Looking for a lighter Rohloff bike than my Mercury

[Moronic]

My preferred handlebars (Ergotec AHS) add a bit of weight compared to straight bars with bar ends but I find them to be much more comfortable so they will have to stay. Similarly the Chainglider adds a bit of weight but is too useful.

I think a few forum members have commented in another thread - maybe another of yours, John - on how it's the non-negotiables that keep bringing the weight up.

FWIW, I'm just back from a trundle of 50km or so and have weighed the bike pretty much as ridden but no food or water bottle, and it came in around 16kg. Plus by then I'd removed my beanie, cable lock, phone, and specs with case - which likely add more than 500g.

On the frame weights PH, what interested me about the comparison of tube wall thicknesses was that the Mercury used the same thickness as the bike Dan had set up as his featherweight, which was within a pound of the carbon-framed Marin I cited.

On the specialness of Reynolds 853, I'm sure the same spec is available from other makers but all this heated-treated stuff is special in so far as the yield strength, and hence the potential for springiness, is way higher than for the softer steels that haven't had the treatment. I think Andy B said somewhere in the megabrochure that the heat-treating more than doubled the price of the tubing. Andre will probably tell us that you can double the price  of a product without improving performance and then sell it to suckers if you get the hype right. I find it hard to imagine Andy falling for that one over a decade or more though: much more likely he'd be explaining to us why heat treatment was a waste of time and money. Unless it actually worked.

[PH]

On the specialness of Reynolds 853, I'm sure the same spec is available from other makers but all this heated-treated stuff is special in so far as the yield strength, and hence the potential for springiness, is way higher than for the softer steels that haven't had the treatment.

All steel has pretty much the same springiness (Youngs Modulus), there is some minor variations but I think Reynolds quote the same figure for all their tubes. The feel comes entirely from the shape and dimensions, one steel tube of the same diameter and gauge will feel exactly like another.  Of course you can't make the same tubes in any steel, the different strength, both Tensile and Yield, determine what can be done with it.
Heat treating does indeed add a chunk to the cost of a steel, Reynolds offer tubes with and without, 853 is heat treated 631, and I think 725 is heat treated 5??.  Thorn's own branded 858 tubing is also heat treated.
OK I'm not a materials scientist, so if anyone knows better I'll correct this, but as far as I'm aware - Thorn 858 tubing will look, feel and behave identical to Reynolds 853 of the same diameter.  Any strength differences will only be apparent at the extremes, such as dent resistance or impact (Crash damage)
So why is the Mercury made with Reynolds?  Well, we can only guess and mine is - There's a lot of work gone into the Mercury frame, every tube is specific and shaped, it's hard to find a straight edge! Possibly their supplier of Thorn tubing couldn't offer that.  But it was always going to be an expensive frame and I suspect the "upgrade" to the Reynolds badge was a smaller percentage of the overall cost than it would have been on a lesser frame. 

[PH]

To help understanding of my current situation I attach a photo I took of my Mercury during the recent trip. It would have weighted a bit over 20kg which is around 2kg less than on the LEJOG due to (i) Marathon Almotion tyres with tubes replaced by tubeless G-One Speed and (ii) rack and rack bag replaced by saddlebag with Bagman.

Your bike doesn't look particularly extreme to me.  You seem well aware of where the extra weight comes from and have decided it's worth it.  It is incremental of course, keep saying X is only a couple of grams and it soon becomes xxx. 
Just be careful in the comparison game that it's like with like. I weigh my bikes bare, everything that detaches is before it goes near the scales, bags, tools, bottles, GPS.  I don't ride anywhere without at least some of them, but still don't consider them "Bike weight"
So, what do your extras weigh and what difference would not having them make?  It seems to me that wouldn't be a hard question for you to answer without spending thousands! The only thing you can't test for yourself is the fork difference, but a steel disc fork is always going to be a disadvantage it terms of weight and comfort (The later can easily be compensated by tyre size, but only by adding to the former)
 

I could then join PH in being a dual Mercury owner.

It is an exclusive club, I don't know the entry requirements, my application was via the stupidity of riding into the back of a car and I don't recommend that.
If I'd started with a blank sheet, I'd have a 700c Mercury and a 650B Nomad.  Those two would ideally cover the riding I currently do on four.

