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1
General Technical / Re: Drop Bars on a "Long" Frame?
« Last post by UKTony on Today at 08:24:49 AM »
My size 580L Mk 2 Mercury had a straight bar setup when new. The second owner converted it to drop bar which is how I bought it.  The original Thorn flat track bar and V brake levers were included in  the sale. I’d been accustomed to riding a straight bar Mk2 Nomad for the previous 9 years and wasn’t intending to buy a drop bar version but gave the drop bar setup on the Mercury a trial for a few hundred miles. I eventually decided to emulate the Nomad and convert the Mercury back to straight bar using the Thorn flat track bars and V brake levers included in the sale, mainly because,
1. Even with the 80mm stem (3cm shorter than the stem on the straight bar) I felt rather stretched in the riding position. I’m 5ft 11in but for my height I have an exceptionally long barefoot inside leg measurement (35in (89cm)) so a shorter than normal upper body.
2. Not relevant to the Sherpa but the Rohloff twist shifter on the drop bar conversion was placed on a short Thorn accessory  T-bar fitted to the fork steerer column below the handlebar stem. I feel safer having the Rohloff twist shifter closer to hand on straight bars within easy reach for rapid shifting without having to take my hand off the handlebars.

For information,
the 580L Mercury frame has a 600mm virtual top tube (I could be wrong but I think that’s measured as a horizontal line from centre of head tube/top tube junction to centre of seat tube). The 580S (short top tube) frame has a 575mm virtual top tube.
The drop bar conversion had an 80mm stem and my preferred  straight bar setup uses a 110mm stem.
In my case, if I wanted a drop bar Mercury I’d definitely choose the size 580S for a more comfortable riding position.
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Wanted / Re: Sport Tour frame
« Last post by sweats on November 04, 2026, 11:42:37 AM »
I’m still looking for a 561L Sport Tour frame or possible a complete bike if anyone has one they are considering selling.
Thanks in advance for any info.
Chris
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Non-Thorn Related / 'Court jester in the palace of science' on bicycle stability
« Last post by Andre Jute on November 04, 2026, 07:48:50 AM »
The Washington Post, in its obituary, quoted someone unnamed describing David E H Jones as the ’court jester in the palace of science’. That’s a witty description, but not fair, not exhaustive, not even comprehensive. David Jones did a lot of innovative thinking and writing for which other men took patents and even Nobel Prizes. An example is 3D printing, which Dr Jones laid out in New Scientist in 1974, 11 years before Chuck Hull ‘invented’ the process in 1984.

 He was also a prime practical prankster, the inventor of fake but plausible perpetual motion machines, one of which is in the Technisches Museum Wien (Vienna). On the other hand, I can offhand, without blinking again, name three prominent scientists that I have known who would have given their eye-teeth to have NASA carry their chemical garden into space, as they did for Dr Jones.

But, arguably, Dr Jones’ most important work for the future of the world, was proving that a bicycle with a reversed fork is stable.

That in the process Dr Jones incidentally killed the mistaken belief that some mysterious gyroscopic force was involved in bicycles staying upright, is a bonus but not all that important.

Bad thinking on that subject had already resurrected itself after Francis Whipple of Cambridge University in 1899 proved conclusively in the rigorous mathematics of his algorithm now known as the ‘Whipple Model’ that a riderless bicycle is stable.

And bad gyroscopic claims will resurrect themselves after Jones — probably about now, as fifty to sixty years seems about a Kondratieff Cycle for delusions of gyroscopes. Watch this space.

Here’s the bibliographic entry including a link for the article:
Jones, David E. H. (1970). "The stability of the bicycle" (PDF). Physics Today. 23 (4): 34–40.

