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Thorn Mercury 650b owner review

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Well I've now been out five times on my new Mercury, and today covered about 60km on a series of Melbourne bike trails that included smooth flat pavement, very rough old pavement, maybe 20km of road-like gravel, and quite a few shortish but steep climbs.

I know some of you cover that distance before breakfast when you're touring or running Audax events, but I have never been in that class and as well have recently restarted riding after taking a break for a few years. So for me that was a significant ride and about the limit of what I could comfortably manage.

I carried a few bits and pieces in a single small pannier. Here's how she looked today.

I am delighted with the way the build has come up. Especially given I did not expect much in that department. More on that in a bit.

I am going to record some early impressions, not so much to inform forum stalwarts but to inform potential new customers or maybe used buyers.

I'll begin with the unboxing, because that's when it dawned on me that I'd be getting more than I'd bargained for. I'm in Australia, so the bike had to come a long way. It came incredibly well protected: every component smothered in foam plastic or packed in labelled and padded bags. There was a lot more to the rebuild than I had expected, and the supplied instructions assumed a much less comprehensive breakdown, but the bits were supplied in a way that let me work it all out, and with grease preapplied where appropriate.

The first surprise came as I began to remove the wrapping. From the images in Thorn's brochures, you'd imagine the paint was all anti-theft flat and dull. I'd seen other pictures in here, so knew better. But I wasn't prepared for the beauty of that grey in the flesh. And even these pics only get half of it.

Then as more emerged from the wrapping, the sculpted intricacy of the fork and chainstays. I could see nothing special about the fork from the brochure. Unwrapped it looked jewel like. And this is the cheaper ST version.

Undersold or what? Why does Thorn do this? I can only guess it is to ensure that people who order their first Thorn really want one.

Okay that's the unpacking, which will have to do for now. Built but without the chain on, and with the seat on the seatpost where Thorn had set it, she looked like this:

Next: Ride impressions.  ;)

To the ride impressions. It's going to be necessary here to distinguish elements that might be true of many options from elements specific to the Mercury 650b but I'll do my best.

For background, I cycled a lot in my teens, although not with a club or in organised events. At around the age of 16 I picked up a bargain bike used with nice lugs and possibly a butted reynolds frame, though it wasn't labelled. Came with tubulars and a single chainring, and I fitted a touring triple and 5-speed touring rear cluster. Lovely soft ride - in fact the fork was a bit wimpy torsionally. Managed a fun multi-day tour on it then swapped it for a new Peugeot PX10LE, with 531 tubing and again tubulars, to which I fitted the touring chainset and cluster. This was much stiffer and not nearly as comfortable, which surprised me at the time. That bike was stolen about the time I turned 20, and given I had got heavily into motorbikes it took me nearly 20 years to replace it.

The replacement was a Trek 7900 multi-track hybrid, with a steel unicrown low-rider fork, lugged and glued carbon-tube main triangle and quite heavy aluminium rear triangle that could handle panniers. The base weight was 11kg with seat and oedals, and as I picked it up heavily discounted I was prepared to accept a frame size way too small but with a top tube very long for its size. Came with Shimano XT MTB derailleurs. Used it over the next couple of decades as a mountain bike (there was enough clearance for 700x38c knobbies), commuter and multi-day tourer. The fit was never quite right but it did the job and rode quite nicely. Key limitation was torsional stiffness, which exhibited through the steering when loaded. Geometry I now recognise as randonneur - so I might have done better to bias loads to the front. Steering unladen was overly light and not terribly accurate.

For some reason after a driveline refurbish it started throwing its chain, and eventually a too hasty retrieval left a nasty gouge in the chainside stay. It's probably not weakened the stay a lot, since the aluminium seems quite thick at this point, but I wouldn't take it touring. Having decided it was time I got back into riding for fitness, I did a lot of research and purchased a Mercury - hence this review.

The first thing to say about the Mercury, a 61s with flat narrow bars, is that it fits me beautifully. Even though the seatpost as supplied by Thorn was adjusted way too high - I could barely get my toes on the pedals. Nevertheless I had asked for a fairly relaxed riding position, and with the seat readjusted that is what I have, with the 'bars set as supplied.