[JohnR]

It's the wrong time of year for sitting in my chilly garage and trying to weigh each bit on the bike but I agree that all the extra, but useful, bits progressively add weight. It's evident that while 50mm tyres improve comfort they, plus the appropriate mudguards and rims, add weight compared with something narrower (and, I presume, slightly increase the aerodynamic drag). However, while there's a good range of 650b tyres in 50mm or larger, there's limited choice in smaller widths. Schwalbe, for example, seems to jump from 50mm to 30mm or narrower.

Which gets me thinking about having a set of 700c wheels for the Mercury. On paper, I have these sitting on my potential donor bike although there are two potential obstacles: (a) that bike has a belt drive with a screw-on sprocket at the back, which I would need to wrestle off; and (b) the front wheel is QR whereas my Mercury has a 15 x 110mm boost hub. Also, when changing wheels I would need to also change or remove the mudguards which isn't difficult but is a little tedious and regularly swapping between two configurations could get a little boring. I've read a little about carbon seatposts and comments confirm that they help in filtering out vibrations caused by less good road surfaces. Comments about Wiggle's cheapest vary but it seems to be a good starting place.

A second frame with a lighter configuration therefore gets attractive and if the frame, as well as what's on it, is a little lighter then so much the better. As someone already commented, having a bike for guests is no bad thing. Of course, if the total weight of bike plus myself is only reduced by, say, 3kg, then the percentage saving isn't much but if the aerodynamic and rolling performance is also better then perhaps we end up with a bike thats 10% faster and help me keep up with some of those who have faster bikes or are slightly fitter than me. A few kg less also helps get the bike to and from hotel rooms although, with practice, I'm getting better at getting the Mercury up and down stairs (holding it by the seat tube seems to work best).

A lot of this is thinking out loud in the hope that any flaws in my logic will be identified. Am I right in thinking that a Rohloff hub can be fitted on any bike with a rear disc brake provision although, unless it has an EBB or sliding dropouts, it will need a chain tensioner?

[PH]

It's the wrong time of year for sitting in my chilly garage and trying to weigh each bit on the bike

I was thinking more in terms of reconfiguring what you have into the bike you think will make a difference and using it for the sort of tour where you think that worthwhile.  Yes some time and effort and also expense, burt even a wheel to suit your fork (Or a fork to suit the wheel)  would be an insignificant expense compared to buying a bike and discovering it didn't do what you want.

Am I right in thinking that a Rohloff hub can be fitted on any bike with a rear disc brake provision although, unless it has an EBB or sliding dropouts, it will need a chain tensioner?

There's a way to fit a Rohloff to most dropouts, plenty of detail on the Rohloff website.
The neatest fitting with disc brakes is the Monkeybone, this is what I use on my Airnimal,but it isn't suitable for all.  With vertical dropouts, the bolt securing the OEM2 plate has to be behind the dropout so the rotational forces are pushing the hub into the dropout rather than trying to rotate it out! This rules out using a Monkeybone with chainstay mounted disc calipers.

Edit - got my drop outs mixed up

[mickeg]

...
Am I right in thinking that a Rohloff hub can be fitted on any bike with a rear disc brake provision although, unless it has an EBB or sliding dropouts, it will need a chain tensioner?

Check any frame you consider against the Rohloff specificaitons.  For example, I do not think that there are any 130mm Rohloffs, for a conventional hub (not through axle, not extra wide, etc.) I think 135mm is the only Rohloff hub option.

Many steel frames that were designed for 130mm can be run with a 135mm hub.  My rando bike, I confirmed with the manufacturer that it would work before I ordered the frame.  Their only concern was that I would need to pry the stays apart a bit for the wheel to drop it and that might chip the paint.  For the five years since I built up that bike, 99 percent of the miles (or km) were with a 135mm hub.  I am not using  a Rohloff hub in that bike, so I have no comments on torque arms or anything like that.

[mickeg]

Another perspective:
https://www.youtube.com/watch?v=sDzMrbJTK-U

[energyman]

Another perspective:
https://www.youtube.com/watch?v=sDzMrbJTK-U

A very good video.  (So drilling holes in my toothbrush handle was pretty pointless.)