The notation resolves to Physics Today, April 1970,  pages 34-40. If the link above doesn’t work for you, here’s the link full out:
https://www.phys.lsu.edu/faculty/gonzalez/Teaching/Phys7221/vol59no9p51_56.pdf

There’s also a YouTube video about Jones and bicycle stability:
https://youtu.be/J5ICTbqKoEI?si=n5cQhf_KXDav0e9n

Here’s Dr Jones' brief biography at Wikipedia, coming with the usual warning about Wikipedia being a lowest common denominator source:
https://en.wikipedia.org/wiki/David_E._H._Jones

Hat tip to Danneaux, the confidant of AI, for the knowledge, the link, and a giggle besides.
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General Technical / Re: Drop Bars on a "Long" Frame?
« Last post by mickeg on November 03, 2026, 12:01:24 PM »
Quote from: in4 on November 03, 2026, 08:17:17 AM
... Interestingly I was originally looking at a 565L Nomad Mk2 but ended up with a 595L instead.
...

Mine is a 590M.  Thorn did not offer any S size frames, only the L and M.  Since I knew I wanted drop bars, I tried to figure out which frame size would be best for me based on top tube length.  And the 590M looked about right for top tube length for drop bars. 

These photos show mine better with the drop bars.  Two photos, the first is the way I used it for my UK trip a few months ago.  I can't fit my full size fenders in the S&S case, I bought two pair of very cheap fenders from asia, and made my own brackets out of 1/8 inch X 3/4 inch aluminum bar.  Bracket in the front is screwed into the fork crown, rear is screwed into the seat stay bridge.  36T chainring and a bash guard.

Second photo is fitted the way I use it around town near home, 44T chainring, full coverage fenders.

And later I realized that this size had another advantage as this frame is a bit small for me.  But third photo shows that this frame is pretty big in an S&S case, not sure if a larger size would have worked as well for packing.

My Sherpa size is 610S.  I had the Sherpa for a few years before I ordered the Nomad Mk II frame.

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General Technical / Re: Drop Bars on a "Long" Frame?
« Last post by in4 on November 03, 2026, 08:17:17 AM »
Interesting photos there. Thanks for sharing. A crude measure I know, but looking at the guy's height I'm wondering if he has his saddle too high; with all the knock-on effects that can lead to re stem length, drops or straights? Guess we're all on that continuum at times. I use a shorter stem to the one I had fitted originally; just more comfortable. I've stayed with my expedition bars and ergon gp5s for the same reason. Interestingly I was originally looking at a 565L Nomad Mk2 but ended up with a 595L instead.

PS Hope the guy tensioned/changed his chain. Looks a bit slack to me! ((I've just replaced mine, along with a new 36T chain ring. I still dislike fitting a new chain though.)
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General Technical / Re: Drop Bars on a "Long" Frame?
« Last post by mickeg on November 02, 2026, 08:14:57 PM »
I read none of what Dan wrote.  While sitting in the train station in Inverness a few months ago, someone wheeled their bike up to me to say hi.  He said my Nomad Mk II was the first time he saw another one, other than the one he bought used.  And I can say the same, both of us had Mk II Nomads and his was the first time I have seen another Nomad Mk II besides my own.

We did not have much time to talk, I did not have time to ask about how he set up his bike.  But he did comment that he bought the bike used and that it was too big for him.

First photo, my bike on right, his on left.

Second photo, this was cropped from the first photo, I am pretty sure that he has a very short stem and that the stem is backwards, meaning it extends to the rear, not forward.

I recall seeing years ago in an ad that someone made some drop bar attachments that you could add to flat bars so that you could ride in the drops if you wanted to.  I think that would be a way to move the drops aft.

Some drop bars have much shorter reach than others.  You may find some with a shorter reach.  I wanted less reach on my rando bike and I did not want to shorten the stem, I put on a bar with shorter reach.

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General Technical / Re: Drop Bars on a "Long" Frame?
« Last post by Andre Jute on November 02, 2026, 07:02:58 PM »
I read only part of one of the articles Dan cites --
Quote
https://bicycles.stackexchange.com/questions/10236/is-reversing-the-stem-pointing-it-backwards-a-safe-way-to-reduce-reach-length
-- before starting to wonder about the teachers who hadn't taught the contributors to put their minds in gear.

There are only four facts that matter here.

