First build questions: commuter road ebike (mid-mount)

Hi all. My experience with ebikes goes back a whopping 3 weeks, when I test rode a [strike]tank[/strike] Stromer ST2 and within 10 minutes, I was hooked. I quickly found the price-performance of commercial ebikes to suck (made suckier by their proprietary designs). A couple conversations with @mystryda convinced me to go the build route. I'd like to share my thinking to date and get your advice.

My goal is to use an ebike for my 2-3x/week, 32 mile (each way) work commute in the DC area-- a mix of flats and rollers. Nearly the whole route is paved, in good condition, and 80% is on bike lanes or paths. On my current road bike, the commute is 2:05 one-way and I'm looking for the ebike to get it down to 1:30 or below, which the Stromer proved was possible.

I'm 6', 180 lb, and I want to cruise 28-30 mph on flats with moderate pedaling. I’d like to use max 70% of the battery's charge range for my 32 mile commute, which means about 32/0.7 = 43 mi total range from the battery. Bike weight goal is mid 40s lb with battery, mostly so I can lift the bike without throwing my back out but also to help with efficiency. A little heavier is OK if need be.

The http://kreuzotter.de/english/espeed.htm tool estimates I put out about 180 W average on my current roadbike, and that I’d need 580 W average on my ebike to hit the 90 minute goal. So the motor needs to make up the 400W difference, requiring 600 Wh over 90 mins, which seems achievable with a 48V 17.5 Ah battery.

I'm expecting to spend about $2.6k (total-- new bike, motor kit, battery, lights, rear rack, etc.) but can afford a little more. I can assemble, crimp, and solder, but no heavy DIY customization.

I’ve got a couple old bikes, but I want hydraulic brakes, so I'm going with modern models. I found nothing on Craigslist in my area so I'm starting with a new bike.

My basic design so far is:

• $600- $1k for an Al road bike or hybrid with 700mm x 32 - 38 tires + hydraulic discs + threaded BB.
  • will add torque arms if needed.
  • Internally routed cables sound appealing so I don't have to re-route them across the bottom bracket during motor install.
  • Some of these bikes come with carbon forks which I assume is OK since Luna's own KHS Grit 220 bike comes with them?
  • 11T smallest rear gear so I can go fast-ish on downhills
• BBSHD kit with standard 750W programming, optional chainring, 48V 17.5 Ah Panasonic GA hard case battery on the downtube, charger. Should total ~$1400
• Chainring: Luna Eclipse 48T. I think a 52T would work better for flats/rollers if they're available.
• Charger with selectable 80/90/100% limit
• Other stuff: gear sensor=yes, PAS only=yes, throttle=no, display=DPC-18
• I plan to look into a Thudbuster after the build is complete.

Some Questions:

First, appreciate any comments and suggestion on the above design.

For the bike purchase, any suggestions for things to look for, apart from riding comfort, bigger brake rotors, torque arms if Al dropouts, and fender/rack mounts?

Is a lightweight steel bike (e.g., Jamis Coda Elite) better than Al, assuming they both are mid-20s lbs?

I haven’t seen much in ES about PAS lag/response time of the BBSHD. I've test ridden some commercial ebikes that had huge (felt like forever but probably ~1 sec) motor cut-in/cut-out lag, which sucked. What's the BBSHD like?

The hydraulic discs on these bikes are almost all 160mm. Is that sufficient? I'm thinking of starting with them and upgrading if they don't feel strong enough.

Is suspended fork worth the weight and "maintenance" for comfort and to reduce impact on an Al frame? I'm thinking it's not needed for road-only riding with mid-30s tires.

Has anyone with a road ebike tried aero bars? It seems that would help with efficiency in the flats, at least while on dedicated bike trails.


I'm super excited to nail down my design and put in my order, so thanks in advance!

Rich

You mention a worry about aluminum dropouts and torque arms, but with a BBSxx I don't think the dropouts are an issue. The BBS02 is a little smaller and lighter and cheaper than the BBSHD and would probably be adequate for your needs, but the BBSHD might be best for long term reliability.

