Sunday, November 23, 2014

ERB Bike Introduction, or, Presenting: The Freakbike!

This post really needs some theme music to get us started:

My bikes often fall a bit outside the aluminum hardtail mainstream, but this one goes a few steps beyond that. It came on Saturday:

The kids had fun with the packing material:

It was a pretty slow Saturday around the house.

It was a great day for me, though, as the Fedex truck also had my latest Amazon order:

Anyway, I've long been intrigued by the Slingshot bike concept, perhaps ever since a Bicycling article back in the late 80s/early 90s when John Kukoda described the Slingshot as the fastest bike he'd ever tested. More recently, Bicycle Quarterly has done some real testing to validate the benefit of a more flexible frame for increasing a rider's power output. The basic concept is that a flexier frame deflects more under a rider's irregular power stroke, which is then sprung back to fill in the dead spot of the rider's power cycle. On a stiff frame, this power is wasted in trying to move the frame, with no return of this energy.

I've long enjoyed the lively, springy feel of a good steel frame, compared to the super rigid, dead feeling of most aluminum and overbuilt steel frames. My Rawlands and vintage Trek road bikes ride better than my modern Surly or Salsa roadbikes. This concept is hard to find in mountain bikes, where oversize tubing is the norm. This is one reason I enjoyed my Soma Juice so much: the single oversize top tube gave it a nicer ride than stiffer frames.

However, I've been hesitant to take the actual plunge and buy a Slingshot type frame. With my habitual bike flipping, and the low resale on these frames, I knew I would take a soaking if I tried it and didn't like it. This fall, I came into some "found" money when I flipped a Gunnar Crosshairs I picked up off our local Craigslist. With that, I was willing to take the plunge.

The Slingshot was inventor Mark Groendal's first take as an efficient pedaling bike. With the ERB design, he's taken the concept to the next generation, with a different pivot board location that is supposedly effective while both standing and sitting (I've heard the original Slingshot was only effective in one or the other, I'm not sure which). He's now working on the third generation of this concept, Alter Cycles.

Enough introduction. After dinner, I grabbed a Great Lakes Christmas Ale and headed to the garage to get some work done:

The build went pretty smoothly, although the non drive side of the bottom bracket proved tough to thread the cup into, fracturing one of my plastic cups. I used a steel cup that only more or less fit the bottom bracket instead. That was the only snag, however, and I got the frame ready for my first test ride that evening:

In this configuration, I'm running 700c disc road wheels and 34mm tires. While I waiting for the frame to arrive, I was trying to keep my expectations in check. How much better, after all, could it really be? There isn't much information on the web about the ERB, so I wasn't really sure what to expect. My first ride that night was revelatory: if a thin tubed steel bike is so much better than a stiffer bike, the ERB was that feeling a few times over. Each pedal stroke seemed to surge me forward, almost like I had a light tailwind (it was a still nigh). I just went around the block, since I wasn't really geared up for a ride, but when I got back to the garage, I had to jump on the bike and go out again. To me, it wasn't a case of, "hmm, there might be some improvement here," but more of a "wow!" feeling.

It was a good first impression, but I got a chance to take it out today on a longer ride, my usual ten mile Metro Park loop to give it a shakedown and take some better pictures:

My drivetrain is my usual Sram 9 speed, with my favorite crank, a battered Suntour XC Pro with 32/42 rings:

With no front derailer, my plan is to use the 32t ring for mountain bike and the 42t for road riding. I still need to add an inner jump stop to the seat tube.

The ERB frame is designed around 26" wheels, but it will just clear my 34mm 700c tires:

I tried to balance my cockpit between road and mountain biking, with a narrower bar, an On One Mary, than I typically use for off road riding these days:

You can see a chip in the top tube--that's where an Allen wrench dropped about six inches and chipped the paint. The ERB's finish doesn't look particularly durable.

After today's longer ride, I'm still pretty impressed by the ERB frame concept. It seems like the harder I pedaled, the more effective the springback was. It wasn't the light shining and angels singing effect of the first night's quick ride, but I was also moving against a strong headwind. I'm looking forward to experimenting with this frame some more to get a better understanding of how it feels.

Here's the road configuration:

One compromise for the ERB's frame design is the single bottle location, which is right in the spray of the front wheel:

Blech. You can see the tape job on my fork: that's to cover up the red/white paint scheme of my OS Blackbuck fork. After the Gunnar money, finding this fork cheap and used on was the second enabler of this project: it's a short (435mm) fork that can still take a 29er tire, and with extra rake to keep the handling nimble.

My plan is to also run it off road as a 69er mountain bike:

Unfortunately, with today's warm weather, our local trails are a sloppy mess right now, so that ride report will have to wait.

ERB advertises this frame as being 650B capable, but there not a lot of room back there with my 26" x 2.4" Mountain King tire:

I don't see how a 650B tire bigger than about a 2.0" is going to fit. A moot point for me, since I have a very nice set up of 26" Bontrager Scandium wheels to use... and it's only a 1/2" radius change, people!

Ranting aside, stay tuned for more updates as I put the ERB through its paces.

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