Convert 2 Classic MTBs to eBikes

Hi,

Here's the background:

I'm planning to convert 2 classic fixed 26ers to ebikes. Both are in pretty good condition, as my wife and I used to ride often and I have always wrenched my own machines. Both are all original and are a 1990 Diamondback Apex and a 1989 Specialized Stumpjumper. I ride the Apex and my wife rides the Stumpy. I want to hot rod mine, ride cross-country singletrack, and use it to learn trials techniques and transfer those skills over to my DS motorcycles (Wheelie anyone?) My wife is more about gravel grinding with some occasional singletrack when needed. We live on top of a pretty steep and long hill, so we need the power at the end of the day to get us back up and home. I think I've decided on using BBSHDs for the power upgrades and for the HD reliability. Budget is in the $1000+ range for all upgrades for each bike.

So the questions are:
1) Are these classic cromoly frames a good starting point? I know from experience that those frames are very strong and lively frames, even if a bit on the heavy side, so I think they are a good place to start.
2) Downhilling on either over rocky singletrack (i.e. creekbeds and runoff tracks) always left my arms buzzing and my hands tingling from the vibes. Should I a) immediately look for front shocks (might be difficult due to the 1" steerer tubes), or b) just build 'em as-is and ride them, or c) start with a good used hardtail or FS bike?
3) As I am planning to have quite a bit of power on tap, I think the brakes will need some attention. Am I right, or will the OEM cantilevers be adequate?
4) If I do need to upgrade the brakes, should I upgrade to a) v-brakes, b) mech. discs, or c) hyd discs?
5) Does anyone have any other general or specific advice I should consider that isn't readily available in the other build threads?

Thanks,
Kubcat

With the BBSHD, you'll be travelling fast enough that a brake upgrade is wise. Unless your frame has caliper mounts, or you have access to welding, you'll have to buy a fork with mounts for the front, and stay with rim brakes in the rear. I have a 2004 Diamondback hybrid where I added a BBS02. The front fork has disk brake mounts, so I put on a Avid BB7 caliper. It seems adequate. If it doesn't work for you, a 180 mm rotor is the next upgrade, followed by a hydraulic caliper. A rotor is 10 bucks. Shimano calipers (a pair) cost me 80 bucks. I have yet to try either.

I put inexpensive $69 RST Capa shocks on a Trek 830 (hub motor). That was a 1" steerer tube. I doubt there are any air shocks for 1" steerers. That bike sees nothing worse than grass trails. Expect the front of the bike to rise 3" or more with the suspension fork. Seemed to ride slightly different initially, but I got used to it in a day.

You start with what you have, typically. Nothing wrong with the frames on either bike.

But you are clearly a guy who needs to go buy a good FS MTB, someday. I don't know how rough your trails are. I live in the rocky mountains, and single track around here is often enough a rock staircase. You just wreck wheels and such, riding it hardtail.

You will really love a good 200 mm travel shock, but your bike was not designed for it, so put one on your current frame, and it will ride funny. So don't do that.

I'm assuming, that you won't ride in the Chicago suburbs. There, you could get used to the different ride. It just becomes a cruiser. Don't ride a cruiser on difficult single track.

I agree with all of the above. In fact, I would say you need a better donor bike to start with.
Since you haven't filled out your profile, we don't know where you are, but out West Craigslist usually has plenty of 2003 and up used MXB's to look at.
Bikes in these years are new enough to have disc brakes and full suspension and although they are considered obsolete by the serious MB guys, they make great ebikes.
A little extra weight and 26" wheels are no problem for an Ebike. Extra large tires can be installed w/ no concern about how they roll.
Used mountain bikes are the best value in ebiking.

Thanks for the feedback. Does anyone want a good deal on some old school fun? I have two bikes for sale?

So if I am not going to use my current old frames, and I will have to start from scratch, the question now is to buy a used donor bike with the grade of components the BBSHD would require, or do I do a frame up build? I'm pretty sure the frame up build would cost more than waiting for the right CL deal to come along over the winter months, but either way I can wrench to my heart's content. For now I think I'll research both approaches.

If I'm going the frame up route, I think I will look for a purpose built frame and get the Bafang Ultra G510 motor with the straight cut metal gears. The FS frames seem to be in the $750 range on ebay, but I found this one on Alibaba.
https://www.alibaba.com/product-deta...20083e5fiZBQCn

I have never purchased anything direct from China, so I'm a bit nervous about it.

