Overheard a shop veteran say carbon paste is a scam on aluminum stems

I was at a group ride last Saturday and this old mechanic said you don't need carbon paste on aluminum stems because it just clogs the bolts and hides loose fits, but doesn't the friction actually stop slipping - anyone else run bare metal and had a stem shift on them?

2 comments

2 Comments

barnes.jamie2d ago

I mean I hear what you're saying but honestly I've run bare aluminum stems on a few bikes for years and never had a single slip even on a hard gravel setup. The whole thing with carbon paste is it's mostly about filling tiny gaps in carbon layup, aluminum is already solid so the clamping force from a properly torqued bolt is way more than enough. Maybe it's just me but I'd rather have clean threads that don't get gummed up with that gritty stuff every time I adjust my stem height.

leor372d ago

Yeah but you're basically playing Russian roulette with a sharp edge. I've seen WAY too many aluminum stems eat into carbon steerers when the grit gets between them even with proper torque. That paste isn't just for grip, it creates a barrier so the metals don't gall together under load. Had a buddy snap his fork crown right at the stem clamp because the two surfaces fused from fretting corrosion over a wet season. Clean threads are nice and all but I'd rather scrub some grit off once a year than replace a fork.