Brake Cut Off - do I need it?

[Kendalian]

I am currently fitting a rear hub drive conversion kit which came with brake levers to cut off the power. Do I really need them? My Bosch powered bike doesn't have them so are they really necessary??
Many Thanks

Kendalian

 

[Benjahmin]

If your kit has a throttle, then yes as there is a possibility of a throttle fault that gives you full power. Of course you can fit the kit without the throttle, up to you, but I find it useful for hill starts.
The other place I find the brake cut off useful is approaching a junction. I need to change down gears (so rotating pedals) but don't want the power.
On some systems the power continues for a short while after you stop pedalling. Remember this will be pas not torque sense, they behave differently.
Other than that - no.

 

[Nealh]

Hub kits use different controller software and can be sensitive with pas. Depends on the makers software and if a throttle is used.
Brake sensors have twice saved me from a damaged controller due to wire and moisture issues causing a surge in power when unwanted. Only one is needed to allow instant cut in power

 

[awol]

I like to have at least one for the reasons already mentioned above. If you have cable brakes and don't want to change your levers you could try one or two of these inline HWBS sensors (asuming your controller will take 3wire brake cutoffs)

https://www.ebay.co.uk/itm/1-PCS-HWBS-Hidden-Wire-Brake-Sensor-for-E-Bike/332586353476?hash=item4d6fb10344:g:EBEAAOSwAwFapz60

 

[anotherkiwi]

Never needed one with a hub motor, wouldn't be without with a crank drive.

 

[Kendalian]

Thanks for the replies guys - even more unsure now since anotherkiwi has given the opposite view to everyone else!

Kendalian

 

[Fordulike]

I would always fit a brake cut-off to the brake which has the motor. Front cut-off for front hub, rear for rear hub, rear for mid/crank drive.

 

[Nealh]

Thanks for the replies guys - even more unsure now since anotherkiwi has given the opposite view to everyone else!

Kendalian

Mostly you don't really need one, if you have no throttle fitted.
They are generally quite easy to fit and having one fitted will save your controller or hub from damage should a wire or other fault occur.

Two faults that occurred to me on different bikes both throttle related.
An intermittent wire contact on the throttle, this led to bike rearing up due to a broke wire. Brake cut off stopped motor dead by cutting power from controller.
Wire fault traced and repaired and all ok.

Julet showed moisture ingress with oxidising tract between two copper pins causing power surge from throttle with out manual operation, again brake cut off cut power from controller.

In both cases with no cut offs applying brake would stop the bike but would not cut power to the controller, this in turn would either cause mosfet or other controller damage and even cause hub damage due to unregulated power surge.

 

[Kendalian]

Looks like fitting them is the best way to go then.

Many Thanks all

Kendalian

 

[Richardab]

Simple really, if you use a throttle then yes, if you only have PAS then they are not really required. I use PAS only and don't have them

 

[anotherkiwi]

Thanks for the replies guys - even more unsure now since anotherkiwi has given the opposite view to everyone else!

Kendalian

I have never mounted a throttle. On a mid-drive you have motor run-on when you stop pedaling which is why one is required even without a throttle. Both bikes using similar KT controllers and PAS cuts off power immediately on the hub motor.

 

[KirstinS]

Never needed one with a hub motor, wouldn't be without with a crank drive.

Don't shoot me.....but I have the exact opposite view ! A bbsxx programmed correctly needs it less than a hub system with a throttle and crappy magnet pas (often with looong run on after pedalling ceases)

My bbs is instant , my GSM not so much though


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[KirstinS]

I have never mounted a throttle. On a mid-drive you have motor run-on when you stop pedaling which is why one is required even without a throttle. Both bikes using similar KT controllers and PAS cuts off power immediately on the hub motor.

Perhaps it depends Anotherkiwi ? As said before my bbsxx programmed is instant but my unprogrammable gsm does run on


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[Paultr]

Glad I have read this thread as much against the advice from Woosh I have not got around to fitting my hydraulic sensors. This is using a hub drive and throttle. In general use I have never felt the need for them but I definitely don't want to lose my throttle as I find it frequently invaluable when starting off but haven't considered it misbehaving.
Going to fit them now.

 

[Nealh]

You only need to fit one brake sensor.

 

[Paultr]

You only need to fit one brake sensor.

Going to put it on the rear disk lever then. Not only is my motor there but I always apply the rear brake instinctively just before the front having learnt the hard way what happens if you slam the front brake on when riding a racing bike when I was probably 14 or so. You only do it once

 

[harrys]

A lot depends on your pedal assist behavior. My cadence sensors need a brake cutoff, especially doing a slow turn-around. Unless I turn off pedal assist before the maneuver or have a brake cutoff, my motor starts up. Not good in a crowd.

I've also had a throttle fault. It was just my Q100 on a 20" wheel, so it wouldn't have gone faster than 18 mph, but the point was I had a cutoff. My bigger bike with 52V would have pulled 1200 watts. (By the way, if your ground wire comes off your throttle harness, most controllers will go wide open.)

 

[Kendalian]

Once again many thanks for all the replies - as it is the wife's I am definitely going to fit them, don't really want a bollocking if things go wrong at some point in the future!

Cheers

Kendalian

 

[Kendalian]

Thanks to Tony at Woosh I have ironed out all the issues with fitting the kit - most problematic was the pedal sensor/magnet ring combination. With hindsight it would have been much simpler to replace the bottom bracket to enable the simpler left pedal sensor to be fitted. I fitted both brake levers with cut off as recommended by most on here. The rear hub motor is amazing - it really takes off in max assist - better than my Bosch centre drive bike! The main thing is the wife is happy!!

The instructions for the King Meter leave a bit to be desired - specifically how do you get it to show the speed and distance units in mph or kph? Mine shows no units at all. Also how do you switch between k and m?

Cheers

Kendalian

 

[Woosh]

Also how do you switch between k and m?

we reprogrammed the LCD to show speed in MPH.
The code turns off / removes the KM/H symbol at the bottom right corner of the LCD.
The speed limit is still set as 25KM/H which is 15.5 Miles/H
All the other functions are in the manual:

http://wooshbikes.co.uk/manuals/KM-529-LCD-Display.pdf