Thursday, September 04, 2014

Fat Boinger

The 2015 Mukluk 2 with a Rock Shox Bluto.
When fat bikes and suspension get mixed into the same conversation, there is always the mention of the wheels and how those fat tires are already suspension and why do you need anymore than that?

Well, that's an easy question to answer, but I don't think the question is about how tires react on trails. No.....I think this question is more about where fat bikes get ridden. 

Most folks would never think about a fat bike as a "mountain bike". The thing is, a fat bike just might be the ultimate mountain bike. So instead of pigeon holing these bikes as "snow" bikes, or bikes for sand only, one really needs to look at what other all terrain vehicles use for wheels and tires. This would give you some clues. Take a look at jeeps, ATV's, rock crawler vehicles, and off road 4X4's. All use a big, fat, low pressure tires. The game is about traction and stability. Bicycles used off road are no different.

So, why wouldn't fat bike tires work the same way? They do work that way, actually, and since traction is enhanced, the extra grip leads to increased speed, and increased speed means high impact forces on the wheels. That leads eventually to a suspension fork. So, while the question about the tires being enough suspension is often asked, I think it really reflects a misunderstanding about how capable these bikes are off road. Because it is rather obvious to almost anyone that an undamped pneumatic tire hitting trail obstacles at speed will quickly become uncontrollable.

Don't call it a fat bike- call it the ultimate bicycle all terrain vehicle.


sniffer said...

I have only ridden the pugsley. You cannot deny that the traction is amazing. They are the hoka's(maximal running shoes) of the bike world. At high speeds it seems like the tires could fold when cornering. Not sure if the fork would change this as it feels like the low pressure is more the issue. Super fun on any trails though, IMO.

Irishtsunami said...

G-T, maybe I am misunderstanding and could use some clarification. I am from the school that greatest feature of the the fat bike (which is just a mountain bike) is the low pressure and wide footprint. These are not speed machines. Yes they can go fast, but should they?

Jeeps and rock crawlers are not necessarily speed machines. Neither are fat bikes. They are capable, but come at a serious cost (efficiency). When I hear a jeep with huge muddin' tires on the interstate a 1/4 of a mile away all I think about is how bad the gas mileage is. Great off road but not with speed.

This is where my misunderstanding comes in, if I am going fast and I have a suspension fork that is giving and low tire pressure that gives, don't I run into a certain level of unpredictability in bike handling (tire folding or rolling off the rim). Then add the energy loss to a suspension fork and 5 psi tire.

For me the solution is to add pressure to the tire. So I make the tire hard which causes it to bounce and I lose the larger footprint (admittedly still larger than a 26 or 29er). But that is ok because the suspension will allow control and keep the tire in contact with the trail providing traction.

But isn't that the point of having a large volume tire with low pressure. It seems redundant to me and my simple brain. Help me understand this because at this point I think folks are adding suspension because if they don't someone else will and then they will be behind the power curve (the 29er evolution comes to mind).

I got it this is a first world problem for me but it seems like excess. Add this to all of the madness in the world and it is overwhelming. The easy answer is "if you don't like it don't buy it!" But I straight up don't understand the madness. That is all.

Guitar Ted said...

@Irishtsunami: The thing that I like to use as an example is an unmounted car tire. You've probably noticed and played with that and seen how they can bounce. They don't do that on cars because of suspension.

Anytime speeds increase over "rock crawling" speeds, this is going to happen with a rigid fat bike. i had an experience at Triple D, (a snow bike race), where I was screaming downhill at 20 something mph and the tires were about to send me on a trip I didn't want to take! Same event a year later, on an icy Humke Road downhill, I lost it due to the front end getting bounced off line, losing traction, and washing out on the ice.

Both situations would have been helped by a front suspension fork. Granted- most snow bike races won't be quite like Triple D, but if you ride in the other three seasons, and you start going down hills fast, a suspension fork will help you control the fat bike on rougher terrain at much higher speeds than you could attempt the DH at on a rigid fat bike. This is independent of tire pressure, by the way. (Normally you would run a higher psi on dry terrain anyway)

Hopefully my brother MG will see this and chime in. he has a ton of off road fat bike experience and now uses a Bluto on his Puffin to great effect.

Shane said...

I admit to never riding a fat (er ATV) bike, but may be looking to purchase come fall/winter. I can now see why getting a suspension fork is beneficial. Playing devils advocate, if I'm not doing much DHing does it still make sense to go with a shock?What are drawbacks of having a shock when having to choose? Thx in advance!

Guitar Ted said...

@Shane Buscher: If you do not see yourself doing much mountain biking, (Spring Summer fall off road), you'll not miss the fork. Otherwise, I'd strongly consider one, especially if you see yourself using this as your main off road rig.

MG said...

I'm with ya, Brother!!

Irishtsunami said...

G-T, Thanks for the response. Some of it makes sense, though I still think it is overkill. For me it is as much about efficiency over the long haul as it is about faster on the down hill. Already big and heavy, tire pressure and shock pressure are going to be essential to not burning out. After all, a great and wise bike guy once said that fat bikes are all about tire pressure! Now it must be in concert with the fork.

I am a lousy bike rider and I love that my fat bike allows me to ride without picking a line or any planning on an approach. I just use brute force to power over obstacles. I can see how a Bluto could benefit me there.

Guitar Ted said...

@Al- Here is a great write up of the Rock Shox Bluto on a Singular Puffin fat bike which will help drive my points home. It's by MG, and you can check it out here:

Roll Solo said...

It's true... You hit something at speed when your psi is not dialed to the conditions the tires will make the bike a bouncy castle. Suspension has its place and it works.

Michael Lemberger said...

Could we dispense with this notion that fat tires are prone to rolling off the rim? Assuming proper setup (a 65mm or greater rim and pressure over about 3 or 4 PSI), it's just not very likely.

Suspension would be a benefit at Triple D if the suspension mechanism works well at winter temperatures. It would definitely have been a benefit for me this past Sunday at the Kettles, where we were indeed riding pretty fast on some technical stuff. Yes, one can air the tires down for a suspension-like effect, but only at the cost of greater rolling resistance. Seems to me that optimal tire pressure is not always that which offers maximum float or shock absorption. Size really does matter, and suspension has the potential to offer the best of both worlds.

DJ Chi Wai said...

There are so many times that I wished I had a front suspension fork on my Mukluk. Some trails are abundant in roots, rocks, drop offs, you name it. Yes I could have easily ridden my full suspension or HT with front suspension, but where is the fun in that???