Best wheel size for MTB style frame going fast on street?

[Moretorque]

My bike has 650's but was thinking of bumping it up to 29's, will this work better for higher speeds? How hard would it be to go from a 1200 watt peak motor to a 1500. I want to be able to pedal without Ghost pedaling and on flat ground maintain a speed of 30 MPH. can I just order a 29 rear wheel with a 1500 watt peak motor or no.

 

[99t4]

My bike has 650's but was thinking of bumping it up to 29's, will this work better for higher speeds?

Theoretically yes. IRL it is limited by available power, and aerodynamic drag. Tell the diameters of your 650 tire, and of the 29" tire you are going to run and we can calculate the theoretical speed increase. Also tell us the max speed displayed with the wheel spinning in air off the ground, and the max speed displayed when riding on the flat ground.

How hard would it be to go from a 1200 watt peak motor to a 1500. can I just order a 29 rear wheel with a 1500 watt peak motor or no.

Sure! In today's world, With enough money anything is possible!

 

[Moretorque]

Theoretically yes. IRL it is limited by available power, and aerodynamic drag. Tell the diameters of your 650 tire, and of the 29" tire you are going to run and we can calculate the theoretical speed increase. Also tell us the max speed displayed with the wheel spinning in air off the ground, and the max speed displayed when riding on the flat ground.


Sure! In today's world, With enough money anything is possible!

I want to do this without doing alot of mods, wondering if I could find a 1500 watt wheel that will work with the current electronics on the bike. If I have to do alot of work might as well build a new bike from ground up.

 

[RunForTheHills]

Usually, a frame is designed for a particular wheel size. Putting a larger wheel (and sometimes larger tire) than it was designed for will probably not work. Even if you manage to put it on the bike, there is the matter of toe overlap with the front wheel and your foot on the pedal. Measure before you buy. You would need to get a different frame and move the components over to it.

Many people buy used bikes on Craigslist to convert to ebikes. But if you did this, the used bike is likely to have better components than your current bike anyway. Given your height, you could benefit from buying a different frame. I know you think the frame fits you, but it doesn't. Just like airline seats, one size fits all frames aren't really meant to fit 6'4" people with long legs.

 

[Moretorque]

I have converted 2 26's to 29's and it turned out well, this frame comfort wise is perfect, I can keep it 650 but want a few more MPH. I am a 2xxl or even 3 when in leg length and barley a large in torso length so a short frame fits me great. This frame is a large and fits my torso the best ever in fit but I am putting a 450 mm seat post on it with 4 inch riser and then tall bars.

 

[RunForTheHills]

Was that conversion 29 in the front or both the front and back wheels? It wouldn't work on any of my bikes with 26 in wheels. Again, you should measure before you spend the money on a new motor and wheel. To go up to a 1500 watt motor, you will also need a new controller and display that supports 1500 watts. By the time you buy a kit to upgrade your motor and controller, you may as well put that kit on a better frame. One that has suspension that can more easily absorb the potholes and bumps at higher speeds.

Also, something to keep in mind is that for the same motor winding, a higher voltage will spin the motor faster. So 72V > 60V > 52V > 48V > 36V for speed. That said, you can get 30 mph out of 52V with common motors pretty easily. You have a 36V battery though.

 

[Moretorque]

I have a 48V battery, the 1200 watt 27.5 is a class 3 28MPH. That is the thing, for 369 this is the best deal I have ever seen. I put 29's on both front and rear but had to do a few minor mods to the 26 MTB bikes. If I put a 1200 watt 29 rear on the bike will that get me a few more MPH? Thanks.

 

[RunForTheHills]

Well, you can pick a motor and simulate it in the Grin motor simulator. You will need a controller that supports 1200 watts. You can pick one to simulate in the motor simulator as well. Motor Simulator - Web Tools - Resources

MTA: Here is an example, 48V battery, 25A controller, 26" wheel, 375lbs total weight, upright (mountain) bike. You can hit 30 mph at around 1200 watts. Motor Simulator - Web Tools - Resources

 

[gromike]

Those inexpensive DTC ebikes are built out of the cheapest parts, so you'll always be chasing your tail if you try for a reliable, higher speed ebike. I prefer to convert a quality used bike.
This beauty was $50. Added the Grin motor wheel and controller, and EM3CV battery.
Full suspension, regen & torque sensing, 30+mph on throttle. Great bike until motor broke.

