Should a 8S cassete be a good option for e-bikes?

Greetings all,

After reading all the troubles with bike chains not handling the load of a mid drive e-bike ( the one i'm mounting), i was wondering if i should go a 8S cassete for a thicker chain.
I will probably go with a Luna Cycles freewheel crank, XT M8000 SGS derailler and an 8S cassete, and at the end add the strongest chain i can get that work on them all.

Can i get a strong build this way, or is it impossible using bicycle chains to get a reliable machine?

Also, got an almost free offer on an hydraulic Avid Juicy 5 with 203/180mm disk brakes, that the owner used on his DH bike. Should be good for this right?

It will be a 2000w+ middrive road bike, to prioritize high speeds on the 40 MPH to comute between House and Job.

Thank you all for the help!

I'd say it depends on your commute and how you shift. I don't seem to use more than 3 or 4 gears, but it's flatland. Bad shifting habits and terrain are going to put more stress on the chain than difference in strengths between 8 and 9 speed chains. I snapped my first old chain a couple times, then replaced it and made sure to downshift at every light, as well as back off the throttle. It hasn't broken since, now it just falls off occasionally.

I have juicy 7's, they work great. Them and Elixir's are my favourite but I hear the Magura are better.

Good luck with using a road bike for a +2000W build. I'm not sure why anyone would do it. At 40mph your rolling rate of friction is nothing compared to wind resistance. The gain in efficiency/speed seems negligible compared to the threat of taco'ing a wheel. You get so much better control and wheel strength with a MTB. But I'm sure it's been done around here.

I don't think that the xt derailleur will work with 8 speed cassettes and chains.

Avner.

ferret said:

I don't think that the xt derailleur will work with 8 speed cassettes and chains.

Avner.

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I think it's OK. I haven't ventured into the 11 speed era but usually it's just the shifters you need to worry about. They might run a longer cage? but you should have chain clearance through the derailleur.

On a side note, I'm not sure it's worth using an XT derailleur on an ebike. I mean it's not a bad idea, but they seem to get chewed up and banged around a lot more. I have an older 8 spd Deore I think I'm going to use and try with aluminum wheels.

YES, it is the strongest setup possible other than going single speed. 6-7-8 chains are all the same with and strength.
I went with 9 speed because I wanted a clutched derallieur and you need to jump some extra hoops even compared to a 9 speed setup to do it with a 8 speed one.
Also you can get $25 50t cassettes for 9sp, but 42t is the biggest for 8sp on ali.

I have a 5kw mid drive with a 9sp chain and I daily commute on it ~30 miles total. It is possible. But you will likely have to forgo PAS and just clown pedal. The reason for this is power = torque * rpm. Torque kills chains and cogs. Keep the revs stupidly high and the torque will stay low. My chainring spins at 700 rpm max, compared to 160 rpm of a bbshd. For this reason even though the bike is 4x as powerful, it doesn't go through chains 4x as often.
I buy standard $18 KMC chains and they serve 4-5 months. I lube and wash them often.

Yeah, i don't do big aceleration, i just need the top speed. I was under the impression that both air and rolling resistances were small at that speed.
I just decided on a road bike because their geometry should be better / more stable that MTB for road and high speeds. Just a hunch mind you, one is for high speed on a road, the other is for close corners, so more nervous, right?

Glad to know the brakes are fine. One less problem!

I saw a thread here about using the XT derailler on a 9S cassete with big diferences between speeds (like 11-50T) and that one was recomended: https://bicycles.stackexchange.com/questions/54476/fitting-a-9-speed-11-50t-cassette-on-mtb-which-derailleur

In the end there's a table with recommendations, but at what point is a chain too wide to fit it?
9S is ok, what about 8s? Should i just stay with 9S?

satanicoo said:

Yeah, i don't do big aceleration, i just need the top speed. I was under the impression that both air and rolling resistances were small at that speed.
I just decided on a road bike because their geometry should be better / more stable that MTB for road and high speeds. Just a hunch mind you, one is for high speed on a road, the other is for close corners, so more nervous, right?

Glad to know the brakes are fine. One less problem!

I saw a thread here about using the XT derailler on a 9S cassete with big diferences between speeds (like 11-50T) and that one was recomended: https://bicycles.stackexchange.com/questions/54476/fitting-a-9-speed-11-50t-cassette-on-mtb-which-derailleur

In the end there's a table with recommendations, but at what point is a chain too wide to fit it?
9S is ok, what about 8s? Should i just stay with 9S?

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Only XC bikes or old mtb-s will get nervous at speed, the head angles of modern mtb are similar to motorbikes and the suspension helps you with road imperfections at speed.
With a road bike, you probably will get a better mileage, but I would only do it if the roads where you live are in quite good condition.

