170- of 175mm Crankset

[Mansie#11]

170mm of 175 mm cranset

Is daar 'n groot verskil? Wat is die verskil?

[Bergbok]

nie te groot nie. 5mm

[Vinnydabutcher]

Crank lenth is usually one of 3 sizes 172.5mm - 175mm or 177.5mm but is not limited to these sizes.

 

The theory goes like this:

 

The longer the crank, the more power you can apply doe to the leverage. However, the longer the crank, the longer the time of muscle movement through the power stroke - thus the longer the muscle stays under contraction - thus more lactic acid produced. The longer the stroke - the slower the candence

 

The shorter the crank - faster cadence - the faster the time under contraction - produces less lactic.

 

Old school theory - if you are short - 172.5mm cranks, med lenght 5`9" - 6`1" 175mm crankts - Tall 6`2"+ - 177.2mm cranks. See what fits you best.

 

I dont agree with - Power rides - long cranks - spinners short cranks but that is how it use to go.

 

You are also more likley to scrape/bash your crank on the ground with longer cranks.

 

I`m 6`1" have alwas ridden 175mm cranks.

[Seeker911]

I have always pondered about this. If you think 5mm is nothing not too mention the difference between say a 172.5 and a 175. Are you actually going to be able to feel the difference if you swop between the two cranks ?

[Mansie#11]

Ek weet nie watter een om te kies nie.

[Tankman]

Ek weet nie watter een om te kies nie.

 

Hoe lank is jy en wat is jou inseam?

 

My eerste bike het n 172mm crank op gehad.

Het dit na n week geruil vir n 175mm

 

Die verskil was nie opmerklik groot nie. n Paar jaar later en ek is nou op 177.2mm en wonder net hoekom ek nie al lank al die 177.2 probeer het nie!

 

Daar was beslis n verskil tussen die 177.2mm en 175 maar nie so groot as wat dit sou wees van n 172mm na n 177.2mm nie.

 

Hou jy van n hoe of lae cadence? Spin of power?

[Mansie#11]

Minder trap en verder ry

[JohnnyReggae]

Quite an interesting topic for me at the moment, mostly due to it being a hot discussion item on the Unicycle forum unicyclist.com at the moment. I didn't realise that the crank lengths for bikes is quite limited, 172.5 - 177.5 ... 5mm

 

With unicycles being such simple machines, crank length is paramount to how you ride.

 

We have much larger jumps in sizes depending on a few things including what style of riding you prefer doing, and personal strength/stamina. I started out Mountain Uni with 170mm, but later moved to 150mm. 20mm was a huge difference in loss of torque and control, but I prefer that length to be honest. Generally cranks lengths used in Unicycling range from 170mm - 110mm, some times even as short as 90mm.

 

Longer cranks for more power for hills or technical downhill, shorter cranks for road riding on larger wheels. Longer cranks do give you more pedal-clips though which can be a b*tch when doing some tricky technical stuff. Had a few that sent me flying

 

At the moment I run with dual hole 150/125mm cranks, so I can swap to shorter crank lengths by simply unscrewing a pedal and screwing it into the short hole. I'm sure something like this could be done on a bike, although your crank length will have to change by quite a lot, more so than anyone has been used to.

[KnobbyMech]

Quite an interesting topic for me at the moment, mostly due to it being a hot discussion item on the Unicycle forum unicyclist.com at the moment. I didn't realise that the crank lengths for bikes is quite limited, 172.5 - 177.5 ... 5mm

 

With unicycles being such simple machines, crank length is paramount to how you ride.

 

We have much larger jumps in sizes depending on a few things including what style of riding you prefer doing, and personal strength/stamina. I started out Mountain Uni with 170mm, but later moved to 150mm. 20mm was a huge difference in loss of torque and control, but I prefer that length to be honest. Generally cranks lengths used in Unicycling range from 170mm - 110mm, some times even as short as 90mm.

 

Longer cranks for more power for hills or technical downhill, shorter cranks for road riding on larger wheels. Longer cranks do give you more pedal-clips though which can be a b*tch when doing some tricky technical stuff. Had a few that sent me flying

 

At the moment I run with dual hole 150/125mm cranks, so I can swap to shorter crank lengths by simply unscrewing a pedal and screwing it into the short hole. I'm sure something like this could be done on a bike, although your crank length will have to change by quite a lot, more so than anyone has been used to.

