Mercury for a gravel event?

[aggs]

I would appreciate your views on using a Mercury for a 200km gravel event I have entered in April at Kielder forest , with 3500m of climbing. virtualy all riding is on forest roads.  Gulp!!

I have a carbon cx bike but it really is set up for shorter rides and the longest I have done is 100km with a mix of on and offroad on 35mm tyres, I am currently planning on using this bike, but would appreciate thoughts on using the Mercury which has the Rolholf and thus a good gear spread and probably a lot more comfortable, even with the steel fork.

My Mercury is set up with long reach road brakes, I currently use 28mm tyres with mudguards , My main issue is would the brakes be powerful enough compared to cantilever for off road riding and would the frame take the knocks associated with off road riding.

The bike is vastly heavier but over 12 plus hours could end up being faster!     

Plus the wheels are really road wheels DT Swiss strong but light road wheels.

[Hubs]

I'd be happy to trying mine, although I'd go for cyclocross tyres. On brakes, my first, 1990's mountain bike had canti's which were ok up to racing speeds.

[jags]

why not take it for a test spin see how bike and pilot fairs out.

[mickeg]

I have never ridden a Mercury or a carbon bike, thus no opinion on those details.

But I can say that when I am out off road where there is rapid changes in grade, I really prefer a Rohloff.  With a derailleur bike, I am trying to keep it straight in my mind when I have to downshift, should it be on the front or rear?  Or both?  But, when I am using the Rohloff, I know that one shift or two or three shifts give me certain reductions in gearing that are predictable and consistent.

And when riding slowly the instantaneous shifting of the Rohloff is nice to have, especially if I have to drop several gears at once.

That is the biggest difference in my mind, but if I was not looking at rapid changes in grade, the advantages of the Rohloff are not as great.  I have been using my Nomad as a mountain bike, that is how I formed my opinions on rapidly changing grades and the Rohloff.

A noticeable disadvantage of the Rohloff is that with my drop bars, I have to take one hand off the bars to shift, thus there are times that I might prefer a derailleur bike.

[jags]

Wow that is one  great photo.

[aggs]

Good point about taking your hands off the bars to shift. I have the drop bar set up too.
Would be hard on a rough road esp downhill.
Thanks for the input.
That has helped me make my mind up and will start setting the cx bike up for the event.

Tried a higher position with a new stem yesterday on the cx bike so could work out ok..  I will experiment more and will have to lower the gearing I think.

Great pic. mickeg  Great bike fit for purpose!!

[Danneaux]

The Gebla Rohbox is a replacement external shift-box for the Rohloff external shifter that will work with modified brifters to shift your hub using the brifters, so no need to remove your hands from the (drop) handlebars.

Shifting action takes place when the internal springs compress enough to pull a toothed gear one way or the other.

Here is the company website: http://www.rohbox.com/

It is available from a growing number of dealers, including SJS Cycles, Thorn's sister company:
Black: http://www.sjscycles.co.uk/gebla-rohbox-shiftbox-black-prod38959/?geoc=us
Silver: http://www.sjscycles.co.uk/gebla-rohbox-shiftbox-silver-prod38958/?geoc=us

Assembly manual here: http://www.sjscycles.com/Instructions/Gebla/Gebla_Rohbox_Shiftbox_Instructions.pdf
Brifter modification manual here: http://rohbox.com/Rohbox%20Technical%20Manuals/ModBrifters.html

Considering the cost of other aftermarket Rohloff shifters, £129.99 is pretty reasonable, though you must also buy briftyers if you do not have them. It works with a variety of brands.

Best,

Dan.

[Joe B]

Hi Dan,

I've not used bifters for a while as I've come to prefer bar end shifters with drop bars but, I am rather intrigued by those Gebla shift boxes. What I don't see however is how a bifter or trigger shifter, which can only shift a maximum of 11 gears will shift all of the 14 we have on our Rohloff's?

[Danneaux]

What I don't see however is how a bifter or trigger shifter...will shift all of the 14 we have on our Rohloff's?

Hi Joe!

