Author Topic: Looking for a lighter Rohloff bike than my Mercury  (Read 5122 times)

mickeg

  • Hero Member
  • *****
  • Posts: 2288
Re: Looking for a lighter Rohloff bike than my Mercury
« Reply #45 on: December 01, 2021, 07:06:27 AM »
...
Some people just prefer the idea of a lockring and a tool rather than learning the technique of fitting and removing a circlip.

Apparently the sprockets on the splined carrier with the split ring can loosen up and become noisy.  The sprockets develop looseness on chain drive sprockets too, but apparently noise is not a factor on chain drive.  I am only repeating what I have read here, I have not seen the lock ring type carrier.

I am guessing that my S&S coupler wrench would work on the lock ring, so if I had a choice I would probably choose that one for my chain drive Rohloff bike.


JohnR

  • Sr. Member
  • ****
  • Posts: 474
Re: Looking for a lighter Rohloff bike than my Mercury
« Reply #46 on: December 01, 2021, 10:18:10 PM »
I've ordered my own Rohloff tool 8508 from SJS and I plan to use my pipe wrench on the screw-on adaptor as there can't be much of a second hand market for them.

I've also looked at the possibility of fitting the support bolt between the two bolt locations. It fits fairly snugly (see photo) and appears to be the best option to date. I'm thinking of improvising the bolt holder from two pieces of 4mm thick steel (probably stainless) flat bar. The dropouts are 3mm thick but there's about a 2mm gap between them and the axleplate so 4mm material reduces that gap. One piece of the steel will be on the outside of the dropouts but I'll make another piece that is carved to fit the valley between the bolt holes. The two can then be bonded with a thin layer Araldite (which IIRC used to be advertised as stronger than steel) before I drill the holes. A total of 8mm of steel should prevent any bending of the bolt. I've also ordered a box of assorted M5 cap screws to add to my collection. I need to sensure that they don't significantly protrude through the dropout and foul the axleplate.

JohnR

  • Sr. Member
  • ****
  • Posts: 474
Re: Looking for a lighter Rohloff bike than my Mercury
« Reply #47 on: December 03, 2021, 07:44:06 PM »
Progress  :) :) . SJS moved quickly on my order for Rohloff tool 8508 and with the help of first class post it arrived today. With the help of a pipe wrench and encouragement from a hammer the screw-on sprocket adaptor finally yielded. There was plenty of what looked like anti-seize on the threads but 3,000 miles of cycling had got it somewhat tight. So I now have a bike with both chainring and sprocket and a chain between them with the chain tensioner on a low tension setting. I've put the Rohloff support bolt in the upper mounting hole and plan to take a short ride tomorrow morning on some local rough degraded cycle paths to see how the bike feels. I'll refrain from tackling any steep hills until I've got an improved torque management setup.

JohnR

  • Sr. Member
  • ****
  • Posts: 474
Re: Looking for a lighter Rohloff bike than my Mercury
« Reply #48 on: December 04, 2021, 09:51:09 PM »
The bike has been out for a couple of miles. The steering felt a bit different from the Mercury, perhaps because it has narrower AHS handlebars or there may be subtle differences in geometry. I've got wider AHS bars as the alternative but wanted to find out if the narrower bars (which I used on the bike which donated the Rohloff) felt as they are slightly easier to manoeuvre through obstacles and into buildings. The ride felt OK and the Brooks C17 saddle seemed comfortable (but 2 miles is far too short to reach a judgement). The photo shows the drivetrain setup.

The bike weighed 13.5kg in the configuration shown (except the saddlepack was removed). This seemed a lot so I removed the bags, water bottle and pump off the Mercury to get it to a comparable condition and came to 16.6kg. That weight, however, includes the forbidden kickstand, some mud and heavier grips on the handlebars so the true weight difference between the bikes appears to be around 2kg.

I'm already missing having a kickstand on the new bike and have ordered a Chinese copy of the Upstand https://www.amazon.co.uk/gp/product/B08T1S2P8L to see how I get on with it. However, I've got my eye on the non-folding Commuter Upstand https://upstandingbicycle.com/shop/the-commuter-upstand/ and have been in contact with the manufacturer who can send by international mail for $15. My interpretation of the current UK customs and tax rules is that the order would fall below value threshold attracting import charges at this end so I may order one once the Christmas period is over. The alternative is extend the proposed adaptor for the Rohloff support bolt to include mounting holes for a conventional kickstand - an adaptation of this https://www.sjscycles.co.uk/gear-spares/thorn-dropout-adaptor-with-kickstand-mount-18-mm. A proper kickstand, however, is running contrary to the weight reduction objective.

