SF Cyclotouring

Ride reports and other ramblings from a San Francisco cyclist.


$4000 Bontrager Race?

This guy is SOOO high! "Bontrager Steel Moutain Bike" $4000 for a Bontrager Race? Even if it is new-old-stock, it's seriously not worth that much. And it's typical Ebay that such a flagrantly overblown starting bid is accompanied by such crappy photos and minimal detail. At least pump your tires up man!

I smell a scam...


Dave Moulton (of course) gets it:

Critical Mass in the US needs to cease, it no longer serves any useful purpose.


If no one is responsible, then everyone is responsible. It is time to protest against Critical Mass, to urge people not to participate. The idea has run its course and is no longer valid. It is no longer cool to be a part of a lawless mob that disrupts the normal way of life, pisses people off, and worst of all perpetrates violence.

Jobst Brandt on Shimmy

More from Jobst Brandt on what makes a bike shimmy...



The "Brown"trager 69er

Anyone who knows me knows I have a thing for Bontrager frames. If I had infinite moneys and storage space, I'd likely buy up any/all/every Race, Race Lite, Road Lite, Ti Lite (!!!), CX, and older custom frames I could find. I really dig their form-follows-function design! Sometimes I fantasize about what it'd be like if KB was still producing frames, and made a 29er version of the excellent Race Lite frame with the coveted Bontrager composite fork...yum!

Anyways, check out this awesome 3-speed 69er hack that Bob Brown whipped up, based on his ol' Bonty Race frame...read all about it here.


Shimmy is as Shimmy Does...Unfortunately

From Jobst Brandt:

Emphasis in bold is mine.

"Bicycle shimmy is the lateral oscillation of the head tube about the
road contact point of the front wheel and depends largely on frame
geometry and the elasticity of the top and down tubes. It is driven by
gyroscopic forces of the front wheel, making it largely speed
dependent. It cannot be fixed by adjustments because it is inherent
to the geometry and elasticity of the bicycle frame
. The longer the
frame and the higher the saddle, the greater the tendency to shimmy,
other things being equal. Weight distribution also has no effect on
shimmy although where that weight contacts the frame does. Bicycle
shimmy is unchanged when riding no-hands, whether leaning forward or
backward. "

In addition...

"Shimmy is caused by the gyroscopic force of the front wheel whose
tilt is roughly at right angles to the steering axis, making the wheel
steer to the left when it leans to the left. This steering action
twists the toptube and downtube, storing energy that both limits
travel and causes a return swing. Trail (caster) of the fork acts
on the wheel to limit these excursions and return them toward center.

So it's generally non-correctable (unless I decide to ride with my
saddle impractically low) and the 2nd paragraph would seem to imply
that it's more prone in a low-trail bike, where the trail is reduced
and thus the steering-limiting mechanism that works against toptube
and downtube twisting is weakened.

Good grief!

-Jim G


Friction Downtube ShiftersMarathon bike-shimmy debugging session tonight. Status: unsuccessful! Things I've tried so far:

Changed to a different front rack, one that mounts at the fork-end eyelets instead of the cantilever brake studs.

Cleaned out and re-greased the headset.

After noticing a wobble in the rear tire due to the bead not seating evenly, I changed to a completely different set of tires.

Lowered the handlebars; raised the handlebars.

Took off the front fender; reinstalled the front fender.

Thinking that the shimmy might be due to some weirdness with the tension in the bar-end shifter cables, I unhooked those and installed down-tube shifters (tangential note: Mavic DT shifters do NOT index with Shimano 9spd). When rolling the bike around, the steering is much looser/floppier since the stiff SIS cables are absent, but the no-hands riding shimmy persists.

Along the same lines, I unhooked the rear brake cable and rode down my street, but I don't think that helped -- I need to retest. My brain's going a bit fuzzy @ 12:45am.

The only other thing I can think of is to get the head tube faced.

Any other suggestions?


Princeton Tec Swerve vs. Planet Bike Superflash

Found this on YouTube via Candlepowerforums...

IMHO, the Superflash still wins in terms of brightness and sheer attention-getting power!


