cassette choice?

Hello all

I am in the process of fitting my 1000watt 48volt rear hub conversion onto a Carrera banshi, the bike came with shimmano 8 speed and a 3 speed crank.

1) I am assuming I will only be able to fit a 7 speed cassette in there now due to clearance issues

2) If I chose a 7 speed cassete is this going to effect anything having been 8 speed before?

3) Do I have to match the makes of cassette or can they be any make?

4) Any tooth size recommendations like go for more of less teethe like when you remove a cog from a scrambler to gain bottom end or am I over thinking this?

Thanks in advance I will get pics up when it is all done, its an ebay kit by panda ;-0

You need a freewheel for your hub motor, not a cassette. Any 7-speed freewheel from the last 25 years or so will be compatible with a 7-speed index shifter. You have to use a 7-speed shifter, though. The spacing between sprockets is different enough that your 8-speed shifter won't work.

You are limited to 14-28 or 14-34 freewheels if you want low cost, widely available 7-speed units.

Hi Chalo

I had an 8 speed shifter and 8 gears fitted to the bike not a 7 speed so I will need an 8 speed?

Also ive run into problems, I want to use the regain breaks however I have hydraulic rear so cant use the rear and the front break leaver wont house the gear lever mechanism ffs ;-( so in order to have regain I would have to loose my 8 speed shifter which could be an option.

Could I just fit an 8 speed rear freewheel but only toggle through 1/2/3 hi ratios so I tehcnicly have 3 long gears I can use to pedal with?

Ive got till Monday as this will then be my only form of transport whilst motorbike gets fixed (engine rebuild).

I know I could just be lazy and not pedal all the way to work and back but id like to put some work in get some cv and that

Thanks for your imput as you can tell I know nowt about bikes.

Your hub probably only provides enough room to fit a 7-speed freewheel. So use a 7-speed freewheel, and get a 7-speed shifter to replace your 8-speed shifter.

Do what Chalo recommends for the best results. Just get a 7 speed screw on freewheel for the motor, and put a 7 speed shifter on it. Or an old school friction shifter that does not index.

FWIW, many of us put the bike in high gear, and never shift again once we get a motor on the bike. Or maybe you pick 2nd or 3rd highest, and rarely shift out of whatever is your favorite.

So this means, the shifter not indexing to all your gears perfectly may not matter one bit. An 8 speed shifter can be adjusted to index perfect on one gear of the 7 speed freewheel, and it will be good enough on one or two adjacent cogs. So it may run fine for you with an 8 speed shifter. Just make the cable adjustments so your chain runs smoothly in your favorite gear. You really won't need more than about 3 choices on the rear gears once you have a one hp motor pushing you along.

I have one bike with an 8 speed shifter and a 7 speed freewheel that I've been meaning to convert to 7 speed shift for 5 years. I just never get around to it. The shifter I need to do it is sitting right there in my garage.

Mostly I leave the bike in a lower gear for dirt use. Once in a blue moon I do ride it on the street, and I simply give the shifter barrel nut a few turns to adjust it to run smooth in high gear.

A free-wheel wit 14T top gear is too low for an electric bike. You won't be able to move your feet fast enough. I have free-wheels with 11T top gear for £20 plus postage in the UK. PM me if you want one. I have 7 and 8 speed. The 8 speed is 1mm wider. It'll probably be OK with a couple of washers on your axle. You might need to dish your wheel a bit to get the rim central.

d8veh said:

A free-wheel wit 14T top gear is too low for an electric bike. You won't be able to move your feet fast enough. I have free-wheels with 11T top gear for £20 plus postage in the UK.

Click to expand...

Since Shimano stopped making 11-34 and 11-28 7-speed freewheels a decade ago, all the 11t freewheels I have seen have been ultra-nasty low quality units that fail early and often (e.g. DNP Epoch). Please report if you've found something decent.

Switching to a crank with a 52t or larger ring is a mechanically much more effective way to get tall gearing. 53/14 gearing on a fat tire 26" bike takes you to 30mph at 100 pedal RPM. Over 30mph, pedaling adds enough aero drag that it doesn't net you much added speed. Better to level the pedals, pull your knees in tight, and crouch (unless you have to fake-pedal to stay out of legal trouble).

11t sprockets are not only inefficient and prone to skipping, but they wear out your chain quickly-- which in turn wears out your other sprockets. I just locked out the 11t sprocket on my new 9-speed cassette because it's the only part of the bike that doesn't work worth a damn, and because I don't need it.

This keeps coming up, and I'm baffled. I'm the first to admit I know next to nothing about cassette's, but I do have a 7 and 8 speed epoch in my hands right now. The gear spacing is the same. I didn't see a millimeter difference in height side by side either. I thought I was going to have to switch down from 8 to the smaller 7 during a current build, but nope, they occupy the same space.

I was going to take pics, but the 8 is now fitted. I put off the pics as I have another in the post and my spirit level is on loan. It should come one day. If In fact a bmsb cassette freewheel is not a cassette.(meanwhile, a cassette bike also sits here on the off-chance it's getting new gears instead)

I like my 52T crank, but such a large thing is rarely seen on 26" bikes. The mountain and town bikes we tend to stick with, come with a 44T or 48T if your lucky. I moved up from a 48T though, it was still too small. 52T on a 3 wheel crank with chain guard is a rare thing though. Especially if you want it for $25


Really quite concerned about this spacing info. I'm just not seeing it, but trust you guys enough to doubt my own eye's a little. The millimeter could well exist, but these 7 and 8s are spaced the same. I had taken it for granted 7 and 8 speed shifters were compatible. I read 9 speed required narrow spacing, forcing a chain width chain. Something I have seen when buying chain.


