Identical bikes, different top speeds

stjotosv

10 µW
Joined
Jun 13, 2022
Messages
5
Hello. A customer came into my workshop today with two identical bikes . One is almost unused and in perfect condition and the other one has been in the river a few times and sees daily abuse by their son. The beat up one does 39km/h and the almost unused one does 31km/h . All display settings are identical . Swapping the batteries does not affect anything. No bad sounds coming from the hub motor .

Can ebike controllers or hub motors be affected by the "silicone lottery"? My next step is to inspect the controllers and maybe try swapping the controllers to see if the problem follows the controller. The controllers are of unknown origin and the rear hub motors are made by Bafang
sykkel.1024x682!m.png
 
The first thing: did both bikes *originally* run at the same top speed? (you'll have to trust the customer's word on that one, since I assume you've never seen them when both were in good condition).

Water damage can cause all sorts of issues; virtually nothing is actually waterproof on ebikes.

Additionally, crash damage can also cause all sorts of issues; wire damage from this is very common at exposed areas of cabling (axle exit of motor especially).

If there is a throttle, it could have either water damage or physical damage preventing it from outputting it's full voltage. Is the voltage range of the signal the same on both bikes?

If it has PAS-only, is it torque control, or only cadence/on-off (with assist amount controled by a level chosen via the display)? If it's torque control, the sensor (in the axle for the cranks, usually), it could have water or impact damage causing less output than it should have.

There could simply be water ingress in the connectors or cabling, or the controller housing, with corrosion causing undesired or insufficient operation.

Could even be at the battery connector on the bike itself, either where the battery mates with it, or where the wires enter the back; this would show a voltage drop at the controller under load vs with no load.

The motor could have water damage in it, but usually this is either a complete failure or normal operation, or something obvious like being unable to turn the motor by hand, or taking a lot of force to do so (and this would also cause the ocntroller and battery to use a lot more power than normal to drive the motor, causing more heating and less range , boht usually significant).



stjotosv said:
Hello. A customer came into my workshop today with two identical bikes . One is almost unused and in perfect condition and the other one has been in the river a few times and sees daily abuse by their son. The beat up one does 39km/h and the almost unused one does 31km/h . All display settings are identical . Swapping the batteries does not affect anything. No bad sounds coming from the hub motor .

Can ebike controllers or hub motors be affected by the "silicone lottery"? My next step is to inspect the controllers and maybe try swapping the controllers to see if the problem follows the controller. The controllers are of unknown origin and the rear hub motors are made by Bafang
sykkel.1024x682!m.png
 
Thank you for your reply. If it was the bike that's been in water that's misbehaving it would have made things alot easier but it's the bike that looks brand new that's not working as it should. I don't think it's ever seen a raindrop. The beat up bike is behaving as it should. (Top speed is 40km/h according to the shop it's from). All external contacts and wires on the new(but slow) bike looks brand new .

The customer thinks it has been like this from the beginning but wasn't quite sure. He almost never uses the throttle and the PAS gets signals from 4 magnets on the bottom bracket.

I will inspect battery contact and controller contacts tomorrow when the customer returns with the bike so i can take a deeper look at it.

amberwolf said:
The first thing: did both bikes *originally* run at the same top speed? (you'll have to trust the customer's word on that one, since I assume you've never seen them when both were in good condition).

Water damage can cause all sorts of issues; virtually nothing is actually waterproof on ebikes.

Additionally, crash damage can also cause all sorts of issues; wire damage from this is very common at exposed areas of cabling (axle exit of motor especially).

If there is a throttle, it could have either water damage or physical damage preventing it from outputting it's full voltage. Is the voltage range of the signal the same on both bikes?

If it has PAS-only, is it torque control, or only cadence/on-off (with assist amount controled by a level chosen via the display)? If it's torque control, the sensor (in the axle for the cranks, usually), it could have water or impact damage causing less output than it should have.

There could simply be water ingress in the connectors or cabling, or the controller housing, with corrosion causing undesired or insufficient operation.

Could even be at the battery connector on the bike itself, either where the battery mates with it, or where the wires enter the back; this would show a voltage drop at the controller under load vs with no load.

The motor could have water damage in it, but usually this is either a complete failure or normal operation, or something obvious like being unable to turn the motor by hand, or taking a lot of force to do so (and this would also cause the ocntroller and battery to use a lot more power than normal to drive the motor, causing more heating and less range , boht usually significant).



stjotosv said:
Hello. A customer came into my workshop today with two identical bikes . One is almost unused and in perfect condition and the other one has been in the river a few times and sees daily abuse by their son. The beat up one does 39km/h and the almost unused one does 31km/h . All display settings are identical . Swapping the batteries does not affect anything. No bad sounds coming from the hub motor .

