fatbike suspension fork?

#1
I am considering picking up a fork with suspension for the fatbike i just got. Its a 2016 specialized fatboy comp. I've been looking online at different ones but the rockshox one seems to require the wheels to have through axles and mine doesn't have that. Know any fork that would be compatible with my bike?
 

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mattybfat

The White Shadow
Team MTBNJ Halter's
#2
Where do you ride? I live in mooch area and see no reason for a suspension fork. I would play with tires and tire pressure. Then take that money and use the upgrade on wheels. IMO I would take weight loss over weight gain to get the most out of your fatbike.
 

qclabrat

Well-Known Member
#4
What Matty said, and a 15ta carbon fork as mentioned by Jim, but a Wren aint shabby either and are currently on sale.
 
#6
I have a 2016 fat boy" trail " model. This bike came stock with and still has an 80mm rockshock bluto on it .while I have had zero problems with it and think it rides awesome ( I mostly ride 6 mile and Allarie and chimney rock) I have heard a few others on this forum say that the Mastidon is far better fork. But I do like my Bluto
 

qclabrat

Well-Known Member
#8
I have a 2016 fat boy" trail " model. This bike came stock with and still has an 80mm rockshock bluto on it .while I have had zero problems with it and think it rides awesome ( I mostly ride 6 mile and Allarie and chimney rock) I have heard a few others on this forum say that the Mastidon is far better fork. But I do like my Bluto
what kind of pressures are you riding with the suspension forks on fat bikes? Do the low pressures and fork travel make the suspension at all unpredictable? Seems like it would work like some sort or 2 stage damper, which would make it harder to dial in right. Need an engineer's perspective @shrpshtr325: what is your professional opinion on this? I have a Wren fork but got is in the winter so have not yet ridden it with the Fatty
 

shrpshtr325

Infinite Source of Sarcasm
Team MTBNJ Halter's
#9
it would be similar to having two springs in series from a strictly mathematical perspective, one spring rate being the tire pressure/sidewall flex and the other being the shock setup. (this is standard on bikes with suspension tho), your shock is also a damped spring which you can setup its response, it could complicate things, but generally you will setup your tire pressure for grip/no bottoming out and then setup your fork to your preferences on that.

its really just changing one of the spring rates in the system (the tire) . . .
 
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#10
what kind of pressures are you riding with the suspension forks on fat bikes? Do the low pressures and fork travel make the suspension at all unpredictable? Seems like it would work like some sort or 2 stage damper, which would make it harder to dial in right. Need an engineer's perspective @shrpshtr325: what is your professional opinion on this? I have a Wren fork but got is in the winter so have not yet ridden it with the Fatty
I run @115 to 125 in the fork ...and 8 1/2 in the tires seams to be good all around pressure for me ..my weight is @205
 

qclabrat

Well-Known Member
#11
it would be similar to having two springs in parallel from a strictly mathematical perspective, one spring rate being the tire pressure/sidewall flex and the other being the shock setup. (this is standard on bikes with suspension tho), your shock is also a damped spring which you can setup its response, it could complicate things, but generally you will setup your tire pressure for grip/no bottoming out and then setup your fork to your preferences on that.

its really just changing one of the spring rates in the system (the tire) . . .
how is that parallel? wouldn't it be linear?
hit rock>compress tire>remaining force travels to the fork to dampen
This obviously happens on all bikes but with the fat tires you have about 50mm of initial compression
 

shrpshtr325

Infinite Source of Sarcasm
Team MTBNJ Halter's
#12
yea brain fart ill correct it. like i said the difference is the first spring rate and how much it absorbs, it would allow you to tune the fork for the bigger hits i guess. . .

this is one of those things thats easy for me to visualize and conceptualize, but harder for me to explain, especially in text, on a screen
 

Bike N Gear

Shop: Bike N Gear
Shop Keep
#13
what kind of pressures are you riding with the suspension forks on fat bikes? Do the low pressures and fork travel make the suspension at all unpredictable? Seems like it would work like some sort or 2 stage damper, which would make it harder to dial in right. Need an engineer's perspective @shrpshtr325: what is your professional opinion on this? I have a Wren fork but got is in the winter so have not yet ridden it with the Fatty
It's the only bike where I end up running higher air pressure in the front tire. 9-12 psi in the front with 7-8 in the rear for normal dry trails. @FitmanNJ has both the Wren and Mastodon and can compare.
 

qclabrat

Well-Known Member
#15
It's the only bike where I end up running higher air pressure in the front tire. 9-12 psi in the front with 7-8 in the rear for normal dry trails. @FitmanNJ has both the Wren and Mastodon and can compare.
not anymore...
I have his Wren :)
That's what was expecting with having to dial up the pressure when using suspension up front
 

mattybfat

The White Shadow
Team MTBNJ Halter's
#16
Wren also has gone through 4 or 5 gens already, latest version is supposedly well tuned. I used to run the old white bros dh fork years ago and that would twist so bad being inverted under off cantilevered turns. I like the idea of wren keying there stanctions.
All that said I ain't adding 5 lbs to my weenie weight fatty...
 

FitmanNJ

Well-Known Member
#17
not anymore...
I have his Wren :)
That's what was expecting with having to dial up the pressure when using suspension up front
As I've probably mentioned too many times at this point, I'm looking for max cush out of my front setup. I continue to run a Bud (for big volume) on a 65mm Nextie rim for my non-winter setup (the narrower rim being my only concession to lighter weight/efficiency/speed:)). I have the Bud inflated to what for most persons is a "snow pressure": only ~3.5 psi (I'm ~160-5 lbs), which means it compresses quite a bit on trail objects. I feel that after deforming the tire, being undampened "suspension," it springs back to normal size relatively fast. When I've tested my Mastodon (and Wren, for that matter) with a "fast" rebound setting, it seems to add to the tire's rebound and launches the bike into the air when going over obstacles...especially noticeable when I'm going over the obstacles at slower speeds, which is often the case for me. So, I feel like I get the best bump compliance by running the rebound on the slow side -- it keeps me more in touch with the trail. If I were predominently hitting trail obstacles at higher speed (or inflating the tires more?), I think that running the fork with a faster rebound might make sense. Only testing can really confirm what's most suitable, and since the rebound speed can't be changed dynamically based on terrain, speed, etc., you're really trying to find the setting that best suits the majority of what you encounter. I haven't touched the pressure too much now that I have the sag where I want it...
 

FitmanNJ

Well-Known Member
#18
...P.S.: My experience was that you can easily go overboard when slowing the Wren's rebound setting. Must be gentle -- it can be put into slow-motion!
 

JimN

Well-Known Member
Team MTBNJ Halter's
#19
All that said I ain't adding 5 lbs to my weenie weight fatty...
Yeah, the Mastodon fork is quite heavy, especially compared to the rigid carbon fork it replaced. For weight weenies, the Lauf is possibly an option, although quite spendy. I've got over 7 pounds of rubber on my bike, so I'm obviously not a weight weenie. I think the Mastodon was an incredible upgrade for me and the trails I like to ride. I'm sure I'm even slower now than I was before, but I don't care at all about going fast.
 

qclabrat

Well-Known Member
#20
Yeah, the Mastodon fork is quite heavy, especially compared to the rigid carbon fork it replaced. For weight weenies, the Lauf is possibly an option, although quite spendy. I've got over 7 pounds of rubber on my bike, so I'm obviously not a weight weenie. I think the Mastodon was an incredible upgrade for me and the trails I like to ride. I'm sure I'm even slower now than I was before, but I don't care at all about going fast.
So you likes for wildcat?