How much power is too much for a standard mtb?

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endrew   10 W

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How much power is too much for a standard mtb?

Post by endrew » Jul 31 2018 7:15am

Hi,
Im thinking of upgrading to a 3KW mid drive system. Im afraid it will be too much for my bike - I have a standard enduro rear wheel with 32, 2mm DT spokes and an wtb i29 asym rim and a standard 11 speed chain and cassette.

How much is too much for this setup? Will it take 3KW?

Tommm   10 kW

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Re: How much power is to much for a standard mtb?

Post by Tommm » Jul 31 2018 7:49am

If you shift and keep the revs up when accelerating, should be fine. Order a few spare chains(like $20 kmc x11-93) and switch to a steel cassette. Big selection on aliexpress for $25.

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Re: How much power is to much for a standard mtb?

Post by kdog » Jul 31 2018 8:01am

Well bikes are designed for human power levels. 3kw is comparable to a world class 200mt sprint champ mid sprint, going flat out on your bike...but continuously. It won't snap in half immediately but you are going to wear out that drive train real fast depending on how you ride it. Add in grit, water etc you get the idea
People do run mid drives at this power level(not me) , but often folks opt for a hub drive or a LHS separate drive train bc of wear and tear etc.
Hunt around for some threads in the non hub drive forum and see how others went.
There are also other issues you'll have like handling at high speed, suspension issues, breaking spokes and most importantly brakes. Even good normal brakes say XT with 180mm rotors start to seem average when you're doing 70+kph. 3kw is often about where moped class wheels etc become worthwhile.
Do it, it'll be a blast, but be aware of the issues.

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Chalo   100 GW

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Re: How much power is to much for a standard mtb?

Post by Chalo » Jul 31 2018 9:00am

endrew wrote:
Jul 31 2018 7:15am
Hi,
Im thinking of upgrading to a 3KW mid drive system. Im afraid it will be too much for my bike - I have a standard enduro rear wheel with 32, 2mm DT spokes and an wtb i29 asym rim and a standard 11 speed chain and cassette.

How much is to much for this setup? Will it take 3KW?
11 speed and mid drive are a bad combination even at modest power levels. You'll wear stuff out extra fast, and then pay an arm and a leg to keep those things replaced.

I recommend 8 speed parts with SunRace's 11-40 cassette. Don't use the 11t sprocket any more than necessary, because it tears things up. Buy 5 cassettes and 10 chains at a time, plus a chain checker. Replace stuff early and often.
This is to express my gratitude to Justin of Grin Technologies for his extraordinary measures to save this forum for the benefit of all.

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Alan B   100 GW

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Re: How much power is to much for a standard mtb?

Post by Alan B » Jul 31 2018 9:44am

Looks like it has been covered here pretty well. At 3kw you are getting to the power level that you can almost instantly break mid drive parts like chains and sprockets with a heavy throttle application. Jerky control is a problem, you need smooth controls, and best to stay with 14 or more tooth sprockets. The 11-13 tooth just doesn't have enough engagement. Prepare to maintain and replace mid drive parts often.

If you want high power consider a hubmotor or two, 5+ kw is no problem. Or a separate (left side) chain/sprocket drive that bypasses the bike gearing.

Bicycle gearing just isn't designed for high power.

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MaartenL   10 mW

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Re: How much power is too much for a standard mtb?

Post by MaartenL » Jul 31 2018 2:43pm

So, I just finished my build with a TSDZ2 500W midmotor and 48V 17.6Ah battery on a Fatbike.

I'm 190cm and 78KG and a pretty fit guy and this is my experience:

If you plan to use your MTB to actually ride offroad on trails than I can say from my experience that what I have is more than enough already. The amount of power I have now is already insane when I go offroad. I can climb the steepest hills and only when I climb more than 50meter and very steep I have to actually pedal a little harder and slow down but can always finish. Everything else is just tooooo easy.

If you just spend your time on the streets it's a different story maybe. My max speed is now 40km/h and I need to work to keep this speed.This could be solved when move up from 42T to something bigger though... However 35km/h is comfortable for me and that actually is already fast in the city.

