Front Derailleur to guide chain or not?

[MWRider]

I had read that the chain can / will jump off of the chainring. It was suggested that the front derailleur be kept in place as a chain guide. I did this on my wife’s Ebike kit build by adding an adjustable cable stop mounted on the seat post tube. Do not know if this is needed. What do you think?

 

[fauconnier]

IMO If you chain line is not over crooked and your hub doesn't exceed 9 gears, you don't need it.

 

[MWRider]

IMO If you chain line is not over crooked and your hub doesn't exceed 9 gears, you don't need it.

Thanks for the reply! That is what I am thinking.

 

[prestoOne]

It is a chain guide. If she is riding nicely paved areas and her chain is good then it will all be good. No harm in leaving it on either.

 

[MWRider]

@Rome, Thanks! I just figured that since it was already there and that I could not find my chain breaker, I would leave it on and utilize it. Especially, since the first one is my wife’s bike and she is not so good on shifting etiquette. Since I put together the Ebike, she likes riding. Hills used to slow her down a lot. $890 for the kit and the battery. Already had the bike and wanted to keep it reversable in case she did not like it.

 

[linklemming]

@Rome, Thanks! I just figured that since it was already there and that I could not find my chain breaker, I would leave it on and utilize it. Especially, since the first one is my wife’s bike and she is not so good on shifting etiquette. Since I put together the Ebike, she likes riding. Hills used to slow her down a lot. $890 for the kit and the battery. Already had the bike and wanted to keep it reversable in case she did not like it.

Good idea and cost nothing to leave it. Im a little OCD with my bike builds and in the situation where it applies have used the following instead of the derailler:
https://www.amazon.com/gp/product/B008ZTLV9W/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I also use narrow/wide chainrings and/or clutched deraillers where appropriate.

You can drop a chain under many circumstances with your chain straight and with less than 9 speeds in the rear.

They make chainguides for a reason

 

[linklemming]

Biktrix says they never had chain dropped out of their test bike and production bikes.
The chain dropped out of my bike when I was on the biggest gear on the cassette, because of the mud gaurd that I installed. It is true because I heard a raucous and at that time I thought my bike was falling apart. I notch the fender and it's alright now. I just rode 17 miles literally trying to make it fail .
So on my bike it's not required.
But I still think it should have one as standard equipment regardless.

Your first pic seems to show a narrow/wide chainring which helps to alleviate chain drop. I have two ebikes with narrow/wide chainrings which have never had the chain drop (I did get chaindrop on one before going to the narrow/wide chainring, it took about 4k miles to happen).

 

[linklemming]

Simply typing 'narrow wide chainring' into google gave the following (amongst many others)

https://www.worldwidecyclery.com/blogs/worldwide-cyclery-blog/narrow-wide-chainrings-guide