More Low-Trail & Shimmy Findings

Yesterday I took my 700C P/R on its longest ride to date, a 90 mile journey from SF to Pt. Reyes Station and back. Prior to the ride, I swapped forks, replacing the 40mm trail fork with the 30mm version (actual trail is more like 42/33). I used a front rack + bag that weighs a bit under 10lbs.

I can report that the lower trail fork seems to make the weight of the front bag nearly disappear -- executing a quick turn to avoid a pothole, for example, while slow does not feel overly "heavy" or "floppy". You don't have to wrench the handlebars around to make the bike do what you want. The same was true of the 40mm trail fork, but the 30mm version makes the steering feel a bit lighter, which was nice.

Unfortunately, my bike still exhibits the shimmy whilst riding no-handed. The change in forks seemed to change the shimmy-speed, previously it was around 15-18mph, now it seems to occur at 18-25mph. More weight definitely makes the shimmy worse. Even touching a couple o fingers lightly against the top tube stops the shimmy. I freaked my riding companions out a bit by demonstrating this multiple times. I attempted to make a video of the shimmy, but it didn't really turn out well -- I couldn't hold my camera steady enough to reveal the bike's shimmy.

I also discovered that at around 40mph, this bike has an unnerving speed wobble (riding with hands on bars). Of course, touching a knee to the top tube stops it...but it makes me wonder what'd happen when I'm poorly focused during a long, tiring brevet?

I'm giving up on trying to ride this bike with a front load -- which really sucks because that's one of the main reasons I wanted this frame! Tonight I'm going to remove the front rack, swap back to the 40mm trail fork, and return to using a Banana Bag.

Summary: I'm quite liking the low-trail handling, but the frame's shimmy is a deal-breaker.


200k Mixed-Terrain Brevet-style Ride this Saturday, July 19th

In case anyone's interested (and apologies for the late notice), a few
guys from my rando club are planning to unofficially ride a
newly-proposed 200k mixed-terrain ride this coming Saturday.... The
route starts in San Francisco's Marina district, crosses the Golden
Gate Bridge into the Marin Headlands, winds around Mt. Tam, then takes
you out towards Olema via Bolinas Ridge, back through SP Taylor Park
to Fairfax, then the abbreviated Paradise Valley Loop, to Mill Valley,
up Old Railroad Grade to West Point Inn, then back through the Marin
Headlands and back across the GG bridge. 60/40 split between pavement
and fire roads/trails.


Saturday 07/19, 6:00am: La Ruta Loca Randonnee, a 200k mixed terrain
route. Meet at the Marina Safeway in San Francisco.

This is a *very* challenging ride, it has ~13-14k feet of climbing, ~
40% of the route is done on fire roads. The updated cue sheet can be
downloaded from http://bike.duque.net/ride-calendar.htm (select La
Ruta Loca Randonnee). If you come please make sure you are truly self
sufficient, we cover some remote areas. Also make sure you pack enough
food and liquids. Front & rear lights are probably a good idea.

is just a harder-than-normal group ride that we'll try to do following
brevet "rules" (13.5 hour time limit, controls, etc.)...


Unfortunately, I won't be joining in due to familial obligations.


My Next LED Bike Headlight Project

Not that I don't have too much to do already, but I've been irrationally obsessing over LED bike lights lately. I say "irrationally" because it's mid-summer where I live and the daylight lasts a good long while, making bike lights mostly unnecessary for me right now. I know that will change soon, though. (I should also be focusing on work, and at least a dozen other things, but I digress...)

Part of my light-lust is being fueled by the recent introductions of a couple of commercial dynohub-powered lights, namely the Schmidt Edelux and the Supernova E3. Both of these are attractive lights, and are reputed to be very bright. However, they represent one problem inherent in current LED-based bicycle lights: the fact that technological improvements often happen faster than product development life cycles.

What do I mean by this? Both of the lights above are based on LEDs that were state-of-the-art six months to a year ago. I don't know for certain, but I'd guess that both lights are based on Cree 7090 XR-E LEDs. The efficiency of these LEDs, ranked by their bin codes, improves constantly -- caught up in a sort-of arms race with other LED manufacturers (Luxeon and SSC), Cree seems to produce ever-higher bin codes every few months. Since it takes many months (to a year or more) to imagine, develop, prototype, manufacture, and ship a commercial product, what this ultimately means is that the commercial bike-lights you can buy today aren't using the best components available now!

