Words by Flow | Images by Flow

Owen Pemberton is the brains behind many of the new bikes which have taken Norco’s standing right to the top of the pile in recent years. The Optic is his latest project, and over the course of the bike’s development he’s spent more time grappling with geometry and the wheel size conundrum than anyone else we’ve ever met. We cornered Owen on Skype for an in-depth chat about the progression 29ers and the creation of the Optic.


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The decision to offer the Optic in two wheel sizes gives riders choice, but damn it sure made for an involved development process!

The decision to offer two wheel sizes is interesting, can you tell us a bit more about it?

What you’ll find with the Optic is that both wheel sizes have very similar ride characteristics, and so it’s quite a subtle difference between them. It’s not like some other brands were their 29er and 650b versions of the same bike are very different. Choosing between them will really come down to your own personal preference. What you’ll find is that the 29″ Optic just doesn’t have the downsides that 29ers traditionally had, because we’ve been able to get the geometry so close to the 650b, to the point that it’s basically identical between the two wheel sizes.

650b was an instant home run, anyone who tried it after riding a 26″ bike for years, it just felt like riding a bike, but it rolled over things a little better and had a few other advantages. That was the beauty of 650b.

Why did you decide to go for two wheel sizes then?

Honestly, I think if we were making that decision now, we might not have gone for two different sizes. But you need to remember we were making that call like two years ago. And at the time, there was very little appetite amongst consumers for 29ers outside of hardtails and pure XC bikes. I mean, there were some aggressive style 29ers, like the Specialized Enduro 29 and BMC had a couple of all-mountain style 29ers, but it was really only ‘in the know’ kind of riders who were picking up on them. There was definitely not the same appetite for 29er then as there was for 650b. 650b was an instant home run, anyone who tried it after riding a 26″ bike for years, it just felt like riding a bike, but it rolled over things a little better and had a few other advantages. That was the beauty of 650b.

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Whereas, the older version of 29ers didn’t feel familiar – they felt like a very different kind of bike. They go fast, they’d plough over things, but they felt different, and while in some situations they cornered better than a 26″, in others they didn’t. For bigger riders, and with a select few bikes, they were a viable option, but for most people they still weren’t.

But as I said, there were a few 29ers that were pushing things, like the Specialized Enduro. And when I looked at the rear-centre length of that bike, it was the same as what we had on our large 650b bikes, so it made sense to me that anyone who rode a large Norco 650b would probably get along well with a 29er that had that same rear-centre length.

 I spent months working on a study, staring at excel spreadsheets trying to work out geometry and how we could make it work – on paper, could we get a 29er to handle as well as our 650b bikes?

At the same time I was having conversations with a number of people about 29ers and I was consistently hearing feedback that people would ride up one size on their 29ers and slap a shorter stem on there, and that helped with the handling, overcoming the weight of the bigger wheel and tyre.

So that thinking gave us some starting points about how we could create a 29er that handled as well as our 650b bikes, because people were loving the way they rode.

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The wheelbase on both bikes is within a millimetre.

So circling back round to your question about why we did two wheel sizes, I spent months working on a study, staring at excel spreadsheets trying to work out geometry and how we could make it work – on paper, could we get a 29er to handle as well as our 650b bikes? And we figured we could, but the question was whether consumers would accept it, so we decided to do both. And now, in the last six months, we’ve seen a flood of aggressive 29er bikes. It seems like quite a few manufacturers were on the same page as us, but we didn’t know that two years ago!

I think what we’re doing with this bike is a little different to what some of our competitors are doing though. Some of our competitors are looking at a shorter travel 29er as a really aggressive bike – kind of like a short-travel Enduro bike, like the big wheels are a substitute for travel. But we’re saying it’s not, this a trail bike; yes, it will go a little faster and carry more speed with the bigger wheels, but if you land a decent sized drop, your ankles are going to tell you that you definitely don’t have 160mm of travel there.

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The Optic is not a short-travel Enduro bike – it’s a trail bike, through and through.

Tell us a bit about the prototyping process for the Optic?

We spent a lot of time and money developing a full suite of test bikes in all sizes and both wheel sizes for the Optic. Basically, everyone at Norco who rides mountain bikes as well as a lot of local riders who we use, were brought in on the process. We stipulated that riders should ride both sizes back to back, and it was interesting to see how people’s views changed. What it really showed is that there is room for both wheel sizes, especially on the smaller size bikes – I mean, I ride a small, and it was the first time I’ve been able to really ride a 29er how I like to ride, thanks to having a 425mm rear centre.

