Anything can be used as a weapon..... flashlight,tire pump,bike chain,
bike lock,a wheel skewer,your bike.

And I'd carry pepper spray and/or small knife wether it was legal or not.
An attacker will most likely have a record already and what are they going to say?
"Well officer,after I tried knocking him off his bike,he sprayed me."

We have a saying over here.....
"I'd rather be judged by 12 than carried by 6"
Just be careful, Weapons can be taken from you and used against you.
A self defense class is always a good idea.
it's getting crazy out there.

JM