Today we are back in the Bike Lab for a cool experiment. We’re going to try to answer the question “Is a slacker MTB always better?” It’s a trendy topic in mountain biking these days. We see a lot of folks over-forking their bikes or using angle-adjust headsets to make their bikes slacker. Why would you want to do this? How do you do it? Is it going to be better? Stick around to find out.
Why a slacker mtb
Let’s start things off with the why. Why would you want a slacker mtb? There are a couple of benefits, but those benefits don’t come without trade-offs. Let’s get into it. A slacker head tube angle is going to make your bike more stable at high speeds. It’s also going to roll over obstacles in the trail a bit easier. Your bike is going to feel more confident in steep terrain as well. All of these things sound great. So what are the cons? When your front end gets slacker, your handling gets a little vaguer. You lose some of the snappy feeling in your steering. Your bike will also get longer. The wheelbase is going to increase because you’ve essentially moved the front wheel further out in front of you. That longer wheelbase can make a long bike even longer — not always ideal for tight and twisty trails. Lastly, some of the things you can do to make your bike slacker are going to potentially void your warranty. Always consult with your frame manufacturer before you try any of these things and proceed with caution.
Now it’s time for the how. How do you make your bike slacker? There are a couple of ways that work really well and some others that don’t. The most common way to make your head tube angle slacker is by over forking your bike. For example, you have a Yeti SB130 that comes with a 150mm fork. You go ahead and swap that air spring/fork for a 160mm version and you’ve pretty much made your bike 0.5° slacker. As a general rule of thumb, for every 10mm of extra fork travel you add, you’ll make your bike about 0.5° slacker. There are a couple of things that will change this, but that’s a rough gauge. Keep in mind, when you over fork your bike you’re also going to lift your bottom bracket as well as make your seat tube angle steeper. These will affect your fit and handling on the bike.
Another way to get a slacker mtb is by using an angle-adjust headset. Essentially, these are a series of offset headset cups that will change the angle at which your steerer tube goes through your frame. Dumbed down, it’s a headset that holds your fork at a slacker angle than your frame’s actual head tube angle. These usually range from about 0.5° – 2° of adjustment. Counterintuitively, they actually lower the front end of your bike. If you think about how they work, they kick the front wheel out further without changing the height of your fork. The front-end drop with these can be substantial. In turn, they will make your seat tube angle steeper as well as bring your bottom bracket closer to the ground. Again, these side effects will have an impact on your bike’s handling.
Lastly, there are two other common methods of changing your head tube angle. The first is a flip-chip. These are pretty common on bikes. They allow you to change your bike’s geometry pretty quickly. The second and least common method is with an external headset cup that simply adds height below your frame and above your fork crown. Think of it as adding height to your fork without the benefit of getting more travel.
The bikes we used for this test are the Yeti 160E and the Orbea Rise. Both of these bikes have integrated headsets. That limits the options you have for using an angle-adjust headset. We ended up going with a product from 9point8 called the Slackr. It’s basically an external, angle-adjust headset cup. It’s a clever solution for bikes that have integrated headsets. The install went really well and only took about 15 minutes without having adequate tools or even a work stand. Done properly in a shop environment it should only take 5-10 minutes. On my Orbea Rise, the head tube angle difference came out to about 1.5° with an 11mm drop in the height from the head tube to the floor. On Zach’s Yeti 160E the angle adjustment was closer to 1.6° with a 12mm drop.
slacker mtb: Ride Impressions
It’s interesting how one change can make such a substantial difference to a bike. The angle-adjusting headset really made the Yeti a different bike. Any bike at 62.9 degrees is going to be something meant for descending. Climbing was a bit trickier. The tight, slick rock maneuvers had to be taken more with speed and commitment to the line instead of nimbly picking your way through the tricky stuff. When it got really steep, the front end needed to be watched closely or you’d end up wandering into the bushes but with a little practice, it was manageable.