One thing I think a lot of consumers don’t understand, is that the whole tyre/chain-ring/chain-stay envelope is the most frustrating area of bike design. Everything is so tight in there.

425mm?! That must be the shortest out there!

I think there are a couple of manufacturers in that ballpark, but we’ve been able to get that length and also be front derailleur compatible, which we’re very proud of. Whether or not you feel that front derailleurs are still relevant, there are plenty of places in the world that still want them, so it’s good to be able to offer that option. In every size were we offer both a 29er and 650b, the rear centre length is exactly the same on both wheel sizes.

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You’ll find short stays on both wheel sizes – 425mm on the size small. Like other Norco bikes, they employ Gravity Tune, so the rear-centre is longer on the larger frames.

Is that something that was made possible by Boost rear ends?

Boost was definitely a huge part of that. One thing I think a lot of consumers don’t understand, is that the whole tyre/chain-ring/chain-stay envelope is the most frustrating area of bike design. Everything is so tight in there. When there were first rumblings about Boost a few years ago, it was like ‘really, is this necessary?’ Because a lot of the talk then was about wheel strength and stiffness, and we just didn’t see people pushing the wheels so hard that they needed an extra few percent stiffness. But the real benefit of Boost was that it got an extra 3mm of chain line in that area, and 3mm to us was like “done! Sold!” It just allows us to get better geometry. And for us as a company, geometry is what drive our designs – we’re always looking to get the optimal geometry for any bike, and Boost has a allowed us to do that on all sizes.

Steepening the head angle may have given you a similar steering feel, but the handling is very different, you’re not going to ride the bike the same.

One of the interesting things with the Optic is the use of a consistent stem length across all sizes. Can you elaborate on why?

One of the things I was hearing from people who were quite heavily invested in 29ers three or four years ago, was that running a shorter stem means the handling matches more closely to what you’re used to with a smaller wheel. So we did some research to see exactly how this worked in the real world. And what we found was that in the past quite a lot of 29ers had dramatically steeper head angles, and this was in order to reduce the trail (ed. Now were moving into territory that might not be familiar for many people – for a good explanation on what trail is, have a look here) and give it a quicker handling feel in spite of the bigger, heavier wheel. The only problem with changing the head angle like that is, well, you’ve got a dramatically different head angle! And that has an impact on how the fork is pointing at objects when you’re descending down steep stuff and so that really changes how you will ride the bike. So steepening the head angle may have given you a similar steering feel, but the handling is very different, you’re not going to ride the bike the same.

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A tiny 50mm stem on the 29er, whereas the 27.5 has a 60mm, across all sizes. Finding the right balance between stem length, head angle and fork offset was a real challenge to keep the steering feel consistent between both bikes.

But what we discovered, is that the sweet spot in terms of delivering the same handling across 650 and 29er, is that the 29er can be half a degree steeper and with a 10mm shorter stem. The steeper head angle reduces the trail slightly, and the shorter stem gives you more leverage over that wheel, so you can get the same steering feel without having to dramatically steepen the head angle.

Of course, there are some slight differences due to tyre contact patch and the like, but the end result is that when you start to get playful on the bike and really engage with the terrain, the Opitc 29 doesn’t feel like your old 29er, it feels like one of our 650b bikes.

Another element that has a big impact on handling is wheelbase, and what we’ve been able to do with the bikes is not only get the exact same rear-centre measurements across both wheel sizes in any given frame size, but we’ve been able to get the front-centre within a millimetre or two as well. And that means your weight balance between the two contact patches of the tyres is the same too.

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Now bringing it back to the stem lengths, which was your original question, it’s the final piece of the sizing puzzle. When you look at the bikes on paper, the reach measurement (ed. horizontal distance from bottom bracket to the centre of the top of the head tube) of 650 and 29er is slightly different, but when you incorporate the stem length we’ve proscribed into the equation (60mm on the 650b bike, 50mm on the 29er) then the reach between the two wheel sizes is identical. From your feet to your bars, and your saddle to your bars is the same.

When I first came to this job, one of the conversations I had was that I felt that in any given model, every frame size should have the same stem length and that should be whatever handled best.

So essentially, the 650b and a 29er fit exactly the same, and they handle as damn near as we feel is possible the same too.

A little while ago I read an interview with you where you talked about the idea of 120mm-travel trail bike with a 65-degree head angle, and I must admit I thought that’s what the Optic might have ended up being. 