Good luck with your build.

EDIT: And welcome to the forum.

Thanks. Yeah, I'm thinking BBSHD for the reliability, to ensure plenty of power to meet my speed goals, and I understand they run a little more efficiently at the same load as the BBS02. Worth the extra few pounds.

About the torque arms-- that's what I'd like to learn. If they're really overkill, then it's a step and an expense I'd love to avoid.

Rich

If you were planning on using a hub motor instead of the BBSHD crank drive you would need to learn about dropouts and torque arms. Hub motors typically have an axle with two flat sides that fit tightly into the dropouts, and the dropouts have to prevent the axle from twisting when the motor runs. If the axle twists not only will the wires that go into the motor be damaged, but the dropouts can break and the wheel can come out, potentially causing a bad wreck. Torque arms are made to help prevent the axle from twisting when torque from the motor is applied.

Anyway, a properly installed BBSxx will be resting against the down tube on your bike, which prevents the BBSxx from twisting at the crank axle when the motor is running.

Thanks for explaining that, makes perfect sense now. One less thing to have to deal with.

Rich

I'm still a beginner on the road to a BBS02 build of my own so I won't offer e-bike specific advice. But definitely decide if you can do a flat bar hybrid instead of a drop bar road bike. On long rides, drop bars can be nice but on a properly fit flat bar (maybe with bar ends if you want) should do okay. The reason I say that is you can get a lot more for your money with a flat bar. I sold Specialized and for a grand now you can get a Sirrus with 10 speed Tiagra, hydraulic Tektro Flow brakes. Also For a grand you can get a Specialized Diverge (hybrid with drops and road geometry basically) with 8 speed and mechanical discs. Both with carbon forks. I think the Allez you can come closer but still the flat bar is a "better" deal if you don't need the drops.

Anyway I'm not advocating Specialized, that's what I have experience with so that's my example. I think they're great we'll designed bikes, but you absolutely do pay a not-insignificant amount for the name...also with Trek et al. But no matter what brand, the basic idea above stands. I stress again that a flat bar should be considered only if it will be comfortable, because that's most important.

I would not get a suspension fork, but that's a personal decision. It's my opinion that you do not get anything decent until a lot more than $1000, it's just a true anchor on the front that just makes the brake feel a little vague due to bushing play. A carbon fork would be great, aluminum fine, steel fine just heavy.

You probably won't need to change the rotors, definitely not the rear. If you want to swap the front go ahead and buy a 185mm adapter and new rotor but be advised on possible potential warranty issues with the fork...personally I wouldn't hesitate a second but just a caution. I'd recommend trying new good brake pads if you're unimpressed as stock brake pads are rarely the best (particularly on Tektro/TRP I find) you can get.

Sorry if you knew all this... just putting it out there if it can help you even a little.

Edit: Dang, so Giant bikes has the Escape which you can get for $680 with Shimano 9 speed and hydraulic Tektro, carbon fork. All Shimano 9 speed is great, I have it on 3 bikes. Personally I think that's a great deal.

Okay good luck!

uncleknoppie said:

Hi all.......and get your advice.

Click to expand...

Why thank you, I will give it to you.

My goal ......32 mile (each way) .......flats and rollers. ......the Stromer proved was possible.

Click to expand...

All e-vehicles mostly depend on stored wattage, aka how much amp hours your battery has, and how much you charged it up. Not fully charging your battery will make it last, but that is a conversation for another time.

...I want to cruise 28-30 mph on flats with moderate pedaling.......

Click to expand...

That sounds like 48v or higher. Just remember crashing at 30mph hearts really bad!!!

I’d like to use max 70% of the battery's charge range for my 32 mile commute

Click to expand...

,

That sounds like a bigger battery then you might think. A light bike and you could easily use 25 watts per mile.

.... so I can lift the bike without throwing my back out but also to help with efficiency. A little heavier is OK if need be.

