Installing larger chain ring on a gen 4 motor

[Deacon Blues]

I'd like to install a larger chain ring on my ebike, with a Bosch gen 4 motor, but the bike shop says that it's more complicated than just installing the larger chain ring and adding a new longer chain, or adding links to the old chain. They said the motor had to be adjusted somehow.
The shop, where I bought the ebike, usually sells high-end road bikes and have limited experience with ebikes.

Has anyone here put a larger chain ring on their Bosch motor? @Ravi can you give me your opinion on this?

 

[rich c]

Why the larger chainring? Are you pedaling out before hitting the high limit? That's not been an issue for me.

 

[Deacon Blues]

I'm finding that I often ride with the cassette in the smallest or next smallest cog. On the flats I'm okay, but on a slight downhill grade I often run out of gears (and I'm way past the motor cut-off).
I ride a Cannondale Topstone Neo Lefty 3, which has a 42T chain ring and an 11to 42 cassette. The Lefty 1 (more expensive model) has a 46T chain ring, with a 10 to 50 cassette.
I want to replace my 42T chain ring with the 46T chain ring found on the Lefty 1. I figure it should be an easy swap.

 

[fooferdoggie]

Humm I wonder maybe ask one of the bosch guys here to see. I know I put a smaller one on mine I had just the opposite problem I could peddle to about 35 mph. so I put a smaller one on but mine is the second j=gen with the small chainrings.

 

[Ravi Kempaiah]

I ride a Cannondale Topstone Neo Lefty 3, which has a 42T chain ring and an 11to 42 cassette.

Bosch system is programmed for very smooth power delivery and also shift sensing. So, it requires OEMs to input the drivetrain ratio into the system.
The shift sensing works differently for derailleur vs IGH systems. On an automatic IGH like the E-14 or Enviolo automatiq, it is a bit more subtle and reduces the power when the cranks are in 6'clock position to allow for more smoother shift.

If you go from 40 to 48T, you might encounter an error code because the ratios are getting messed up but within a certain range, you could do it. Since the left 1 has 46T and 10-50T cassette, ask them to look at the gearing ratio used in the system and then reprogram yours to that ratio. Then you will be able to use the same drivetrain that is on the Lefty 1.

 

[Deacon Blues]

Thanks for the reply, Ravi.

 

[Ravi Kempaiah]

Thanks for the reply, Ravi.

Happy to help. Hope it works out.
Your shop is right and your motor would need minor adjustment in the gearing ratio.

 

[markybolton]

Bosch system is programmed for very smooth power delivery and also shift sensing. So, it requires OEMs to input the drivetrain ratio into the system.
The shift sensing works differently for derailleur vs IGH systems. On an automatic IGH like the E-14 or Enviolo automatiq, it is a bit more subtle and reduces the power when the cranks are in 6'clock position to allow for more smoother shift.

If you go from 40 to 48T, you might encounter an error code because the ratios are getting messed up but within a certain range, you could do it. Since the left 1 has 46T and 10-50T cassette, ask them to look at the gearing ratio used in the system and then reprogram yours to that ratio. Then you will be able to use the same drivetrain that is on the Lefty 1.

I have the Domane+ HP with a 11-42t and 46T, can I do the same gear without too much problems? I would like the 10-50T plus the larger chain ring!

 

[gadgetguy]

I have a Gazelle Medeo T10+. The bike came with a 55T front chainring and 11-42T in the rear. Motor is gen 4. Tires are 28 x 2.0. So that arrangement does work with the Bosch system and it works well. Can't comment on how it was programmed since this is how the factory delivered the bike. Very little space between the chainring and the frame.

 

[markybolton]

I have a Gazelle Medeo T10+. The bike came with a 55T front chainring and 11-42T in the rear. Motor is gen 4. Tires are 28 x 2.0. So that arrangement does work with the Bosch system and it works well. Can't comment on how it was programmed since this is how the factory delivered the bike. Very little space between the chainring and the frame.

Not a 55T on the front but a 48T

 

[gadgetguy]

Not a 55T on the front but a 48T

The chainring is stamped 52T. It is larger than 48T. Have not counted the teeth. I got 55 from Gazelle's website.

 

[Alaskan]

I'd like to install a larger chain ring on my ebike, with a Bosch gen 4 motor, but the bike shop says that it's more complicated than just installing the larger chain ring and adding a new longer chain, or adding links to the old chain. They said the motor had to be adjusted somehow.
The shop, where I bought the ebike, usually sells high-end road bikes and have limited experience with ebikes.