It works by sequentially ratcheting from one (or two) shifts to the next gear using the lever ratchet. I other words, it is like any ratchet system that cocks a trigger, then releases. There is no ratchet in the Rohbox.

This works because the return ratchet in the brifter has been modified per the directions linked above.

All the best,

Dan.

[Joe B]

yes, I see now. sorry, I should have looked through the link to the instructions too.

[Danneaux]

No worries. 

The Rohbox works on such a simple concept, it is difficult to grasp at first. Where other aftermarket shifters use internal ratchets and gear trains, the Rohbox uses the warping of a compressed spring to engage and move a gear. It is brilliant in its simplicity, though I have not tried it myself. It looks like a lot of loading will be placed repeatedly on a small section of spring coil. I'm not sure how long it will last, but spring and cable replacements look to be straightforward and easy.

The idea to use an existing brifter was a good one; all the needed ratchet hardware is already present and works readily with slight modification. Of course, the brifters can be restored later if needed for derailleur shifting.

Best,

Dan.

[Mike Ayling]

I would appreciate your views on using a Mercury for a 200km gravel event I have entered in April at Kielder forest , with 3500m of climbing. virtualy all riding is on forest roads.  Gulp!!

I have a carbon cx bike but it really is set up for shorter rides and the longest I have done is 100km with a mix of on and offroad on 35mm tyres, I am currently planning on using this bike, but would appreciate thoughts on using the Mercury which has the Rolholf and thus a good gear spread and probably a lot more comfortable, even with the steel fork.

My Mercury is set up with long reach road brakes, I currently use 28mm tyres with mudguards , My main issue is would the brakes be powerful enough compared to cantilever for off road riding and would the frame take the knocks associated with off road riding.

IMHO any Thorn frame will take a lot of hard knocks.

The bike is vastly heavier but over 12 plus hours could end up being faster!     

Plus the wheels are really road wheels DT Swiss strong but light road wheels.

There is a lot of BS going around about CF forks being more comfortable than steel but the bottom line is down to tyre pressures, if you run these at the lower end of Thorn and the tyre manufacturers specs your ride will be more comfortable than if you are running at higher pressures. Read Thorn's fork reccommendations where AFAICR they rated their very light steel fork at about the same comfort level as CF.

My first tourer had double pivot calipers and when I got a Surly LHT the cantis were no better than what I had been riding.

I endorse what the other blokes have said about the Rohloff particularly at the end of the day when you don't want to think about front change of rear change or both, simply turn the twist grip in the required direction.

IMHO any Thorn frame will take any amount of hard knocks!

I love my Mercury.

Mike

[aggs]

Thanks Mike.

I will train on the cx bike and try the Mercury out on a test run when the weather improves in the spring.

Happy New Year everyone

[aggs]

Update.
I have decided I need 40mm Tyres which I notice in recent training rides float over the loose gravel. Plus are very much more comfortable. This has led me to the decision to strip down my Tourer for the event. With 40mm Tyres it's so much more comfortable and with a good range of gearing. I could not get such large Tyres on the Mercury.
The Club Tour will be returned to Touring Spec for a camping trip to France in the summer. I'm am a bit loath to get it dirty but a cracking 50 mile ride today with approx 30 Miles OK n forest track went really well. The CX bike is just too harsh. Steel is real!

[Relayer]

And when riding slowly the instantaneous shifting of the Rohloff is nice to have, especially if I have to drop several gears at once.

That is the biggest difference in my mind, but if I was not looking at rapid changes in grade, the advantages of the Rohloff are not as great.  I have been using my Nomad as a mountain bike, that is how I formed my opinions on rapidly changing grades and the Rohloff.

Sorry to push pins into the Rohloff bubble again, but I can't help myself.

I never experienced instantaneous shifting with my Rohloff because of the need to back off the power to shift down, which in turn lost me a lot of momentum, which then necessitated more downshifts. 

With derailleurs I can keep the power on and better maintain momentum slowing the drop in speed, meaning fewer and more controlled down shifts; altogether better ... and if you don't have the weight penalty of a load lugger, even better still. 

It is all very well to praise a solution to a problem, but if the solution is a major part of the problem in the first place ...

Jim