Fork length effect on hardtail geometry

Drag the slider to see effects on hardtail geometry of different length forks. All angles are based on appropriately sagged forks: eg 100mm travel fork sagged 25mm. We consider this a more useful guide than static geometry when considering hardtail geometry.

Note that using the same travel fork gives the same geometry across all our hardtails, but that each frame has a different max length fork it can take.

Figures are a guide only, and will vary slightly depending on fork make, model and setup.


The development of the Hemlock frame

Mountain bikes get hemmed in to their little slots in the market a great deal these days. It probably makes for an easy sell when you claim a bike is focused on only one thing. However, Cotic has never been about the sell, it's about the ride, and that's exactly where the Hemlock came from. Against a backdrop of using our Souls and Sodas for pretty much everything from racing to big mountain terrain, we didn't want a suspension bike that was 'XC' or 'AM' or 'FR' or whatever set of initials is new this week, we wanted something we could ride most things on and have loads of fun doing it. We wanted a Mountain Bike in the truest sense - take our do anything hardtail philosophy and develop it. So the frame had to be light, but not so light it broke at the first drop or flexed like a long bow, and it had to be strong enough to take on big terrain and new generation big forks without needing 'drop it off a building' reinforcement. Finally, it had to be adaptable. People have different preferences and different local terrain, so they need options to make the best of that. It's not about compromise - that implies lowering performance - it's about choice. Travel isn't the performance differentiator most people believe it is. Sure it makes a difference, and probably for the last few ounces of ultimate speed more is better, but how many people just want to go fast and that's all? What about other factors?

The hardtail hardcore amongst us wanted something short travel and snappy, with plenty of trail feedback so we could tell what was happening, and didn't have to relearn our hardtail riding techniques everytime we switched bikes. The big mileage guys who ride day in, day out to earn their crust in the mountains wanted long travel to look after them all season long, and give them the performance they wanted when the rocks got really big. Some guys wanted long forks, some wanted shorter forks, and so it goes on. The key thing is that there was no 'wrong' setup, just a bike capable of being configured to work really well for the way a particular rider likes it.


ROADHOG Forks Have Their Disc Mount on the Right :  What's That All About?

ROADHOG forks ROADHOG forks ROADHOG forks

Our ROADHOG forks caused a bit of a stir when they were released to compliment our ROADRAT frame. Why? Well, as you can see from the photo, the disc mount is positioned on the front right of the fork rather than the more usual left rear. As always with Cotic products, there were firm engineering reasons for placing it where it is, and here's the lowdown:

Forces
Axle movement under disc braking is now a fairly well known phenomenon in mountain biking. Basically with the caliper positioned left rear (usual place), and a vertical dropout, there is a reaction of the braking force which tends to push the axle out of the dropout, hence you're relying on the friction of your QR to counteract this rather than a completely mechanical stop. Most manufacturers have moved to a slightly forward facing dropout to counteract this.

We've actually never experienced any trouble with this on our mountain bikes, but during prototype testing of the ROADHOG fork - which had the disc mount in the usual left rear position - we did actually experience some axle movement. Nothing actually came undone, but after some serious downhill braking on fast roads, the rotors would be rubbing a touch and the wheel would 'clunk' home in the dropout when we undid the axle nuts. This was clearly unacceptable, so we set about finding a solution. Our first port of call was forward facing dropouts, but these would have required custom cut version which would have increased the fork cost disproportionately. Therefore the design problem became how to contain the disc forces whilst using an off the shelf vertical dropout. The solution, as you can see, was to place the disc mounting on the front. This puts all the forces into the dropout, and is still a completely normal International Standard setup, so it takes any IS caliper. It also gets the brake away from the back of the fork which brings us to....

Mudguards
With the ROADRAT's do-it-all brief, it was clearly important to provide mudguard mountings. However, trying to figure out if it was possible to mount a mudguard regardless of the type of disc brake used when the disc mount was on the back of the fork was turning into a quest, and a futile one at that. The beauty of the front right disc mounting was that it killed two birds with one stone: The disc forces were contained, and no matter what brake system you used, you'd always be able to get a mudguard stay fitted.

Conclusion
The front right disc mount position solved a number of problems we were faced with during the design phase: Which gives you a fantastically versatile fork with no drawbacks.

