Anybody got a 650b Mercury?

[brummie]

As per the title - Anyone riding a 650b Mercury? Don't think I've seen one on this forum as yet...

[JohnR]

I've been lurking here for over a year (initially to improve my understanding of the Rohloff hub gears) and this question has encouraged me to finally register for the forum.

In July I had an irrepressible urge to spend the money saved during the lockdown and bought the red 650b Mercury that's shown on page 2 of the Touring Bike Bible http://www.sjscycles.com/thornpdf/thorn_mega_brochure.pdf . I wanted a bike that was more comfortable through the potholes and patches that seem to form an ever-increasing proportion of the English rural roads than the aluminium framed bike with Rohloff gears that I bought a year ago which couldn't handle more than 37mm wide tyres and the 650b Mercury appeared to be as good as I could get. I also wanted disc brakes front and back. After getting a Dawes Super Galaxy with those brakes a couple of years ago I wouldn't want any other brakes. That bike, however, got rehomed as I didn't find drop handlebars very comfortable and got fed up with the mental arithmetic involved in any gear change.

After unboxing the bike I fitted my Spa Cycles Nidd saddle and went for what I expected to be a short test ride with the possibility og going further. I ended up doing 43 miles which provided plenty of time to decide what was OK and what needed changing. The gearing was too low. Sarah had assured me that it was a 17T sprocket but I counted 19 teeth. That soon got sorted and I was pleased to note that there was enough travel in the EBB to take up the slack in the chain. I wasn't happy with the handlebars. First I shortened the Thorn bars but soon concluded that the bar ends weren't to my liking so the whole lot was replaced by some Ergotec AHS bars which I already had. Apart from those bars providing the hand positions I find comfortable, I suspect that the slight flexibility (at least when the hands are on the front part of the bars) provides a bit of bump absorption.

I then decided that the Nidd felt a bit wide (the Mercury has a longer frame than my previous Rohloff bike) and am currently trying to break in A GB Aravis saddle (I think I'm finally winning). The other challenge was finding a rack suitable for my rack bags. After trying several racks from my other bikes I ended up with an ETC rack which is a fairly snug fit above the mudguard (to maximise space for the bag under the back of the saddle) and also has enough width to support the bag. A CarraDura bag is currently on the bike but I've also got a Carradice Super C.

The bike is now up to nearly 1400 miles. The rear tyre is getting smooth in the middle and has various small cuts. Getting my first puncture was a little disconcerting - finding the tyre was a bit soft and hearing a bit of gurgling. The front tyre is in better condition. One thing I'm not happy with now that the roads are turning muddier is that there's precious little clearance between tyres and mudguards. Maybe that's done to confine splashing water but doesn't work with sticky mud. I've had to use the pressure washer to get the muck out of the insides of the mudguards.

I've got a pair of Panaracer Gravel King SKs waiting to be fitted for the winter cycling (I like a bit more grip given the amount of fine gravel that gets on the roads). They are nominally 48mm so maybe will provide a little more clearance inside the mudguards. Also waiting for fitting is a Hebie Chainglider.

Any questions?

[PH]

Great first post JohnR.
Some interesting choices and a well thought through evolution.  A few sizes smaller than my 610L by the look of it, probably why it looks so well proportioned on 650B. 
Re mudguards - is there anymore clearance on the frame?  I have 700 x 40 on the back without them being particularly tight.

[JohnR]

There is more clearance on the frame - see the photos at http://www.sjscycles.com/thornpdf/BUILD8MERCURY650bROHLOFF.pdf which says that there's room for 650b x 54mm with mudguards. However, to move the mudguards out I'll have to get some new stays because whoever assembled the bike didn't leave any length protruding beyond the mounts on the mudguards. I'm in correspondence with Highways England regarding the mudbath their contractor has created on a minor road although, if it's like last winter, people seem to think the best time to work on or near a road is when they can make maximum mess.

The other minor adjustment was to replace the 110mm ahead stem with 90mm. I'm at the fractional adjustment stage but one beneficial change compared to my previous bike (still in garage) is that the bottom bracket is slightly lower so I can have what feels to be the optimum saddle - crank distance while easily getting toes onto ground when stopped.

I had planned to do a leisure supported LEJOG this year using the previous bike, which is up to the task but not ideal, and when that got cancelled I looked around for a better bike to get ready for next year.

[JohnR]

I note that I didn't pass comment on whether the bike had delivered the expected improvement in ride comfort. The answer is, without any doubt, yes. There's a bit of bounce through the rough where was previously there was a series of thuds.

I've also got another comment on the Mercury: I've discovered that the saddle has gradually lowered itself by about 20mm although the bolt is as tight as I can get it. The seatpost had been very generously greased although it's held in the seat tube using a shim so the risk of the seatpost rusting in place is somewhat remote. I've cleaned off as much grease off the tube and the inside of the shim as I can easily do without resorting to cleaner and wait to see if that provides enough friction to keep everything in place. If not, I'll be getting the calipers out to check diameters of seatpost, seat tube and shim.

[Danneaux]

Lovely Bike, John; thanks for sharing it with us.

I've discovered that the saddle has gradually lowered itself by about 20mm although the bolt is as tight as I can get it.

Slipping seatposts can be a complicated issue due to variations in tolerances between all the parts, see:
https://surlybikes.com/info_hole/spew/spew_why_seatposts_slip
The one on my 2012 Nomad Mk2 initially slipped. Careful checking of all dimensions showed the ID of the seat tube was within specs, the OD of the seatpost was within specs, but the shim was slightly undersized. It was the cheapest thing to replace, so I fitted a new one and had no more problems. The replacement required a normal amount of torque to keep the seatpost firmly in place even with a film of grease -- as expected.

Best,

Dan.

[brummie]

Thanks for sharing John. I've always thought the 650b option on the Mercury was a nod in the right direction Thorn took many years ago with their highly popular XTC range.

[PH]

I've discovered that the saddle has gradually lowered itself by about 20mm although the bolt is as tight as I can get it.

That's a shame, I'd have thought the plastic shim would have enough deformation to grip even if there was some slight mismatch.   
Both of mine have been fine, with plenty of marine grease, not to avoid seizure , but to keep the rain out.
On another bike, I have a slipping post, a couple of wraps of PTFE tape is the difference between bad fit and perfect.