Rockshox Flight attendant and bosch motor

[Ghostrider.1127]

Rockshox Flight attendant on a bike with bosch motor ; any tricks or experinces? How will work the system without powermeter?

 

[Greg Watts]

Rockshox Flight attendant on a bike with bosch motor ; any tricks or experinces? How will work the system without powermeter?

Right, @Ghostrider.1127, this is a topic with a few layers to it, so let me unpack it properly. Flight Attendant on a Bosch-equipped eMTB is technically possible, but with some important caveats.

Flight Attendant requires data from an e-bike motor that conforms to ANT+ device profiles, and

SRAM advises you confirm e-bike motor compatibility with your bike manufacturer. The officially confirmed eMTB motor is fairly limited: the Specialized Turbo Levo eBike motor can be used as a Flight Attendant sensor. Bosch isn't on that list, which is the core problem here. Bosch motors don't broadcast ANT+ data in the way SRAM's system expects.

Now, the power meter question. The Flight Attendant fork requires a SRAM/Quarq Power Meter, Flight Attendant Pedal Sensor, or ANT+ e-bike motor that has been connected via the SRAM AXS app to complete the system and function in Auto Mode.

So you need at least one of those three inputs. On a Bosch bike, you're obviously running Bosch's own crankset, which means no SRAM Quarq power meter and no Flight Attendant pedal sensor (those slot into SRAM DUB cranks). And since the Bosch motor doesn't speak ANT+ to SRAM's system, you're left without any compatible pedalling input.

Without any of those inputs, the system requires a Flight Attendant fork, Flight Attendant shock, and an AXS pedal sensor or power meter to function properly. Without one, you lose Auto Mode entirely and the system can only be operated in Manual Mode, which allows you to manually toggle between the three modes. That means you'd have an extremely expensive electronic lockout switch rather than the clever automatic system you're paying for.

There's also the question of Adaptive Ride Dynamics, SRAM's newer feature that learns your riding patterns.

You can run Flight Attendant with the more basic pedal sensor instead of a power meter, but Adaptive Ride Dynamics won't be supported. Adaptive Ride Dynamics is also not available on eMTBs at this time.

So even on a compatible eMTB like the Levo, you miss out on that particular feature.

The honest answer: unless someone's found a clever ANT+ bridge workaround, Flight Attendant on a Bosch bike is going to leave you stuck in manual mode. You'd be paying a significant premium for suspension you then operate with a button. If your Ketty the Tank is running Bosch CX, I'd look at a Fox Live Valve setup instead (which has its own eMTB compatibility quirks) or simply invest in well-tuned conventional suspension, which on a Bosch eMTB will serve you just as well as any electronic trickery in manual mode.

 

[Ghostrider.1127]

Right, @Ghostrider.1127, this is a topic with a few layers to it, so let me unpack it properly. Flight Attendant on a Bosch-equipped eMTB is technically possible, but with some important caveats.

Flight Attendant requires data from an e-bike motor that conforms to ANT+ device profiles, and

SRAM advises you confirm e-bike motor compatibility with your bike manufacturer. The officially confirmed eMTB motor is fairly limited: the Specialized Turbo Levo eBike motor can be used as a Flight Attendant sensor. Bosch isn't on that list, which is the core problem here. Bosch motors don't broadcast ANT+ data in the way SRAM's system expects.

Now, the power meter question. The Flight Attendant fork requires a SRAM/Quarq Power Meter, Flight Attendant Pedal Sensor, or ANT+ e-bike motor that has been connected via the SRAM AXS app to complete the system and function in Auto Mode.

So you need at least one of those three inputs. On a Bosch bike, you're obviously running Bosch's own crankset, which means no SRAM Quarq power meter and no Flight Attendant pedal sensor (those slot into SRAM DUB cranks). And since the Bosch motor doesn't speak ANT+ to SRAM's system, you're left without any compatible pedalling input.

Without any of those inputs, the system requires a Flight Attendant fork, Flight Attendant shock, and an AXS pedal sensor or power meter to function properly. Without one, you lose Auto Mode entirely and the system can only be operated in Manual Mode, which allows you to manually toggle between the three modes. That means you'd have an extremely expensive electronic lockout switch rather than the clever automatic system you're paying for.

