shimano rd-4700 actuation ratio

[Brucey]

remember that 2.3mm is an average, and that might include the (longer) first and last pulls. I don't have any accurate measurements for shimano 10s so I can't say for sure what the exact measurements on every shift are, but I can say with some confidence that one way the indexing can 'pull short' is if the housings are of poor quality or are badly prepped; they can then work 'like springs'. Similarly they can also do all manner of weird things if the cables are a bit draggy, too.

cheers

[Mick F]

remember that 2.3mm is an average, and that might include the (longer) first and last pulls.

OK, that makes sense, but if you look at my figures, it still comes out as 2.1mm ish over the full range.

Little Cog = 38.6mm
Big Cog = 19.5mm
Difference/9 = 2.12mm

[student]

Mick, it seems you have a 46 series tiagra.

For improving shifting, I'd generally just recommend the plain sp-41 outers with good quality alloy end caps, and a slippery-stainless steel gear cable. Make sure the housing is adequate length, without sharp bends, acute angles. A friend of mine used to recommend lubing the inners with silicon grease, but later abandoned this practice.

And also, if you have a frame which has the derailleur cables running beneath the bottom bracket on a tiny plastic cable guide, you could also try changing that for a new one (SM-SP18 bottom bracket cable guide) This is a hot-spot, where lot of grime and dust accumulates, and the cable rubbing against the plastic could slice the material a little, thus creating extra friction.

A good decent quality cabling makes a huge improvement. And for sharper-crispier shifts, one can also tweak the rear mech's b-tension screw, letting the upper pulley closer to the cogs.

[matto]

This seems the most appropriate thread to discuss this. Just trying to figure out if the new Tiagra 4700 opens up any new useful shifter derailleur combinations.

As I understand it you can replace the 4700-RD with 11 speed RDs 5800/6800 and it still works, so the 4700 RD uses the same pull ratio (1.4).

I also understand that the 10spd 4700 cassette uses standard 10 speed road cog pitch, i.e. 3.95 mm.

In order for these two to work together the shifter pulls 3.95/1.4 ~=2.8mm

This is the same pull as a 10 speed Campy. Also the same pull as 8 speed Shimano so another option for upgrading 8 speed shifters.

Alternatively using SRAM 10/11 speed exact actuation shifters and the 4700 RD (or other 11 spd RD) should work with a Shimano 9 speed cassette

[markfh]

I had come to a similar conclusion to matto about using the new Tiagra 4700 shifters with an existing 8 speed rear dérailleur. Assuming that the quoted pull ratio's are exact, noting that they are only quoted to a single decimal place (1.7 for 8/9 speed rear dérailleurs and 1.4 for the new 4700 RD) then working back from the sprocket separation of a 10 speed cassette of 3.95 mm gives a cable pull of 3.95/1.40 = 2.82 mm. 2.82 x 1.70 = 4.80 mm (all figures rounded to 2 decimal places) which is the sprocket separation of a Shimano 8 speed cassette.

Based on this I have today taken delivery of some Tiagra 4703 shifters which I Intend trying on a bike with an existing 8 speed Shimano rear cassette (it is currently equipped with Sora 3500 front and rear dérailleurs but as they have the same shift/pull ratio as 8 speed ones it should not invalidate the "experiment"). I have still to get a few more parts that I need to complete the transfer but as soon as I have tried it I will report back in this thread. I had been wanting to try STI shifters on this bike for a while but had wanted to use under tape cable routing so as to not get in the way of using a bar bag. I had considered a shimergo sett up but have a personal preference for Shimano's arrangement of the shift levers over Campag's.

Being somewhat of a cynic and as noted above the calculations are based on pull ratio figures that are only quoted to a single decimal figure I have also bought the corresponding 10 speed front and rear dérailleurs but I will try the ST4703 shifters with the 8 speed set up first. Part of the reason for wanting to try this - apart from idle curiosity - is that the particular bike I will be trying it on whilst having just enough clearance for a 10 speed cassette the chain just fouls the frame on the smallest sprocket so even if I went over to a "full 10 speed" set up I would probably have to use the dérailleur limit screw to block out the smallest sprocket resulting in only 9 gears. I say probably as I tried it with a cassette with a 12 tooth smallest sprocket and it might just work with a cassette with an 11 tooth sprocket but I did not have one to hand to try.

[cycleruk]

Part of the reason for wanting to try this - apart from idle curiosity - is that the particular bike I will be trying it on whilst having just enough clearance for a 10 speed cassette the chain just fouls the frame on the smallest sprocket

I had the same situation on a frame and just fitted a thin washer on the axle - problem solved.

[markfh]

Cycleruk thanks for the suggestion. I will bear it in mind if I want to make use of all sprockets on the rear.

[markfh]

A preliminary update on my experiments with using a Tiagra 4700 shifters (10 speed) with with an 8 speed set up.

So far I have only tried the rear dérailleur but shifting whilst testing on a work stand seems reasonable. I needed to be near the house phone this afternoon so was not able to go for a test ride.

Current set up
Rear shifter = Shimano 4700 10 speed
Front shifter = friction

Front dérailleur Shimano 3503
Rear dérailleur Shimano 3500 GS with over 16,000 km "on the clock" all be it with new jockey wheels approximately 2,500 km ago.

Cassette Shimano 11-28 8 speed
Chain KMC X8-93 8 speed chain

Front shifters set up to use "lowest" 8 positions. All new outers and inner cable to rear dérailleur. The various cables are held to the bars with insulating tape at present, i.e. handlebars NOT taped.

[markfh]

A further update on my experiments with using a Tiagra 4700 shifters (10 speed) with with an 8 speed set up.

When testing last week, although it changed equally well across the whole range of the 8 speed rear dérailleur, it was sometime hesitant to a smaller cog at the rear although generally shifting within one full rotation of the rear wheel. Having realised how many km's I had done with the existing 3500GS rear dérailleur I checked it for slack and found that there was over 1mm side to side of free play when everything was disconnected compared with a new rear dérailleur which had negligible such play. I have therefore swapped the rear dérailleur for a new one and now also connected the existing front dérailleur to the 4703 front shifter.

With the new rear dérailleur the hesitation in shifting to a smaller cog at the rear now seems to have gone and the set-up shifts equally well across the range whilst on the work-stand.

From this it would seem that not only is the cable pull for the 4700 front shifters a good match for a Shimano 8 speed rear dérailleur, but also that the 4703 (triple) shifter is a good match for an 8/9 speed road triple front dérailleur.

Current set up
Rear shifter = Shimano 4700 10 speed
Front shifter = Shimnao 4703 triple

Front dérailleur Shimano 3503 - existing
Rear dérailleur Shimano 3500 GS - new.

Cassette Shimano 11-28 8 speed
Chain KMC X8-93 8 speed chain

Front shifters set up to use "lowest" 8 positions.
All new outers and inner cable to rear dérailleur.
New outer from handlebar to downtube cable stop and new inner for front dérailleur - short outer cable near bottom bracket not yet renewed.
The various cables are held to the bars with insulating tape at present, i.e. handlebars NOT taped.