Potential fix for low gearing on SC2 Highspeed?

[sammcneill]

Hi.
I'm not sure if Philip Pierce is on this forum or not, but he commented on my blog post here, and provided the following solution to my 'complaint' around low gearing on SC2 meaning it's difficult to get the full value of the HS boost above 40kph

Hi Sam, just read your article on the R&M sc2 vario high speed bike, although 11 months on, you have likely worked how to increase your gearing. Any how change front chain ring to 55T and rear pinion to 24T this is all for Gates drive your bike shop should do this for you.
Also if you register your bike with R&M, then you can make some adjustments under MY BIKE All this can be done on line, main points are custom ride modes you choose the power to ride, maps and ride data, however to do this you must have the NYON/smartphone app controller, these are not expensive, except the controller, check out your options.

I have the roadster mixte vario HS also bought for my lovely wife, mine came with the above spec as standard for 2021.

I did look into this a while back but I estimate I only have 2-3mm clearance between the current chainring and the frame. I just don't see how it would be possible to put a bigger one on the front.

Has anyone here ever done this? @JVBulman I know you're working on these bikes day in and day out - is this something that can be achieved? I'd happily pay to get this done at the LBS if it meant I could reduce the cadence and obtain higher resistance to push consistently into that 40-45kph speed (where it's safe to do so)

Happy to post a photo of the chainring and gap if that would be useful.
Cheers
Sam

 

[JVBulman]

If you lack the clearence to install a bigger chainring, you can still increase the gearing by installing a smaller rear cog.

 

[sammcneill]

Thanks @JVBulman

He also suggested I check the settings under My Bike here:

https://www.r-m.de/en-au/my-bike/my-bike/

which appears to already have the sizes he suggested:

Chain ring55T, for Gates drive belt CDX
Chain guardRiemenschutzring
ChainGates drive belt CDX
Pinion24T, for Gates drive belt CDX

I'm assuming "MyBike" configurations actually ARE my bike and not just generic settings for the SC2.

If I was to put a smaller rear cog in, would I need to get a different size Belt? assuming yes....?

Thanks

 

[JVBulman]

At a glance, it looks like the only option from Gates for a smaller cog is a 22T. I'm not able to test it right now, but the sliding dropouts might have enough range to cover a difference of two-teeth.

That said, if my napkin math is right this will only increase your gearing by about 8.5%...

 

[sammcneill]

Thanks mate - will make it a problem for the LBS - not sure what the cost of a 22T cog is, but even 8.5% gearing increase would be greatly appreciated as my city is very flat and we don't need super low gearing.

 

[JVBulman]

Thanks mate - will make it a problem for the LBS - not sure what the cost of a 22T cog is, but even 8.5% gearing increase would be greatly appreciated as my city is very flat and we don't need super low gearing.

They're usually $80-$100USD.

Good luck, and let us know if your shop comes up with a better solution.

 

[peterh_nz]

Hello Sam

This topic follows on from an earlier discussion we had. From memory, my SC2 with Rohloff hub requires a cadence of 75 to acheive 40kmh in top gear. The belt drive sprockets on my bike are 55T to 19T.

So you might want to decide on the cadence you want at, say, 40kmh and adjust the rear sprocket size accordingly. That is, you could possibly go less than 22T if you wanted.

Cheers

 

[sammcneill]

Thanks Peter,
Yes we have discussed this. Did your bike come with a 19T sprocket or have you reduced it to that aftermarket?

I do see 19T ones here:

Rear Sprockets

Rear Sprockets

www.gatescarbondrive.com

Remind me - are you on a Vario or Rohloff?

Also, can you check the R&M "My Bike" portal and see if you're listed as having 19T rear sprocket?

Cheers
Sam

 

[JVBulman]

@sammcneill You'll want to narrow your search to Enviolo cogs specifically as they have a special fitting vs Rohloff: The smallest size is 22t.

Rear Sprockets

Rear Sprockets

www.gatescarbondrive.com

 

[peterh_nz]

Thanks Peter,
Yes we have discussed this. Did your bike come with a 19T sprocket or have you reduced it to that aftermarket?

I do see 19T ones here:

Rear Sprockets

Rear Sprockets

www.gatescarbondrive.com

Remind me - are you on a Vario or Rohloff?

Also, can you check the R&M "My Bike" portal and see if you're listed as having 19T rear sprocket?

Cheers
Sam

As I mentioned above, Rohloff. The 55T to 19T are as specified and purchased.

How many tooth belt does your bike have? If I've read correctly, mine is "Gates Carbon Drive 11M-125T-120T". From that I don't know if it's 125 or 120T!

.... ah, it seems like it's 125T and I misread the second number which is "12CT".

 

[sammcneill]

Sorry Peter - skim reading whilst working is not great for me - missed your very obvious reference to Rohloff! Apologies!

I've gone to Christchurch Electric Bikes to see if tehy could help with a 19T rear (and noting @JVBulman on the 22T for Vario) and see what tehy say.

Will report back if I have any success here team!

 

[peterh_nz]

Sorry Peter - skim reading whilst working is not great for me - missed your very obvious reference to Rohloff! Apologies!

I've gone to Christchurch Electric Bikes to see if tehy could help with a 19T rear (and noting @JVBulman on the 22T for Vario) and see what tehy say.

Will report back if I have any success here team!

Thanks. Am interested in hearing the outcome.