Shorter Cranks - What a difference! :D

Dmak

First ride on the bike today since I replaced my 175mm cranks with 170's and wow 5mm really does make a lot of difference! I went out, took it fairly easy only to return home to find I'd beaten 3 of my personal bests on Endomondo :shock:

I figure it's worth sharing here given the difference it's made. The vets clearly know it all but for beginners it's defo food for thought.

I'm just shy of 6' and my inside leg is 35 inches. I like to spin the cranks and not grind, 90-100rpm typically. Much more comfortable ride for me and the hip joint pain I've been suffering with lately was present but very faint, I figure and hope this should fade completely now.

New Sora compact chainset cost just £34, money well spent. Glad I bought a bike with a value groupset!

wilshawk

cool, I may try this sometime

rozzer32

Did you drop your saddle to compensate?

Might find that if you didn't your saddle in now closer to the correct position which is why it feels so different.

inseine

Did you drop your saddle to compensate?

Raise his saddle.....

cougie

I found one of my best rides coincided with getting new sunglasses.. I rode like Big George that day !

danowat

cougie wrote:

I found one of my best rides coincided with getting new sunglasses.. I rode like Big George that day !

Look, at least tell us which sunglasses, and who the F is "Big George"

rozzer32

inseine wrote:

Did you drop your saddle to compensate?

Raise his saddle.....

Ahhh yes you would be correct :oops:

Pross

danowat wrote:

cougie wrote:

I found one of my best rides coincided with getting new sunglasses.. I rode like Big George that day !

Look, at least tell us which sunglasses, and who the F is "Big George"

I think he meant Boy George

danowat

Pross wrote:

danowat wrote:

cougie wrote:

I found one of my best rides coincided with getting new sunglasses.. I rode like Big George that day !

Look, at least tell us which sunglasses, and who the F is "Big George"

I think he meant Boy George

In that case, thats a proper Freudian slip

Dmak

rozzer32 wrote:

inseine wrote:

Did you drop your saddle to compensate?

Raise his saddle.....

Ahhh yes you would be correct :oops:

I reset it to 88% of my inside leg from the BB, rode for a bit and then lowered it a touch.

I shouldn't imply that this would be good for everyone, it's a very personal thing. Most people are probably using the correct cranks but if something doesn't seem quite right it's well worth looking into. Crank arm length calculators seem give wildly different results. Below, however seems to be the most sensible guide.



"BikeDynamics recommends that you refer to the TA graph above for all inseams above 74cm, and use the Kirby recommendation below that."

This tells me I should use 172.5mm cranks but as I spin fast, a size shorter is probably more suitable, those who like to grind a bigger gear may want a size up.

http://bikedynamics.co.uk/FitGuidecranks.htm

http://www.myra-simon.com/bike/cranks.html

cougie

Oakley eyejackets - and George Hincapie of course....

The benefits didnt last longer than one ride though - so it will be interesting to see if you still notice the difference in cranks on the next few rides. I cant tell any difference with them.

amaferanga

One of my road bikes has 175mm cranks, the other 170mm cranks. I can't tell any difference. There's also no noticeable difference in the power I can output on each bike.

Maybe you had convinced yourself it would be better so rode harder to prove that to yourself?

jgsi

cougie wrote:

Oakley eyejackets - and George Hincapie of course....

The benefits didnt last longer than one ride though - so it will be interesting to see if you still notice the difference in cranks on the next few rides. I cant tell any difference with them.

My Oakleys lasted about 2 rides before the effect wore off...

this is classic case of clutching at straws to think how to go faster.. and all it was in the end was getting the seat height correct to pedal more efficiently.
both my bikes have diff size cranks ... the slower one is usually the heavier bike by about a 0.00012 mph.


if I see a SRAM red chainset for under 150 and it was only in 170... dont think I'd go aw shucks , not for me then.

(the spin bike, I have to use during working hours ... has 165's)

Pross

amaferanga wrote:

One of my road bikes has 175mm cranks, the other 170mm cranks. I can't tell any difference. There's also no noticeable difference in the power I can output on each bike.

+1

cougie

I saw a thread this week that had figures that the difference between long and short cranks was something like 1% ? That sounds about right and certainly in my experience it was too small to notice. Human performance fluctuates far more than that anyway - so it could even have been you were having a good day.

Dmak

amaferanga wrote:

One of my road bikes has 175mm cranks, the other 170mm cranks. I can't tell any difference. There's also no noticeable difference in the power I can output on each bike.

Maybe you had convinced yourself it would be better so rode harder to prove that to yourself?

Not at all, I went out admiring the view and took it fairly easy. I was pretty shocked when I got back to find I was faster than ever, without even trying to be.

The main thing for me here is sorting out hip pain and so far so good.

rozzer32

You probably has a tailwind for most of the ride

Dmak

Too many doubters in this forum. No matter what you say it must be wrong!

If you don't notice a 5mm difference in crank length, GOOD FOR YOU! It's a 10mm change in the overall diameter of the pedal rotation.

If the correct crank arm length for the rider isn't important, how come they're supplied in 2.5mm increments?

I will add that I did a huge chunk of miles on road on an MTB with slicks and 170's. 45 miles commuting daily, this was my primary training for my recent stint of cycling, the muscle and tendon structure I have developed is suited to this pedal stroke. Then I bought the road bike with 175s. Instantly something didn't feel right with my new bike (Sept) and then the hip pain appeared. At that point I thought cranks were a universal length, then I learnt they weren't. Can't believe it's taken over 7 months to fix the issue.

Like I said before, this info is really for those new to road cycling. Given that the cranks are how you get the power into the bike to push you forward for thousands of miles I would hazard a guess that the correct length is ABSOLUTELY CRUCIAL. End of rant :P

P_Tucker

Dmak wrote:

Given that the cranks are how you get the power into the bike to push you forward for thousands of miles I would hazard a guess that the correct length is ABSOLUTELY CRUCIAL. End of rant :P

See, theres your problem. You don't know anything, but you just assume something then deny any suggestions that you might be wrong. This is how religion started FFS,

saintdracula

P_Tucker wrote:

Dmak wrote:

Given that the cranks are how you get the power into the bike to push you forward for thousands of miles I would hazard a guess that the correct length is ABSOLUTELY CRUCIAL. End of rant :P

See, theres your problem. You don't know anything, but you just assume something then deny any suggestions that you might be wrong. This is how religion started FFS,

Thing is, it could also be a conjecture...or an axiom...or a theorem

Dmak

P_Tucker wrote:

Dmak wrote:

Given that the cranks are how you get the power into the bike to push you forward for thousands of miles I would hazard a guess that the correct length is ABSOLUTELY CRUCIAL. End of rant :P

See, theres your problem. You don't know anything, but you just assume something then deny any suggestions that you might be wrong. This is how religion started FFS,

Continue.