Well it is an interesting concept, and I do think that’s a viable geometry. But we also still need to sell bikes, and what I’ve learned is that the mountain bike consumer is generally a pretty conservative kind of buyer.

When I first came to this job, one of the conversations I had was that I felt that in any given model, every frame size should have the same stem length and that should be whatever handled best. I come from a downhill background, and I’ve always put whatever stem length on my bike gave the best handling. Whereas it seems that there’s a very pervasive road bike style of thought around this issue in much of the industry, where it’s all about using the stem length as an instrument of fit, as opposed to handling.

But that just doesn’t make sense – you don’t steer a road bike, you lean it, whereas a mountain bike involves a lot more input at the bars. They’re a completely different bike, and so you need to have a completely different understanding of how the stem length is looked at. And it’s crazy to think that mountain bikes are still evolving away from this!

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A road bike and a mountain bike sure aren’t turned the same way, so why should we have the same approach to stem length, reasons Owen Pemberton.

I mean, a lot of mountain bikers still look at top tube lengths, not reach, which is really only relevant to when you’re sitting down as opposed to standing up, which is where most of your riding is done on a mountain bike. What I’m trying to work towards is a completely different understanding of bike design than that you’d find on the road.

You don’t steer a road bike, you lean it, whereas a mountain bike involves a lot more input at the bars. They’re a completely different bike, and so you need to have a completely different understanding of how the stem length is looked at. And it’s crazy to think that mountain bikes are still evolving away from this!

Anyhow, we are moving away from that traditional approach. And what I was getting at in that interview, is the notion that perhaps one day we could end up with, say, an Optic and Sight and a Range, all of which have the same geometry and fit exactly the same, but with different amounts of travel. For a rider like me, that be perfect, I like to ride down the steep stuff and go fast, but I don’t need all the travel as I don’t hit the big drops or big jumps.

Now that is a really interesting concept! The same geometry, the same fit, different travel. Tell us about the suspension on the Optic. We notice both bikes have slightly more travel up front.

Yes, that really comes from looking at what we do – if we’re building up a bike, we tend to go slightly more travel up front. On trail, it just feels better, it balances out when you’ve got a lot of weight on the front wheel.

We did some cool custom work with FOX on the 29er fork too. Normally FOX would spec a 120mm 29er fork with a firmer, cross-country tune, but we’ve had our forks on the Optic 29er given more of a Trail tune, so a softer compression tune, which helps ensure that both the 29er and 650b bike have very similar suspension feels too.

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The 29er and 27.5″ both have the same fork tune, which was a custom request – normally the 120mm fork would have a firmer XC tune.

What about the rear suspension rate?

In terms of the rear end, it’s designed to be very progressive. We’ve equipped it with a smaller volume air can, and that’s to ensure it’s nice and progressive – it’s only quite short travel, but it’s capable of being ridden very hard, so we wanted to ensure the rear end wasn’t going to be bottoming out constantly. Trust me, if you ride it like it can be ridden, you’ll get full travel. Probably one of the most consistent comments I hear is “it feels like it has more travel than it actually does, but I’m still not bottoming it out”, which is exactly what we wanted.

On the shorter travel bikes, they’re already less inclined to have suspension bob, but you’re also pedalling a lot of the time, and over all kinds of surfaces, so having less anti-squat allows the suspension to work its best with minimal impact of chain tension on the suspension.

Compared to a Sight for instance, the suspension is more progressive, and it also has less anti-squat. That’s something that some people haven’t quite understood our thinking around, why we have less anti-squat. But let’s look at the extremes, for example the 160mm-travel Range and a 100mm-travel Revolver.

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The rear end is super progressive, so even though travel is limited you don’t blow through and bottom out with hard riding.

With the Range, we have a lot of anti-squat built into the suspension, and that’s because that bike is primarily climbed up fireroads, then rallied down really rough, steeper descents where you’re not pedalling much. So you can have a lot of anti-squat to keep that large amount of travel stable, while you pedal on a smooth surface where there’s not so much pedal kick back.

Whereas on the shorter travel bikes, they’re already less inclined to have suspension bob, but you’re also pedalling a lot of the time, and over all kinds of surfaces, so having less anti-squat allows the suspension to work its best with minimal impact of chain tension on the suspension.

What we found works better, is actually the opposite of what most people think – most people assume a cross-country bike should have more anti-squat than an Enduro bike, but in practice it works better the other way around.


 

For more on the Optic, take a look at our news piece, and hold tight for a full review soon!

 

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