Author Topic: Question: What is "high speed" wrt bicycling?  (Read 5716 times)

Danneaux

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Question: What is "high speed" wrt bicycling?
« on: June 28, 2012, 11:06:35 PM »
Hi All!

My question: What constitutes "high speed" when the term is applied to cycling? In other words, what speed does a bicycle need to travel to be traveling at "high speed"?

This is not a frivolous question or carelessly phrased, and directly relates to my investigations of speed wobble and shimmy as well as bicycle lighting. It is made more complicated by opinion, semantics, and the lack of a universally-defined velocity threshold.

I've scoured the InterWebs, done a word/speed frequency analysis, tabulated the results, and it seems 30mph/48kph is the magic threshold at and beyond which all bicycling speeds are regarded as "high". Below that, we have various speeds called "fast", "regular", normal, and "just riding around" < -- A term used by plaintiffs who make warranty claims when their bikes break. Peter White nibbles 'round this magic figure when describing speed-appropriate lighting for nighttime downhills. Others seem to hover 'round that same speed in their discussion of frame geometry and suitability for purpose.

Now, I'm asking the collective Thorn Hive Mind if you concur or have heard of other definitions for "high speed" when applied to bicycling.

Does 30mph/48kph and above sound about right for "high speed" on a bicycle?

Thanks in advance. This is all going somewhere, but will take awhile, some computer and real-life simulations, and some machine- and torch-work to percolate to fruition. For science! For physics! To keep Danneaux out of trouble arising from boredom!

Best,

Dan.

triaesthete

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Re: Question: What is "high speed" wrt bicycling?
« Reply #1 on: June 29, 2012, 12:35:15 AM »
Dan, surely you don't have time to be bored?!

Would it help to break this one down a bit into gravity and human powered speed? 30mph average speed for a time triallist is a serious achievement (ie 20 min/10miles)but no great shakes on a descent.

Modern lighting seems to have reduced the day/night contrast though.

Imagine 30mph on an Ordinary :o

I think the old English legal offence of "furious riding" had a contextual element too.

Can't wait to see where this is going,
Ian


stutho

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Re: Question: What is "high speed" wrt bicycling?
« Reply #2 on: June 29, 2012, 01:10:40 AM »
On the flat with no tail wind anything above 25mph I would thing of as high speed 'cos I can't go that fast!!

On a slope I regularly exceed 40mph so high speed must be higher than this.  I did once get up to 60mph - that was brown pants scary fast.  I wont be trying that again!  So for me, down hill, 'high speed'  is about 50mph.

Poll?   


Danneaux

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Re: Question: What is "high speed" wrt bicycling?
« Reply #3 on: June 29, 2012, 01:23:50 AM »
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Can't wait to see where this is going...
Yeah, me too, and I proposed it!

Here's the thing...

When people (on the 'Net, so by definition it must be true, right?) talk about speed and bicycles with regard to geometry, handling, and lighting, they often seem to divide their discussions into "high-speed" and "low-speed", then postulate their theories, relate their data, and present their findings from there.

Over and over, this same phrase or term comes up when discussing bikes.

Unfortunately, people rarely quantify "high-speed" with a number. Drives me nuts, 'cos without numbers, it makes their data and conclusions "slippery" and almost impossible to replicate except in general terms. One person's "high-speed" is another person's "tootling along".

Writing and asking has gotten me nowhere.

I -- of course! -- want to quantify my data and relate it to what I've read, so I am trying to determine what "high-speed" is by contemporary cycling convention. What does it mean today? For example, I recently read some ad copy for a carbon bike that touted its "unsurpassed high-speed handling". Well, at what speeds? Sherpa did really well screaming down Green Hill yesterday loaded to the guards, and he's a touring bike. The tandem does really well at just over 62mph/100kph (and maybe more, but the traffic light at the bottom of the hill turned red and put an end to the fun. My then-86-year-old stoker, otherwise known as "Dad", was up for more and waving me onward until the light changed). I'd call that "high-speed". Tout-Terrain seem to think "high-speed" lives somewhere around 18-20mph/29-32kph. In his headlight comparisons, Peter White seems to think "high-speed" is at or over 30mph/48kph.