[JohnR]

There's a way to fit a Rohloff to most dropouts, plenty of detail on the Rohloff website.
The neatest fitting with disc brakes is the Monkeybone, this is what I use on my Airnimal,but it isn't suitable for all.  With vertical dropouts, the bolt securing the OEM2 plate has to be behind the dropout so the rotational forces are pushing the hub into the dropout rather than trying to rotate it out! This rules out using a Monkeybone with chainstay mounted disc calipers.

Thanks for highlighting this important consideration which I think rules out the Spa Cycles' disc brake frames such as the Elan which mounts the caliper on the chainstay (unless I use the less-than-beautiful torque arm). One remaining candidate is the Surly Straggler frame https://www.spacycles.co.uk/m11b0s143p4208/SURLY-Straggler-Frame-and-Forks-700c which has the caliper mount on the seat stay and what appears to be suitable dropouts to avoid a chain tensioner. The www indicates a few examples of Straggler Rohloffs although there's not much detail.

This exercise is gradually moving from being creation of a lighter Rohloff bike to the rehoming of the useful bits from a bike that's too small into something which would be useful to me or someone of similar size (I've got a couple of friends of similar build whom I keep trying to persuade that Rohloff is the way forward). This doesn't reduce the number of bikes in the garaga but it avoids adding another one.

I attach a photo of the shifter side of the Rohloff on the potential donor bike so you can see what bits are there. It's unclear to me if having a QR axle is a show stopper. While a solid axle would be better with slotted dropouts, the Straggler dropouts do have stop screws to restrain the axle from moving.

[PH]

I'm now a little confused about which way you're thinking of going. 
I think you're going to end up with a heavier and lighter build? What I'm not sure of is which the Mercury is going to be!
If you're leaning towards building the other bike as the lighter one and considering non Rohloff specific frames, the Thorn Audax MK4 might be a contender. With discs it'll take 35mm tyres (according to the brochure) but good 32's are probably fine.  It's Rohloff ready, I think that means it has somewhere to attach the OEM2 plate, it'll still need a tensioner, it's probably cheaper and IMO better than the Surly, 858 tubing and a quoted frame weight around 2kg.
A QR in horizontal dropouts is fine, just get a good one.  My Surly Ogre is a nutted axel but I've seen them built up with QR's.  Horizontal dropouts do away with the need for a tensioner at the cost of having to adjust the brakes each time you adjust chain tension, I wouldn't let the difference between them determine a frame, though neither has the convenience of an EBB which would always be my first choice.

[JohnR]

If you're leaning towards building the other bike as the lighter one and considering non Rohloff specific frames, the Thorn Audax MK4 might be a contender. With discs it'll take 35mm tyres (according to the brochure) but good 32's are probably fine.  It's Rohloff ready, I think that means it has somewhere to attach the OEM2 plate, it'll still need a tensioner, it's probably cheaper and IMO better than the Surly, 858 tubing and a quoted frame weight around 2kg.

Thanks for this pointer. That method of restraining the Rohloff hub, and the Audax Mk4 frame being suitable, hadn't crossed my mind. For future reference it's explained at https://www.rohloff.de/en/service/handbook/oem#c27157 . I presume you've previously been through a similar thought process. We might have a way forward although the answer to a question at https://www.sjscycles.co.uk/frames/500-thorn-audax-mk4-disc-frame-gunmetal/ says the weight of a medium frame is 2.46kg but I could pair the frame with disc brake capable carbon forks to help keep the overall weight down. The Spa Cycles Elan 725 frame can accommodate wider tyres but it would be fortutious of the spacing between axle and rack bolt hole was 39.9mm.

The objective is to create both a basic bike (without spending a fortune) that's inherently lighter than the Mercury but one where I would be less inclined to add innumerable extras in order to keep the final weight under control. And, by cannibalising an existing bike, I avoid increasing my collection.

[mickeg]

If you're leaning towards building the other bike as the lighter one and considering non Rohloff specific frames, the Thorn Audax MK4 might be a contender. With discs it'll take 35mm tyres (according to the brochure) but good 32's are probably fine.  It's Rohloff ready, I think that means it has somewhere to attach the OEM2 plate, it'll still need a tensioner, it's probably cheaper and IMO better than the Surly, 858 tubing and a quoted frame weight around 2kg.

...
The objective is to create both a basic bike (without spending a fortune) that's inherently lighter than the Mercury but one where I would be less inclined to add innumerable extras in order to keep the final weight under control. And, by cannibalising an existing bike, I avoid increasing my collection.