Has anyone seen these frames in US/Europe for under $500? I want aluminum, not CF.

AFAICT, we're still waiting for "Ultra" frames to be available in the "west". Also, even with a $500 frame your budget will be increased to $2000+ with a good fork and rear shock plus conversion parts. I did a frame up steel hardtail (Fox fork) plus BBS02 for about $1500 and have ridden if for four years off road. However, more expensive if you need full suspension.

How do you like the hardtail? Any regrets? Any plans to upgrade to FS?

I am on the fence about FS vs hardtail. Even though I know that the motor can overcome the suspension compression and expansion inefficiencies on aggressive climbs, those inefficiencies are still there, sucking down the juice.

At my age I'm not a downhill bomber anymore, and am really targeting a more cross-country bike that I can also use to practice low speed control and balance.

Any and all thoughts are welcome.

Thanks

For me, the hardtail plus Thudbuster are adequate, but I'm not a downhill bomber either and ride relatively tame as opposed to very gnarly trails. I have a FS donor bike (languishing in the garage) that may receive an "update" someday, but I'm not in a rush.

Umm,, I didn't say don't build with your current bikes. I just said build on them, and then keep an eye out for something better if you ride really tough trails. As others said, look for something used in decent shape. Meaning, a FS MTB that sold for 1500 or more new, but you get it for 500-700. Less if it needs a new fork or shock, or wheels are trashed.

What you have may be quite ok for what you do. I got no idea how hard you ride, how hard the trails are, or how much harder you might ride once the motor helps. You can always still do the hard riding on your motorcycle.

Your bikes now are fine if your trails are not that rocky, or you are not dropping down staircases of rocks, or you tend to ride relatively easy trails with just a few tough spots.

When you start pinch flatting your rear tire, that's your signal to spend on new bikes with full suspension.

Dogman, I appreciate your input, and I was thinking along the same lines, until I started learning about how much wear the high torque mid-mount motors can cause in the drivetrain of a bicycle. Given that I want to buy the motor for growth into the sport, that means high torque and high wear, so using the 30 year old drivetrain is probably not the right starting point, even if the frames would easily stand up to the abuse.

I'm now thinking of following your advice for my wife's bike with her old frame and the BBSHD in a 750W road legal configuration. For my bike, I'm thinking a bottoms up bafang ultra with a purpose built frame, belt drive and IHG, all designed to handle the driveline torque. The savings on her bike, which will be built to her riding style and won't require any compromises for her, will be redirected to my budget, so overall we may still be in the sub $4k range for both bikes.

I'm now leaning to a hardtail on the frame-up build, but really unsure about what to base that conclusion on other than budget.
The majority of the time, we will be riding together, which means, in order of frequency, long distance (50 miles) gravel and paved road rides, afternoon rides (2-3 hours) flowing forest trails with roots and some rocks, and only very occasionally some downhill bombing runs that she might opt out of.

What I want to end up with is bulletproof, well balanced, (relatively) light, and reasonably comfortable even over some bumpy conditions for a few hours at a time. Does this sound like a hardtail will fit the bill, or should I go with FS?

kubcat said:

Given that I want to buy the motor for growth into the sport, that means high torque and high wear, so using the 30 year old drivetrain is probably not the right starting point,

Click to expand...

If they aren't already worn out, drive components of that period will far outlast today's new hotness. And then you can replace the worn parts, because bikes that age don't usually have goofy nonstandard parts.

A new MTB is the clear choice for play riding on manufactured trails, because that's what they're for (other than maximizing profit). A 1980s MTB isn't for any one kind of riding; they were figuring it what to do with them as they went. But they were mainly for riding, not jumping off of things that were specifically constructed to be jumped off of. So if you're more interested in riding different situations than you are in hurtling downhill or catching air, you could do a lot worse than an old rigid MTB.

1) Are these classic cromoly frames a good starting point? I know from experience that those frames are very strong and lively frames, even if a bit on the heavy side, so I think they are a good place to start.

Click to expand...

They are a good start.

What is especially hilarious is that the new hotness is 'gravel bikes', which are really just a re-hash of early era mountain bikes, but with drop bars and 700c wheels instead of straight bars and 26 inch wheels. The advantage of old MTB and gravel bikes over modern MTB is that they are simpler, more efficient to pedal, and can be fitted with fenders and frame bags or racks to make them into 'adventure' or 'touring' bikes easily. They are much more suitable to cross country and long distance riding then a lot of modern MTBs.

