Thorn Cycles Forum
Community => Non-Thorn Related => Topic started by: Danneaux on June 28, 2012, 11:06:35 PM
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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.
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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
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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?
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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...)
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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.
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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
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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
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Dan, are you trying to turn an art into science?
Eh...what gave me away? ;)
All the best,
Dan.
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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.
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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.
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.
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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
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Wonderful, Jawine; I'm still laughing!
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. 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). 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. 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.
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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 ;)
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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!
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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. I doubt I will ever reach Jawine's speed!
I doubt many of us will; she is remarkable in our group!
Best,
Dan.
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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.
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the cobalt blue with an Alfine which has been on the website recently
Oh! Now, this is exciting, Robert! I don't believe we've had any RST/Alfine owner-rider reports on the Forum yet, let alone photos. Especially nice if it helped trigger a Forum membership; very much looking forward to seeing it personalized under your ownership and to hear how it works for you. '72 VW 1300 which is also cobalt blue
A match made in heaven, I'd say! What will you call it? Name it, and it'll be faithful to you always...
Best,
Dan. (...who really should think of better names than "The Nomad", "The Blue Bike", "The Maroon Bike", "The Tandem", etc -- all seem to belong to "The" same unimaginative family)
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I am not normaly very aware of my instantanous speed on the bike but pay more attention to the avarage over the ride. However on night riding (Like last night) I need to pay much more attention to speed as with my lights (2 off Cateye 530) I have about 20m off well lit road so have to keep my speed down to a point where I can avoid any unforseen obstacles (potholes, cats, dogs boars deer and even the occasional bear) At night I limit the speed down to 40km/h as I feel that is safe.
In the voting I have gone for above 30mph as I would say anything upto that should be classed as normal riding speed. Not to say I ride that fast but I aim for about 20mph cruising speed on the flat on an expedition touring bike (unloaded) and in my old roady days it used to be 25mph solo cruising speed. At these sort of speeds a bike should handle in its "normal" manner and no "high speed" craveats should be put on it.
Over 30mph you are one or more of the following:
Really giving it some
Going down hill
In a very good race line
High speed tail wind
In these circumstances extra caution is required and you would accept the burden of paying more attention to both the road and the bikes behaviour.
Thats my two pennies worth
Andy
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Depends on the road too...I have no speedometer but I know I get nervous around 30mph downhill from a ride where I did have one. Braking distance increases and so does ouchie if anything goes wrong.
But, there's few roads here where you can safely let rip.
There's nearly always White Van Man, sideroads, left turn into idiots, Vintage Potholes (tm) and other hazards. Especially potholes...everywhere!
So it's bikehandling + environment that determines speed for me :)
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I was once radar-trapped and booked for breaking the speed limit in front of the hospital at Clon, which is at the bottom of a hill. I went through the speed trap at 43mph/69kph, still slowing after seeing the hospital sign and remembering that it is a notorious speed trap location. This conversation ensued when the policeman stepped out from behind the bush and held out his hand to stop me.
"Good! I like to see my tax-euros at work, Constable. If you didn't get the number of the second bastard who passed me too close, I have—"
"It's you I'm booking, sir. On two separate charges. Exceeding the speed limit, doing it in front of a hospital."
"But those bastards passed me."
"They're local, sir."
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Well, Dan, there are old riders and there are bold riders, but not so many old, bold riders...
"It depends", surely -- on three clusters of variables: bike, rider and load, and terrain (the latter understood broadly to include not only road, surface, slopes and corners, but also wind, rain, june bugs, other traffic, pedestrians, etc.) (Much like the old dilemma of judging musical quality: singer-song-or-audience?) (Too many sidebars-itching-to-become-tangents here; sorry about that.)
So, for me, "fast riding" = "approaching the limits". But the notion of "limits" surely includes the bike's capabilities + terrain + how-much-do-I-want-to-terrify-myself-today, etc., etc. So I'm reluctant to put a (kph/mph) number on it. Out-riding your brakes or headlight is surely "too fast". 60 kph down a 14% grade is "plenty fast" -- but stupidly fast if there are unseen sharp turns (esp at the bottom), unyielding walls or barriers, sand-gravel-wet leaves, and roadside forest where lurk the twitchy deer; or, if you're in Africa, where always there lurks a clutch of goats in the high grass, goats which cross the road only in single file & only at the last possible instant, and which always include a youngster who didn't get the memo, looked up, saw Mum mid-way across the road, and panicking, dashed into the empty spot you'd just chosen so as to avoid ploughing into the line. So, "fast riding" = "approaching the limits" = "consciously diminishing one's margin of error".
I guess one could find out about shimmy, etc., if / if one could control the variables of "terrain" enough to be able to assess shimmy at speed, under load, etc. -- without finding out all-of-a-sudden that (dang!!) I've just crossed the limits of my bike or myself--funny they were there & not a bit higher as I'd assumed/hoped...
J.
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last year i was out riding with the group in the cooley mountains well me and another guy got dropped on a long' ish climb.but when we were coming down the other side we let it rip 55mph, caught the group in jig time flew by them. we couldnt understand what they were shouting at us until we rounded a bend and ran out of road man it was scarey but lucky we managed to stay upright. i done over 60mph in spain coming off a mountain ah i've copped myself on since those days 16mph is fast enough these days. ;)
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Well, Dan, there are old riders and there are bold riders, but not so many old, bold riders...
LOL ;D
Hobbes that's typical isn't it! ;)
I personally HATE any near misses, so I don't push my limits hard when I feel there's any terrain risk, rain, mud etc. I just don't get a buzz from a near miss, more a panic feeling ;(
Going uphill on the other hand...there's a lovely 1 mile climb to get to a friend's house. The trick for me is to get the XTC (unladen) uphill on 52/16 and time the effort/RPM just so that I mash it up just to the house. Which doesn't always work...last Sunday it turned out that I am out of practice ;)
As there's no risk due to any em speed and the road is quiet enough and wide to take the middle of the lane (potholes and damaged rollsplit) I test fitness limits rather than speed/handling limits. Can't get floored on an uphill just stop if it's too much.
Yes it's very fast downhill but not for me lol if you want you can hit 40mph ;D
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Ah, jeez, Jags, J-M-&-J, please be careful, think o' your nearest and dearest and your wee grandkids....
J.