PH

  • Hero Member
  • *****
  • Posts: 1751
Re: Looking for a lighter Rohloff bike than my Mercury
« Reply #49 on: December 05, 2021, 12:40:53 AM »
the true weight difference between the bikes appears to be around 2kg.
Be interesting, to me anyway, to take the wheels out of the equation and weigh again.
My friends steel Elan, with a full carbon fork (But not the one you have) and Shimano GRX groupset (2X11), whatever Spa do as a lightweight handbuilt wheels, road saddle, lightweight conti 32mm tyres, fancy mudguards... comes in well under 12kg, he was hoping it'd be under 11 and may get there yet.
Regardless of the weight, did it feel faster? I see you have some pretty chunky tyres, I know it's still a work in process, but for the usage you've described that's probably where the biggest advantage lies.

JohnR

  • Sr. Member
  • ****
  • Posts: 474
Re: Looking for a lighter Rohloff bike than my Mercury
« Reply #50 on: December 05, 2021, 09:47:56 PM »
I took the frontwheel off and it weighed 1.67kg complete with a 37mm Marathon Mondial Tour tyre (which Schwalbe says weighs 0.57kg) and inner tube. Those tyres were on the wheels already and will stay there until the roads become less mucky when the tyres will be replaced by 40-622 G-One Speed (weight 0.465kg). The rims are tubeless ready American Classic Hurricane (approx 2014 vintage although new along with the rest of the bike when I bought it in 2019 ago). If I can get them to seat on the rims then that will save about 0.3kg on the weight and improve the ride. A hollow axle crankset might also save a little weight as would narrower tyres, ditching the mudguards, Chainglider (and could then fit an aluminium chainring), fitting simple handlebars and using a lightweight saddle. I didn't have a weight target but was wanting less heavy than the Mercury and less temptation to add more baggage than necessary. A Rohloff hub will never compete on weight with a lightweight groupset.

I went out today for what I expected to be 4 miles but ended up travelling 12 miles on a route which needed nothing lower than 8th gear. I had adjusted the handlebars after yesterday's ride and they felt much better and, while the bars appeared, when looking at the bike, to be higher than I intended this seems to be an illusion as my body position felt fine. On the first part of the trip the bike felt fast but then the final part was into the wind which was like cycling through treacle. I'll need a reasonably calm day and a trip around a longer (~25 mile) circuit before I can get a proper feel for whether the bike is faster than the Mercury (which I've just switched from G-One Speed tubeless to Panaracer GravelKing SK with tubes for some extra winter grip and noticed that the bike felt slower). Also of great interest to me is how well the bike felt on rough bits of road and in this respect it was OK.

One little annoyance is that I'm getting some rubbing noise from the Open Chainglider. It seems to be diminishing with usage so I hope it will become as quiet as the Chainglider on the Mercury. I'm now waiting for some bits of stainless steel for the Rohloff torque anchor and once that is done then I can look for a gap in the weather for a trip around a longer circuit.

ourclarioncall

  • Sr. Member
  • ****
  • Posts: 484
Re: Looking for a lighter Rohloff bike than my Mercury
« Reply #51 on: December 07, 2021, 10:06:25 PM »
You could get another bike thatís really heavy and ride it for ten minutes , then go back to the Mercury

Tricking your nervous system or something like that ☺️ It will make the Mercury feel super light in comparison

A bit like how bodybuilders do with lifting weights

I thinking the lighter and weaker we go with things , the benefit might be short lived and wear off after a while unless we also have something that is also stretching us in the opposite direction

I find this with playing guitar and setting it up to play with lighter strings and lower action . The initial results can feel amazing but our bodies seem to get used to it too quick. Our hands get weaker coz thereís less tension

I was just looking at Thorns weight recommendation for their frames today (Mercury included ) it got me thinking . Although the Mercury is light , it can still carry a fair bit of weight . So maybe itís not that light 🤔

JohnR

  • Sr. Member
  • ****
  • Posts: 474
Re: Looking for a lighter Rohloff bike than my Mercury
« Reply #52 on: December 12, 2021, 10:16:32 PM »
You could get another bike thatís really heavy and ride it for ten minutes , then go back to the Mercury

I didn't think the Mercury was heavy until I saw some of the other bikes on a group bike ride. Part of the problem was that having a bike designed to carry a load encouraged me to carry more than necessary.

