I am a creature of habit, especially when it comes to building up new mountain bikes. Every bike build follows a similar pattern:
- I install a fork with the manufacturer’s recommended travel
- I do a few gnarly rides and scare the crap out of myself
- I decide to get a bigger fork
- I end up loving my overforked bike
Every time I think, “This bike is designed to run an X-travel fork, I should just ride it with X-travel.” Then, as my hunger for more downhill performance grows, I always cave and either swap air springs or get a new fork altogether.
Here’s why I overfork all of my mountain bikes, and what you need to consider if you’re thinking about overforking your own bike.
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What is “Overforking” and What Does It Do?
It should be clear, but just in case it’s not, “overforking” is installing a suspension fork on a mountain bike with more travel than the bike originally comes with. In mountain biking, this is one of the most common modifications downhill-focused riders make to customize their bikes.
When overforking, many riders will increase their fork travel by 10-20mm. This has a few key benefits:
- More fork travel helps you maintain control and go faster in gnarly terrain
- A longer fork slackens your head tube angle, increasing stability
- A longer fork raises your stack height, putting you in a better position on steep terrain
As a general rule, every 10mm change in fork travel leads to a 0.5-degree change in head angle. So bumping up to a 10mm longer fork slackens out your head angle by 0.5-degrees, and bumping up 20mm gets you around 1 degree. (Of course, this is a rough estimate and it will vary depending on specific fork and frame.)
If you not only increase fork travel but upgrade to a burlier fork with thicker stanchions, then you also get the benefits of increased fork stiffness. A stiffer fork will generally feel plusher because there’s less bushing bind, and it tracks the ground better and gets knocked off line less easily in gnarly terrain.
I’ve been overforking all of my bikes for years. Here are some of my most recent overworked machines:
My Specialized Epic Evo: designed for a 120mm fork, but upsized to a 130mm fork.
My REEB Sqweeb: designed for a 150/160mm fork, but upsized to a 170mm fork.
My Forbidden Druid: designed for a 140/150mm fork, but upsized to a 160mm fork.
In all these cases, I started out with the “stock” fork travel. They performed fine on my local trails, and in reality, I didn’t really NEED a bigger fork. But the upgrade bug always bites me hard, and after a couple of months, I ended up swapping air springs to get a bit more travel out of the front. It gives me more confidence on the steep and gnarly terrain I regularly ride, so I always think it’s a worthwhile upgrade.
What Are the Potential Downsides of Overforking?
Of course, no modification comes without tradeoffs. Here are the potential pitfalls of overforking your bike:
- Geometry changes: slacker seat tube angle, higher bottom bracket, higher stack
- Reduced climbing performance
- Warranty issues or broken frames
A bigger fork slacks out your head tube angle, which is great for downhill riding. But it also slacks out your seat tube, and raises your handlebars and bottom bracket. These changes might have a negative effect on your climbing performance since you won’t be positioned over the bottom bracket as much on steep grades. Raising the bottom bracket height with a bigger fork can also reduce stability and change the cornering behavior of your bike too. How much this actually matters though is debatable.
A 10-20mm increase in handlebar or BB height sounds significant, but you’re not actually raising things up that much. The fork is at an angle — these days, usually between 63-68 degrees — so when you increase its length by 10-20mm, the vertical increase in height will actually be less (you’re going to need to do some math to actually calculate it). With handlebar position, many riders remove 5-10mm of spacers from under their bars to compensate for the bigger fork.
If you’re really in tune with changes in your bike geometry, then maybe you will notice. But I think the vast majority of riders won’t. In my experience, I hardly notice. To me, the benefits of a longer fork outweigh these potential negatives.
The bigger consideration, however, is what a bigger fork might do to your bike frame. Manufacturers design their frames to work with specific fork lengths. If you’re riding a brand-new bike with a warranty, overforking your bike could void it. In a worst-case scenario, because a longer travel fork essentially acts as a longer lever, it could produce forces your frame wasn’t designed to withstand and break your frame.
This is where I need to put a disclaimer to check with your frame manufacturer before overforking your bike.
Some manufacturers might explicitly warn against it. Many, however, have no problem with it. Santa Cruz, for example, provides a fork travel range for their frames and often approve using forks that are 10-20mm longer. My current Forbidden Druid is designed for a 150mm fork, but Forbidden specifies a maximum compatible axle-to-crown length which conveniently matches a 160mm fork.
You’ll see some manufacturers overfork their own bikes too. Yeti produces a “Lunch Ride” version of its bikes that generally have a 10mm longer fork. Orbea’s longer travel “LT” models also use a 10mm longer fork.
Generally, modern mountain bike frames are extremely tough and well-designed, so they can easily handle a 10-20mm longer fork. You could go bigger than 10-20mm, but it’s rarely recommended. Of course, anytime you modify your bike, you do so at your own risk.
The Truth of Overforking: It’s Mostly In Your Head
Above, I talked about how I don’t mind overforking my bikes because I barely notice “negative” changes like a slacker seat tube and higher handlebar and BB. So you might be wondering, if that’s the case, then how noticeable is the extra travel? The honest answer is: not that noticeable.
To me, overforking has a much subtler effect. Just the knowledge that my fork is beefed up gives me a slight mental edge on descents. If you paid attention in science class, then you know the placebo effect is powerful. It’s like riding with knee pads or a full-face helmet. The extra confidence a bigger fork provides has the biggest effect on my riding.
Am I saying that overforking your bike is pointless? No. A bigger fork still does all the things I said: absorb bigger hits and slack out your head angle. I just don’t want anyone to expect it to completely transform their bike into a mini downhill bike. That’s not how it works. If you’re looking for a big, super-noticeable change in the downhill performance of your bike, you probably actually want a whole new bike.
But if you’re a tinkerer who likes optimizing your equipment and you want to make your bike's intentions a bit more gravity-oriented, then overforking your bike is one of the best mods you can do. I always recommend it because the downsides of increasing fork travel 10-20mm aren’t that huge, and the gains are well worth it.
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