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

[Eric7]

Sharing my measurements.  I measured the threadless stem on the Rad Mini ST.  It is a 1 1/8 inch diameter threadless stem.  The top of the frame, where the stem comes out is 31 inches above the ground or about 79 cm off the ground.

I plan to replace the steering stem because it is too high off the ground even at the lowest setting.  I'll probably get a 5 inch or 6 inch extension and put it about 36 or 37 inches off the ground.

[Radio Runner]

Did the same on my RRunner. The stock bar and stem combo were way to upright for me. I lowered hand position by about 8 inches and my back and neck are still upright. I'm 5'10"

[Eric7]

Did the same on my RRunner. The stock bar and stem combo were way to upright for me. I lowered hand position by about 8 inches and my back and neck are still upright. I'm 5'10"

Thank you for your advice.  I measured the folding stem from Rad on the Mini ST and it is about 12 inches long (from the very bottom to the very top).  I ordered a replacement straight non-folding stem of 210 mm which is 8.3 inches (from the very bottom to the very top) so I will be dropping the handlebar about 4 inches.  Also, I don't have to put the handle bar at the very top of the new stem so I guess I can adjust the height of my new stem from 3 inches to 8 inches (dropping the handlebar 4 inches to 9 inches.  I figure this is nice because I can move the handle bar up and down until I am happy.  Time and age makes me not want to bend down so much when pedaling anymore.  After I figure out the optimal height for the Rad Mini ST I'll go work on my road bikes and figure out the optimal height for that.

After this project, I'll think about handlebars.

[Eric7]

The Mini ST has one issue. The steerer tube only sticks out less than 1 inch from the top bearing.  I did not have the setup to measure it exactly but it is certainly less than one inch. It is hard to replace/extend the stem with anything else when there is only 1 inch to work with.

[Radio Runner]

 So the pinch bolt on the steering column is only compressing an inch of steer tube? Would be nice to see a picture of what's going on under there.

[NaturallyRC]

I'm interested too. Where did you get the parts, and which ones, please?

Did the same on my RRunner. The stock bar and stem combo were way to upright for me. I lowered hand position by about 8 inches and my back and neck are still upright. I'm 5'10"

[NaturallyRC]

Kindly keep us posted. I also find the bars strangely high.

Sharing my measurements.  I measured the threadless stem on the Rad Mini ST.  It is a 1 1/8 inch diameter threadless stem.  The top of the frame, where the stem comes out is 31 inches above the ground or about 79 cm off the ground.

I plan to replace the steering stem because it is too high off the ground even at the lowest setting.  I'll probably get a 5 inch or 6 inch extension and put it about 36 or 37 inches off the ground.

[Eric7]

Disclaimer - this is what I measured.  Don't rely on it.  Make the measurement yourself.  I am not a bike mechanic.  I am an amateur chatting.  I am not trained in making measurements and I may be using a wrong standard. I can be wrong.

In answer to your questions, you can easily figure it out yourselves and come to the same conclusion.

I consider the top of the "frame" as the top of the flat washer on top of the top bearing.  Without taking the bike apart at all, you can measure the length of the pinch area. To make it easier for you to visualize it, fold the stem so you don't get confused with the long stem unfolded. The pinch area is exactly one inch long by my micrometer measurement inside the hole of the stem after the stem is removed. But you don't have to remove it, you can make an educated guess from the outside using a ruler and see what I am saying is right.  The folding hinge of the stem starts about 1 inch from the bottom making it impossible that the steering tube sticks out more than 1 inch.

My feeling is it is actually less than one inch but I use a bike stand and I have to manually push the fork into the frame when measuring the length so it is not totally accurate.  The lower limit is 21.62 mm which is what I measured.  Once again, it is my lower limit, it is not a higher limit.

The stem hole (my name for the part) of the clamping part of the stem is 1 inch deep maximum according to my measurement - taken with the stem removed.  But it does not mean that the steerer tube is sticking in one inch.  It has to stick in a little less than full length so you can tighten it with the star nut/hex screw/top cap arrangement You can see and guess from the outside that I am right.  My measurement is that the steerer sticks in 21.62 mm - possibly a bit more but no more than 25.6 since that is all the hole would accept.

On my other non-electric bikes, the steerer tubes are 3 inches long.  Maybe 1 inch of spacers and 2 inches of clamping area for the stem.