My Mk. 1 torque anchor (3 holes in a 20mm x 35mm piece of 4mm thick steel) wasn't to my satisfaction (using a hand held drill isn't very accurate) so I'm I'm now planning a Mk. 2. However, I wonder if I'm over-engineering a solution since one of the Rohloff options uses an M5 bolt https://www.sjscycles.co.uk/hub-spares/rohloff-oem2-adapter-for-m5-fender-luggage-rack-bolt-8552 and a quick calculation which might be wrong) suggests that there isn't a very big factor of safety against that bolt shearing off under Rohloff's worst loading condition. As one of my mounting holes is 10% more than the recommended distance from the axle then I've effectively got a 10% higher FoS. If only the fingers on the OEM2 axleplate were a couple of mm longer then I'd be happy to go that route as the permanent solution.

While waiting for the permanent fix I've taken the bike out on a couple more rides which didn't require going lower than 6th gear. After the first ride with the steering not feeling completely OK I've changed the handlebars to the longer Ergotec AHS bars (SJS are selling the silver version at a fair price https://www.sjscycles.co.uk/handlebars/510-humpert-ahs-basic-sport-handlebars-cw-comfort-barends-254mm-clamp-silver) and now the steering feels just the same as the Mercury - probably a matter of what I've got used to. Today's ride was 27 miles and no slower than I would expect with the Mercury but the wind wasn't favourable. The Chainglider has got quieter but the second half of the noise had another slight rubbing noise from, I think, some muck inside the rear mudguard. The damp weather cause caused filthy roads not helped by large vehicles spreading muck from the edges towards the middle. Some heavy rain would temporarily get the roads clean.

I've also noticed that the Rohloff hub seems to have become quieter in low range than when on its previous bike. I'm wondering whether the larger diameter aluminium tubes on that bike made an effective noise amplifier.

JohnR

  • Sr. Member
  • ****
  • Posts: 474
Re: Looking for a lighter Rohloff bike than my Mercury
« Reply #53 on: December 15, 2021, 10:09:05 PM »
I got fed up with waiting for a piece of 1mm thick steel which would form part of the planned Mk 2 support bolt carrier and have implemented Mk 3 which involved cutting a notch in the axleplate so that it's restrained from rotating by 5mm bolts in both the mudguard / rack mounting holes. I also put a piece of 1mm thick aluminium on the end of the smaller finger of the axle plate so that it's a fairly tight fit on the Rohloff support nut (part 8552) so there's no movement when changing the torque direction (above / below 11th gear). The notch in the axleplate rests against the head (8mm dia) of a 5mm capscrew threaded from inside to outside of the dropout. The photos should illustrate how it's put together.

The main disadvantage compared with the planned Mk 2 restraint (which would place the 6mm support bolt in the valley between the two mounting holes) is that the Rohloff cables are hanging below the chainstay so I'll probably improvise a rigid support. It's also slightly more fiddly getting the wheel into the drop-outs.

The next task is to take the bike up my worst local hill (approx 1 in 6) which I normally crawl up in 3rd gear. Perhaps the worst test I can do is try accelerating from hill start in 1st or 2nd gear to add a bit more load. I don't know of an even steeper hill in my area.

JohnR

  • Sr. Member
  • ****
  • Posts: 474
Re: Looking for a lighter Rohloff bike than my Mercury
« Reply #54 on: December 18, 2021, 06:33:51 PM »
The less heavy bike project is effectively complete. It's clocked up over 100 miles including a couple of trips up my worst local hill without any signs of distress. Since my last post I've changed the mudguards (SKS Bluemels from Wiggle's outlet on ebay https://www.ebay.co.uk/itm/154739257339) although there was a bit of fun routing the front nearside stays around the disc brake rotor and I tidied up the cables including an improvised holder for the Rohloff cables below the chainstay. I'm planning to make minor adjustments to the handlebar position in the quest to find the best balance between wind drag and comfort.

It's 2.3kg lighter than the Mercury in similar configuration. I could reduce the weight further by sacrificing features I want such as a comfortable saddle, the AHS handlebars, flat pedals with grip, some chain protection and the mudguards (I bought these cut-down guards for the summer https://www.amazon.co.uk/gp/product/B004R4I6XI). Hollow cranks might save a few grammes. Whether this bike is faster remains to be seen as the time around my various circuits depends on a range of factors, such as weather (particularly wind speed and direction) and how I'm feeling with the bike itself being a lesser factor. It's as comfortable as the Mercury on a range of surfaces in spite of narrower tyres although I think the Mercury's 50mm tyres are slightly better on gravel.

