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Looking for a lighter Rohloff bike than my Mercury

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JohnR:

--- Quote from: Danneaux on February 01, 2022, 08:45:44 pm ---Carbon posts don't get along well with grease, which can cause slippage. Using a carbon assembly paste will often fix the problem and keep a carbon post secure. By any chance, did you use carbon assembly paste on yours? If so, then I'd suspect one of the other causes.

--- End quote ---
I removed all traces of oil and grease. I tried carbon assembly paste which made things worse as the jelly appeared to act as a lubricant.

I think the underlying problem was the clamping arrangement. I didn't want the slot at the top of the seat tube to cut into the carbon post so I rotated the clamp (bolt at the front) to try to spread the clamping load but the result was that it couldn't get tight enough.


--- Quote from: mickeg on February 01, 2022, 10:16:34 pm ---I have no experience with carbon anything.  That said, I had an aluminum seatpost that would slip, slipped on different bikes so I think it was slightly undersize. 

It was painted black.  Two or three additional layers of paint from a spray can made it a bit bigger, stopped slipping.  Let the paint harden for at least a few weeks, so it would be fully hardened before I used it.

--- End quote ---
I also had a slipping Thorn seatpost on my Mercury and my calipers suggest that it was slightly undersize. In this case the fix was 6 layers of aluminium cooking foil between the shim and the seat tube.

Overall, I look on the carbon seatpost as a useful experiment which was successful in improving comfort and reducing road buzz. However, there's the lingering doubt that it might break at the wrong moment particularly on a longer ride with a loaded saddle bag adding to the bending force. The titanium post removes these worries without providing the harsher ride of an aluminium post. With hindsight (a wonderful thing) I should have tried the experiment some time ago as it lets me run the tyres a bit harder.

PH:

--- Quote from: JohnR on February 02, 2022, 08:02:07 am ---I think the underlying problem was the clamping arrangement. I didn't want the slot at the top of the seat tube to cut into the carbon post so I rotated the clamp (bolt at the front) to try to spread the clamping load but the result was that it couldn't get tight enough.
--- End quote ---
Yes that would do it, without the two gaps lining up the effectiveness will be reduced.
Those Ti posts look good, though I've heard people having issues with the saddle clamp, I'd be tempted, except prefer more layback.

JohnR:

--- Quote from: PH on February 02, 2022, 09:03:59 am ---Yes that would do it, without the two gaps lining up the effectiveness will be reduced.
Those Ti posts look good, though I've heard people having issues with the saddle clamp, I'd be tempted, except prefer more layback.

--- End quote ---
I reckon its actually 25mm offset as listed at https://www.oraeng-tw.com/sp002-bike-seatpost.html and seatposts with even more offset aren't easy to find. 20 to 25mm suited me as the bike was set up for the wiggle carbon seatpost which is 22mm offset.

At the moment my biggest complaint about the saddle clamp is that access to the main both is impeded by the edge of the saddle.  There's also what is marked as a security screw on the back of the clamp. In the absence of any additional guidance I assume this should be tightened when the saddle is in place and adjusted.

PS: Having checked the saddle position today because I felt on yesterday's ride that it needed moving forwards I discovered that it had slipped backwards so it isn't gripping the rails as tightly as needed. I've now given the problem a little thought and will get the seatpost and saddle off the bike for a closer examination. My current thinking is a layer or two of car touch-up primer pain on the inside of the jaws that grip the saddle rails or, if there's a bigger gap to be filled, a thin layer of epoxy resin glue. It's a fine balance as too much filling will impede the teeth on the vertical ange adjuster from engaging.

