ricohman

I have finally got the FSA road triple swapped out for a Shimano Trekking LX crankset on my Sherpa 30.
I decided to bring down the arm length to 170mm from the 175mm to get my cadence up a bit. And the new gearing at 48/36/26 will be a lot better than the 52/42/30 that came with the bike.
All my old school bikes are 170mm. And to tell you the truth I always found myself dropping gears to bring up my cadence on the new bike.
But will the 170mm cost me in power for climbing on a loaded bike?
At 5'9" I thought the 175mm a bit long for a touring bike.

redtires

Let us know how your experience goes with the shorter crankarms...I'm sure I'm not the only one here that has thought about different lengths.

ricohman

Its -42 here right now so I may be a few weeks on the commentary!
I thought about this all winter though. There is much to read but little of it has any practical relation to loaded touring. Lots about racing, little about touring.

Randochap

I doubt you'll notice any difference. I don't, between 165 and 170.

ricohman

Very true, but the older I get the more I'm inclined to preserve my knees.
I have read you can get serious knee problems from cranks that are to long, but shorter arms never hurt anyone.
And since I'm in no hurry, but I wanted to get my cadence up, I chose the shorter arms.
But all my vintage tourers have 170mm anyways so maybe this question is pointless.

rhm

170 is definitely going to be better than 175, but the difference is going to be too small to notice. I started getting shorter cranks on my bikes a bit over a year ago; I didn't even notice much difference when I went down to 152 mm (6"). Now I have most of my bikes set up with cranks in the 140 - 155 range. The main problem is that most cranks shorter than 165 mm are BMX style, and aren't drilled for a triple (but there is one cheap triple crank called Forza that comes in 145 and 155 lengths).

One option, if you're daring... you can take a beefy mountain bike crank arm and cut it down. The smallest amount you can remove is about 22 mm, so if you start with a 175 you'll end up with 153mm arms. I've done this to a few cranks, and it is not as complicated as you'd think.

Basically the shorter crank arm means less leverage, which you have to overcome with higher cadence. In bicycling you're always balancing a muscular vs cardiovascular workout; higher cadence tips the balance in favor of a cardiovascular workout. But at low cadence short crank arms are harder on your muscles and joints, so you need lower gears.

Make sense?

Remember, every millimeter subtracted from your crank arm has to be added to you seat post. At the same time you will gain a millimeter of toe clearance, heel clearance, and so on.

EDIT: my inseam is 32 for reference.

kayakdiver

This is the setup I run on my Jamis Aurora. My inseam is a 32 for reference. When touring I'll take any help I can get when climbing and keeping my cadence up is much better for my knees. Gearing works great when I'm on tour and not to bad around town running errands when not.

rhm

I missed something. What is the setup?

smovlov

I just thought I'd throw this in here.

https://bikesmithdesign.com/Short_Cranks/shorten.html

Seems pretty cheap.

kayakdiver

LX Crankset with 170 arms and the same chain rings. It's a nice solid crankset for touring. I was referring to the OP's new crankset.

KoYak

Just a couple of observations on short cranks. I’m 5’8” w/ 30” inseam. I have short cranks (150mm-155mm) on all 5 of my bikes. By spinning w/ short cranks, I feel like I apply power during more of the pedal stroke. With longer cranks I feel I apply power only during a very short arc during the downstroke which I noticed as the bike surged with each downstroke. W/ Short Cranks, I just feel smooth power delivery to the pedals.

As for performance, I can definitely climb better /faster with short cranks - I find myself climbing a gear or two higher with short cranks (both the 170’s and 153’s both had the same configuration of the Mountain triple Q-rings). Flats seems to be about same.

My conclusion is that with short cranks, I get less peak power, but I can apply power during the more of pedal stroke.

For those of you (me included) with larger mid-sections. Short cranks may keep your thighs from pressing up on your stomach at the top of the pedal stroke. Probably one of the reasons I feel I ride better with shorter cranks.

Oh..and short cranks have eliminated my knee pains.

Bikesmith is awesome. Mark Stonich is great to work with. I’ve ordered three cranks from him.

northboundtrain

Going from 175 to 170, I doubt very much you'll notice any loss of power when climbing. Besides, you're touring, not racing. However, a 5mm difference in length ends up in a 10mm difference at the top of the pedal stroke (because you raise the saddle 5mm), and this can make a difference in whether you experience knee pain. Touring is particularly tough on the knees because you put in so many hours day after day. Unless you're accustomed to riding 6+ hours regularly, you might find your knees hurting even if you've never had an issue before.

I'm 5'-10", and I've toured with 175 and 172.5, and I plan on going to 170 before my next long tour.

I believe 170 was the common road length for men of average height for many years. I know that 15 or 20 years ago, they came standard on bikes in the 54-56 cm size, whereas 172.5 is now the norm. The move to longer cranks is probably due in part to the advent of mountain biking where the increased leverage and slower cadence are beneficial for handling purposes when climbing over rough terrain.

I think that some of the touring bike manufacturers essentially put a MTB drive train on their bikes and just use the same crank length that they would on a MTB. For instance the LHT 56cm comes with 175, and this is something Surly gets wrong I believe.

rhm

I think you are right about mountain bikes and 175 mm crank arms; before that 170 was indeed normal. Earlier, though, people used even shorter ones. Old three-speeds, which were woefully overgeared (low gear around 50") came with 6 1/2" cranks (165 mm). Now that we prefer lower gears, you'd think we'd want shorter crank arms; but instead we have higher ones.

