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Dahn’s Pinion Gearbox Titanium Waltly 29’er

This year has seen a few ‘firsts’ for the blog, including the first folding mini-wheeler and a tandem. Just when I thought there were no more surprises due, other than what Santa was going to leave me under the tree, along comes Dahn.

You know a Rohloff hub right? OK, if not that then how about a classic Sturmey Archer three speed? Both tiny little epicyclic gearboxes built into the rear hub. Having all that weight hanging off the back of the frame isn’t great though, how about we mix things up and bring that weight closer to the middle of the frame and attach the cranks to it – sounds weird, right?

Pinion would seem to think it’s quite normal though:

They make a variety of crank based gearboxes that fit on a special mounting plate incorporated into the frame design. An internal system of shafts and gears connect the cranks and the chainring together via various different paths so you can engage a range of gears. Pinion’s gearboxes offer between 9 and 18 speeds that can cover a wide range of ratios to surpass a normal derailleur setup.

Gearboxes are completely sealed and can be used with a Gates belt drive to give a seriously weatherproof and maintenance free drivetrain. They’re frequently found on commuter bikes, tourers and other extreme adventure platforms.

All groovy in the ‘hood, we should all be using them, right? Well hold on there young fella, we’ve got a few things to think about first. Complex designs with many moving parts mean additional weight and an increase in the cost of manufacture.

It’s also been traditional to knock gearbox drives for poor efficiency compared to a standard sprocket and chain setup although this has turned out to be a little unfair. You’re going to kill a few watts whichever solution you use.

You’ll need to change the way you shift though, remembering to stop pedalling briefly as you change gear. The advantage there of course is that you can still change gear when you’re standing still, it’s also possible to dump a whole load of gears in one go if your wrist is up to twisting the shifter far enough.

The big challenge with the Pinion ‘box is that you need a frame made especially for it, although we know a few people that can help us out on that score.

Looking good – the Pinion gearbox is very compact and is complimented by the low maintenance Gates belt drive.

Dahn – tell us about how your project got started:

Everything started when I bought an electric bike, a well-built Dutch KOGA. Prior to the purchase, I read a lot about the different parts and when the purchase was made and I started using it, I discovered that I missed the research. So why not build a bike myself? An electric bike is a lot of fun and has many advantages (like riding 45 km/ph), although of course you do not get the same amount of exercise as with a traditional bike.

It’s all about the journey as they say – but an electric bike that’ll hit nearly 30mph? You Swedish guys have great laws (electric bikes are limited to half that speed in the UK!) 😉

Last year a friend of mine completed a long MTB race and it made me interested in this type of bike. I decided early on that if I were to build a bike then I would try to challenge myself and use new technology as much as I could. I had previously read about the Pinion gearbox and it fitted perfectly into my plans. So, my basic idea was an cross country MTB with a Pinion gearbox. Though, where would I find the frame?

I more or less fell across a link to Waltly and contacted them. Very quickly I received a reply from Sumi who sent a CAD drawing of a frame. Now I had a starting point and for several months I measured and counted. For me, it was also about the aesthetics; I did not just want the frame to meet my requirements for function but I also wanted it to look good.

A Pinion gearbox is mounted low in the frame, so having a narrow and thin downtube would make the frame look unbalanced, and I wanted the finished bike to be as stable as possible. I decided on an oversized downtube and longer chain stays in combination with 29 inch wheels. In order to keep the weight down, I wanted a belt drive instead of a chain. This meant that the frame needed to be divisible in the rear triangle because a belt could not be split like a chain.

Sounding good so far – how did the order go?

Sumi at Waltly was a pleasure to deal with and I was amazed at how quickly they made changes and sent a new drawing. Even with minor changes, Sumi was always very helpful and courteous and proved very patient. Finally, when pleased with the drawing I made my order and paid a down payment for the frame. After five weeks the frame was ready and Waltly sent pictures of it. I paid the remaining amount and two weeks later it arrived with DHL, nicely and well packaged. The frame looked great and all parts matched the drawing. Now, I’m not an expert on welding, but as far as I can judge the Waltly craftsmanship is excellent.

Where’s the bottom bracket gone? Oh wait, I see…

The mounting plate for the gearbox is crafted by Waltly based on the spec from Pinion, it’s got to be a worry that everything is going to fit together properly?

