The Numbers Game

I’ve never been any good with figures, but increasingly my conversations about mountain biking feel like I’m reading a barometric pressure chart – my poor brain sometimes struggles to attribute meaning to numbers being flung my way. And every year the mountain bike numerical soup gets thicker, swimming with new component or frame standards that sound like an international dialling code.

"You know what moments like this really need, mate?" "No, what?" "A discussion about wheel sizes."
“You know what moments like this really need, mate?” “No, what?” “A discussion about wheel sizes.” “Dickhead…”

The thirst for evolution and incremental improvements is the driver, and don’t get me wrong, I love the way bikes are always progressing. I just wish there weren’t so many numbers that went along with it!

Go back fifteen or so years and it wasn’t so. The only numbers thrown about were frame size and travel – you certainly didn’t need to specify wheel size because wheels had one size. Now you can’t talk about wheels without sounding like you’re rattling off the dimensions of package you’re shipping.

Definitely not thinking about bottom bracket measurements.
Definitely not thinking about bottom bracket measurements.

The times-table of axle sizes and hub widths was much simpler too: 90% of mountain bikes had the same axle and hub widths, with downhill bikes the only exception. Admittedly most riders’ wheels were being held in by ridiculous little chopsticks, never may they return, but that’s not the point. Now we’ve Boosted the issue to include 100×12, 100×15, 110×15, 142×12, 148×12 and 157×12 too, plus good old 110×20, 150×12, 100×9 and 135×10. The answer is 15,964 by the way.

29,1x11,157x12,110x15
29,1×11,157×12,110×15

A handlebar was just a handlebar. It had the diameter of a handlebar and was about one handlebar wide. Yet now we agonise over just how much to trim (or not) off our 808mm bars and debate the merits of 31.8 and 35mm clamps.

Dare we get started on bottom brackets? Once 68mm or 73mm (both threaded), the bottom bracket options now read like the Australian Standards sticker inside your helmet: 68mm, 73mm, BB92, BB98, BB30, PF30, BB386 and about a dozen other variants on the theme too. Or drivetrains? 3×9 has become 1×10, 1×11, 1×12, 2×10, 2×11 and 3×10…phew.

Not concerned about hub widths.
Not concerned about hub widths.

While I’m not sure if my improved numeracy can be called an upside, in some ways the onslaught of number has made actually getting out on the bike even more of an escape. Once you’re on the trail, you can forget about the fact your bike’s running 27.5, 2×11, 148×12 with BB92, you’re just riding, and hopefully that never changes!

The important numbers: how far and how long you rode this week.
The important numbers: how far and how long you rode this week.

Wheel Talk, with Wheelworks

We got Wheelworks founder Tristan Thomas on the line to answer a few questions about why all wheels are not created equal, and to dispel a few myths around the oft-called ‘dark art’ of wheel building.


Wheelworks Flite Wheel Build
Three Wheelwork’ers, Gavin, Tristan and Jesse, from Wellington.

We’re going to be testing the Flite Wide Carbon wheels, which boast a 34mm internal width. From our perspective, we feel that rim width can really transform a bike in so many positive ways. Given the performance benefits, why do you think it took so long for wide rims to come about?

Wheelworks Flite Wheel Build
How every good wheel build begins.

We’ve been building and riding wide rims for about 5 years now and it’s great to see them become popular and mainstream.  From our point of view there aren’t many downsides to rims with an internal width of 30 to 40mm, and as you know there are a whole lot of positives.

After the move from 26” to 29” and then 27.5” that most companies felt they’d already overloaded their customers and their supply chain with wheel changes

I think the delay with seeing these rim widths becoming adopted by the industry is that after the move from 26” to 29” and then 27.5” that most companies felt they’d already overloaded their customers and their supply chain with wheel changes and that the move to wide rim wasn’t a priority for them.

I don’t think we’ll see much change in rim widths over the next few years.  I think that rims will go as wide as 40mm for 2.8-ish tyres but for everything from XC oriented 2.2” to enduro oriented 2.5” will use rims in the 30-40mm range.  We’ve been running everthing from 33mm cyclocross tyres on 30mm rims and there really is zero downside to wider rims.

Wheelworks Flite Wheel Build
Just like with alloy rims, there’s a huge range of quality in carbon rims too.

