8-tooth spread on QB/SO track-ends

[j.schwartz]

Curious if the 8-tooth "max" spread can be pushed by a tooth or two?

Is that just a conservative figure or has anyone successfully run a larger (9 or 10 tooth) chain ring size difference on their Quickbeam or Simpleone and still had good brake pad alignment on the rear wheel?

I'm rebuilding my SO and I have a 41/32 crank which is only 1 tooth larger than the spec.

The freewheel is 20t and the wheels are 700/43.

[Jim M.]

8-tooth is the max I could get, and that was with 700x33 tires. Larger tires reduced the achievable spread because they can't move as far forward between the chainstays.

[Deacon Patrick]

You can get wider gear inch spread with a smaller tooth spread if you use a flip-flop hub or a White Industries DosEno freewheel. Then you run little cog with big chain ring, big cog with little chain ring. 

With abandon,

Patrick

[j.schwartz]

Thanks Patrick 

I forgot about that.

What sort of gearing numbers did you run on your off road QB?

[Deacon Patrick]

Still running it. Grin. 44/34 x 17/21 (fixed gear Surly Dingle cog), yields 44x17=71" and 34x21=44". Keep in mind that's geared up for fixed.

With abandon,

Patrick

[Coal Bee Rye Anne]

I don't own a QB/SO/Frank Jones, but used the same approach as Deacon Patrick described to try different gear ranges in a more traditional horizontal track end and keep axle movement as minimal as possible.  My frame also had more limited tire clearance but when using a Surly dingle cog for fixed with no rear brake I had much more room to work with and no brake pad alignment issues.  You may or may not experience any issues or matters regarding chainline, depending what changes you make.  I'm not a chainline snob, and certainly still a novice when it comes to all this stuff, but did learn quite a bit when I first began messing around with singlespeeds and fixed gear builds and did end up finding some quirks regarding chainline, such as:

Different cog spacing/chainline between freewheel and fixed cogs on a flip flop hub.

One of my builds included a White Industries 17/19 Dos Eno on the flip side and a Surly Dingle fixed cog with same 17/19 spread on the flop side, with a matching 2 tooth difference on a double crank (which would keep the axle in the same exact spot in either combo.)  I thought I'd just use the outer chainring and 17t with either the freewheel or fixed side and the inner chainring with the 19t either freewheel or fixed.

WARNING: Don't try shimming your fixed cog on the hub.  I briefly tried this to get the Surly cog to match the freewheel chainline but this does not allow enough lock ring thread engagement.  Ask me how I know?  I stripped the outermost lock ring threads upon a hard skid-stop as the cog unthreaded itself and overpowered the lockring!)

The spacing was off enough that the 17t fixed and outer chainring combo would bind a little, I could reduce this by slackening the chain a little but then crank engagement in fixed was less desirable with the slack.  I also found that I wanted to gear up a little more with fixed so my matching 17/19 combo was good in theory to make the most of an otherwise limited range of axle movement in the dropout/track ends but not so good in practice.

I ultimately changed the rings around and flipped them inside out, placing a larger 44t chainring on the INSIDE of the double crank and a 42t chainring on the OUTER position, which gave better chainline with the larger inner ring and fixed cogs with the higher gearing and good chainline with the lower geared freewheel in the outer 42t ring.

This improved a couple things, but then eliminated the possibility of the 44x19t fixed combo because of the axle movement needed and brake pad alignment and under caliper clearance issues.  I'd have needed for further reduce tire width or remove the rear brake entirely to get them all to work, which would otherwise eliminate either the freewheeling option (if removing rear brake) or eliminate the benefits of a slighter lower 44/19 fixed gearing which otherwise worked nicely with my chosen semi-slick tire for occasional off-roadish detours (if going back to a narrower slick tire.)

All in all I had a lot of fun with all the gearing/axle/chainline experimentation but in the end I realized that in practice and with my local terrain I could handle a much simpler 1 tooth difference in a flip-flop fixed/freewheel and will eventually finish an updated build with 15t fixed cog/16t freewheel and a single chainring plus outer chainguard (still a work in progress for various reasons.)

Of course, I'd likely be singing a different tune if I had the adjustment range of the QB dropouts and would keep the greater gearing spread.  Best of luck on your rebuild!

Brian Cole

Lawrenceville NJ 

[Philip Williamson]

I echo other people's recommendation to run a Dos Eno or a Surly Dingle cog. I have two rings and a Dingle cog on my Quickbeam, giving a one tooth difference in the two gears. 39/44 x 17/21. I have fenders on the bike, so it's nice to not worry about fender line anymore, or trying to flip the wheel. 

Good luck with the rebuild!

Philip 

Santa Rosa, CA 

On Monday, October 14, 2019 at 3:24:57 PM UTC-7, j.schwartz wrote: