After profiling him a decade ago, we catch up with Owen Pemberton, founder of Forbidden Bike Co. and early proponent of size-specific geometry, to talk all things suspension design.
Almost 10 years ago to the day, we shone the spotlight on Owen Pemberton in a feature titled, “These People are Changing Everything”. The idea behind the feature was simple: showcase key personalities in the mountain bike sphere who were pushing boundaries and defying convention. The rising stars of mountain biking if you like.
In that article Owen stood shoulder to shoulder with the likes of Manon Carpenter, Sam Needham and Katy Winton. Back then, the straight talking Englishman was a frame engineer at Norco, Owen pioneering size-specific geometry while establishing a new life for himself in British Columbia, Canada.
Today Owen is the owner, founder and head engineer at the Forbidden Bike Co. He’s still based in Canada but in addition to designing high-pivot idler bikes with size specific chainstay lengths, he also has a company to run.
The recently launched Forbidden Druid V2
We caught up with Owen when he was back in the UK for the recent launch of the new Druid V2 to talk about all things bike design, suspension and get some insights into what he’s been doing for the last decade.
In the interview that follows, Owen speaks candidly about his early days at Norco and his shift in thinking with regards to suspension design. He also opens up about his fears around high-pivot idler designs being the latest industry darling, and the risk that they could suffer the same fate as Plus size tyres.
High pivots are the mainstay of Forbidden’s suspension platforms
Owen had a lot more to say on multiple topics but we didn’t have enough space to include everything we discussed here, including a deep dive into pedal back and the limitations of certain suspension configurations.
Words and interview: Alan Muldoon, mbr.
mbr: Okay, let’s get one thing straight right off the bat. Did you call your brand Forbidden Bike Co because you are making the bikes you were forbidden to design at Norco?
OP: Honestly, I don’t think I’d have even pushed for a bike like the Druid at Norco. The move was more about designing the bikes I want to make. It’s in my nature. If I can’t find the thing that I like, then why not just make it? Also, I wanted to see if I could build a brand, but no one was going to hand me, an engineer, a job as a brand manager. So I created it for myself. But to answer the question. No, it is because our HQ in Cumberland, Vancouver island, is near one of our riding spots which is called the Forbidden Plateau.
mbr: How come you launched the 130mm Druid first, especially given that high-pivot idler designs are more common on longer travel bikes?
OP: For the most part the Cumberland trail network is a lot like the riding in the UK, it’s not super steep, so that’s why the Druid was developed first. If I ride the Dreadnought on our local trails I’m bored because the bike is bored. It needs gradient and speed to come to life. We have that at Forbidden Plateau and Mt Washington, both of which are Dreadnought territory.
Bike test editor Alan Muldoon has ridden both generations of the Forbidden Druid
mbr: With the Dreadnought being the second bike to launch, how did things evolve from the Druid?
OP: Mostly in sizing. I actually designed both bikes at the same time. We launched the Druid and the plan was always to follow with the Dreadnought soon after, but I had a company to run. That gave me time to tweak the Dreadnought through, so we went half a size longer than the original Druid, and the same changes have been carried over to the V2 Druid. I do feel a little bad though, as we won’t be catering to smaller riders quite a well as before. And much as I’d love to offer seven sizes for each bike, we can’t currently do that.
mbr: How important is it to have a 100% rearward axle path, and is there a travel limit to that with a single pivot design?
OP: The Dreadnought is 100% rearward and the Druid V2 is pretty close too, but yes there is a limit, As the travel increases the pivot would need to be at the seat tube junction with the top tube to maintain that trait. If you look at previous designs of mine, like the Norco Aurum downhill bike, it was 100% rearward and as you push the pivot higher, the anti-rise starts to get too high, even for me. That said, I don’t ever want to ride a bike with low anti-rise again, because after many years riding standard 4-bar bikes with low anti-rise, I don’t want a bike that pushes all of my weight onto the front wheel on anything steep, when braking.
Owen Pemberton talks through the changes made on the second generation Druid frame
mbr: One question that comes up a lot is: If the rearward axle path has to come forward on rebound, isn’t it just smashing into bumps that much harder?
OP: When I hear that, I get what people are saying. But what they tend to miss is that the wheel moves with the impact and usually when it’s rebounding it’s not driving into the ground. Instead, it has usually left the ground. So that argument falls flat on its face.
mbr: Do you think it’s also a misconception that the suspension is less effective under braking with higher anti-rise values?
OP: It’s going to be more susceptible to packing down. So the shock is going to struggle more to recover under repeated hits, as the high anti-rise magnifies the effect. Especially if you are dragging the rear brake. So any bike with a significant amount of anti-rise will increase chassis stability by getting the rear suspension to sit down, which negates the effects of fork dive, and rewards good braking technique and punishes bad braking technique. If you’re dragging the rear brake, anti-rise is a hard thing to overcome. To me, it’s not a negative, though.
MBR’s Alan Muldoon and Owen talk tech
mbr: What, if anything, have you changed your mind about with regards to suspension design in recent years?
OP: I used to be totally of the school of thought that you need a nice straight progressive rate start to finish for consistency. But as we push bikes harder, if I used a constant rate of progression that feels good at bottom out, it would be challenging in the mid-stroke, especially on faster chunky hits, as it wouldn’t allow the bike to absorb high-speed impacts as the shock isn’t able to move fast enough. By using a variable rate design, that’s not erratic, I can get closer to the characteristics that I want at each stage of the travel and for different travel bikes. Which is why the Dreadnought is less progressive than the Druid in the mid-stroke, it’s a bike for charging hard on rougher terrain.
mbr: Shock tune is fundamental on any suspension design, but are there unique traits of a high pivot idler design that you have to accommodate?
OP: Anecdotally, I don’t have any evidence as to why that should be the case. But I do find that I can run the rebound faster and athletes have said the same thing. So if you bounce on a Forbidden bike in the car park and you think it’s right, the rebound tends to feel a little too slow on the trail. But I’m not entirely sure why.
mbr: Is it because your bikes feel more planted, so having a faster rebound helps make them feel more poppy, even if that’s true of any bike?
OP: Once you get one of our bikes set up properly, it rides like a bike with more travel than it really has. I suppose that’s quality over quantity, and I’ve never been a big fan of having more travel than is really necessary as it can make a bike really sluggish. With shorter travel bikes like the Druid the faster rebound is really important, as it helps the bike ride higher and recover faster from bigger hits. With so little travel you can’t really afford to have any packing down in the shock.
If I can’t find the thing that I like, then why not just make it? – Owen Pemberton
mbr: You’re a big proponent of proportional rear ends and building it into the front triangle was such an elegant engineering solution. Does the idler design make that harder?
OP: No. Because with an idler design, the anti-squat can be kept constant across all sizes even when moving the pivots relative to the BB to give size specific chainstays. Also with an idler, the amount of anti-squat which is generated by the chain tension is determined by the position of the idler, and that’s in the same position on all sizes relative to the suspension pivots. There is still a change in anti-squat, but it’s down to the centre of gravity height of the rider changing, not the frame design. Basically we end up with an optimised suspension package, while still allowing us to have a consistent weight bias on every size of bike.
mbr: Suspension set-up impacts weight distribution dramatically too, right?
OP: Yes, you can correct it with the suspension. And one of the things we have been playing around with is setting the suspension up to push more weight onto the front, but then the suspension isn’t performing as well. Which is why the new DH bike has interchangeable dropouts to adjust the chainstay length. But we’re actually going in the opposite direction to most, i.e. longer. So on more moderate gradients that are fast, you can lengthen the rear end and weight the front wheel more easily.
mbr: You’re moving in a different direction with the geometry on your bikes too, so what brought that about?
OP: From the geometry side of things, what I was seeing is this push where we’re getting more aggressive in the way bikes are being ridden, speeds are picking up on trail bikes too, so it’s all morphing more toward what riders have traditionally been doing on downhill bikes. Especially bigger travel trail bikes. There was a drive to gain stability on bikes, but it was all in the front end. It is almost as if brands had a wheelbase number in mind from DH, but all on the front end. Head angles have been catching up too, because when bikes first started going really long they still had steep head angles and what you ended up with was a decent wheelbase, but your hands were too far forward, and the head angle was too steep. So the bikes weren’t balanced.
The hardware that goes into the Forbidden’s high pivot design
mbr: Sounds like you’re describing the early days of Forward Geometry?