Click to expand...

If you have your battery in a back pack then your bike will be lighter. Motors are full of copper. Copper is heavy.

.....So the motor needs to make up the 400W difference, requiring 600 Wh over 90 mins, which seems achievable with a 48V 17.5 Ah battery.

Click to expand...

Every estimator I have used was off the target, or hard to use. Think like 25 watts per mile. That covers cold, wind, hills and other factors.

.......crimp, and solder, but no heavy DIY customization.

Click to expand...

Then you better be open to learning because e-bikes always need maintenance.

I’ve got a couple old bikes, but I want hydraulic brakes, so I'm going with modern models.

Click to expand...

Don't get locked into hydraulic brakes. They can be an oily mess and don't do any more for stopping then cable brakes. I roll around on a 80lb e-bike with v-brakes and can stop very quickly when a cager try's to munch me.

Is a lightweight steel bike (e.g., Jamis Coda Elite) better than Al, assuming they both are mid-20s lbs?

Click to expand...

My current e-bike is Al, but I think steel is a softer ride.

I haven’t seen much in ES about PAS lag/response time of the BBSHD. I've test ridden some commercial ebikes that had huge (felt like forever but probably ~1 sec) motor cut-in/cut-out lag, which sucked. What's the BBSHD like?

Click to expand...

I don't do PAS, but lag also is part of the batteries ability to deliver juice. RC lipo will cut your lag time, and if handled properly will give you great satisfaction. However if not handled properly, it will burn your house down...literally. Lag is frequently a battery issue.

Is suspended fork worth the weight and "maintenance" for comfort and to reduce impact on an Al frame? I'm thinking it's not needed for road-only riding with mid-30s tires.

Click to expand...

Before I got suspension every pot hole I hit felt like a bomb going off underneath my bike. I believe in suspension!!!

Has anyone with a road ebike tried aero bars? It seems that would help with efficiency ......

Click to expand...

Yes it will help with efficiency just like any other aero equipped bike. Just know that your e-bike will be heaver then a pedal only bike, and it will go faster and take longer to stop, so you will need to be very careful with controlling your bike while in aero position.

Good luck with it!!

JDMopar said:

On long rides, drop bars can be nice but on a properly fit flat bar (maybe with bar ends if you want) should do okay. The reason I say that is you can get a lot more for your money with a flat bar.

Click to expand...

Yeah, I've since started shopping for bikes and the "commuter bikes" are generally great value (including the fact that its end of season). But I've ridden flatbars and I find them rather uncomfortable. Bar-ends would help, by they can only raise your hands up?-- seems not very aero. Long-term, a more comfortable or more aero solution will be important.

I own a 2015 Giant flatbar roadbike with hydro brakes and had the LBS switch out the flatbar for 1" diam bullhorns. They had trouble getting the levers and shifters on (I understand why now, that flatbars are 22mm), but they managed to do it. The levers/shifters are mounted near the headset, so can only be operated from there, not from the bullhorn part. That works well enough for me on that bike, but for an ebike, I think you'd always want your hands in a brake-ready position at all times.

JDMopar said:

I would not get a suspension fork, but that's a personal decision. It's my opinion that you do not get anything decent until a lot more than $1000, it's just a true anchor on the front that just makes the brake feel a little vague due to bushing play. A carbon fork would be great, aluminum fine, steel fine just heavy.

Click to expand...

Thanks, that really helps.

JDMopar said:

If you want to swap the front go ahead and buy a 185mm adapter and new rotor but be advised on possible potential warranty issues with the fork...personally I wouldn't hesitate a second but just a caution. I'd recommend trying new good brake pads if you're unimpressed as stock brake pads are rarely the best (particularly on Tektro/TRP I find) you can get.

Click to expand...

Yeah, I learned that bigger pads place more torque on the fork, potentially breaking its design envelope.

JDMopar said:

Sorry if you knew all this... just putting it out there if it can help you even a little.

