As a fellow Canadian (or really any non-American) you shouldn't be assuming mph.

Unless you're landing men on the moon

OK, my usual solo pace is 16.25-17.5 mph and those guys were going about 18.75-20 mph. Later they upped it to 25-26.25 mph and dropped me.

There's nothing unbelievable about that. I'm not sure why @mcours2006 questioned it.

19-20mph is no big deal on flat land, and it wouldn't be hard to draft at that speed(even on a mountain bike).

That mcours2006 guy maybe not up to snuff with the beasts found on this forum. Needs to HTFU and do more training.

There is always someone....

Around here (SoCal S OC and N San Diego) it is better to tell them to knock it off. Or stop and let them go. There are too many variables and knuckleheads of vastly different abilities. Beginners on pro bikes, to the electric bikes, to some surf camp kid on a MTB thinking he can mix in with the "real riders". There are plenty of group rides that welcome you and plenty of solo riders you can get to know, then ride with. But jumping in with strangers, esp those without their hands on the bars is increasing risk considerably - esp in higher speeds.

This was a cool down after a rowing competition on a course you know well because we had the TT bike in the trunk - so used it. I told him I'd drive behind and honk at anyone that got on his wheel.
We've often had issues with the un-invited while training. Actually more by "real cyclists" thinking he was following them as a kid. He still gets barked at by old guys.

^ Passing car on the left???

I hate to throw around a stereotype but my experience with triathletes is most of them are blind. They'll run over a California Redwood and feed it to whoever is drafting them. Add to that the choppy, start/stop pedaling (especially on slopes), abrupt speed changes and you've got yourself a great chance to find out what your medical co-pay is. I don't care who drafts me because nine times out of ten, I'm not the one who's going down. However, I'm very choosy about taking a wheel from someone I don't know.

Hey now, i am a roadie who's gone over to the dork side. Re triathletes - the serious ones are not that different from roadies. Many of them do go out on group rides on their road bikes, etc. The casual ones? Well, they are no different from the freds that dont know group riding etiquette either. I dare say only a small percentage of people on road bikes can be trusted in a paceline.

Yeah, the trust thing is a big deal when drafting or riding close side by side. And after a crash or three I'd bet most of us tighten up our trust standards.

Of the road group I ride with occasionally there's only one guy I trust enough that I'll draft him even at night on a narrow twisting path, having no idea what's ahead but his butt. He's that good.

I try to return the favor but I don't have his bike handling skills on fast curves and twisties. I always lose a split second, a gap opens and I'm dropped. But I'm okay on straights and rollers so I'll pull for a mile on those segments. Good workout too.

A few other folks are regular leaders on casual group rides too so they're pretty predictable, although I don't trust them quite enough to just lock my gaze on the wheel and follow. I'll peek around as we'd normally do.

The other guys... some are pretty fast but they'll run you right into traffic cones, potholes or debris without warning. Some wobble around or shift lines randomly without seeimng to be responding to actual road hazards.

On the plus side, riding with folks I don't really trust made me stronger because I'd drop out of the draft and work harder to keep up. Sorta Cat 6-ish. Not quite the experience I was expecting from a moderately fast club ride, but, hey ... lemonade from lemons and all that.

Best drafting experience I had last year was when one of the regulars had to concede to age and started riding an e-assist road bike. He's very smooth so I'd get in his wheel on climbs and rollers. Lotta fun. Closest thing I've gotten to pacing off a Derny.

A lot of tri guys train where I ride. Many of them have a particular way of riding: slow cadence, aero position, trying to sustain 40-43kph, "serious" impassive face, staring way ahead, impervious to everything... Maybe that's why the stereotyping.

People train in a manner appropriate to their competition. Shocking.

The only image I have of tri-folk is blasting down the 4 foot wide sidewalk that laughably passes for an MUP, 25 mph, in the aero bars, nowhere near brakes, blitzing past dogs on retractable non-leashes, joggers and walkers zoned out in earbuds, and older folks using wheelchairs, walkers and canes.

I don't get it because our area is fortunate to have some safe public roads for those of us who enjoy riding fast.