A big concern was that I had no opportunity to handle or look at the Pinion gearbox before the purchase. I didn’t even know where to buy one because they are normally only sold to bicycle manufacturers! I eventually received help from Davis Carver at Carver Bikes / in the United States. He generously shared his knowledge of both the Pinion gearbox and Gates Carbon Drive. I was able to order the gearbox directly from the website.

With an eye my budget I went with the recently released C1.12 model which uses a cast body to keep the cost down. This gearbox is similar to the older model but has some potentially important differences. The C1.12 has a more narrow chain stay and Q-factor. This made me unsure if it would fit my frame since, as I saw it, the risk was that the crank arms would hit the frame. However, it turned out that this was not a problem as it fits perfectly!

Risky business indeed, it sounds like Pinion are aware that if they change too much it’ll throw out manufacturers careful calculations. So everything came together OK in the end?

Yes, I also had a few pleasant surprises too. I had chosen internal routing for the brake hoses and gear cables, I discovered that Waltly had fixed tubes inside the frame to hold the cables. It was easy to thread cables through and there’s no rattling noise when you ride!

Waltly are really good about doing that, you can see the small tubes featured on the CAD drawing. So go on then, how does it ride?

This kind of bike opens up paths that I have never seen on a bike before and it is great fun. The bike feels responsive and handles exactly how I wanted it to.

The Pinion gearbox takes some time to get use to but it’s very smooth and responsive. In the future I might shift the range of gears slightly which is easily done by changing the front cog and using a different length belt if needed. The gearbox is very low maintenance, the only thing it needs is an annual oil change!

The finished bike is a bit on the heavy side though, it weighs 13.5 kg (around 29.8lbs) including pedals and a with Magura dropper post. It wouldn’t be my first choice for any kind of competitive riding, but that wasn’t my goal in the first place, I wanted a bike that could take me out on the trails and have fun.

I’m very pleased with the result, especially considering that I had to buy some of the parts without having the opportunity to examine them closer before the purchase.

Some cable wrangling might be in order there but otherwise a very neat setup.

Another satisfied Waltly customer?

I would definitely consider buying a frame from Waltly again. I have nothing to complain about regarding their service, or the quality of the finished frame.

Luckily I got the sizing of my frame correct. My top recommendation for other people would be to spend the majority of their time measuring their existing bikes and getting the key dimensions correct before placing the order. Myself, I might have also chosen a slightly longer head tube, though in this case I kept it shorter as I thought it looked better!

Top work indeed, so are ‘box bikes the way of the future?

Excellent work, I have to say I was interested to see how the blogs first gearbox bike turned out and the Pinion design is pretty out there!

It looks like Dahn nailed his frame design, especially given it was his first one. You can tell he’s sweated the details with the ovalised top tube and shaped down tube. There’s also lots of thought gone into where the cables are going to run too. Not really much to add on that front, everything looks well taken care of.

He’s also hit his goal of producing a go-anywhere trail bike that really doesn’t need much maintenance, there’s no chain to rust or sprockets to wear out.

But… Hmm, nearly 30lbs for a fairly lightweight build machine? That does seem pretty surprising, although we can work out where some of the weight is coming from by using the chart that the Bicycle Junkies kindly put together. They estimate that the Pinion gearbox is around 3.5lbs heavier than a conventional derailleur setup and around 2.8lbs heavier than a Rohloff hub.

The Pinion mounting plate and the sturdy frame may have contributed to the overall weight but even so… I think we’ve established why you tend to see gearbox bikes on commuting and exploring machines where low maintenance is the biggest driver.

Still, who knows how things will turn out in the future? Engineers love the challenge of enclosing the gears to keep them clean and tidy so maybe we’ll see a lightweight gearbox you can shift while pedalling soon!

Have you had something made in the Far East? Don’t be shy, drop me a line via the Contacts page and let’s all have a look!


Some collected useful links below to resources I browsed while doing my homework:

A review of the Pinion gearbox by some keen adventuring types:

Super nerdy test to see check how much drag is added by gearbox systems vs. a standard chain drive:

The super helpful guys at Bikeman, one of the few places you can buy a Pinion from:

The Pinion website: