Toothless/smooth large chain wheel dummy

[Scott]

Hi, all:

I'm running XTR M900 triple cranks, 74/110 BCD, and want to do a build utilizing middle ring only, a 1 x 8.

What's options are out there that would replace large chain wheel with a toothless/smooth dummy wheel?

Thanks in advance!

Scott

[Bill Lindsay]

The options include:

-buy a guard

-make a guard from a donor chainring

-use a narrow-wide ring an don't bother with a guard

-don't bother with a guard and don't bother with a narrow-wide ring

One popular source for the "buy a guard" option is BBG.  They are MUSA and cheap as heck.  https://bbgbashguard.com/shop  

When they list the "size", it's the number of teeth that particular guard will cover.  For your 1x application, you may be able to get away with going a little bit bigger.  "too big" would be when the chain rubs the chainguard when you are in the smallest cog in back.  

If you want to make a guard from a donor ring, it's common to use a ring that was 4 or 5 teeth bigger than the ring you'll actually be using.  Some people break the teeth off and file what's left.  Some hacksaw the teeth off and file what's left.  Others file from the start.

Good luck with your build

Bill Lindsay

El Cerrito, CA

[Scott Luly]

Thank you for intel, Bill! Exactly direction I was looking for!

Warmest regards,

Scott

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[Nick Payne]

Here's a chainguard I made from an old middle chainring. With the chainring flat on a carpenter's saw horse, I hacksawed the teeth off, smoothed the cuts with a bastard file until most irregularities were removed, then mounted the ring onto the crank and held a 2nd cut file against the edge while rotating cranks by hand on the workstand. Finished off with a small diamond stone and cutting oil.

The old chainring I used was only three teeth larger than the chainring behind it - 41t vs 38t - so the outer diameter the chain runs at slightly exceeds that of the chainguard, but it looks alright to my eye.

Nick

[Scott Luly]

Thanks for replying and sharing, Nick. That's a sano job you did there! It looks factory.

Thanks to you and Bill now I have options to ponder...

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