Shimano 21 speed gears

[mick.stirman]

Just bought a sheng miloMX01 1000 w electric bike with 21 speed gears. 2 questions
1. does anyone know how to de restrict the speed?
2 Can someone advise me on gear changes?
I've ridden bikes before but not for some time and never with 21 speeds. When changing gears from 7 to 8 and 15 to 16, which gear should I change first, the crank cogs (3) or the cassette cogs (7) and is it the same way when changing down? Thanks for any help.

 

[McCorby]

Most ebikes use a single front chain ring, so one thing to note with your setup, versus a single front chain ring, is that you need to be sure to avoid cross chaining. See link below. I would recommend keeping the chain on the front chain ring‘s middle sprocket until you learn to properly shift with the rear derailleur.

Excerpt from the linked article:

“The proper relationship of the chain to the gears is the straightest line. Never select gears where the chain runs from big to big or small to small. Select the gear so that the chain forms as near a straight line between the cog and the chainring in use.”

'Cross chaining' a real don't for a properly functioning bike

Improper gear selection stretches your chain unnecessarily, and the teeth of the chainrings and the cogs wear faster. Unnecessary wear on the chain and gears can be avoided if you never "cross chain."

www.active.com

 

[indianajo]

I don't understand the cross chain paranoia. I always wear out the middle sprocket of the rear cluster, never any front sprocket and never the low or high rear sprocket. Of course I ride on road. the wheels on the takeup wear out about 4000 miles, not the spring.
There is overlap between the large rear sprockets of the smaller front sprocket, and smaller rear sprockets of the next higher front sprocket. Use whichever combination suits your speed range.
I used to leave middle front sprocket on level ground and shift from 2nd rear out of stop signs to 4 or 5 on the flat. To 6 or 7 on downhills. However that thumb shifter caused a painful 10 cm x 1 cm cyst to grow over my thumb joint. I was age 62 at the time, now I'm 70. Twist shifter helped reduce cyst to 6 cm diameter. Now I leave the rear sprocket in 3 and shift the front sprocket from to 2 to 3. Use 1 front only on steeper grades. Cyst is gone. Left shifter receives push from the thumb, doesn't require swiveling it.
If shimano 7 speed rear, beware of it coming unscrewed and the balls falling out. It is made for kiddies that might ride the bike 500 miles in 6 years. The bearing race is held in place by a ferule pushed from the outer nut, and I'll tell you, it doesn't work at 3000 miles. I bought a 3/8"x26 nut (hard to receive, parts houses will list it but send you some other random piece of hex shaped junk), sawed it in half, and put it on the axle to counter torque against the race. That lasted several thousand miles without failure. Now I'm using a SRAM 8 speed rear sprocket. 4500 miles, no problem.

 

[McCorby]

I don't understand the cross chain paranoia.

It’s not paranoia, cross training is definitely a real thing that will eventually cause wear issues.

I’m glad what you do works well for you though!

 

[McCorby]

What cross chaining looks like....

 

[indianajo]

Might be a problem on 11 speed rears. Has not been a problem over 20000 miles on 15 speed, 18 speed, and 21 speed rears. What happens on 18 speed shimano rears, the 8 mm axle breaks.

 

[McCorby]

I guess we’ll just agree to disagree on this subject. It is a well known practice to use the correct front sprocket for the selected rear sprocket. Shimano notes this as a recommended best practice to reduce wear. They make no mention that it’s ok if the rear sprocket has less than 11 gears.

Quote from a Shimano representative:

The most efficient chain line occurs when the chain is running in a straight line. This minimises friction. When you run big-big you're pushing an uneven power transmission to the rollers, plates and bushings, especially at the points where the chain line alters (the points where the chain meets the sprocket and the chainring). This uneven load causes extra friction which increases the wear on the chain and longer term leads to less than optimum gear shifting.

For these reasons Shimano recommends avoiding extreme gear positions.

Ben Hillsdon, PR Officer, Shimano Europe

 

[FlatSix911]

Just bought a sheng miloMX01 1000 w electric bike with 21 speed gears. 2 questions
1. does anyone know how to de restrict the speed?
2 Can someone advise me on gear changes?
I've ridden bikes before but not for some time and never with 21 speeds. When changing gears from 7 to 8 and 15 to 16, which gear should I change first, the crank cogs (3) or the cassette cogs (7) and is it the same way when changing down? Thanks for any help.

Welcome to EBR and congratulations on your new EBike. Shengmilo MX01 - PushEVs

Regarding your questions:

1. It looks like you have a Bafang 1000W motor so de-restricting is difficult.
2. Regarding the gear shifting... think of your bike as having a manual transmission:

- the front chainring is like shifting gears... small ring for climbing, mid-ring for flats, and large ring for speed.
- the rear cassette cog is for fine-tuning the range of the front chainring selection... large cogs for climbing and small cogs for speed.
- the shift points will become second nature over time... you will spend most of your time in the middle range of the 3 front and 7 rear gears.

Hope this helps.

 

[mick.stirman]

Thanks for the swift replies folks

 

[mick.stirman]

Where can I get a manual for the Sheng Milo MX01?

 

[mick.stirman]

What tyre pressure should I use on a Sheng Milo MX01

 

[6zfshdb]

Two questions:
1 - Of the 21 gears, how many combinations are duplicates producing the same overall gear ratio?
2 - Why that many gears on an e-bike with a 1000 watt motor?