Converting my Gunnar Roadie to low-trail 650B, part 2: First ride impressions

What was the fifth-coldest February on record in Madison provided me with many opportunities to work on the 650B conversion of my Gunnar Roadie. Two days ago I had finally reached the point where it was time for the first test ride. It was already late in the day and so I just went around the block—and was like “Woah! What's going on?!” Little did this have to do with the low-trail geometry of the bike, though. For the past five months I had been riding almost exclusively my fixed gear, studded tire Cross-Check, totally messing with my muscle memory of riding a “normal” bike. In any case, the ride around the block was sufficient to confirm that by and large everything seemed to work and Gunnar was ready for a longer test the next day.

On a beautiful spring afternoon I went out on the Southwest Bike Path, one of Madison's most popular bike paths. I got used to being able to coast and not riding boat anchor tires relatively quickly, and after that the bike mostly felt—not that different from its 700C build. I figured that wasn't a bad thing, and once I had cleared the busier sections of the path, I started experimenting to explore the handling of the bike. Putting into words how a bike feels is difficult. Probably the best way to describe it is that the bike goes exactly where I want it to go, with high precision. The smooth rail trail didn't provide opportunities for, say, high-speed cornering, but adjusting my line a bit felt very precise and required little steering input.

Low-trail geometry is sometimes said to feel unstable at low speeds, but I didn't really notice that. Riding with no hands can be another point where low-trail bikes are different. It should be noted that in general I'm not particularly comfortable with no-hands riding—I suspect that my scoliosis is part of the issue. When taking the hands of the bars, the bike immediately starting shimmying; however the bike stabilized and the shimmy stopped after only a few oscillations. I will have to explore this further. With hands on the bars, shimmy did not occur at all, despite using a regular ball bearing headset. (Roller bearing headsets with their increased friction are said to be a remedy for shimmy in low-trail bikes). Of course, I didn't do any fast descents on this ride.

What did feel weird was getting out of the saddle. It was very different from my Cross-Check, but also different from the 700C build of the Gunnar. However, it seemed like something that I quickly got accustomed to.

One thing to keep in mind with all this is that the bike didn't carry any load. I had taken off the Carradice saddlebag, and the Nitto front rack remained empty. For some low-trail bikes, having a front load apparently is almost a necessity to achieve acceptable handling. This doesn't seem to be the case for Gunnar, and I'm curious to see if/how things change once I add a handlebar bag.

A few remarks on the Panaracer Col de la Vie tires: Using the canonical Frank Berto chart, I pumped the front to 3.5 bar (~50 psi) and the rear to 4.1 bar (60 psi), making them about 35 mm wide (nominally they're 40 mm). While they felt fine, I must say that I didn't have a "magic carpet ride" experience compared to the 25 mm Conti Grand Prix 4000S that where on the bike previously. The Col de la Vie is, of course, what is considered to be a budget tire that didn't fare too well in the tire test by Bicycle Quarterly. Also, the SW Path is smoothly paved, canceling out the potential advantages of wider tires. Aside from subjective impressions, I did end up with a few personal records on Strava, despite not trying all that hard. I'll do some more performance tests on stretches where I more have reliable Strava data from Gunnar's 700C days.

Converting my Gunnar Roadie to low-trail 650B, part 1

My 2002 Gunnar Roadie is the best bike I've ever ridden. It's fast (it's painted orange; so what did you expect...), looks good, is reliable. Since I first built it up in 2010, I've made some changes, but they were mostly minor -- Grand Bois handlebars replaced the modern bars, as did a 1" steel stem the 1 1/8" aluminum stem, and I upgraded to a generator hub. But now it's time for something more drastic: Converting to 584mm/650B wheels and a fork that will make the bike low trail.

Gunnar with 25-622 wheels/tires

Why change an already great bike?