JohnR:
I think I've finally fixed the saddle slipping backwards problem. Paint didn't do any good so I applied a thin layer of slow setting Araldite  to the inside faces of the rail clamps and left it overnight on a radiator to harden. After that I had to file a lot off until the clamps were a snug fit on the rails. However, that wasn't enough by itself to stop the saddle moving back but I had noticed that while I had everything tight before the ride that the saddle rotated backwards slightly once when I went over a substantial bump despite my efforts to ensure that everything was tight. This indicated that the teeth controlling the rotation weren't properly engaged at the start (and I couldn't have the saddle in my preferred position of horizontal) but also meant that once those teeth were engaged then the grip on the rails was reduced until the bolt was retightened. After resetting the saddle distance from the bars, making it horizontal and putting a little gease on the clamp bolt (to help get it tight) I took a large Allen key of the appropriate size on the next ride. Then, once I felt the saddle rotate slightly, I stopped and retightened the bolt. There has then been no further saddle movement on that ride (yesterday) or today.

The other ongoing experiment has been the handlebar height on the basis that if I can get my body a bit lower then there will be less cursing of the headwinds. Over several weeks I've been intermittently dropping the bars in 5mm increments starting at a height similar to what I had on the Mercury to find the limit where I felt uncomfortable. Yesterday I took the drastic measure of flipping the 7 degree 110mm stem from up to down but moving it to the top of the steerer which resulted in a 20mm drop from the previous bar position. One ride revealed that there was too much weight on my arms so the stem has been flipped again and moved down the steerer. A zero degree stem higher on the steerer would likely be the optimum solution but fixed zero degree stems aren't common and I don't want the extra weight of an adjustable stem.

JohnR:
It's a year since I started this and an update is appropriate. The copper-coloured Elan 725 provided 6 months of trouble-free cycling including Lowestoft - St Davids (supported by a van carrying the baggage). There was only a dozen of us and I was at the back on the flat roads of eastern England but near the front when we reached the Welsh hills and the lower gearing than most derailleur bikes came useful.

However, I then started thinking about how I could further improve on what I had built. Further reading made me realise that a titanium frame not only provides a further weight reduction but also further improves comfort as it's less stiff than steel. As I'm under 65kg and normally have no more than 5kg of baggage I don't want a strong frame but something that helps absorb the rough bits of road. That's where I went wrong with choosing the Mercury - it's designed for at least 20kg more than I'm likely to need (the Mercury is still waiting to be rehomed).

I was very happy with the geometry of the 52cm steel Elan frame so I arranged to visit Harrogate while on the annual car holiday and inspected the titanium Elan frame and satisfied myself that there would be no serious problems with fitting the Rohloff hub. After the holiday the Ti frame was delivered and I spent a day moving all the components to the new frame. Modifying the Rohloff OEM2 axleplate to fit the Elan Ti frame was easier than with the steel frame. It just required deepening the valley between the two fingers as the axle - rack bolt hole spacing was 36mm instead of Rohloff's specified 40mm and putting Rohloff support bolt 8560 through the rack bolt hole. Perhaps it was wishful thinking but the rough bits of road on one of my circuits immediately felt smoother. Had I appreciated this advantage of the titanium frames then I would have gone that route instead of steel a year ago.

After a few hundred miles on this bike I started to wonder what else I could improve. One problem was that a Carradice Super C saddle pack was bouncing on the rear mudguard and I used a strap through the saddle rails to lift it which reduced the available capacity. After more miles of pedalling and thinking I realised that smaller wheels would not only help with this problem but also address another problem which was that with the optimum saddle-pedal spacing I could only put a few toes on the ground when stopped. My Mercury has 584 rims and I never had problems caused by the height of the bottom bracket. So I commissioned Spa Cycles to build me a new 584 front wheel and rebuild the Rohloff hub into a 584 rim. (I chose Spa for this work as they stocked Kinlin TL-21 tubeless rims in the 584 size). As noted elsewhere, I fitted the Rohloff flange support rings before the hub went for the wheel build.

One photo show the bike in its current condition with a Carradice Maxi saddlepack (the Super C saddlepack is a size bigger although the nominal capacities are the same) and I've just fitted full mudguards instead of clip-ons now the weather has turned wetter. The tyres are Schwalbe G-One Allround (35mm on the front and 40mm on the rear) which were very easy to mount tubeless on the Kinlin TL-21 rims. The other photo is a detail of the rear hub showing the Rohloff axleplate.

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