The fit alone seems almost wirth the price of entry. From the saddle, the bike feels very different from how it looks side-on. It looks like a big bike, but from the rider perspective it feels very compact, helped by the moderately steep (for a tourer) head tube angle and that fat 50mm Schwalbe G-One Speed tyre. I persistently experience it as a sport-tourer - just as Thorn claims it is. The long steerer tube with its spacers disappears as you're virwing it vertically, and overall I feel like I'm riding the cycling equivalent of a GT car - not light but small, sharp and comfortable.

I also enjoy looking down at the finely crafted lugged fork - so much nicer aesthetically than the unicrown fork that was fitted to the Trek and seems to have become the industry standard for steel.

Weight BTW on my luggage scale comes in at 13.8kg. That's with a Tubus Vega rack, full mudguards, dynohub, Edelux headlamp, Brooks Professional saddle, full-cage MTB pedals, and three bottle cages. Weight could be saved, at a price, from replacing the solid Thorn crank arms, the pedals, and the seat. I'm very comfortable with the weight, having expected that with the big frame and touring fork and the accessories and the 550g tyres it would have come in at mid-14kg. Then again, maybe my cheap scale is not all that accurate.

The ride quality is excellent, even if I thought I might have had a wee bit more compliance from the rear triangle. In that respect it feels roughly the same as the Trek, allowing for tyre differences. The fork is the Reynolds ST rim-brake verson with low-rider lugs, and with the big tyres comfort at the front is superb. You can feel the blades soaking up road hum in high speed descents - so on the question whether a steel fork actually does flex helpfully I'm a believer. The fork feels noticeably better than the steel Trek fork, and at the same time feels much more rigid torsionally. Forum regular PH has compared this fork with the alternative 853 fork on his Mercuries and says the ST fork is significantly less compliant. The 853 fork must be wonderful, but with the big tyre the ST fork is really, really good.

Andy Blance talks up Thorn handling, and from my experience so far he is well justified. It's great in a 'just right' sort of way - neither too twitchy nor too slow. On my regular ride there is a very steep brief climb up from a bridge underpass to road level, which includes an extremely tight left and right ess. I cleaned it once on the Trek but negotiating the left turn was so marginal that I walked it every susequent time. Helped enormously by the very low gearing I have for the Rohloff, the Mercury makes that turn feel safe and easy. It's the same in the way down: on the Trek I would unclip from the pedals in case I needed to dab; on the Mercury I've remained clipped in and felt safe. Likely the rigidity helps greatly here too.

Mid-speed handling in turns is helped greatly by those grippy, wide tyres, and the Merc carries momentum beautifully through twists and turns tyical of local cycling paths.

But it has been on the few occasions I've been able to enjoy winding high-speed descents that the Merc really shines. Here the rigidity, balance and accuracy of the rolling chassis has felt magnificent. I've done too few of these to say much more, except to observe that the exhilaration of a quick descent is enhanced very significantly by the confidence I have felt from the saddle. This was one of the less happy elements of handling on the Trek, so the difference feels very pronounced. It feels like on the Mercury I am going only half as fast on the downhills, except that I know I am not and quite likely I'm quicker.

The final touch on the handling comes from the tyres. The security added over the Schwalbe Kojac 700x35c slicks on the Trek is profound. Its particularly valuable on slick-looking surfaces but it's there all the time. You get used to accommodating the uncertain road grip of narrow rubber, but there's stress involved and I hadn't realised how much until I rode these big G-One balloons on winter trails.

Next: the Rohloff and other bits and pieces.  :D

I've recognised that the fit info isn't much use without my measurements, so I'm 181cm tall with a barefoot standover height of 88cm. I clear the top tube comfortably but from Thorn's sizing chart I have long legs for my height and I would want the next size down if my legs were a couple of cm shorter. That means that for a fairly relaxed posture, the long steerer tube with its stack of spacers is not avoidable. I imagine that's a piece of Andy B pragmatism: Thorn this way can accommodate more sporty postures with a single frame shape (or two, if you count the two top tube lengths), which helps hold the price level at merely challenging.

