bike stem solution
 

I made a drawing but can't post it yet. On my engwe 750 engine pro I have 21mm available steering tube length to mount my 30mm thick stem. The upper stem mounting bolt centerline is in line with the top of the steering tube.

I'm thinking about putting a steering tube diameter spacer below the top cap to support the upper stem bolt compression with a slight gap below the top cap rim. Not sure I need this though. I don't do jumps or hills, just ride around a local sporting clay course on a gravel path. Think this will work?

Wish I could post the drawing, might make things clearer.

I havn't measured the rim dia of the top cap, not sure the stem will compress on it. It seemed like a sloppy fit.

Not exactly sure of the situation but having the stem/steerer clamp's top bolt even with the top of the steerer is what I consider a must. If the steerer doesn't extend above the stem there's generally no need for a spacer above the stem. Andy

I need to post the drawing I made, it would make it more clear. I have to make 10 posts before I can post an image.
I guess I could reply 9 more times to this lol.

I guess that why people bump their replys? lol

well that didn't work. tried to link to the gallery.
I put the drawing pic in the gallery if you can find it lol

I can't find it. Go to your user profile and create a picture album and post the pic there. It will be easy for others to find.

Ok, made the album with the pic. Thanks for the idea :)

Pic assist. I get squeamish when it comes to steering/handlebar mods. I would advise against this. Can you get a stem with shorter height?
https://cimg2.ibsrv.net/gimg/bikefor...157982c531.jpg
https://cimg7.ibsrv.net/gimg/bikefor...c5b4b3bc1f.jpg

I don't like it a bit. The idea of having two clamp bolts is to increase the area under clamping pressure (and add redundnacy). What you propose seems to me like you are "stealing" clamping pressure from the stem and using it to uselessly clamp the spacer. If oversize, the spacer could conceivably compromise the clamping ability of the lower bolt, too.

Given the height of your handlebar, you should seek another solution. Your proposed "solution" is dangerous, you need a fork with a steerer long enough to provide support through the whole depth of the stem. If you have a failure in that area results can be fatal. Last summer, a local cyclist died when his stem broke as he rode over a speed bump. His bike setup was far less extreme than yours

You need to find a lower stack headset to pick up 6mm or so of steerer height. I can’t think of any other option aside from replacing the fork with a longer steerer.

John

I've considered all those things. I talked to a guy at a local bike shop, he suggested I find an old steerer tube and cut a piece off to make the spacer. Even looked at mil spec washers but the correct OD would be hard to find.

If you look at my albums you'll see a pic of a "bike hidden stem extender" I think might work. Most reviews were good, a few thought it might come loose with a hard turn to the left.

I think the best way to mount it would be to split the difference between the steerer tube and the extender with the new stem with headset spacers below the bottom of the new stem and snug the stem bolts. This would ensure alignment for both.
Then tighten the extender bolt using the stem to hold onto to get it tight against the inner wall of the steerer tube. Maybe add some removable loctite?
Then loosen the stem bolts, add headset spacers to the top, and set the headset preload.
Then finally torque the stem bolts.
Ya, that will work, i'm sure of it (final last words lol)

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The first vid is interesting, kinda the same principle as the steerer tube extender. I saw those but wondred how you would preload the head set with one of those. Kind of a okie rigged set up but I guess it would work. I'd hate to take that apart though if I had to.

The second vid... must be nice to have a shop like that lol.

Here's a shout out to cat0020. I noticed in the electric folding ebike thread you too have the engwe 750 pro with lowered handlebars. Was your steering tube short like mine and how did you solve attaching the extention for mounting the stem?

I tried to send him a message but I havn't reached the 10 post 5 per day thing yet. If someone could hit him up maybe he could view this thread and respond.

I'd appreciate it :)

Why don’t you flip the stem?

I really like the idea of using the tube extender. If you had a steel steerer and a steel extender, you could actually weld it and then grind it. Lower weight.

As for having a free-floating spacer under the stem where one of the tightening bolts is, it probably is a bit better than tightening a clamp on air (the machinist in me has a big negative reaction to tightening anything onto air). But it's suboptimal and I think dangerous.

Bettter to use the extender idea - this has the stem clamps tightening on an integrated tube.

It wouldn't make any difference, the bolts are symetrical. Even though my drawing doesn't really look like it.

It's the shortest stem height I could find (30mm) that mounts the way the drawing shows.

I wish someone would link to my photo of the "bike hidden stem extender" in my albums. I'd like to get an opinion on it.

I have 1 posts to go before 10 after this one so I need to use them up today so I can post like a normal person tomorow lol.

Ok, last post today lol...
Ya the spacer idea was just so the upper bolt would have something to clamp to. The bottom bolt would be doin all the work. I think I'm gonna go with the "bike hidden stem extender".
Had to order it from china, down side is it takes a few weeks to get it.

You could probably find the 1-1/8” quill to threadless adapter without having to go to China. They are pretty common.

If the threadless steerer ID is the same as a threaded ID, then there would be no difference using it.

The flange nut looks like an interesting work around. I might be inclined to find something with a little bit better interface. A stainless spacer chamfered to fit against the angled reducer section.

John

Edit added: Using a compression plug instead of star nut is a smart idea since you loose access to the quill extender. It would be more of a pain to remove the star nut since you can’t tap it out the bottom of the steerer if you ever needed access.

The assembly illustrated in the diagram above is dangerous and exacerbated by the BMX style handlebar and the fact that this is an e-bike. Much safer to just get a fork with a longer steerer tube.

Here's the hidden stem extender I'm gonna use. Found one on amazon, gettin it tomorow. Ya baby lol.
https://cimg6.ibsrv.net/gimg/bikefor...4425ffb407.jpg

c-bore a pocket down to the existing steer tube height?

No it fits right in the tube.
https://cimg1.ibsrv.net/gimg/bikefor...ad614790a3.jpg

https://cimg2.ibsrv.net/gimg/bikefor...0f4d19a1b8.jpg

https://cimg7.ibsrv.net/gimg/bikefor...8d291a8ac8.jpg

Then I'm gonna put on this like I originally wanted to do :)
https://cimg1.ibsrv.net/gimg/bikefor...f52526b656.jpg
This shows it used on a carbon fiber tube.
https://cimg3.ibsrv.net/gimg/bikefor...0e147bf6c4.jpg

There are a few ways to extend the steertube for mounting different stems on the particular ENGWE ebike, I've tried a several, still trying to finalize the most secure way for myself.

I think the method Gearbasher used is fine, as long as the top cap keeps a decent amount of tension on the whole setup.
https://cimg7.ibsrv.net/gimg/bikefor...c5b4b3bc1f.jpg

I've also tried the hidden same hidden stem extender, it is made of aluminum, the center bolt is aluminum, too.. easily stripped when you try to torque it down. Also it is more difficult to have proper tension for it to secure the headset without a top cap that's threaded.

I currently have this steertube extender installed, easily combined with different MTB stems, not the lightest setup, but with a top cap and long bolt to use existing star nut in the steertube: : https://www.ebay.com/itm/154650501497
https://i.imgur.com/RVMT1Lb.jpg
https://i.imgur.com/Bxukm7o.jpg

If I ever find an aluminum BMX high rise handlebar, I'll probably go with something similar to gearbasher's setup; I don't think it's anymore dangerous than other setups for my riding; that's just me.