Rear wheel 8 to 7 speed

[eligri]

Hey!

Trying to order a e-bike 1000w kit. I will be converting a 10 year old mountainbike (steel frame). It is however 8 speed (8*3), but most conversions with rear-hub seem to have 7 speed gears. Will this be an issue?

Read that rear hubs are safer than front hubs. Should I still consider front hub for any reason?

Thanks!

 

[eligri]

Looking at this one:
https://www.ebay.com/itm/26-48V-1000W-E-bike-Conversion-Kit-for-Rear-Wheel-Hub-Motor-Conversion-Kit-UK/193294198024?hash=item2d013b6508:g:IP4AAOSwKpNeGB63

Or if front wheel:
https://www.ebay.com/itm/26-Electric-Bicycle-Front-Wheel-Conversion-Kit-E-Bike-Cycling-Hub-48V-1000W-NEW/192828824873?hash=item2ce57e5d29:g:GpoAAOSwjhJeHS9b

Any other suggestions for ~200-250$ from Europe?

Also curious as to if these have a 250W switch, for when I need it to be road-legal.
Tried contacting seller, but not getting any answers.

Thanks again

 

[john61ct]

Front wheel hub **can** be made perfectly safe, but requires very strong stiff / rigid forks and robust double torque arms

 

[E-HP]

Hey!

Trying to order a e-bike 1000w kit. I will be converting a 10 year old mountainbike (steel frame). It is however 8 speed (8*3), but most conversions with rear-hub seem to have 7 speed gears. Will this be an issue?

Read that rear hubs are safer than front hubs. Should I still consider front hub for any reason?

Thanks!

You may do some shifting when you first convert the bike, mostly out of habit. But after that, you may only shift on rare occasions, which makes 7 vs 8 speeds less relevant. You may need to change your shifter if the gears don't index properly after adjusting.

 

[eligri]

Hey!

Trying to order a e-bike 1000w kit. I will be converting a 10 year old mountainbike (steel frame). It is however 8 speed (8*3), but most conversions with rear-hub seem to have 7 speed gears. Will this be an issue?

Read that rear hubs are safer than front hubs. Should I still consider front hub for any reason?

Thanks!

You may do some shifting when you first convert the bike, mostly out of habit. But after that, you may only shift on rare occasions, which makes 7 vs 8 speeds less relevant. You may need to change your shifter if the gears don't index properly after adjusting.

Just something like this, then?
https://www.bikester.se/shimano-tourney-sl-rs36-grip-shifter-7-speed-right-M735047.html

 

[Balmorhea]

Just something like this, then?
https://www.bikester.se/shimano-tourney-sl-rs36-grip-shifter-7-speed-right-M735047.html

No, not like that. Whether you use a thumb throttle or a twist throttle, that thing will interfere. Best is to use a thumb shifter:

Second best is to use a trigger shifter, though this limits your throttle options.

 

[E-HP]

Just something like this, then?
https://www.bikester.se/shimano-tourney-sl-rs36-grip-shifter-7-speed-right-M735047.html

i use one like that, but mount it on the left side.

 

[batpot]

I think the fundamental question that hasn't been answered yet is whether your 8 speed cassette will fit a motorized rear wheel free hub body.

I do not know the answer, but am curious.
Generally speaking, 8,9,10 are wider than 6,7, so it likely will not fit.

That bring said, what E-HP said is right on: just use the 7 speed; with 1000W in the back, you won't miss it.

 

[Balmorhea]

“7 speed” hub motors are in my observation always threaded, with enough axle spacing to use standard 7,6,5, or 1-speed freewheels. If you add washers inside the dropout, you can use the less common 8/9/10-speed freewheels, provided the frame is widened and the wheel is dished accordingly.

Cassette hub motors always have 8/9/10 speed Shimano pattern splines, which can accept 7-speed cassettes if there’s a 4mm spacer behind them.

 

[batpot]

“7 speed” hub motors are in my observation always threaded, with enough axle spacing to use standard 7,6,5, or 1-speed freewheels. If you add washers inside the dropout, you can use the less common 8/9/10-speed freewheels, provided the frame is widened and the wheel is dished accordingly.

Cassette hub motors always have 8/9/10 speed Shimano pattern splines, which can accept 7-speed cassettes if there’s a 4mm spacer behind them.

Didn't know there were "cassette hub motors".
Sounds like that's what OP should look for, and just use existing group set.

 

[john61ct]

Cassette hub motors

With that phrase do you mean geared or also DD hub motors?

Are all DD models the same in that respect?

 

[Balmorhea]

Cassette hub motors

With that phrase do you mean geared or also DD hub motors?

Are all DD models the same in that respect?