Our test wheels are carbon. What are the most common misunderstandings, myths or mis-truths about carbon rims?

My big frustration is that all carbon rims, whether they’re good or bad, get lumped into this same category of “carbon rims” and talked about like they’re the same and this isn’t fair or accurate.  There are plenty of good quality aluminium rims which are much better in every measurable way than a cheap carbon rim.

There are plenty of good quality aluminium rims which are much better in every measurable way than a cheap carbon rim.

Modern, high-quality, carbon rims like our Flites are the lightest, stiffest, and most durable rims available.  The only downside is that they’re more expensive than aluminium.

 

You also offer an alloy Flite wheel set. Can you have an alloy-rimmed wheel that’s as strong as a carbon-rimmed wheel? Are there any inherent limitations or advantages to an alloy rim?

Alloy wheels are far from dead and there is heaps of product development still going into them.  Modern wide alloy rims are a big improvement on the narrow, flexy things of yesteryear.  In general an alloy wheelset will be heavier and less stiff, but will be cheaper.  Alloy rims tend to dent when they’re whacked…this can be a good thing and is why you see EWS racers using alloy, whereas good carbon will take a pretty serious beating with no damage at all but whack them hard enough and they will crack.  In general alloy rims should be treated as a consumable item for an aggressive rider…they’ll dent and eventually have a hard time holding an airtight tubeless bead.  Good carbon rims don’t suffer from these dents and will outlast alloy.

Wheelworks Flite Wheel Build
Strength, stiffness and durability are all very different attributes, even though they often get lumped together.

Where does a wheel actually derive its strength from? How much is a product of the rim versus the build quality etc?

Stiffness, strength, durability are three terms which get used and I think it’s worth clearing these up as they’re very different but often get confused.

Once a wheel has ‘enough’ stiffness the rider won’t notice twice as much stiffness.

Lateral stiffness is how much the wheels flex when loaded sideways during cornering, landing crooked (come on, admit it!) knocking off rocks or riding off-camber roots.  A stiffer wheel provides a more direct, confidence-inspiring ride.  A wheel which isn’t stiff enough is vague or mushy to ride.  Once a wheel has ‘enough’ stiffness the rider won’t notice twice as much stiffness.  I think of it like having a waterproof roof on your house:  if it’s not waterproof enough then it will drip in the rain but once waterproofed it doesn’t matter if you double or quadruple that waterproofness as you’re still going to remain dry.  How much lateral stiffness is ‘enough’ depends on the ride weight and style, and on their bike.  Also worth noting is that a super stiff wheel won’t be noticed when clamped into a super-flexy fork with a flexy stem and flexy handlebar.

Wheelworks Flite Wheel Build
Getting the spoke lengths exactly right helps prevent any weak spots or stress concentrations for better durability.

A big myth here is that high spoke tension builds stiffer wheels

Lateral stiffness is built into a wheel mainly by the rim’s shape and material but the spoke type, number of spokes, lacing pattern and hub flange dimensions also play a role.  A big false myth here is that high spoke tension builds stiffer wheels:  There is no scientific reason for this to be true as the spoke’s Modulus of Elasticity isn’t affected by tension and our lateral stiffness testing confirms it isn’t true.  Lowering spoke tension won’t change how the wheel feels unless you lower the tension so far that the wheel falls apart.  Conversely increasing spoke tension won’t make the wheels feel any stiffer or more responsive but the higher tension will place more stress onto the rim, hub, and spokes and will cause these items to fail sooner.

Wheelworks Flite Wheel Build
Higher spoke tensions don’t necessarily equate to a stiffer wheel, despite popular myth to the contrary.

Vertical stiffness is another myth.  Wheels don’t flex vertically in any amount which could be significant.  Your tyres have around 60mm of vertical flex so adding, say, 1mm of rim flex just won’t do anything.

Strength is how a wheel will respond to one, single, hard impact:  A cased jump, a hard strike onto a root, etc.  Strength mainly comes from the rim’s design and a good, strong rim poorly laced to a cheap hub will still be strong.