Additionally, the Edelux and E3 are both single-emitter (one LED) lights. While these designs may be brighter than their halogen-incandescent predecessors, many folks are still choosing to run multiple lights on their bikes for increased output. At over US$100 each, these lights aren't cheap, and mounting two is even more costly. Why duplicate things -- I don't see the need for the extra lamp housing, wiring, switch, etc. required by the second light unit? Why not simply make multi-emitter dynohub-powered lights, with two (or more) LEDs in a single casing? This adds only the minimal cost and weight of the extra LEDs, and is the option most DIY projects take.

Furthermore, in addition to advancements in LED efficiency, new designs are becoming available: multi-core LEDs are the new thing. These emitters basically combine four diodes into a single device with the same footprint as a single-emitter LED (analogy: think four filaments in a single incandescent bulb), quadrupling the light output!

So, my next bike light project will involve getting a dynohub front wheel, and building either a three or four LED light head or a lamp based on a quad-core LED. I'm not sure when I'll get started on this, but the results should be brighter than what I can buy "off the shelf" right now! Plus, I will no longer have to futz with the batteries my other light requires...

Going Nowhere Fast!


Kogswell 700C P/R -- Long Term Impressions

Taking a breakI've now ridden just over 200 miles in just under two months on my Kogswell 700C P/R bicycle, so I feel qualified to offer up some longer-term impressions of the bike.

First, because I don't think I've done so before, I'll offer up a detailed component list:

Frame: Kogswell P/R, 59x700C (S/N: CB70W0093)
Fork: Kogswell 700C, 1-1/8 steerer, 58mm offset (expected ~42mm trail)
Rims: Mavic MA-3 - 32 spokes front, 36 spokes rear
Hubs: Shimano XT
Spokes: Wheelsmith 14/15g
Tires: 700x35 Panaracer Pasela
Pedals: Shimano SPD PD-M515
Crank: Shimano Exage FC-M520B, 175mm/24-36-46
Chain: Sram PC971
Cassette: Shimano 9spd 11x32
BB: Shimano UN-52 113mm
Front Derailleur: Shimano DX
Rear Derailleur: Shimano Deore 9spd
Shifters: Shimano bar-end 9spd
Handlebars: Trek System 2 44cm
Stem: Kalloy threadless
Headset: Kogswell (included w/frameset)
Brakeset: Avid Shorty 4 w/Koolstop Thinline salmon pads
Brake Levers: Shimano 600
Saddle: Terry Fly
Seat post: Zoom 27.2mm
Accessories: Nashbar front rack (modified/customized) with Performance TransIt Pro DX Handlebar bag, Velo-Orange 49mm fluted alloy fenders, Velo-Orange alloy bell, Zefal HPX-4 pump, Performance Forte Terra Lite Stainless MTB Cage (2), SI 90 computer

I've previously written about my initial impressions of this bike (see also), and my longer-term experiences mostly reinforces those first thoughts...

I still really like the fat 700x35 Pasela tires! In fact, I think the bike's strongest suite is the fact that it'll fit these tires with fenders...not many bikes on the market today can duplicate that.

Overall, the low-trail thing has been something of a disappointment, in that there's just not that much explicit difference between this bike and other non-low-trail bikes I've known. Sure, there's a difference, but it's so subtle that if I'd not known what to look for beforehand, I wouldn't have picked up on it. The P/R might hold a straight line at lower speeds somewhat better than other bikes. I haven't noticed any advantage while riding through cross-winds. The bike is definitely confidence-inspiring while riding through fast, swoopy downhill curves -- but that may be due to the fat grippy tires as much as anything else (I need to mount those tires onto another bike and compare). Low trail geometry is supposed to be beneficial for frontal loading of a bike, but I've been frustrated on that with this bike (more on that later). Does it plane? It might -- I was riding up a favorite climb with a friend recently, and I was pedalling at a fairly easy effort since my companion had dropped back a bit. He later claimed that I was ascending the hill at a strong clip, which suprised me because I was in fact trying to go slow to wait for him to catch up!

