Seat tube / bottom tube joint wobbly

This problem is hard to describe, so I apologize in advance if my description is hard to follow. In fact, I’m not sure if it even is a problem.

For some reason I recently noticed that there is a certain amount of “play” between the bottom tube and seat tube at the point where they meet. If I stand next to my (unfolded) Strida and grasp the seat – or any other part of the seat tube – and wiggle it laterally (imagine trying to turn the seat in a circle, alternating clockwise and counter-clockwise), I can see and feel how the seat tube slightly moves toward/away from the bottom tube at the joint, rather than remaining flush against it.

The bottom tube is not too loose, but it isn’t that tight, either. In other words, it moves quite quickly when I fold or unfold the Strida. I have tried the obvious: tightening the bolt that holds bottom tube and seat tube together as much as possible. But I can’t seem to make the bottom tube any tighter than it already is.

So: is this “wobbly” joint normal? And if not, why is tightening the bolt not minimzing or eliminating this problem?

It sounds to me like the 2" dia nylon washer between the tube that connects to the Pedals and the one that connects to the seat is worn. I had this, on an old STrida2 and cut a new one from a spare plastic carton (about 1/6" thick). The screw bottoms out so only the thickness of this washer and the outer cone washers takes up any play. I guess alternatively you could add another cone washer (if you can get one - I couldn’t).

The strida triangle will never be as solid as a non-folding bike. The previous post listed one “fix”. The other thing I noticed is that sometimes my front tube pin (the one that the bottom tube sits on, part #216 on the strida diagrams) sometimes works its way to be a little loose. Retighten those bolts and the connection is a lot more solid.

Thanks for the suggestions. To what part exactly does “cone washer” refer? Is it the part with the hexagonal recess into which the screw fits snugly when it is tightened?

The cone washers are like little springs (I think they are also called Belleville washers … or is that a cycling film :smiley: ) - they fit under the Big hex bolt at the rear joint … they sort of Clamp the bottom tube against the ‘seat tube’ so it is as stiff as possible when pedaling and also allows folding.

Agreed about the steering pin screws, I’ve seen much written about them on here … bottom line is check and keep them as tight as possible.

In the diagram in the manual, I see three washers under the hex screw. Are these the “springs” to which you’re referring?

BTW, as I mentioned previously, my hex screw has a matching washer with a hex-shaped recess into which the screw snugly fits. Looks different than in the manual. So I’m not sure if I have the three pictured washers. Will have to disassemble and take another look …

Yes the bigger ones of the 3 are spring washers, see strida1 manual for more info on these…
These must be one of the few areas which is much the same on Strida5 as it was on Strida1, this manual explains it quite well…

You might need another washer compress the spring washers, so they are loaded. A new, thicker nylon washer between bottom tube and seat tube also will have the effect of compressing the spring washers.

Thanks for the tip.

On the outside I only had 2 washers (1 spring, 1 normal). Added a 2nd red washer on the inside and my wobbly back wheel vanished.

Not sure whether you need to be carefully with keeping the belt on the same teeth when taking the arm on and off ?

I had to re-tighten the nut, but its been ok since - and I find I’m less prone to drop the bottom tube while unfolding now the movement is stiffer. I noticed when folded the bottom tube has to deviate more from a simple up and down fold to move out and over the rear tube and the tube protector.

On my old strida 2.5 the tube didn’t seem to have to move so much to the right to get over the ‘nobble’ on the plastic bottom bracket housing (and sometime I didn’t even bother doing that)