Let's talk about FAT BIKES

[MikeFairbanks]

I don't know if there's an official FAT bike thread, but I've been looking at them and have learned some basics. Correct me if I'm wrong but:

1. They are slow on pavement.

2. They are faster than most mountain bikes on the rough stuff because the big tires (at very low pressures....7psi is not unusual) conform to obstacles instead of hitting them and bouncing up.

So, what I'm wondering is how they compare to full-suspension mountain bikes. Do the fat tires absorb negative energy (so-to-speak) whereas full suspension bikes must use shocks and such, or is it better to have the full-suspension to absorb the energy but keep the momentum going?

And, of course, there's the issue of the motor.

Any thoughts? I know nothing other than what I wrote above, but they sure do look cool.

Here's a link at MTBR (Mountain Bike Forums), and an example of a FAT bike. http://forums.mtbr.com/fat-bikes/fat-bike-faqs-498930.html

 

[MadRhino]

They are better than any other bike on soft terrain: Mud, sand and snow.
Other than that, they are mules.

 

[lazarus2405]

I'll preface this by saying that I'm an experienced mountain biker, but I haven't straddled a fat bike either. The impressions I get are from two friends with experience on them and the occasional chat I'll have when I see one on the trails.

Point 1 is more or less correct, but part of it is the low tire pressure and knobby tread. You can get slick(er) tires for them, like these, and increase the pressure. They'll still be slower than most things out there, especially at accelerating. We're talking about having to spin up tires that range from 2.5lbs to 3.5lbs (each). That'll wear a commuter out fast compared to a road/touring/commuter/hybrid bike, but it's a moot point with a motor.

Point 2 is tricky. Mountain bikers run relatively low pressures anyway (25-30psi) to prevent that bouncing-off-obstacles stuff. In low traction situations, yeah, the super low pressure lets the tires conform to everything and grip like an angry barnacle. Sand, snow, wet stuff, loose rock, steep grades, combinations of two or three of those at once, the fat bike has a big leg up. I'm not sure that those things translate into "faster". These bikes aren't made for speed. They're made to go places no other bike can.

The difference between a fat, low-pressure tire and a shock in terms of suspension is that the shock is controlled. How much force it takes to compress the shock (spring rate), how quickly it compresses (compression damping), and how it decompresses after the hit (rebound damping) can all be controlled and tuned to the rider and the conditions. A tire will absorb small bumps by deforming, but there isn't much more you can do with it.

So it depends on what you're doing. Where, how, and why are you thinking of riding such a bike? It could be a great tool for the job, or it could be a distraction. If you want to rip some trail, you're better off with real suspension. If you see sand or snow in your future, the fatbike could be the ticket.

 

[mabman]

If I was going to get a fat bike this is the one I would go for to use as a platform. http://www.ezbeachattachments.com/single-speed-cruiser-beach-bike-yellow

 

[MikeFairbanks]

Maybe I should try my new commute that runs trail with less air pressure. Right now I'm rattling teeth with large, goofball to tennis ball size gravel in may areas. They are utility roads for the power lines. I was keeping my knobbies at 55psi.

What should I try, 20psi?

 

[hillzofvalp]

depends on weight and tire size. 2.1" 26" tire I shoot for 30-40psi and I'm 190. With my big apples on my 29er I run 25psi.

I thought of doing a fat bike, but then realized how inefficient it would be. Then again, my 29er isn't probably very efficient either.

 

[MikeFairbanks]

Well, my commute is mostly rough trail, so I'll try 25psi.

 

[liveforphysics]

Greenmachines on this forum has a fatbike ebike. It's a surly I think. He likes it. He does a lot of beach-riding.

 

[mabman]

Well, my commute is mostly rough trail, so I'll try 25psi.

I would start at 40psi. You risk pinch flatting running low tire pressures on a 26" tire unless you are running tubeless.

 

[Ykick]

Well, my commute is mostly rough trail, so I'll try 25psi.

I would start at 40psi. You risk pinch flatting running low tire pressures on a 26" tire unless you are running tubeless.

Very true, I weigh 240lbs and somewhere around 30psi pinch flats (snake bite) have gotten me when hopping fairly mild curbs. Slime won't help seal either since they're on the inside circumference of the wheel.

Fat 3"-5" tires are probably much more forgiving though. These Fatty bikes have grabbed my attention before.
Hanebrink does the high flotation tire, soft surface thing too.

 

[hillzofvalp]

holy crap looks like 1:1 drive:

 

[mabman]

A gentleman in Southern Oregon made a few fat bikes years back. He lives in area with alot of sand dunes and used them for beach combing.

This bike is actually using 17" motorcycle inner tubes with a covering of shrimp net!



I ran across this guy due to a CL outing. I ended up with the blue bike, now black, and don't have a decent shot of it but do have this one of the rear end. Can you say drillium?


This was his second bike and he used motor cycle tires once again that he ground off the knobs and cut out the sidewalls for more flex.






This was his last one and it had a jackshaft gear train and some little big tires.



And this last one is one I saw online awhile back and got a kick out of that has the same type of drivetrain.
View attachment 2

And then there is always someone that has to be that much different.

 

[dogman dan]

I ride a lot of loose sand with 2.3 front and 2.5 inch rear knobbies. It's as big as I can go with the mongoose blackcomb frame without fabricating a new swingarm. It floats good enough, but 3" would be nice. My pedaling trail bike has 3" rear and 2.3 up front. I found 3" up front made it harder to steer for some reason. Both bikes float a lot better than a 2" tire in the loose sand.


With half decent FS, you don't have to run low pressure, the shocks do the work. If you lower your tire pressure too much with a hubmotor, you'll just start getting pinch flats. I run about 60 psi. Too bad you don't have the budget to buy several frames and try them all. Every month you are dreaming about something else. I know the feeling, it took me several years to scare up affordable nice FS bikes. Meanwhile I had to use some pretty bad wallbikes till I found better bikes cheap.

I think there is no substitute for suspension, but it has to be better than the really primitive early stuff still seen on Wallbikes. That's why I came to like the cheap mongoose blackcomb. For a cheap bike, it has a nicer rear suspension link. Carrying battery is a bitch of course on a y frame, but that's whrere the lipo comes in handy.