I got the deore m6000 gs, no need to go higher as it has a clutch. It can handle up to 42-46t. But you can use 50t too because ali sellers will give you a free extender (hanger-like bit) when you buy a big cassette.
https://www.aliexpress.com/item/32973873176.html

It is a 10 speed unit, but you can pair it with a 9 speed sram shifter, chain, cogs just fine. It would probably do 8 speed systems if you got a sram 8 speed shifter like this.
https://www.halfords.com/cycling/bike-parts/gears-drivetrain-cables/sram-x4-trigger-shifter-8speed-rear-1-1
The most important thing is the pull ratio, old shimano systems don't have 1:1, but new ones do. Sram has been 1:1 for a long time. Therefore if you want less speeds with a clutch, you must match shimano derallieur with sram shifter.

Tommm said:

My chainring spins at 700 rpm max,

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You can use that to cut crown moulding and 2x4's as well.

satanicoo said:

I just decided on a road bike because their geometry should be better / more stable that MTB for road and high speeds. Just a hunch mind you, one is for high speed on a road, the other is for close corners, so more nervous, right?

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More aerodynamic riding position maybe, but you really want to keep your head up doing 40mph.

OK, In My Opinion, no. Road bikes sit too high up, they have skinny wheels, and they have no suspension. If you're talking about a road bike ie: road bars, and not a hybrid, narrow bars are not as stable as say a nice wide downhill bar.

So yah, I'm going to say basically the exact opposite to what you think. Welcome to the internet!

The science behind my opinion is; wider tires keep your center mass in the "stability triangle", wider tires offer better suspension, so less energy is transmitted into the rider and the steering, wider steering ie; bars means more mechanical advantage (leverage). lower rider position also keeps the center mass down and over the "stability triangle", more frame flex also means less stability.

I think most of the guys not using MTB are using comfort or hybrid bikes with 700c wheels and fat tires, not road bikes. Hopefully someone with a mid drive on a road bike will give you some tips. You probably want something like a cyclocross rim and some fat 36H hubs I reckon.

furcifer said:

satanicoo said:

I just decided on a road bike because their geometry should be better / more stable that MTB for road and high speeds. Just a hunch mind you, one is for high speed on a road, the other is for close corners, so more nervous, right?

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More aerodynamic riding position maybe, but you really want to keep your head up doing 40mph.

OK, In My Opinion, no. Road bikes sit too high up, they have skinny wheels, and they have no suspension. If you're talking about a road bike ie: road bars, and not a hybrid, narrow bars are not as stable as say a nice wide downhill bar.

So yah, I'm going to say basically the exact opposite to what you think. Welcome to the internet!

The science behind my opinion is; wider tires keep your center mass in the "stability triangle", wider tires offer better suspension, so less energy is transmitted into the rider and the steering, wider steering ie; bars means more mechanical advantage (leverage). lower rider position also keeps the center mass down and over the "stability triangle", more frame flex also means less stability.

I think most of the guys not using MTB are using comfort or hybrid bikes with 700c wheels and fat tires, not road bikes. Hopefully someone with a mid drive on a road bike will give you some tips. You probably want something like a cyclocross rim and some fat 36H hubs I reckon.

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to handle the extra weight and power of electric you would want a heavy duty frame.. road bikes are optimized for lightweight and are not heavy duty like off-road bikes..

Thanks for the help guys, it is mostly very good roads, i dont want to go 23c tires but wont go 50c too, its a 18c Rims, i will go probably 35 or 40.
So, 8S 11-40T cassete, Xt derailler ( can get it cheap), KMC chain.
Any alternatives to the Luna freewheel crank?

satanicoo said:

Thanks for the help guys, it is mostly very good roads, i dont want to go 23c tires but wont go 50c too, its a 18c Rims, i will go probably 35 or 40.
So, 8S 11-40T cassete, Xt derailler ( can get it cheap), KMC chain.
Any alternatives to the Luna freewheel crank?

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Hi i done all this above . It work fine just care about brakes and tires the right one

Just cheap sunrace cass steel over Ti cass it last longer and cost less

Good luck

I've used schwalbe marathon race 35mm tires on a road ebike (not always they fit the road frames though) for some 10000 kms

It worked perfectly and has some cush to them for potholes. Smaller tyres below 30mm are too small to handle bad roads at speed ( if you're not in the giro )

40mph is still a bit stiff with a road setup. A pothole at that speed hits hard.
25-30mph - no issues.

One thing to note is that a normal road position with low bars gets more tiring for the upper body as you don't use your legs as much for counterforce on an ebike. Ideally your lean into the bars are balanced vs some of the force of your legs so a more upright position fits better for an ebike even with the increased drag.

There are reinforced 8-speed chains if you're worried about it. In my riding a standard 8-speed chain can run 2000W without issues, just shift somewhat carefully

And.. It will not be like cycling anymore at 2000w so in my opinion the road bike is not the best option for your ride. I used to do about 10000kms of unassisted cycling per year so i do have some background to judge this

chain wear gauge

used regularly

any sign wear

replace chain

cogs last much longer




replacement interval

cheap 6-8 speed stuff

about 1000 mile

2 months my commute

satanicoo said:

Thanks for the help guys, it is mostly very good roads,

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This is probably going to be your deciding factor. Anything but fresh asphalt is going to be tricky, even with 32C tires. You can get kevlar belted tires but you're still going to get pinch flats.