MichaelW

I switched from 170 to 175 because they came with the bike. I prefer 170 with a higher cadence and lower gear ratio.
There is no reduction in power, just a difference in pedalling style.

ricohman

The Shimano crankset can be ordered with 175mm or 170mm.
I chose the 170mm set for the reasons I stated in my first post.
I can't figure out why this makes a 10mm difference at the top of the stroke though. If the seat is raised 5mm to compensate, shouldn't everything be essentially the same?

northboundtrain

No,

If the crank is 5mm shorter, then the pedal will be 5mm closer to the bottom bracket and 5mm further from the saddle at the top of the stroke. At the bottom of the stroke it is 5mm closer to both the BB and the saddle, which is why you would raise the saddle 5mm higher when switching to the shorter crank. So now the saddle is an additional 5mm from the pedal at the top of the stroke. Thus, the 10mm.

supersport

I went the other way and changed from 170 to 175 on my road bike. I noticed a distinct difference. I like climbing and liked the feel a lot better. I have a 36in inseam, so kinda long legs. Around the same time I was using a CX bike for commuting that had a compact crank and 172.5 arms. Couldn't tell if the difference in feel was due to the bike or the cranks.

LeeG

it's all personal preference. Your body will adjust the crank arm length. The comments "you won't notice the difference" are kind of silly given that your legs are familiar with a particular range of motion and if you change that range you will notice it. I notice seat height differences of 1/8". Whether you pedal at higher cadence or not won't be much affected by crank length as much as your intention to pedal at a higher cadence.

arctos

My earliest road bike over forty years ago had 165 cranks and my size 14/49 feet were not happy. A US Road Race Champion I rode with suggested moving to 177.5 Campy cranks. I used them for years on my road, touring and tandem bikes and loved them.

With the advent of mountain biking I extended to 180mm cranks and continued happy into the present on all my bikes. It has worked for my foot size and has kept my knees happily spinning at a high cadence. A bit of extra leverage in the steepest and loose going while touring off pavement has been noticeable. It has worked for me.YMMV

foamy

My roadie is 174mm and on the advice of the builder of my tourer, when to 170's. I never really noticed a difference. Seems to work just fine. As far as keeping cadence on tour, well, I didn't bother. That cadence counter is a slave driver and I was out to just have fun. That seemed to work too.

rhm

I agree with almost all of that. But let's distinguish preference from what you're familiar with. If you haven't tried a wide range of crank arm lengths, you don't really have a preference. You don't know what you like, you only know what you know. In common parlance we may not distinguish between preference and familiarity, but they are not the same thing.

You are right, I was silly to say "you won't notice the difference." I do notice a difference of 5 mm, and I believe most of us would. My point is no one need worry about a 5 mm reduction in crank arm length. Most of us would be fine with crank arms 20 or 30 mm shorter and some of us would be better off that way.

On their own testimony, Arctos and Supersport, who have long legs, prefer longer crank arms. That makes a lot of sense. Shorter people would be better off with shorter ones.

Crank arm length is extremely forgiving. People can ride a bike with a less-than-ideal crank arm length. In fact most of us do.

wologan

I've done 15,000km on 152.5mm cranks, and I'm 6'2". Love them. It allowed me to use 20 inch rims, whilst maintaining a sensible cadence. Thus saving weight on the wheels, frame and the cranks, and allow more space for panniers and gear.

You need to be a bit carefull about which cranks to choose though. Some of these new Shimano hollowtec varieties are a bit too hollow.

You could go for a Schlumph mountain drive, with a nice short crank, and do away with all that irritating gear cabling/deralleur nonsense.

All the best.

sesmith

Agree completely. I have 3 toad bikes with 165, 170, and 175 mm crank arms respectively. I notice the difference when switching between the bikes, but adjust within minutes. I'm 5'9" with a 32" inseam and the 175 feels the least ideal, but I rode that bike for years without knowing it was not ideal ( I got the other 2 bikes more recently) and ride the bike with the 175 crank arms almost twice as much as the other 2 bikes combined. If I ever have a reason to replace the cranks on that bike, I'll switch to 170's but won't switch them just because of the size.

LeeG

I'm not sure what you are saying, that some people have preferences and some don't? Maybe the miscommunication comes from an unstated meaning of what "difference" is being talked about.

You have a preference for very short cranks that is outside the bell curve. Your statement that "most of us would be better off with cranks 20-30mm shorter" isn't supported by my experience cycling and observing a range of cyclists. That may be your preference but I don't see how you can say it's universal.

rhm

Yes, exactly. If you have actually tried both A and B, you may have a preference between them. If you have only tried A but not B, you do not have a preference. You may have a prejudice, but you do not have enough experience to have a preference.

What bell curve?

If you plotted a bell curve tabulating all riders' leg lengths to the crank arm length they are actually riding, you would find the shortest riders use the longest crank arms, and the tallest use the shortest. Would your interpretation be that crank arm preference is inversely related to leg length? My interpretation would be that preference cannot be an issue if all crank arms are the same size (170 mm).