kjmillig

I'm 5'9" with a 30" inseam. I'm wanting to start doing some occassional loaded touring, and most of it for a while will be SE Texas flat roads with some central Texas small-to-medium hills.
Given my inseam, should I stay with 175mm cranks or consider 160mm, or is crank length mostly just personal choice?
I'm thinking of going with a 48-38-28 triple crank. A 42-32-22 has crossed my mind, but 22 seems awfully small for road touring.

NoReg

try multiplying your inseam by .21, or .216. Thanks to Zinn. That should at least give you a ballpark.

adun111

Were you planning to do fully loaded touring? If so, consider the 42-32-22. What kind of gearing do you have with your current cranks?

kjmillig

I don't understand. 30 x .216 = 6.48. What does that number represent?

kjmillig

Yes, I want to do loaded, self-contained touring. My old Raleigh Wyoming still has the advertised "touring geometry" 52-42 chainrings, which is fine for commuting, though I rarely use the 52.

kjmillig

Any other thoughts? I'm planning on ordering this week.

tuz

I think 42-32-22 is great for loaded touring. You'll thank the granny on long ascends. Fine tune the steps and range with the cassette. Something like 13-32 seems good. You can always put a 44 as modern derailleurs can take up to 22 teeth change, or take a 12-32 cassette if you're worried about top speed.

About crank length. Yes you'll find lots of formulae like proposed above. Peter White cycles proposes 18.5% of inseam. In the above your 6.48" = approx 165mm crank length. Sadly they are quite arbitrary. It should really be a function of the ratio of femur to tibia length, or something of the sort.

Crank length determines 2 things. First, longer cranks mean more knee flex due to larger amplitude movement and potentially uses your knee more. It makes it more difficult to spin high cadences. Second longer cranks mean more leverage, which is important in climbing or for max power transfer (such as in TTs).

So short cranks are easier to spin but have less leverage. However note that the difference in leverage between 175 and 165mm is only 6% which is no big deal. I'm guessing the difference in knee flex is not so large as well.

So I guess to really know you have to try a few lengths. Sadly this is not practical. For a man your height 170mm would be standard. I personally favour short cranks I would maybe go 167.5 or 165mm since we spin a lot and low gears are used for hills in touring. But 170 or 172.5mm should be ok, and if you're used to 175mm go for it.

cachehiker

6.48 inches = 164.6 mm. If I recall correctly the formula is supposed to use the pubic bone height. I wear a 30 inch inseam but my pubic bone height measures about 31 inches. The formula says I should be using 31*0.216*25.4 = 170mm cranks. When touring and commuting, I spend more time spinning than mashing and ride in street clothes more often, so slightly shorter 167.5mm cranks seem to work a hair better for me.

BigBlueToe

I climbed the North Cascades Highway over Rainy Pass and Washington Pass this summer, pulling a Bob trailer, with loaded front panniers and a rack trunk on the back. I installed a 26 tooth granny gear before I left (replacing the 28.) On the ascent I was constantly wishing I had a lower gear. If I had a 22 tooth granny, I wouldn't have suffered so much.

acantor

I have never met anybody who complains that their lowest gear is too low! You will appreciate an ultra-low "bail-out" gear the first time you find yourself climbing a long, steep hill.

Sebach

You might also consider a custom "Trekking" crankset, which I guess is normally 46-36-26. Now where the custom comes in is where you swap out the granny 26 for the real granny: 22. This would give you a set of 46-36-22. Decent high and a solid granny if coupled with an 11-32 cassette.

Just a thought.

