Crank length?

[FOAD]

I am about to upgrade the compact on my Cube Agree 60cm bike to a double.

I am 6'3" with a 32" inside leg.

My current crank length is 172.5, and I have zero knee or other problems with it. My LBS (who are fitting but not supplying the new crank) reckon I should go for a 175 length.

I am concerned that the extra 2.5mm may be cause issues I don't have now. Is 175 excessive for such relatively short legs on a tall bloke?

 

[ianrauk]

have a look at 2.5mm on a ruler... can you honestly say it will make a difference?

*waits for jimboalee impossible crank size equation to appear*

 

[I am Spartacus]

well.... we alll know that few mill on seat height can be a sod...
so I'd say if no problem.. stick with 172.5

I am 6 2 with 34 inside leg and have 175 cranks.. but have used shorter ones , I own up to that

 

[SimonC]

well.... we alll know that few mill on seat height can be a sod...
so I'd say if no problem.. stick with 172.5

I am 6 2 with 34 inside leg and have 175 cranks.. but have used shorter ones , I own up to that

Same here, 6 1 and have 175mm cranks, but I used to use 172.5, and only changed to 175's cos I got a Campag chainset on the cheap. Cant tell the difference, and as earlier poster said, have a look at 2.5mm on a ruler. Its bugger all!

 

[Chrisz]

As above! I'm 6'3" and have always used 172.5mm cranks up until two weeks ago when I replaced mine with some 175mm Fulcrum RRS's - can't tell any difference (apart from the sexyness of them )

 

[HLaB]

I'm just reading an interview with the British TT champ, Michael Hutchinson

Hutchinson uses 172.5mm cranks. Shouln't a bigger rider like him ride 175s?
"I don't think crank length makes a flying toss of difference" he asserts. "If someone had fitted different cranks to my bike before the National 25, I don't think I'd even have noticed. Besides, if you use cranks that are 5mm shorte it makes yo much lower at the front. Which if you've got a large beer gut and you're going for a Boardman position, helps."

 

[I am Spartacus]

Actually the main point of this thread is getting rid of a useless compact to a useable double!

 

[FOAD]

Actually the main point of this thread is getting rid of a useless compact to a useable double!

Not really, but you are absolutely right! It's cool for the big climbs but shite when my mates are leaving me for dead going for signs as I spin out at 34mph!

Never liked it from the moment I had the compact tbh.

 

[gavintc]

An 11-50 is a pretty high gear. Not many can spin this out, unless your going downhill.

 

[FOAD]

My back end is 12-27 and spinning out 50-12 is pretty easy, and I don't mean that in a cocky way, cuz I aint too fast, I just mean that when we race for signs 34 mph or there abouts is the limit, and on a slight decline that is easy to achieve when just giving it a bit of effort, especially as I am a fat b'stard.

 

[Crankarm]

I've a 29" inside leg and have 175mm and 172.5mm cranks on different bikes. I can't tell the difference. You will be fine. It is more critical to get the seat position and cleats correctly positioned to avoid knee problems.

 

[jimboalee]

If you read up on the subject by doing some clever Googling, you will find Crank length is related to the height of your Hip ball joint.

With bare feet, get someone to measure the height of your Hip ball centre.

Divide this measurement by 5.48.

Hey presto.

My hip ball centre is 927mm. That gives 169mm crank length, so I went for the vanilla flavour 170mm jobbies.

I didn't really, the bike I bought had this size as standard to suit the rider the frame was sized for.
Cunning hey, these chappies at Dawes.

 

[Chrisz]

Personally I'm a little dubious about the hip ball centre thingi because - you can't actually feel the ball of the hip joint (unless there is something seriously wrong!!), what you can actually feel sticking out at the hip is a projection called the great trochanter of the femur which is not necessarily level with the ball of the hip joint.

 

[lukesdad]

Missing the point here, I always thought crank lengths are nothing to do with the riders height, its purely a torque/ revs/power thing riders who spin use shorter cranks power riders who stamp on the pedals delivering more torque use longer cranks am I wrong?

 

[SimonC]

If you read up on the subject by doing some clever Googling, you will find Crank length is related to the height of your Hip ball joint.

With bare feet, get someone to measure the height of your Hip ball centre.

Divide this measurement by 5.48.

Hey presto.

My hip ball centre is 927mm. That gives 169mm crank length, so I went for the vanilla flavour 170mm jobbies.

I didn't really, the bike I bought had this size as standard to suit the rider the frame was sized for.
Cunning hey, these chappies at Dawes.

All assumes that you can make these measurements to the degree of accuracy required, without resorting to surgery to get the end of the tape onto the centre of the hip joint