Duragrouch Yes the folding stem is tapered but very gradually. Here are my measurements with a digital caliper. 28.53 just below the clamp and 28.58 about 4cm down.





It s a hair less than 28.6 but also most stems will have a clamp gap when tightened. Here are shots of my trail bike stems with the gaps indicated. So you can further tighten the bolts down to compensate. Or you can always use aluminum tape to increase the diameter.







I would do it if I have a spare folding stem to test and as long as your not pulling up wheelies or doing stunts on your bike, I think it's a fairly safe mod to do.