I'm working on replacing the handlebar stem for Mini ST

[Eric7]

Eric7, I'm wondering how the fork bearings will be tightened up if and when you might install the steering tube extension. It's to bad that the steer tube isn't longer.

I'll let you know.  I can't tell from looking at the pictures so I ordered blind.  ● <added by edit> I am hoping that the bolt has a hole in the middle.  Maybe one screws it down with a 6 mm hex but there is a round threaded hole inside the hex hole. The hole remains so you can screw in the pre-tension screw.  But I really don't know and it is coming from Asia and will take forever.  I'll report it but it may be some time. ●

In looking at the Expand, videos of the Brompton, videos of Dahon, these types of short steerer tube seems typical.  I don't like it - but now I guess Rad is just doing what everybody else is doing.

[Radio Runner]

Eric7, I'm wondering how the fork bearings will be tightened up if and when you might install the steering tube extension. It's to bad that the steer tube isn't longer.

I'll let you know.  I can't tell from looking at the pictures so I ordered blind. 

In looking at the Expand, videos of the Brompton, videos of Dahon, these types of short steerer tube seems typical.  I don't like it - but now I guess Rad is just doing what everybody else is doing.

Brompton has a quill insert like older bike stems so there is no steer tube that needs to be compressed or clamped. The headset is tightened old school useing a threaded steer tube.

[Eric7]

Brompton has a quill insert like older bike stems so there is no steer tube that needs to be compressed or clamped. The headset is tightened old school using a threaded steer tube.

Thanks.  I learned something.

I will modify what I say. 

It appears having a hinge close to the top of the frame in the steering stem is a standard design for folding bikes from Rad, Dahon, Lectric and Brompton.  The Brompton uses a quill so it does not suffer from a short steer tube and threadless design (thanks Radio Runner for pointing it out).  I don't know about the others.

[rjp]

Yes but rad dosen't have a  threaded steertube and the Quill type won't tighten the steer tube bearings.

[Eric7]

Eric7, I'm wondering how the fork bearings will be tightened up if and when you might install the steering tube extension. It's to bad that the steer tube isn't longer.

UPDATE ON MY PROJECT.

The steerer tube extender arrived today and it is designed well.  You use a hex tool to tighten the hex nut.  The hex nut has a screw hole beneath the hex hole to accept the steering tube screw to tighten up (or preload) the fork bearings. 

One problem is there is a star nut blocking where the aluminum wedge part of the stem extender would go.  I think I have to drill out or pound out the star nut.  I think I'll drill it out because some people say you cannot pound out the star nut if your steering tube is butted (meaning the hole gets smaller as you do downwards towards the wheel). 

Just to test the extender, I need to destroy and remove the star nut.  If it does not work, I have to buy and install a new star nut.

This is probably a whole day's work.  I enjoy experiments but right now I don't have time because I am tied up with other equally interesting projects.  I'll probably start by buying an extra star nut - or one of the new higher tech star nut replacement which is just a wedge.

I'll probably give it a try this summer but not right now. As always, I wish I have more time to do things.

[Radio Runner]

Just tap the star nut down about another inch or more if needed so its out of the way. Then just leave it in there. It wont hurt anything staying along for the ride.

[rjp]

Eric7, To clarify what your explaining about the steer tube extender. You use a hex wrench (allen wrench) to tighten the hex bolt (socket cap screw). The hex bolt has a threaded hole beneath the hex shaped hole in the head of the bolt, to insert a bolt to preload the stem bearings. Is that correct.   

[Eric7]

Eric7, To clarify what your explaining about the steer tube extender. You use a hex wrench (allen wrench) to tighten the hex bolt (socket cap screw). The hex bolt has a threaded hole beneath the hex shaped hole in the head of the bolt, to insert a bolt to preload the stem bearings. Is that correct.   

Yes.  Your description is correct and more elegant than mine.  The same hole will fit a hex wrench and a screw (which goes in deeper than the hex hole).  I enclose pictures - you have to look carefully but you can see the screw hole which is smaller than the hex hole, of course.

By the way, the link I use is not the cheapest place to buy this extension. There are many places that sell this.  One place charges $50 and makes it look like a custom job.  There is probably only one manufacturer.  Others sell it for $12.  I got mine maybe at $22 from Amazon because I did not want to register at yet another store.  But even Amazon had a few vendors.  I chose a vendor that seemed reliable.  I am not endorsing this - have not tried it yet.

But as I said earlier, I don't see how any extension can remain resistant to rotation.  So I am still thinking about it.

To put it more plainly, if you give me permission, I can probably straddle the front wheel and turn the handlebar (with no stem extensions) of your bike or any bike until it is out of alignment. So that joint is not totally rigid even under optimal conditions. On the other hand, I guess it means the joint does not have to be perfectly rigid against rotation since every bike's joint is like that.

[rjp]

Eric7, How is your handlebar stem replacement going. I'm eager to find out how it works because I need to improve mine also.   

[Eric7]

I did not use the steering tube extender and I bolted the stem extender onto the steering tube.  As I said earlier, the steering tube only sticks out 21 mm and the stem extender only grabbed 21 mm.  I torqued the bolt really tight and the the whole setup seems to work well.

I hit an unexpected hidden mini ditch about 1 foot ride 6 inches deep riding on the grass and I fell so hard my iPhone called 911 automatically.  I canceled the call.  At one point I almost went over the handlebar. Afterward, upon inspection, the handlebar stayed in place and did not move left or right.  There was nothing to straighten out except for the phone holder and the brake levers seem to have rotated a bit.  To restate, the stem extender worked well and did not have to be readjusted.

