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Short Crank Curious…

SylentK

Turbo Monkey
Feb 25, 2004
2,305
861
coloRADo
Super interesting. Remind me where you live? I really think elevation matters quite a bit on this. Is this co front range? Or high country.

Def not trying to make a dick swinging content, just curious about what folks run.

out here (Sandy, ut), we usually climb 2400 vert laps @ 7.5mi ride distance per lap (4.5mi up, 3mi down). But it’s fairly low (most rides range from 7k-11k, usually 10k or lower top out) compared to many Colorado rides.

I just switched from 11 speed (32 x 11-46) to 12 speed (32 x 10-51) on my bikes, and was super stoked at how much less demanding the hardest and most technical sections of climbing became by adding essentially 1 more shift easier if a gearing.

I would imagine 28t front is about 1 more shift, so I would guess folks running this are riding looser or more chunky trails than me?

fair assessment? And curious how the short crank folks fit into all this, as next drivetrain im likely to try some 165’s on the big bike.
Yeah man, I think you're on it! I think it really comes down to the rider and where they are with fitness, mobility, strength, all that blah. So do what YOU feel is right.

Yes, I'm in Fort Collins. Front Rangy, Northern Colorado, But similar to the likes of Golden or like Colo Springs. Not quite "high altitude" as we're all around 5280' in elevation. And used to it. I'd consider High Altitude at 8K feet.

tl;dr - IMO: the largest gear ratio should be your "bail out" gear. Not the one you constantly use. Unless that's where you're at. Feel free to use it all the time. It doesn't matter. Have fun. Ride your bike! Stretch your limits!

Long story: Remember the days of a triple front chain ring? Well if you don't, let me explain: you typically wouldn't use the small chain ring unless absolutely necessary. Now, this could be used just once in a ride on a crazy tech uphill. Or used the entire ride up the hill. I have many years on both scenarios. Only you know when you need to use this gear. I have many fond memories of bros trying to go UP a gnarly section and having fun with little competitions on that. Just as much as we'd do going down. No one ever thought of comparing to crank length or cassette to front chain ring ratios. You just had fun.

Now, we have just one front chain ring. I rarely find it being in the smallest cog. You know, the fastest of all gear ratios. Usually if it's we're on the road going back to the car. But I find I'm in the biggest cogs most of the time. What size of front chain ring is where I think about things. Usually it's a 30t. Enduro racing it's 32t. At home because I may be hung over, hurt, recovering, trying to win "crazy climb show with the bros" 28t. Just cuz. Like I said, you never really use the smallest cogs but definitely the biggest cogs.

Going from a 26" rear wheel to a 29er definitely effects the gear ratios. So feel free to experiment. In my experience I'm going down in gear ratio, hence the 28t chain ring. I know, I suck.

Your mountains may vary. YMMV?

It's all good. Have fun with what you brung.
 

Jm_

sled dog's bollocks
Jan 14, 2002
18,943
9,623
AK
The hardest local "rideable" climb is 1,240 freedom-feet in 2.34 freedom-miles. It says the average grade is 10%, but that's not right, it's mostly in the 20s. It's definitely a hell of an effort to keep a decent speed on it. It's not the steepest anything, but to keep it going over that distance at the constant grade is pretty tough without resorting to single-speed/standing slowness. 30-42 works fine for me here, although 30-40 or 30-44 isn't a huge difference either. I lost the KOM while sitting here with my peg-leg, but I don't think easier gearing means much. Gearing is largely a matter of conditioning IME, that's how SS riders go up stuff and going easier in gearing doesn't make me faster or make climbs suddenly possible. There's a range that if you go too far, this doesn't hold true, but people are generally a lot more adaptable than they give themselves credit for. If you want to get better, it's going to require bootstraps. Or an ebike.

 

Jm_

sled dog's bollocks
Jan 14, 2002
18,943
9,623
AK
Yeah man, I think you're on it! I think it really comes down to the rider and where they are with fitness, mobility, strength, all that blah. So do what YOU feel is right.

