Crank lengths question

[Marcellus]

Currenly i have 50/34 chain rings with a 172.5 crank.

Looking to change to a 54/39 and have been offerred a pair with a 175 crank.

Apart from 2.5cm what's the difference and will i notice?

[lukeyman]

2.5mm..

[Marcellus]

Really 2.5mm??

So unlikley to notice then?

[TheAllSeeingPie]

If you use this you'll be able to compare the two: http://www.sheldonbrown.com/gears/

Going to a 54 from a 50 will require more effort even if you have longer cranks. Are you changing the cassette?

[deadtom]

Marcellus said:

Apart from 2.5cm what's the difference and will i notice?

Marcellus said:

Really 2.5mm??

from this it looks like you thought the crank length measurement was in cm...

This cannot be, surely?

[Pachydermus]

Marcellus said:

Really 2.5mm??

So unlikley to notice then?

you'll notice. whether it bothers you is a different question - I didn't get on with a change from 170 to 172.5 so switched back. Probably mostly psychological but that's how it was for me.

[okgo]

I don't notice the difference, got 170 on TT bike and 172.5 on road, or the other way round, just make sure saddle height is adjusted accordingly.

[Marcellus]

I think i'll suck it and see how i get on, i can get the new crank set for only £20 nearly new so not a massive cost if i don't get on with it.

[WinstonWolf]

Pfft. I've got 170mm one side and 175mm the other, but I'm a bit "special".