Threaded vs. cassette is a property of the hub’s side cover, not the motor inside.

 

[john61ct]

Are you saying there are motors where that side cover can be swapped out if a different type is desired?

Not trying to nit pick here, noob with genuine ignorance on this topic.

 

[Voltron]

The picture shows the difference between threaded hub with freewheel, and splined freehub with slide on cassette. Either one could be any number of speeds.

6,7 and 8 all use the same spacing between the shifter clicks and chain width, so one could use a 7 speed shifter on an 8 speed cluster, and choose whether you can't reach the high or the low gear, or 8 speed shifter with 7 speed gear cluster, and decide which shifter click you don't use. But not 8 matched with 9 or more... The spacing is different.

 

[Voltron]

Also, usually no, not really on swapping covers... That side of the axle is different between free hub and freewheel thread versions, on most of them anyway. Usually the cheapest thing to do is buy a freewheel or cassette to match the motor if what you have is different.

 

[Balmorhea]

Usually the cheapest thing to do is buy a freewheel or cassette to match the motor if what you have is different.

Often that’s true, but there are many times that adapting a threaded “7-speed” hub motor to an 8/9/10 speed bike becomes more complicated than converting the bike to 7-speed.

One thing I recommend against, which is often advised in this forum and others, is mixing different gear counts on the shifter and freewheel. If you don’t pedal in earnest, it doesn’t matter. But if you do pedal, that’s setting yourself up for accelerated wear and gear skipping under load.

 

[Voltron]

Converting a 9 or 10 to 7 or 8 yes, but usually 7 to 8 is just figuring out which gear or click you don't want to use as the chain width and click spacing is the same.

 

[Balmorhea]

Converting a 9 or 10 to 7 or 8 yes, but usually 7 to 8 is just figuring out which gear or click you don't want to use as the chain width and click spacing is the same.

7 speed uses 5.0mm intervals, but 8 speed uses 4.8mm intervals. In between any two gears, this is within the mechanism’s tolerance of misalignment, but across the cassette it represents a 1.4mm discrepancy. That’s enough to unship the chain when you’re pushing hard on the pedals.

 

[Voltron]

It's seems to work fine... Which is why they sell the same chain for 6,7 and 8.

 

[Balmorhea]

It's seems to work fine... Which is why they sell the same chain for 6,7 and 8.

KMC-X893-CHAIN-6-to-8-SPEED.jpg

Chain width is limited by, but not tied to, sprocket spacing. You could just as well call 9-speed chain “7/8/9 speed” or 12-speed chain “10/11/12 speed”, because that works too. My point is that there’s no way to reconcile 7 speed and 8 speed components at the extremes of the range. You can get workable shifting at one end or the other, but the misadjusted end will cause problems.

It’s true that many e-bikers don’t use their lower gears generally. But then there’s a motor problem, and they’re the ones most needed.

 

[Voltron]

I'm just going from my own experience where it hasn't been a problem.

 

[john61ct]

So, ELI5 please, assuming nothing has yet been purchased

which hub type are most hub motors? All?

are geared ones the same or different in that regard from direct?

And are threading gauges pretty well standardized between EU/China/USA?

I understand with motors, even DD, much fewer external gears are actually needed. But if I want leg muscle power to contribute as much as possible, isn't there still and advantage to lots of gears?

 

[Voltron]

And it's not like I'm the one calling it 6-7-8 speed chain.. That's what the two biggest bike chain manufacturers sell it as...

 

[Voltron]

And john61ct, yes, if you really want to pedal along, more gears is usually better. But the steps between the gears is important too, depending on how fast you like to accelerate. On one of my hub motor bikes, it has a triple on the front, and 8 rear, but when going thru a series of stop signs in the city, it's just as fast to shift with the front 3. Otherwise, you have to double shift the rear to keep up with the acceleration, then shift all the way back during decel to get ready to sprint out towards the next stop.. If you're going on a steady climb, esp with just leg power, where you're shifting infrequently, but want to exactly match your leg cadence to the speed, then more is definitely better. But for fast frequent speed changes, maybe less gears with faster engagement is just as good.

 

[E-HP]

Didn't know there were "cassette hub motors".
Sounds like that's what OP should look for, and just use existing group set.

The leafbike motors have a cassette option. There's a few motors that offer cassettes, but it's not the norm.

Even if you end up shifting for some reason, 7 speeds are all you need for a hub motor, since you need to maintain decent speeds to keep your motor from frying itself on climbs anyway, so the really low gears don't get used. <sorry, that was a long sentence>

https://www.leafbike.com/products/e-bike-hub-motor/48v-52v-1500w-rear-spoke-hub-motor-electric-bike-motor-spline-cassette-1110.html