I need shorter cranks, but by how much?? (155mm vs 160mm)

[pigman]

For me, I can really spin short cranks and wind it up on the flat, track-rider style. However, as soon as I climb, I can't maintain that spinning needed to make equal progress. As a rider, I am of heavier build and have breathing difficulties, so the slower tempo and bigger muscles make it easier to grind. Maybe if I had "trained" myself to the different style of riding needed, it may have worked, but any thoughts of training went when I stopped racing 30+ years ago.
My style is more Ulrich than Armstrong (can we mention them?)
Interestingly, I am not a 53x12 type of rider. The biggest gear on my carbon bike is 48x12 and on my winter bike 46x13

 

[Nob]

I’ve been riding 177.5’s since 79 & not going to change anytime soon as feel comfortable on what I know works. The minute you start meddling with lengths is the time you start getting ache pains knee trouble etc..... stick with what works especially as we age smaller chainrings of course

 

[Ugo51]

Very nice post to read, 2manyoranges.
Having shorter cranks will definitely help upping the cadence, as pigman suggests. I don't much climbing, if any, so I don't anticipate it being a problem. Although it's interesting to think that at home in Italy, I run 170mm cranks on my MTB and never felt the need for shorter cranks. Probably because the longest flat stretch it's 1km or so, and I'm 99% of the time either climbing or descending

The issues I want to address with shorter cranks (beside my personal curiosity) are that I want to be reduce load on the knees, and also reduce fatigue. What made me click and really set me off about wanting shorter cranks is that I am afflicted by constant fatigue and tightness in my quads, which is not explainable by the amount of riding I do.
It seems that the high accelerations resulting from running too long cranks, can be responsible for fatigue. I already have the seat almost fully forward, and I think - think! But I can't be sure - the seat height is right.

Anyway, especially as I am coming from 170, I think I will stick with 160mm. 155 would probably be too short, even for me.
I will keep you posted. I'm very curious to see how it will feel to change crank length. I've always ridden 170mm so who knows? Maybe I'll hate the 160mm.

Edit: SpaCycle just email me saying the 160mm cranks are out of stock

 

[2manyoranges]

Ah....stock....the impact of pandemic....try SJS and their Thorn cranks. I use these for young people - good cranks.

 

[dg01]

having too long cranks on the road means you get dropped on hills,

And here I was thinking I just had had too many pies (as distinct from 2manyoranges)...

I also concur with Ugo51 - good post to read.

 

[Ugo51]

I decided to try the 160mm cranks first.
155 might be too short even for my legs.

Also, contrary to what I remembered, I still had a few mm left in the seat rails to move the seat forward, which already helped.
There is a bit too much weight on the front now, but the pedaling is already easier (or just different, which might seem easier just because it makes me engage the muscles in a lightly different way).

​

 

[2manyoranges]

That’s good to hear. I did a bike fit with someone who had given up riding because of knee pain. When I saw her on the bike I knew exactly why - saddle way too low, way too far back, and handlebar far too rotated to the rear. All of those sorted, and she could immediately ride without any pain, and it cost.....nothing....hurrah!

 

[insanefred]

Lots of recumbent and velomobile riders run 155mm cranks, which seem to help for the different sort of riding - more spinning high cadence and low gears. Have a look at bentrider.com, lots of advice over there.

 

[fastpedaller]

I tend to spin, and used to time trial mostly on fixed wheel. I bought some second-hand good quality (stronglight) cranks which was all I could afford at the time, and they were 150mm! They served me well. It felt really odd when changing from 170mm on my other bike , and took a few rides to re-accustom. With hindsight, the 150's were probably too short for me. I now ride 165's and find them a good compromise. I don't understand the logic 'time triallist should use shorter cranks to get a better tuck' because the rider (with shorter cranks) will be slightly higher in teh saddle - maybe presenting more surface area to the wind? All pretty academic anyway, as surely pedalling efficiency 'outranks' a very small aero advantage?

 

[Ugo51]

In the end I got a 160mm chainset from Spa Cycle, but I was very disappointed, and I sent it back.
It's a shame, because it's essentially the only 160mm on the market, so now the choice is between 155 and 165mm.

I found these: https://www.ridewill.it/p/en/brn-be...y-racing-155-mm-bcd-110/136026//?adv=s&zone=2

But I don't know whether to splash and the get BOTH 155 and 165mm and see which one fits better, or just the 155.
165mm feels too close to the 170mm I am using currently, not sure whether I would feel a difference, but as fastpedaller says, it might be the right compromise.
I'll wait to get the money back from Spa, and then I'll place the order.