Durability is how well a wheel responds to prolonged riding and continued impacts.  A  wheel’s durability is much harder to measure and building durable wheels is not easy.  This is where some of the ‘black art’ of wheelbuilding comes in and although no single silver-bullet will give you excellent wheel durability – there are plenty of small steps, custom tools, and minor tweaks that can be done during the wheelbuild process to increase durability.  We’ve been doing this for over 10 years and wheel durability is a huge area of focus for me and the reason we’re able to offer lifetime guarantees on wheels.

Wheelworks Flite Wheel Build
‘Grimlock’ is Wheelworks’ custom press that subjects wheels to forces far beyond what a rider is capable of.

We notice you offer a lifetime broken spoke warranty. How can you do this?

Because we’ve figured out how to ensure they don’t break! As part of every wheelbuild we measure the rim and hub and calculate the spoke length.  We then cut spokes to the exact right length, down to 0.1mm accuracy, specific to that wheel to ensure we’ve got full thread engagement in the nipple.  If the spokes are too short they’ll break the nipple, if they’re too long they’ll break at the first thread.  When they’re the perfect length and combined with our other steps, we can guarantee they’ll never break.

There are two types of warranty:  one where the manufacturer expects the product to fail and be replaced, and one where the manufacturer puts steps in place to nearly eliminate possibility of failure.  We offer the second type of warranty and I’m extremely proud of the durability of our wheels.

You’ve mentioned to your ‘grimlock’ machine, which pre-stresses the wheel. Can you explain how it works and the importance of this process?

If you’ve ever ridden a brand-new bike you’ve likely heard a popping sound coming from the spokes as they settle in, unwind themselves, bend themselves slightly, and loosen off.  With some hand-built wheels you’ll hear that they need to go back to the builder after they’ve ‘settled in’ to be re-tensioned and re-trued.

Wheelworks Flite Wheel Build
After Grimlock, the wheels go backing into the truing stand.

Grimlock allows us to apply a vicious amount of force into the wheel in a really controlled way, and basically over-load the wheel well beyond what will happen when you ride it.  The first time a wheel goes into Grimlock it loses about half its spoke tension so we need to re-tension and re-true the wheel.  We alternate this process of re-tension and re-truing, and putting the wheel through Grimlock until the wheel comes out of Grimlock as true as when it went in.  At that point the wheel has been stressed well beyond what a rider can do and we’ve got full faith that barring a huge crash the wheel will never go out of true.

Do spoking patterns really have an impact in the world of mountain biking? How do you lace mountain bike wheels and why?

There are a few little things that lacing patterns impact but nothing too significant.  We lace most carbon rims with a 2-cross pattern which reduces the angle that the spoke enters the rim and helps with rim durability a little.  We lace the rear wheels so that the ‘pulling’ spokes bring the crossing in towards the centerline under power to give a bit more derailleur clearance, but with modern 142 and 148mm dropouts being so stiff and modern 40-plus tooth cassettes this doesn’t have a significant effect for most people.

Wheelworks Flite Wheel Build
Checking the dish.

What is the next frontier for wheel development?

The area between Plus and non-Plus is pretty blurred at the moment and you’ll see that continue, but the industry will settle on 30-40mm rims for non-Plus bikes, 40-50mm for Plus sizes and those horrible 23mm rims will be a relic of the past like V-brakes.

Carbon rims will continue to drop in price and will be spec’d on lower-priced bikes but the high-end stuff will remain at a similar price.

Wheelworks Flite Wheel Build
Short black? How did you know?

If you look at the holistic development of the bike I think that wheels are in front of the curve.  I think we’re unlikely to see really significant changes to wheels in the next few years but there will be lots of development in tyres to make the most of wider rims.

Wheelworks Flite Wheel Build

Bikes which can accept both super-wide 27.5” tyres and 29” tyres will be increasingly common.  What we’re seeing riders owning this type of bike can drastically change how the bike rides by carefully selecting two wheel and tyre combinations so they no longer have a need for an XC bike and a Trail bike and just swap wheels instead.

At the moment we’ve got a mess of axle ‘standards’ which are confusing for riders and make life harder for everyone in the industry from frame companies to dealers so we’ll see the industry settle on a single standard which works.

Thanks for taking the time to chat, Tristan! We’re looking forward to putting your wheels to work! 

Interview: Chris Pomering, Engineering Manager, Trek Bikes

Chris Pomering, Engineering Manager with Trek Bicycles chats candidly about the good, bad and ugly of mountain bike wheel size developments.

