Lessons Learned After Owning A Fat Hydra’s For A While

[Cuz Vinny]

After owning my Fat Hydra for a while I thought I’d share some of the things that work and don’t work on the bike.

1. Super wide wheels don’t work well. Stick with an 80mm wide rim to be able to use all the gears on your cassette. I have 90mm Nextie Carbon Mags with a 26X4.8 tire the chain rubs the tire on the last two cogs. I’m going to keep using the Nextie’s because I bought them but save yourself some headache and stick with 80mm wide wheels.
2. Best setup I had was Sunringle Mulfut 80mm rims and Surly Edna 26X4.3 tires. Still has the fat bike look but I could use all the cogs on the cassette. No chain rub on the tires. The tires are awesome and have tons of grip.
3. Bike needs a large chainring on the front to clear the front part of the swing arm. I’m running a 46T ring. Also keep the chain tension tight. Frame protection like All Mountain Style is a must on the swing arm close to the front ring.
4. Check all the bolts and fasteners after the first couple rides as they can come loose. This is normal.
5. Swap the chain for a KMC Ebike chain if your bike doesn’t come with one.
6. The bike makes a lot of torque so best to get heavy duty parts if available, ie steel free hub vs alloy.
7. The Whiskey Milhouse handlebars I’m using are freaking sweet and make the bike very comfortable to ride.
8. Recommend electric shifting to clean up the cable/wires on the bike. Since I ditched the throttle too I only have the brake cables and wire for the display. This is more personal preference but I hate the rats nest of wires/cables the bikes come with.
9. Lastly if you want your motor to live a long happy life don’t lug it, use your gears. It likes to spin so don‘t use the smaller cogs going up hill just because it has all this power. Use the taller cogs, your motor will be happy and so will you.

Next I’ll put together a similar list for my 27.5 Hydra.

 

[Cuz Vinny]

IMO the sweet setup for the Fat Hydra are 27.5 X 80mm wheels and 27.5X3.8 tires.

 

[loamoaf]

@Cuz Vinny nice to know about the Nextie's. I have a Dengfu E06 but one of my 90mm Nextie's had a defective rim bed, so I'm waiting for a replacement - happened to be the rear one so I didn't get a sense of chain rub with it on - I have Vee Snowshoe 2XL's (5.15") and 4.8" studded Snow Avalanches for winter trail riding and 42mm inner width 29's with 29x3 Vittoria's for summer, but I've been toying with the idea of a 27.5 fat setup with 3.8-4" tires for this frame and then use the 29's where more appropriate - the Mastodon & E06 frame looks large with them on there! Wouldn't mind a bike that's not so hefty either, my whole setup is about 59lbs and I'm still young and fit so something that's less ovbious and can be flung around a little easier would probably be more ideal for me. I think I may grab some Mulefut 80's for the studded Vee's so I don't need to swap tires on the wheels - I got a little compressor with a tank to seat my tires more easily but still it's a chore - even if only swapping a couple times a year I'd rather spend the money on a set of rims that last. Plus you have wheelset ready to go for another build if you choose to do so! I wouldn't mind the efattie, a slimmer emtb, and then an unassisted HT frame with a Pinion gearbox.

On the steel freehub, if you're building your own wheels, an ebay seller wheelsnsprockets has Fatback 197mm hubs with steel HG freehub bodies for $99. They're symmetrical so easy to build with symmetrical rims. I like Onyx Racing fronts - little pricey but super beautiful and they seem to spin forever with those massive bearings. I would be interested in a set of Hadley hubs but am a little apprehensive to have something so expensive and not steel (Ti freehub body) hooked up to something like a modified M620.

For cable management, a solution that's clean but allows you to easily change things around or remove the clips for maintenance are Jagwire clips. The have 4/4mm, 4/5mm, and then rotating hooks that are 5/5mm. Here you can see I use a whole mess of them to keep the front clean. I would like this solution for the cleanest cockpit: 750C display over the stem - but the display doesn't have that extra remote thumb switch on it - and then the brake input and throttle input goes right into the display, with one cable going back into your frame. Easier to have your wires run along or inside the bars to the display instead of along your shifter/dropper/brake lines into the frame. On my current setup this would only clean up the Tripwire brake cable - but the size of the switch on it kind of makes it a prime candidate for hiding inside the handlebars. I would like a slim 3D printed throttle though just for walking up stairs or clearing roots/rocks that might result in a pedal strike if I were to pedal. I'd love for wireless shifting but I'm hesitant to add the D1X module onto a chainstay vs something like SRAM AWS that's a wholly contained unit - but that price difference...