Yes, I'm in Fort Collins. Front Rangy, Northern Colorado, But similar to the likes of Golden or like Colo Springs. Not quite "high altitude" as we're all around 5280' in elevation. And used to it. I'd consider High Altitude at 8K feet.

tl;dr - IMO: the largest gear ratio should be your "bail out" gear. Not the one you constantly use. Unless that's where you're at. Feel free to use it all the time. It doesn't matter. Have fun. Ride your bike! Stretch your limits!

Long story: Remember the days of a triple front chain ring? Well if you don't, let me explain: you typically wouldn't use the small chain ring unless absolutely necessary. Now, this could be used just once in a ride on a crazy tech uphill. Or used the entire ride up the hill. I have many years on both scenarios. Only you know when you need to use this gear. I have many fond memories of bros trying to go UP a gnarly section and having fun with little competitions on that. Just as much as we'd do going down. No one ever thought of comparing to crank length or cassette to front chain ring ratios. You just had fun.

Now, we have just one front chain ring. I rarely find it being in the smallest cog. You know, the fastest of all gear ratios. Usually if it's we're on the road going back to the car. But I find I'm in the biggest cogs most of the time. What size of front chain ring is where I think about things. Usually it's a 30t. Enduro racing it's 32t. At home because I may be hung over, hurt, recovering, trying to win "crazy climb show with the bros" 28t. Just cuz. Like I said, you never really use the smallest cogs but definitely the biggest cogs.

Going from a 26" rear wheel to a 29er definitely effects the gear ratios. So feel free to experiment. In my experience I'm going down in gear ratio, hence the 28t chain ring. I know, I suck.

Your mountains may vary. YMMV?

It's all good. Have fun with what you brung.
Yeah, but some of that triple stuff was just f*cked. 1:1 (22x32, 34 or 36) was just too low to keep moving forward in a lot of climbing situations. With low anti-squat bikes and big travel front forks, this was basically unmanageable IME. It wasn't a "bail out gear", it was pretty much unusable IME. 1:2 was generally your steep-ass climb, because you could drop to it with relatively one motion as shit got steep. You downshifted on the big ring and upshifted on the cassette at the same time, to arrive at 1:2, except you kind of lost out on making a decent transition from the middle ring to the insanely easy gearing of the smallest. You also had to often let off the pedals to get the damn thing to shift down to that 22 granny ring, trying to shift under the slightest bit of power on a steep climb could be difficult to impossible depending on the bike and front derailleur tune/geometry.

Anyways, this IME gave you redundancy and stuff outside a reasonable range, on both sides. 1x is a lot better at giving me just what I need.
 

Gary

"S" is for "neo-luddite"
Aug 27, 2002
7,615
5,535
UK
155mm

DSC_0374.JPG

Not mine.
I might be special... But not that special.
 
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Gary

"S" is for "neo-luddite"
Aug 27, 2002
7,615
5,535
UK
Those are the E-bike cranks. Basically just two left hand ISIS crank arms. one threaded for a right pedal thread.
 

canadmos

Cake Tease
May 29, 2011
20,382
19,390
Canaderp
yeah but paywalled... seriously? paying for Blister?!
Everything in the world is going behind some sort of subscription bullshit. Its so sad. :(

These things might only be $3 here, $17 there, $9 over there, but man it adds up if you aren't careful.
 

Andeh

Customer Title
Mar 3, 2020
1,007
981
yeah but paywalled... seriously? paying for Blister?!
I get a lot more value out of paying for them than some of the other shit I pay for. They do proper in depth analysis of stuff, do great head to head comparisons, and I've taken advantage of their personalized recommendations for bikes and skis. Their podcasts are good too. I'm happy to support them. The savings I got on a pair of 4FRNT skis probably covered a few years of subscription alone, and if I get a set of WAO wheels on the next bike with their discount, that'd cover a lifetime subscription.
 

djjohnr

Turbo Monkey
Apr 21, 2002
3,011
1,704
Northern California
These look interesting, although I don't know much about 2024 aluminum. Major bonus for being a pinch-bolt design.

