Cheap way to reduce crank length on racing bike

[Gingerbread Man]

I picked up a 2002 Giant TCR 3 racing bike as my first road bike.

I really like it, however the crank length is 172.5mm which feels really long. When I am in the drops my knees are coming up to my stomach even tho the saddle is set as high as I dare.

I have an inseam of 30 inches and I would like to try 165mm cranks.

It seems it would cost me almost as much as the bike cost me to buy a complete new Shimano 105 crankset. Is there another way? Cant I get hold of some nice cheap alloy crank arms that would fit to the chain rings?

EDIT: This is an FC5500 model 105 crankset. The chain rings are 53/39. Since I am coming from a 48/38/28 MTB this is a bit of a struggle and I run out of lower gears. If I am going to have to spend a lot - I may as well go for a compact crankset instead of a 53/39. Is this easy or are there compatibility issues I need to consider?

 

[daveryanwyoming]

First it sounds like you could use a good bike fitting. It's likely your bars are set pretty low if you hit your knees to your chest while riding in the drops with an appropriate seat height. That or what seems like an appropriate seat height is actually a bit low or a combination of both.

But if you do want to swap to shorter cranks I'd look for used cranks on ebay or Craigslist, maybe something like: http://www.ebay.com/itm/Shimano-105-5700-Compact-50-34-Crankset-165mm-Bottom-Bracket-Not-Included-/150918697490?pt=Cycling_Parts_Accessories&hash=item2323749212

Which would give you both the shorter crank arms and a set of compact chainrings.

If you swap to compact cranks you'll want to lower and readjust your front derailleur but otherwise it's a pretty simple conversion assuming your existing cranks and the new cranks both use the same bottom bracket style.

Of course if you do swap to shorter cranks you'll want to raise your seat so that extension at the bottom of the pedal stroke is the same which again gets back to getting a good bike fitting.

-Dave

 

[dabac]

Originally Posted by daveryanwyoming .

First it sounds like you could use a good bike fitting. It's likely your bars are set pretty low if you hit your knees to your chest while riding in the drops with an appropriate seat height. That or what seems like an appropriate seat height is actually a bit low or a combination of both.

+1
Odds are, there's more than overly long cranks lurking here. And 53/39 is a fairly high gearing. Depending on what cassette you're using, a 39 can still let you get away with a fair amount of everyday riding. But don't expect to use your 2-3 highest gears for anything else than scary fast descents.

 

[Gingerbread Man]

I am consistently getting push back from LBSs I ask about 165mm cranks. They say I need 170mm.

I have only done few hundred miles on a road bike by now so what do I know? BUT I have proportionately short legs even for a short guy (5ft 7) and I am struggling to accept that I should be using "standard" 170mm cranks.

My biggest problem is that when in the hooks the tops of my thighs are hitting my tummy flab (and believe me I havent got much of it). IMHO my knees are coming up too high even though the saddle is set as high as I can have it without overstretching (causing me hamstring issues). Reducing from 172.5 to 170mm seems like nowhere near enough (2.5mm?!) to solve this problem and investing in a new chainset is a big big investment for me.

I cant afford a bike fit. Not for quite a while anyway. I think Santa would need to be involved in that one.

I want to hear that 165mm is what I should be choosing - though I am trying to keep an open mind.

Advice ?

 

[vspa]

a 165mm is really for a track bike, it is needed low to avoid hitting on the tarmac in steeply banked oval tracks, 170mm is the standard for road cranks, i hit my stomach too on the drops but the reason is that im really overweight right now, for this same reason i switched to a compact 50-34 crankset, it really makes life easier if you are not in good shape, i'll only switch back to the 53-39 if i come into great condition, which i doubt for the time being

 

[alienator]

I am consistently getting push back from LBSs I ask about 165mm cranks.  They say I need 170mm. I have only done few hundred miles on a road bike by now so what do I know?  BUT I have proportionately short legs even for a short guy (5ft 7) and I am struggling to accept that I should be using "standard" 170mm cranks. My biggest problem is that when in the hooks the tops of my thighs are hitting my tummy flab (and believe me I havent got much of it).  IMHO my knees are coming up too high even though the saddle is set as high as I can have it without overstretching (causing me hamstring issues). Reducing from 172.5 to 170mm seems like nowhere near enough (2.5mm?!) to solve this problem and investing in a new chainset is a big big investment for me.   I cant afford a bike fit. Not for quite a while anyway.  I think Santa would need to be involved in that one.   I want to hear that 165mm is what I should be choosing - though I am trying to keep an open mind. Advice ?

Have you checked eBay? You can get a set of 165mm cranks relatively cheap, used. If they don't work for you, you can resell them, and if they work for you, you win.