cmill189

I put in my stats and used an average decent around here and got 43mph coasting. Seems pretty accurate to me, I run out of gear at 40 and hit 45 pretty regularly. I hit my fastest ever last year at 53mph. Having a very steep and very long decent is a big help, but I think being very thin and able to put your face at the stem doesn't hurt.

zonatandem

Highest speed on our tandem: 53 mph descending in the White Mountains of Arizona.
Have broken 50 mph many times. Both pilot and stoker 'tuck in' and coast.
Highest speed pedaling on a slightly downhill course racing 2 other tandems: 44.5 mph.
We were running a 56T chainring and 13T cog at that time and we were bouncing on the saddles.

coasting 

I've been up to 58 mph and i do it pretty easily; more easily than I would care to. I just don't look at the computer, tuck in and not touch the breaks ever. It helps if the road is clear and straight.

bjtesch

Where I live it is relatively flat but we do have the occasional big hill. There are two hills around here that I've been at least 55mph on. You pedal until you spin out at something near or just over 40 mph then tuck in and coast the rest of the way. In your tuck you are pretty intimate with the front wheel and just hoping that you don't hit a big rock or hole in the road. If you stay cool a good road bike will be pretty stable at 50+ mph. One of these hills is surprisingly steep and you get the feeling that it is trying to pull the bike out from under you.

I took a bike trip in Utah about 20 years ago. This was a commercial trip and they provided us with heavy touring bikes. I remember we climbed up one hill between the Grand Canyon north rim and Zion national park. Once we reached the summit down the other side was a long descent towards the turnoff to Zion, but not real steep. I spun out at 40 mph or so and coasted a little faster than that. I had glasses on but the wind blast was still pulling the tears out of my eyes and they were streaming back along the side of my face.

mkadam68

+1 Yep, this is me. Hit 52mph on a 1-1/2 mile downhill at a max 8%. 'Course, I'm a clydesdale.

I'm at a loss.

Rx Rider

one of the reservoirs nearby will get me going 55mph easily with zero pedaling. 13% grades will do that for you.

fishymamba

I weigh very little compared to some of the guys I ride with, so this is the only way I can keep up with them on the downhills. I prefer to keep my hand in the drops, so I have access to the brakes.

I have hit 52 mph in less than half a mile of descent. It was down a 14% road, but the first half mile was more like 16%

Fastest I have gone is 57.3 mph down a 8% grade, but I was drafting a van.

AlbertaBeef

Do your best to draft off them... One ride with some very competitive guys a while back I actually sprinted UP the hill to pass the riders so I could really leave them over the other side, and hopefully stay out there... I didn't even look behind me (should've) and one guy managed to hammer it and get into my draft. He stayed with me downhill, when I finally turned around to look (I do NOT turn around when descending at over 90km/h) he was right with me... the guy must've been inches off my wheel.

I've a 50" + chest ... People say that about me... that it's like drafting a van...

SlowOlympian

My guess would be the opposite! I am quite thin. Before cycling I weighed 125 (5'10"), since then I've gained about 10 LBS. On a 5-7% gradeI can pedal up to 40mph, but even with a flat back, nose on the stem, I start slowing down! Not much, I seem to scrub off 1-2 mph, but I don't bomb down the hills like I imagine someone with 80LBS on me would.

Rode with a friend once who has 100lbs on me, went over a big roller, and near the bottom he FLEW past me! This is a 6'ish guy with broad shoulders, and skinny me in the drops pedaling for my life. Oh, and he couldn't hang with me on the flats, so it isnt leg strength.

I think the fastest I've seen is 47mph. Several hills in Oly were 12-17%, but not very long, maybe 300' tall. The 17% had a bad chipseal, with a hard left at the bottom, never had the guts to take it near full speed. Harrison hill was fun, but has 2 roundabouts... And the Beartooth pass is only like 7% at the steepest, but for 10 miles. THAT was a lot of fun! but again, I think I only hit 40-45ish.

Nick Bain

I think the pros have an easier time doing that since they have less upper body mass. When I do it I do not feel stable et al. But im sure it is one of the many risks they take in the tdf.

thump55

This. Your speed over the summit and at the start of the descent has an incredible effect on your max speed.

