Tried an old set of 175s on the Rex and just about killed my knees. Recently bought a NOS F5 w/ 170s, which I liked so much I switched to 170s on the Rex as well.

One thing to keep in mind is crank length relative to leg lenght: according to Lennard Zinn, with a 36" inseam (and I forget what femur length), I should be riding 195s (yes, one NINETY fives), so I was on "short" cranks to start out with. For folks of a more average size, 145-155 cranks would probably be proportional to what I'm using.

Of course, YMMV (and probably will)

SP

Bud Bent

Funny how often that happens. In West Texas, there's Colorado City. "Colorado" is pronounced with a long 'A'.

Timtruro

Sounds like a great LBS, most frown on you walking in with parts purchased elsewhere unless they are part of a very big job.