Thanks to all for the helpful comments that have encouraged me to get to the end of this project which has resulted in a good Rohloff-equipped bike for somewhat less cost than a new one. Hindsight is a wonderful thing - I should have thought of this before I bought the Mercury! The next unknown is whether the Mercury is redundant and needs to be listed in the for sale forum.

PH

  • Hero Member
  • *****
  • Posts: 1751
Re: Looking for a lighter Rohloff bike than my Mercury
« Reply #55 on: December 18, 2021, 11:04:23 PM »
Looking good, the cable run isn't as messy as I thought it would be.  I have one of those blue Brooks, after a lifetime of saying saddles should be black, though at least mine is on a blue bike  ;)
Your post does have me scratching my head, as has much of this thread.  Where does that 2.3kg come from? I know about 600g will be the fork, what about the rest? If there's any difference in frame weight it'll be minor and I'd have thought in favour of the Mercury.
And now you're contemplating selling the Mercury  :o :o :o
Your bikes and your choices of course, but I still think, as I said at the start of this thread, trying your Mercury in a light build would have given you a practical benchmark.

JohnR

  • Sr. Member
  • ****
  • Posts: 474
Re: Looking for a lighter Rohloff bike than my Mercury
« Reply #56 on: December 19, 2021, 07:33:04 PM »
Unfortunately, Wiggle's sale of C17 saddles at £59.99 didn't include the copper coloured version.

I may have over-stated the weight difference as I should have given both bikes a wash before the weighing session and the Mercury has has more opportunity to collect dirt, particularly on the inside of the mudguards. Both weights were without the saddlepacks.

In the ideal world I would dismantle each bike into the constituent parts and weigh them individually but that's not on my to-do list. :o While the Mercury's 983 steel is stronger than the 725 used in the Elan frame, the latter is one size smaller (52 vs 55L) and may be designed for a lighter loading (Spa doesn't give numbers) but the weight comparisons earlier in this thread were between the Elan frame and the Thorn Audax frame, not the Mercury frame which is rated for higher loading than the Audax. BTW, I've accidentally discovered how thin the metal is in Elan's top tube: Tap it gently with a bit of metal and it rings like a bell (there's nothing attached to this tube to dampen the sound).

My Mercury's forks are the heaviest option, with disc brake capability and chunky axle which means the maximum weight difference between those and the full carbon (including steerer) forks on the Elan and this is probably the biggest component of the weight difference. Otherwise it's the sum of small differences. The rims on the Elan are narrower (17mm internal width) and look to be lighter than the rims on the Mercury. The 48-584 GravelKing SKs are about 40g each heavier than the 37-622 Marathon Mondials on the Elan plus there will be a proportional difference in the weight of the tubes and mudguards.The Mercury's EBB must add a bit of weight (which might be offset by the chain tensioner on the Elan), both bikes have square taper bottom brackets, fairly chunky cranks and the same pedals (MKS MT-FT). The Mercury has a full ChainGlider while the Elan as the open ChainGlider. Both have the same handlebars although the Knog Deluxe bell I've put on the Elan will be lighter than the traditional bell on the Mercury. Both bikes have Wiggle's carbon seatpost. There's a small difference between the advertised weights of the C17 (464g) and Aravis Ti (425g) saddles which is in favour of the Mercury.

I agree that I could have had a Mercury in a lighter specification but, if I didn't want to forego a front disc brake and minimum 40mm tyres with mudguards or a good saddle then I don't see much option for weight reduction. In addition, as I think I noted at the start, this was also an exercise in recycling as much as possible from a too-small aluminium-framed bike to build something more attractive that would be, I hoped, be lighter than the Mercury. One part that I didn't yet recycle was the Sram X5 hollow axle cranks and bottom bracket and that was because the cranks are 175mm. However, I'm tempted to try as that BB is 68mm and should fit the Elan frame complete with the right chainline. Sensibly the hollow axle should mean less weight.