Once again, read my disclaimer 

[Radio Runner]

Eric7, Your description is perfect and the pics help. Unfortunately it would seem that the steer tube is cut shorter than the usual 2 or 3 inches so the folding part and clear it. (makes sense for the intended function)

This does leave a stem modification rather tuff without total fork replacement. There is a chance a Delta stem extender may work but hard to tell without installing 1st and then torqueing the bars around to simulate riding stress. I say if it goes 3/4 into the Delta extension its "most likely" good to go.

https://amzn.to/3lgSgJV

[Eric7]

Eric7, Your description is perfect and the pics help. Unfortunately it would seem that the steer tube is cut shorter than the usual 2 or 3 inches so the folding part and clear it. (makes sense for the intended function)

This does leave a stem modification rather tuff without total fork replacement. There is a chance a Delta stem extender may work but hard to tell without installing 1st and then torqueing the bars around to simulate riding stress. I say if it goes 3/4 into the Delta extension its "most likely" good to go.

https://amzn.to/3lgSgJV

I think we may be stuck with the folding stem.  The stem you recommend has a minimum insertion of 40 mm which would mean the insertion would be closer to 54% insertion.  My guesses are

(1) that when Rad first designed it, it was a smaller company with limited capacity to spec its own parts so it used what was available. There are a few bikes that look amazingly like a Rad Mini ST on the web.  This was a design weakness they could not address.  With the Expand, they got a shorter folding stem and a handlebar with a high riser (i.e., looks similar to a BMX bar). Looks like the Expand may also have a fork steering tube that does not stick out so much.  At least with the Expand, if you get a handlebar with a lower riser distance (i.e., a regular handlebar), you can drop the handlebar height. 

(2) Rad never saw it as a problem because they don't expect people to change stems.

Would have been nice if the steerer tube was a bit longer.  Most of the other parts on a Rad is generic which I consider a really good feature.  It means you can maintain the bike even if the bike is discontinued and the availability of parts from Rad is gone.  There is another thread where a Rad is totaled and it is being rebuilt.  https://www.radowners.com/index.php?topic=2036.0    I wonder whether Rad sells the new shorter folding stem.

[Onebuckz]

I tried inquiring about purchasing the stem and handlebar of the new Rad Expand to retain the foldability but either they are not selling it separately or are not willing to sell it at all.
Perhaps something similar will be available in the future from online chinese stores like Aliexpress since these parts come from there mostly anyway.

[Eric7]

I tried inquiring about purchasing the stem and handlebar of the new Rad Expand to retain the foldability but either they are not selling it separately or are not willing to sell it at all.
Perhaps something similar will be available in the future from online chinese stores like Aliexpress since these parts come from there mostly anyway.

Thank you for the info.

I measured again, the steering tube sticks out more than 21 mm and less than 22 mm.  That's it.  I have the following current thoughts.

1.  There are gadgets on Amazon that allows you to add 30 mm or so to your steerer tube.

2.  BMX stems seem to only require 1 inch stack height.  But they are only for BMX 1 inch thickness handlebars.

I am still thinking about it but I have also not completely thought it through.  In answer to the question posed to the "Rad Runner" owner, I think, by looking at the pictures, the Rad Runner has more steerer tube to work with.  Also, by looking at the pictures, I think the Expand and the Mini ST have about the same steerer tube length.

[rjp]

This one is longer, https://amzn.to/39tVnMf

[Eric7]

I define the Rad folding stem as 12 inches.

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/3lgg1Sw

It feels so comfortable.  Just went on a test ride.

I got a steering tube extender because the steering tube is only 21.5 mm sticking out. 

https://amzn.to/3sBUW9a

This has not come yet.  I have no review for this.

I think in the beginning I thought, well my arms are still hanging down.  I'll be OK with the stock stem.  I am riding a Dutch bicycle now. etc. etc. excuses excuses.  After trying the 8 inch stem, I wonder how I ever lived without it.  Also, I can mount the handlebar lower to try for example 6 inches and 4 inches.  I am very happy with 8 inches for now.  I'll give it a week before further lowering it.  Give each position a few weeks for experiment.  I fell a few times because it is harder to hold a tall bike in a fall - at least for me.  Now it feels more stable and secure and I can lean forward in a climb etc.  The original configuration of 45 inches off the ground is a bit too much for me.  Great for going downhill but not so much for climbs. 

● In a climb, once you are stuck and speed goes to zero, you are in trouble.  I always fall because the tall handlebar prevents me from standing up.  Some climbs are quite steep - I mean for only 5 or 10 feet - getting over a hump really.  But if you can't do it, the high handlebar guarantees a fall - at least for me.●

These extensions allows you to set the bearing tension once and clamp the extension down.
Then you can slide your handlebar/stem up and down without having to adjust the bearing tension again.

I still have the stem reversed.  It points towards me when I am seated on the bike.  You can think of me as having a -60 mm stem.

Please note I don't recommend anything at this point.  I am still in the trying stage and I'll report later.  I am not approving or endorsing any product.  There are many variations you can buy from Amazon.  Also I don't want to be responsible for your safety so you have to decide on your own.  Take your own risk.

[rjp]

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.