fastest you've gone?

[philw]

I just looked up the bike speed records, the fastest speeds seem to be on snow, perhaps because of pitch and length?? Or maybe just for saftey or just lake of true grade, not many roads in the us are steeper then9%. but lots of groomed trails are.

The bikes I've seen ridden at serious speed were run on an FIS speed-ski course (it's not an official FIS sport but it's supervised by them). Those slopes are stupidly steep and very well prepared for the purpose. I've never seen a road *anything like* that steepness, and I've ridden a lot of roads. It's a different concept.

I've never seen anyone ski/ snowboard/ cycle at anything like those speeds, although I'm sure the kids at my local school have GPS devices which "prove" otherwise.

Here's one I shot..

http://philwigglesworth.net/images/library/snow_sports/speed/images/A19S21438.jpg

[Neil Gendzwill]

I know it is all relative.. but on my pedal bike 45 is scarry fast and I got brakes and very fast tires and I think rolling friction on a bike is better than a sliding friction on a snowboard.

A really steep road is 10% grade, less than 6 degrees. A steep-ish blue run is 20 degrees or so. No comparison.

[Bordy]

The bikes I've seen ridden at serious speed were run on an FIS speed-ski course (it's not an official FIS sport but it's supervised by them). Those slopes are stupidly steep and very well prepared for the purpose. I've never seen a road *anything like* that steepness, and I've ridden a lot of roads. It's a different concept.

I've never seen anyone ski/ snowboard/ cycle at anything like those speeds, although I'm sure the kids at my local school have GPS devices which "prove" otherwise.

Here's one I shot..

http://philwigglesworth.net/images/library/snow_sports/speed/images/A19S21438.jpg

Nice shot Phil, That rear tire is punching deep....Did any of thoose guys dig in the front and go over the bars?

[OhD]

Just drove 8 miles to work with stretches of cruise at approx 35, 45 and 55mph. Allsport reported max speed of 56.8. Seems accurate as the speedo.

[philw]

Yeah, I think GPS is generally pretty good for road-use, it's fairly predictable most of the time, and you can average over a respectable period, although some of them do "ring" on the corners.

Nice shot Phil, That rear tire is punching deep....Did any of those guys dig in the front and go over the bars?

Not from what I remember - they were stupidly good in a straight line. Some people did wipe out right at the bottom of the deceleration zone; I think they were skiiers. The scary bit was that the crashes I saw were right at the very bottom, when people had almost stopped. Yet they still crashed hard and violently fast into the house-wall sized inflatables there. I think they were all Austrian, so completely crazy anyway. Someone did 132 klicks on an airbed (which was a world record at the time).

[OhD]

"Ringing", if you mean overshooting ant taking a few oscillarions to settle, is caused by the logging program interpolating a path between points or a velocity plot between calculated velocities (calculated using either the path spline chord length or a straight-line point to point velocity) using a polynomial or spline curve fitting algorithm. To minimize error, you may be able to set the location update frequency to something less than a turn radius or a fraction of a turn time, depending on whether your logger uses distance or time intervals. I used 10' riding and 20' driving. Higher frequency burns batteries faster.

Dennis

[Neil Gendzwill]

10 seconds is nowhere near fast enough for riding, if you want to track a carver's path. If you are making a 10m radius turn at 20 km/hour, you are going to complete that in about 3 seconds. You could link 3 of them together within one sample cycle.

Most of the GPS boxes used in cars for track-day logging sample at 10 Hz, and cars are not taking anywhere near as tight/quick turns as we are. There's one available that samples at 100Hz and supplements with an accelerometer (OXTS RT3000). Those boxes have the advantage of being powered externally though. I'm not sure you could practically sample GPS fast enough for riding without having an external battery pack for the device.

[kieran]

there are two sections of good downhill tarmac near here, where i can easily hit 50mph+ on 700x23c's. at the local .. lift-served munro, there is a route between two pomas where i usually straightline, and the gps frequently records 41 - 44 mph.

even though i'm only wearing two bits of lycra, a helmet and a grin, i feel safer on the bike.

