Problems with drivetrain and the BBS01, need advice.

[SkipperDK]

Hi guys,

I'm having problem with my drivetrain. I'm using a citybike with a 8-speed 32-11 casette and a 46t in front.

I do a daily commute of 20miles and i like using PAS, this means i'm running mainly in the 46-11 gearing at about 500watts + my own pedaling. My problem is, that i'm pulling the 11t sprocket to shreads way to fast, I only get about 100-200 miles before et starts skipping the chain.

I always shift gear at high cadence and I also use a shiftsensor.
I do keep it very clean and change both chain and casette when replacing, nevertheless, it starts skipping fast.

Any of you masterminds of ES that have any great suggenstions as to overcome this problem?

Thanks in advance, guys

 

[Balmorhea]

You're pedaling at too low a speed. The motor is operating in its high torque/low efficiency range. This is bad for your motor due to added heat, bad for your gears due to added wear, and bad for your range due to inefficiency.

11t sprockets barely work for pedal bikes. The main reason they are acceptable is because they are used so little of the time when the bike is shifted correctly. The best policy for 11t sprockets is don't use them. They wear and wreck your chain, which in turn wrecks the rest of your gears.

You can't only replace the worn sprocket, because it will have transferred that wear to the chain. You have to replace both.

However fast the chainring turns when the motor is running and the rear wheel is off the ground, the ideal steady state pedaling speed is about 80% of that. If you can't pedal that fast, or don't want to, then pedal as fast as you can. Everything will work better, and you won't have to use the 11t sprocket.

 

[SkipperDK]

Thank you for a very good reply. I'm keeping as high a cadance as possible, it's just about 80-90rpm, so i'm thinking tur cadance is alright, but you're right, perhaps its just to much torque for the 11t sprocket.

Should i go for a bigger front ring instead?

 

[Balmorhea]

Should i go for a bigger front ring instead?

Yes. 52t is easy and cheap to get, and it means a 13t sprocket will do the job.

13t second position sprockets can be bought separately, so keep a couple on hand.

 

[SkipperDK]

Thats a great suggestion, i'll give that configuration a go next week.

Thank you, mate.