The little I've found where numbers are tossed about seems to indicate 30mph/48kph is the point at which a bicycle (and rider atop it, hopefully) definitively enters "high speed". If I can get some consensus on that, I can go somewhere in relating my shimmy data to others' and the lighting data as well.

None of this would matter much to me if my background weren't in research design and methodology. I did the pioneering work in a particular sub-field of the discipline, and there really is value in getting things nailed down. Otherwise, everything is pretty much a shot in the dark. Because I occasionally carry unusually heavy loads on very poor - or no! -- roads, I am finding some interesting things about bicycle handling I haven't seen reported elsewhere. I think the weight and road surfaces amplify certain handling characteristics and make them more clear and apparent than they would be otherwise. Some of thesr characteristics hold constant regardless of speed, and some are speed-dependent.

Apart from the rider (a huge variable right there), a lot of factors determine a "good-handling" bicycle and its suitability for a given purpose and intended use/speed range. A bike may handle well at any speed or with any use, or only within a range of speeds and conditions that may be unfortunately narrow. Rider A may never have a problem because his speed tops-out at 25mph/40kph and life is Good until the day he braves a downhill at 35mph/56kph and the wheels fall off, so to speak. Rider B may have a bicycle that rides on rails at 30-40mph/48-64kph, but curses the thing when it wanders up the drive to the shed and nearly throws him into the weeds.

I suppose it is a bit like two people who each buy the same computer. One keeps it original, uses it only for light tasks, and thinks its a speed demon. The other edits huge video files or does 3-D renders and compares its performance to watching paint dry. In this case, performance benchmarks get you in the game, but they don't guarantee equivalent experiences or performance if the use differs.

I suspect I have asked an Imponderable, but that "high-speed" term must have some basis in factual data. I'd sure like to find it and it would sure be nice if there was some comparability to make reasonable comparisons. For science! For physics!

Best and thanks,

Dan. (who thinks Stuart has a great idea for a poll...)

Andre Jute

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Re: Question: What is "high speed" wrt bicycling?
« Reply #4 on: June 29, 2012, 01:27:22 AM »
Short answer: I don't know. But I'll throw some second-hand data into the pot.

The German legislature seems to thnk anything over 25kph/16mph is too fast to entrust to your average cyclist; they limit pedelecs to this speed, and the rest of Europe has followed suit.

Many of the roadies that I know who commute to work seem to think that if you can't maintain 20mph, you're a danger to yourself and to other road users.

The same roadies brag about being able to maintain 25mph, especially in training groups. I would humbly submit that, as the purpose is training for racing, that is already fast.

So your 30mph seems a bit high, Dan.

***

These days 60kph/35mph is about as fast as I go downhill. That is already a good deal faster than your average cyclist should go, because he is an incidental, intermittent, occasional rider. Bike integrity and maintenance already figures very large at 60kph, and skill and experience too, and they ain't got it.

Andre Jute


triaesthete

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Re: Question: What is "high speed" wrt bicycling?
« Reply #5 on: June 29, 2012, 01:52:03 AM »
Dan, are you trying to turn an art into science? The thing I love about building bikes is the intuitive, heuristic and creative element and the joy of getting it all to work

Group and solo rider speed ranges would also vary massively.  Andre mentions roadie training groups at 25mph and it's true. I have vivid memories of a big chain gang ride in the years before bike computers when a chap leaned out of his car window and said "Blimey! Do you know you're going at 35mph!"

What you'll have to do carefully and in the name of science is follow the sports scientists into power metering as rider Wattage is probably the nearest we get to a "true" number in all this.

Or you could do it by the seat of your pants dyno with a suffering calibration!

Ian

Danneaux

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Re: Question: What is "high speed" wrt bicycling?
« Reply #6 on: June 29, 2012, 01:57:15 AM »
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Dan, are you trying to turn an art into science?
Eh...what gave me away?  ;)

All the best,

Dan.