Seeking a new home for the Mercury was always a background thought as I am trying to reduce my bicycle collection. I've nothing against the Mercury, as 7,800 miles in 17 months should testify but my group bike rides have revealed that it's over-engineered for the touring I've done (and hope to do more of) which isn't real touring in that there's a van to carry the baggage. There's probably someone out there in greater need of the Mercury. Should I decide to try some credit card touring then I can put a rack on the Elan. First I must clock up some more miles on the new bike.
« Last Edit: December 19, 2021, 07:36:07 PM by JohnR »

PH

  • Hero Member
  • *****
  • Posts: 1751
Re: Looking for a lighter Rohloff bike than my Mercury
« Reply #57 on: December 19, 2021, 11:41:12 PM »
Oh well, your choices.  There's no reason why you should prefer the Mercury to the Elan, I wouldn't know if I would, so I certainly wouldn't know for someone else.  The difference is I'd want to base that on experience rather than theory, I'd ride the Mercury with the same wheels and fork to make a genuine comparison.

Just on the factual stuff:
In the ideal world I would dismantle each bike into the constituent parts and weigh them individually but that's not on my to-do list. :o While the Mercury's 983 steel is stronger than the 725 used in the Elan frame, the latter is one size smaller (52 vs 55L) and may be designed for a lighter loading (Spa doesn't give numbers) but the weight comparisons earlier in this thread were between the Elan frame and the Thorn Audax frame, not the Mercury frame which is rated for higher loading than the Audax. BTW, I've accidentally discovered how thin the metal is in Elan's top tube: Tap it gently with a bit of metal and it rings like a bell (there's nothing attached to this tube to dampen the sound).
The Merc is Reynolds 853, I'm sure you knew that.
I think the Elan, like all Spa steel bikes, only uses 725 for the main three tubes, the minimum to be able to use a Reynolds sticker.  The stays are generic steel, nothing wrong with that, though it's probably not heat treated and therefore needs to be a bit thicker.  The lightest gauge of 725 main tubes is 0.8/0.5/0.8, that's also the most common 853 gauge and I expect what's used on the Mercury, though 853 is also available 0.7/0.4/0.7.
I'm not telling anyone what they should do, but if you choose the Elan over the Mercury on the basis that it's a significantly lighter bike that isn't an evidence based decision. 

JohnR

  • Sr. Member
  • ****
  • Posts: 474
Re: Looking for a lighter Rohloff bike than my Mercury
« Reply #58 on: December 20, 2021, 10:18:11 PM »
The Merc is Reynolds 853, I'm sure you knew that.
I think the Elan, like all Spa steel bikes, only uses 725 for the main three tubes, the minimum to be able to use a Reynolds sticker.

I'm not telling anyone what they should do, but if you choose the Elan over the Mercury on the basis that it's a significantly lighter bike that isn't an evidence based decision.
Yes, there was a keyboard mulfunction regarding the steel type used in the Mercury.

I'm not disputing that I could have rebuilt the Mercury to be less heavy but I was trying to use the good parts off a bike that was too small to build something usable and, I hoped, would be less heavy than the Mercury without a massive financial outlay. For the price of the Mercury frame I could have got the Elan Ti frame which would definitely win the weight comparison. Anyway, I've now got two good bikes and a 49cm aluminium frame on which I place no value.

Moronic

  • Full Member
  • ***
  • Posts: 153
Re: Looking for a lighter Rohloff bike than my Mercury
« Reply #59 on: December 22, 2021, 09:14:53 AM »
This thread started to make a lot more sense to me when I looked up the disc front fork Thorn supplies for the Mercury and discovered it weighed 1.5kg.

That's 450g more than my ST fork and 650g more than the Reynolds 853 fork that Thorn also offers for the Mk 3 Mercury.

There's not only the added mass. Thorn says the ride suffers, rating the fork at 4.5 for comfort against the 853 fork at 10. The ST fork is rated at 8.

It is all very well to say that some comfort is returned by a fat 650b tyre but it comes back in another way. The perception of liveliness from the frame likely suffers.

Thorn used to offer a carbon fork with disc brake for the Mercury. Andy B reports in the megabrochure that he switched his personal lightweight Mercury from the disc brake carbon fork to the rim brake 853 fork and preferred the latter (p61).

If you have to have a disc front brake then I can see why the built up Spa bike could save you nearly a kilogram in the fork alone. FYI on the Mercury frame, I can confirm that Thorn quotes 0.8/0.5/0.8 for the main tube thicknesses.

Anyway good luck John with the experiment - I look forward to further comparisons as you gain experience with the Elan. I am tempted to say that if I had been on a similar quest I would simply have gone for an 853 fork, lighter rims and the lightest tyres I could find - Rene Herse Babyshoe Pass 650bx42mm are rated at 373g in the extralight casing. But then I like the rim front, disc rear brake set up I have on my Mercury and I don't assign a lot of value to braking performance.