Single ring for Specialized Crux

Especially for light weight issues concerning cyclocross / touring bikes & parts.

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GregMay
Posts: 6
Joined: Sun Oct 16, 2011 10:33 am

by GregMay

Have run a few single ring setups over the last few years. All have been on 'normal' rounded tubes on the seat tube and run a K-Edge single ring CX chain guard. Perfect. The seat-tube on the Crux is squared where it meets the bottom bracket and makes it impossible to fit this.

Anyone know if there is a braze on version of this mount or similar?

Don't want to run a front derauiler for both weight and jamming. E-type mounts wont work as I'm running a 43 front ring and in past experience they clogged up pretty badly.

Ideas?

thisisatest
Shop Owner
Posts: 1980
Joined: Sat Jun 13, 2009 4:02 am
Location: NoVA/DC

by thisisatest

for a customer's hillclimb bike with one ring, i used a k-edge braze-on mounted guide. i first used a piece of round aluminum that i drilled and tapped for an m5 bolt. that gave the k-edge something to screw into, as there would be no derailleur. then i drilled and threaded another hole, this time into the side of the k-edge itself, directly over the chainring. this allowed me to thread a bolt there, which was just above the chain when in the easiest cog. i locknutted the bolt on the left side of the k-edge with a little (plastic) nut.
now the chain cannot lift itself up over the chainring teeth, a requirement in derailment...
pics to follow

Briscoelab
Posts: 1730
Joined: Thu Jan 26, 2006 6:01 pm

by Briscoelab

We put a cheap "Third Eye" fang style on my wife's for a single ring application. This was the "universal" fit type with a hose clamp. Has been working fine.

helios
Posts: 98
Joined: Mon Feb 01, 2010 10:27 pm
Location: STL

by helios

I know a couple guys run the CruX single with an outer guard and the K-Edge braze on, but not drilled out from the side as discussed above. No complaints from them. Last weekend's race had a couple really rough washboard sections and no one reported any dropped chains.

JBV
Posts: 195
Joined: Wed Jun 27, 2007 12:18 am

by JBV

Double guards are more reliable than a guard and a watcher anyway, do you have room for a guard on the inner position? This will change your chainline in that now your chainring will be on the outer spot on the crankset (where the big ring goes on a double) rather than the inner spot.

You'll need long chainring bolts & spacers too, along with the extra guard. The price of the K-Edge makes that a bit easier to take though, especially if you run inexpensive guards like BBG.

GregMay
Posts: 6
Joined: Sun Oct 16, 2011 10:33 am

by GregMay

helios wrote:I know a couple guys run the CruX single with an outer guard and the K-Edge braze on, but not drilled out from the side as discussed above. No complaints from them. Last weekend's race had a couple really rough washboard sections and no one reported any dropped chains.


THink the clamp I have is too narrow to fit around the tubing. Might try a wider clamp though.

JBV wrote:Double guards are more reliable than a guard and a watcher anyway, do you have room for a guard on the inner position?


I should have space to run double rings, have in the past on other frames, just tying to get away with as light as possible I suppose! Have the BBG guards somewhere...

JBV
Posts: 195
Joined: Wed Jun 27, 2007 12:18 am

by JBV

GregMay wrote:I should have space to run double rings, have in the past on other frames, just tying to get away with as light as possible I suppose! Have the BBG guards somewhere...


BBG superlights at $12/guard, 20-30g each depending on model: http://www.bbgbashguard.com/superlights.html

Guymk
Posts: 82
Joined: Sun Oct 17, 2010 1:44 pm

by Guymk

What about using no guards and just using a pauls chain keeper? That would be the lightest system.

Briscoelab
Posts: 1730
Joined: Thu Jan 26, 2006 6:01 pm

by Briscoelab

You can't because of the square shaped tubing at the seat tube/bb junction on the crux.

Guymk
Posts: 82
Joined: Sun Oct 17, 2010 1:44 pm

by Guymk

Ohh, I didn't know that.

gospastic
Posts: 266
Joined: Tue Jun 08, 2010 4:58 am
Location: Chicago

by gospastic

K-edge makes a clamp on catcher that mounts higher on the seat tube than the normal one. I too had a problem initially since my Jamis also squares toward the BB.

jooo
Posts: 1510
Joined: Wed Feb 02, 2011 3:48 am

by jooo

Maybe make one yourself? If you don't feel like making it from scratch, it would be fairly easy to adapt the Paul BB mount guide.

Image

Just toss the actual BB mount. Use the 'arm' and make a little L-bracket to attach the 'arm' to the braze on mount. Should be quite light and the only cost on top of the Paul guide would be a tiny piece of aluminum angle from a hardware store - which could be painted black and no-one would know it wasn't a 'factory' part. That approach would probably work with a few other guides too.

I'm sure someone like Mattias could make one for you. I think he's done a few non-standard guides. This is a custom SRAM direct mount guide:
Image

I think I've seen Fibre-Lyte mention they were/are thinking about making something also?

Maybe Berk on the forums here would also make something to suit?

brearley
Posts: 354
Joined: Mon Aug 11, 2008 10:08 pm
Location: Hull

by brearley

my crux came with a dog fang to use but because of the square section it doesn't fit, totally pointless sending one.
anybody got weights for their fully built up cruxs?

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