A couple of months ago I was lucky enough to get my hands on a brand new Forbidden Dreadnought. The latest bike to come out of the Canadian company, ‘Forbidden‘, the most noticeable thing about it is it’s high pivot point. Now, I was aware of this having been a feature on some bikes for a little while, but had no real idea why it existed or if it was any good. 8 weeks later I think I finally understand, and I can tell you all about it.
Traditionally most mountain bike have the pivot point between the front and rear triangles near the top of the chain ring, but a high pivot bike has the pivot point much further above the chain ring.
The high pivot isn’t a new idea, it can been seen on bikes as far back as 2000. Over the years the idea has been tested out by Trek, Honda, Ghost and the Zerode. More recently the Commencal Supreme dominated the 2018 downhill world cup podiums under Amaury Pierron and Myriam Nicole. Then following on from this success Norco released their Aurum HSP downhill bike. But up until this year the high pivot has really only been found on downhill bikes, and the occasional niche custom build.
So what has changed? High-pivot bikes have a reputation for a high resistance and draggy pedalling, so you might not think of applying this design to a trail bike. The high pivot takes up space on the frame that used to be occupied by the front deraileur and multiple chain rings. With the advances in cassettes and rear deraileurs allowing bikes to have a large range of gears, whilst only having a single chain ring, means there is space on the frame for the high pivot and idler pully. Additionally the wider boost hub standards allow for a stiffer rear triangle, meaning there is more support for longer chain stays and the high pivot. These changes now mean that more companies are looking at using high pivots on their enduro/trail bikes. Norco have released the Range HSP, and Devinci have a new high pivot Spartan in the works.
So what does this change in the pivot point do?
When a traditional bike compresses the pathway of the back wheel moves up and towards the seat tube. This shortens the overall wheel base of the bike. A shorter wheel base results in a less stable bike.
A high pivot suspension design creates an axle path that closely mimics the travel of the fork. So instead of the rear wheel moving forward, it now moves in an arc up and backwards from the rest of the bike. This results in the bike being able to carry speed, as there is more time for the wheel to move over bumps in the terrain. Essentially the bigger the bumps in the trail the further the wheel will move rearward, resulting in increased stability.
The suspension also acts differently on bikes with a high pivot point. The rearward path of the axle has more leverage on the bikes shock than the normal forces that holds the rider up. This makes the suspension feel a lot softer over bumps.
What are the advantages?
As the bikes suspension does it’s work over the rough trails, or you compress in to a corner, a bike with a regular low pivot get shorter, which throws your body weight over the back wheel. This un-weights the front wheel, and causes a loss of traction. With the high pivot bike, it gets longer under compression, which keeps your weight in the middle of the bike, and maintains your grip.
What are the disadvantages?
One of the original disadvantages of the high pivot was the amount of pedal kickback. As the bike compresses, and the wheelbase gets long, the chain would be pulled anticlockwise, causing the cranks to rotate backwards. By re-routing the chain to go up and over an idler pully, above the crank, it reduces the feel of pedal kickback. The down side of this is, the total length of the chain required for a medium Dreadnought is 128 links long, which is 2 links longer than a normal chain. So when you are first building the bike, you need two chains. Some people have voiced concerns over the additional drag having an extra jockey wheel, in reality this gives no more resistance than having some mildly muddy tires.
All the advantages and disadvantages of this design is some what irrelevant, what it really comes down to is the feel of the ride. I was really nervous about switching to a high pivot bike, I was expecting it to feel like piloting a boat, with a big turning circle, but I was pleasantly surprised. During slow speeds it can feel a bit of a drag, but once you get it up to speed it really comes to life. It took a few weeks of riding to really get used to the extending wheel base under compression, but that increase stability makes a noticeable difference. With a bit of confidence and slightly earlier breaking points you can really push in to corners, and carry a lot more speed out of them, without loosing traction. One thing to note about this, as your body weight tends to stay more central in the bike, you find that you don’t swing off the back in the steep sections, so I am now running my bars a lot higher than I previously have done.
The biggest advantage to the ride feel is it’s ability to carry good speed through the roughest sections of track. I am currently using the Fox Float X2 shock with about 32% sag, and the ramp up of the suspension feels really predictable. Despite the relatively short 154mm of travel on such an aggressive Enduro bike it has proven extremely difficult to bottom out.
As you might expect with the high pivot design it is a little bit less playfull and poppy, but you don’t buy an all out enduro weapon for jibbing around on. That being said, there have been a lot of people complain that the longer chain stays make it impossible to manual or wheelie the bike. I admit that I am terrible at doing wheelies, but even me (at 5’7″) can find the balance point on the dreadnought, and anyone who has the skills will have no problem adapting to the different balance point, and making it playful.
It might have taken a couple of weeks to adjust to the way the high pivot bike rides, but once I accepted to let off the brakes, and let the bike do its thing, then it made a world of difference to my rides. I have never done as many laps of the downhill tracks on a single crown bike before. I can definitely see why so many enduro bikes are moving towards a high pivot layout.