[OhD]

I was updating at ten and twenty FOOT intervals.

[poutanen]

I board with GPS running on me all the time (I like to push my daily distance and vertical meters)... Of course there are random spikes in the data of 500+ km/h, but I've seen reasonable sections of the graph as high as a sustained 80 km/h for 10 seconds or so. Seems reasonable to me...

edit: I should mention I'm aware of the limitations of a tracklogging GPS, but the one thing it is is consistent with itself. For doing personal bests (distances and vert) I can safely say that day X was longer than day Y for me. I just can't compare my stats to other people accurately.

[Neil Gendzwill]

I was updating at ten and twenty FOOT intervals.

How do you update at a distance interval? The GPS doesn't know how far its gone until it takes the next measurement. You'd have to extrapolate when to sample based on the last speed ... I don't know why anyone would design it that way.

[philw]

Yes, didn't hugely want to go there again, but one has to know the limitations of one's gear. Ringing: programming at the device level I found that different manufacturer's devices dealt with interpolation quite differently. You couldn't change that as it was built into the device, so testing and then picking the right one was important.

Bikes are fast, but on snow everything *feels* faster, probably because we're all used to tarmac at speed so it doesn't feel as fast (say) as flat-water on a windsurfer or whatever.

[Willow 15]

Not sure how accurate app is, but it was fast.

[kieran]

How do you update at a distance interval? The GPS doesn't know how far its gone until it takes the next measurement. You'd have to extrapolate when to sample based on the last speed ... I don't know why anyone would design it that way.

some gps' (usually in a phone) offer a 'minimum distance between points' option. though i don't know if that's what is being referenced here.

[poutanen]

some gps' (usually in a phone) offer a 'minimum distance between points' option. though i don't know if that's what is being referenced here.

For what it's worth, I use Trekbuddy on my phones (as does my GF) and it allows you to select intervals in number of seconds. Then it just records a tracklog file which I upload to garmin connect... So far so good. Did 1150 km on the snow last year! :) Biggest day I had was just under 10000 vertical meters.

[Neil Gendzwill]

some gps' (usually in a phone) offer a 'minimum distance between points' option. though i don't know if that's what is being referenced here.

I would strongly suspect that is on option for how many points are stored, rather than how many samples taken. So sample every X seconds, and only store the ones that indicate you've travelled the configured distance. Saves on storage space, not so much battery life.

[OhD]

I see at least two approaches:

1. The distance interval for fixes is extrapolated forward based on recent observed speed. Fixes are taken at times corresponding to the estimated time to travel the specified distance interval from the last fix.

2. If the instrument can update position at some very high frequency, the interval for saved location data could be specified and the program would just copy the location coordinates closest to the specified time or distance interval into a table for use in plotting and postprocessing statistics such as the speed/distance graphs, MAX speed figure, etc.

I don't know which is used in practice. Allsport GPS Pro settings include "Update Distance - Distance threshold for GPS points while recording.." in feet.

I don't know what kind of path-fitting algorithm is used (presumably a regression-fit curve, not forced to hit any point).

Altitude, latitude and longitude are calculated. Altitude may have two solutions if only three satellites are visible but one is subterranean and rejected.

Motorola claimed horizontal accuracy of <10m in continuous navigation and speed accuracy <1m/s (2.24mph) for their GPS receiver chip as of 2007.(http://www.motorola.com/web/Business/Products/M2M%20Wireless%20Modules/GPS%20Module/_Documents/_staticFiles/GPS%20Module%20Data%20Sheet.pdf)

Cruising a nice wide-open groomed run with moderate pitch is going to subjectively feel slower than the same speed on a narrow run, a bumpy run, or a narrow roadway lane. Tapping a death cookie with a hand or smoking a glove on frozen corduroy at 50mph puts things back in perspective, and should induce a great deal of respect for anyone who can corner at such speeds on two wheels and a puck!