OP: Perhaps, but I just want to shoot myself when I read stuff from brands saying that the longer front end adds stability and the shorter rear end keeps manoeuvrability. I’m convinced that a lot of engineers would benefit from riding lots of different bikes, maybe even BMX. By taking a much simpler bike like a BMX you can understand what different changes can have in regards to handling. Like front to rear end weight bias, how BB height affects it. All of these things can affect how manoeuvrable a bike is, not just how long the chainstay is.
mbr: Do you think idler designs favour flat pedal riders, and specifically, having a longer chainstay, because flat pedal riders have to drop their heels more to keep their feet on the pedals, which in turn rotates their body rearward?
OP: I would say that a well designed bike favours flat pedal riders. I’m pretty short, so in the grand scheme of things, I should want short chainstays on my bikes compared to average height riders. But I’m after the same balance. I certainly don’t want a chainstay that’s longer than the reach and what you tend to get is a lot of really vocal tall people saying how bikes should be. But I’m at the other end of the scale, saying, hang on a minute.
mbr: You cut your engineering teeth designing classic 4-bar designs, so how long has the process been to get to where you are now?
OP: I’ve been designing bikes for almost 14 years. I learnt what 4-bars can do, and that’s why for an aggressive riding bike, I’d never want to ride a regular 4-bar again because I don’t want to ride a bike with such low anti-rise again. That was a real eye-opener for me. At Norco, I didn’t really ride lots of different bikes, so one of the things when starting Forbidden was to make that a goal. And while I never set out to design a high-pivot bike, I just set out to design a good bike, one of the key things I really wanted to do was have a consistent weight distribution across the size range. The engineer in me was always frustrated when I first pitched Gravity Tune at Norco, because we had all the numbers figured out, then it was decided that riders wouldn’t accept chainstays that long on the larger sizes, so we had to reduce the jumps in chainstay length to 5mm to keep them shorter. And 5mm was just chosen as a random number, it wasn’t figured out.
And I still see bands with five sizes of bike and only two or three rear end lengths. And they are quite small jumps, so it annoys me when journalists say they have size proportional chainstays, when they just have different rear end lengths. If you have five sizes and two rear end lengths there’s nothing proportional about that. Yes, I know things get dumbed down, as some of the readers won’t get the nuances, but it’s frustrating.
Forbidden has updated the swingarm design on the Druid V2
mbr: So are you going to stick to your guns and build bikes with longer chainstays?
OP: For the time being, we’re sticking to our guns. There are so many bikes out there for people that want a shorter chainstays and shitty suspension action because of chain influence, and a fully forward axle path. Those bikes already exist. I’ve ridden all of those bikes and I don’t like them so I designed a bike that I like.
The DH bike and Druid V2 are clearly not single pivots, is that a direct result of the constraints of the single pivot design driving anti-rise too high as travel increases?
Yes, and if you look at Commencal it switched from a single pivot to a six-bar…because with some suspension designs you can manipulate the anti-rise more than with others. I actually looked at doing this back when I was starting Forbidden, but I couldn’t figure out how to package it all. I knew single pivots worked, and it’s a good way to make a frame as you have two carbon frame members with very good tolerance and alignment. But I’ve been working on the updated design for the downhill bike ever since the Dreadnought was completed. I’ve always known that to get more travel, anti-rise needs to be manipulated to stop it getting too high. And with some of the things we’ve learnt with the current bikes, even just little things like stones getting caught in the frame, we wanted to move away from having overlapping frame members so the inverted 4-bar is a good solution.
I think idler designs give a lot of brands a new story to tell, but does it worry you that so many manufacturers are jumping on the bandwagon?
Yes, some brands are really afraid of missing out on any new trend. And it’s because they don’t really develop things, as they aren’t actively trying to make better bikes. They are just thinking, “we need to do that too”. I believe that’s a bad way to do business, as you’re always playing catch-up. Instead, you should be hiring the kind of people that understand the type of products you’re trying to make, understand the rider’s needs, then develop the products that meet those needs. Not every brand is guilty of following trends, but there are quite a few. And I’m worried that high-pivot designs and idler pulleys will get lumped into that trendy category? Sure and there’s always a chance that it could end up like Plus tyres, just because too many brands didn’t understand them, and didn’t take the time to do a good job, instead they were just throwing ideas at the wall to see if any would stick.