BBS01 Chainrings

I have fitted a BBS01 to an old Specialized Stumpjumper FSR and it's working well!

I want to lower the gearing for off-road, but there doesn't seem to be a simple way to purchase a smaller chainring in the UK - I see 44t on eBay, but that is only 2 teeth down so not much help.

The chain line will not allow to go any further out as 2nd is a worrying angle, 1st I just don't use.

Any suggestions? I'm thinking 40 or 42t...

Thanks

Steve

 

.....The chain line will not allow to go any further out as 2nd is a worrying angle, 1st I just don't use.......

I am not specifically familiar with your set up but I was similarly unhappy with chain line on TSDZ2 with the lower gears. Anyhow I managed to dismantle the gear cluster and rearrange cogs to give a wide spread of ratios over 7 speeds with the chain line on the 18 tooth cog. i.e. 13/15/18/21/24/28/34.

I reckon for ebike's in general, you need a different set of ratios with less gears and a bigger spread. especially on the lower gears.

If you buy a lekkie 42 bling ring [not cheap], but it has the added advantage of moving the chain line inwards

or a cheaper option is to try a chain guide

. Anyhow I managed to dismantle the gear cluster and rearrange cogs to give a wide spread of ratios over 7 speeds with the chain line on the 18 tooth cog. i.e. 13/15/18/21/24/28/34.

Interesting idea. I had a quick look at an old cassette and its easy enough to do, will have to look at the teeth spacing as I think only have 11t so would be a relatively big jump, I can see having a 13t top gear on the lock ring would be good.

If you buy a lekkie 42 bling ring [not cheap], but it has the added advantage of moving the chain line inwards

Well.... actually the standard ring has quite a pronounced dish inwards to help the chain-line, so I can only assume a Bling ring would just move it out as its flat?

The 36 lekkie is flat but 42 and above are dished, luna cycles used to have a range with different offset

Ah, yes my mistake. At that price, and made from softer aluminium I think I will look at other options

Just for interest, I have found that as my fitness increased the need for lower gears has gone and I quite often want a higher gear! Well, downhill anyway.

One thing of note with the BBS01 is that it's power curve peaks at quite a low rpm, or at least quite a bit lower than my normal cadence.

This means that to benefit from the motor on a steep hill needs a gear or two higher than you would use in unassisted mode.

I did swap to a 34 tooth cassette when changing the chain recently, 2nd gear now is plenty low enough without any nasty chain noises. 1st gear works reliably but does make a little noise due to the chain angle, but I never need it anyway.

....One thing of note with the BBS01 is that it's power curve peaks at quite a low rpm, or at least quite a bit lower than my normal cadence.

This means that to benefit from the motor on a steep hill needs a gear or two higher than you would use in unassisted mode.

I did swap to a 34 tooth cassette when changing the chain recently, 2nd gear now is plenty low enough without any nasty chain noises. 1st gear works reliably but does make a little noise due to the chain angle, but I never need it anyway.

On most 'controlled' electric motors, the power seems to peaks around 60-70% of max rpm but the motor is most efficient above 80%. (RPM = cadence on a mid drive)

The motor simulator can illustrate this e.g. On a 10% hill climb, the 24T rear cog has more power and faster than the 34T, but is less efficient and does result in a hotter motor (100 versus 70 C) and approx 10% extra battery consumption.

https://www.ebikes.ca/tools/simulator.html?mid=true&motor=MBBS02&gear=1&mass=120&tr=34&cont=cust_16_70_0.03_V&cont_b=cust_16_70_0.03_V&motor_b=MBBS02&mid_b=true&gear_b=1&mass_b=120&tr_b=24&bopen=true&grade=10&grade_b=10&hp=100&hp_b=100&wheel=700c&wheel_b=700c

This adaptor?

https://m.aliexpress.com/item/4000734950609.html?gatewayAdapt=Pc2Msite&aff_fcid=c6d832df65ba48c183caffdb4ed3311a-1644744699836-04420-_AFcGA1&tt=CPS_NORMAL&aff_fsk=_AFcGA1&aff_platform=shareComponent-detail&sk=_AFcGA1&aff_trace_key=c6d832df65ba48c183caffdb4ed3311a-1644744699836-04420-_AFcGA1&terminal_id=d9364e66a2494080ad1dfe22a7d73159