Convert drivetrain / transmission?

Terms

See here.

General

The selected transmission ratios, spreads, etc. have changed again and again over the range of electric motors. In the early years, small gear ratios were preferred. To achieve this, two or three chainrings were used. A 5-speed was introduced in 2020 with the ST2 Belt. From 2022, the number of gears increased again to up to 12 gears and 600 % gear range (spread) with the use of the Pinion 'C-Line' transmission line. In between, the tried and tested '52T / 11-42T' can be found on the later ST2, the ST2S / ST3 / ST5, which are equipped with a 52 chainring and an 11-speed cassette.

The gear ratio offered together with the respective tire circumference and the pedaling cadence (cadence) results in the respective achievable speed. The correlations can be seen in a Pinion calculator be calculated.

Here in the example I show the calculations for my converted cassette (from 42 to 46T) on the ST3. The 46 teeth on the lowest gear allow me a little more cadence on steep climbs in my hilly riding area and thus a slightly improved 'climbing ability'.

Pinion models: ST3 / ST5 / ST7

The configuration of the belt drive is as follows:

Pinion: On the ST3 with the Pinion C1.9 XT, this configuration results in a gear ratio of 0.32 in the highest gear, a Unfolding of 12.3 m and a cadence/cadence of only 62 crank revolutions per minute at 45 km/h.

Chain: The Stromer ST3 / ST5 with derailleur gears require 72 rpm in the highest gear, the ST2 with 26″ tires even 79.5!

Cassette conversion - ST3

To increase the 'climbing ability' of the ST2 / ST3 / ST5 you can change the cassette. Instead of the 11-42T you can fit an 11-46T. These are available from Shimano, for example. On my ST3 I have the Shimano Deore XT CS-M8000 cassette 11-fold / 46T installed. The conversion is simple. The setting of the B-screw on the changer must be readjusted, but the chain itself does not need to be adjusted.

Conversion - ST2 (newer models) / ST3-, ST5 with Gossamer 52T chainring

There are two ways to reduce the cadence. Replace the chainring with a larger one or change the cassette to a 10-speed sprocket.

As there are no 10-speed sprockets available for the Shimano 11-42 cassettes fitted, this option is not available. That leaves the chainring. Stromer installs a Gossamer 52T chainring with narrow/wide teeth. This can be replaced by one with more teeth. It should be noted that the chain guard must also be replaced if you go beyond 56 teeth. The chain length would also have to be adjusted. A good compromise would be a ALIZE 5-ARM**external - 130 mm bolt circle - 56 teeth. This reduces the theoretical cadence at 45 km/h from 72 to 67 rpm.

**Attention: If you want to use the original Stromer chain guard, the bulges for the chain guard struts must be large enough!

Conversion - Pinion - Can the gear ratio be changed?

There are larger pulleys at the front - but not with Pinion mounts. The rear might be possible. 20T(or 19T), but the rhyme would probably have to be adapted?

The unfolding increases from 12.2 m to 13.5 m (20T) or 14.2 m (19T). With the standard configuration, the cadence at 45 km/h is 61, at 20T, 56 and with 19T, 53. 

IMHO 61 is very low. From a sports medicine point of view, higher cadences are more optimal for the effort required and therefore also for the joints - but in the end it's a matter of individual taste.

> See also the chapter SHIFTING