I originally ordered a 50T and a 40T NW chainring to test sizes, then also decided to jump the gun and order a 30T Wolftooth stainless steel... it has built in threads and standoffs but is meant to mount on the inside of the spider so I'm unsure if it will get the chainline correct on a 197mm setup... I need to do a test on the full travel of the suspension to see if I can swing a 32T because that's the smallest Wolftooth I'd be able to fit on the outside of my spider. I have a 51-11T 11spd all stainless steel Shimano cassette on the rear and like you said the motor is happier when it's spinning faster - runs cooler and more efficiently - just like optimum human pedal cadence is around 80-100rpm! Aside from the super tall 29x3's I run for spring/summer, I also plan to haul equipment and supplies to assist with trail maintenance so the lower the gearing the better - hope garner a little goodwill with the mountainbikers here who can be pretty aggressively against ebikes... I also just moved on a mountain and it's a steep 600' or so climb to my neighborhood from the main road if I ever get the weird urge to ride on pavement!

 

[Cuz Vinny]

Here’s what I’m talking about with the 90mm wide Nextie’s. On the tallest two cogs of the cassette the chain rubs the tire.

 

[loamoaf]

Brutal! Which tires are those? I had hoped the 90mm Nexties would help square the tire profile a bit and keep those shoulder lugs from poking outward... At least I have time before winter here, I may request Nextie send me an 80mm replacement rim for the rear instead to avoid this and still be able to ride my big chunky beige balloons. When I was seating the bead on my rear I heard a nasty crunch and a rush of air, turned out there were 2 thin spots on the rim bed that I could push in with my thumb - so they won't seat and because this is a solid rim bed with no tape it can't hold air. I can't believe I didn't catch those while handling the rims and building up the wheels and I should have been a little more weary when one rim was about 50g lighter than the other - the 29's only had a 2g difference, but so far Nextie's been killer with customer service. I'm fighting the urge to order a pair of 27.5 fat rims from them with the replacement for my defective 26er. The carbon is so ridicously light and I love the sound it makes when I tap it.

 

[Cuz Vinny]

Brutal! Which tires are those? I had hoped the 90mm Nexties would help square the tire profile a bit and keep those shoulder lugs from poking outward... At least I have time before winter here, I may request Nextie send me an 80mm replacement rim for the rear instead to avoid this and still be able to ride my big chunky beige balloons. When I was seating the bead on my rear I heard a nasty crunch and a rush of air, turned out there were 2 thin spots on the rim bed that I could push in with my thumb - so they won't seat and because this is a solid rim bed with no tape it can't hold air. I can't believe I didn't catch those while handling the rims and building up the wheels and I should have been a little more weary when one rim was about 50g lighter than the other - the 29's only had a 2g difference, but so far Nextie's been killer with customer service. I'm fighting the urge to order a pair of 27.5 fat rims from them with the replacement for my defective 26er. The carbon is so ridicously light and I love the sound it makes when I tap it.

Tires are Maxxis Colossus 26X4.8. Something like a Surley Edna 26X4.3 might work but I haven’t tried them.

 

[Cuz Vinny]

Rear tire width. Looks bad a**

If I had to do it all over again I get 27.5 x 85 Nextie Mags with a 27.5X3.8 tire.

 

[MacCrackin]

After owning my Fat Hydra for a while I thought I’d share some of the things that work and don’t work on the bike.

9. Lastly if you want your motor to live a long happy life don’t lug it, use your gears. It likes to spin so don‘t use the smaller cogs going up hill just because it has all this power. Use the taller cogs, your motor will be happy and so will you.

9. Lastly if you want your motor to live a long happy life don’t lug it, use your gears.
It likes to spin so don‘t use the smaller cogs going up hill just because it has all this power.
Use the taller cogs, your motor will be happy and so will you.

Same with cordless tools - I find it odd so many don't shift to low gear driving screws,,
and you can hear the motor just crawl with torture trying.
When low gear,, it would be effortless. And if they claim it's junk,, they forced it into junk.
Cheers

 

[MacCrackin]

View attachment 123303









Here’s what I’m talking about with the 90mm wide Nextie’s. On the tallest two cogs of the cassette the chain rubs the tire.