 

 

So when is uni-cycles going the 29" route?

[JohnnyReggae]

So when is uni-cycles going the 29" route?

They're been there for a long time already I have a 29'er, but I prefer to ride my 26" .... it's more of a DH machine than the 29'er I used to ride a 24" but the 26" is a better size for me. Incidentally I have the same length cranks on both my 26" and 29", which makes the 29'er a little harder to control on the descents and also harder up hills due to loss of torque, but the larger wheel size does allow me to go faster.

[Tankman]

I didn't realise that the crank lengths for bikes is quite limited, 172.5 - 177.5 ... 5mm

 

so I can swap to shorter crank lengths by simply unscrewing a pedal and screwing it into the short hole. I'm sure something like this could be done on a bike

 

It is not only limited to 172.5 and 177mm, those are just the most common ones.

For the bikes you can get 160mm to 180mm and I know of custom 190mm cranks.

 

And it has been done, there are adjustable cranks available giving you 170, 172.5 and 175mm all in one crank.

 

So when is uni-cycles going the 29" route?

 

geez we cant even discuss cranks without the big wheel makin9 an appearance!

[JohnnyReggae]

It is not only limited to 172.5 and 177mm, those are just the most common ones.

For the bikes you can get 160mm to 180mm and I know of custom 190mm cranks.

 

And it has been done, there are adjustable cranks available giving you 170, 172.5 and 175mm all in one crank.

 

As a rule of thumb though what do roadies use, and what do mtb'ers use ?

 

As mentioned the length of crank is paramount to how you ride a unicycle, and coincidently a discussion thread came up on the Uni forum about crank length. One of the guys posted a spreadsheet detailing how various crank lengths dictate a certain riding style based on the size of the wheel in terms of gain ratios. I remember seeing the spreadsheet a while back, but was good to see it again. I've posted it here as a reference.

 

The list starts with a 20", 24", 26", 29", 36" (Geared 24"), 39" (Geared 26"), 43.5 (Geared 29"), and 54" (Geared 36"). The largest actual wheel size is a 36". Geared is using a Schlumpf Geared Hub which has 2 gears, 1:1 and 1:1.5 ratios. This will effectively make a 24" a 36" etc... in terms of distance covered per revolution of the cranks.

 

So I ride a 26" with 150mm cranks which puts it slap-bang in the middle for the best gain ratio for Mountain Uni. My 29'er also has 150mm cranks putting it just in the XC style riding with some Mountain Uni. My 20" trials Uni has 125mm cranks, which can and has been used for Mountain Uni ... but it's not the most efficient Mountain Uni

Edited April 14, 2011 by JohnnyReggae

[Mansie#11]

Ek het finaly die verskil uit gevind!! 175 mm

[bontie]

I just ride my bikes.

 

Recently bought a new bike and it came with 170mm, didn't notice until I saw it bu coincidence after about 1000km...

I remember buying a 2nd hand MTB a couple of years ago, after very long I noticed it had 175mm cranks.

 

Honestly - I don't think there is a big difference...

[Tankman]

You may think that there is no big difference and it might even feel that way if you are not 100% in tune with you setup but there is quite a difference between 170 and 175mm. (Google)

 

Changing cranks in increments of 2.5mm will be less noticeable but changing with 5mm will definitely be noticeable.

 

You are also comparing to different lengths on different bikes with different setups mtb vs road.

 

I have 177.5mm on the racing bike and 175mm on the training bike with pretty much the exact same setup and I can feel the difference.

 

As a rule of thumb though what do roadies use, and what do mtb'ers use ?

 

Dont know if there is a rule of thumb other than you get what is on the bike when you buy it and it is never really discussed when buying your first bike.

 

Road bikes seem to have 172mm on as standard. If we were as short as them Italians that might have been correct but then again mtbikes have 175mm on as standard? I would have said if you manufacture a Large or XL frame dont let it leave the factory with anything less than 175mm crank.

[FC&P2C]

I've got 172.5mm on my 56cm road bike, 175mm on my 54cm tt bike, 175mm on my 17,5" mtb and 180mm on my 24" bmx race bike.

I can honestly don't tell the difference between the different length cranks!