Crank arm length and gearing

[Arron_w]

Just after a little advice how to change my gearing to suit my needs I have had a operation on my quad muscle making it really week so need to change my setup to accommodate I am putting the miles in on my turbo and on the road but as soon as I hit the cat 4'z again I really struggle


I'm currently running Ultegra dbl chainset 175cm. 53/39
And 11 / 28 on the rear


The options I have increase the rear cassette to a 12/30

Sell my chainset and buy a compact

I've also been advised to get a 165 crank lenth to increase cadence

I've had so much mixed results just after some solid advice befor wasting money

 

[MrJamie]

I would imagine the higher cadence - shorter crank would assume easier gear ratios too, otherwise shortening the crank would just be giving you less leverage to turn the chainset, putting more strain on your muscles I think? It'd also affect the range of motion in your legs and possibly your bike fit too, which I am not qualified to understand Assuming it's a lack of strength in the quad, I'd guess youd just want to gear down, but more drastically than 28 to 30 on the rear.

I'm sure the cleverer folk will be along with some actual good advice!

 

[Shut Up Legs]

I'm no expert on this, but I'm guessing decreasing the crank lengths by 10mm would significantly change your overall bike fit. Perhaps you would be better off simply using lower gears? Initially, this will be difficult, because you'll be expending more aerobic effort, but persevere and it will become easier.

[edit] 'cm' changed to 'mm' - oops!

 

[themosquitoking]

I would imagine the higher cadence - shorter crank would assume easier gear ratios too, otherwise shortening the crank would just be giving you less leverage to turn the chainset, putting more strain on your muscles I think? It'd also affect the range of motion in your legs and possibly your bike fit too, which I am not qualified to understand Assuming it's a lack of strength in the quad, I'd guess youd just want to gear down, but more drastically than 28 to 30 on the rear.

I'm sure the cleverer folk will be along with some actual good advice!

^^^ This sounds sensible to me.

 

[RWright]

crank lengths are in mm

 

[Rob3rt]

Shorter crank arms won't alter your cadence.

If this is a medical issue (which is it is) and not you just being a pussy, you are forgiven for buying a bigger cassette and if you still struggle, for fitting a compact chainset!



Or you could just avoid the hills for a while longer until you regain more strength!

 

[RWright]

Make sure your rear derailleur can handle a 30 tooth cog.

 

[Nigelnaturist]

Shorter cranks would increase the overall gearing.

 

[grumpyoldgit]

Shorter cranks would increase the overall gearing.

Not sure how.I thought that it would decrease leverage,therefore increase effort required,but the gearing remains the same.

 

[Rob3rt]

Not sure how.I thought that it would decrease leverage,therefore increase effort required,but the gearing remains the same.

Yup, gear inches would remain the same!

 

[Osh]

i've been thinking of switching from 172.5 to 170, to nudge the seat a bit higher, and then use a longer stem to improve aero position.

It's probably be cheaper to just wear a nappy under my bib shorts though

 

[grumpyoldgit]

i've been thinking of switching from 172.5 to 170, to nudge the seat a bit higher, and then use a longer stem to improve aero position.

It's probably be cheaper to just wear a nappy under my bib shorts though

Serious question,do you really think you will notice a 2.5mm increase in height?

 

[Osh]

it's a fair question. I think i would notice it...i set my seatpost a smidgin (maybe 5mm?) too high the other day after a clean, and although it was a stretch on the legs i preferred the higher/more forward position i got on the bars... It's surprising what a difference these minimal adjustments can make!

 

[Osh]

i wouldn't bother making the change except that i'm after a new chainset anyway, so trying to work out what crank length would be best. 167 seems a bit too short...but again, it's just a difference of a few mm.

 

[Rob3rt]

The best crank length will depend on your anatomy. Particularly the proportions of your legs.