Ultra FS -- 400 mile update!

dadoftwinsfml

New Member
Hey all,

I've now got about 400 miles on my ultra FS and I've got some additional thoughts to share. I've made a couple mods to the bike, but before I get into that let me say I am still super happy with the bike, and I love riding it day in and out -- regardless of weather.

The mods:
- I replaced the crappy DNM rear shock with a Rock Shox Monarch RT3. This has made a WORLD of difference, and I highly recommend replacing the DNM with something better. @roshan just an FYI I would have loved to have an option for this at purchase time... for those of us who are pushing the bike to its limits the DNM that's on there simply isn't good enough for the weight of the bike, especially when matched with that awesome Wren fork. Instead of giving you that money I ended up giving it to the local shop.
- I put a bashguard on the chainring to stop the chain from flying off. This is an absolute must if you're gonna offroad the thing, and I really think the bike should come with a bashguard by default.

The repairs:
- The 1500w ultra motor is a beast. In my first 300 miles I completely chewed up the rear cassette -- I ground down the gear teeth so they were little stubs, and then the chain would slip under load. I replaced the cassette and have now adopted a riding style where I press one of the brakes a tiny bit to cut off the motor, change gears, let off the brake, then ease my way up to 1500w :). Basically I use one of the brakes as a clutch. I think the gear shift sensor is essentially useless on this bike.

Questions:
- I notice the frame looks like it might have a split in it near the rear derailleur hangar (there's some weird looking bolt / connector things down there, is that actually a frame split?) Anyone know if the bike could be converted to belt drive? If it were possible to go belt drive with a rohloff hub I think that would be the ideal setup for the bike.
- Sadly I have to report I've had the battery unseat itself a couple times on bigger drops. It's never fallen right out, but it has unseated to the point where power got cut off. It also rattles just a tiny bit on bumpy terrain... I'm wondering if anyone has also had this happen and does anyone have a solution? Could I have a bent a pin in there somewhere? What if I just jam a few layers of tape in there to keep it from rattling... might that be enough?

All of this said, let me tell you though with those two simple changes: new rear shock, and a bashguard, this thing feels AWESOME. I'm fortunate to have single track on my commute to work every day with some decent sized drops (2-3 ft), some crazy steep grades and a few jumps. The suspension now soaks everything up no problem with perfect rebound. I love this bike.
 

Deafcat

Active Member
That is awesome to hear! Good idea on rear shock option, it sounds like it was a really effective upgrade.

That's concerning about the battery unseating, they really shouldn't do that. Check that the bits that retain it are all tight and not flopping around (particularly where the terminals contact, I've heard at least once of that part being loose and causing issues).
 

MisterM

Active Member
Hey all,

I've now got about 400 miles on my ultra FS and I've got some additional thoughts to share. I've made a couple mods to the bike, but before I get into that let me say I am still super happy with the bike, and I love riding it day in and out -- regardless of weather.

The mods:
- I replaced the crappy DNM rear shock with a Rock Shox Monarch RT3. This has made a WORLD of difference, and I highly recommend replacing the DNM with something better. @roshan just an FYI I would have loved to have an option for this at purchase time... for those of us who are pushing the bike to its limits the DNM that's on there simply isn't good enough for the weight of the bike, especially when matched with that awesome Wren fork. Instead of giving you that money I ended up giving it to the local shop.
- I put a bashguard on the chainring to stop the chain from flying off. This is an absolute must if you're gonna offroad the thing, and I really think the bike should come with a bashguard by default.

The repairs:
- The 1500w ultra motor is a beast. In my first 300 miles I completely chewed up the rear cassette -- I ground down the gear teeth so they were little stubs, and then the chain would slip under load. I replaced the cassette and have now adopted a riding style where I press one of the brakes a tiny bit to cut off the motor, change gears, let off the brake, then ease my way up to 1500w :). Basically I use one of the brakes as a clutch. I think the gear shift sensor is essentially useless on this bike.

Questions:
- I notice the frame looks like it might have a split in it near the rear derailleur hangar (there's some weird looking bolt / connector things down there, is that actually a frame split?) Anyone know if the bike could be converted to belt drive? If it were possible to go belt drive with a rohloff hub I think that would be the ideal setup for the bike.
- Sadly I have to report I've had the battery unseat itself a couple times on bigger drops. It's never fallen right out, but it has unseated to the point where power got cut off. It also rattles just a tiny bit on bumpy terrain... I'm wondering if anyone has also had this happen and does anyone have a solution? Could I have a bent a pin in there somewhere? What if I just jam a few layers of tape in there to keep it from rattling... might that be enough?

All of this said, let me tell you though with those two simple changes: new rear shock, and a bashguard, this thing feels AWESOME. I'm fortunate to have single track on my commute to work every day with some decent sized drops (2-3 ft), some crazy steep grades and a few jumps. The suspension now soaks everything up no problem with perfect rebound. I love this bike.
It's a known issue about the heavy battery popping loose on these emtbs - it's due to the lock pin being slightly too short and when bounced around can come loose. Some manufacturers have custom-made a slightly longer lock pin that solves the problem (my battery has the longer pin and is rock solid - no rattles at all). However, people have reported success by adding some velcro straps around the battery/downtube. It's a cheap solution.

