Oh yes, I do want to hear what you have to say; you're the expert with experience!
First of all lets acknowledge that several others in this group of mutually self-appointed experts just threw up in their mouth a little. This makes my day
. Wait did I say that last part out loud?
Some of what you say will lead to some more questions from me; I hope you don't mind. I'm the kind of person who wants to understand how things work, otherwise, I can't remember. I need to know the "why's" in order to get the picture.
Absolutely the best way to go about things. The more you know the less you'll want to take what someone else chooses to give you and tell you thats what you really wanted, and to forget about that other stuff on your shopping list.
As for a frame, finally, someone else who loves chomoly!
This seems the right time to leave my favorite observation on frame material here:
More seriously, I have alloy, titanium and chromoly frames. All of them have their strong points. Some have weak points as well. Old school chromoly has rather a lot to recommend it. Especially when it comes to an ebike platform where the stresses are high and chromoly's strength and forgiving nature outweigh its... weight. That is incidentally a theme of the ebike that cyclists generally take a while to get beat into their heads: The whole weight weenie thing has to be cast aside in favor of durability. This is why a cheapo Shimano HG400 cassette - pinned together steel - was once the epitome of ebike clusters, until SRAM decided to make their own out of tool steel (and charge $350+ for it). Now in 2024 we have more choices. The Microshift Advent X costs about $40.
My favorite bikes are chromoly, my Trek 520 touring and my Jamis Exile mtb. I thoroughly looked at all 3 Surly bikes you listed. Only one would fit and I can’t really see spending that for a frame when I already have many that fit and perhaps 2 or 3 that might work.
First question is, would you rule out a good aluminum frame?
Hell no I wouldn't. That road bike I pictured earlier is a Vitus 979 'duraluminium' frame from 1983, if I recall correctly. That was the first bike I built frame-up (in 1983), which explains the triple front and the straight block (it worked but definitely a learning experience I need not repeat). My next-most-recent build was the bike featured in this series:
You want to build an ebike, but the project seems overwhelming. Lets de-mystify the entire process, including planning, parts and perfecting the end result.
talesontwowheels.com
Its a 2000 Intense Tracer frame I rescued cheap on Ebay, and it is alloy. And maybe the most fun bike I own. Rigid and light. With the rigidity offset by the full suspension (and thats a 1999 Marzocchi Bomber fork I also rescued for that build). And of course my Bullitts are alloy-framed. Those bikes use super-rigid alloy construction, but since the bike is 8 ft long, flex creeps in naturally and its deceptively comfortable for an alloy frame with no suspension.
With that said, chromoly options are the best candidates for an off the shelf conversion. Since you are already sold on chromoly I'll spare the peanut gallery waxed eloquence as to why. Keep loving it. And keep an open mind, but not so open your brains fall out
. Alloy can work just fine if the planets align properly.
It seems that most of the ebikes, even high end, are made of aluminum. Granted, they are probably made of heavier tubing and more sturdily than non-electric bikes I would suppose. But I am a light rider.
Your body weight definitely offsets some of the factors that would lend one to favor alloy. Just remember the decision process is layered and your body weight is only one layer in the onion.
I have to say I'm not a fan of either of your two choices. I think they both are too old to make a safe ebike conversion. A lot of this has to do with the lack of disc brakes, but I am also looking at all of the parts on these bikes. I would say the Jamis is ideal IF it had disk brake mounts. But it doesn't. I would never build an ebike with any kind of caliper brake, even though I know some DIY'ers out there will say they have done it, and pooh-pooh the standard wisdom that any rim brake regardless of the flavor is not a long-term safe solution. Regardless of any good intentions to take it slow, the reality is an ebike is a faster animal with a fair bit of added weight to slow down safely and stop (and yes I know you are a very light rider). I've seen adjustable-angle stems like the Trek has give way under intense braking and as such I'll never trust them.
The Jamis is ideal in the sense it has a perfect down tube shape, and a real triangle with what seems to be plenty of room for a battery mount. Its also got frame bosses for a rack although the lower rear ones don't look particularly robust (I cracked my first steel ebike frame when a lower rack boss snapped that one time I overdid it and the frame was history with a fresh hole in the chainstay). I do love seeing a chain hanger on a frame again, though.
For both the Trek and the Jamis, I would out of the gate take it as a given the suspension fork will be retired in favor of a much better air fork. That 1999 Marzocchi I used on the red Intense was a miracle find in that it was 23 years old but appeared new... but even so it still needed all new seals. You can get a 'vintage' fork on ebay if you want to keep up appearances, or spend about $150-300 on an inexpensive or halfway decent air fork.
Also honestly for a modern ebike where you are going to be riding at speeds you otherwise never would be, with potholes rearing up at you a lot more quickly, I'd abandon any inclination to use ancient wheels, unless a pro has tuned them and signed off on their survivability (which will not help the poor pawls under the cassette body, or the cassette body itself). Otherwise... they won't survive. Simple as that. You'll start popping spokes too. Been there and done that, unfortunately. I know you don't want to go past 1.8-1.95 but at the least you should go a bit wider on rims to allow for a future BurroBabe who's gotten some e-experience under her belt and wants a ride less likely to rattle fillings and bash her lower back. At 62 my priorities in this regard are nothing like what they were when I was 22. Or even 52.