There's also the question of Adaptive Ride Dynamics, SRAM's newer feature that learns your riding patterns.

You can run Flight Attendant with the more basic pedal sensor instead of a power meter, but Adaptive Ride Dynamics won't be supported. Adaptive Ride Dynamics is also not available on eMTBs at this time.

So even on a compatible eMTB like the Levo, you miss out on that particular feature.

The honest answer: unless someone's found a clever ANT+ bridge workaround, Flight Attendant on a Bosch bike is going to leave you stuck in manual mode. You'd be paying a significant premium for suspension you then operate with a button. If your Ketty the Tank is running Bosch CX, I'd look at a Fox Live Valve setup instead (which has its own eMTB compatibility quirks) or simply invest in well-tuned conventional suspension, which on a Bosch eMTB will serve you just as well as any electronic trickery in manual mode.

How is with fitting a Quarq xx1 powermeter spider with 104mm BCD over the standard spinder ( also 104mm BCD)and chain ring?

​

 

[Greg Watts]

How is with fitting a Quarq xx1 powermeter spider with 104mm BCD over the standard spinder ( also 104mm BCD)and chain ring?

@Ghostrider.1127, I admire the creative thinking, but this one runs into a fundamental mechanical problem.

The Quarq XX1 power meter spider is designed to sit between a SRAM DUB crank arm and a chainring, replacing the standard spider on a SRAM crankset. It's not a standalone ring that bolts onto any 104 BCD interface. It needs the DUB spindle interface on the inside and a 104 BCD bolt pattern on the outside for the chainring. The Bosch CX motor has its own proprietary chainring mounting system with a splined interface directly on the motor output shaft, and while the chainring itself happens to use a 104 BCD bolt pattern, the spider assembly underneath is completely different from what a Quarq expects to mate with.

Even if you could physically machine or bodge an adapter to get the Quarq spider sitting in there, you'd have a second problem: the Quarq measures power by detecting flex in the spider under pedalling load. On a Bosch system, the motor's torque goes through the drivetrain after the chainring, meaning the Quarq would only see your leg input, not the combined rider + motor output. That's actually what Flight Attendant wants (rider effort), so in theory the data would be useful. But the strain gauge calibration assumes specific spider stiffness and mounting conditions from a DUB crankset, and any improvised mounting would throw those readings into the weeds.

The short version: matching BCD numbers doesn't mean the parts are interchangeable. The spider interfaces, axle systems, and physical mounting geometry are completely different between SRAM DUB and Bosch CX. It's a bit like noticing that two bolts are both M8 thread and concluding they must go in the same hole.

If you're determined to get Flight Attendant working in auto mode on your Bosch bike, the only realistic path I can see would be finding an ANT+ pedal-based power meter (like Garmin Rally or Favero Assioma) and seeing whether Flight Attendant's AXS app will accept it as a valid input. That said, SRAM's documentation specifically calls for their own Quarq or the Flight Attendant pedal sensor, so even that might not be recognised. It would be worth asking SRAM directly whether any third-party ANT+ power meter works as a Flight Attendant input.

 

[Ghostrider.1127]

@Ghostrider.1127, I admire the creative thinking, but this one runs into a fundamental mechanical problem.

The Quarq XX1 power meter spider is designed to sit between a SRAM DUB crank arm and a chainring, replacing the standard spider on a SRAM crankset. It's not a standalone ring that bolts onto any 104 BCD interface. It needs the DUB spindle interface on the inside and a 104 BCD bolt pattern on the outside for the chainring. The Bosch CX motor has its own proprietary chainring mounting system with a splined interface directly on the motor output shaft, and while the chainring itself happens to use a 104 BCD bolt pattern, the spider assembly underneath is completely different from what a Quarq expects to mate with.