Based on this data, I think my setup is working well and I don't need the steering tube extender.  I don't take any responsibility if you hurt yourself. You have to decide yourself and take your own risks.  I reduced my stem height from 12 inches to 8 inches (I have an 8 inch stem extender).

For me, I don't think I'll ever switch back. I really like it. I can lean forward in a climb much better now I don't have a 45 inch handlebar blocking my chest.   

Next part of the project 1:  I previously rotated the stem 180 degrees to reduce my reach.  Now, I am thinking of rotating the stem back to normal configuration because my reach is so much better.  This is also because there is not much space between the handle bar and the seat.

Next part of the project 2:  I might further reduce the handlebar height 2 inches.  Originally it was 12 inches.  Now it is 8 inches.  I plan to try 6 inches.  The stem extender I bought allows me to adjust the stem height. By using 6 inches of an 8 inch stem extender, I would have 2 inches sticking out of my handlebar.  I think it will be OK.  I've used a bicycle for decades and I don't remember any situation where an extra 2 inches sticking out of the handlebar would hurt me.

[rjp]

Eric7, what name brand riser did you end up using? I have a 6.5" Delta on my Rover ST and I like that I don't have to use spacers when making adjustments on the Delta. But that might not be long enough on my Mini ST2. I had about 2" sticking out on my Rover until I spun the stem back around to the front, Then I raised the stem to the top of the Delta riser.

[Eric7]

Eric7, what name brand riser did you end up using? I have a 6.5" Delta on my Rover ST and I like that I don't have to use spacers when making adjustments on the Delta. But that might not be long enough on my Mini ST2. I had about 2" sticking out on my Rover until I spun the stem back around to the front, Then I raised the stem to the top of the Delta riser.

I used this one.  It is cheap. Quote from previous post:

         So I got a 210 mm cheap stem extender from Amazon for about $20.  That's about 8 inches.  So I achieved a 4 inch drop.

        https://amzn.to/3N3lyqY

Once you clamp it, you can remove the pre-tension screw on top and clamp your handlebar where you want.  I, however, rearrange the spacers and tighten up the pretension screw afterwards and figure it is a second safety mechanism.  Should the extender clamp fail, my handlebar would be somewhat held on by the pretension screw.  You can do all this without removing the clamp of the stem extender.

You can buy a shorter one.  It depends on your needs.  I was not sure so I got the longest one.

Naturally, the more expensive stem extenders make it easier - because you don't have to rearrange spacers and pretension screws while adjusting height (I am assuming - never actually used an expensive one).  But it is also twice as expensive and when I started out I wasn't sure it would work.

I like it.  I think 45 inches off the ground is too high for a handlebar - especially off road.

You assume your own risk and use your own judgment doing this. 

I am still testing and I am not sure how this will work long-term although I am impressed with the crash performance when I crashed. It seems to be good enough around the neighborhood and riding on the trails and off road on groomed grass near where I live.  The land is full of rabbit holes and hidden ditches. I need to ride slower but the stem seems to hold up rabbit holes and all and my previous higher speed. 

I would not know what to do, for example, if I sign up for an expensive bike vacation.  What if the stem fails at the start of vacation?  I'll worry about it when or if that happens - no plans for a bike vacation.

[Darrine90]

I just purchased a rad mini and am planning to put bmx bars on it!  Do you know if something like this would work to extend the fork to mount the stem? This one is pretty cool because it allows you to fold the bars sideways.

Thank you!

https://amzn.to/3Os6bcX

[Eric7]

I just purchased a rad mini and am planning to put bmx bars on it!  Do you know if something like this would work to extend the fork to mount the stem? This one is pretty cool because it allows you to fold the bars sideways.

Thank you!

https://amzn.to/3Os6bcX

I don't know because I don't have one but I can give you some insights of what to think about.  Once again, you take your own risk.  I definitely do not suggest anyone follow my advice.  You have to decide the safety issue yourself.

Issue 1:

The one thing I would be worried about is that only one bolt holds this stem extender onto the steerer tube.  I wonder about the maximum insertion of the steerer tube.  Say it is 40 mm or 50 mm.  That would mean that the one bolt is acting around 20 mm or 25 mm.  By my measurement, the actual steerer tube inserts only 21 mm.  In this design, with one bolt, you are barely clamping on the steerer tube. 

In those designs with 2 bolts, at least the bottom bolt would be somewhere well within the 21 mm.  My stem extender has 2 bolts of which only one (I guess) is actually clamping and working.

Issue 2:

I measured the Rad factory-issued stem and I feel it has a 12 inch minimum height.  Your suggested replacement has a 3 inch maximum height.  Therefore, you are dropping the stem height by 9 inches below the previous minimum.  Will this be too low for you?  Only you can answer this question.  Maybe you want to compare your ebike with your regular bike or your friend's regular bike to see if a 9 inch drop is too drastic.  Do your own measurements and come to your own conclusions.  Also consider any interference with front baskets or any other accessories.

There may be other issues.  Maybe I have not spotted it all.  I wonder how you pretension your proposed device.  I guess they must have figured that out.


I hope it all works out well for you.

[Darrine90]

Thanks for the tips! Disclaimer I don't have the bike yet but I should next week. I am trying to plan this out because I want to do it right away. My thinking is that with one bolt the clamping force may be more even but its hard to say... Also the BMX handle bar have a 9" rise so I think it will be plenty high enough but will have to measure when my bike arrives.

Also did you watch the video where it was done on the letric xp. They use a quil stem adapter I am not sure if it would work or not? Links below

https://amzn.to/3HxVe7m

https://www.youtube.com/watch?v=dmsj8ykIxBM