I posted some useless numbers a while back from a small hill repeat session where I was experimenting with such things as starting speed and aero position. I'm too lazy to search for the post now, but I do remember a huge difference in max downhill speed on the same hill (no pedaling) when starting from a stop, and from just a 5 mph roll.

ENEMY

I've always wondered if people use they're cars no "rides"

digibud

I have to disagree here. I'm a 60 yr old clyde and an ex full time hang glider pilot. I mention it because riding fast down a hill is far from the most dramatic thing I've ever done. I have much more interesting things to "brag" about. I use a Garmin and live in AK where we have some pretty decent hills. I love going downhill fast and work really hard to get into the best tuck a big guy can. My garmin definitely screws up regularly with regard to high speed. Every month I have a few rides where I show 100+mph, but I've also done several rides with and without GPS turned on ( I have a cadence unit too) and have multiple runs down some good hills that I can now claim with some reasonable assurance, are true. In July I did a 47, 49 and 53mph run and I'm fairly sure those, as well as quite a few others in that range are probably true. I know pros in the TDF hit well above these speeds and they aren't pedaling at that point. It just takes a well balanced bike and a good tuck and it's about the only time when extra weight isn't a liability.

nd2010

How I get over 60 mph without pedaling: it's easy and I could do it every day if I wanted to. I just press the gas pedal and the car goes to 60 mph easily.

On a bike, that's a little harder. The fastest I've ever gone was 47 on an 8% grade. It was scary. I was hoping there would be a speed trap since I wanted a speeding ticket because I was breaking the 40 mph speed limit. I would pay it for bragging rights.

You could draft a vehicle moving faster than 60 mph. But if that vehicle suddenly stops, you're toast.

BarracksSi

Mine gave me over 3,500 mph last week. I was completely unable to figure out where it happened in Garmin's player, either.

BarracksSi

I've experienced this, too (normally as the bigger bullet..). I figure that a similar aero position used by both riders is fairly equivalent, so the drag on each rider is pretty similar, too. He's got more force due to more mass plus gravity, though, so he's got more energy left over for speed after the drag takes its share.

Dr. Banzai

I'm guessing you didn't do well at science in school.

Brian Ratliff

Better than you, apparently.

Rx Rider

I just learned how to spell science recently, pretty proud about that.

AK404

Thank you for confirming this for me. I've been using Strava for fun for the past few days and couldn't figure out for the life of me why my max speed wasn't going up even though I could swear I've been getting faster. Now I guess it's time for me to buy a new/working computer.

Dr. Banzai

2 riders or equal surface area but different weights will descend at the same rate. A bigger, heavier person will actually descend slower due to frontal area. Being heavy will not make you go faster downhill.

chasm54

You're wrong about this. It isn't the same as dropping two stones of a different weight from the same height, it's a question of momentum, which is velocity x mass. The heavier rider will have a greater momentum than the lighter one, so as their speed increases he/she will overcome the wind resistance more effectively: especially since, being three-dimensional objects, their surface area relative to their mass will be smaller. Big riders descend faster. Everyone observes it in the real world, and the physics supports their observations.

DannoXYZ 

You need to study your physics and go out and ride with some light and heavy riders. A 100kg rider will NOT present double the frontal-area to the wind as a 50kg one. Because surface-area increases only to the square-power, while mass increases to the cube-power of volume. You can add 100% more mass, but surface-area will only increase by 58% total. And most of that increased surface-area will be reduced in a tuck. A 100kg rider will end up presenting only 20-25% more frontal-area to the wind as the smaller one, but will have 100% more kinetic enery from the pull of gravity.

I used to do hill-repeats on a 7-mile hill in Santa Barbara with a backpack. At the top, I'd load it up with 10-15kg of rocks. This consistently added 8-10kph more top-speed on the fastest straight about 1/2-way down the hill. I'd dump out the rocks at the bottom and go back up with an empty backpack.

carpediemracing 

I always wonder why people post theoretical stuff. Theory is great but it doesn't work if it isn't applied correctly or there are other factors in play.

