[el_gordo]

Cross post for a bit more visibility -- hopefully someone who rides a MkIII can also tell me if this is unusual behaviour or just the way the frame is constructed.

I purchased a 2005 MkIII frame earlier this year and built it up. I've gotten probably 5 rides on it but am having two huge issues:
Issue 1) Chain suck from the day I built it. With both the Evolve and Atlas cranksets, any shifts to the small ring when under pressure (i.e. climbing) results in the chain wrapping up under the front ring. The entire drivetrain is new, including the chain. I set the chain length at the standard big ring/big cog +2 links based upon the suspension at full extension (top of travel).
Issue 2) Running the big ring and shifting to the 26/30/34 cog makes the chain into a chainsaw on the bottom chain stay. I know cross chaining is bad, but no one told me it would saw my bike in half (see pictures).

Setup (all parts are NEW) --
2005 IH MK III Team frame, medium, bb chased and faced
Cranksets (I've tried two sets) --
Race Face Evolve DH w/ bash X-type (no chainsaw issue here, but then again no big ring)
Race Face Atlas X-type (spec on IH MkIII Team), currently dialed with the chainline at max out (50mm I believe).
Front derailleur -- SRAM X.Gen (spec on IH MkIII Team)
Rear derailleur -- XT
Chain -- SRAM 990
Shifters -- XT
Rear cassette -- XT (same size as spec)
Wheelset -- Mavic Crossmax XL

Chain on big ring and 26 tooth cog

Results #1

Results #2

This has pretty much driven me nuts. I am not even worried about how it shifts right now, I just want to be able to climb a hill without eating sh!t when I shift.

 

[stosh]

Check the spacers on the BB.

 

[el_gordo]

The cups (not sure what the x-type bb term is) are spaced per the Race Face instructions for my bb width. I added chain line spacers to push the chain rings out. I peeked at a MkIII at the local Performance store with the FSA crankset, but it did not look like the rings were pushed out any abnormal distance, but I did not but a measuring tape to them.

 

[Wumpus]

PM Ska Todd or call Iron Horse.

 

[el_gordo]

I sent IH an e-mail (yesterday) through their web site, waiting for a reply. I'll ping Ska Todd if they don't reply.
thanks -
PS -- got 2 fad bikes sitting in the garage...I'm waiting for a 29er downhill rig with a 29er triple crown fork...

 

[ska todd]

I've seen this info w/ some of the different 2pc crank set-ups out there. No two seem to be exactly the same set-up and some seem to be different even from crank-to-crank w/in brands.

Add another BB spacer to move the chainrings out some. I had to do this on my Diablous cranks on my DH bike despite what the instructions said. I checked the spacers on an Atlas crank here on someone's personal MkIII and they are running one spacer on each side. There is no sign of chain suck and the bike shifts beautifully in the stand. For the chain contact issue, when in the 44x32/34 the chain will contact the chainstay when the bike is static. However, with proper sag (25-33%) there will be no contact. We recommend THE Jet Pro chainstay protectors if you're looking to cut down on the slap here.

-ska todd

 

[el_gordo]

Todd -
thanks. I'll give adding a spacer a shot. I wasn't sure I wanted to brake (pun intended) the rules on the bb spacing issue without some guidance from above (or NY, which is technically above Virginia).