“Max’s” new bike

“Max’s” new bike, originally uploaded by BikeTinker.

So far, it’s set up for me, while I “iron out the kinks.” This bike is really nice. I want to drop the levers a quarter inch, and run the cables higher on the bars, but it’s pretty well dialed. Dingle setup, 36×14 and 32×18. Flared drops. Flat pedals. I haven’t tried the low gear, but I bought a new ring just for it. Coasting is actually pretty fun!

I like cassette hubs, and I like disc brakes. And threadless headsets. The two-tone bar wrap is also pleasing me a lot. You’ll see that again in a little bit.

It’s a Gary Fisher Utopia hybrid my friend Jim (coincidentally a fan of CycloFiend’s bike gallery)¬† gave me for my 10 year old. I thought (and Max still thinks), “Dude, it’s a grown-up bike!” But at 43cm, it’s the smallest 700c bike I can find, and the same size my LBS recommended for a kid’s first ‘full size’ bike. The only issue is getting the bars low enough, but a short stem, inverted, and the seat slammed all the way, puts the bars and saddle in the same relative position as his Redline Junior.

I replaced the Metro shock with a rigid Kona Project 2 fork, and got some 42cm Salsa Woodchippers from a friend. The bartape is Newbaum’s cloth tape, from Rivendell.

So far the kid is sticking with the Redline Junior BMX bike he’s had since he was 5. That works for me, since I haven’t ridden another bike since I set up the bars. Stop me before I put a rack on it!

Multi-speed Fixed Quickbeam

Quickbeam, originally uploaded by gjtramey.

From one of my Flickr and RBW group friends. I like his gear spread for a go-anywhere fixed gear bike. He’s using the Surly Dingle double-fixed cog and some larger rings than the stock Rivendell setup.

Rings: 39/45
Cog 1: 17/21 Surly Dingle cog
Cog 2: 23
Gears: 46, 50, 58, 62, 71.5

I’ve migrated toward larger rings on road cranks, too, but I like his 23t flip cog better than a 15t cog. That’s a beautiful spread. He can drop from 72″ to 50″ without taking the wheel out of the dropouts. Flipping the wheel, his biggest and smallest gears have the exact same axle position.

rings 45
50.1″ 57.9″
45.8″ 52.8″

Running the numbers, we can see that he must be using 32mm tires. And, uh, plus we can see them. 38 or 40mm tires will give slightly taller gears.

Gear ratios for Torpedo 2-speed hubs

Figuring your gears is a little tricky with a two-speed hub that shifts by itself. The low gear is 1:1, the high gear is 1:1.36.

The low gear is direct-drive. There’s no fussing; the gear you calculate on Sheldon’s gear calculator is the actual low gear. It is the 1:1 gear.

The high gear is 36% larger. I plugged in larger cog sizes until I got ones about exactly 36% larger. I just noticed that Sheldon’s calculator will let you add fractional cogs!

I’m a double idiot – I just noticed that Sheldon’s gear calculator lets you choose a “Sachs Duomatic / Automatic” hub in the Internal Gears dropdown. This way is a little easier to read, though.

I have a 19t sprocket, and a 22t sprocket. I also have 39, 40 and 42 tooth chainrings I think might work for this project.

The “high gear equivalent” for the 19t is 13.97 (let’s call it a 14). The “high gear equivalent” for the 22t sprocket is 16.18. Again, 16 is plenty close.

With a 19t cog and a 39t chainring, I get a low gear of 56″ and a high of 76″

19t low
56.1 57.5 60.4
36.0 %
high 76.3 78.2 82.1

With a 22t cog and a 42t ring, I get my ideal setup: ¬†52″ low and 71″ high gear.

39 2.6 % 40 5.0 % 42
22t low 48.4 49.7 52.2
36.0 %
high 65.9 67.5 70.9

The Sachs Torpedo 2-speed gives a slightly wider ratio than my double fixed setups that use a 17/21 Surly dingle cog and a four-tooth chainring difference.