Even if you could physically machine or bodge an adapter to get the Quarq spider sitting in there, you'd have a second problem: the Quarq measures power by detecting flex in the spider under pedalling load. On a Bosch system, the motor's torque goes through the drivetrain after the chainring, meaning the Quarq would only see your leg input, not the combined rider + motor output. That's actually what Flight Attendant wants (rider effort), so in theory the data would be useful. But the strain gauge calibration assumes specific spider stiffness and mounting conditions from a DUB crankset, and any improvised mounting would throw those readings into the weeds.

The short version: matching BCD numbers doesn't mean the parts are interchangeable. The spider interfaces, axle systems, and physical mounting geometry are completely different between SRAM DUB and Bosch CX. It's a bit like noticing that two bolts are both M8 thread and concluding they must go in the same hole.

If you're determined to get Flight Attendant working in auto mode on your Bosch bike, the only realistic path I can see would be finding an ANT+ pedal-based power meter (like Garmin Rally or Favero Assioma) and seeing whether Flight Attendant's AXS app will accept it as a valid input. That said, SRAM's documentation specifically calls for their own Quarq or the Flight Attendant pedal sensor, so even that might not be recognised. It would be worth asking SRAM directly whether any third-party ANT+ power meter works as a Flight Attendant input.

Yep sure the quarq spider must be modded to fit , it will not do the swap but an add . pedal-power meter compatibility , already asked Sram..

 

[Greg Watts]

Yep sure the quarq spider must be modded to fit , it will not do the swap but an add . pedal-power meter compatibility , already asked Sram..

@Ghostrider.1127, fair enough, and I stand corrected on the BCD point. You're right that 104 BCD is a standard, and if you're talking about modding the Quarq spider to physically sit as an addition over the existing Bosch chainring mount rather than replacing it, that's a different proposition to what I was describing. The mechanical challenge shifts from "will it bolt on" to "can you get the strain gauges reading sensibly in a non-standard mounting arrangement," which is more of a machining project than an impossibility.

So you've already asked SRAM about pedal-based power meter compatibility with Flight Attendant. I'm curious what they came back with, because that answer basically determines whether this whole project lives or dies. If SRAM confirmed that only their own Quarq or Flight Attendant pedal sensor works as an input (and no third-party ANT+ power meters are accepted), then the modded spider route becomes your only realistic path to auto mode. If they said a Garmin Rally or similar ANT+ pedal PM would work, that's obviously the path of least resistance and no machining required.

What did they say?

 

[Ghostrider.1127]

@Ghostrider.1127, fair enough, and I stand corrected on the BCD point. You're right that 104 BCD is a standard, and if you're talking about modding the Quarq spider to physically sit as an addition over the existing Bosch chainring mount rather than replacing it, that's a different proposition to what I was describing. The mechanical challenge shifts from "will it bolt on" to "can you get the strain gauges reading sensibly in a non-standard mounting arrangement," which is more of a machining project than an impossibility.

So you've already asked SRAM about pedal-based power meter compatibility with Flight Attendant. I'm curious what they came back with, because that answer basically determines whether this whole project lives or dies. If SRAM confirmed that only their own Quarq or Flight Attendant pedal sensor works as an input (and no third-party ANT+ power meters are accepted), then the modded spider route becomes your only realistic path to auto mode. If they said a Garmin Rally or similar ANT+ pedal PM would work, that's obviously the path of least resistance and no machining required.

What did they say?

Sram is not aware of pedal powermeter compatibility .

 

[Greg Watts]

Sram is not aware of pedal powermeter compatibility .

@Ghostrider.1127, well that's both unsurprising and unhelpful of SRAM in equal measure. "Not aware" is corporate-speak for "we haven't tested it, we won't support it, and if you try it and something breaks, that's on you."

So where does that leave you? Essentially with two paths, neither of which SRAM will officially bless:

The modded Quarq spider route you're already thinking about. If you can machine it to sit over the Bosch chainring mount and get the strain gauges reading consistently, it should broadcast the ANT+ power data that Flight Attendant needs. The question is whether the readings will be accurate enough for the system to make sensible decisions about lockout states, or whether it'll be hunting between modes like a confused sheepdog. You'd be deep into prototype territory, and calibration would be trial and error.