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Ivanovitch_k   10 W

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Re: How much power is to much for a standard mtb?

Post by Ivanovitch_k » Aug 04 2018 7:20pm

Tommm wrote:
Jul 31 2018 7:49am
If you shift and keep the revs up when accelerating, should be fine. Order a few spare chains(like $20 kmc x11-93) and switch to a steel cassette. Big selection on aliexpress for $25.
would recommend the KMC X11-E chains instead, they are specifically reinforced for ebike use. I get 3500-4000km out of them on a BBS02 750W.

For the cassettes, I've got ~5000 km out of shimano 11spd XT 11-40. However I set the derailleur limit screw to never use the 40 granny which is aluminium. The 11T can wear out quite fast if used extensively but it can be independently replaced for ~5 eur.

A better cassette option would be sram XG-1150 10-42, 100% steel and all sprokets are riveted together.

Of course no shifting under power. Never. If you do, carry spare chain links and a breaker :mrgreen:
BBS'ed Radon ZR Team 8:
BBS02B 750W - DPC750C - 48V 17.5Ah GA shark - 11 spd 11-40 Shimano XT, 42T N-W Precialps CW, KMC X11e chain, Gearsensor, XT RD, XTR Shifter, F Saint Brake, R XT Brake, RT99 200/160 Discs, magnetic shutoff, DT Swiss X1900 QR9 wheels, Manitou M30 air fork, 2.4" slick balloon schwalbe Super Moto X tires @2 bars, Suntour NCX suspension seatpost, ergon SFC3 saddle, ergon GP3 grips, Supernova M99 Pro + E12 Taillight

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Re: How much power is to much for a standard mtb?

Post by Tommm » Aug 04 2018 7:59pm

Ivanovitch_k wrote:
Aug 04 2018 7:20pm
Tommm wrote:
Jul 31 2018 7:49am
If you shift and keep the revs up when accelerating, should be fine. Order a few spare chains(like $20 kmc x11-93) and switch to a steel cassette. Big selection on aliexpress for $25.
would recommend the KMC X11-E chains instead, they are specifically reinforced for ebike use. I get 3500-4000km out of them on a BBS02 750W.

For the cassettes, I've got ~5000 km out of shimano 11spd XT 11-40. However I set the derailleur limit screw to never use the 40 granny which is aluminium. The 11T can wear out quite fast if used extensively but it can be independently replaced for ~5 eur.

A better cassette option would be sram XG-1150 10-42, 100% steel and all sprokets are riveted together.

Of course no shifting under power. Never. If you do, carry spare chain links and a breaker :mrgreen:
KMC E chains are over 2x more expensive... I would be interested if they last 2x longer though.
You can buy cassettes from sunrace or even cheaper bolany on alexpress, they are all steel and one piece, up to 42t, 50t, and cost ~$25.

hobbyvac   100 mW

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Re: How much power is too much for a standard mtb?

Post by hobbyvac » Aug 04 2018 9:11pm

I am admittedly at one end of the spectrum. My 350 watt TSDZ2 drive is enough to make a 60 year old guy ride like he was 20 again. At 61 I still want the same exercise but now I can run the same pace I had in my younger days. I wouldn't want it any easier, I just want that same feeling I had when I was fit and young.

This is from a perspective of an ex racer and mountain bike single track riding. Street riding is a whole different scenario needing more power to fight the wind.

Sadly its the high powered bikes that turned the MTB community against us. All the great MTB trails in Michigan ban e-bikes completely. I got on the MMBA forum and the hostility against e-bikes was very concerning. So now I have a way to experience my youth again but I'm not allowed to ride anywhere except street or sandy motorcycle trails. I hope the opposition to e-bikes softens in a few years but I suspect they will be treated more like motorcycles instead.

Tommm   10 kW

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Re: How much power is too much for a standard mtb?