The Ultra does chew up cassettes. Upgrading to a much stronger SRAM EX1 cassette that's specifically designed to handle high stresses from ebikes is a worthwhile upgrade. I've got about 350 miles on my Ultra with an EX1 and there's no discernable cassette wear - and I'm not gentle when I shift - usually under full load. EX1 only allows you to shift one gear at a time to prevent undue shock on the drivetrain. I can't imagine putting a Rohloff hub on an emtb - would be very sluggish shifting when out on single tracks.


Never once had a chain fall off while I'm out on the trails on my Ultra FS (built by a different manufacturer). Have you checked if your chain is too long? But it could just be due to the unusually long chainstay length on the Bixtrix Ultra FS letting the chain flop around.
 

roshan

Active Member
Hey all,

I've now got about 400 miles on my ultra FS and I've got some additional thoughts to share. I've made a couple mods to the bike, but before I get into that let me say I am still super happy with the bike, and I love riding it day in and out -- regardless of weather.

The mods:
- I replaced the crappy DNM rear shock with a Rock Shox Monarch RT3. This has made a WORLD of difference, and I highly recommend replacing the DNM with something better. @roshan just an FYI I would have loved to have an option for this at purchase time... for those of us who are pushing the bike to its limits the DNM that's on there simply isn't good enough for the weight of the bike, especially when matched with that awesome Wren fork. Instead of giving you that money I ended up giving it to the local shop.
- I put a bashguard on the chainring to stop the chain from flying off. This is an absolute must if you're gonna offroad the thing, and I really think the bike should come with a bashguard by default.

The repairs:
- The 1500w ultra motor is a beast. In my first 300 miles I completely chewed up the rear cassette -- I ground down the gear teeth so they were little stubs, and then the chain would slip under load. I replaced the cassette and have now adopted a riding style where I press one of the brakes a tiny bit to cut off the motor, change gears, let off the brake, then ease my way up to 1500w :). Basically I use one of the brakes as a clutch. I think the gear shift sensor is essentially useless on this bike.

Questions:
- I notice the frame looks like it might have a split in it near the rear derailleur hangar (there's some weird looking bolt / connector things down there, is that actually a frame split?) Anyone know if the bike could be converted to belt drive? If it were possible to go belt drive with a rohloff hub I think that would be the ideal setup for the bike.
- Sadly I have to report I've had the battery unseat itself a couple times on bigger drops. It's never fallen right out, but it has unseated to the point where power got cut off. It also rattles just a tiny bit on bumpy terrain... I'm wondering if anyone has also had this happen and does anyone have a solution? Could I have a bent a pin in there somewhere? What if I just jam a few layers of tape in there to keep it from rattling... might that be enough?

All of this said, let me tell you though with those two simple changes: new rear shock, and a bashguard, this thing feels AWESOME. I'm fortunate to have single track on my commute to work every day with some decent sized drops (2-3 ft), some crazy steep grades and a few jumps. The suspension now soaks everything up no problem with perfect rebound. I love this bike.
1. Great recommendation about the DNM. We'll be offering more choices next time around
2. We changes Ultra spec to Sram Gx1. It's holding up really good. If it works well, we will make this standard for the next version
3. With the rear bolt - it is indeed possible to split the frame and use belt drive. But it likely won't work well with the full suspension.
4. Battery mount - send us an email and we'll send you a replacement top mount for the frame. It's easy to swap and it'll fix this issue. Perhaps the pin on your mount is a tad bit too short.

Glad to hear that you're enjoying the bike!
 
Last edited:

Dmitri

Active Member
@roshan Are you a representative of Biktrix? I have some questions:

  • The website states that a 48v/20Ah battery gives a 60+ mile range... is this throttle-only? At what speed? This measurement is inconsistent with my observations of ebikes generally. A 1kWh battery should give you twice this range (see, e.g., Bosch, Yamaha etc.). I know it's different voltage, but I'd still expect 150-200km off a 1kWh battery unless I'm missing something.
  • What is that weird headtube? I assume tapered forks fit in, but it looks 100% straight from the outside. Is it 1½" throughout or..?
 

roshan

Active Member
@roshan Are you a representative of Biktrix? I have some questions:

  • The website states that a 48v/20Ah battery gives a 60+ mile range... is this throttle-only? At what speed? This measurement is inconsistent with my observations of ebikes generally. A 1kWh battery should give you twice this range (see, e.g., Bosch, Yamaha etc.). I know it's different voltage, but I'd still expect 150-200km off a 1kWh battery unless I'm missing something.
  • What is that weird headtube? I assume tapered forks fit in, but it looks 100% straight from the outside. Is it 1½" throughout or..?
Hi Dmitri,

I am!