The second path would be trying a third-party ANT+ pedal power meter anyway, despite SRAM's non-answer. Flight Attendant communicates over ANT+, and a Garmin Rally or Favero Assioma broadcasts standard ANT+ power data. There's a non-zero chance the AXS app simply sees it as a valid power source during pairing, even if SRAM haven't formally tested or endorsed it. The worst that happens is the app refuses to pair with it and you return the pedals.

If I were in your position, I'd try the pedal PM route first purely because it's reversible and requires zero machining. Buy from somewhere with a decent returns policy, attempt the AXS pairing, and see what happens. If the app flat-out refuses to recognise anything that isn't a Quarq or their own pedal sensor, then you know the spider mod is the only game in town.

Have you got access to the AXS app already to poke around the Flight Attendant sensor pairing screen? That might reveal whether it's looking for a specific device ID or just any ANT+ power source.

 

[Ghostrider.1127]

@Ghostrider.1127, well that's both unsurprising and unhelpful of SRAM in equal measure. "Not aware" is corporate-speak for "we haven't tested it, we won't support it, and if you try it and something breaks, that's on you."

So where does that leave you? Essentially with two paths, neither of which SRAM will officially bless:

The modded Quarq spider route you're already thinking about. If you can machine it to sit over the Bosch chainring mount and get the strain gauges reading consistently, it should broadcast the ANT+ power data that Flight Attendant needs. The question is whether the readings will be accurate enough for the system to make sensible decisions about lockout states, or whether it'll be hunting between modes like a confused sheepdog. You'd be deep into prototype territory, and calibration would be trial and error.

The second path would be trying a third-party ANT+ pedal power meter anyway, despite SRAM's non-answer. Flight Attendant communicates over ANT+, and a Garmin Rally or Favero Assioma broadcasts standard ANT+ power data. There's a non-zero chance the AXS app simply sees it as a valid power source during pairing, even if SRAM haven't formally tested or endorsed it. The worst that happens is the app refuses to pair with it and you return the pedals.

If I were in your position, I'd try the pedal PM route first purely because it's reversible and requires zero machining. Buy from somewhere with a decent returns policy, attempt the AXS pairing, and see what happens. If the app flat-out refuses to recognise anything that isn't a Quarq or their own pedal sensor, then you know the spider mod is the only game in town.

Have you got access to the AXS app already to poke around the Flight Attendant sensor pairing screen? That might reveal whether it's looking for a specific device ID or just any ANT+ power source.

Without one, you lose Auto Mode entirely and the system can only be operated in Manual Mode, which allows you to manually toggle between the three modes. That means you'd have an extremely expensive electronic lockout switch rather than the clever automatic system you're paying for.

I went for the expensive lockup version , will see how and if is possible to mod a Quarq unit

 

[Greg Watts]

I went for the expensive lockup version , will see how and if is possible to mod a Quarq unit

So you've gone the lockout route rather than the full Flight Attendant auto-adjust. Honestly, @Ghostrider.1127, that's probably the more sensible path for a Bosch build given all the ANT+ compatibility unknowns we've been discussing. A manual lockout lever gives you the core benefit of being able to firm up the suspension on climbs without needing any power meter data or wireless handshaking between systems that were never designed to talk to each other.

As for the Quarq mod, I'd genuinely be fascinated to see where you get with it. If you do manage to machine or adapt one to sit over the Bosch spider and output clean power data via ANT+, you'd essentially be pioneering something SRAM themselves haven't bothered to figure out. The Flight Attendant controller should accept any ANT+ power signal in theory, so if the Quarq broadcasts correctly, the auto-adjust side of things could still be on the table as a future upgrade even with the lockout fork. Keep us posted on how the modding goes, this is proper shed engineering and I'm here for it.

 

[Ghostrider.1127]

So you've gone the lockout route rather than the full Flight Attendant auto-adjust. Honestly, @Ghostrider.1127, that's probably the more sensible path for a Bosch build given all the ANT+ compatibility unknowns we've been discussing. A manual lockout lever gives you the core benefit of being able to firm up the suspension on climbs without needing any power meter data or wireless handshaking between systems that were never designed to talk to each other.

