On flat ground, I don't know. Maybe about 45-50kmph (28-31 mph). However, there is a long downhill on my ride home where my max speed has been 75.5kmph (47 mph). That was on a very warm day with no wind. I'm too light to go any faster than that.

I've hit 45 mph a couple of times on a long, steep downhill with a tail wind pedaling like crazy in my top gear.

Apparently it's actually faster to not pedal when you're going that fast. You gain more speed from an aero tuck.

Spin, you madman, SPIN!!!!

Top speed on my regular commute route is 42 mph - coasting in a tuck down the hill that leave from my house.

Top speed on my secondary commute route is 48mph pedaling down the hill behind where I work.

And top speed overall is 50mph - also pedaling down the other side of the hill from my house (yeah, it sucks to have to ride home).

All riding a 2007 Tricross Comp.

Top speed with the tandem on a downhill run is limited by the intensity of screams from my stoker. Usually have to hit the binders at 35mph. I'd like to see just how fast we could roll, but it would most likely end up with a number of nights on the couch for me.

38.83mph on my Sirrus. In the tightest tuck I could get myself in on a flat bar road bike - drafting behind a decked out roadie. Not pedaling at all.

38.61mph by myself, pedaling like mad, partial tuck. Same bike.

I hit somewhere around 120mph last time I jumped out of a plane.

One good thing about being canadian is that in kms the number is bigger.!!!

On a flat road with no wind I can go at about 40 km/h for at least 40-50 seconds.

my absolute record is 75 km/h on a very steep hill, I think I could have gone faster but I carefully put the brake to control my speed because I was scared to go any faster.

When I was 20 years old (in 1995) I bought a old 1979 trans-am with the 602 buick engine (special edition with the t-top and 4 speed automatic transmission) and I got to 190 kms on the highway but that's another story.

I don't know because I've never even tried going for the top speed as yet. I took my bike computer off few years ago, I don't even know what my daily speed is anymore. Keeping track of speed and trying to break speed records is irrelevent to me, I just ride for enjoyment, sometimes fast sometimes slow.

Sort of. You can actually boost your speed a little by pedaling like mad down hill. Pros doing road races coast down the hills because there is so little benefit speedwise from pedaling down hill, they are conserving energy for the uphill portions. The guy who figures out to coast uphill will be famous.

One hill I frequent I can take coasting at 38. Peddling like mad I can almost hit 40. Not really worth it since there is another uphill right after it bottoms out.

51 mph on my recumbent, and there's a nice left hander at the bottom, so lots of good lean angle at the end of that one. That's on one of my alternate routes for my normal commute. Now, going back up from the bottom of that hill is another story....

The slightly less fast route, I've managed over 40 mph for nearly 3 miles if I hit the first stoplight on a green.

On my motorcycle: 164 mph (indicated, probably really only in the high 150s).

I haven't been supersonic in a plane yet, but if I get my pilot's license, I got a friend with a T-38. All I gotta do is buy the gas.... (which is ~$1200/hour).

On my commute, the fastest I went was 27 mph with a tail wind on flat terrain. Fastest ever was 39.8 mph downhill - I wish I'd touched 40, just to say I did!

26 mph on the flats though I'm pretty sure I can pull 30 for a few seconds or two. 39 downhill tucked on my street slicked MTB on a 7% 1/2 mile downhill. Could probably hit 42-43+ on the 'Nago...but 39 is fast enough and when the cars slow down a bit and passengers give you a thumbs up...that's a bit too fast on 18 pounds. I can't imagine going 50+.

The computer kept flipping back & forth from 40-42mph. It was a dead calm on level ground. I was able to maintain for about 5miles.

I find that when tail winds get too gusty they some how stop helping. Its like my tires can't dig in well enough to get max thrust. It doesn't happen very often, but when all the planets are in aligment....the ride can be so sweet.

OK. I think getting all anal about trying to set personal speed records while commuting is silly willy, recording it and posting it, even sillier willyer; but to each their own.

Somewhere in the high 60s (measured in kph) so something like 42-43mph I guess. That was down a good sized hill but without pedalling.

The fastest speed I ever hit on flat road was a whisker under 29mph. No particular reason, the road was smooth, traffic was light, the speed limit was 30mph so no need to worry about fast traffic, and I was curious. I think I surprised the van that was following me.

On a flight from the US back to England the flight crew were OK with me turning my GPS on and I clocked a maximum speed of 693mph.

I've done 31.5 mph on my singlespeed. Ofcourse, that was done downhill. Plus there's a light in the middle of the hill. 25 mph maintained for about 30 sec. My bike's gearing is 63.6 gear inches. So pedeling at that speed, your spinning pretty fast.

58 to 60 coming down Tramway in Palm Springs California on a 84 Trek 660.

I've only gotten to 34 mph. At that speed, I start to think about pot holes and large cracks in the road. I always start to coast and thus slow down.

38 is my top speed, and I reach it almost weekly, on either road bike or cyclocross bike. Can't break it, as hard as I try, though I am heavy. Illinois just doesn't have big hills, and the biggest ones always have stop signs/lights at the bottom. Hit 33 on most commutes.

My fave was this road that used to be near me, which had a sharp curve I would hit at 38 mph, and I would lean around the curve so deep my leg would lightly brush the ground. Terrifying and stupid. Unfortunately, they upgraded the road so its straight.

Flat and sustainable around 36kmh on my slick equipped mtb. Downhill I hit 60mh once. Probably could go faster but my will to go faster fails.

We only have a few big hills in my area. I am a fatty and my wheels are nice. If I pedal like a crazy man at the top and get to 30ish before the decent I can easily break 50mph on the really steep and long decents. It is fun to hit the recall button just because I am a speed demon.

On my commute I hit 30mph most days on the decents. Otherwise, I'm just a fat fred riding the MUP.