 

[RunForTheHills]

I have a 48V battery, the 1200 watt 27.5 is a class 3 28MPH. That is the thing, for 369 this is the best deal I have ever seen. I put 29's on both front and rear but had to do a few minor mods to the 26 MTB bikes. If I put a 1200 watt 29 rear on the bike will that get me a few more MPH? Thanks.

It is a great deal for trying out ebikes to see if you will like them. You have already spent a lot of time and money modifying it to fit you and you are proposing to spend hundreds of dollars more to make it faster. It's will be far from a $369 bike by the time you are done and the end result won't be as nice as if you started with a quality used mountain bike with good components. You can usually pick one up in the $200 range or less if you are patient and look for a deal.

 

[Moretorque]

I just like the frame geometry of this bike, it really just needed the brakes fixed. I am just wondering if I put a 29 on the back could it get me a few more MPH over a 650 is all.

 

[RunForTheHills]

You don't need a larger wheel to go faster. People build fast bikes with 20" wheels. You could just get a controller with higher current output assuming your battery and motor can handle it. The motor probably can handle a little more. Did you look at the motor simulator output I posted above. A Clyte H3540 motor with 48V, 25A controller, and 26" wheels will do 30 mph.

 

[Moretorque]

Thanks.

 

[E-HP]

I just like the frame geometry of this bike, it really just needed the brakes fixed. I am just wondering if I put a 29 on the back could it get me a few more MPH over a 650 is all.

No, not necessarily. As mentioned, it depends on the motor. There’s usually enough info in the listing to tell you what kind if speed you could expect, but you never answered the questions from post #2, so hard to help without you providing info.

 

[n00b]

My bike has 650's but was thinking of bumping it up to 29's, will this work better for higher speeds? How hard would it be to go from a 1200 watt peak motor to a 1500. I want to be able to pedal without Ghost pedaling and on flat ground maintain a speed of 30 MPH. can I just order a 29 rear wheel with a 1500 watt peak motor or no.

29s, definitely, unless there's something bigger.
XL frames are better for going fast, too. Longer wheelbase.

 

[n00b]

Was that conversion 29 in the front or both the front and back wheels? It wouldn't work on any of my bikes with 26 in wheels. Again, you should measure before you spend the money on a new motor and wheel. To go up to a 1500 watt motor, you will also need a new controller and display that supports 1500 watts. By the time you buy a kit to upgrade your motor and controller, you may as well put that kit on a better frame. One that has suspension that can more easily absorb the potholes and bumps at higher speeds.

Also, something to keep in mind is that for the same motor winding, a higher voltage will spin the motor faster. So 72V > 60V > 52V > 48V > 36V for speed. That said, you can get 30 mph out of 52V with common motors pretty easily. You have a 36V battery though.

View attachment 382883

I bet I can get 30 mph out of a 36v battery. It's at 42v right now.
Thing rips. Final gear ratio is 58-18.
It certainly did, too:

That 37 is the mph. I been foolin' with the calculator and all. It says only 559 watts.
I have doubts about that. It's not the fastest, but it'll get up there.
I'm leaving the 36 volter on there. Do not care what the average says, I ripped downhill and then stopped and downshifted and
waited for traffic on the way back.

 

[n00b]

I just like the frame geometry of this bike, it really just needed the brakes fixed. I am just wondering if I put a 29 on the back could it get me a few more MPH over a 650 is all.

Changing the controller could get you a few more mph, probably.
And you should fix those brakes.

 

[Moretorque]

I am going to fix the gearing and I want the bike to go 30 when peddling hard and 25 when cruising.

 

[n00b]

I am going to fix the gearing and I want the bike to go 30 when peddling hard and 25 when cruising.

Just add a bigger chainring if you want to pedal and it's assisted.
Got a pic of your current chainring?

 

[Moretorque]

I just got a 11 tooth to replace 14 tooth .

 

[MxusMick]

From my limited experience with DIY ebikes, using the same voltage on various size rear wheel hub motors, 20" and 26", field tests showed faster excelaration side by side from the 20" which actually had no cranks or chain, flat ground. The ride with a 26" front wheel and a 20" rear wheel is better than good, true the pedals are lower but........ pedalling thru corners at 30 mph???? C'mon man