Single Speed Gearing

It took me months from the time I first started thinking about going single speed to when I finally plunked down the cash for my Salsa Cassaroll.  What finally put me over the top was:

  1. Realizing I was 42, and that it wouldn’t be too long before ascending Capitol Hill on a single speed would be a physical impossibility; and
  2. Finally getting a grip on gearing, “gain ratios” and what it would mean to do the ascent in a relatively high gear.

Trying to figure out gearing was HARD.  I really didn’t want to walk my bike up the hill.  I finally stumbled on Sheldon Brown’s site, which contains a highly-illuminating formula for figuring out the gain ratio of gearing (thus allowing me to compare the gearing on my 9-speed urban destroyer commute bike with the single speed of my dreams). Here’s how the formula works.  It looks more complicated than it really is:

  1. Determine the wheel radius.  Note that wheel radius is influenced by tire depth; a 700 x 28 road tire has a radius of 336 mm, vs a 44 mm tire on the same wheel which has a radius of 354 mm.  Refer to Sheldon’s handy-dandy chart.
  2. Divide the wheel radius by crank length (use consistent measurements for each – millimeters or inches) to get the “radius ratio.”  For the old urban destroyer, this yielded a radius ratio of 1.906 (324 mm wheel radius/170 mm crank length).
  3. Divide the number of teeth on the chainring by the number of teeth on the rear sprocket (let’s call this the “tooth ratio”).  For third gear on the destroyer – the gear I typically used to climb the hill – this was 38/18, or 2.11.
  4. Multiply the radius ratio by the tooth ratio to get the gain ratio – which can then be compared, apples-to-apples, to the gain ratio on any other bike.  Third gear on the destroyer? 1.906 x 2.11 = 4.024.

Now, most of the single speed road bikes I looked at had radius ratios around 2.00.  That meant that getting gearing equivalent to what I was currently climbing the hill with would require a tooth ratio of around 2/1.  While that would make it easy to climb the hill, it would be impossible to ride at any speed with such gearing.

The trick was to find a tooth ratio setup high enough to allow some speed on the flats but not so high I’d be unable to climb.  In talking to people riding single and fixed gear bikes up the hill, this seemed to indicate a ratio of a little less than 3.00 (one popular single speed configuration is 42/16).

I saw one guy riding a track bike up Pine with a setup of something like 52/12, but he looked like he weighed in at about what I did at age 9, so I ruled that configuration out.

Here’s where it got daunting:  a 42/16 configuration has a tooth ratio of 2.63.  Multiplying that by a radius ratio of 2.00 equaled 5.26 – which is about what 7th gear was like on the urban destroyer.  Gulp.  I tried climbing the hill in that gear a couple of times, but always had to gear down after a block or two.

Ultimately, I just took a leap of faith and went for it.  More on that later.

Cycle Track for Broadway?

As plans for a streetcar down Broadway develop, CHS Capitol Hill Seattle reports that SDOT is considering including a “cycle track.”  Presumably the cycle track would run down the center of Broadway, along with the streetcar.

I think I like the idea of a cycle track; there aren’t any in central Seattle (or elsewhere in the city, as far as I know), but Portland has been experimenting with them.  The idea is to create a traffic-separated lane for bicycles, sort of a bike path attached to the road.  Cyclists on a bicycle track are thus not contending with cars or doors, at least until they try to exit the cycle track.

It would certainly be a step up for bicycle infrastructure in the city.  While Seattle likes to tout its bike-friendliness and hundreds of miles of bike routes, most of these are indifferent or downright dangerous “improvements.”  For example, the lion’s share are sharrows, those ubiquitous painted stencils of cycle-and-chevrons.  Painting a few sharrows and calling it a bike route is hardly progress.

seattle sharrows

Others are worse; the bike lane down Pine attempts to squeeze cyclists into a narrow space next to parked cars, often occupied by delivery trucks and continually bedeviled by right-turning cars and brazen pedestrians.  For riders, it’s far better (and safer) to  just claim the lane and gain some visibility and maneuvering room.

pine street seattle bike lane

In fact, the only bicycle route I can think of in downtown Seattle that offers a positive alternative to just riding in traffic is the uphill bike lane on Pine.  While it suffers from the same narrowness and proximity to parked cars as its counterpart across the street, the speed differential makes all the difference.  I’m a lot less concerned about getting doored when I’m standing in my pedals, climbing the hill, than when I’m bombing down it.

My biggest concern with the cycle track is, in fact, the lack of maneuverability.  How easy will it be to ride around slower cyclists, or groups of club-going pedestrians when they cross the cycle track?  I wouldn’t be surprised to find that, just as with the downhill bike lane on Pine, it’s better to just keeping riding amidst the cars.

Why Single Speed?

Bike Shop Girl had a nice post last week on single speed and fixed gear basics, noting the primary benefits of going gearless: greater pedaling control and lower maintenance.  My road to single speed started some months after starting to ride to work every day, as the realities of daily use started to take their toll on my bike.  Despite the slipping gears and weekly dérailleur adjustments, it took me over a year to finally make the move to single speed.

The reason for my delay was simple enough:  facing me at the end of every day was the ride from downtown up Capitol Hill; 300+ feet of elevation gain in the first two miles.  The only people I ever saw with single or fixed gear bikes going up Pine Street were rail-thin hipsters, and many of them were pushing their bikes.  I vowed that wasn’t going to be me (the pushing part – I’m at least 80 pounds and 15 years over the hipster limit).  But when I’d try making the climb in a single speed gear ratio I could never make it all the way without shifting down.

The answer was to burn my bridges.  So on the spur of the moment I sold my bike and bought a single speed.  I won’t pretend the first few days riding it were easy, but I never had to push it up the hill.  Turns out the increased “connection” to the drive train you get without a dérailleur in the way makes a world of difference – and, for some reason, it’s just a hell of a lot more fun riding without all those gears in the way.

Sorry, Pedestrians

I’ll admit that my focus on staying safe while riding has caused me to infringe on the rights of Seattle’s famously inept pedestrians to wander aimlessly about.  Occasionally I might have even made someone walk around my bike (or at least detour around my back wheel) in a crosswalk.

So, to the young jogger who reminded me this morning that I was in the crosswalk at Broadway, thank you.  I will take that under advisement.

Tired of my Rain Bike

The summer solstice is almost upon us, yet I’ve had to break my rain bike out every day this week – and today is shaping up no differently.  Despite its cushy ride and cargo-carrying capacity, I’d rather be on my more sprightly Cassaroll at this time in June.