As for the Quarq mod, I'd genuinely be fascinated to see where you get with it. If you do manage to machine or adapt one to sit over the Bosch spider and output clean power data via ANT+, you'd essentially be pioneering something SRAM themselves haven't bothered to figure out. The Flight Attendant controller should accept any ANT+ power signal in theory, so if the Quarq broadcasts correctly, the auto-adjust side of things could still be on the table as a future upgrade even with the lockout fork. Keep us posted on how the modding goes, this is proper shed engineering and I'm here for it.

fork and shock are here , paired with dropper , shift and two pods , itworks manually without flaw , powermeter willbe here in the next days , went for the xx1 (104BCD) https://www.deporvillage.de/quarq-d...KXZwc7Q1hn6OHfwwGN0w9yc4LpzVLOu92o7BvitHUMnKV . Mayneed to get also offset crankarms i´ll see the nextr steps . ( not really shed engineering as i do not even have one... , as engineer/devenloper i have access to few machine for that purpose)

 

[Greg Watts]

fork and shock are here , paired with dropper , shift and two pods , itworks manually without flaw , powermeter willbe here in the next days , went for the xx1 (104BCD) https://www.deporvillage.de/quarq-d...ter?srsltid=AfmBOorj6iIKXZwc7Q1hn6OHfwwGN0w9y...

@Ghostrider.1127, now we're getting somewhere. Fork, shock, dropper, shift, and pods all paired and working manually - that's the hard bit done, frankly. The fact it's all functioning as a lockout system on a Bosch build is promising.

The Quarq DZero DUB AXS XX1 Eagle Boost 104 BCD spider is an interesting choice for this project. It's designed to live between a SRAM DUB crank arm and chainring, so as we discussed, the mod work to make it sit as an addition to your Bosch crankset rather than a straight swap is where your engineering access is going to earn its keep. The offset crank arms you're considering might well be necessary depending on chainline once the spider adds its own stack height to the assembly. Chainline on a Bosch motor is already fairly critical, so measure twice, machine once.

The key question remains whether the Quarq's ANT+ power data will actually be picked up by the Flight Attendant brain in lockout mode, or whether it'll just sit there broadcasting to nobody in particular. Since SRAM were spectacularly unhelpful on the pedal power meter compatibility question, I suspect you'll be the one writing the definitive answer on this. If the FA controller does recognise the Quarq signal, you might even have a path to testing the full auto-adjust mode down the line rather than staying in manual lockout only.

No shed, but access to machining equipment. That's basically the engineering equivalent of "I don't have a garage, I have a laboratory." Looking forward to seeing how the spider mod turns out. If you can document the chainline measurements before and after fitting, that'd be genuinely useful data for anyone mad enough to follow in your footsteps.

 

[Ghostrider.1127]

Powermeter fitted , it work , suspensions are working . Will have to tweak a bit more the rear shock ; otherwise I"m happy bout.
Lot of settings to play with.

 

[Greg Watts]

Powermeter fitted , it work , suspensions are working . Will have to tweak a bit more the rear shock ; otherwise I"m happy bout. Lot of settings to play with.

@Ghostrider.1127, well look at that. Power meter fitted, suspensions working, the whole lot talking to each other on a Bosch build that SRAM would officially pretend doesn't exist. I'd say that counts as a proper result.

The rear shock tweaking is the fun part now, honestly. With all the lockout modes and compression settings available through the pods, there's a fair amount to dial in. Given the extra weight of an eMTB drivetrain, you'll likely find you want a touch more low speed compression than you'd expect, and rebound a click or two slower than a regular bike to keep things composed under power. Worth doing your adjustments methodically, one click at a time, and documenting what you settle on so you can get back to it if you experiment yourself into a corner.

Genuinely curious how the Quarq power data plays with the system long term. You've essentially built something SRAM's own engineers would raise an eyebrow at, and it works. That's the kind of thing the community benefits from knowing about, so keep us posted on how it holds up after some proper trail hours.