1. A properly designed bike, fit for purpose, is a stable machine when in motion. As an example of the amazing dynamic stability of a bicycle with proper geometry, an English scientist*, bored out of his skull in an office job after the excitements of WW2, proved for all time in the parking lot that a bicycle with the handlebars, and consequently the steering and fork, reversed is dynamically stable when pushed and then allowed to run until it ran out of steam and fell over. (Not with my bike you don't, not even in the Service of Science!) I expect that a Thorn bike of any generation would be competently stable, but in any case we know for a fact from a chorus of experienced users that the Thorn bikes of the Andy Blance era were conservatively designed and thus extremely stable.

2. There is no mechanical difference in operation between a forward-pointing stem and a rearward-pointing stem except, for the dementedly obsessive, the theoretical fractional surplus of stiction between tyres and road in pushing rather than pulling, and, since one hand is always pushing and the other hand pulling when a cyclist turns his bike, these fractional forces balance each other. All that matters is how long the lever arm is: the lever arm is the direct distance between the cyclist's hand on the grip and the pivot in the centre of the steering tube; Dan has already pointed this out. The 'twitchy bike' in the discussion group that irritated me is mere confirmation bias, if a real fear, or if not, wannabe experts posturing.

3. There was a time in the early history of the bicycle when tiller type steering was common, then less common because wheelbases were short and knee-room had to be found somehow. Tiller type steering of various degrees of sophistication still has a foothold in recliner bikes, where they are a vast improvement over the only alternative, rear wheel steering. If you want to feel real instability, try rear wheel steering in a tadpole recliner tricycle; every move is a sudden-death playoff, a lose-lose event. (In automobile suspensions the concepts of leading and trailing positional or reacting lever arms has validity but only because so much more power is in play, and, as can be seen in any Citroen or modern hatchback rear suspension, the engineers never agreed on which way is the best compromise.)

4. When I made my truck assisted personal record ton-up downhill bicycle ride, I used an adjustable stem bent so far down that I put a piece of thin foam between it and the head tube to protect the paint; in the stem the North Road bars were rotated so that the grips pointed nearly vertically downwards beside the fork legs to get my back flat. In short, there was virtually no 'stem length' and any input should in theory have resulted in a noticeably more abrupt steering response than the normal settings. I can assure you that at a 100kph and some small change I didn't fancy chewing tarmac, and was paying strict attention to the bike's responses. This is an anecdote with a sample of one, so I'm not claiming the status of science or history here, but in racing my specialty was suspensions and I was my own test driver, so I know what to look for.

I therefore think Binky can save his money and to start with merely turn the stem 180 degrees to point backwards. He might, depending on his and the bike's precise measurements, after his initial tests have to buy a shorter stem, or possibly (but not really likely because knee room will be critical), a longer stem. And it would be smart at first to ride cautiously but that's pure common sense.

One more point. I like wider grips-spacing than is fashionable among the drop bar crowd. Binky might consider North Road bars. They're extremely ergonomic used right way up, they can be flipped over front to back to become bullhorns, and they can be flipped to become mustache bars, all of which means he can fine-tune his fit on the bike, his reach, and his back angle almost infinitesimally, and even more so when partnering the North Road bars with an adjustable stem. North Road bars are cheap, or sometimes free from the sort of LBS which makes its main profit from selling 'upgrades' to the unsuitable bikes they have persuaded people buying bikes on government schemes would give them a 'sporting look'; one of the first things they throw off are 'old fashioned' North Road bars.

*AI is outrageously useless. I asked Siri on my Mac with the best Apple AI, 'What is the name of the Englishman who proved that a bicycle with the handlebars and all attached to them turned around is nonetheless stable if pushed to speed and then allowed to run without a cyclist aboard?' It replied, 'An Englishman is a man from England. It can also refer to several specific people, such as the Canadian rock singer Jason Englishman or the reggae musician Erald Briscoe, who records under that name.' Hey, Apple, did you intend to insult me with pop trivia? Shame on you.
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General Technical / Re: Drop Bars on a "Long" Frame?
« Last post by Danneaux on November 02, 2026, 01:42:47 PM »
Hi Binky!

Warning: Long post ahead.