Can ebike controllers or hub motors be affected by the "silicone lottery"? My next step is to inspect the controllers and maybe try swapping the controllers to see if the problem follows the controller. The controllers are of unknown origin and the rear hub motors are made by Bafang
sykkel.1024x682!m.png
 
stjotosv said:
Thank you for your reply. If it was the bike that's been in water that's misbehaving it would have made things alot easier but it's the bike that looks brand new that's not working as it should. I don't think it's ever seen a raindrop. The beat up bike is behaving as it should. (Top speed is 40km/h according to the shop it's from). All external contacts and wires on the new(but slow) bike looks brand new .

Sorry, somehow I missed that. :oops:

I'd still check for cabling / connection issues on the misbehaving bike, including for the battery cradle. (if i does'nt matter which battery is on there, that means it shouldn't be caused by the battery itself).

If max speed via throttle is the same as speed via PAS, then it's not a "control" problem, but could be a speed sensor problem (misreported overspeed to controller results in lowering controller output to drop speed), etc.
 
The plot thickens . Customer has used bearing grease on the battery and other contacts. I think that may harm conductivity i always use electric component silicon based grease for corrosion protection. Speed is same with PAS and throttle and speed limit is set to 99kmh. Could the speed sensor sense over 99kmh when in reality he is going 30 kmh?


amberwolf said:
stjotosv said:
Thank you for your reply. If it was the bike that's been in water that's misbehaving it would have made things alot easier but it's the bike that looks brand new that's not working as it should. I don't think it's ever seen a raindrop. The beat up bike is behaving as it should. (Top speed is 40km/h according to the shop it's from). All external contacts and wires on the new(but slow) bike looks brand new .

Sorry, somehow I missed that. :oops:

I'd still check for cabling / connection issues on the misbehaving bike, including for the battery cradle. (if i does'nt matter which battery is on there, that means it shouldn't be caused by the battery itself).

If max speed via throttle is the same as speed via PAS, then it's not a "control" problem, but could be a speed sensor problem (misreported overspeed to controller results in lowering controller output to drop speed), etc.
 
Different tire pressures (one bike vs. the other) could do something like that. Dragging brakes or tight wheel bearings might also be considered.
 
Thank you for your reply. That's the first thing I'm going to check next time he comes by because he is really avoiding tire pressure related questions when asked . Also checking front wheel bearings. Rear seemed fine.

AHicks said:
Different tire pressures (one bike vs. the other) could do something like that. Dragging brakes or tight wheel bearings might also be considered.
 
stjotosv said:
Thank you for your reply. That's the first thing I'm going to check next time he comes by because he is really avoiding tire pressure related questions when asked . Also checking front wheel bearings. Rear seemed fine.

AHicks said:
Different tire pressures (one bike vs. the other) could do something like that. Dragging brakes or tight wheel bearings might also be considered.

Maybe introduce him to a sealant for his inner tubes? That way he can set it and forget it for months....
 
Have you got both bikes in the shop? Did you do amberwolf's suggestion of checking the no-load speed. Wheel off the ground, Flip the throttle. They should match. Also check the throttle voltages to make sure they both reach the same level.

If the no load speeds don't match, no need to swap motors. Just open the motor connectors and swap them. See if speed travels with the motor.
 
Thank you for your reply. I would love to do this but after i mentioned tire pressure and how it affects fat bike speed he fell off the face of the earth and i have not heard from him since. I can only guess that it may have been related to tire pressure .

docw009 said:
Have you got both bikes in the shop? Did you do amberwolf's suggestion of checking the no-load speed. Wheel off the ground, Flip the throttle. They should match. Also check the throttle voltages to make sure they both reach the same level.

If the no load speeds don't match, no need to swap motors. Just open the motor connectors and swap them. See if speed travels with the motor.
 
AHicks said:
Maybe introduce him to a sealant for his inner tubes? That way he can set it and forget it for months....

No. Forget your tubeless sealant for even a few weeks and it will coagulate into lumps in the low spots of the tires.

There are reasons to favor tubeless, but it will always squander more of your time on your tires than if you went for something less faddish.
 
Chalo said:
AHicks said:
Maybe introduce him to a sealant for his inner tubes? That way he can set it and forget it for months....

No. Forget your tubeless sealant for even a few weeks and it will coagulate into lumps in the low spots of the tires.

There are reasons to favor tubeless, but it will always squander more of your time on your tires than if you went for something less faddish.

Speaking of CONVENTIONAL TUBE TYPE TIRES, running sealant in the tubes is an excellent plan that's I've been using for quite some time. Early on (analog bikes) it was because I was tired of the need to constantly check and air up my tires to maintain them at my favored 65psi. Today (e-bikes), I'm running wider tires at lower pressure, but running sealant for the same reason, as well as pretty much eliminating flats.

I'd say what brand I prefer, but I don't want to hear some butt head call me a fan boy. I would endorse some due diligence, but you don't need to get carried away regarding the brand. The worst available, IMHO, is better than nothing.....
 
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