Has anyone here put a larger chain ring on their Bosch motor? @Ravi can you give me your opinion on this?

Have you had any luck sourcing the 46 tooth chainring for your Neo 3. I am interested in doing the same but having a hard time finding one.

 

[bob armani]

I'm finding that I often ride with the cassette in the smallest or next smallest cog. On the flats I'm okay, but on a slight downhill grade I often run out of gears (and I'm way past the motor cut-off).
I ride a Cannondale Topstone Neo Lefty 3, which has a 42T chain ring and an 11to 42 cassette. The Lefty 1 (more expensive model) has a 46T chain ring, with a 10 to 50 cassette.
I want to replace my 42T chain ring with the 46T chain ring found on the Lefty 1. I figure it should be an easy swap.

Yup, that's exactly the way I ride on the last 2 cogs. They certainly wear out first and have to be mindful when that happens on a 2 year old E-bike thus far.

 

[Deacon Blues]

Have you had any luck sourcing the 46 tooth chainring for your Neo 3. I am interested in doing the same but having a hard time finding one.

I was going to call the shop where I bought the bike from. Since Cannondale offers the larger ring on the Lefty 1 I should hope they can ship one to my dealer. I'd also like to find out if there is a rear fender available for this bike. I have a MTB rear fender, which keeps the mud and muck off the back of my jacket, but it does nothing to stop the muck from hitting the rear portion of the frame.

 

[Alaskan]

Actually, earlier this afternoon, I sourced what we need from a cycle shop in the UK

FSA G3/4 Bosch EBike Bicycle Cycle Alloy 104 BCD 1X11 Chainring Black

FSA G3/4 Bosch E-Bike Bicycle Cycle Alloy 104 BCD 1X11 Chainring Black | eBay

Find many great new & used options and get the best deals for FSA G3/4 Bosch E-Bike Bicycle Cycle Alloy 104 BCD 1X11 Chainring Black at the best online prices at eBay! Free shipping for many products!

ebay.us

 

[Deacon Blues]

Alaskan, great find! Are you going to order one?

 

[Stefan Mikes]

Alaskan, great find! Are you going to order one?

As I can see, Alaskan has already bought one from the website

 

[Alaskan]

Alaskan, great find! Are you going to order one?

@Stefan Mikes came to the correct conclusion. I have already placed my order for the 46 tooth.

 

[Deacon Blues]

Alaskan, you don't waste any time.
I'm going to phone the shop I bought the bike from and see if they can order one (and at what cost). The shop is about 150km from where I live, but I'm spending a week there in May (RVing).

 

[almikel]

I'm finding that I often ride with the cassette in the smallest or next smallest cog. On the flats I'm okay, but on a slight downhill grade I often run out of gears (and I'm way past the motor cut-off).
I ride a Cannondale Topstone Neo Lefty 3, which has a 42T chain ring and an 11to 42 cassette. The Lefty 1 (more expensive model) has a 46T chain ring, with a 10 to 50 cassette.
I want to replace my 42T chain ring with the 46T chain ring found on the Lefty 1. I figure it should be an easy swap.

I find the same on my Giant Revolt - on pavement with any slight downhill grade I'm in the smallest cog on the rear with an 11-42T cassette and 42T front chain ring...slight inclines and I'm still in the smallest 1/2 of the cassette...a bigger front chain ring would be handy for me...

Bosch system is programmed for very smooth power delivery and also shift sensing. So, it requires OEMs to input the drivetrain ratio into the system.
The shift sensing works differently for derailleur vs IGH systems. On an automatic IGH like the E-14 or Enviolo automatiq, it is a bit more subtle and reduces the power when the cranks are in 6'clock position to allow for more smoother shift.

If you go from 40 to 48T, you might encounter an error code because the ratios are getting messed up but within a certain range, you could do it. Since the left 1 has 46T and 10-50T cassette, ask them to look at the gearing ratio used in the system and then reprogram yours to that ratio. Then you will be able to use the same drivetrain that is on the Lefty 1.

Hi Ravi,
Are the Giant Syncdrive/Yamaha PX2 motors as sensitive to gear ratio changes as the Bosch Gen4?...I don't think they have the "shift sensing" you mention the Bosch Gen 4's have?

I figure it should be an easy swap.

I would have expected so, but apparently not

Mike