If you change from Comfort to drop handlebars, you will likely have to change your shifters as well to accommodate the difference in handlebar grip diameter, so keep that in mind.

I'm going to reach back a ways in the archives for my past posts on a related topic. I'd urge you to read these first...
https://thorncyclesforum.co.uk/index.php?topic=4939.msg28811#msg28811
...and...
https://thorncyclesforum.co.uk/index.php?topic=10737.msg77527#msg77527

[Some of the related links mentioned within those links no longer connect, because we changed domains since they were posted. I'm engaged in the slow and tedious process of going back through ALL the Forum posts of that era and updating them. Until I get them all updated, the old links will work if you replace...
https://thorncycles.co.uk/forums/
...with...
https://thorncyclesforum.co.uk/
Do a copy-paste of the updated portion and you can view them easily as they're still there. Same with photo attachments that have no thumbnails. Click on them, then download to view locally on your device]

The summary version:
While a frame with a "long" top tube is not ideal if you need shorter *and* drop handlebars, you can certainly make it "better". It just depends on how much distance you need to make up. My Nomad Mk2 was definitely not recommended for use with drop handlebars, but by choosing a Medium (rather than Long top tube version) frame size, then fitting compact drop handlebars and a stem with shorter forward extension/reach, I was able to duplicate the positioning on my other bikes with "standard" length top tubes that had longer-reach stems. YMMV may vary; "how long is a piece of string?". Some measurement and careful parts selection will be required.

As the two links above indicate, the important distance for steering leverage is not handlebar placement, but the lever arm (distance) between your hand grips (whether drop or straight or comfort 'bars) and the steering axis. Get that the same or similar, and perceived steering effort will be very much the same. So long as your hands remain at a similar distance from the steering axis -- whether forward or back or widthwise -- the steering will feel similar, rather than more twitchy. Counterintuitive, but it is a matter of leverage rather than placement. This is why my 1 liter bidons placed immediately around the steering axis have no noticeable effect on steering.

The one negative difference I have felt related to stem length came from fitting very long-reach stems on frames with short top tubes. I needed to fit narrower bars to compensate and keep the same moment arm to avoid the feeling of a "tiller". Also, with more body weight forward over the front wheel, handling suffered. This doesn't seem to be the case when weight is moved more within the wheelbase of the bicycle, rearward of the front axle centerline.

As a hobbyist framebuilder, I have made a variety of stems for the folding small-wheeled bicycles I brazed-up from raw tubes. Because the main frame spar was so much lower than the handlebars, I had freedom to empirically test the effect of long, short, and negative stem reach and this is what I concluded. Allowing for a head tube declined rearward, the stem I designed and chose for my suspension design is effectively zero-extension (Photo 1 below) and I'm happy with the handling. I can and have reversed it with no ill effect on the ride. I pair it with a bullhorn pursuit handlebar (and bar-end shifters) that can be reversed along with the stem to achieve a very upright cockpit if desired.

Wrt drop handlebars, brake lever bodies (where the hands perch when riding atop the hoods) have also become much longer over time, mostly to accommodate the internal mechanisms of brifters (brake levers-shifters combined). This was copied in standalone brake levers by Tektro and other brands so cockpit sizing would be the same with, say, bar-end shifters fitted. If you commonly ride atop the brake levers with drops and have either bar-end shifters or downtube shifters fitted, a swap to smaller brake lever bodies will also effectively shorten the cockpit. 1980s vintage Dia-Compe, Shimano, and Campagnolo brake levers of that era and earlier were all much shorter reach and work fine with cantilevers or calipers but not standard v-brakes. If you must have v-brake compatibility, then fitting a leverage-altering pulley like the Travel Agent or mini-Vs can create a cable-pull match with the older, shorter levers.

Photo 2 below shows my position on my 580M Nomad Mk2 with Medium top tube. I like the overall feel very much.

The calculations for all this are pretty straightforward and "subtractive": Simply measure where your hands are now, then progressively remove the distance to match where you want your hands to sit atop drop-bars and the brake hoods.

