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My fatboy is scheduled to come into the shop tomorrow and should be in my sweaty palms early next week. I have some questions about the fat bike and the people at the shop have no experience with them. I'd appreciate some info from folks with experience.

First, not to provoke the usual verbal donnybrook, but what pressure should I be using in these 4.6 inch tires for various surfaces? I have no idea. I tend to run my 2.5 inch tires on the high side at about 40 - 45 lbs. I'll be riding all sorts of surfaces from snow to forest hillsides with or without a trail including soft stuff and rocks.

Second, I'll need an extra tube right away and no one locally stocks fat bike stuff. What tubes do folks recommend and where to get them? What size tube also given that the tire is advertised as a 4.6 inch tire?

I'll be doing some cross country (and I mean cross country) riding in areas with star thistle and some other pokey things like the occasional goat head. Are there any really tough tubes that come in this size?

Thanks in advance. I'm really stoked about a new bike and can hardly wait. My bike will now be fatter than my belly!
 

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pressures vary a lot depending on the rider, terrain etc. In snow, I run my 4" tyres down to 4psi. I have heard people running down to 3psi. Makes for slow going on hard surfaces but on snow it is great. On dirt, I ride closer to 8psi. Much harder than that and the bike will bounce on rocks a roots, much softer and it bounces on cadence. Bigger tyres use less psi. Your finds might be much different to mine as I would never run more that 30-35psi on 2.2-2.4" tyres.

Tubes will expand to fill the tyre casing. it is the tyre holding the pressure, not the tube however, if you do run a smaller tube, it will have to stretch to fill the tyre. In my opinion, this does not make it any more susceptible to punchers but what might have been pin hole and slow leak on a fat tube could be tear and instant flat that is not fixable. It is more difficult to fix a skinny tube as the stretch can peal the patch off. Just find the biggest tubes you can, perhaps DH 2.8s etc
 

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If you're riding mostly packed trails start off about 10-12 psi and go up or down from there depending on the firmness of the surface and personal preference. You've been riding awhile, so you'll probably get feel for things pretty quickly. I agree with most of what mtbXCgeek said. Where I differ is about punctures. Where I live in AK there are no thorns and I've never had a flat on a fat tire. As I'm sure you know, its a different story in CA. In your area, I'd consider running heavier, thicker Surly tubes. The tires themselves are pretty thin; never checked out the GCs though. The 2.2-2.75 tubes work great, but I think they'll be too thin when stretched out to give you puncture protection. Also can be hard to patch, as previously noted. If you choose to go with the lighter tubes, you might want to use sealant in your tubes or tire liners. Or, perhaps, rig them tubeless. This is conjecture on my part, cause like I said punctures aren't an issue for me. Welcome to the fat side. Enjoy the new bike and let us know how things work out.
 

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turtles make me hot
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First thing you should do when you get that bike home is set it up Ghetto Tubeless.
Pick up a pair of 24" Q Tubes and split them. It'll set up easy and you'll never give the tires a second thought while you're out riding.
I weigh 250 pounds and I have my 4.8 tires on 100mm rims at 9 psi in the rear and 8 front. My lighter friends use less.
You'll see.
Congrats on the Fatboy. I spent more money than that bike costs building a 907 and it's heavier than the Spesh. Bike's pretty damn light for the money.
 

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Yes, do split-tube tubeless (such a much more elegant name than "ghetto tubeless"), if you keep your sealant levels up you should have no problems with thorns.

I have been doing split tube for a long time on many of my 29er wheels. I noticed the Stans goober production is much higher than in my narrower wheels. I guess that's because there's more air in there to interact with the sealant. All that to say, add sealant every 45-60 days and you should be good.
 

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Is the the TGR Telelmike?

I'm pretty new to the fat bike scene as a few month's ago. You will need to experiment with tire pressures, regular tire pumps do not measure well at low pressures, I bought one of these.
SKS Airchecker Pressure Gauge 0 140 PSI 10 Bar | eBay

For my self around 200 pounds geared up with the tires I have this is what works for me, your mileage will vary. Also running tubes right now, probably try tubless at some point. A 26" tube in the 2.75 range will work fine as a backup and what is in my tires now, I have yet to need one yet. I've just ridden snow and typical Tahoe decomposed granite and granite drops,etc, no pokey stuff.

I find about 8.5 pounds is about right for the front, any less and I get some self steer. I run about 6.5 pound's in the back.
 
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