Help with part selection

[J84]

I’m building a bafang ultra bike.

I joined a Emtb forum but most weren’t very supportive of anything over 250w, so I thought I’d try here.

I’m about to buy suspension and tyres and need some help.

Everything I read on the last forum said that fat tyres were a bad idea. They might be on a 250w mountain bike, but are they on a 1000w bike that will have mixed use on the road and woodland trails?

I was going to buy a Fox 38 Float Factory E-Tuned Grip 2, but I’m beginning to think a coil fork might be a better idea for a bike that’s used on the road a lot?
I don't mind the additional weight. Am i correct in thinking extra weight will make the bike feel more stable at speed?

Thanks, J

 

[lnanek]

Yeah, fat tires are a current fashion trend in the motorcycle world. The cycling world still kind of makes fun of them, though. Theoretically you get a little better stopping power and a little free suspension from them, but everything else is worse, including top speed. If your bike has real suspension, it likely doesn't need the cheap hack of fat tires to provide some cushioning otherwise, so you are free to go with better performing thinner tires.

 

[Wattman]

It's complicated but to simplify, you can extrapolate from world class mountain bikers. They aren't on fat bikes on trails because of:
1. weight
2. aerodynamics
3. they don't need the added footprint for traction. You won't be shredding off road faster than top mtb riders even with a motor.
On smooth road, you don't even need mountain bike tire width other than for ride comfort if building a hardtail versus full suspension bike.

You can also extrapolate from higher power off road motorcycles. They aren't on fat aka 4" wide tires either other than dual sport with much higher horsepower.

For Bafang Ultra power, 2.25 tire or standard issue mtb tire width is fine.

As to coil versus air shock, a nice air shock is a bonus off road but on smooth pavement a coil shock is fine.

What frame are building with?

If you are a performance rider, fit to the bike is king. Choose your frame size carefully in particular if you come from performance bike riding. Many lose this concept and they could be more comfortable on the bike...if you want comfort and good handling and even good pedal power on the bike. I have a 29'er with BBSHD and just love the bike. Ultra motor is nice because it has torque sensing of course but doesn't fit as many frames of course because of its flange mount which is the point.
I would suggest UART versus Canbus for your motor/controller...Ultra motor is sold both ways.

Best of luck with your build. To me, this level of power on a bicycle is the way to go. A BBSHD bike on a more generic frame is a great riding experience but a custom Ultra build should bring you many smiles per miles.
Problem with Ultra custom frames is many times you are locked into a given battery...many times proprietary unless you want to build your own within the downtube of the bike which can be challenging. Battery cell integrity is paramount and many downtubes are volume limited for adequate amp-hrs.

 

[E-HP]

The 20" fat tire ebikes are pretty bulky, but still fit in ok on the trails. The 26" fat tire bikes, ebike or pedal, are just huge and look out of place anywhere but the beach. Sort of like driving a monster truck around the neighborhood, not the intended application (other than the fad aspect). But, on sand, that's where they have a big advantage. I see maybe 80 ebikes in a day, and maybe 2 will be 26" fat. A few folks still ride the Rad fat bikes, and a few ride the Aventon fat bike, which is pretty popular and does 28mph, which isn't too bad for factory.

PS. my 2.8" knobbies are now bald and need to be replaced, but I'm enjoying the silence, and the increased range and speed. I'm tempted to put on some hookworms, but I do about 2/3 1/3 street and offroad.

 

[biphaeboh]

Around here (Alberta) the true fat tires -greater than 4" -are used on snow and ice for winter riding, usually with studs.
I find them awkward on dry trails, low enough pressure to soften the ride results in squirrely handling.
Personally for trail riding I like something between 2 and 3". I have an expedition bike with 3" 'plus' tires, the larger contact patch makes climbing on loose surfaces easier, although I don't know how power affects that - that bike isn't electrified.
If you are planning on significant pavement riding narrower tires are better.

 

[fechter]

My bike has 26" fat tires and I've been pretty happy with them. Great in the mud and sand (no snow around here). Rolling resistance is not significantly worse than skinny tires. Most of my riding is on dirt trails with some street on the way to the trails. One issue is less selection available for forks in that width and the frame needs to be a bit heavier to accommodate the wider tires. Also not so great for pedaling due to the wider bottom bracket, but I have a BBSHD, so pedaling is just to get some exercise. I've had it for 5 years now and never had a flat but I've gone through 3 sets of tires.

 

[biphaeboh]

Nice looking bike. I like it.

 

[J84]

Thanks for the advice. Fat tyres are not what I need. I’ll never see sand or much snow.

I’m leaning towards 29 wheels and a M Dengfu E22 (E23 if I was going fat).

I did consider the Markhor and Ansbern frames, but there is more information online regarding custom batts etc with the Dengfu which makes things easier.

The UART motor I was going to buy has been sold to someone else so I’m hoping titan pro get more back in stock.

Someone advised me that a Rockshox Domain would be a better fork choice for my use than the fox and it’s a lot cheaper. Don’t want to buy it a regret it later though.

BBSHD is a great motor but I want something a bit more subtle with an internal battery.

 

[J84]

Just ordered a UART M620.

 

[J84]

Been a few changes since I last posted.

Frame has arrived, ordered my forks and rear shock, bought a M600 with Luna V2 controller but turned out to be a scammer. Finally made my mind up with most of the parts I’m buying.

Considering bars with a higher rise than the Hopes have or a riser stem for a more upright riding position.

Buying bike parts isn’t as easy as I expected.


Motor: Bafang M560 (released May 23)

Battery: Custom

Frame: FM MD17 Carbon

Suspension fork: RockShox Zeb Ultimate 150mm

Damper: RockShox Super Deluxe Ultimate Coil

Brakes: Hope V4

Drivetrain: Microshift Acolyte CS-H083 12-46T

Wheels: Hope Fortus 35 29”

Tyres: Schwalbe Johnny Watts/Pickup Super Defense.

Stem: Hope AM 35mm?

Handle bars: Hope carbon 35mm?

Peddles: Hope F20

Cranks: Hope 155mm E-bike crankset

 

[marty]

Rolling resistance is not significantly worse than skinny tires.

Fechter says "One test is worth a thousand opinions"

Lets do a test. Remove motor from your Fat Tire Bike. Ride 10 miles. Now get a thin tire bike with pedals. Ride 10 miles. Suspect the difference will be something like turtle and rabbit.