[C5 Golfer]

Bikes are fast, but on snow everything *feels* faster, probably because we're all used to tarmac at speed so it doesn't feel as fast (say) as flat-water on a windsurfer or whatever.

we cannot feel velocity/speed, we can only feel acceleration.

[poutanen]

we cannot feel velocity/speed, we can only feel acceleration.

Methinks he was meaning perception. We can perceive our speed relative to our surroundings. Sitting in a plane doing 500 mph above the clouds "feels" like sitting at the kitchen table, but we perceive the speed to be about the same as doing 55 mph on the highway.

Riding hard through a narrow trail makes us perceive that we are going faster than doing the same speed on a wide open trail.

[C5 Golfer]

Methinks he was meaning perception. We can perceive our speed relative to our surroundings. Sitting in a plane doing 500 mph above the clouds "feels" like sitting at the kitchen table, but we perceive the speed to be about the same as doing 55 mph on the highway.

Riding hard through a narrow trail makes us perceive that we are going faster than doing the same speed on a wide open trail.

you are right of course -- similar to when I ride my Corvette at 70 and I ride in my son's big a** Dodge truck at 70 -- seems we are going slower in the truck cuz we are so far up/off the highway surface

[poutanen]

you are right of course -- similar to when I ride my Corvette at 70 and I ride in my son's big a** Dodge truck at 70 -- seems we are going slower in the truck cuz we are so far up/off the highway surface

Only thing I don't get is how that translates to a bike. I used to ride a sportbike back in the old days, and had the bike above double the speedlimit on roads and it seemed normal. Had a tank cam going at the time and when I got home and watched the video I realized I was going obscene speeds in places I didn't expect.

Did the same thing with a helmet cam snowboarding, and when I feel like I'm flying it looks like I'm just out for a sunday cruise on the board. Doesn't help that the helmet cam is a wide angle, and my head stays relatively stable while the rest of my is rocking back and forth underneath.

[C5 Golfer]

Only thing I don't get is how that translates to a bike. I used to ride a sportbike back in the old days, and had the bike above double the speedlimit on roads and it seemed normal. Had a tank cam going at the time and when I got home and watched the video I realized I was going obscene speeds in places I didn't expect.

Did the same thing with a helmet cam snowboarding, and when I feel like I'm flying it looks like I'm just out for a sunday cruise on the board. Doesn't help that the helmet cam is a wide angle, and my head stays relatively stable while the rest of my is rocking back and forth underneath.

Dunno - its friday and I need a glass of red wine..

But here is a phunny thought... what would happen on I-90 -- Montana Wyoming areas... if all the cars and trucks and motorcycles had no speedometer. wonder what the traffic pattern would look like????

[kieran]

Dunno - its friday and I need a glass of red wine..

But here is a phunny thought... what would happen on I-90 -- Montana Wyoming areas... if all the cars and trucks and motorcycles had no speedometer. wonder what the traffic pattern would look like????

probably a concertina effect. all it takes is one twit stamping on the brakes and you get a compression waveform moving in the opposite direction to traffic flow.

[C5 Golfer]

probably a concertina effect. all it takes is one twit stamping on the brakes and you get a compression waveform moving in the opposite direction to traffic flow.

Not sure of that... I know you are in Scotland.. Coming there soon BTW. But the area to which I am referring is a wide open flat straightaway highway with very few autos. Used to be years ago -- no speed limit there. My question is more related to this area and no speedometers to keep most everyone with in 10-15 mph. I wonder what the spread would be if we only drove by feel of what is safe.

kieran-- different subject -- yes coming to Scotland and Ireland to play golf for 8 days next April.. I just have to get thru this snowboard season with no broken bones so I will limit my fast speeds at Whistler accordingly.

[philw]

we cannot feel velocity/speed, we can only feel acceleration.

And not one of you can feel it?

I'm sure you can...

First off, start moving. Then open your eyes. Observe all that stuff whizzing past. Broadly speaking, and if we take Newtonian Physics as an approximation, and if you look at stuff which is unlikely to move itself in any way which is meaningful, then the faster that stuff seems to be going, the faster faster you're going.