Bike Forums

Bike Forums (http://www.bikeforums.net/forum.php)
-   Fifty Plus (50+) (http://www.bikeforums.net/fifty-plus-50/)
-   -   Sort of technical question (http://www.bikeforums.net/fifty-plus-50/315097-sort-technical-question.html)

tlc20010 06-28-07 08:58 PM

Sort of technical question
 
Okay, an actual bike question. One of my bikes has a Shimano FC-R700 compact crank with 172.5 mm crank arms and I might be interested in trying a shorter crank. Do I have to buy a whole new crank set or can I get just the sorter arms--and from where and is it easier (and/or cheaper) than getting a new crank set??

Jet Travis 06-28-07 09:01 PM

I fear you must get a new crankset.

BSLeVan 06-28-07 09:03 PM

You'll need the whole crankset. The drive side arm is attached to the spider arms to which the chainrings are connected.

Tom Bombadil 06-28-07 09:53 PM

I sure wish it was easier. I'd love to try 165mm crank arms. All of my bikes presently have 170mm.

Technically a 172.5mm arm should suffice unless your inseam is less than around 31".

John E 06-28-07 09:55 PM

Just swap the cranks themselves. You can reuse your bottom bracket, pedals, and chainrings. With luck, you might even find someone with whom to trade cranks.

BluesDawg 06-28-07 10:15 PM

Theoretically you could take the spider and rigs off of your current arm and replace just the arms. But in reality you will not likely be able to find the arms for lass than a whole crankset. Replacing a crankset is a 5 to 10 minute job. You won't even need a crank puller for the FC-R700.
http://www.parktool.com/repair/readh...id=122#shimano

stapfam 06-29-07 12:09 PM

Now just a change of crankset and you may be lucky---BUT-- In my experience- even if you have the same type of bottom bracket (Splined or square Etc. ) You may need a different length bottom bracket. Found this a lot on the MTB's where you do an upgrade that is many grades of up. Shimano LX up to XT was fine as there was only 2mm difference but Once had to change a Cheap OE fitment to Deore and the Deore required a BB of 115 mm and the OE had a BB of 127mm. Didn't matter that much as The BB was shot- but just a warning that you may have to change the BB aswell.

BluesDawg 06-29-07 01:16 PM

Quote:

Originally Posted by stapfam
Now just a change of crankset and you may be lucky---BUT-- In my experience- even if you have the same type of bottom bracket (Splined or square Etc. ) You may need a different length bottom bracket. Found this a lot on the MTB's where you do an upgrade that is many grades of up. Shimano LX up to XT was fine as there was only 2mm difference but Once had to change a Cheap OE fitment to Deore and the Deore required a BB of 115 mm and the OE had a BB of 127mm. Didn't matter that much as The BB was shot- but just a warning that you may have to change the BB aswell.

I think most of us are assuming he would be changing to a longer arm crank of the same model as the original, not an upgrade. At least that is what I took him to mean.

ThinLine 06-29-07 01:17 PM

Bummer!
:)

Tom Bombadil 06-29-07 01:25 PM

Quote:

Originally Posted by tlc20010
Okay, an actual bike question. One of my bikes has a Shimano FC-R700 compact crank with 172.5 mm crank arms and I might be interested in trying a shorter crank.

Pricey crankset.

W/170mm crank arms:
http://www.niagaracycle.com/product_...oducts_id=6755

w/165mm crank arms:
http://www.niagaracycle.com/product_...oducts_id=6754

RockyMtnMerlin 06-29-07 01:45 PM

Quote:

Originally Posted by Tom Bombadil

No. THIS http://fairwheelbikes.com/index.php?...products_id=64 is a pricey crankset. Only about $1,000 additional dollars!


All times are GMT -6. The time now is 05:41 AM.