A helpful review of *extremely* short and zero-reach stems can be found here, along with a discussion about them...
https://theradavist.com/zero-offset-and-reduced-offset-mountain-bike-stems

More here...
https://www.bing.com/search?q=bicycle+with+reversed+stem&cvid=270a18bdb6644449a78b88aebb55939f&gs_lcrp=EgRlZGdlKgYIABBFGDkyBggAEEUYOTIGCAEQABhAMgYIAhAAGEAyBggDEAAYQDIGCAQQABhAMgYIBRAAGEAyBggGEAAYQDIGCAcQABhAMgYICBAAGEAyBggJEAAYQNIBCDY4NjBqMGo5qAIIsAIB&FORM=ANAB01&pcmpc=PCMEDGEDP&ucpdpc=UCPD&PC=UCPDDB

https://bicycles.stackexchange.com/questions/10236/is-reversing-the-stem-pointing-it-backwards-a-safe-way-to-reduce-reach-length

https://theradavist.com/raised-reversed-mountain-bike-stem-review

Do be warned, however: If you do fit drop handlebars to a reversed stem, the arc of travel will be around the rear of the pivot point/steerer. This means (and especially so with drop handlebars that...drop), the sides of the 'bars will be below the level of the top tube and so limit the available travel 'round the arc. This should not be a problem, as most steering is done by a combination of leaning and small corrections in arc. You'd be most at risk of 'bar-tube collision during tight turns at low speed.

One last thought: If you prefer the palm-facing orientation of riding atop drop handlebars, one way to achieve that on a too-long frame is to fit bullhorn pursuit handlebars (Photo 3) reversed and flipped with your present stem. Your hands will be oriented similarly with palms facing, but much closer to you. To get a bit more aerodynamic for headwinds and such, you can always slide forward to the cross-portion of the handlebar. You'd need to replace your present brake levers with "interrupter" levers intended as supplements for cyclocross and gravel bikes, due to the difference in grip diameter between road (23.8mm) and MTB (22.2mm) 'bars. That's how I handle braking on my Folders. The interrupter levers are available in cable-pull ratios suitable for road/canti- or v-brakes. Might have to change your shifters, too.

Whew! Good luck!

Best, Dan.

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Non-Thorn Related / Re: Bike accessible bothies in Scotland
« Last post by Binky on November 02, 2026, 01:25:11 PM »
A bit of a thread resurrection.

Good to see there's a bothy thread on here, I'm a big fan of them, have used many and have attended a few maintenance days (work parties) over the years, where any help is appreciated regardless of what DIY skills one has or doesn't have!

Fair play to you on getting loaded touring bikes to some of those bothies. Some landowners' idea of a "landrover track" can be pretty steep and rough and I've walked in to some of the bothies mentioned thinking I'd struggle on a mountain bike!

As has already been mentioned, the MBA website is a good source of information on where the bothies are and how to use them responsibly. Membership is worthwhile as the yearly membership fee helps go towards maintenance of these facilities.

The UK bothies forum at https://www.tapatalk.com/groups/ukbothies/ is worth a look too. Some parts of the forum require logging in to read (creating an account is free) but the threads for each bothy, organised in subsections by region can be accessed without logging in. Plenty of stories and photos over the years.

I'm gradually trying to spend the night in every MBA bothy so if anyone wants some (unfit) company for bothy trips let me know!
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General Technical / Drop Bars on a "Long" Frame?
« Last post by Binky on November 02, 2026, 11:18:54 AM »
I've done a couple of rides on my recently purchased secondhand Sherpa and although I've yet to get a bike fit for it (something I'm organising) I'm in two minds about the Thorn Comfort bars it currently has. The majority of miles I've cycled over the decades had been on steel road bikes with drop bars.

I know Thorn designed the "long" frames for straight bars and the "short" ones for drops but has anyone successfully put drops on a long frame? My concern is I don't have a particularly long reach so a very short stem would be necessary.

I understand bike fit is a very personal thing but I'd be interested to hear if anyone has done this or has any thoughts/advice on whether this is a good/bad idea.
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