My other choice is a Jamis Exile mtb. It has a chromoly butted triangle frame. It's 13", has a Manitou Spyder fork which doesn't appear to have anything to attach a disc brake to. The rear stays have 2 drilled holes and another with a bolt in it on the inside of both sides. The front fork is about 16” axle to inside the top arch. Gears are 3 x 8, Shimano STX RC front crank and derailleur and the rear derailleur is just stamped “ integrated 8SK”. It also has stupid grip shifters which I cannot twist (My wrists are destroyed). I would need to change the flat bar to a riser with some ergonomic sweep as well.
Bikes like this from such a bygone era should be regarded as frame donors only. But in this case the frame is just a teeny bit too old given its lack of disk brake mounts. But its definitely a close fit. The drivetrain on this bike has no hope of working long term. You can see I think the same thing about the wheels (for 26" wheels my choice would be the indestructible SunRingle MTX39, or the AlexRims DM30, with the latter being a little narrower but only by a few mm).
It’s bottom bracket is 69mm wide, too narrow for the BBSHD according to Bafang’s website. I couldn’t find the other motor listed there. This bike has Sunrims CR18 and Parallax hubs. I’s lighter, without a rear carrier and with light street tires (also 26 x 1.95”) it weighs about 28.5#.
A 69mm bottom bracket is not at all a problem. The BBSHD comes in 3 widths: 68-72mm, 100mm and 120mm. The first size on that list would work just fine. Also the BBS02 is available in a 68-72mm width. 69mm is ideal.
I checked out the Microshift website to see the Advent X drivetrains. They don’t come in 8 speed but they do have other groupsets in 3 X 8 and 3 x 7. And I'm fine putting on a new group set that can handle the extra torque from a motor.
For a beginner build, you want the Advent X. Forget about the 3x systems. 8s and 7s systems are bottom of the barrel, qualitywise. It has been decades since anything was made that was 7s and not Walmart-level quality. You will be using a 1x as a mid drive will require a single front ring. Common wisdom is that a motor is so happy in a wider range of rpms that you need fewer gears. But for a cyclist, ideal cadence still rules and is unaffected by this, so unless you just want to throttle down the road you want 9, 10 or 11s. It so happens the Microshift Advent X is cheap, smooth, durable and effective. Here are two companion articles which go together on this subject. The first one gets into drivetrain options. Believe it or not 11s is ideal thanks in part to the 1x front limit, but 11s for a beginner is a lot tougher and much more expensive than doing 10s now that there is an inexpensive, quality matched drivetrain (derailleur, e-shifter, rear cluster and chain), just waiting to be installed with minimal investment. I put a wider (11-51T) 11s Sunrace CSMX8 cluster on my Big Fat Dummy last month and just the freaking cassette ran me $130. 9s is an option as well and 9s used to be the DIY builder's smart choice, but the Microshift 10s system is a jewel.
And yes in this first article I do mention 8s systems that are worth a damn... but its a very, very short list.
Mid drives up the ante on the required competence of the builder. Read this so your bike lasts without things breaking or wearing out early.
talesontwowheels.com
If you can ride a bicycle you already know how to ride a hub drive ebike. Not so a mid drive. Particularly a powerful one that can tear your chain apart. Fear not. The rules are simple.
talesontwowheels.com
So M@, what do you think? Any of these bikes seem like they might work for conversion? And thanks in advance for any other advice or recommendations you can offer.
I would say no, but a frame like the Jamis
with disk brake mounts would be ideal. Part of why I recommended picking something like a Surly Grappler was because the rest of the components on the bike were modern and safe. Plus the Grappler already used the Advent X drivetrain out of the gate. A bike like that would let you just pull the bottom braket off, plug in a motor, bolt on a battery and off you go. Otherwise you are going on a frame hunt and doing it the long way. Which can be a wonderfully rewarding project, but not sure you want to go there. My Intense Tracer, now renamed the Apostate, is loaded into my car tomorrow morning on its way to the Lower Sierras where it and I will spend the better part of a week poking around.
Incidentally, here is that bike, now-assembled, back when it had street tires on it. Schwalbe Pickups, which are hard, fast rollers.
Part of the reason I rechristened the bike 'Apostate' was its a dedicated mountain bike re-purposed for pavement. A Surly Grappler or a Marin Pine Mountain are good choices for a street ride when you consider the beefed up components are better suited to a life with electric assist.
, or yellow stripes to make it more Vespa?
(for those of you who don't do Latin, it is the name of a certain family of Yellow Jackets.) Hmmmmmm
, of course with Red I could go with scales, outlined in silver, for Dragon, but again, there was the Honda 250 I was planning to make a dragon as well. . . . . nah, it'll be black. 