Okay good luck!

Click to expand...

Very helpful, thanks!

e-beach said:

...I want to cruise 28-30 mph on flats with moderate pedaling.......

Click to expand...

That sounds like 48v or higher. Just remember crashing at 30mph hearts really bad!!!

Click to expand...

Yes, I was able to rent the Stromer and commute to work on it a couple days. I learned to respect 30 mph. You have to be very focused while cruising. It's like riding downhill on a roadbike for the entire commute.

I’d like to use max 70% of the battery's charge range for my 32 mile commute

Click to expand...

,
That sounds like a bigger battery then you might think. A light bike and you could easily use 25 watts per mile.

e-beach said:

.....So the motor needs to make up the 400W difference, requiring 600 Wh over 90 mins, which seems achievable with a 48V 17.5 Ah battery.

Click to expand...

Every estimator I have used was off the target, or hard to use. Think like 25 watts per mile. That covers cold, wind, hills and other factors.

Click to expand...

I understand. Trying to look at the question different ways, to confirm I'm not crazy way off. Another one was that on the Stromer commutes I had "10%" charge left (whatever that means) upon arrival. The Stromer's battery is rated at the same 840 Wh as the one I'm considering, and that bike has 500W DD, which is less efficient than mid-mount? With a more efficient battery and lighter bike, I should do better, everything else being equal?

e-beach said:

.......crimp, and solder, but no heavy DIY customization.

Click to expand...

Then you better be open to learning because e-bikes always need maintenance.

Click to expand...

Good point. For now, I'm just worried about getting through the build. Once I fall in love with riding it, I'll be happy to figure out the other stuff.

e-beach said:

I’ve got a couple old bikes, but I want hydraulic brakes, so I'm going with modern models.

Click to expand...

Don't get locked into hydraulic brakes. They can be an oily mess and don't do any more for stopping then cable brakes. I roll around on a 80lb e-bike with v-brakes and can stop very quickly when a cager try's to munch me.

Click to expand...

I hear you. And you can wire up mech brakes however. It's going to be a challenge making hydro brakes more aero, as drop-compatible levers are very expensive. So advantage to mech brakes.

e-beach said:

I haven’t seen much in ES about PAS lag/response time of the BBSHD. I've test ridden some commercial ebikes that had huge (felt like forever but probably ~1 sec) motor cut-in/cut-out lag, which sucked. What's the BBSHD like?

Click to expand...

I don't do PAS, but lag also is part of the batteries ability to deliver juice. RC lipo will cut your lag time, and if handled properly will give you great satisfaction. However if not handled properly, it will burn your house down...literally. Lag is frequently a battery issue.

Click to expand...

Thanks, very informative. Not a big fan of the risks of lipo.

e-beach said:

Is suspended fork worth the weight and "maintenance" for comfort and to reduce impact on an Al frame? I'm thinking it's not needed for road-only riding with mid-30s tires.

Click to expand...

Before I got suspension every pot hole I hit felt like a bomb going off underneath my bike. I believe in suspension!!!

Click to expand...

I'm very familiar with my commute route so I should be able to slow down for the few rough patches. So I think I'm going to bet on big tires (compared to roadbike) and no suspension.

e-beach said:

Has anyone with a road ebike tried aero bars? It seems that would help with efficiency ......

Click to expand...

Yes it will help with efficiency just like any other aero equipped bike. Just know that your e-bike will be heaver then a pedal only bike, and it will go faster and take longer to stop, so you will need to be very careful with controlling your bike while in aero position.

Click to expand...

Yes, I definitely gained a lot of respect for that while renting the Stromer.

e-beach said:

Good luck with it!!

Click to expand...

Thank you, super helpful!

GEt used alum bike, full suspension. Get BBSHD. Get about 15 ah. Get 42 tooth front gear. Limit your PAS to three, MAYBE four. Use thinner tires, than dirt. You will be limited to 26 mph, but it is safer, more comfy and relaxing, and easier on motor.