Cycling UK Forum

hello.

as i know, shimano 11speed road derailleurs have 1.4 actuation ratio, just like old, 20th century campag.

tiagra pretty much got the same design, so, increased cable travel and decreased actuation ratio

http://blog.artscyclery.com/science-beh ... atibility/

if i'm correct, a campag 10 speed shifter would be able to operate a tiagra derailleur (4700, which has the same design as 11 speed road) on a 10speed shim cassette.

2,8*1,4=3.92, pretty close to the spacing of 10speed shimano.

the reason I'm asking, i have shimano compatible wheels and have some 10 speed ergopowers as well, and for summer trips, mountainous passes, a long cage tiagra with a 32t top cog would be much more price sensible choice as compared to campag cassettes and derailleurs.

What would be the consensus? is there anyone, who can confirm, that the actuation ratio of the rd-4700 is indeed 1.4? by looking at the rd design (pivot points and cable attachement) id assume, that it is indeed.

cheers and thanks for the comments.

no, RD-7400 is nowhere near 1.4, it is more like 1.9

For reference, the pull ratio is such that (using a shimano 9s shifter) RD 7400 will index nicely on 8s.

You can find all this out here

http://www.ctc.org.uk/cyclists-library/components/transmission-gears/derailleur-gears/shimergo

and here

https://en.wikibooks.org/wiki/Bicycles/Maintenance_and_Repair/Gear-changing_Dimensions

BTW
Shimano road 11 is ~1.65 and
Shimano MTB 11s (dynasys) is ~1.25 shift ratio.
[edit: the above numbers are wrong, sorry. Recordacefromnew has a good point but there is no explanation other than 'brain fart' in this case. The correct numbers are 1.385 and 1.055 respectively.]

cheers

rd-4700 is 10 speed road (http://bike.shimano.com/content/sac-bike/en/home/components11/road/Tiagra4700/rd-4700-gs.html), so actuation (traverse / cable pull) is 1.7 as specified in Brucey's ctc link.

If you have a 10 speed Campag shifter as you say, it will index fine with an 8 speed Shimano cassette with conventional cable attachment, or 9 speed Shimano cassette if hubbub.

Brucey must have had a good Sunday lunch...

nope. rd4700 is not old-10 speed (SIS) compatible, the shifters don' use the short cable pull, in fact, they pull a lot more. The RD is designed the same way as 5800, 6800, both of which has 1.4 actuation ratio (11 speed shimano cable pull is approx. 2.7mm)

but just looking at the design, it is clear that the cable attachement point relative to the pivot points is moved further than it was with former sh derailleurs.

That is why I assumed that rd4700 also has 1.4 actuation ratio.

well, i guess the only way to figure it out is to buy one, and try it..

http://blog.artscyclery.com/science-beh ... atibility/

http://answers.chainreactioncycles.com/ ... stions.htm

http://www.bikerumor.com/2015/03/31/all ... nd-groups/

also, is someone runs an old 9speed campagnolo shifter and drivetrain with pre2001 cable pull&actuation ratio, now can just simply replace a wobbly rd with tiagra, and opt for wider ranges of gears.

a collegue of mine suggested trying it out, as it is clear that the new rd-s are designed for longer cable pullz.

http://www.bikeforums.net/bicycle-mecha ... st18408796

sorry, you are quite right, it does look close to 1.4 shift ratio, like 11s (had a brain fart before...or something!).

The compatibility charts eg here;

http://www.celebrazio.net/bicycling/shimano/2016_compatibility.html

indicate that ST4700/ST4703 should only be used with RD4700 mechs, so no big clues there....

Like you say it is probably best to buy one and try it. If the shift ratio is slightly different from what you expect, you can presumably adjust it with a little tweak of some kind.

Now I'm sure that this kind of stuff is about as interesting as watching paint dry to most folk, but here's a thing; if the shift ratio is indeed 1.4 then this means the shifters have 2.8mm/click or thereabouts. If so this means that (as well as 9s campag users) shimano 8s users may now have the option for different parts (ST470X shifters, with underbar cable routing, on 8s)

However if using a campag shifter with the shimano rear mech it might work just fine but in the past there have been subtle differences in cable pull vs rear mech geometry between shimano and campag that may result in slightly less accurate shifts over the full range. However even that could be different now.

Apologies for earlier confusion!

cheers

My Moulton TSR30 has Tiagra stuff and STIs.
I don't like the STIs, though I am getting used to them.
My Mercian has Campag Ergo 10sp though I'm not about to swap them over to check ......................

I wonder though, that I could mount the bikes side-by-side with the Moulton on the workstand, and lace the Mercian RH Ergo to the Moulton Taigra rear mech. I could turn the Moulton cranks and see how the Mercian Ergo handles the cog changes.

Something to do some other time, but it would be an interesting experiment.

Mick,
a fairly easy test would be to measure the 'bare cable gap' in the Tiagra 4700 rear mech, both in top gear and bottom gear. Whilst this might be subject to errors of ~0.5mm or so, it'd confirm the cable pull per click to within ~0.1mm or thereabouts...? Maybe the measurement would be more accurate if it were taken between gear #2 and gear #9....?

-just a thought...

cheers

you can see the difference in design in these pictures;

RD-4700 (10s) (with 'revised shift ratio')


RD-4600 (10s) (with original 6-10s (road) shift ratio)


RD-5800 (11s, with 1.4 shift ratio)


cheers

also the fd-4700 front mech shift ratio is 'quite a bit different' too



that is the longest arm I have ever seen on a front mech!

Wheras the FD-4703 triple mech looks much more 'normal' to me



-but is still indicated as being unique in the shimano compatibility charts...

cheers

thank you.

i must admit, the long arm front derailleurs made an improvement in shifting at the front, and also, with these new, revised rear shifters, the system is not that sensible to cable stretch and grime.

The stuff just works very good. Even though, the older ten speed shifters with non-concealed cables were very smooth as well

thanks everyone for the responses, and esp. Brucey with the explanation with pictures.

cheers.

Just got back from a ride.

................ been thinking ............

What about taking the rear wheel and rear mech off Mercian and the same off Moulton, then fitting the Moulton rear wheel and rear mech onto Mercian?
Obviously can't ride it like that!
However, it should show if the Ergo will shift the Tiagra rear mech adequately whilst on a stand.
Maybe have a go at that if I'm bored one day.

Meanwhile, I'll check the spare cable, as that's easy.

Back soon!

Here's my results.
Using my trusty (analogue) vernier calipers and my tired old eyes. Moulton on the workstand.

Big cog is Cog 10
Little cog is Cog 1

Spare cable measurements:
Cog 1 = 38.6mm
Cog 2 = 36.4mm
Cog 9 = 22.5mm
Cog 10 = 19.5mm

Make of that what you will!
I'm going for some lunch.

Brucey,
My rear mech is like the top one.
You have it as a RD-4700.
Except the logo is like the bottom one. Also the front parallelogram plate is shiny like the bottom one.

The instruction sheets I got with my Moulton are for 4600 but I don't have one for the rear mech.

I have not checked the measurements you have kindly provided but I think you have a RD-4600-GS mech there, like this one



If so it ought to be ~2.3mm per click, like all other Shimano road 10s mechs (apart from 4700, it seems...)

cheers

Thanks!
That looks like it.

I've since checked and re-checked the figures, but they come to me to nearer 2mm per click than 2.3mm.
Did it a few times Cog 2 to Cog 9 and came out on average 2.17mm.

Now, here's a point.
I'm complaining that the rear gear selection isn't quite right.
If my rear mech is out by circa 0.3mm per click, it means it's out circa 2.7mm from end to end.