When pointed downhill it became a freight train. Few declines were too steep. Point, shoot, let go of the brakes as much as you dare, and let it rip was the best method. I felt a loss of playfulness and it took more effort to change directions but it’s a trade-off. When it gets gnarly and steep it’s kind of amazing. The drawback though is that on somewhat mellow, everyday trails I feel like it lost a bit of the fun factor.
For me, it comes down to the terrain and you’re riding style. If you have truly steep and nasty trails it turns the SB160e into a self-shuttling trail destroyer. But if that’s not the type of trails you ride or you’re not quite that type of rider the stock geometry is likely the better choice on the Yeti.
I had a completely different experience than Zach. To be fair, my bike is a completely different bike, to begin with—my bike is a bit more on the trail bike side of things. I mostly noticed some positives with a couple of things I wasn’t a huge fan of. The first thing I noticed was the drop in the handlebar height. It pulled my weight further over the front of the bike. On the climbs, it almost counteracted the negative effects of a slacker front end. I noticed the handling wasn’t as quick and snappy as I’m used to on that bike. It wasn’t a huge penalty, but it was noticeable.
On the descents, the bike really opened up. It added a degree of capability to the Rise that I really appreciated. It rolled through rough terrain faster without getting hung up or deflected as much. I did notice the handling was slower on the DH as well. It took a couple of turns to make the adjustment, but once I did, the handling felt in line with other bikes in the all-mountain category. The drop in the front end was noticeable on the descents as well. I think I’d counteract this with a riser bar or adjusting the spacer stack on my steerer tube.
slacker mtb: The verdict
Is a slacker MTB always better? Simply put, no. Remove the word always from that question and the answer totally changes. Slacker can be better. I think it depends on a couple of factors — the type of bike, the rider, terrain, and riding style.
What is the best way to make a bike slacker? Headset cups or over forking? We’re going to go out on a limb here and say both. Not either-or, but both — at the same time. If you run an angle-adjust headset and pair it with a 10mm longer fork, you can almost isolate the head tube angle change from the rest of the bike’s geometry. They each counteract each other’s side effects.
If you can only do one, we’d suggest over forking and paying the seat tube angle penalty. It’s the simplest and easiest option. It can be the cheapest too—a new air spring will run you about $45-50.
The best bikes to make slacker
We’ve narrowed it down to two categories of bikes that can benefit from getting slacker. The first is trail and all-mountain bikes. Bikes like the Rise that have some relatively conservative head tube angle numbers can really benefit from a bit slacker front end for the right rider. I’d argue that the HTA on the Rise is good for the majority of people we sell them to. Other riders who are truly pushing the limits of the bike, could benefit from a little slacker front end. Bikes like the Ibis Ripley could use a slacker front end for the right rider as well. Now, I’m not saying that if you have a Rise or a Ripley, you need to rush and buy all the things to make the front end slacker. I’m saying that if your terrain and riding style (aggressiveness) warrant a slacker front end, these bikes are good candidates for it.
The last kind of bike I’d want to make slacker is something like my Norco Range. It’s super slack to begin with. It’s also longer than a city bus —it doesn’t need to be slacker or longer.
The other category of bikes that can benefit from being slacker is older and more conservative bikes—bikes that are 3-4 years old and are starting to fall off the cutting edge of bike geometry. Making the head tube angle slacker on these isn’t going to instantly bring all the geo up to modern standards, but it can help prolong your enjoyment of the bike for another year or two. Bikes like the previous generation Tallboy come to mind. They’re solid bikes that are built to last. In 2022 their geometry is starting to look a bit dated, though. By making the front end a bit slacker you can bring it a bit closer to modern norms. Again, not everyone needs or wants this, but for the folks that do, it can be beneficial.
So there you have it. The who, what, when, where, and why of a slacker mtb. We’ve tried to stay pretty high level here. This is a complex topic with a lot of moving parts. We wanted to stay out of the weeds and keep it simple. We haven’t covered every last detail, but this should serve as a pretty comprehensive guide to help those looking to make their bikes slacker.