Help needed re. crankset.

frogmanrn

Hi, hope you can help, I have just got my first road bike a giant defy 3 large which is right for my height but whilst doing my own bike fit with the help of you tube I have noticed that my crank arm is 175 and the recomended for my height is 172.5 so I have had to put my seat all the way back, Is this ok? I am quite happy to get a new one, but another thing is I dont understand all the different gearing sizes and most I have noted are only doubles mine is a triple, do I need the 3rd small ring? I did use it on climbs but from what I have seen most people dont have the small ring, I am looking at doing long rides centurys hopefully.

Thanks

brownbosh

'Standard' (usually 53/39) 'Compact' (50/34) or 'triple' (53/39/30) is a personal choice and is a fashion thing as well as a matter of choosing the correct tools for the job. If you are new to road cycling, you will probably find pushing the 53 in the biggest gears pretty hard and a 39 will not seem like a small gear especially if you have come off of one of those horrible mountain bike things! If you are using all of the gears keep them for the time being until you build up your strength and then decide after you have put some wear through your current set up and shop from a position of knowledge. I used to have a a triple and a compact but now 4 of my bikes are on a standard set up and the other is a single speed. I have no issues getting up hills on a standard rig but if i was going to ride the alps or a hilly long sportive i would put back on a compact or a triple from my spares as i saw fit. Triples are considered girly but i say they are not as girly as being seen to push a bike up hill! Welcome and i hope you grow to love riding on the road half as much as i do!

HonestAl

You have a couple of things tangled up here. First, the length of the crank, then second the gearing.

I don't really understand why having a slightly longer crank than ideal (by 2.5 mm) would make you move the saddle BACK. If you're using KOPS to position the seat, I'd have thought it would have you move the seat forward (when one crank is pointing "forward" (as in parallel to the ground with the pedal near your front fork, the pedal is 2.5 mm closer to the front of the bike, so your knee should be 2.5 mm farther forward, so your saddle would be 2.5mm farther forward, not back. And of course the saddle would be a smidgeon lower (cos the pedal gets 2.5mm closer to the floor due to the longer crank) Therefore I'd imagine you'd have the saddle very slightly lower and farther forward.

But hey, I could be confused.

then there's the double / compact / triple story...

However I reckon brownbosh is spot on in terms of "suck it and see" on both counts. Or go back to the shop and get them to help?

frogmanrn

Thanks for your input that has cleared things up alot,

with the crank arms when the pedals are horizontal to the ground i ran a plumb line from my knee and it is supposed to run through the pedal axle but to get that I had to put the seat all the way back, but I know what your saying 2.5mm is hardly going to change it, heres the link to the video it might help some people out.

Thanks for the help





http://www.youtube.com/watch?v=FAl_5e7bIHkthe

frogmanrn

if that link dosnt work type in= HOW TO FIT A ROAD BIKE