So to the transmission. Yes I am starting to hear a little more grumbling from the hub in the lower seven gears, obviously amplified by frame resonance. It concerns me not at all, and it's way lower in amplitude than, say, the gentle rubbing of the chain in bottom gear on a marginally maladjusted front derailleur cage. Nor do I get any sense from the sound that it's holding me up. The drivetrain continues to feel - note, feel - more efficient than the derailleurs I have used in the past. I find nothing about it demotivating; quite the opposite - I feel more motivated than I did on derailleurs.

The gearchange action is certainly different and I'm still getting used to it. It rewards mechanical sympatico and might punish the hamfisted. Get it right and it's as smooth and quick as a rear derailleur change on the smaller cogs. Get it wrong and you can find yourself in a gear you weren't looking for, or changing through two gears where you had sought to change one. The key seems to be the load you have on the transmission at the point of change, and if subtlety is required that's because the Rohloff will in fact shift under light load - so you can get away with being sloppy and don't immediately understand the benefits of being accurate. I'm still working on the accuracy, and it's clear there is a fair bit of joy still to come. Rohloff suggests timing shifts for when the cranks are vertical, and that will be a neat trick if I master it. The 7-8 change is merely more demanding of accuracy: this is where sloppiness with load and timing is punished most severely.

I've chosen 37-19 as the overall ratio and that is just about at Rohloff's permitted limit. Since I'm not very strong, the idea is to have a bottom gear that allows me to manage stiff climbs with a light camping load on. With the tyres I have that's about 15 inches, or roughly 22F-40R on a derailleur system. Any lower and I wouldn't be able to balance the bike, and yet with a moderate cadence I can balance her easily enough. As I get stronger I might go up 4 teeth at the front, which would add a little more than 10 per cent so I would still have a gear a little lower than my present second. An extra 10 per cent at the top would be welcome -  yes she does spin out early.

Nevertheless I have a (marginally) broader range than is offered on the newly fashionable 1x12 derailleur systems, with more steps in between. It is an advantage of the low sprocket ratio that the road speeds at cadence are closer than if the gearing were taller, and the steps feel comparable with what I had on my 11-30 rear 8-speed cassette. It is actually fantastic to have such a choice of low gears - I can tune the gear to the grade  very finely. It is also fantastic never to be anxious that the change into bottom gear might overshoot the biggest rear cog. This never happened to my derailleur systems in practice but I always felt some relief as the chain seated properly.

The other nice bit of course is never having to swap between front cogs, often with a compensating change at the rear to hold cadence. There is a lot less thinking and planning required, and I don't miss that a bit. The one downside of Rohloff's enforced sequential shifting is that sometimes the one-shift move to a big front cog is handy. That's rare though, and on a 1x12 you would not get that anyway.

I can see why strong riders and those who ride often in fast groups might prefer their close-spaced derailleurs, for sure. A Rohloff isn't for everyone; it just happens to match the sort of riding I like very well.

And I think that will do - I've put fewer than 150km on the bike after all. Questions and comments are welcome, of course. I may add stuff from time to time as I build up more miles.

Mike Ayling:
What a great review Moronic.

You mentioned the ability to drop two or three gears when encountering one of those sudden steep pitches on on a lot of Melbourne bike paths.

BTW is the picture of the bike along the Mullum Mullum Creek path close to where the creek joins the Yarra?


Hi Mike, I'm glad you liked it - especially given you have one.  ;D

Yes the snappy downchanges are handy. Of course you can go down gears pretty quickly on a derailleur transmission, and the 1x12 must have similar qualities. The big advantage over a triple is that you can change down as far as you like without also swapping front cogs.

The pic is on the Diamond Creek Trail, which by the end of the year will extend the Main Yarra Trail north to Hurstbridge. I'm yet to try the Mullum Mullum path - is it good?


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