There are two main reasons for this project. The first one is that there is one shortcoming of the frame. It was built to accommodate tires up to 25mm wide, without fenders.  I can actually make 28mm tires work, but the clearances at the chain stay then get a little sketchy. Relatively narrow tires have served me pretty well so far. A good tire in combination with the compliant carbon fork make for a comfortable ride, and I've even ridden pretty rough gravel roads on Gunnar. The lack of fenders, on the other hand, is limiting, turning Gunnar basically into a fair-weather bike. I have little patience for getting road spray all over myself, and when the forecast predicts rain, I therefore switch to my fully-fendered Cross-Check. The reason for going to low-trail at the same as changing wheel size is curiosity. Bicycle Quarterly, my favorite bike magazine, has long praised the advantages in handling that low-trail geometry and front loading can bring. Now I don't nearly perceive high trail and rear loads as pernicious as some people make it to be. I regularly ride my Cross-Check with two Ortlieb Back-Rollers full of heavy groceries and yet I'm still alive. But then of course I lack a point of comparison.

Converting Gunnar is thus the answer to these two points, unlike converting my Cross-Check with ample clearance for wide tires and fenders. I'm on a tight budget and so I spent several months accumulating the parts required for the conversion: A 1" threadless Rawland Stag fork, Shimano Ultegra 6600 rear hub, Shutter Precision PV-8 generator hub for the front, Pacenti SL-23 rims, Sapim double-butted spokes.

Brakes

Currently I'm running Dura-Ace caliper brakes with a reach of 44mm. Switching to 584mm rims necessitates another 19mm of reach for a total of 63mm. At the local community bike shop I found a pair of Mafac Racer centerpull brakes that at least should work for the rear. The Stag fork is intended to be used with cantilever brakes; so I might do centerpull in the rear and canti in the front.

Nice pair of Mafac Racer centerpull brakes

Clearances

There are two, interconnected challenges with the conversion, tire clearance and ground clearance. As I said, currently the largest 622mm tires that fit are 28mm wide. A 584mm wheel moves the tire further towards the hub and therefore increases clearance at the chain stays—but not by much. The way to figure this out in advance is to measure the distance between the chain stays at 320mm distance from the rear axle. I got about 40mm, but the measurement is a little finicky. So in the best case, I could fit a 38-584 tire without fenders—which of course somewhat defeats one of the main reasons for this conversion—or a 32mm tire with fenders. With the latter option then comes the question whether my pedal-to-ground clearance is still going to be sufficient. When using a typical wide 584mm/650B tire like the Hetre with its 42mm diameter, the outer diameter of a wheel is actually about the same as that of a 622/700C wheel with 28mm tires. Using a narrower tire will lower the bottom bracket and consequently lead to potential pedal strike in corners. The Roadie probably has a bottom bracket of 70mm (though I have to confirm this by measurement), which is on the high end for a 650B conversion, especially when running 175mm cranks.

Headset

Low-trail bikes can have problems with shimmy more frequently than high-trail bikes. One possible remedy is the use of a rollerbearing headset to slightly increase friction. For now I will stick with the headset I already have and see how it goes. 

What's next?

I'm still waiting for some wheel parts to arrive before I can build them up. I also haven't decided what to do about tires yet. I'm hesitant to spend a lot of money on tires that then potentially are to wide to fit the bike. I could also potentially go for narrow-ish tires in the rear and 42mm tires in the front—but that doesn't make that much sense given the load distribution of a bike. I will report back once I'm getting closer to completion of this project.

Experiments with measuring bike geometry

The current weather in Montreal has kept me indoors more than I wanted. Inspired by an article in the current issue of Bicycle Quarterly, I decided to measure the geometry of my Gunnar Roadie.The article in BQ describes how to measure bike geometry from a photograph, and an older article gave instructions how to measure directly on the bike. As a quick summary: measuring on the bike works better for almost all dimensions but trail and fork rake. Trail and fork rake can be measured on a picture, but it's hard to get them accurately.

Measuring angles

For measuring angles, using a digital angle finder or an angle finder app for your smartphone is the best option. According to the interwebs, the angle finder apps are pretty accurate. The angles you need are that of the seat post, the head tube and the top tube. The top tube angle is only important for calculating the effective top tube length, as described below. So if you plan on measuring the top tube length directly, you can skip that step. For most bikes, seat tube and top tube angles will be somewhere between 70 and 75 degrees. Top tube angles used to be 0 on most bikes, but after the sweeping success of compact geometry with sloping top tubes, there now is a large range of angles. In order to get good measurements, measure multiple times and make sure that your angle finder is flush with the frame. Many frames have butted tubing that will be thicker near the intersections of the tubes and you should thus measure in the middle of the tubes.

