Dario DiGiulio (from Pinkbike) recently asked us what our approach to bike sizing was. He polled 10 different brands including Knolly Bikes. Noel dives deep on this topic, read his full reply below. For PB's full article, click HERE.
1. How does your brand approach bike sizing in the current market?
Knolly takes an evolutionary approach to our design and engineering and as such, has arrived at our current geometry based on several previous generations of frame designs over the past two decades.
Over the past ten years, bikes have become "longer, lower and slacker" and this has made bikes from early 2010 and before feel quite dated in their designs. But I feel that we're also coming to the end of these advancements, mainly due to the proportions of the human body.
In mountain biking we have pushed seat tube angles steeper and steeper. We can do this because full suspension bikes sag when the rider sits on the bike, which effectively slackens out the seat tube angle. The bike sags even more when climbing (due to the transfer of the Center of Gravity towards the rear wheel), which further reduces the seat tube angle. Road bikes - in comparison - have had fairly consistent geometries (or the changes have been small). Only now, with the rise of gravel bikes, are we potentially starting to see some movement in geometries to a more hybrid position between road and MTB (but still closer to road). The one aspect of road bike geometry that has been pretty nailed down is that of the saddle position and hence seat tube angle. There is an ideal position to achieve the desired combination of maximum efficiency and power for each discipline and the road world has had this figured out for years. The mountain bike world started making full suspension bikes based on road geometries and now - 20 years later - has shifted to full suspension bike geometries that replicate road saddle positions, but mainly when climbing, which is where these geometries are most important.
Where we see the confusion now is in the ubiquitous "Reach" measurement. Reach is assumed to be the same for every model: any deviation from this is sacrilege! However, in reality, Reach is only one of several fitment measurements required for an ideal fit. Arguably the most important of these is Effective Top Tube length (ETT) because this determines the length of the bike and how a rider will fit on it. But even here, we have to take into account the effective seat tube angle, and the intended bar and stem that the designer suggests.
For Knolly, our trail bikes are designed to use 10mm longer stems than our Enduro / Freeride models. Hence, the ETTs on the larger travel bikes are longer. Also, the bigger bikes have steeper seat tube angles because those models sag more when climbing. This further increases the ETT on those models. So, it's not unusual to see the reach of a Knolly Enduro bike to be 15-20mm longer than the reach of a Knolly Trail bike. However, when sitting on both bikes, the fit will feel the same when you're riding.
2. Do you view your sizing chart as a hard line, or is there room for interpretation?
No,there is room for interpretation. Every customer is different, and sometimes you have to work with a customer who is a "tweener" - i.e. could go either way on a frame size. Customers also have personal preferences as well. But in general, most customers are best served by following the sizing chart. We use our staff, our team riders and our ambassadors to help check sizing. But perhaps more important is the move away from named sizes. For example"I've always been a Large" is going away and frankly an old way to think about sizing. For Knolly, size Large has always been what fits me - since I design the geometry on the bike. For sure, these bikes have become longer, seat tube angles steeper and hence reach longer as well. But regardless of model type, we try and keep the fitment the same across the model range for most customers. We also have best in class dropper post compatibility and pretty much any customer from 5'1" and taller can run a minimum 180 to 200mm dropper post, and anyone who's around 5'10" or taller can usually fit a 220-240mm dropper post. This allows us to be less concerned about seat tube length / stand over and more concerned about cockpit length for fitting customers on bikes. Hence, we worry less about "Small, Medium, Large..." and more about riding the correct length of bike for the customer. Thus ensuring that the ETT is correct so that the bike is comfortable for the rider. Then, the customer has the flexibility and versatility to fit the bike to their preference.
3. How might sizing up or down benefit certain riders?
I don't think this has changed much from the past many years, apart from the trend to "size down" or "size up" seems to flip back and forth every 3-5 years. Generally longer cockpits are more comfortable when climbing. Shorter bikes are more maneuverable and easier to manage when jumping. But you have to really decide what you want to focus on. I personally would say that you should be in the "right sized bike" for most riders. This will give the greatest overall comfort and performance. But riders will downsize for maneuverability or upsize for pedaling comfort or high speed stability. So, there is some variation for sure.
4. How do you go about establishing height recommendations for a given size?
As mentioned in the first question, we are an evolutionary design and engineering company. So, we start with what worked well in the past, then take rider feedback into account and then prototype for new models. When we release a new model, generally it's more progressive than the outgoing model and this - of course - feels great at the start. But after being on that bike for a year or two (and for me, this is often the time when the bike actually gets to market, as I've been riding prototypes for 12 months before), then we already know what we might want to tweak.
Typically over the past few models, we have tweaked our prototypes "longer". Only once during the past decade have we shortened a model between prototyping and production. We have a wide range of rider heights and sizes at our company, our extended team, and ambassador riders. Often, these riders are part of the design process as well, and we solicit feedback from them on their current bikes and when they have a chance to spend some time on a prototype new model. Universally the trend has been towards longer front ends on bikes with steeper seat tube angles. But I do think we're hitting the end of that now. There is only "so steep" you can go before you are too steep. It also seems like stem lengths have kind of standardized between 35-50mm for Enduro, FR and trail, and even a bit longer (back to 60mm) for tech XC bikes. So, given that, the ETT can only be SOOOO long before the rider is too stretched out and it becomes difficult to maneuver the front of the bike. This forms the foundation of the sizing metrics and we go up and down from these center points to develop the fitment profile for our customers.
The one thing the customer needs to do is stop looking at the "sizes"... "I'm a large - i"ve always been a large and I will always BE a large". Forget about what the "size name" is and just focus on the combined measurements, not just reach. If you take Knolly's Enduro bike (Chilcotin) and compare it to the Enduro models of some of our PNW based competitors, you'll see that once you remove the "size name" and just say" what's brand X's largest frame size, Brand Y's largest frame size and Brand Z's largest frame size", you'll see that all of us are within a few mms dimensionally of each other. Reach, ETT, seat tube angles, Chainstay length, etc... The designers of these companies didn't get together over coffees one morning and work this out between three companies. We all arrived there independently, with two decades (or more) of experience. Just compare the largest, then second largest, then third largest frame sizes and you'll find that as smaller / medium brands, we can be more progressive and take increased risks compared to the big brands.
