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Discussion Starter · #1 ·
I've searched, and haven't been able to find any information about the bottom bracket type and dimensions, other than they are 73mm... are they external bearings? What is the length?

I intend to use my Shimano M521 Hollowtech Octalink cranks with my new BM frame.


TIA!
 

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Frt Range, CO
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GpzGuy said:
Yes? 73mm by what? How long? External bearings or not?
English threads, external or internal will work fine. Octalink BB comes in 68mm and 73mm, you'll need 73mm. If you have a 68mm octalink bb, buy a 73mm octalink bb with same spindle length (should be 113mm/118mm/122mm/127mm). Here's a cheap V2 octalink bb:
http://www.universalcycles.com/shopping/product_details.php?id=15802&category=347

Jenson has last year's LX cranks on sale for $90, they'll fit:
http://www.jensonusa.com/store/product/CR303A00-Shimano+Lx+Fc-M582+Crankset.aspx
 

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I would buy the LX cranks from Jenson, the Big Mama has chain suck issues related to cranksets, and I suspect the M521 crankset you mentioned above would not help alleviate the situation.
 

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rth009
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Definitely get Shimano crankset for your Big Mama, as there are chain suck issues with this frame with certain cranksets. I replaced the stock Race Face crankset with a Shimano XT and have had no problems since then. I strongly recommend XT for use on your Big Mama. I suspect the LX would suffice, but dont have any personal experience withthem
 

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Discussion Starter · #8 ·
Ummm... thanks guys! But I'm a bit confused because the cranks I have ARE Shimano (slightly older) LX (FC-M521). Really not much difference between them and the XT except for weight.
 

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The newer LX as shown at Jenson are hollowtech 2, external bearing cranks and should be much stiffer than an older ISIS crankset. Stiffness is key to avoiding chainsuck with the Big Mama.
 

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rth009
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I dont know whether it was stiffness or not, but in my experience Race Face chain sucked and XT does not. Obviously try the crankset you have, and make sure and instal the recommended spacer for your crankset and the 73mm bottom bracket, but if it starts sucking on you, you might have to spring for the XT crankset.
 

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rth009 said:
Definitely get Shimano crankset for your Big Mama, as there are chain suck issues with this frame with certain cranksets. I replaced the stock Race Face crankset with a Shimano XT and have had no problems since then. I strongly recommend XT for use on your Big Mama. I suspect the LX would suffice, but dont have any personal experience withthem
More likely a chainring issue than crank. I only get chain suck when the rings are worn out.
 

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I'm just messing with you
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shiggy said:
More likely a chainring issue than crank. I only get chain suck when the rings are worn out.
I get chainsuck with a new Jenson LX crank if I shift at exactly the wrong time. It's just the nature of the Big Mama beast. The good thing is the chain doesn't jam, but it sucks to have to backpedal if you're headed up a hill ....

I used a Firex crank for months with no chainsuck at all, but as soon as I swapped that for the LX, bang there it was.
 

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I tried two different sets of rings on my Race face and had chain suck with both. I slapped an xt crank on and problem solved. I've heard the slx works fine too
 

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rth009
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murph62903 said:
I tried two different sets of rings on my Race face and had chain suck with both. I slapped an xt crank on and problem solved.
That is my exact experience. I wore through the stock set of race face deus team rings and then put new Race face turbine rings on and it chain sucked frequently with both types of chain rings. Since I installed a new XT crankset Ive had no problems.
 

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Well Shiggy that's what I thought also, but how can we all have worn out ringe on new bikes, I have two Salsa bikea a Big Mama & a Mamasita.

The B/M had the Stylo 3.3 I turned it into a 2.2 I had some problems but not much that frame is for sale.

The Mamasita had the Fing XT build I changed it over to XO, BUT!, I didn't change the
Race Face Deus. I had nothing but problems with it, I fell that Salsa should have recalled the R/F deus cranks. It's going to the dump! I see where people are selling them on line they should be ashamed, that dues crank keep getting chain suck and it has tor-up my frame and I might beable to sell it for 1/2 of what I could have.

I am building up new bikes & I'm sure that they are going to be H/T but what kind?
 

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Discussion Starter · #16 ·
Well, I have a chain suck issue... happened right on the work stand while tuning it. It happens when going to the smallest chainring while in a middle to small cog. I suspect that the sudden slack in the chain isn't being taken up fast enough by the rear derailer cage. It didn't happen when I had more tension in the chain... but I had to add a link to the chain to get its length right.... does the chain distance get shorter or longer as the suspension compresses? I was just barely able to run it without the extra chain link on the biggest cog and biggest chainring, but the chain would rub on the derailer cage due to too much tension. I'm thinking that if the chainline shortens when the suspension is compressed, then at proper sag then it should be hunky dory.

BTW, I took the advice and got the Shimano LX crankset from Jenson because my old bottom bracket wasn't wide enough.
 

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I don't remember which way my chain behaved when I compressed the suspension. Seems like it didn't change much at all though. It's simple to figure out though, just let the air out of your shock and compress the suspension and figure it out.

You might be the first to report chain suck on the stand. Be careful sizing that chain, you can rip the derailleur and/or hanger off if you're not careful. I run mine per the rule of thumb, around the big gears and add one full link.
 

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GpzGuy said:
Well, I have a chain suck issue... happened right on the work stand while tuning it. It happens when going to the smallest chainring while in a middle to small cog. I suspect that the sudden slack in the chain isn't being taken up fast enough by the rear derailer cage. It didn't happen when I had more tension in the chain... but I had to add a link to the chain to get its length right.... does the chain distance get shorter or longer as the suspension compresses? I was just barely able to run it without the extra chain link on the biggest cog and biggest chainring, but the chain would rub on the derailer cage due to too much tension. I'm thinking that if the chainline shortens when the suspension is compressed, then at proper sag then it should be hunky dory.
I think you nailed the primary cause of most chainsuck issues -- it's chain length and the resulting tension. I've run a couple of different cranks on my Big Mama in (going on) three seasons of riding it, and there have been no inordinate chainsuck issues to report. For the most part, I think that's because I've had the chain length dialed from the start, I haven't run it too short and I change my chain before it stretches enough to cause significant drivetrain wear. Those three factors have kept the right chainstay of my Big Mama relatively clean and gouge-free.
 

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Are you using an old rear derailleur? A new RD could solve a tension related issue, newer Shimano and SRAM derailleurs both have a lot more tension than older models. You can buy an N-Gear Jumpstop to help prevent this occurance, too.
 

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Discussion Starter · #20 ·
Its a Shimano M772 derailer. Brand new in '08.

I don't see how the N-Gear Jumpstop is going to help. It looks like it installs on the seat tube to provide a limit on the chain at the top of the chainring. Where the chainsuck is occuring is at the bottom of the chainring
 
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