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31
Thorn General / Re: Sherpa forks in Raven Tour frame?
« Last post by mickeg on July 16, 2025, 12:19:49 PM »
I know almost nothing about frame geometry when it comes to handling characteristics, but the tiny bit I know tells me that your trail is a key number.

If you can determine what your current trail is and calculate what it would be with the change, then someone that knows more about geometry than I do could take a guess on what would happen to handling characteristics.

But in the big picture, if you are on tip toe when you stop, even if you can make a slight improvement with a different fork, if you stop on a dip where the ground under your wheels is higher than under where your feet would land, you could be in big trouble.

I assume you have the same bottom bracket eccentric that I have on my Nomad Mk II.  I have seen plenty of photos of bottom bracket eccentrics with the thin part on the bottom instead of top, if you did that and were careful not to overtighten the set screws that hold it in place, could that help?  I stretch rubber bands over the two set screws to prevent them from rotating and loosening.  Thorn advises against this due to possible distortion of the eccentric.

Thicker soles on shoes?

It is a major bummer to have buyers remorse, but that might be where you are headed.

32
Thorn General / Re: Sherpa forks in Raven Tour frame?
« Last post by PH on July 16, 2025, 12:08:59 PM »
I think you've covered it, the question is how it effects handling and there's a good bit of subjectivity in that.  It's probably that subjectivity, rather than any practical reason, which has Thorn sitting on the fence.  Some people have a preference  that has to be mm perfect, but I note Thorn have some current forks, for the same models, which vary between 385 and 410mm. 
When i set up an EBB bike I do so with the BB in the centre position and accept the fore/aft variation of +/- 6mm and the 3mm height variation, others change their saddle to correspond.  The third option, which I did for a while, is to use a half link to minimise BB movement.  I mention this because if BB height is critical, then getting the EBB to maximise it could be useful.
.
33
Rohloff Internal Hub Gears / Re: Adjusting the Chain Tension on the Nomad Mk II Bottom Bracket Eccentric
« Last post by Notts0115 on July 16, 2025, 12:01:36 PM »
 No tips from me, but I’m pleased you have highlighted a very useful older post that I couldn’t find - thank you!
34
Thorn General / Sherpa forks in Raven Tour frame?
« Last post by Andyb1 on July 16, 2025, 10:19:26 AM »
When riding my 537L framed Raven Tour for the first time I realised how high the BB is which results in a high saddle and possible instability when I stop as I am on tip toe.
The forks fitted are the standard twin plate type with an L1 measurement (axle to crown bearing) of 410mm.  Sherpa forks have L1 of 370mm, which I have calculated will drop the BB height by 16mm, making it the same as another bike I ride.

So has anyone else done this change?   If so did you use 46 or 52mm offset sherpa forks?

I am going to make the change as I have the parts and see how it feels; I expect the shorter forks will make the bike feel more responsive but hopefully not twitchy.

I have spoken with Thorn about it and they could neither confirm or deny that the change would work, which I can understand.  But it was not a ‘No, No’.
35
Rohloff Internal Hub Gears / Re: Adjusting the Chain Tension on the Nomad Mk II Bottom Bracket Eccentric
« Last post by Andyb1 on July 16, 2025, 10:07:33 AM »
Just resurrecting this as my Raven pinch bolts came loose yesterday on my way back from SJS (possibly due to ACF50 in the frame?).  I was surprised how slack the eccentric was in the frame with the bolts loose - definitely not seizing!  Earlier in this thread mickeg’s suggestion of using pieces of innertubes to lock the bolts sounds good, Thorn have suggested locktite, what (if anything) do others use to keep the pinch bolts tight?
36
Muppets Threads! (And Anything Else) / Re: The Return of Global Warming?
« Last post by julk on July 15, 2025, 04:46:40 PM »
John,
that looks like a nice scythe, but I would plump for one with a wooden snath.

I got the one I use from https://www.thescytheshop.co.uk/index.html plus a shorter one for my wife,
and a selection of blades for use with length in inverse proportion to what is being scythed.
Julian
37
Thorn General / Re: New to me Raven Tour
« Last post by mickeg on July 15, 2025, 01:56:15 PM »
Quote from: Andyb1 on July 15, 2025, 11:54:59 AM
...
So what are the advantages of presta on wide rimmed bikes with low pressure (~50psi) tyres?
...

Wide tires with low pressure, Presta is not much of an advantage. 

In my case it goes back several decades, I was riding narrower high pressure tires with Schrader valves and often lost several PSI when I took the chuck off the tire.  And I often lost several PSI when using a gauge to check pressure.  So, when I started to buy Presta, I totally stopped buying anything Schrader.

