From time to time I do an incognito search for Thorn Mercury reviews, in part to see how the model's reputation is faring and in part to see where Google's algorithm is ranking my lengthy owner-appraisal on here of the Mk3 650B.

It was nice to see my piece ranked at 2, but not so nice to see the highlight Google had chosen, which emphasised: Steering unladen was overly light and not terribly accurate.

Someone curious about the Merc may well have responded to seeing that tidbit by reading the referenced post, and might have discovered that the remark quoted described not the Mercury but the bike it replaced: my late-90s Trek 7900, a carbon-aluminium 700C hybrid.

But I've seen recent instances of people seeking advice on enthusiast forums and observing that AI says this or that about the product in question. And on its face, that seems fair enough: you wouldn't think the much-hyped technology, new as it is, would be so incompetent as to weight heavily in its response a remark someone had made online about a different product altogether.

Well, you would if you've been following the rollout of AI-powered bots and have a sense of their limitations.

As the screenshotted pic shows, the next item on the page is an AI summary that says in part:

"The Thorn Mercury (specifically the modern Mercury 40) is a premium, highly versatile steel sports tourer. Riders praise its classic, responsive 853 steel frame, ..."

When as we know, the Mercury 40 doesn't have an 853 frame – and as far as I can tell has received no praise online from any rider whatsoever.

We can all hope that AI gets better. Even if some clever people have proposed that it will mainly get worse, because it will be feeding increasingly on its own misinformation.

I have for sale a the above frameset bought a few years ago off what I believe was the original owner and built up but not used for much other than some trail riding around the local woods.
It is a hub gear specific frame and I have had Sturmey Archer 3 speed, Shimano Alfine 11 speed and a Rohloff 14 speed in it at different times. It is disc and V brake compatible and has an almost new bottom bracket which has done less than 100 miles, a Hope headset but the bearings are not as smooth as they should be, the original seat post and two side loading bottle cages.
The seat post tube is 400mm, top tube 560mm and the stem is 260mm, there is a some of corrosion on the forks and bottom bracket which should be visible in the photos. The forks are Magura and hold pressure.
For some reason the previous owner filed out the front wheel slots which I have shown but this did not affect the mounting of any of the wheels I had in it, make your own mind up whether this is acceptable to you before buying, Thorn do sell a rigid fork for this bike. I have washed it but there may be some dirt left in out of the way places.
I would prefer pick up from just outside Axminster in Devon and will post within the UK but I would need to get a box which might take a few days as I do not own a car, I would use Parcelforce and expect it to cost under £20 but will get an accurate price if someone wants it sent. The frame number looks to be 582SM07016 but the powder coating is quite thick so this might not be totally correct.

Price is £140.

For photos here is a link to the listing on Retrobike.

https://www.retrobike.co.uk/threads/thorn-stirling-frameset-small-medium.508223/

I recently acquired a Thorn Raven Enduro MTB frame, size 589L.

I am now looking for a suitable rigid fork for an all-year city commuter build.

Any good suggestions? Carbon or steel?

Also, would it be possible to fit 27.5" wheels on the frame?

Best wishes and happy trails
Mikkel from Denmark

Quote from: in4 on June 08, 2026, 10:09:16 AM

Perhaps it’s simply a case of business realities.

Probably

Oh, I think we can take that as a 99% certainty. Here are just a few costs associated with such an efflorescence of models and fits as offered by Thorne while Andy Blance was their designer, all of which I knew about before I went to business school:

Cost of capital (interest, repayments of loans cutting into distributable profits) to finance so large a range, warehousing space built or rented, sales lost because a large range of sizes and fits and models must be compensated by reduced colour range which is arguably more important to the vast majority of bicycle purchasers, time to train customer-facing staff in so large and varied a range, multiplication of showroom fit-out of so many models meaning larger stocks of expensive parts. The absolutely brilliant 100 days free trial also brought costs to the vendor, as well as welcome buzz on the internet. We also saw some of the fits at the margins being offered well after the main body of the production was sold, often at bargain prices; these discounts are an additional cost of so large a range.

On the other hand, you might say that the two main ranges established Thorn with a bang as a premier manufacturer of touring bikes after making custom bikes ran into a brick wall of costs and Far Eastern competition, and very likely brazier staffing problems too. (A quarter century ago already, when I drew a design for a custom bike built of triangulated small tubes, I couldn't find anyone except art school welders and silversmiths-- Jesus help me! -- to braze it together for me.) Thorn wouldn't be THORN today without all that; it might not be more than a fringe curiosity, as so many of the once famous custom builders in Great Britain have become. Whichever way you choose to do it, it is expensive to establish a mainstream brand, and niche brands perversely cost more to establish.

There is a time to take such a risk, and pay its costs, and inevitably a time arrives for consolidation and rationalization.

***
It's worth saying that this is a standard business school (or at least good, meaning non-political, business school) applied micro-economics analysis: in short, a point well understood would arrive where the owner of the business would have to make some unavoidable hard choices. 

Personally, I came to appreciate Thorn's exquisite care for the fit of their riders after Sheldon Brown drew my attention to it, and to Mr Blance's insistence on the best value, long-lasting component choices which would least often immobilize the tourist in some godawful place.* Getting on for twenty years later I see no reason to change my mind about either early impression.

*In Oz you get a choice between 'The Pub With No Beer' and 'The Fatal Wedding', the latter 114 stanzas that start, 'The Hearse Overturned At The Crossroads.' You shoulda stayed in Melbourne: at least there you can get a 'Floater' from the cart at the bottom of Spring Street, which is a meat pie in a bowl allegedly of pea soup, and the only danger is the tram lines bending your rims as it they cast you onto the tarmac.

Perhaps it’s simply a case of business realities.

Probably

Going from imron back to powercoat doesn't seem like such a step down in an era, when frame-protection tape is so common in the bicycle world. Primarily favored by bikepackers to avoid bag-rub, but it’s not as if there are any downsides to using it even if one doesn’t have such bags.

My Nomad Mk2 frame is powercoated and even unprotected by tape, and used now as a local-use bike in a wet climate. I can't say the paint seems particularly more vulnerable than my imron Nomad Mk3 frame.

Frame tape is fine in the obvious areas but it won't wrap around bottle bosses, cable guides, and rack mounts, which in my experience with my Thorn bikes are areas which start to rust and from where it creeps under the paint and can start to bubble.
Maybe the Thorn paintwork has improved since I bought mine. But I liked the idea of the more durable Imron paint and stainless steel fittings.