Building a rat bicycle: road frame with mountain bike parts

I never really know how one ends up with a rat bicycle. They just kind of happen. You buy bikes and parts and swap them around until you’re left with a pile of mismatched metal and rubber. And if you stare at the pile long enough you just might be able to manifest a bike out of it.

Rat bicycle or pile of parts?

In my case I had a bunch of spare mountain bike parts and no mountain bike frame to put them on. I did however have my favorite heavy road frame and some 650b wheels that were rim brake compatible.

But a pile of mismatched parts does not in itself make a bike. Especially when those mismatched parts need to carve out a niche in my already robust quiver. I needed a reason to build a bike, but what has changed?

I had recently built up the Niner Air 9 as a replacement for my monstercross bike. (If you want to know why, go ahead and read this). I converted the monstercross back to a plain old hardtail, which I recently sold off.

The gap in the quiver was now apparent. Without a do it all bike, a big old dad bike sized hole was staring me right in the face. Not just any old dad bike though, a dad of young kids dad bike.

This dad bike needed to be a workhorse. A bike that could tow a trailer and loaded racks. One capable of hauling two kids in a Thule trailer, a third on a seat, loaded panniers with other kid stuff. I also like getting places pretty fast. A loaded request no doubt, especially for a rat bicycle.

The rat bike build

What did I hang on this road frame? And where did these parts come from?

It’s no surprise that many of these parts came from different builds of previous bikes and that they were almost all compatible. But that makes sense right? The parts you have are all parts you bought for one reason or another to work with the other parts that you have. You either upgraded components overtime before eventually doing a frame swap or cannibalized a bike for another build and were only missing a few things to make the old bike ridable. Don’t get me wrong, I have a huge pile of parts that have no business intermingling but the closest they’ll get to that is sitting on a shelf adjacent to one another.

How does this rat bike ride?

This bike is a great prototype dad bike. The big tires make this capable of riding on rougher city roads as well as unpaved cycle paths. The flat pedals are great when running errands or playing with the kids at the park necessitates running and jumping while not also tap dancing in cleated shoes. Flat bars give me a less aggressive riding posture and keep me out of race-mode. Something that drop bars just immediately turn on for some reason. The 2x drivetrain and wide range rear cassette gives me plenty of torque when pulling the trailer up the local hills on the way to and from childcare. It also gives me a higher top end speed when on the flats or not hauling a trailer.

What would I change?

There are probably a few things I would change though. The saddle is pretty much vinyl over plastic. Any foam that once existed has been compressed and hardened by the forces of time and “heavy” use. The handlebars could use some sweep. The super wide flat bars aren’t as comfy and are a little difficult to fit through gaps (when not towing a trailer). I ran a rear rack on the bike with some caged panniers that fit grocery bags but now that my youngest is bigger I have to move him from the front thule seat to the rear and the panniers need to move to the front. The stopping power needs to be improved dramatically. Rim brakes are not cutting it when you have close to 300 pounds to stop on any sort of downhill. Most of these problems can be sorted out with things I have around the garage, the stopping problem might require a more creative solution.

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Have you built a rat bicycle? Have you built the ultimate dad bike? Let me know in the comments