The biggest problem I'm having with the bike currently is the fact that it tends to shimmy fairly violently during no-handed riding. When I first began riding the bike, I purposely loaded it up "wrong" because I wanted to begin the experience with a familiar set of parameters -- I mounted my usual small, lightly-loaded handlebar bag up front to hold food and extra clothing, and a midsized seat pack behind the saddle carrying heavier items like tools. When riding no-handed, the Kogswell shimmied a bit with this front load, but I attributed that to the fact that the handlebar bag (a Rivendell/Baggins Candy Bar bag) non-rigidly straps and ties onto the handlebars and as a result, tends to swing a bit relative to the handlebars (this bag actually causes a bit of shimmy on two of my other bicycles as well). One of the key characteristics of a classic low-trail randonneuring bicycle, which the Kogswell P/R attempts to emulate, is its ability to carry a front bag while maintaining excellent handling and stability. In fact, it's argued that the front bag helps to reduce a rider's overall brevet times because tasks like eating and adding/removing a jacket can be done on the moving bike, since the cargo compartment is easily accessible. Obviously, to do these things a rider must be able to comfortably ride his/her bike no-handed. As an aspiring randonneur, I added a front rack and bag to my bicycle, but I was dismayed to find that the shimmy problem only grew worse, in spite of the fact that the bag is rigidly attached to the rack and bike!

Kogswell has produced two versions of the P/R frameset. The first version used oversized (OS) frame tubing and was powdercoated a custard-yellow color. While these frames were generally excellently received, some argued that they were too heavy and the ride was too stiff. To that end, Kogswell modified the design for the second production run, and the result is the black frameset using standard diameter, thinner-walled tubing. From this posting to the Kogswell Owners List:

> Is there a summary anywhere of the differences between the first and
> second batches of P/R's?

The down tube changed from 31.8 x 0.6 x 0.9 to 28.6 x 0.6 x 0.9.
The top tube changed from 28.6 x 0.6 x 0.9 to 28.6 x 0.5 x 0.8.

There has been some discussion since then that the new design might've taken things a bit too far -- that low-trail geometry coupled with light-gauge tubing is a recipe for shimmy. At this point, I'm tending to agree with that statement.

My handlebar bag and its contents (map, pen, first aid kit, tool kit, spare inner tube, small digital camera, jacket, small padlock and thin cable, food) weigh 8-9lbs. Assuming a weight of one pound for the front rack gives us approximately a ten-pound front load -- not at all atypical cargo for a randonneuring bicycle. Yet the bicycle shimmies profusely when riding no-handed at speeds of 15-18 mph or more. The bike rides very nicely and handles quite well during normal riding, but I simply cannot ride this bike no-handed for any distance. (For the record, I am able to ride any of my other five bicycles for quite some distance without hands on bars. Also, for the record, I weigh around 145 lbs., so it's not like I'm overly stressing the frame itself.) A recent thread on the Kogswell list prompted me to conduct some experiments of my own...

First, I checked the tires' pressure and ensured that they were inflated to 60 psi (according to my pump's gauge, which admittedly probably isn't terribly accurate) and remounted the handlebar bag with the typical contents. I was able to duplicate the findings of my previous ride, namely that strong shimmy occurs when riding no-handed at around 15 mph. Next, I removed the front bag, and discovered that a slight shimmy occurs now at around 18-19 mph. Third, I reinstalled the bag, and increased the tires' pressure to 75 psi -- again a slight shimmy occurred around 18-19 mph. Fourth, I replaced the front wheel with a similar wheel shod with a 700x28mm Pasela tire inflated to 85 psi -- and the result was similar to #3 above. Fifth, I attempted to tighten the bearing adjustment on the headset, but that didn't seem to change anything.

Nishiki Sport Front Rack+Bag TestFinally, I decided to try the same front load on another bicycle entirely. I mounted a spare front rack on my mid-trail (59mm) Nishiki Sport and attached my handlebar bag to the rack (see photo). I expected this bike to ride like crap with this front load, but in a short test ride I was surprised to discover that it wasn't actually all that bad. In fact, it wasn't significantly different than how the Kogswell felt with a front load! AND that bike didn't shimmy. At all! Ultimately, this makes me wonder if my entire low-trail experiment is a failure!?! There's one last thing to try...I have a second fork with more offset (67 mm), intended to produce around 32 mm of trail on this bike. I need to try that and see what the effects are.

Stay tuned....

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