JimK

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Re: Question: What is "high speed" wrt bicycling?
« Reply #7 on: June 29, 2012, 02:29:30 AM »
Apart from the rider

This recent posting:

http://janheine.wordpress.com/2012/06/13/bicycle-quarterly-performance-of-tires/

got me thinking again about tires... along with Dan's shimmy trials. What Jan Heine doesn't seem to take into account is rough roads. But rough roads make the rider really important, and also the precise nature of any luggage and how that is battened down. A bike, especially a lightweight bike, is going to handle rough road very differently depending on whether the rider has his/her weight on the saddle or they've suspended themselves loosely up on the bars and pedals. Especially when clipped in, a rider can unweight the bike and even lift the bike right off the ground to reduce the shock and vibration from obstacles on the road. How can one define "rolling resistance" for a tire with this kind of variability?

That book I read recently, Distance Cycling by Hughes and Kehlenbach, discussed cornering technique: on dry pavement lean the bike more and the body less, while on wet pavement lean the body more and the bike less.

What are the hazards from high speed descent?

Avoiding obstacles: braking to stop before reaching them, hopping the bike to jump over them, steering the bike around them, accelerating the bike to get out in front of them. In any case, seeing them, being aware of them, having the quick judgement to choose how to avoid them.

Yes and also bells and lights to warn the obstacles to stay clear!

Handling curves, rough pavement, loose pavement.

Danneaux

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Re: Question: What is "high speed" wrt bicycling?
« Reply #8 on: June 29, 2012, 03:17:50 AM »
Some very good points, Jim.

Another thing to keep in mind wrt to bike handling and speed is the rider's placement on the frame. Thorn's "short" frames are designed for use with drop handlebars and anticipate the greater forward "throw" that comes with the forward reach of drop handlebars. However, the short frameshave a shorter front-center, so the rider on the brakes hoods (nearly everyone, most of the time) places more of his or her weight over the front axle than the user of straight 'bars. This greater forward distribution affects weight distribution and balance. Lowers center of gravity compared to an upright rider with straight 'bars, too.

Jim, if you and I were the exact-same height and weight and limb dimensions, we'd sit differently on otherwise identical bikes if we used different handlebars with frame geometry optimized for each type of 'bar.

It doesn't take much thought to figure this would undoubtedly affect propensity to shimmy. It is also bound to affect handling "at high speed" and differences in body position will of course affect top speed due to aerodynamics -- an upright position has a higher coefficient of drag than a tight tuck on the drops.

Yet another factor in perceived and actual handling as well as actual speed potential is handlebar width. Not only does a change there alter placement of weight laterally, it also affects body positioning and aerodynamics. I have had a lot of fun over the years, trying various width handlebars on my other bikes. It is amazing how the actual width affects handling and perception of same. Wide 'bars can stabilize steering...or make it feel incredibly twitchy at low speed, all on the same bike and for a given amount of trail. Depends on whether you have to manhandle heavy front panniers and an HB bag, too, and the road surface, as you keenly observed.

Jan has done some fantastic work on rolling resistance, but his research has limitations, as all studies do. Because he is primarily a randonneur, his work, research, tires and applications all reflect his interest in that facet of cycling. He has made a tremendous start, but it is only a start, and we need others to follow and build from there. Jan's results have general application, but are not universal.

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What are the hazards from high speed descent?
Um...falling? :D No, you ask a very good question, Jim, and aerodynamics come into play. I found the fluttering of my Ortlieb HB bag map case was good for peeling 1.1mph off my downhill speed with identical wind conditions and all other variables held as constant as I could. Placing a hand on it or removing it entirely had a noticeable and measurable effect. I tried a number of different positions as I descended, to see if they would induce shimmy. I was conscious that each position change affected not only aerodynamics and center of pressure as my speed approached maximum; those same changes also affected my weight distribution. If I could have managed 20 runs yesterday, I would have. As it happened, winching the lot up to the summit three times was enough on a hot afternoon. More runs are scheduled with the reversion to 2.0 tires and, eventually, a return to the Surly Nice Rack (Rear) as I deconstruct the shimmy solution to find the root cause.