 

StiHacka

Compensating for something
Jan 4, 2013
21,560
12,505
In hell. Welcome!
These look interesting, although I don't know much about 2024 aluminum. Major bonus for being a pinch-bolt design.

Those look nice.
 

6thElement

Schrodinger's Immigrant
Jul 29, 2008
15,926
13,178
Just read about those on PB and came to link them, the negative would be back to a 104BCD spider, so nothing less than 30T possible if required.
 

StiHacka

Compensating for something
Jan 4, 2013
21,560
12,505
In hell. Welcome!
Just read about those on PB and came to link them, the negative would be back to a 104BCD spider, so nothing less than 30T possible if required.
Just put a 60T cassette in the back. The more I look at these cranks, the more I like them. Throw a steel chainring on and you're all set for thousands of miles of riding.
 

HardtailHack

used an iron once
Jan 20, 2009
6,701
5,574
I bought 175mm cranks because they were in stock, they feel nicer than 165mm until I hit them on something when pedaling, but that's due to shit riding style and forgetting I am now on a dually.
 

canadmos

Cake Tease
May 29, 2011
20,382
19,390
Canaderp
I am riding 165 cranks because of clearance on my mullet Titan. I read this article. Then I clicked on the appleman link curious to see what his calculator would tell me to ride. Entered my tibia lenght - boom - 175 mm :D
I'm building a mullet Titan as well and had 175mm cranks on the Spitfire, that I'm going to swap over.

Too low in your opinion?
 

Flo33

Turbo Monkey
Mar 3, 2015
2,063
1,301
Styria
I'm building a mullet Titan as well and had 175mm cranks on the Spitfire, that I'm going to swap over.

Too low in your opinion?
As always, depends. I'm running the dropouts in the lower "high" position. I'm noticing it only on descents in rough off camber stuff. With the 165 cranks I can put in some quick pedal strikes where I had a hard time with the 175s. No problem on uphills though. You should be fine.
 

Happymtb.fr

Turbo Monkey
Feb 9, 2016
1,913
1,268
SWE
Anyone having success drilling and taping forged cranks? If yes which model of cranks did you use?

I am building a 2015 Giant trance for my 12 years old son and would like some shorter cranks. I found those but with only 123mm between arms they most likely will not fit the frame https://www.vpace.de/en/vpace-children-s-crankset-incl.-chainring?number=1001451&c=35
20230128_132856.jpg

Shimanos look like that inside
hollowforgedinternal_ecbb1073c823462f44b03386f52841131abe0201.jpg

Would that be enough meat to drill and tap close to the pointy void?
 

Electric_City

Torture wrench
Apr 14, 2007
1,994
716
I think the old rule of metals is that the holes need to be 3x the diameter apart from each other. In the case of that crank arm, it looks like the hollow part in comparison to the pedal hole would be close to that rule. But it's been 20 years since I took that class, so what do I know.
 
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Gary

"S" is for "neo-luddite"
Aug 27, 2002
7,615
5,535
UK
I am building a 2015 Giant trance for my 12 years old son and would like some shorter cranks.
Shorter than what?
165s are fine for a 12yr old (Fathered many). If he can fit an adult bike he'll be just fine on adult length cranks.
 

canadmos

Cake Tease
May 29, 2011
20,382
19,390
Canaderp
Anyone having success drilling and taping forged cranks? If yes which model of cranks did you use?

I am building a 2015 Giant trance for my 12 years old son and would like some shorter cranks. I found those but with only 123mm between arms they most likely will not fit the frame https://www.vpace.de/en/vpace-children-s-crankset-incl.-chainring?number=1001451&c=35
View attachment 188510

Shimanos look like that inside
View attachment 188509
Would that be enough meat to drill and tap close to the pointy void?
I don't think its a good idea, as aren't Shimano hollowtech cranks two pieces of metal that are then joined together? You might risk compromising that junction.

Plus even if it worked and you got the hole drilled, who has a tap for the reverse threaded side? :edit: ok so Park Tool, at least, has these taps and they are pretty cheap, but quality might be questionable for cutting new threads?
 