If your goal is light weight and if you get a disc frame, if a rim brake fork is lighter you could put a rim brake fork up front, disc in rear.

That is what my titanium bike is, rim brake front and disc rear.  I did not do that for weight, I did that because when I bought the frame I already owned the fork that had the right specifications (rake, crown race to axle length, steerer length, wheel size, and max tire width) that I needed.  It would have cost me over $400 USD more to put a disc up front than a rim brake, that was my driving decision.

[Danneaux]

I came across this older but recently updated link in my library. Even on a budget it can be costly to reduce weight and even an all-out effort doesn't accomplish much (1-1.3kg)...
https://road.cc/content/buyers-guide/8-cheap-ways-get-lighter-bike-186074

I tend to go by the "full water bottle" principle of saving weight on my bikes. I use 3-5 1l bidons on most of my bikes; some have cages instead for 1-3 1.5l bottles plus 2 1l bottles, so it is easy to simply leave some home in cooler weather. Employing all the measures suggested in the article only saved 1,329g at a cost of £605.05. About the equivalent of one of my bottles. 

Time for me to buy a few more cases of dehydrated water. 

Best,

Dan.

[JohnR]

After much cogitation, exchanging of emails, measuring, calculation and dithering I decided that the Spa Cycles Elan frame https://spacycles.co.uk/m11b0s143p4590/SPA-CYCLES-Elan-725-Frame-and-Forks was a better fit for my needs than the Thorn Audax frame although there's the problem of providing torque restraint for the Rohloff hub. The primary disadvantage of the Audax frame for me was the limitation of 32mm tyres with mudguards and 35mm without whereas the Elan can accommodate 40mm with mudguards and 50mm without. I've got some 37mm Marathon Mondials which look narrow compared to the 50mm tyres on the Mercury and the prospect of 32mm or narrower tyres was not attractive although I'm not envisaging going above 40mm but i do like my mudguards.

In addition, while the Elan frame is heavier than the Audax, the longer head tube made it possible to achieve my preferred handlebar height using full carbon (including the steerer) forks while respecting the guidance of maximum 40mm of spacers between headset and stem so the extra weight of the frame is offset by lighter forks. I will also admit to being attracted by the Elan's copper paint.

The frame arrived a couple of days ago and I've fitted it out with the available parts so I could discover what I didn't have and which parts I needed for the Rohloff hub. I had long correspondence with John at Spa Cycles regarding the bottom brack size needed with the Spa cranks in order to get a 55mm chainline. I couldn't completely understand his logic but the recommended 122mm bottom bracket proved to be correct with the chainring on the outside of the spider.

One of the attached photos shows the bike in the current condition with brakes, wheels and tyres (the Mondials) off the donor bike. The brake and Rohloff cables are also those off the donor bike and will be replaced. The other attached photo shows the standard Rohloff axleplate in the rear dropout. My plan is to fit a Rohloff support bolt in the upper mudguard / rack hole where it will partly engage with the axleplate and cut a bit out of the side of the axleplate to engage with another normal bolt in the lower hole for further torque restraint in the low gears. However, it remains to be seen how well the axleplate will engage with the support bolt as it also needs to restrain the anti-clockwise torque (as viewed from this side) that occurs in gears 12 - 14. I may be hunting for a short piece of 10mm ID tube which I can fitt over the support bolt so it fits snugly in the end of the groove in the axleplate.

At the moment the copper bike feels a lot lighter than the Mercury but the difference will reduce as I add the remaining fittings and some baggage. I'm thinking of a small saddle bag plus a small bar bag to put some more weight at the front. I encountered a short section of hill when in Cornwall in October which was steep enough for the Mercury's front wheel to lift off the ground in spite of the relatively heavy steel forks.

The project is now on hold pending arrival of the remaining parts which I ordered yesterday.

[PH]

That's going to be an interesting bike.  I've looked longingly at those frames since they were first introduced, I really can't justify another bike...  A friend has the Ti version and prefers it to his other, more expensive, bikes.
When considering an unconventional Rohloff build, I did consider getting a custom OEM plate shouldn't be exceptionally hard or expensive, but I didn't follow it up.
Cables without guides can also be an issue, aesthetically if nothing else. I've seen a couple of bikes with no outer along the down tube using Problem Solvers backstops
https://problemsolversbike.com/products/brakes/backstop_-_1282