But with lower pressure and wider tires, any pressure loss when you take the chuck off will be minimized.

Gauges, I have a Presta gauge, but almost never use it.  The pumps I tour with have built in gauges.  Those gauges are not very good, probably are plus or minus 5 PSI, but that is good enough for me.

If you are happiest with Schrader, I see no reason to change.  You explained why you wanted to make the change to Schrader.  And if you had Presta only pump that could not be converted to Shrader when you could only buy a Shrader tube, I can see that as a big reason. 

I carry pumps that can be converted.  Exception, I use a Presta only pump on my rando bike and road bike, but those bikes stay in places where I can buy Presta.  And those bikes have rims that are Presta only.  That said, I still have a Schrader adapter on each of those bikes, just in case I needed to use a car pump.

I will admit that when I am filling up a 57mm wide tire at home, I am inclined to use the Schrader adapter on my Presta so that I can use an electric pump.

I use tires as narrow as 40mm on my Sherpa, 37mm on my light touring (titanium) bike, so I do pump those up to higher pressures when touring.
38
Thorn General / Re: New to me Raven Tour
« Last post by Andyb1 on July 15, 2025, 11:54:59 AM »
The old presta vs schrader debate!
I used to have everything presta but after getting stuck a few years ago when my bike pump broke and I could not pump up my repaired presta valved innertube (but I could have borrowed a car pump) I started to go to schrader, but it is taking years to make the change over!  Consequently I still use some presta valved innertubes and carry adaptors to screw on the top to go to schrader.

Advantages of schrader to me are:
- always a car pump around!
- when I damaged my schrader hand pump in India I bought a good alternative for £5 - no presta pumps available
- with lower tyre pressures / wider rims schrader work fine (maybe not so good for high pressure / narrow or deep aero type rims, but I don’t use those).
- my pressure gauges are all schrader ones
- valve stems stronger - I have bent the screw ends of presta valves in the past - and last year in cold weather I miss-fitted a long stemmed presta valve which blew the next day as it was not fully pushed through the rim due to jamming on the pastic schrader / presta hole adaptor.
- schrader valve inserts easily changeable at car garages if required.
- presta valves can undo a little and give a leak
So what are the advantages of presta on wide rimmed bikes with low pressure (~50psi) tyres?

Tyres.  I want to use up the tyres I have so will probably run on a 2.0 dureme front / 1.75 marathon plus at the moment and go from there.  Thanks for the recommendations Martin, I will come back to those options in due course.

I weighed my sherpa and raven many times yesterday as I swopped parts across like the saddle, pedals etc and the raven was about 0.5kg heavier once different tyre weights were accounted for.  The sherpa is now set up as a rather nice looking flat barred bike with rear rack and shiny stem weighing in at 13.0kg. Unfortunately it will have to go once I get a few miles on the raven to make sure all is good.
39
Thorn General / Re: New to me Raven Tour
« Last post by martinf on July 15, 2025, 07:02:02 AM »
Quote from: Andyb1 on July 14, 2025, 10:09:07 AM
and a dureme tyre replaces the front Marathon.

I'd also replace the rear tyre with a kevlar bead Mondial at 675g in the 50x559 size. This should save a fair bit of weight over a Marathon Plus and work better if you use rocky tracks. The wire bead version of the Mondial is cheaper, but heavier at 740g. And not quite so good for sidewall protection and puncture resistance.

Or, if you will be on tarmac most of the time, put the Dureme on the back and a light tyre on the front, for example :

https://www.bike24.com/p2360101.html

I use the Continental Contact Urban on my Bromptons, it has reasonably good puncture resistance and low rolling resistance. Also fairly light at 590g and relatively inexpensive. The 47-559 version is slightly lighter at 560g.
40
Thorn General / Re: New to me Raven Tour
« Last post by mickeg on July 15, 2025, 12:45:03 AM »
Quote from: Andyb1 on July 13, 2025, 08:20:41 PM
...   Change presta innertubes to Schrader……
...

I have been thinking about this, why would you want to do that.  I can see making sure your rims are drilled to Schrader size hole in case that is the only tube you can buy, I drilled the rims on my Nomad Mk II for that reason.

But I still want Presta on everything that does not have a motor in it.

I have a Schrader to Presta adapter threaded on one wheel on each of my bikes, just in case I might want it some day.  And a Schrader valve cover over the top of that adapter.

I used to use the metal Presta Savers, but had corrosion problems.
https://www.sjscycles.co.uk/rims-tape/wheels-manufacturing-presta-tube-stem-saver-fits-schrader-rims/

Now use the plastic ones.
https://www.sjscycles.co.uk/rims-tape/mavic-rim-valve-hole-drilling-converter-insert-schraeder-to-presta/

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