The cons really out weight the pros. To be honest, I don't find 40 mph on an ebike (DIY bicycle conversions) very enjoyable. High 20's to 30 is enjoyable, anything higher starts to be work. I can't imagine doing it on a road bike. It's doable, but you're kind of setting yourself up for failure. (this is assuming you want to average 40mph over 5-10 miles say)

Guys, don't think i stopped posting due to having my answers. I just like to research by myself and try to find my best options. Only when i can't figure it out i do ask questions.
Also work is heavy and doesn't leave much time to spare.

I've researched the chains, will go for the KMC X8, recommended by many. Non light version.

Is is true that there isn't a reliable ESC for RC motors, not even VESC? Investing in such controller, subject to have it stop mid drive to work is a big no no, i need to aim for a reliable build. Would love to have a use for my 6364 though.

Other than that, i'm slowly ordering parts and waiting for them to arrive. Then i'll assemble the ride, with my little time available should take months...

Thanks again!

It will be a 2000w+ middrive road bike

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I predict that it will work okay for the first several rides and then the teeth on both the chainring and the cassette side of the will start to wear a little. You will start to notice the chain "snagging" and the teeth will get to the point in which they are bend inwards too much to work proper. You will have to replace chainring and cassette at this point.

parajared said:

It will be a 2000w+ middrive road bike

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I predict that it will work okay for the first several rides and then the teeth on both the chainring and the cassette side of the will start to wear a little. You will start to notice the chain "snagging" and the teeth will get to the point in which they are bend inwards too much to work proper. You will have to replace chainring and cassette at this point.

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I don't think so, done this for two years with zero cassette changes. Front sprocket is a different animal since chain wears only one instead of 8.

Change chain and front properly, the cassette will be fine. Either way maintenance is not huge if you do this.

As with most generalizations you could be very wrong depending on ...
Which kind of Mounatin Bike
and
Which kind/brand of Road Bike

To be Specific, For the speeds you want to go ....

You only want a Road Bike that is designed to go fast , in other words an Expensive ! , Road Bike like a TimeTrail/Tri , or a Bike that the Pro's ride , example Specialized Tarmac / BMC Time Machine / Giant TCR Advanced , etc.
Now try putting a mid drive on a bike like that , good luck , look at the very large area of the Bottom Bracket .
You could do an aluminium Road like the Allez , but you will not be happy at 30-40 mph for long , Most Road Bikes beat up your body.
It is often said that the top Pro Road Racers are the people who can endure more pain than most every other Mortal Human .

In the case of MTB's , a Cross Country Race bike will be twitchy , however a All Mountain / Downhill MTB will not be twitchy,

In fact the best bike for your desired speeds is a All Mountain/ Downhill MTB ! ( higher the speed the more you want full suspension )

and now If you get an older AM/DH bike like made in 2010 or before you do not even need a mid-drive you can do what you want with a 3k watt rear DD Hub Motor. Which is better for commuting anyway .

If you do not heed the advice of many of us in trying to steer you away from a Road Bike for those higher speeds ... at least get the Friction Drive that Kepler has developed . ( and use a higher cell count on the battery like 7s instead of 6s or 5s ( read the latest posts for the current parts used )
With Kepler's drive you can keep the bike light weight and much less stress on a light weight road bike frame than the other mid-drives that weigh 10 pounds or more .
https://endless-sphere.com/forums/viewtopic.php?f=31&t=86961

satanicoo said:

I just decided on a road bike because their geometry should be better / more stable that MTB for road and high speeds. Just a hunch mind you, one is for high speed on a road, the other is for close corners, so more nervous, right?

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Very late update as promissed.
Due to covid and layoffs i got spare time for the last 2 months and decided to go forward with the build.
Here's a small video testing the build: https://youtu.be/fEJ3AHD_zI4

After realizing the 3 stage mistage, i changed it to 2 stage, and on the bench it measures 70 km/h.

Tested it today, it went way fast... for 300 meters until the motor burned.
I tried to controll the load but its pretty hard to drive and do it... the result is a dead motor.

A few questions:
-How can i check if the magnets of the motor are OK?
-Considering going the VESC + Sensored motor route, so i can configure a max motor Amp and be safe... Any thing higher than 50 Amps for the Vesc without breaking the bank?
-I really dont like my gearbox, ok it works, but i rather purchase one. Any recommendation for a 1:9 ratio unit?

NVM, why save now after all the expenses right?
Gonna get a Trampa Vesc 6, 80A continuous is more than enough for what i'm building.
Undecided on the motor but probably will go on an Alien C8085.

Will post later!