Decided there was only one course of action: http://sheldonbrown.com/cribsheet-spacing.html#k7fw
It's all messed up. SRAM for instance space there freewheels at 5mm for both 7 and 8 speed. Not their cassettes though, for cassettes the 5mm 7 speed spacing drops to 4.8mm spacing for the 8 speed. As does most Shimano stuff.

The 8 speed I'm working on has SRAM shifters listed their as 5mm spacing. So the general consensus is that they won't work with shimano gears unless it's a 7 speed cassette? Lets hope my eyes are not deceiving me, and 7 and 8 epochs are the same. Something I really must measure now, unless d8veh beats me to it

The spacing difference between 6 and 7 speed sprockets is usually 0.5mm. Between 7 and 8 it's usually 0.2mm, and between 8 and 9 it's usually 0.16mm. The trouble with a 0.16mm discrepancy is that you've got 8 of them across the cassette, and they stack up. The more speeds you have, the more precision it takes for them to work right.

The difference in width between a Shimano 7-speed cassette and a Shimano 8-speed cassette is 3.1 to 3.5mm. Freewheels vary a little in how far they overhang the outermost sprocket, but remember that the chain has to have clearance to sit on the outer sprocket without rubbing the frame. That means even a freewheel with zero overhang can't be pushed right up to the frame.

A 53/39t double crank can be very cheap. You don't have to use a triple crank just because your bike came with one. Lots of folks here report never using any but their top gears anyway.

The 53T is nice, but for me it offers no chain guard. Would it work with a 44T derailleur? So many bikes use them, it would be good to know.
I use my gears somewhat, but my front changer failed on my maiden voyage. I think I use the rear from 13T to the mid 20s. If I run out of power I may flick the chain off the 52 to the 42 but the 34 is just silly. I have a feeling that with the front derailleur working, I would rarely use the rear. Just going 42/52 most of the time.

I'm pleased to hear the shimano 8 is stacked higher than the 7. I have a 7 on my cst and needed to make a spacer around 5mm thick. Seeing the epochs 7&8 look identical, had me wondering what the cst expected me to fit lol. You sure don't need close ratio's with an ebike.

Where are all the 5 speed options. 5 is ample. 5 well spread gears like 11-36 if a derailleur can hack it. It's not to tall between gears if you have a motor. With 7 speeds, I'm changing up at a frequency close to 1 a second. Making me very aware that I'm using gear sets designed for non assisted use. 5 in the back, one in front, nice weight saving with aero advantage. Minimal kit for the 'I don't pedal' crowd.

Chalo said:

Since Shimano stopped making 11-34 and 11-28 7-speed freewheels a decade ago, all the 11t freewheels I have seen have been ultra-nasty low quality units that fail early and often (e.g. DNP Epoch). Please report if you've found something decent.

Switching to a crank with a 52t or larger ring is a mechanically much more effective way to get tall gearing. 53/14 gearing on a fat tire 26" bike takes you to 30mph at 100 pedal RPM. Over 30mph, pedaling adds enough aero drag that it doesn't net you much added speed. Better to level the pedals, pull your knees in tight, and crouch (unless you have to fake-pedal to stay out of legal trouble).

11t sprockets are not only inefficient and prone to skipping, but they wear out your chain quickly-- which in turn wears out your other sprockets. I just locked out the 11t sprocket on my new 9-speed cassette because it's the only part of the bike that doesn't work worth a damn, and because I don't need it.

Click to expand...

I believe that you're talking from experience of bikes without hub-motors, where maybe the stress is much higher. Myself and many of my friends and UK Pedelecs forum members have been using DNP free-wheels for many years. None of us have ever experienced any noticeable wear or failure. They're not exactly expensive either in the unlikely event that you did have to replace one.

If someone is a sporting cyclist and likes to pedal hard, a hub-motor that takes a freewheel is probably the wrong choice anyway. They might be better off with a cassette motor like the Q100C or Bafang CST, or maybe a crank-drive system.

As far as I can see, most people want a motor so that they don't have to pedal hard, in which case a DNP freewheel is more than adequate and probably better than the one they already have even if it's not as good as the no longer available Shimano one.

Fitting a 52T or 53T crank is also not without problems. On MTBs, there often isn't enough clearance from the chainstay, which means adding spacers behind the BB on the drive side, which then means you need a longer BB and your chain is no longer on the ideal line. Also, as already pointed out, it's difficult to find a chainguard for 52T.

I have found that my ideal combination for pedalling a bike with a rear hub-motor (freewheel type) at 20 to 25 mph, considering low price, functionality and durability, is the 48T Shimano M590 crankset and the DNP 11T/30T freewheel.

Motor or not, it's still true that an 11t sprocket will wear your chain faster if you pedal hard. Some do pedal hard for a few feet leaving the stop sign, and that can wear the chain fairly quick.

for sure, you will notice some clicking when using a 7 speed freewheel, and an 8 speed shifter. This will be worst if you index the shifter to run best on one end of the cluster. So if you index to run smooth on the small gear, it will index poorly on the largest one.

Adjust your 8 speed shifter to run perfect on the gear you will use the most. Most of us only use 2-3 gears once you have the motor. It will index ok enough on three gears.