BFe Geometry Explained

We've noticed a few comments around the web questioning why we've kept the relatively long top tube lengths from the Soul and read them across to the BFe, when a lot of other companies' frames of a similar ilk are shorter. I gave a bit of an explanation on the STW forum, and thought I'd elaborate a bit further on the thought processes behind the new frame.

Early on in the BFe development I did think about shortening the frame, but the feedback I got from test riders was that they were using stems 20-30mm shorter than they would normally use on their Soul/Soda's for XC stuff. This was partly due to the slacker angles resulting from longer forks (the shorter stems helped keep the handling sharp), and partly because the BFe is for mucking about on so a shorter position pushing the rider back on the bike was desirable. As well as this, a couple of the guys rode a size down from what they would usually ride, which is effectively shortening the position as well. The other thing to remember is that the frame was developed partly in response to the need of the AQR guys out in Luchon in the Pyrannees, where the lifts don't run all the time very early and late in the season. They wanted something tougher than the Soul, but they also wanted a bike which was easier to pedal up mountains than their full suspension bikes when the lifts were shut. As a result, the BFe still needed to balance the requirement for having a bit of room to breathe.

After receiving the feedback and talking it over, in the end I decided to stick with the 'standard' Cotic lengths as people seemed to be shortening the position using component setup. The other advantage of this is that is gives the frames a lot of setup flexibility, as switching to a slightly longer stem and winding the forks down a touch turns it into a very usable trail bike. The lack of seat tube bottle bosses also allows a long seatpost to be dropped right down, which helps with this. Of course the facility to use a really long seatpost that drops properly gives you the option to go for a size smaller frame if you really like you bike compact.

In the final analysis, a shorter position is easy to achieve with a shorter stem or by pushing the saddle forward in the rails (good for weight distribution with long forks), and the length of the bike gives the same fantastic weight distribution and handling our other frames have become well known for. After all, if I'd wanted a bike like all the others I wouldn't have started Cotic in the first place!


Why and how we use Reynolds 853 in the Soul frame

853
Steel's steel, right? Wrong! All steel is not created equal. At Cotic, we use 853 for the Soul frame because it's one of the best engineering materials on the planet. Standard cromoly steel, in standard (non heat-treated) condition is between 34% and 38% less strong than Reynolds 853. Think about that for a second. That's a lot of strength. And it doesn't just end there. The increased grain alignment and post welding chemistry of the tube means that it air hardens. Simply put, it gets stronger after it's welded. It's a very neat trick, and one that cromoly simply doesn't do. You weld cromoly, it gets weaker in the heat affected zone around the weld.

Premium
Obviously all this trickery comes at a price. You don't get something for nothing. But, next time you hear someone talking about how the Soul is so much more expensive than other steel frames, think about this: Reynolds 853 costs nearly 5 times more than the equivalent Reynolds cromoly. We think it's worth it because it gives the frame such fantastic performance, and that it makes the Soul fantastic value.

Performance
With 853 being so much stronger than regular steel, you may wonder why the Soul isn't that much lighter than other steel XC frames. Stronger material means you can use less of it, right? Well yes, but that wasn't the design brief for the Soul. Strength and accuracy were at the top of the list of priorities. A very light steel frame is noodly and flexes along it's length. Not what you want when you're hauling through that rock field, or zig-zagging between the trees on your favourite singletrack. So, the Soul uses oversize sections in similar wall thickness to any other steel XC frame. What does that get you? Huge strength and longevity for a similar weight to other frames out there. But lets put that into context for a moment. To get the same strength, stiffness and fatigue resistance as the Soul out of a frame made from regular cromoly, it would be nearly 0.5lb heavier than the Soul due to thicker tube walls. It would also need down tube and top tube gussets at the very least to reinforce the structure at the weak points. That's a lot of extra weight to haul around to get the strength we wanted.

Stays - Updated
So after all the slagging we've just given cromoly, you're probably wondering why the rear end of the Soul is made out of the stuff instead of 853 now that 853 stays have become available (late 2005). Well, any structural problem is simply a matter of working to the limits of the material, and the rear end of the Soul is as strong and responsive as it can be through careful design and tube specification, backed up by more than 4 years of riding through prototyping and into production. Reynolds are only offering their 853 stays in the same profiles and wall thickness as our cromoly stays so they wouldn't any lighter, just an awful lot stronger (when our cromoly rear end is perfectly strong enough) and an awful lot more expensive. For the moment, we'll stick with what we've got.