Maiden Voyage - GB4 36 Custom

So first, I’ll confess my shame. My new GB4 36 arrived from U-Turn last Friday, and it took me 5 days to get to its maiden voyage. But last night was the night, and the journey was only sweeter for the anticipation. I’ll get to a more formal review later in the proper forum, once I’ve knocked off a hundred miles or so and can speak from an educated standpoint. This post is just about the joy and challenge of taking a super-fine machine out for its first journey.

Getting it ready was pretty straightforward. The packing was great, everything came through in great shape, nothing was sticking out of the sides of the boxes, and all that really needed to be done was install the pedals, mount the wheel, tighten down the bearing holders, and program the computer. John Childs was kind enough to come over on Monday night and help make sure I didn’t botch the wheel install, but that was mostly just a good excuse to have a couple beers and down some of Marie’s excellent homemade shepherd’s pie. George’s bearing holders are very precise, and the wheel dropped in beautifully. By that point it was getting dark, so I knew a ride was out. That said, you can’t have a brand new custom 36 sitting there assembled in front of you and NOT give it a try. I was worried, though…I hadn’t been on a Coker since January, and I really didn’t want to blow my first free-mount attempt. Call it superstition, but I wanted to nail the first mount. The worry was doubled having Childs there, because he’s the person I wipe out in front of the most. Turned out to be a non-issue, even with him watching. I backed it up half a turn, walked forward, and hopped right up the first time. Good Luck Omen #1.

So due to other commitments, I couldn’t ride Tuesday…another agonizing delay. Finally Wednesday came, I got home from work, and after a few laps around the neighborhood to get things adjusted and snap a few pics, I was off. About time! I headed right for a long gravel trail out of my neighborhood, trying to think through the ideal route for a test drive, with some good climbs, steep downhills to test the brake, and some gravel and dirt trails just because.

The first section was pretty flat, giving me a chance to check out the basic speed and handling. The GB with U-Turn’s wheel and higher quality bearings is much easier to pedal than my stock Coker was. Very smooth and very fast. In my previous Cokering, I couldn’t really imagine shifting to shorter-than-stock cranks, but I found myself thinking about that very quickly here. I pretty quickly got up to max pedal speed (for me), which according to both my fear factor and the computer was faster than I’ve ever gone by about 3 mph. I thought the wider hub would really take some getting used to, but it felt comfortable right away.

After a short paved section through the edge of a thick wooded area, the path I was riding comes out of the trees and takes a sharp turn to run through a large grassy field under some big power lines. I came around the corner at about 5 mph and rode right into a group of three deer that were browsing the grass at the side of the path. They were literally less than ten feet in front of me, and if they hadn’t jumped pretty quickly, I had a real chance of either hitting one full on or UPD-ing into one. But not being on a 36” wheel, their ability to quickly accelerate saved the day. Surprisingly, they really didn’t get spooked…they jumped about 30 feet away, then stopped and went into a slow walk into a stand of trees. This gave me the opportunity to dismount and snap a couple pics. It was quite the adrenalin charge to get so close to this wildlife on my uni, and I’ll consider it Good Luck Omen #2 for my new GB4.

Flats, speed, and wildlife out of the way, I headed for some hills. As part of my Moab prep, I had switched to muni riding exclusively after January. With a four month hiatus from the big wheel, I was a little worried about climbing with it, but was very happy to find that the progress I’ve made in climbing on my muni mapped right over to the 36. Hills that used to leave me sucking wind if I could climb them at all seemed much easier. The GB/UT prototype handle provided a very solid platform for pulling, and there was no noticeable wheel flex during the climb. I did seem to hit the side of my thighs a couple times on the crown, but that was pretty easy to adjust for.