One more observation wrt to my top speed yesterday: Compared to a bare bike, the bags did increase frontal area, but the effect was not as great as I had imagined. I'm wondering if they smoothed airflow around my legs and torso. I was lucky to have nearly still air for my runs (I carefully timed my runs to coincide with minimal wind speeds), but I would like to compare Sherpa's terminal velocity bare vs. loaded and see how they compare. His loaded maximum was very close to that of my unloaded rando bike, and I was still doing a good 48mph+/72kph+ on each as I rounded the corner to the flat section before braking heavily for the stop sign.

Man, there's a lot of variables!

Best,

Dan.

JWestland

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Re: Question: What is "high speed" wrt bicycling?
« Reply #9 on: July 13, 2012, 07:32:00 PM »
It depends on the group (cycling style, cyclist age, type of cyclist, bike ridden, roads ridden etc) you ask too...and if they are going downhill :D

Captain slow: 10 miles an hour average
Me: HURRY UP!!!! I AM TRYING TO GET TO WORK

Me: 15-22 miles an hour average (fixie, Thorn)
Road racer: HURRY UP!!!! CAPTAIN SLOW!!!

Dutch commuting cyclist: 10 miles an hour average, talking on cell phone, with 10 KG of shopping/beer and a passenger at the back.
Me: I love my home country. But in the UK this is quite rare.

Road racer: 22 miles and up, and way more an hour going downhill
Me: Puffing behind, contemplating a carbon bike and cycle computer until sanity returns
Pedal to the metal! Wind, rain, hills, braking power permitting ;)

Danneaux

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Re: Question: What is "high speed" wrt bicycling?
« Reply #10 on: July 13, 2012, 08:30:08 PM »
Wonderful, Jawine; I'm still laughing!
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Captain slow: 10 miles an hour average
Me: HURRY UP!!!! I AM TRYING TO GET TO WORK
And, if they were driving a car in these parts, they'd also be wearing a hat. Hat-Wearing Car Driver is code for They Will Be Slow. Except when you attempt to pass, at which time they do a wonderful job imitating Michael Schumacher's F-1 pass-blocking techniques.
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Me: 15-22 miles an hour average (fixie, Thorn)
Road racer: HURRY UP!!!! CAPTAIN SLOW!!!
Yaaay! I can keep up with Jawine! I can keep up with Jawine! (I had my doubts for awhile there after hearing the gears you pull...hummingbird revs on my part make up for it, apparently).
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Dutch commuting cyclist: 10 miles an hour average, talking on cell phone, with 10 KG of shopping/beer and a passenger at the back.
Me: I love my home country. But in the UK this is quite rare.
Or, they'll be about 90 and on an Oma bike. Yeah, I love the NL as well. The one thing that really irritated me was the recent allowance of motorized scooters on the bike paths. They all had bumblebee extractor exhausts with their two-cycle engines. I think they cost me some high-register hearing. And...the mini-cars! As I recall, they had something like a 40kph limit on them, but cars?!? On the fietspad? That's me in the photo (with stuffed jersey pockets)and a particularly nice example of minicar-on-path. Can't draft 'em 'cos they slam on the brakes unpredictably.
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Road racer: 22 miles and up, and way more an hour going downhill
Me: Puffing behind, contemplating a carbon bike and cycle computer until sanity returns
A Dutch Junior Team member very kindly let me draft her outside Schoonhoven as I was plowing into a headwind. For the first time, I knew firsthand why I always have a string of Klingons (cling-ons) behind me when I take the tandem. Tandem = windbreaker.

Thanks, Jawine, for a great post. I'm still trying to figure out the "what is high-speed on a bicycle?" question as I go through the commonly-published trail and geometry figures I've run across online. When trying to figure out and document my shimmy problem, I found some speed-specific handling traits at <9mph/15kph, at 12-15mph/19-25kph, >16mph/25kph, and at about 30mph/48kph. And, of course, at speeds well beyond that (53mph/85kph). By any number of definitions, my shimmy problem is a low-speed shimmy that also manifests at high speed. All is relevant to discussions of geometry and trail, where high-trail is regarded as providing lively low-speed handling and more secure at high-speed (that phrase again!), neutral trail being well, neutral, and low-trail being very stable at low-speeds but having the nasty characteristic of losing contact-patch stability at high-speed (again!) and being more prone to wobblyosisTM (Shopping Trolley Syndrome) when humming right along.