Not good for modern more difficult tier mtb trails with jumps and all that stuff, but on mild to medium trails I am sure they can still be fun.

They are really very terrific bikes.

2) Downhilling on either over rocky singletrack (i.e. creekbeds and runoff tracks) always left my arms buzzing and my hands tingling from the vibes. Should I a) immediately look for front shocks (might be difficult due to the 1" steerer tubes), or b) just build 'em as-is and ride them, or c) start with a good used hardtail or FS bike?

Click to expand...

Get the biggest tires that can fit. Nowadays 2.5 and 2.6 inch tires are common and easy to find. Also big foam grips might help.

Don't bother with upgrading to suspension fork. Even if you do find a rare 1 inch suspension it will be very low quality compared to modern stuff and it'll jack up the geometry of the bicycle. Suspension forks are much longer then rigid forks. It's possible to go the other way (suspension to rigid) easily because they make longer then normal forks (suspension adjusted) for that purpose.

Nothing wrong with hardtails or FS. It's all personal preference. If you want to go that route then do so.

3) As I am planning to have quite a bit of power on tap, I think the brakes will need some attention. Am I right, or will the OEM cantilevers be adequate?

Click to expand...

Cantilevers CAN be made to work. But they are fiddly. You have to understand the angles and linkages and such things. And they are dangerous unless you have the original reflectors on or have fenders as if the cable lets go the 'Y' connection can fall on the tire, get caught, and break your face on the ground.

4) If I do need to upgrade the brakes, should I upgrade to a) v-brakes, b) mech. discs, or c) hyd discs?

Click to expand...

V brakes (linear pull or direct pull) use the same mounting posts and are much less fiddly. Shimano or Tektro brand V brakes are the ones to get. The upgrade requires you to purchase matching braking levers as the pull ratios are different.

Kool stop 'mountain pads' are a nice upgrade. I like the dual compound.

5) Does anyone have any other general or specific advice I should consider that isn't readily available in the other build threads?

Click to expand...

Go over the bike and check for corrosion. If they haven't been rid in a long time factor in the price of new pads, new cables, and new chain. Make sure everything spins well and bearings are not crunchy or otherwise need servicing. I'd go and pull out the handle bar quill and seat stem and put some grease on those. Just go over the bike and give it a nice refresh if it hasn't had it for a while.

A few upgrades (like new seat, h-bars, larger pedals) are a good investment, but if you want to do major upgrades to try to modernize it then it's not going to be worth it financially. Much cheaper to buy a bike off of bikes-direct or something like that.

hard tail is alright
lots have a good suspension seat post which is good to have
fat bike tires soften the cushion
if your of average weight, 100-250lbs then a fs is good to have
havent seen much for 350+lb guys for suspension.
mind any suspension fork will do, but a good one its the rear for heavy fat guys

Let's say it will never be a motorcycle.
Frist build your wife's bike linear brakes with Kool stop pads. Mid drive and trangle battery and an air fork. That's a start maybe a thud buster and a newer shorter version.
Then after learning real life - find out your needs.
Go down to a big ebike store and try some out where do you live ?
.

Replacing the Fork to a Suspension Fork , and upgrading the Brakes will probably be as expensive as finding a good deal on a newer used full suspension or newer steel hard tail bike with Shimano Hydraulic Brakes included . ( note used bikes with Avid brakes need too much service on the brakes meaning $$$ , so count on just throwing them out unless you can do the fluid Dot 3 change and maybe even some seals as well , your self .

Go to youtube to see how to service avid brakes after seeing how much work it is , you will probably want to get Shimano's to begin with , Avid BB 7's mechanical disc brakes are very easy to install and work on.

You can go back to 2003 models but often you can get a good enough deal with a 2009-2012 FS 26 inch wheel bike because , right around that time most bike MGF's went to tapered head tubes and thru axle frames so hardly anyone wants a straight headtube and /or dropouts any more . You will see sellers often trying to sell for more than the bike is worth , so go to bicyclebluebook.com to find the real value , and also find out if the bike was one that mostly sat in the garage and not used on any down hill gnarly trails.

kubcat said:

The FS frames seem to be in the $750 range on ebay...

Click to expand...

This is an old thread and I am guessing your project is complete.

That said...

My bike riding days are over and I have an FS titanium SevenCycles frame that is looking for a home.



Also an FS Ellsworth Isis that is currently an exercise bike