So I got my cyclocomputer setup today and took it out for a trip. I was headed down hill and my comp showed I was doing 39mph and I am not sure if thats right. It was a fairly steep hill and I was moving very fast so I was some what confused if it was correct or not. Also the settings were all set correctly for my tire size and its wired so should be no interference.

So is 39mph to fast to be true or is that a regular speed for a down hill run?

That isn't an unbelievable speed at all for a steep downhill.

All my rides have hills on them and so I pretty much always hit at least 65 km/hr (40 mph) unless its raining or in the spring and the roads have sand on them (lots of curves on the down hill). This is approaching fast, but fast for me is 80 km/hr. (50 mph).

There is a really good video on Utube of some guys in the tour doing 100 km/hr. Wish I had the link. It needs to be steep to go that fast, you (or at least I) can't spin that fast.

Me: 50mph
Tandem: 60mph

There's always faster.

39 mph? How about 50+ mph ...

I never really trusted my computer till I rode by one of the police "your speed is ___" machines. my cateye was dead on. (as a side note those things are addicting, I kept riding around the block to pass it again and again, I never realized I would work on bikers, but I guess they use the same things for baseball speeds and I am larger than that )

I hit 60km/h (the speed limit) down a small hump (less than 500m) with tail wind today.

I need to find a bigger hill... or deeper valley.

Lucky the road I was on was very smooth cause on the way back I was going down another hill doing about 35mph and had to slow down. Their was to many pot holes and crap on the road for a storm we had a couple days ago. Anyway good to see I got some speed ha.

The fastest decent I've done was 57mph. scary, luckily no turns.

+1 - 39 can be done fairly easily. For reference:

• I've been up around 50 any number of times. Fastest I've ever descended was 52 mph. Hogpen Gap, northern GA. 15% grade, and a mostly straight shot for about 2 miles. I'm a chicken... a number of the guys I was riding with went faster.
  
• Just the other day I hit 41 on a little 3% downhill grade with a tailwind the other day, and I've done 40+ on flats in strong tailwinds.
  
• My fastest sprint that I know of is 36.
  
• My group can run mid-30s in a paceline on flat ground with a decent tailwind.

And those are by no means meant to be bragging... all are only modest numbers. There IS always faster.

I've passed cars on downhills in the mountains. It was either that or ride the brakes. Kinda fun but scary too.

on my solo rides the fastest i regularly hit on the downhills is 40-44mph

anything more than that requires some serious "age" (i.e., grade-age and/or watt-age)

Just for my information in a race (such as the CSC invitational) which is fairly flat what is the average speed?

Like ExMachina, i'll usually hit around 40-44mph on a downhill. Today I hit 51mph on a steep downhill, about 12% grade. my fastest is 54mph which was on the same hill, and I was in a paceline until i hit about 50mph, then I pulled out of the paceline and flew past everyone. Going that fast is a rush.

solo, i would say anything above 20mph is fast. Riders can go way faster than that, sometimes above 25mph.

riding in a group, the average speed will obviously be higher. I would say anything above 25mph is fast, with speeds being in the low 30's for the best riders.

Early on, the announcer was saying they were going about 35 mph.

They might have slowed somewhat as the race wore on, but I'll swear that the lead teams must've been pushing 40 when they dropped the hammer on the last couple laps.

The tires on the Subaru SUV that was riding support occasionally howled & chirped around the corners while keeping up with the breakaway group.

I'm surprised that there were only two crashes, considering how crappy parts of those streets are.

My quick smells like french toast.

39?
I can make 34 on flat ground. My ride to the grocery store gets to 42. I've seen the lower 50s. Not sure exactly how fast, I was a little busy hanging on at the time.

I passed a big shiny Dodge Ram 3500 4X4 going 65 km/hr downhill through some sharp curves once, the driver was real pissed. [I'd ridden that route a 100 times and knew the line though those curves like the back of my hand.]

Depends on what kind of distance you are talking about. Solo 25 miles in 1 hour on an open road with a normal bike is an excellent time. All those 30+ miles in one hour times that you read about are indoors on a smooth wooden track with special time trial bikes.

I've hit 50 on downhills as well - once you get past the "wow this is amazing, but I'm so screwed if I crash now" feeling, the thing that gets to me is how long it takes you to slow a bike down from those kind of speeds.

Can't beat the feeling of knowing you can do that without gasoline.

i was going down a hill at 46mph and a fat guy passed me... and yelled.. physics sucks! lol..

I always say, "Newton is on my side."

My brother and I have a joke. If someone says they can do 30, they can really do 27 consistently. If someone says they were commuting at 20 mph, they mean 17 mph... Everyone will overestimate.

If you're talking about really pushing on the flats, a good non-pro rider can hold 30 mph for a short time.

If you're talking about time trials in the category 3-4-5 level, 23-27 mph is about the sustainable range for winners of races more than a half-hour.

Try looking up some TT race results for flat courses and calculate their average speed.

there's a mile long 5 degree hill about 3 miles from where i live... i've been waning to try it, but, I don't want to climb back up it...