Originally Posted by
Pop N Wood
Interesting. Very true that they all turn solid at the top. I will say the ones I've used are split past the top of max insertion point of the tube. There is a mechanical lip that prevents over insertion. Is that enough to equalize the pressure? Hard to say, especially with the low torque points.
At some level, anything except for a full split cylinder should, at least in theory, prevent even clamping pressure. Is it enough to cause harm in practice? I certainly cannot answer that.
I have, use, and enjoy a stem riser on one of my mountain bikes. It's a cheap no-name from Amazon and it's worked fine. It's on an aluminum steer tube, though, and I don't think there are generally any concerns with such a setup. I use it as a "soft roader" bike only, and don't subject the bar or stem or riser to any loads higher than what I'd consider "moderate" trail type riding.