As for cranklength, I rode 175mm's last summer when I crossed Canada. No problems. When I bought a new crankset, I switched to 172.5mm on my tourer just because it was available (old one went to my #2 bike) and barely noticed it. Even after being in the saddle for 3 months straight and getting to really know my bike well, I hardly could tell anything had been changed.

kipibenkipod

I have 175mm and now I understand why I have hard time keeping the cadence high.
I have 34'' inseam, so the formula gives 86*0.216=185 and 86*1.85=160 - go figure...
I think I need to go down a step or two to check things out.

cyccommute 

The 42/32/22 with a 12-34 is a good crank for touring but for everyday riding it's lacking. The gearing is a bit low for flat country riding and you'd probably spin it out quite easily. I'd suggest a Shimano Trekking crank like this one from Nashbar, kjmillig. At $45 and the cost of an Octalink bottom bracket you can't beat it. Pair it with an 11-34 cassette and you'll have a gearing system that does well unloaded and does well loaded. If the Trekking set doesn't have a low enough gear, you can change the inner to a 22 easily. It only comes in 175mm, however

I used to think that crank arm length was very important but I'm not so sure anymore. If you have short legs (your's aren't) it might be more important but for average size, I never found it to be that critical.

SteveA

I'm not sure about your math...

34inches * 25.4mm/1-inch = 863.6mm inseam * .216 = 186.5 mm

or

34inches * 25.4mm/1-inch = 863.6mm inseam * .21 = 181.356 mm

Bikepacker67

For me anyway, the best gear combo for touring is 44-32-22 X 11-34
That gives you from 17 (you can climb walls) gear inches up to 108 (which is around 30mph at a 90rpm) gear inches.

* on 700c wheels.

acantor

My setup is an ultra-wide range 48-34-22 x 12-34. Occasionally it is tricky finding the "perfect" gear in the mid-range, but I don't mind. It's a consequence of having such a wide range of available gears. This setup is ideal both for climbing "vertical wall" hills and blasting across flatlands with the wind behind me.

niknak

I don't think that will work. Trekking cranks have a 110/74 BCD, which prevents you from using a 22T chainring, which is made for a 58 BCD spider. You can, however, use a 24T chainring made for a 74 BCD spider. Close enough.

https://sheldonbrown.com/gloss_bo-z.html#bcd

Sebach

I was thinking more along the lines of a MTB Shimano M580/M581 crankset combination, where both (standard MTB triple and Trekking triple) use a 64/104 pattern. But yeah, if sticking strictly with road cranks, a 24 tooth granny combined with an 11-34 cassette in the rear would still be a good wall climber too.

FlyingAnchor

This is exactly the thread I have been looking for, woo hoo.

I have been seriously looking at changing out my front gears, currently 52/42/30 for a 46/?/24. I ride an Agio recumbent so going to 22 would be a little slow to not fall over.

I expect to go into my LBS and see what they have or can get. Maybe I'll go with 165mm cranks as I have the same 30" inseam at 5'6 1/2".

Thanks all.

Steven

kjmillig

Using the femur bone measurement technique, I need about a 162mm crank arm. I've been looking at a Sugino XD300 with 165mm arms and 42-36-26 rings, BCD 74/110 as an economical choice. Is 24 the smallest chainring I can put on it?

seeker333

yes

lighthorse

kjm,
My choice is to keep all of my cranks the same length. I want to maintain the same cadence when touring as when I am training. Whatever fits you on your riding style now without causing knee problems is what you probably should use for touring.

I used a standard Ultegra setup for my tour across the Southern Tier: 52/40/30 crank with 12-27 cassette. That worked fine for my unsupported tour. This year's trip across the country from Florida to Oregon I used a 48/36/26 with a 13-30 cassette. Again, I carried all of my camping gear on an unsupported tour and found the gearing to be fine for me.
Good luck.

acantor

What this posting illustrates is that gearing is a very personal thing. In the past I have had setups similar to both of the above, and I almost died climbing hills!

When choosing gearing, you choose what makes good sense, and then allow experience guide your decision next time!

FlyingAnchor

This weekend I ordered two new gears for my triple. I had/have 52/42/30, the shop mechanic convinced me that my derailer would handle 52/38or39/24. This way I keep my high speed gear and the steps will work with all the gears. I can't wait to try going up those two hills with the lower gears.
Can't wait for them to come in. whoo hooo
Steven