My braking skill from my muni—unfortunately—did not transfer over quite as well. I made the mistake of having my first downhill brake attempt be on one of the steepest paved hills in my neighborhood: I can get down this no problem on my muni, with or without brake, but on the 36 I got to about the halfway point and things started going wrong. Braking on a 36 requires a much more delicate touch, and it’s also a lot harder to make micro adjustments to make up for inconsistent application pressure. At one point, things got wobbly, I squeezed the brake tighter, started to go over the top, released the brake, and had the GB shoot out from under me. It bounced and rolled, I just bounced. Wipe-out #1…there always has to be a first one, right? Over the rest of the ride, I had a chance to practice braking on some longer hills also, with sections of varying steepness. In the process I UPD-ed backwards and over the top, the latter resulting in a nice stripe of rash above my knee. George and U-Turn: you’ll be glad to hear that the front of your handle provided sufficient protection for the computer. The uni went down hard, and everything was protected. By about my fifth descent I was starting to get the hang of it. Next ride I’ll be going back to that little hill in the above link, and I’ll make it down. Then I’ll turn around and crank my way up it. You can only take so much lip from a stupid hill…

Since I was falling off anyway, I took the opportunity to check my cycle computer. Seven miles… I was only about a half mile from my house at this point and was feeling kind of tired from the climbing and wipe-outs. I started to head for home when that little Fred Flintstone landed on my shoulder, whispering “If you don’t get to double digits on your Inaugural Ride, you’ll be a Wimp For Life (WFL, or “wiffel”). Yeah, I thought, you’re right Fred. Can’t limp home now without hitting the decade mark…better get in some more climbing and braking practice. Turned out to be a good idea, since otherwise I’d have missed a really nice sunset.

One thing was a bit off: I felt like the uni was “pulling” a bit to the right, which is to say I felt like I was having to lean slightly to the left (i.e. pushing my hip slightly to the right) just to keep going in a straight line. I’m sure it’s just something slightly out of adjustment, and that something might just be my brain. The wheel is absolutely true, and is a work of art, so I’m ruling that out. Not sure what else might be a factor. Airseat inflation? Seat angle? Wheel housing in the bearing holders? Any recommends from the pros on why it might feel that way?

I’ve created an album of shots of my GB4 36 Custom, and it can be found as the last album at this link: There are some shots in there showing the arrival, boxes, unpacking, etc…, plus the final assembled road beast, deer in the trail, etc. All in all, the Maiden Voyage was a great success. The GB4 36 rode like a charm, the U-Turn wheel and overall build-up is great, I crashed it good a couple of times, I bonded with deer, and I made it to double digits even though it brought me home after dark. It was a good day. Total miles: 10.3; Average speed: 7.6; Top speed: 16.3; total pedaling time: 80 minutes. George and Dave: you have built a wonderful machine, and I’m proud to own it. What a ride! I’m looking forward to the many thousands of miles ahead…


Re: Maiden Voyage - GB4 36 Custom

If you thought seeing the deer was a kick, wait till you do a night ride with a bright light. Then you’ll see all sorts of glowing eyeballs looking at you from the sides of the trail, from the woods, from up in the trees, everywhere. It’s freaky. :slight_smile:

The problem with the uni feeling like it is pulling to the right can be due to several things. On the Coker I’ve found that it is usually due to something being out of center with the seat. If the padding in the airseat gets out of kilter and leans one way then the uni is going to do the same. We’ll have to find out how U-Turn put the seat together and how the inner tube is stuffed in there. Maybe it’s a little lopsided. It could also be due to needing to get used to the wider hub. We’ll see.

My max speed on my GB4 Coker is only 15 mph. I have no desire to push it beyond that right now.

Say, talking about max speeds. What did you end up setting your cycle computer at for wheel size? Maybe your setting is making you go faster than you actually are. There’s no way that you can be faster than me.

Thanks for the nice writeup and photos, Tom.

It’s nice to see the crash protection is working well. It has worked well on others and there’s some delicate stuff up there (Magura brake cables, cyclometer head, headlight). The handle was designed specifically to provide crash protection for those three components.

You will quickly get used to the brake. I did the same thing with mine - I went flying about 12 feet horizontally. Now I use it all the time (when I’m functional).

