4 different approaches
The fork is one of the most important factors of the overall bike compliance. A stiff fork will make bike harsh and very hard to live with on a gravel road. On the other hand, the more flex in the fork the less precise and confidence-inspiring steering. So making a good fork that combines stiffness with compliance is not an easy thing to do. But, as my test shows, it can be done!
My benchmark bike has a carbon Jamis ECO fork. Eco stands for Enhanced Compliance Offset and means that fork blades move forward to provide extra vertical compliance for a more comfortable ride. The same effect you can achieve with GT Grade Flip Chip fork that allows you to move the axle more backward in relation to the fork blades. And my test showed that this really increases the fork compliance without any negative effect on steering precision. But there is another way to achieve that. Just look at the fork of an Argon 18 Dark Matter gravel bike. Instead of bringing the axle closer to the rider Argon 18 decided to bend the fork in a way that axle is put in the more forward position allowing for more flex in the fork blades without losing the overall stiffness.
The other solution for improved fork compliance is incorporated in Lauf Grit fork. It has 3 very thin springs that allow the wheel movement up and down without losing too much of the handling precision. And this is true but you have to remember that this is a very tall fork that will affect your overall bike handling (it will probably make the steering much slower). Fortunately, there are also forks like U-turn GravelPLus from a very renowned OPEN company. It promises a lot of flex without any visually visible gimmicks. And all of this is accomplished with very low fork weight and very high stiffness. It sounds like a holy grail of gravel forks, but is it really?
Fortunately, I had all four forks at my disposal so naturally, I wanted to find out which will be the best one in terms of compliance. To make the test as much objective as possible I used my benchmark bike with a 100 mm stem and only 20 mm of spacers below to put as much weight as possible on the front wheel. I also used the same wheel and tire (AlexRims ATD470 and Soma Cazadero 700x42c). For the tire pressure, I have chosen 40 psi. I did not want to go any higher because I wanted to make this test as close to real life as possible (not may ride their gravel bikes with air tire pressure above 40 psi) but at the same time, 40 psi is enough to make the fork show its strengths (25 psi that I usually use would mean almost all of the suspension is created by the tires itself). I also did all of the test runs on the same day so the weather and road conditions were exactly the same for all of the contenders.
Let’s talk about the results!
Those who follow my site closely probably already know that I tested the Lauf Grit SL fork before and find out that it is more comfortable fork than my Jamis ECO fork. And this stayed true but to my surprise, the difference between those two forks was even smaller than previously. Maybe cold weather affected the performance of Lauf’s springs. Or 40 psi tire pressure was not doing any favors to the fork but at the end of the day, Lauf Grits SL was only 5% comfier on the bumpy forest route and only 2,6% better on a fast gravel road (which at this time of the year was also a very bumpy road). The difference was not huge, but then I tested the Argon’s 18 bent fork and, boy, I was really surprised. On a fast gravel route, it was slightly more comfortable that Lauf Grit SL fork (only 1,4% but still!). On bumpy forest road, Lauf Grit SL was better but again, the difference was very small (2,6%). And then, I put the OPEN’s fork on my benchmark bike and this was a shocker! It was the most compliant fork on the fast gravel route (beating Argon’s 18 fork by 1,4%) and, what was even more astonishing, only 1,3% less compliant on a bumpy forest route than the best in that department, Lauf Grit SL fork. What do those results mean? Two things!
First: it looks like today’s gravel bikes forks reached an extremely good level of compliance (the difference between the best forks are almost negligible) and if you have a bike with something like U-turn fork from OPEN, there is simply no need to buy a much more complicated and compromised fork like Lauf Grit. And this is, indeed, a shocker!
Second: It looks like you don’t need a bend in the fork to achieve great results. And many times before I was told by the different bike designers that the shape is as important as the carbon layout you use. So you can have a fork like my Jamis ECO which in theory should be great but then you compare it to the straight fork form OPEN and see, that for sure, someone did a much better job in terms of using the right carbon in the right places (achieving both stiffness and compliance). The great result of OPEN’s fork is even more remarkable when you compare the fork lengths. My fork has 405 mm legs which should promote more compliance. Lauf Grit SL has 409 mm legs (sag included). The OPEN fork has 395 mm legs. The shortest in this comparison was Argon 18 fork with 390 mm legs. Maybe if they were a little bit longer, it would be the most compliant one. Who knows…
To sum up
During this test, I compared 4 very good forks. Unfortunately, I did not have something cheap/stiff to throw in the mix but it would certainly be interesting to find out how big would be the gap between bad and best fork. But do no worry! I will certainly do that in the future. For now, we can conclude that we simply don’t really need more solutions like Lauf Grit SL fork, but forks similar to OPEN’s one. Simple, but great at combining compliance and stiffness. Well done OPEN!