SF Cyclotouring

Ride reports and other ramblings from a San Francisco cyclist.

7/06/2008

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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2 Comments:

Blogger elybike said...

I recently totalled the front end of my bruce gordon blt, into a cooper mini at full speed.
I replaced the fork with a junk fork from a hybrid, my family was scheduled to leave in 3 days for the summer, so I grabbed whatever was laying around the Bike Kitchen.
The new fork has lower trail and also a shorter axle to crown distance. The handling is significantly better at low and medium speeds. With or without a big bar bag.
I can ride no hands with no problem, unlike before. We did a Boston to New Hampshire ride (in one long day), a few others, last week I did a 100k here in Florida.
I think that the whole fork geometry thing is true, though I don't understand it all. I always felt like the front was slow and unresponsive, but now, it feels totally different. I admit that on long very fast rides, the front end is too responsive and reacts to your input too much. I have yet to do a full loaded trip, front and rear.

6:14 AM  
Blogger Boxer Bikes said...

jimg - I suggest you try out your lowest trail fork and explore the ride/handling characteristics then.

10 lbs. total for a front loaded rando rig is not overly high. With a ~30 odd trail figure and a rigidly mounted bag on a solid rack, you might find the bike handles better.

My experience on the SIR Cascade 1200 bears this out. For the C1200, I made a new handlebar bag. On the 4 passes 600k brevet, I used a taller and slightly wider bag, with a little more weight up front and could not safely ride the bike no handed at most speeds.

The new smaller bag is no taller than the tops of the bars, has no side pockets and has a more rigid internal stiffener. There is little to no sway or flex of the bag when I turn the bars. The rack is completely rigid. I think this was key in eliminating the shimmy.
I also moved two spare tubes and a spare folding tire to a burrito style wrap under my saddle. Less overall weight in the bar bag also contributed to better overall handling.

See this photo for the overall set up: http://www.flickr.com/photos/seattlerando/2618350556/

Note also, how the two rear pockets of the bag are filled and nestle around the rear hoop of the rack - maybe hard to see in this photo, but it's much like the Berthoud/TA/Sologne bag system. I put a full tube/bike repair kit in the right pocket (~2 lbs.) and rider repair kit in the left (.75 lbs). Each pocket also holds a pare tube at the bottom, below the repair kits.
The large pocket on the fron t of the bag holds rain jacket and eventually arm/leg/toe warmers as the day warms up. Fairly lightweight items that are bulky. ~ 1.5 lbs.

The main compartment holds food, space blanket, house key, wallet items, additional cue sheets, control card, etc. Maybe 5-6 lbs.

The burrito wrap under the saddle probably weighs 3 lbs.

In listing all this, I hope to point out that having the weight as close to the headtube of the bike as possible may make a noticeable difference to the bike handling issue. If the 700c P/R has front end geometry similar to the 650b version, our bikes should have very similar handling characteristics. I built my bike with the geometry of Jan Heine's 1952 R. Herse randonneur, which performed so well in VBQ handling tests. 73 degree ht angle, 70mm offset on the fork, mitsuboshi trimline tires, so 30-ish trail figure. worked a charm on the c1200.

Here's a picture of the larger older bag used on the 4 passes 600k: http://www.flickr.com/photos/archivalclothing/2586076728/

- dan b

9:07 PM  

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