 

The arrival of 650B feels like a push from the industry, rather than a consumer demand driven change. Do you agree?

I agree. There’s a great visual that really illustrates this for me that talks about the Formula One evolution, and how the cars have changed from the 1950s to today. It shows how wheel size, and cockpit size and air-foil dimensions have all evolved and adapted, and bikes are the same. As technology evolves, things change. Wheel size is one of those things.

How do you feel about certain brands pushing 650B as the answer for cross country use when 29 has been promoted as the fastest, best size for this style of riding for the past few years and has become so established in this arena?

My feeling towards that? That’s a good question. All our research, all our pro riders, all our experience tells us that 29 is truly the right wheel size for that style of riding if you’re truly looking for the fastest wheel size. I don’t know, everybody has their own arguments, but everything we have seen points to 29 for that application.

And do you think that holds true for all rider sizes? In particular, really short riders.

I think in the extremes, you may have to consider smaller wheels for smaller riders, but that’s definitely the exception to the rule. I don’t generally think it’s a fit story, so much as a rider preference story – how do you want the bike to ride, to handle underneath you. Generally you can overcome all of those issues and get smaller people into the right position for their preferred riding style on a 29er.

When it comes to the difference between 26” and 650B, it is really hard to discern the difference on the trail. If you blindfolded me, I’d struggle to tell them apart. Would you say the differences are as much theoretical as anything else?

From the engineer in me, I’d agree. I mean, it is very close to a 26 in measurement terms. And for 95% of the people out there it is such a fine tuning change that they won’t pick it up.

I guess that then begs the question, is it necessary? The benefit of a slightly bigger wheel is there, but it’s such a small difference, is it worth the overhaul of so many parts of the industry? 

Personally, I think there are a lot of other technology advancements people could be working on instead of trying to run down this wheel size thing. I mean electronics, suspension technology… there are lots of areas in my mind that I think would better serve mountain biking than all the noise around wheel size.

Chris Pomering Trek World

Given that, if you had unlimited resources, what would you spend your time and money on developing?

I guess it depends on your philosophy on innovation. Are you taking a more incremental approach, or are you swinging for the fences, more of a blue ocean approach. For me, I’d look at everything; materials, electronics, new materials – I’d go in every direction if I could.

When you design a bike, what weight is durability given in the mix?

We’re in a really tough spot when it comes to developing new frames, because our durability requirements continue to grow. Compared to five years ago, we’re testing twice as many aspects and often for twice the duration than in the past. And at the same time, we’re of course making them lighter every year, so it’s not an easy job – but that’s why we don’t have monkeys doing it I guess. Durability is definitely a huge factor.

It’s an interesting move with the Remedy to have the same bike, with the same travel, available in two different wheel sizes. I understand the argument for rider preference, but for many consumers it could be be quite confusing. 

Yes, it could be. I mean there’s the engineering answer and there’s the reality. Everybody can research on the internet and find their own perception of what they think suits them, and there’s a lot to be said for giving people a chance to decide what they thinks suits them. Different people preference different things; take a look at the road world – some people think aero is most important, others weight, other stiffness. There’s a lot to be said for catering to the preferences of those riding the bikes.

We’re starting to finally see the arrival of bikes designed specifically around 1×11 drivetrains. Talk to us about 1×11 and the potential here to free up frame design.

There is a lot of potential here. That interaction between the front derailler, the tyre, the frame… there’s a lot going on there at the point and we constantly beat our head against a wall trying to get around that and optimise it, so there is room for huge improvements here. I just converted my kid’s bike to a 1x drivetrain, and I’m just waiting for the parts to do mine too.

Is there an aspect of Trek that you feel the company should be most proud of?

On some ways I love how diverse we are, and it’s often only when I come to events like this that even I can appreciate some of the cool stuff going on that I mightn’t get to deal with in my role. There are so many areas we cover as a brand, we can have the saddle engineer in a room with a wheel engineer, or a mountain bike engineer. So there’s a lot of opportunity for great collaboration – you can really pool expertise. On the mountain bike side of things, I’m really excited about the race shop products, things like the Ticket and Ticket S. I think they’ll be great for the brand, we’ve always had more of a conservative image as a brand and I think these will be bikes that people will really aspire to ride.