Measuring lengths

The seat tube is probably the easiest thing to measure. The cranks are somewhat in the way of putting a ruler on there, but it's still easy to get a good measurement. Just make sure to note which measurement you're taking: either center (of bottom bracket) to center (of top tube intersecting the seat tube) or center to top (of seat tube). In addition, you will probably already know this number, as this still is the most common way in which manufacturers size their frames.

The top tube is a little bit more tricky, at least if it is a sloping top tube. In order to measure the effective top tube length you have to put a level on your ruler and then measure the distance from the center of the head tube to the intersection with the seat tube (or the seat post as its extension). I find this pretty difficult to do properly, and fortunately there is another way by employing the powers of trigonometry: You'll need the length of the actual seat tube and the angles of the seat and top tube. Using the laws of sines, you can calculate the effective top tube length x as follows:

$x=\genfrac{}{}{0.1ex}{}{\sin \gamma \cdot a}{\sin \beta }=\genfrac{}{}{0.1ex}{}{\sin (180-\alpha -\beta )\cdot a}{\sin \beta }$

Another relevant dimension is the bottom bracket drop, that is the distance from a line between the two wheel dropouts and the center of the bottom bracket. Jan Heine suggests tying a string around the front and rear quick release skewers and then using a ruler to measure the distance from the string to the bottom bracket. You have to correct that measurement with the radius of the skewers.

Next is the front-center distance, i.e. the distance from the front wheel axle to the bottom bracket. The problem is that the fork has to be completely straight in order to get an accurate measurement--something not easily to achieved. Jan Heine suggests measuring on both sides and then making sure to get identical readings, but I found that rather difficult.

Now we get to the tricky part: measuring fork rake and trail. I won't go into the discussions if high trail or low trail are TEHBESTTHING(tm) and instead only show how to best measure trail. Measuring trail directly is almost impossible. Trail is defined as the distance between where the front tire touches the ground and the extension of the steerer axis, as shown in the following figure.

Fork rake r and trail t

Projecting the head tube and the vertical axis through the hub onto the ground accurately just doesn't work properly. [1] Fortunately, you can use the fork rake and wheel diameter to calculate the trail. Measuring the fork rake is easier than measuring trail, but it's still tricky. Bicycle Quarterly use a custom made tool or they measure rake from a digital image. If you only have access to the image of a bike, it's even possible to get all of the above measurements from the image; however, I had a hard time producing a distortion-free image with the lenses at my disposal.

First, take a picture of the front part of the bike. Using your image editor's (I'm using Photoshop) measuring tool, rotate the bike so that the head tube angle matches the value you got from the angle finder. Measure some other tubes, too, to see if and where there is distortion. In addition, draw a circle and see if it is well aligned with the rim. If that shows too much distortion, take another picture and repeat the process. Now you will determine the scale of your image. Draw a vertical line through the hub and measure the distance from the center of the hub to the outer rim. It doesn't really matter which unit of measurement your software uses. On your bike, this distance is a known variable, and dividing the real value through the measured value will give you the scale of your image. With my bike, I measured 1.729 in the image and by dividing 316 (622mm bead seat diameter plus 10mm, then divided by 2) by 1.729 I got a scale of 1:182.8. It is a good idea to repeat the measurement a couple of times on different sections of the rim to once again control for distortion. I measured 1.729, 1.758, 1.651, 1.524, showing that there is still a good deal of distortion. One might be tempted to just take the average of these measurements, but since distortion is not random, this is not advisable. It is preferable to keep taking more pictures, with different lenses and at different angles to achieve a minimum of distortion. For now, we'll just assume that the 1:182.8 scale is correct.