Happymtb.fr

Turbo Monkey
Feb 9, 2016
1,913
1,268
SWE
you are right guys, that is not such a good idea...
my buddy who is a mechanical engineer was not thrilled by it! :D

@Gary
I am trying the idea of compensating for a too low BB. The stock bike has a high BB but after putting a 26" at the rear (basically the only fitting wheel I have) and swapping the shock for a 190x51 (from a 200x51), the BB is now crazy low. You will be right to think that I am looking for more problem than I already have :brows: but hey, I am a nerd and think that my son would benefit from a lower BB and also shorter cranks on a bike that should be predominantly used in bikeparks.
I could do simple and put the original shock back and use the 175mm crankset I have in my parts bin. And it is probably where I will end. But for the moment I enjoy contemplating other options ;)
 

Gary

"S" is for "neo-luddite"
Aug 27, 2002
7,615
5,535
UK
the BB is now crazy low.
This needs quantifying.
Plus pics. Even if just to laugh at its seat angle.

Ps. I built my GF a trance a few years ago as an XC bike and slung on 26s f&r. It has my old 165 Saint cranks but it's not low enough that it desperately needs them. She's kinda a novice and never gets pedal strikes. Eventually I'll probably swap the cranks out for lighter shimano 170s and stick the Saints on my capra where they belong.
 

Gary

"S" is for "neo-luddite"
Aug 27, 2002
7,615
5,535
UK
how tall is said 12 year old?
Mine were all somewhere around 5ft by 12.
Youngest is 13 now and just over 5'4" with size 8 feet
ie. She'd have grown out of silly little cranks pretty fast
 

Happymtb.fr

Turbo Monkey
Feb 9, 2016
1,913
1,268
SWE
This needs quantifying.
Plus pics. Even if just to laugh at its seat angle.
There is a picture in my first post, for the moment without headset. The bb was around 31-32cm above the ground. I will update when the headset arrives.
 

iRider

Turbo Monkey
Apr 5, 2008
5,653
3,092
Propaine has a 115 mm crank they install on their kids bikes:

Funn made short cranks, I think square taper though:

An option from Rotor: https://www.kaniabikes.com/zubehoer/zubehoer-20-zoller/tretkurbel-rotor-bcd-104-einfach/143?number=rotor135 0,42 kg&c=43
 

Gary

"S" is for "neo-luddite"
Aug 27, 2002
7,615
5,535
UK
Hard to tell just how low your BB is from that pic. Likewise this isn't the best pic and the rear wheel is raised in the feedback stand so hard to see actual geo and BB height but here's my GFs with 26s and a 140mm fork. It's a size M
DSC_1554.jpg
 

Gary

"S" is for "neo-luddite"
Aug 27, 2002
7,615
5,535
UK
Disappointing Google search result Westy?
Mercan English spelling to blame?
 

pe6u

Chimp
Apr 19, 2013
29
28
I did it for my son's bike, I put 24" wheel in the back of a XS frame, bought old FSA Moto X Gravity cranks (not hollow) and cut them to around 135 mm, he still rides them (now on my old 26 Nukeproof Mega M) and he loves them.
 

Happymtb.fr

Turbo Monkey
Feb 9, 2016
1,913
1,268
SWE
Propaine has a 115 mm crank they install on their kids bikes:

Funn made short cranks, I think square taper though:

An option from Rotor: https://www.kaniabikes.com/zubehoer/zubehoer-20-zoller/tretkurbel-rotor-bcd-104-einfach/143?number=rotor135 0,42 kg&c=43
Porpain might have worked but is out of stock...
I also found plenty of short cranks with square taper but I haven't found a way to fit them to a pressfit frame

Hard to tell just how low your BB is from that pic. Likewise this isn't the best pic and the rear wheel is raised in the feedback stand so hard to see actual geo and BB height but here's my GFs with 26s and a 140mm fork. It's a size MView attachment 188538
It looks nice! How tall is she?
i got a medium frame too