Developing the DMR Sled - Interview

At Core Bike over the weekend, the folks at DMR pulled back the curtain on a product that they've been working on for roughly two years now. The brand, which has recently been diversifying their range considerably, have now added an alloy framed, dual suspension bike to the mix. The bike was launched to the typical "looks like a…" comments, but there are a number of differences, including a concentric bottom bracket pivot. Although the bike was only recently launched to the public, we first got to see it back in August when DMR's marketing guy, Olly Wilkins, stopped through Squamish en-route to Crankworx.

The introduction of the Sled is an interesting move for a brand that, despite the introduction of the Bolt full suspension bike a number of years back, is still more well known for their steel hardtail frames and pedal designs. To find out more about the development process of the DMR Sled we spoke with the team behind the bike.

---

DMR started out with pedals, then eventually built some of the most bombproof dirt jump frames, but what brought on the desire to build an alloy full suspension bike?

We did the DMR Bolt full suspension frame several years ago, but we wanted to develop a new trail bike for a wider audience. It also suits the riding we all do the most here at DMR. You’ve got to want to ride what you’re designing I think!


What were the goals with setting out to develop this new full suspension frame?

The key goals with this frame were to make a fun, fast bike. We also wanted this, as with all our products, to be at a sensible and honest price.


How did you arrive at the chosen suspension design? Did you look at the full gamut of options out there before arriving at this?

We looked at numerous options in the early stages, the pedaling efficiency of virtual pivot designs rose to the top of the list…



The Sled has an interesting take on the virtual pivot design, with the addition of a concentric bottom bracket pivot. What were you looking to achieve from the suspension design?

Our DMR Bolt frame design is a single pivot with concentric BB (so you can build in single speed), it occurred to me the lower link of a Virtual pivot could be too. We worked on it with David Earle of Sotto design and the kinematics looked good with this configuration too. It allows a short rear end and huge bearing on the BB link.


Concentric designs have been around for a while but they’re not very prominent today. What does this element add to the design that you weren’t able to achieve with others?

It’s not so easy to do and adds cost, which are a couple of reasons. It provides a broad base to the link to make it stiff and there are kinematic benefits, anti-squat in particular.


What are the main characteristics of the frame design?

A stiff front and rear triangle with broad/stiff links to provide a solid platform for an easily tunable shock. Excellent pedalling efficiency provided by the virtual pivot design, and enough travel at 160mm.




Who developed the suspension kinematics?

David Earle of Sotto Design. We worked with David on developing the DMR AXE cranks previously; we didn’t know at the time his huge background in suspension, so it turned out we had one of the industry's experts on virtual pivot designs at hand—Nice!

He did a great job on this, we couldn’t be happier with how it's turned out, (it) rides really well and looks the part.

Here are David’s comments on the design:
• Anti-squat is rising from 70% below sag to 100% at sag and then falling off to 70% again. This gives great pedalling around the sag point and minimizes the chain-growth and pedal kickback.

• The shock rate is also really good, falling about 8% before sag for great small bump feel and then rising about 15% after sag for great playfulness and resistance to bottom out.

• Chain growth is a minimal 24mm, which is very small on a bike with that much travel. This will produce no pedal feedback.

• Anti-rise, which controls braking, is around 80–90% in the normal travel range that is used when riding, which will allow the bike to slightly sit in when under hard braking, keeping it level and stable.




What considerations were taken into account with modern shocks?

We’ve stuck with ‘legacy’ sizing 215 x 63mm—it's even got a threaded BB! We wanted the broadest choice of shocks if people wanted to change; however, the Rock Shox Monarch RT3 Debonair fitted is tuned to suit and an excellent option that’s very tuneable at a good price.

It was actually a straight forward choice for us. Metric will be something we can easily adapt to in the future. That's the beauty of ‘metal', changes are quick and easy should the industry create even more ‘standards'.


How did the process work for you guys? This is a ground up design, so it must've taken a bit of time?

It’s taken a couple of years to get done from start to finish, but it’s always an interesting journey with a design project as big as this one. It took a while to boil things down to a clear direction, but once we’d decided on the travel we wanted and the overall suspension platform design we got a basic design layout together pretty quickly with David.

The first prototypes were done in steel back in August 2015 to check out the basics. But it was clear from the outset that this bike would need to be in aluminum to meet the price and weight we were aiming for. So following the initial steel prototypes we moved onto the aluminum production design with David at the helm on that.



The first mule that Olly (Wilkins) had here in Whistler was littered with small asterisks over the frame, highlighting points that need to be worked on. Is this a normal process for DMR?

Yes, this is the normal sort of thing as there’s only so much you can do in CAD, getting a physical bike together and getting it ridden is an essential part of the process. Cable routing is one of the trickier things to get right! Along with problems we got great suspension feedback from every rider we have so far had on board. The kinematic predictions by David were echoed by Olly after two weeks of testing in Whistler.

We were also an early supporter of the ShockWiz on Kickstarter. This helped us evaluate the suspension and decide on the stock shock tune. It proved to be super helpful and very useable technology for us to have access to.


How many different iterations did the frame go through from this first alloy mule?

Apart from the initial design prototypes in steel, we did just one aluminum prototype round, then pre-production samples, then a pilot production run, before an actual production run. But from start to finish there were dozens of CAD drawing iterations and refinements, etc...

The best design gets the best performance at the best price, that’s where you need to be a bit clever... getting the best solutions with the least compromise. It was great to be working with David and his team at Sotto design to refine the design as far as possible.




Were there any unexpected elements that needed to change? What was the most surprising?

Nothing that comes to mind, to be honest. The project has flowed nicely. How time slips by is always surprising!


What was the toughest part of the process to overcome? The hardest piece of the frame to get right?

Getting it into production is always difficult, it may all look wonderful on CAD but getting it actually made in volume with high quality is a difficult process for a product like a suspension frame, there are so many elements to get right. Again having David on this project with his experience was a massive help!


Were there any elements that you had to let go of that you really wanted to include? What was it?

Getting a water bottle in the front triangle was one, and the concealed V8 motor…


DMR has a history of building long lasting products. How did this affect the development of the Sled?

Yes, it's built to last, it's early days but we’ve tried to make it as robust as possible without adding too much weight. Durability and serviceability are definitely important to us. We definitely wanted the Sled to be UK-weather-proof. If it can survive our testing grounds then it’s done well. In winter testing it hasn’t just survived, it’s thrived!

---

MENTIONS: @dmrbikes

---