Now we can actually measure the rake: Draw a thin line through the steerer axis, extending it all the way to the end of the fork blades. The draw a line parallel to the steerer axis through the hub. Parallel lines are easiest to get with copying and pasting the first line or drawing a rectangle. Measure the distance between the two parallels. In my case, this was 0.240, yielding a rake of 0.240 * 182.8mm = 43.9 mm. Common values for fork rake are between 40mm and 75mm, with most forks being in the lower range of this spectrum.

Using fork rake, head tube angle, and wheel/tire size you can now use the excellent online trail calculator to get your bike's trail. For Gunnar that would be 54mm trail with a 25-622 tire. Since small measuring errors in any of the measurements can throw the calculation off easily it's hard to say how accurate this value is. It would put Gunnar in the medium trail range (Heine gives 25-80mm as the common range).

To conclude, measuring a bicycle's geometry, either on the bike or from a picture, can be tricky. For many bikes you will be able to get the correct values from the manufacturer (please note, though, that most likely there will be minor aberrations from the values on your frame as artefacts of the manufacturing process). If you want to measure your own frames it might be a good idea to start with a bike with known dimensions to give you an idea of how good your own measurements are.


[1] I wonder if one could use a laser pointer attached to a concave piece of metal that matches the head tube's curvature. I've ordered a laser pointer and tinker around with it a bit.

A whole lotta bike

Last Sunday was a day full of various kinds of bike-related events: I volunteered at the Hollenbecks Spring Classic race, organized by the FLCC, and I did a lot of riding. Leaving the house at 7 am, I rode Gunnar out about 30 km to the start of the race, Hollenbeck's Cider Mill in Virgil. It hadn't cooled down much during the night and the forecast predicted a hot and potentially thunderstormy day. I coated myself in a thick layer of sunscreen and hopped on the bike in just shorts and a short-sleeve jersey. Because it was early Sunday morning, I took the most direct route, following NY-366 and 13 to Dryden, and then 392 to Virgil. As expected, there wasn't much traffic and the only thing I was struggling with was the fact that I can't eat that early in the morning and was therefore pacing along on an empty stomach. Nonetheless, I got to Virgil well before the scheduled pre-race meeting for the corner marshals.

After we had been assigned our corners, I had about 35 minutes left before the start of the race and so I decided to ride out to the corner instead of getting a ride. The distance was 9 miles and involved one large climb, meaning that I'd have to put in quite a bit of an effort to make it in time. The racers warming up on 392 at a more leisurely pace were probably wondering why that guy with a Carradice saddle bag and baggy shorts was passing them at maximum effort... Well, I got to my corner just before the other volunteers arrived by car and then had 3 hours of flag waving, videotaping, and waiting for the next pack of riders to come through. After the last rider had made past our corner, I rode back to the cider mill and after hanging around for the little ceremony for the winners, I decided to ride back immediately in an effort to avoid getting t-stormed upon.

On the way to Dryden I could really feel my legs and I decided that I definitely needed water, electrolytes, and calories. Well, what better way to get all these things at once than going to McD and having large fries and a large coke? And indeed, this made me feel much better! So I got going again and thought of ways of lengthening the way back to Ithaca in a way that would make my total kilometrage that day get over 100 (at the McD in Dryden I was at 70km). Initially I thought I'd just ride out to the airport and take NY-34 back into town instead of following Upper and Lower Creek Road into campus. However, as I was feeling really good and the weather had gotten better again, I decided to something a bit more crazy: ride out to the airport but then not return to Ithaca but instead follow the route of the FLCC "Almost Genoa" ride that I had done a couple of weeks ago. And that I did.

For the part of the route that heads north, I was doing fine. The strong winds were mostly coming from the side to back and the route is rather flat. The climbing along NY-90 made me feel my legs again but the prospect of getting to the gas station at the intersection NY-90 and -34 propelled me forward. At the gas station I took a quick break to down a bottle of Gatorade -- and made the mistake of not also topping up my water bottles. On the way back south, first following 34 and then Salmon Creek, I had to head into the wind (even though not as badly as I expected it to be) and my body got more and more complainy. My butt hurt, my legs and upper arms were tired, and overall I felt a bit bonked. The steep climb up Brickyard Rd certainly didn't make things better and I was also running out of water. Anyway, in the end I made it all the way home, having ridden almost exactly 150 km, at an average moving pace of 25 km/h. Pretty epic, I'd say.

