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rider
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Discussion Starter · #1 ·
I'm thinking of building up a light, rigid 29er with a 1x9 drivetrain. Got tons of unused parts laying around might as well use them right? For the crank I'm thinking of using an old '91 LX 110x74mm BCD crank and just hacking off the outer arms and running a 27-28 ring off the granny bolts.

Was wondering if I'm going to push the q-factor too much by running a longer BB to get the chainline right?
 

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Those are nice old cranks -- still running pretty much the same ones as you (XT M730) on my Vulture, the 4th bike I've had them on. You should be fine on both Q-factor and chainline if you run a long 120+mm BB.
 

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rider
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Discussion Starter · #4 ·
Thanks for the input, thought they might be good candidates for this build. Think I have an old UN 72 in 122mm length to try out the chainline with. Mmm.. good BB.
 

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29erchico said:
I'm thinking of building up a light, rigid 29er with a 1x9 drivetrain. Got tons of unused parts laying around might as well use them right? For the crank I'm thinking of using an old '91 LX 110x74mm BCD crank and just hacking off the outer arms and running a 27-28 ring off the granny bolts.

Was wondering if I'm going to push the q-factor too much by running a longer BB to get the chainline right?
I'm running the exact same crank on my 29er, but with a 36 tooth on the middle (1x8) I'm using a 125 x 68 BB and it lines up pretty good with the cassette. I think an inner ring would line up well too.

You must have some huge climbs to want a 27-28. The 36 is about perfect for Michigan.
 

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rider
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Discussion Starter · #6 ·
grawbass said:
I'm running the exact same crank on my 29er, but with a 36 tooth on the middle (1x8) I'm using a 125 x 68 BB and it lines up pretty good with the cassette. I think an inner ring would line up well too.

You must have some huge climbs to want a 27-28. The 36 is about perfect for Michigan.
I'm now running a 29t middle ring with a 12-34 cassette on my AM bike. Thinking that a light rigid bike with a 28t ft and 11-34 cassette would be really fun for playing around on the granite at altitude in the sierras. Really wondering if I can climb better up there on a sub 25# rigid 29er with a 28 x 34 low gear vs. my current 34# Monk with a 20 X 34 low.

Thinking that going slow and seriously picking lines again will help my technical skills.
 

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29erchico said:
I'm now running a 29t middle ring with a 12-34 cassette on my AM bike. Thinking that a light rigid bike with a 28t ft and 11-34 cassette would be really fun for playing around on the granite at altitude in the sierras. Really wondering if I can climb better up there on a sub 25# rigid 29er with a 28 x 34 low gear vs. my current 34# Monk with a 20 X 34 low.

Thinking that going slow and seriously picking lines again will help my technical skills.
Hmmm....I think the gearing will make a bigger difference than the weight. You're losing about 10 lbs and I'll assume that you and the bike combined weigh about 200 lbs, so a 5% decrease. Your low gear is increasing by 40%, although the 20 x 34 might have been too low.

Your technical skills (and strength) probably will increase though.
 

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rider
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Discussion Starter · #8 ·
grawbass said:
Hmmm....I think the gearing will make a bigger difference than the weight. You're losing about 10 lbs and I'll assume that you and the bike combined weigh about 200 lbs, so a 5% decrease. Your low gear is increasing by 40%, although the 20 x 34 might have been too low.

Your technical skills (and strength) probably will increase though.
Thanks for the kind weight guess. I'm 220# bike goes 34# and my heavy pack and riding gear has got to go a minimum of 20#. So 274#. Long or cold rides, add up to a bunch more.

Looking at the hard numbers here, possibly I should be thinking about a 2 x 9 with a nice light modern crank running 22t & 32t rings and no outer. Was hoping to not run a front derailleur.
 

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29erchico said:
Thanks for the kind weight guess. I'm 220# bike goes 34# and my heavy pack and riding gear has got to go a minimum of 20#. So 274#. Long or cold rides, add up to a bunch more.

Looking at the hard numbers here, possibly I should be thinking about a 2 x 9 with a nice light modern crank running 22t & 32t rings and no outer. Was hoping to not run a front derailleur.
274 lbs?....makes my point about weight % even more valid. ;)

I agree its nice to loose the FD, but then you need a bashguard and a jump stop or some type of Rohloff like chain guide, so the only thing you're really losing is the shifter and cable. I think a 2 x 9 would be your best bet if you want to keep that low gear, otherwise you'll spin out too much on the fast sections of trail. I spin out a bit more often than I'd like and my high gear is a 36 x 11.
 

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@adelorenzo
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29erchico said:
Looking at the hard numbers here, possibly I should be thinking about a 2 x 9 with a nice light modern crank running 22t & 32t rings and no outer. Was hoping to not run a front derailleur.
I'm a big hoss -- 6'6" 250+ -- and a recreational/beer league sort of rider. I struggled for a while with the same decision. I got rid of my big ring straight off, so most of last year I had a 22/32 with 11-28 8-speed in the back.

I was riding last year on a 26er for most of it when I started to think about ditching the front derailleur. First thing I did was just try some rides where I didn't use the granny. That seemed OK, so I got rid of it entirely. Outer bashring but no other chainguide, and I had no problems.

When I built my new Karate Monkey I went straight to a 1x8 set-up with 32 up front and 11-34 8-speed in the back. I don't miss the granny, the 32x34 is pretty low. Sometimes I need to push up hills but hell, some of those hills I was pushing up anyways.

I had to fuss with chainline (get the ring as close inside as possible) and make sure that my chain was as short as possible (derailleur is stretched to the max in the 32x34), but I just have the outer bashguard and nothing inside.

I'll never use a front derailleur again, and to be honest I'm basically slow and fat. You don't need to be superman to push a 32x34.

Regards,
Anthony
 
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