Best,

Dan.
« Last Edit: July 13, 2012, 08:38:39 PM by Danneaux »

JWestland

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Re: Question: What is "high speed" wrt bicycling?
« Reply #11 on: July 14, 2012, 01:54:25 PM »
Ah yes old/disabled people drive those small cars, they have the engine of a scooter (maybe slightly more powerful ;)
Some scooters have their engine drilled for more power, it's not legal, but it definitely increases the racket! The police actually occasionally does sound checks on them in NL, but Dutch people tend to em be liberal with some rules, if they can get away with it.

I find the Captain Slows on bikes also do manoeuvrings to stop you overtaking them! :)
Bit like track cycling really, if there was a strategy behind it....

Lots of pavement crawling here in the UK, some hilarity when:

I caught somebody on the pavement with a helmet (safety first eh?)
There was talk of a guy who's not only a Fakenger (eg fake messenger, right bike, right clothing all super expensive) and cycles fixed but...on the pavement! They dubbed him "The Pavenger"

Maybe I do go faster than 22 miles an hour on average? I might...ah who cares to find out means a cycling computer and we all know where that leads too...though I really do want to break the 30 mph speed limit on my work to work, I did 18mph on The Beast (heavy bike with child seat) so...

All that lawn drum rolling you do it great for the hamstrings btw! :) Told you that you are stronger than you think  ;D

Hm I wonder if there's some Maths (tm) calculations online that can help you model the Wobbliosis problem?

As I read your tale on Rake and not sure how it works from a maths POV (as the problem occurs at low speeds, then goes away, then can re-occur at higher speeds) Something about a spring and a ball apparently...

RE speeds I would model it based on the community/use, so in Touring community, with loaded touring, eg what YOU do, what speed is:
Low
Average
High
(if a step size of 3 is even enough for such a problem, you're the expert here)
And
How Frequent said speed is cycled, again with a certain step size, eg low 20% of time, average 70%, high 10%?

Also as is the shimmy really the same, is the low speed one exactly the same as the high speed one? Maybe it's on a different frequency? As it could have a different root cause maybe? (I am guessing here...never had a shimmy on any bike I owned...)

I wonder if there's a mathematical formula somewhere that can bring some new insights, sometimes looking at an idealized model can give one some new ideas...or maybe not and maths should stay well out of cycling ;)
Pedal to the metal! Wind, rain, hills, braking power permitting ;)

RobertL

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Re: Question: What is "high speed" wrt bicycling?
« Reply #12 on: February 07, 2013, 07:13:07 AM »
My 1986 MTB which has been my only bike since new (an RST is on order), averages around 12~13 mph but will reach 35 mph downhill without any issues. The 36 spoke Arayas plus Schwalbe 1.95 tyres cope with potholes at speed which, I would suggest is a boundary line for high speed - ie at what speed do you bottle out if you had to take a pothole with a risk of losing a spoke or a wheel collapse at speed. The other condition would be speed exceeding braking ability, especially in the wet. The final condition would be ability for the helmet to protect to you on a head on collission. With these in mind I would suggest speeds over 18~20 mph might be classified as high.

It will be interesting to see if the RST gets my average speed to shift up, 14~15 mph would be nice and reduce my commute to 1 hour 15min  - although I doubt I will ever reach Jawine's speed!

Danneaux

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Re: Question: What is "high speed" wrt bicycling?
« Reply #13 on: February 07, 2013, 07:21:13 AM »
Hi Robert!

Welcome to the Forum. Good points, all, and some overlooked in the discussion til now.

Congratulations on new Thorn ownership; another RST is nigh! Very much looking forward to any photos of it in the gallery if you wish to share.
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I doubt I will ever reach Jawine's speed!
I doubt many of us will; she is remarkable in our group!

Best,

Dan.

RobertL

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Re: Question: What is "high speed" wrt bicycling?
« Reply #14 on: February 07, 2013, 07:37:27 AM »
Will do, it is the cobalt blue with an Alfine which has been on the website recently - serendipity - it may be a good match to my '72 VW 1300 which is also cobalt blue. I needed a good commuter with hub gears and was really pleased when this one came up.