Lessons for future long distance rides:

• find a way to deal with the breakfast issue. Maybe I can force myself to have some liquid calories in the morning?
• The Brooks did a good job but nonetheless my butt did hurt quite a bit. Not sure what to do about that. 
• Gunnar rode like a charm. I think running 700x23c tires works very well, even over long distances. I might raise the handlebars a little bit to put less stress on my arms. 
• Drink more. Eat more. As much as I know how important this is, on the ride I still keep on ignoring this knowledge.

As soon as I have the time, I'll try the 200k to Lake Ontario and back.

New Front Wheel for Gunnar

I don't really have a good excuse for doing this, but I've built a new front wheel for Gunnar. As you might remember, currently he's running Wolfgang's old Alex-DA16-on-Deore 36 spoke wheel. While this works just fine, the internal rim width of the DA16 is 16.3 mm (at least according to their website) and thus technically a teeny tiny bit to small for my 700x23 tires. But I admit: this is a lame excuse for my urge to build a new wheel. An additional boost to this urge actually came from a gift from my friend Löby, who gave me an old but functional dial indicator. The idea is to mount it to my truing stand, theoretically allowing me to true wheels down to 0.01mm. Well, I'm still working on the attachment to the stand which turns out to be a bit tricky.

But I've built up the wheel anyway. It's a 32 spoke Mavic Open Pro with DT Swiss Comp 2.0/1.8 spokes on an Shimano Ultegra HB-6600 front hub. After lacing the wheel the wrong way twice, three times was the charm and now it's all trued and tensioned. Figuring out the correct spoke tension was a little tricky because my Wheelsmith tensiometer's calibration table only gives values for their own double-butted spokes which are 2.0/1.7 and not 2.0/1.8. But since the absolute value for spoke tension is not that crucial anyway (Mavic recommends 1050-1100 N) it shouldn't matter too much.

One final note about the wheel: the Open Pros don't come with a wear indicator. Therefore I've measured the thickness of the rim's sidewall. A trick to do this: attach a little magnetic ball to your caliper in order to get around the flange of the rim. My measurements came to almost exactly 1.5mm. This should give me a good point of reference for judging rim wear.

FLCC Sunday Ride, Attempt 2

After our somewhat sucky experience with last week's FLCC Sunday Ride, I thought I'd give it another shot, this time not with the accomplice, but with my German riding buddy Tim. We met downtown at 9:45 and rode up the hill to the East Hill Plaza meeting place. There were about 8 people there already, once again all in Spandex and on road bikes. Well, this time I was prepared and had brought Gunnar (no spandex, though). We got going just a bit after ten and the pace was fairly fast, but not too fast for my (or Tim's) taste. We dropped a few people during the first part of the ride but re-congregated at the Warren Rd post office where we met another rider. From the airport on, we had to struggle with a fierce wind from the North and at some point I was feeling a little bonked. Well, fortunately the Clif Bar consumed during the stop at the post office kicked in quickly and I was feeling fine again. So fine that I actually did quite a bit of pulling and ended up in a breakaway group of three people. Our only other stop was at the gas station at the intersection of NY 90 and 34, where we waited for most of the other riders. From there on, the riding-into-the-wind was mostly over and we zoomed down Salmon Creek valley into Ludlowville, up the hill to Lansing and back to campus on Warren Road. After about 3.5 hours we were back at the East Hill Plaza parking lot. Verdict: great ride, awesome route! But don't come to a Sunday Ride if you're not well trained and want a truly relaxing ride on your non-road bike. Unless you don't mind being dropped quickly.