As far as the twisting goes, there are several things to think about, not in any particular order:

  1. You may not be comfortable riding at night, so that your body is drifting into an “easy bailout” mode. More rides will fix this.

  2. You may just need time with the new configuration. More rides will fix this.

  3. Your seat may be a little high, so that one of your legs (probably dominant) is optimizing itself at the expense of the other.

  4. The seat may not be on quite straight.

  5. As John said, there may be seat support issues. These seats are really tricky and very individual. However, at first just play with the air pressure, because reconstructing the internals is a lot of work.

  6. Find neutral ground to ride on (that is, non-sloped, non-crowned hard surface) and see if the problem still exists after riding for an hour or so.

All but the second half of #5 require little work but riding, so I recommend doing them first. However, if it should come to that, you might at first revert to a “normal” air seat using a dogbone (I did send you one, right? If not, I will) and simply replacing the innards rather than try to rework the innards. Then you can try the innards again later without having torn it apart (for the non-Tom Blackwoods, the “innards” of the seat include a constrained air tube plus Miyata foam).

I look forward to more excellent writeups!

Re: Maiden Voyage - GB4 36 Custom

I find this quite interesting as I always drift to the left. This is regardless of the surface I am riding on as I do the same whether I am on a nice flat hall floor, on tarmac or on paving.

I have checked the seat and I’m pretty sure it is on straight. I’ve been experimenting with seat height and I’m pretty sure I have that right. I may, of course be wrong on both these points, but at least I’m riding far enough to notice the drift (4 pedal strokes).

Is this a characteristic problem with cokers or just something that you notice quicker because you go so far with each pedal stroke?

Anyway - a very nice write up of what sounds like a fun ride.


Re: Re: Maiden Voyage - GB4 36 Custom

Well unless you botched the chalk marks during the roll-out, it should be correct. The tale of the tape was 110 inches, which according to the online conversion engine at sciencemadesimple equaled 279.4 cm. I rounded down to 279, which might be responsible for the discrepancy. :stuck_out_tongue:

I was stunned by the reading also…as I noted, it’s 3+ above my previous fastest. But everything else looked right…I’ve ridden the route before and the mileage made sense. Maybe we can try side-by-side this weekend and check the calibration.

Re: Re: Re: Maiden Voyage - GB4 36 Custom

If you want to go twice as fast, or three times, I have some extra magnets here… :wink:

Re: Re: Re: Maiden Voyage - GB4 36 Custom

I’ve been using Nathan’s measurement of 2776 mm. His number came from measuring 3 revolutions and includes riding wobble so it gives road speed rather than wheel speed. But that number was on a stock Coker wheel. I’m not sure if the Airfoil rim will make a difference.

Some threads about Coker rollout distances:

Nathan’s measurement
Calibration thread started by Klaas Bil
Calibration thread started by Ken Fuchs

It’s too early in the morning for me to do any math. I’m curious about how much of a difference in MPH your setting of 2790 mm and my setting of 2776 mm would be if we were both going the same RPM (cadence). I suspect it wouldn’t be much. Probably less than the resolution of the cycle computer. Maybe. But I don’t feel like doing any math to verify.

Your number is close to the measurements for no wobble while mine is close to the measurements including wobble.

I use the Google calculator for conversions and calculations. I love the Google calculator.
110 inches in mm

Re: Re: Re: Re: Maiden Voyage - GB4 36 Custom

Seems to me there was plenty of wobbling going on as tried to get that one full revolution while clinging to my wife’s truck…

Maybe on our weekend ride we can find a measured mile someplace and see how our computers compare against it. I don’t want to go too fast…I just want to set me computer so I can remain a little faster than you. :wink:

How are we going to keep up with you on the Iron Horse Trail with you going so fast and us trying to dodge a herd of wild animals chasing you? I can tell you without seeing it that the seat is too low. Please fix that for me before I ride it.