Post by Tommm » Aug 04 2018 9:12pm

hobbyvac wrote:
Aug 04 2018 9:11pm
I am admittedly at one end of the spectrum. My 350 watt TSDZ2 drive is enough to make a 60 year old guy ride like he was 20 again. At 61 I still want the same exercise but now I can run the same pace I had in my younger days. I wouldn't want it any easier, I just want that same feeling I had when I was fit and young.

This is from a perspective of an ex racer and mountain bike single track riding. Street riding is a whole different scenario needing more power to fight the wind.

Sadly its the high powered bikes that turned the MTB community against us. All the great MTB trails in Michigan ban e-bikes completely. I got on the MMBA forum and the hostility against e-bikes was very concerning. So now I have a way to experience my youth again but I'm not allowed to ride anywhere except street or sandy motorcycle trails. I hope the opposition to e-bikes softens in a few years but I suspect they will be treated more like motorcycles instead.
Parks are shiet anyway, ride natural trails.

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Chalo   100 GW

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Re: How much power is too much for a standard mtb?

Post by Chalo » Aug 05 2018 11:21pm

Tommm wrote:
Aug 04 2018 9:12pm
Sadly its the high powered bikes that turned the MTB community against us.
Some of us predicted it all along.

The thing to hope for is that electric motorcycles get treated as motorcycles, and electric bicycles get treated as bicycles.
This is to express my gratitude to Justin of Grin Technologies for his extraordinary measures to save this forum for the benefit of all.

2old   100 kW

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Re: How much power is too much for a standard mtb?

Post by 2old » Aug 05 2018 11:40pm

I'm in Orange County, CA riding on terrain that either specifically permits e-bikes or doesn't prohibit them. Individuals on the local forum have excoriated e-MTB from the beginning, but in three years of riding and meeting many MTB riders I haven't had a negative experience. Don't let the couch potatoes on forums reflect negatively on all riders. Probably they're 0.01% of the MTB contingent; the 99.99% you meet on the trails respond much differently.

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Alan B   100 GW

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Re: How much power is too much for a standard mtb?

Post by Alan B » Aug 06 2018 12:44am

Many on the trails are angry but won't say anything. Some will yell at you. Don't assume you know what they are thinking.

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Ivanovitch_k   10 W

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Re: How much power is to much for a standard mtb?

Post by Ivanovitch_k » Aug 13 2018 4:24pm

Tommm wrote:
Aug 04 2018 7:59pm
KMC E chains are over 2x more expensive... I would be interested if they last 2x longer though.
I don't know where you see them this pricey ? X11-E are ~27eur vs ~21eur for X11.93, in both 118 links. Not 2x between the two.

agreed on the cassettes tho, they might not shift as well as their brand-name counterparts, but ey, who really cares.
Last edited by Ivanovitch_k on Aug 13 2018 4:29pm, edited 1 time in total.
BBS'ed Radon ZR Team 8:
BBS02B 750W - DPC750C - 48V 17.5Ah GA shark - 11 spd 11-40 Shimano XT, 42T N-W Precialps CW, KMC X11e chain, Gearsensor, XT RD, XTR Shifter, F Saint Brake, R XT Brake, RT99 200/160 Discs, magnetic shutoff, DT Swiss X1900 QR9 wheels, Manitou M30 air fork, 2.4" slick balloon schwalbe Super Moto X tires @2 bars, Suntour NCX suspension seatpost, ergon SFC3 saddle, ergon GP3 grips, Supernova M99 Pro + E12 Taillight

Tommm   10 kW

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Re: How much power is to much for a standard mtb?

Post by Tommm » Aug 13 2018 4:27pm

Ivanovitch_k wrote:
Aug 13 2018 4:24pm
Tommm wrote:
Aug 04 2018 7:59pm
KMC E chains are over 2x more expensive... I would be interested if they last 2x longer though.
I don't know where you see them this pricey ? X11-E are ~27eur vs ~21eur for X11.93, in both 118 links. Not 2x between the two.

agreed on the cassettes tho, they might not shift as well as their brand-name counterparts, but ey, who really cares.
I buy my .93 chains from aliexpress at $17 delivered. The ebike specific ones aren't on ali, and they are indeed 27 eur in europe.

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