1. The range is just a very pessimistic estimation. We'd rather under promise and over deliver.
2. The Ultra 1000 is straight and not tapered. You could get a CaneCreek adapter if you want to use a tapered fork - we do this when you order a Wren fork with it.

Cheers
Roshan
 

Mike Sloan

New Member
Hey all,

I've now got about 400 miles on my ultra FS and I've got some additional thoughts to share. I've made a couple mods to the bike, but before I get into that let me say I am still super happy with the bike, and I love riding it day in and out -- regardless of weather.

The mods:
- I replaced the crappy DNM rear shock with a Rock Shox Monarch RT3. This has made a WORLD of difference, and I highly recommend replacing the DNM with something better. @roshan just an FYI I would have loved to have an option for this at purchase time... for those of us who are pushing the bike to its limits the DNM that's on there simply isn't good enough for the weight of the bike, especially when matched with that awesome Wren fork. Instead of giving you that money I ended up giving it to the local shop.
- I put a bashguard on the chainring to stop the chain from flying off. This is an absolute must if you're gonna offroad the thing, and I really think the bike should come with a bashguard by default.

The repairs:
- The 1500w ultra motor is a beast. In my first 300 miles I completely chewed up the rear cassette -- I ground down the gear teeth so they were little stubs, and then the chain would slip under load. I replaced the cassette and have now adopted a riding style where I press one of the brakes a tiny bit to cut off the motor, change gears, let off the brake, then ease my way up to 1500w :). Basically I use one of the brakes as a clutch. I think the gear shift sensor is essentially useless on this bike.

Questions:
- I notice the frame looks like it might have a split in it near the rear derailleur hangar (there's some weird looking bolt / connector things down there, is that actually a frame split?) Anyone know if the bike could be converted to belt drive? If it were possible to go belt drive with a rohloff hub I think that would be the ideal setup for the bike.
- Sadly I have to report I've had the battery unseat itself a couple times on bigger drops. It's never fallen right out, but it has unseated to the point where power got cut off. It also rattles just a tiny bit on bumpy terrain... I'm wondering if anyone has also had this happen and does anyone have a solution? Could I have a bent a pin in there somewhere? What if I just jam a few layers of tape in there to keep it from rattling... might that be enough?

All of this said, let me tell you though with those two simple changes: new rear shock, and a bashguard, this thing feels AWESOME. I'm fortunate to have single track on my commute to work every day with some decent sized drops (2-3 ft), some crazy steep grades and a few jumps. The suspension now soaks everything up no problem with perfect rebound. I love this bike.
Awesome suggestions! I just purchased the Juggernaut FS and would like to get the rear shock and bash guard you mentioned. Any model #'s would be greatly appreciated!
 

Mike Sloan

New Member
Hey all,

I've now got about 400 miles on my ultra FS and I've got some additional thoughts to share. I've made a couple mods to the bike, but before I get into that let me say I am still super happy with the bike, and I love riding it day in and out -- regardless of weather.

The mods:
- I replaced the crappy DNM rear shock with a Rock Shox Monarch RT3. This has made a WORLD of difference, and I highly recommend replacing the DNM with something better. @roshan just an FYI I would have loved to have an option for this at purchase time... for those of us who are pushing the bike to its limits the DNM that's on there simply isn't good enough for the weight of the bike, especially when matched with that awesome Wren fork. Instead of giving you that money I ended up giving it to the local shop.
- I put a bashguard on the chainring to stop the chain from flying off. This is an absolute must if you're gonna offroad the thing, and I really think the bike should come with a bashguard by default.

The repairs:
- The 1500w ultra motor is a beast. In my first 300 miles I completely chewed up the rear cassette -- I ground down the gear teeth so they were little stubs, and then the chain would slip under load. I replaced the cassette and have now adopted a riding style where I press one of the brakes a tiny bit to cut off the motor, change gears, let off the brake, then ease my way up to 1500w :). Basically I use one of the brakes as a clutch. I think the gear shift sensor is essentially useless on this bike.

Questions:
- I notice the frame looks like it might have a split in it near the rear derailleur hangar (there's some weird looking bolt / connector things down there, is that actually a frame split?) Anyone know if the bike could be converted to belt drive? If it were possible to go belt drive with a rohloff hub I think that would be the ideal setup for the bike.
- Sadly I have to report I've had the battery unseat itself a couple times on bigger drops. It's never fallen right out, but it has unseated to the point where power got cut off. It also rattles just a tiny bit on bumpy terrain... I'm wondering if anyone has also had this happen and does anyone have a solution? Could I have a bent a pin in there somewhere? What if I just jam a few layers of tape in there to keep it from rattling... might that be enough?

All of this said, let me tell you though with those two simple changes: new rear shock, and a bashguard, this thing feels AWESOME. I'm fortunate to have single track on my commute to work every day with some decent sized drops (2-3 ft), some crazy steep grades and a few jumps. The suspension now soaks everything up no problem with perfect rebound. I love this bike.
Do you have model #'s for the bash guard and Monarch shock?