Quote [ For cable management, a solution that's clean but allows you to easily change things around or remove the clips for maintenance are Jagwire clips. The have 4/4mm, 4/5mm, and then rotating hooks that are 5/5mm.]

Those are great looking clips - and I like the butted beefy looking bars. Are they specific brand,
or is they the bars used on 'Specialized' bikes that were seen recently?
Still researching for near future E-Bike..
Cheers

 

[Jon A]

Good stuff Cuz Vinny. But if you don't mind, I'll offer an alternative perspective on the below.

1. Super wide wheels don’t work well. Stick with an 80mm wide rim to be able to use all the gears on your cassette. I have 90mm Nextie Carbon Mags with a 26X4.8 tire the chain rubs the tire on the last two cogs. I’m going to keep using the Nextie’s because I bought them but save yourself some headache and stick with 80mm wide wheels.
2. Best setup I had was Sunringle Mulfut 80mm rims and Surly Edna 26X4.3 tires. Still has the fat bike look but I could use all the cogs on the cassette. No chain rub on the tires. The tires are awesome and have tons of grip.

Another solution is a different drivetrain.

Having run quite a few different tires, including some quite good ones (Van Helgas, 3.8" Gnarwals, Wrathchilds, even Johnny 5's) on 65 and 80mm rims, and then finally the Johnny 5's on 100mm rims, I've found there is a very wide spread in capability and a huge gap between the big J5's on 100's vs even the same J5's on 80's. J5's on 100's give completely next level traction compared with very good tires like the Wrathchild or even the very same J5's on 80's (and I would assume the same would be true for the 2XL's as they are even wider and are supposed to be even better for deep snow). Compared with ~4-3.8" tires, it's not even in the same zipcode.

If one is spending this much money on a fatbike, one of their goals may be to go through snow as well as they possibly can. For that end, one doesn't want to compromise rim width and tire size. If the frame will fit the biggest tires and you use smaller ones or even the big ones on narrow rims (somewhat neutering them), you're leaving a ton of capability on the table. Just today, when climbing a steep snowy hill that I would have struggled to make it up at all on my other fatbike on its Wrathchilds, I quite literally popped a wheelie under power for a few feet because the rear J5 hooked up so well. I've just never experienced any other fatbike tire hook up that well on any sort of snow. Next level traction.

Back to the drivetrain. I had thought I might be able to make it work with my 12 speed Sram GX by spacing the chainring out far enough, but the chainline which would result on the biggest cogs would be really nasty. That may be OK for a manual fatbike (most have pretty crappy chainlines in the biggest cogs). But when you add Bafang power, I think a chainline that bad is just asking for a breakage.

While I considered the Box One Prime 9, which should offer similar geometry, I ended up going with the Sram EX1. Yes, the cassettes are ridiculously expensive, but they should basically last forever with the cheap replaceable top 3 gears. Here's why:

That's the EX1 cassette compared with the Sram NX 12-speed cassette on identical freehub bodies. As you can see, the large cog of the EX1 is between the 3rd and 4th cog of the 12 speed. This allows me to have a very, very good chainline for the entire cassette and have gobs of tire clearance. The J5's on 100mm rims have clearance to spare.

The EX1 isn't perfect, I have my nitpicks (as I do with everything) but in the end it works well and solves the problem. Allowing my E06 to run wheels/tires which give it the capability to run through stuff that would stop other fatbikes in their tracks is well worth it to me.

 

[loamoaf]

Nice write up. I ordered a set of Mulefut 80's on CM sale for my studded 4.8's so I don't have to deal with sealant or removing the 2XL's on the Nexties. I originally went to build with an EX1 drivetrain but didn't read into as much as I should have, tried to dodge shelling out $3-400 for a cassette and got a standard 8 speed not realizing the EX1 uses 10 speed spacing. It's got a really satistyfing heavy thunk when shifting - feels very confident and deliberate and the pulley arm clutch pin thing is incredibly handy. Lever operation though simply isn't as refined and light as the XTR I have now though - EX1 has very little uptake and heavy weight, XTR has a slight bit of uptake with a much lighter weight.