I went from being a pretty good descender (I'm 5'8", low on bike, and I was up to 215 lbs at one point, and raced at 180-190 lbs) to a terrible one. I dropped down to just under 160 lbs for the 2010 season. I found to my horror that I had to pedal furiously to stay with everyone. My frontal area was a little bit smaller - I was skinnier - but my helmet size, glove size, shoe size stayed the same. I had a different frame (it was more narrow and shorter in height so probably more aero, and it happened to be about a pound heavier) so I should have been faster. I used the same wheels, tires, bar, stem, saddle, post, cranks as the prior bike, and even the same fork off two bikes prior to that.

I also cornered the same before and after, and my issues were on straights, not the corners - I could still dive into corners and hold my own with anyone around me.

Basically I had the same frontal area, a bit smaller fine, but basically the same. I had 30-50 lbs less mass. That's huge. That makes a difference.

Now that I've gained back almost 20 lbs I descend a lot better haha.

Regarding the tuck positions - I've tried them all (except that one with stomach on saddle lol) and I've found the following:

1. The one where the butt is in the air seems to be the best for all round handling. I can go from a full tuck in that position to max control in the drops in less than half a second. Before anyone says that's impossible, go out and do it. The bike is amazingly stable at speed and you can easily, even one hand at a time, go from a 100% tuck to being on the drops and grabbing brake in a half second or less.

The disadvantage to that butt in the air position is that your legs have to hold your body up, and, for most people, you use your legs to clamp your frame. You want to keep the frame from flopping back and forth else you can set up a shimmy and clamping it between your legs really helps. This means the position is tiring. If I'm cramping or otherwise exhausted I have a hard time holding this position for more than 10-15 minutes. This is especially true if my upper body is fatigued (my legs seem okay, it's my arms that give out).

2. The lower position (Garmin rider picture) is great if you're really tired or you have a very long descent. I'll use it in sections coming off Palomar - that's a 33-35 minute descent for me - because my arms and legs are already tired from the 4+ hours it takes for me to ride to the top of Palomar.

I've seen this position used in time trials as well, sacrificing a little bit of speed to rest the legs. Again, before anyone cries foul, the clip I saw was of Taylor Phinney when he won the World Championships. It appeared he used this position to enable him to go much harder just before, then recovered on some relatively short but fast descents.

Also, and this is theoretical so you can bash me, based on watching some much taller riders descend (Phinney but also friends of mine who are 6'2-6'4"), this position is much, much lower than sitting on the saddle. In fact their saddle ends up the highest part of the bike/rider unit. Phinney's back is just a bit lower than his saddle if I remember correctly. This reduces their frontal area as much as possible, letting them descend faster. The riders that use the first position tend to be smaller (like me).

Disadvantage is because you don't have a good "grip" on the frame, if you hit a bump or something the frame can wobble. This can lead to a feeling of instability. It's the same as diving into a corner out of the saddle - it's better to have your weight on the saddle because your butt holds it in place. If you watch someone try and coast through a sharp curve while out of the saddle the bike bounces around a lot. When in the saddle the rider's mass dampens the movement. With aero tucks this position is not as stable because you don't have as good a grip on the bike overall.

carpediemracing 

For the OP - once you hit about 40 mph on a decent sized downhill it's aerodynamics that's holding you back. Remember that the biggest limiting factor in bicycle speed is aerodynamic drag - that's why drafting a car or truck will allow a rider to go significantly faster (the record is over 160 mph behind a vehicle). I know the record set earlier than the current one (i.e. the John Howard record of 158 mph) required something like a 450 hp car to make a big enough hole in the air for the rider to get a draft.

Therefore, unfortunately, the only way to truly increase speed when on your own is to get into a tuck. It's possible that when you untuck to pedal you'll actually slow down - I know this happens to me once I'm at about 47-48 mph.

The tip about sprinting over the top of the hill is valid too. The highest speed I ever hit came after I started the descent sprinting up to about 45+ mph before I tucked. Due to the kind wind and a closed course with marshals, I hit well into the mid 60s before the road flattened out (that's a one time thing for me - I rarely break 60 and haven't hit over 55 in a long time).