Gunnar

Finally the weather has been nice enough for me to take out Gunnar for a couple of rides. After a short loop through the city and a ride to the FLCC spring seminar two Sundays ago, yesterday I took Gunnar on a real test ride, out to Taughannock and back on Route 89. And Gunnar rides like a charm. I pushed it pretty hard and averaged at 30.7 km/h for the out-of-town portion of the ride. I think the geometry works pretty well for me, but I will keep tinkering with it: saddle height is maybe still a bit too low, but the current seat post is already at its max. And if I have to get a new seat post anyway, I might get one with a different set-back. Currently my KOPS (knee over pedal spindle) position is about 6 cm behind the spindle and my saddle is as far forward as possible. I'm well aware that several cycling gurus are rather skeptical of the KOPS method and their arguments are making a lot of sense to me. But given that my saddle is at the margin of adjustability, a zero-setback post would give me more options to tinker with my position. Probably I should just ask Glenn for advice. Handlebar height might get readjusted downwards, too. At the moment my posture is fairly aggressive, but I think I could drop a spacer or two and still be comfortable.

I'll go for another ride with another German guy today and we'll see how Gunnar feels after 2 or 2.5 hours. I definitely expect my behind to hurt, as the Selle Italia Flite Gel Flow (I have the one without titanium rails) saddle is just too tiny. My knees might also be a trouble spot, as I messed them up a bit yesterday, courtesy of a downward sliding seat post...

I also shot some outside pictures of Gunnar. I hope you'll enjoy:



Odo Wolfgang: 3924 km
Odo Gunnar: 991 km (point zero is at 954 km)

More ride, less blog

What's a good indicator of the coming spring? That my kilometrage is up and my blog-postage is down.

Just a quick maps-con-pics from last week's lovely ride to Taughannock Falls. If you want more details: I think the accomplice might blog about the ride soon.



Oh, and I've done the first couple short rides on Gunnar. Verdict: nice ride, but still needs some adjustments. More detailed account to follow sometime.

Upgrade for Gunnar

Courtesy of the yearly sale of German online bike shop Rose, I've ordered a little upgrade for Gunnar. As you might remember, currently I have the old Alex DA-16/Deore wheel from my Cross-Check installed. The upgrade will be a Shimano 32H Ultegra Hub with DT Competition spokes on a Mavic Open Pro hub. That should shave a couple grams off of Gunnar's weight, look nicer, and be more appropriate for running thin tires. But first I have to wait for my Germany visit in order to pick up the components.

Gunnar's weight

I ain't no weight weenie but I nonetheless wanted to add the weight the previous post about Gunnar. With the addition of Shimano PD-M520 pedals, two bottle cages, and changing the tires to 23mm Michelin Krylions I ended up at about 10.3 kg (measured with bathroom scale). I had hoped to reach the 10 kg mark, but I suppose with a 62cm steel frame that's not easy.

Gunnar is ready for a ride

Okay, I've finally finished building up Gunnar and have had a chance to take some pictures for your (and my) enjoyment. Isn't he a beauty? Due to poor weather and salty roads I haven't had a chance to take him for a ride but hopefully it'll get better soon.



Now the nerd facts:

Gunnar Roadie 2002 62 cm frame
Shimano 105 ST-5600 brifters
Shimano Dura-Ace BR-7700 brakes
Shimano 105 RD-5600 rear derailleur
Shimano Ultegra FD-6500 front derailleur, clamp-on
SRAM PG-1070 12-27 10 speed cassette
SRAM 1050 chain
Selle Italia Flite Gel Flow saddle
Bontrager Select 27.2mm seat post
Powerdrive BC1.37x24t 68mm shell bottom bracket
FSA Gossamer 50/34 compact cranks
3T Forgie stem, aluminum, 120mm
3T Forgie bar, aluminum, 44cm
Cane Creek S2 headset
Mavic Cosmos 28 spoke rear wheel
Alex DA-16/Shimano Deore front wheel

Some of the components, like the front wheel will probably be replaced in the near future and I still need pedals, but my main goal was to get to a functional and affordable quality build ASAP. And in that I've certainly succeeded.

Brakes!

Quick ebay update: I'm now proud owner of a set of Dura Ace BR-7700 brakes. Still missing: Brifters, cassette, front derailleur. Frame scheduled for delivery tomorrow.