We have managed 45mph on the flat but only held that speed for about 10 seconds. Mind you at a Cadence of 150- I did not want to--

The "We" bit--It was on a Tandem and we were just at the end of training for a very hard ride.

I would suggest that he is in error somewhere.
I know that it is possible to spin a bicycle wheel at ridiculous speeds on no-drag rollers (IF the gearing is present to do it) but as for actually moving through dead air? Not likely.

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If you really want to sprint to 50+ MPH it can be done, but not on a regular bicycle.
https://www.recumbents.com/faired.htm

People who own fully-faired hard-shell 2-wheel HPV's say that an "average" rider can cruise at about 35 mph and usually get them up over 50 mph for brief periods.
They are cramped, have poor rider visibility and don't like crosswinds however. Also bring $$$$. Kevlar is highly recommended for the shell, since it will protect you from "cheese grating" in a sliding fallover at speed....
~

The sprinters in the pros come out of their team drafts and hit 42 to 44 mph on the radar gun for a few hundred meters.
I doubt that anyone else is capable of those speeds.

Just how much gear do you need to even be theoretically reach those speeds?

I once hit 45mph on a flat briefly due to a hellacious tailwind.
I had just aborted my intended ride, and done a u-turn due to that wind
At 45mph, I was spinning ~145rpm, hence the "briefly".

Where in Michigan is this brother-in-law?

The UCI upright bike hour record is in KM/h, but the HPV record with a fully faired 'bent is ~56 MPH or ~90 KM/h. But we ae not tallkng about a guy that got his first bike last year.

Edit:

From https://en.wikipedia.org/wiki/Bicycle_performance

"The highest speed officially recorded for a bicycle ridden in a conventional upright position under fully faired conditions was 82.52 km/h (51.29 mph) over 200m"

50mph seems wayyyyy too fast. I can get to 30mph if I try as hard as I can. The fastest I have gone downhill is 51mph which I will never do again.

The pros typically will have a 53 x 11 or something like that as the lowest gear. But most of the sprinters will probably be in something like a 53 x 13 during the final sprint. In the lowest gear they probably cannot accelerate fast enough. The speed is around 42-44 MPH for the fastest road sprinters at the end of a stage on a flat road surface with no wind. As has been stated above. They can go faster in a strong tail wind. Tandems can go faster but most probably cannot hit 45 MPH without a tail wind. They would have to be close to world class athletes to have done that. But a couple of strong cyclist's on a tandem with a strong tail wind can get moving really fast.

You are correct for the upright fared record. The fully fared recumbent division human powered record is held by Sam Wittingham and is around 82 MPH. Yes you heard that right. This is without drafting but is in a missile shaped fully enclosed bike. The fastest time on an indoor track for 200m on an indoor time trial bike is around 51 MPH. Who knows for road racing. Conditions are not controllable enough. Recumbents can go faster and are in a different division.

The one hour record in a fully fared bike is about 56 MPH:

https://www.ihpva.org/home/

https://www.ihpva.org/hpvarec3.htm#nom09

The UCI records for more conventional bikes are on this page. And the other page sited.

https://en.wikipedia.org/wiki/Hour_record

Of course we have all assumed our man was turning the pedals on a bike unassisted...

I experienced a case this past summer where my GPS unit (Garmin GPSmap 60CSx) registered 48mph for a segment. I know that I was nowhere near 48mph on that segment (or any segment for that matter). I was in downtown Pittsburgh at the time and think that the buildings caused the unit to become temporarily confused (switching satellites combinted with ± 20' error). I agree with the poster that said that a "more" traditional cyclocomputer (properly calibrated) would give a more accurate measure of speed.

I have hit 38 mph on flat ground with 53*13 and was starting to want to upshift. Bicycles without some sort of customized grearing just to not have high enough gears to go at 50 mph.

Also figure the a great time trial by a world class time trial specialist is around 34 mph. That is just to give you an idea.

I have heard of people hitting over 50 on a bike but that has always been on descents. I have never heard anyone even claim to hit 50 mph on the flats.

I suspect that there was a glitch on the equipment and your brother and law bought it at face value.

Of course, his speed is nothing. I once "averaged" 115 mph on a club ride which was going at a "C" pace. Now who wouldn't believe that? I rather suspected that there was something fishy going on with my bike computer.

Assuming a 700cx25 drive tire with an actual diameter of 26.4", a 53/11 gear spun to 132 rpm would get you to 49.9 mph. I can spin that fast, but at that point I'm way off my power curve and I'm just spinning. Actually applying 2-3 hp at that cadence - no way!

My 60CSx clocked my cycling speed at 248mph at one point. In fairness I had just emerged from a long tunnel. Otherwise I'd have to say I can only imagine how humiliated the likes of Contador and Schleck will be next year when they are roundly thrashed in the Tour de France by a fat guy on a mountain bike...

I'd say that was about it.

I should be able to hit 50mph - downhill - but I haven't, yet.

Goal for 2011: 50mph - downhill.

So what is a big downhill in Indy?

That's the problem with Indy and thereabouts - too danged flat.

Lots of up-and downhills in Morgan, Brown, Monroe, Greene, Owen and many other counties.

Yup, and I have a Garmin Connect log that shows a top speed of 2,507mph. I don't even remember breaking a sweat! P

Must have been a re-entry speed.

Temporary amnesia is a common symptom of exceeding the sound barrier on a bike.

I can't believe your BIL doesn't think it's beyond
an olympic feat, and maybe google bike speed records.

I managed to get my car up to 970mph. Not bad given I was apparently about 200 miles west of Ireland in the ocean. Even so, I bow to your superior speed. If only you could sustain it, you could complete the entire Tour de France within an hour. Just look at the lightweights who need a couple of weeks or more to do it.

My motorcycle has a VMax recall. One time the speedo sensor went south. I had a VMax of 275 MPH.