[Archer]

Hey guys - I need some technical info on crank types.

Can I swap out my 2008 Kona Jake the Snake FSA Gossamer MegaExo Compact 46/36 with a Ritchey WCS Road V Crank 50/34 compact double? Trying to keep the same B/B (FSA MegaExo) if possible. Long story short, I need more top end gear for the flats and low end for climbing. I have never done a crank removal before. My first glance at the two cranks looks like they are not compatible The Ritchey's are Shimano Octalink compatible I think. Not sure about the FSA Gossamer though. Are there any special tools I need to remove the sprockets/arms? Will I need to replace my chain with a longer one?
The other thing I am worried about is the Ritchey's are 172.5mm arm length and my FSA's are 165mm, is this something that could effect my bike setup/ergonomics, mainly my knees? Seems like I would have more leverage....with the 172 jobbies
I am a newbie......any simple input on this matter is greatly appreciated.
Was going to try and do the swap myself instead of LBS. Save a little $$
Thanks in advance.
Cheers! :thumbsup:

 

[cocoboots]

you will need an octalink BB.

I recall reading that Ritchey issued a recall on their cranksets? can't remember if it was on here or velonews/cyclingnews.... someone will chime in with the specifics.

find a local member and see if they will help you with the crank swap and bike fit.

 

[hayduke1972]

First off...its very doubtful that your Jake the Snake has a 165mm crank arm length. You should check it again...its probably 175mm

Second, why not just swap out chainrings on the FSA crank. You don't need an entire new crankset to get a 50/34 combo...just replace the chainrings.

 

[Archer]

I checked it twice, it was stamped on inside of both crank arms "165". Suppose I could measure it too. The part no. for my FSA's are CK-6020 (not compact double). The 165mm is probably the reason I am having trouble climbing. A hill that can be done by 42/28 I can barely do with my 36/28.... straining for leverage. Maybe cross bikes use 165 for clearance......maybe somebody can confirm this. I should also mention I am riding a 49cm frame. I have a 28" inseam.
Great suggestion Duke, I should just sell the Ritchey's and buy 2 chain rings. Just wanted to loose a little weight and gain some arm length for the hills. The Ritchey's are a little sexier too, Flat Black as opposed to my chromed out shiney pimp daddy FSA's. Also, I missed the recall by 1 month on the Ritchey's..... thanks again.

 

[wim]

Crank length.

165 mm cranks are considered just about right for a 28" inseam, so it makes sense to have them on a 49 cm frame. But you shouldn't have any problems with 172.5 mm cranks. I'd lower the saddle about 3 or 4 mm to compensate for the longer cranks.

As to leverage from the crank—it doesn't do as much as you hope it will. For one, there are three more levers to go through before power is on the road (chainwheel radius, cog radius and rear wheel radius). The other thing are the laws of torque: what leverage gives you, the longer crank circle takes away—unless you increase your leg speed. (However, if you mash uphill at agonizingly low rpms, leverage does help a bit.)

 

[hayduke1972]

OK...in the context that you have a 28" inseam and a 49cm frame...a 165mm crankset makes sense (though I'm surprised its not a 170 on a cross bike).

165mm is the right size for your inseam. Also, you don't need to sell your Ritchey cranks, both the FSA and Ritchey use a 110mm bolt circle so the chainrings should swap.

But if you want to use your Ritchey cranks, you'll need to remove the FSA bottom bracket and replace it with a Shimano Octalink V1 bottom bracket.

 

[Archer]

Hey thanks a bunch guys for suggestions.
Looks like I will just swap out the rings as suggested. Cut my losses.

Do I need to worry about making my chain longer?
Will I need to adjust front derailleur? (eek)
Last time I made derailleur adjustments my LBS wanted to shoot me for having to fix my madness. Lol. Instead they settled for charging me double.....I know I would have.
Live and learn....right?

Thanks again guys.
Hasta

 

[bopApocalypse]

Hey thanks a bunch guys for suggestions.
Looks like I will just swap out the rings as suggested. Cut my losses.

Do I need to worry about making my chain longer?
Will I need to adjust front derailleur? (eek)
Last time I made derailleur adjustments my LBS wanted to shoot me for having to fix my madness. Lol. Instead they settled for charging me double.....I know I would have.
Live and learn....right?

Thanks again guys.
Hasta

If your chain is sized as short as possible (shifting into the big-big combo is barely possible) then you'll need to lengthen your chain. If your chain was sized as long as possible (just a little bit of chain tension in the small-small combo) then you may need to shorten it.

You will probably need to raise your front derailleur to accommodate the bigger ring.
Read park tool's guides (http://www.parktool.com/repair/byregion.asp?catid=53), and understand what you're doing when adjusting derailleurs - if you understand how it all works, it's pretty simple.