Gearing again

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molzor
Posts: 113
Joined: 21 Dec 2014, 12:34pm

Re: Gearing again

Postby molzor » 26 Aug 2018, 8:02pm

Brucey wrote:all else being equal shifting force will also be increased if you move from ramped/pinned rings to some with fewer ramps/pins etc. is this the case? (there are different chainring options on chainsets from spa)

Also, is the shifter/cable old, poorly lubricated, or badly routed (esp via a BB guide)?

cheers


There does seem to be few ramps/pins on the new chainset. the old tiagra chainset has a mountainous surface!

The cable is new, so is the outer. I will check out the bottom bracket guiding tomorrow. Make sure it's ok.

molzor
Posts: 113
Joined: 21 Dec 2014, 12:34pm

Re: Gearing again

Postby molzor » 26 Aug 2018, 8:09pm

slowster wrote:Is the stiffness only felt when the cage comes into contact with the chain and presses against it, or is it felt before then?

You haven't by any chance re-attached the cable to the front derailleur on the other side of the pinch bolt?


The stiffness is almost certainly just because I am forced to over tension the cable to make the mech stretch far enough. I have just checked the bolt, and I am on the correct side.

molzor
Posts: 113
Joined: 21 Dec 2014, 12:34pm

Re: Gearing again

Postby molzor » 26 Aug 2018, 8:25pm

Brucey wrote:read teh model numebr and double-check what the chainring interval is meant to be with your mech. Compare with the interval you are using and act accordingly.

Note also that the FD is meant to be used with the chain entering it at within a certain range of angles; toe in or toe out can alter the angle one way and the included angle between the chainstay and seat tube (as well as variations in cassette and chainring sprocket sizes) alter it in the other. Both can affect front shifting.

cheers


I cant seem to find any information for one which looks like my front mech, but I was sure it was the 4703...I bought the groupset and everything else looks like the 4703.

I dont know... Thanks for the help everyone, but I'm giving up on it for today. I will hassle you all again soon.

NetworkMan
Posts: 700
Joined: 25 Aug 2014, 11:13am
Location: South Devon

Re: Gearing again

Postby NetworkMan » 27 Aug 2018, 12:21pm

I had a look around on the web and it does look as if there are two variants of 4703 and molzor's looks like the older. It looks as if the newer one has that option to tweak the pull ratio that was raised on some other post not long ago. I think that they are both designed for 63-66 mm chainstay angle and 50-39-30 rings.
A couple of points. Molzor's interval in 10T not (edit 11T, see below) but I'd have thought that was too small a difference to matter too much - perhaps raise the cage a little (2-2.5 mm) after it's been lowered to match the smaller big ring.
Does anybody recall anyone doing this modification with a 10 speed system - mine is 9 speed, so is Spa's tourer. All Spa's 10 speed bikes have standard Shimano transmission I think.
Slowster, is your super-compact double 10 speed? Do you use a triple FD - so it's essentially a triple with a missing big ring and a different BB to tweak the chainline

My understanding is that Molzor is having to do this because this Tiagra group has a different RD pull ratio that makes it impossible to fit a mountain bike RD and a big sprocket. Is that correct?
Edit
Actually now not sure if the newer FD does offer the ability to change pull ratio - not important here anyway I suspect.
Last edited by NetworkMan on 10 Sep 2018, 10:32am, edited 1 time in total.

Brucey
Posts: 35610
Joined: 4 Jan 2012, 6:25pm

Re: Gearing again

Postby Brucey » 27 Aug 2018, 12:53pm

molzor wrote:
I cant seem to find any information for one which looks like my front mech, but I was sure it was the 4703...I bought the groupset and everything else looks like the 4703.

.


the model number is written on the back of the mech. Just read it off.

I think that both versions of FC-4703 have the same pull ratio, are designed to work with the same shifters and the same chainset.

This FD is designed to work with an 11T middle to big ring interval. This means if it is set to a normal height above the big ring, and you are using a 9t interval, it won't work, simple as that. Probably you will be able to see the cage clouting the middle ring.

For this FD to work with a 9T interval the FD will have to be set at about 4mm higher than normal, i.e. to clear 5-6mm above the big ring instead of 1-2mm as per the normal recommendation. IME this is high enough that the chain will be at some risk of unshipping off the big ring occasionally.

As per a previous post, if the chainline is wrong (wrong length BB spindle fitted) then this will stop the FD from working too.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

slowster
Posts: 943
Joined: 7 Jul 2017, 10:37am

Re: Gearing again

Postby slowster » 27 Aug 2018, 1:14pm

NetworkMan wrote:Slowster, is your super-compact double 10 speed? Do you use a triple FD - so it's essentially a triple with a missing big ring and a different BB to tweak the chainline.

It's 10 speed with a CX70 front derailleur. Mine was a 2 x 10 set up to begin with, and I had to fit the CX70 because the original Microshift FD could not be lowered sufficiently to work with the smaller rings of the Super Compact double without fouling on the chainstay.

NetworkMan
Posts: 700
Joined: 25 Aug 2014, 11:13am
Location: South Devon

Re: Gearing again

Postby NetworkMan » 27 Aug 2018, 4:04pm

Brucey wrote:
molzor wrote:
I cant seem to find any information for one which looks like my front mech, but I was sure it was the 4703...I bought the groupset and everything else looks like the 4703.

.


the model number is written on the back of the mech. Just read it off.

I think that both versions of FC-4703 have the same pull ratio, are designed to work with the same shifters and the same chainset.

This FD is designed to work with an 11T middle to big ring interval. This means if it is set to a normal height above the big ring, and you are using a 9t interval, it won't work, simple as that. Probably you will be able to see the cage clouting the middle ring.

For this FD to work with a 9T interval the FD will have to be set at about 4mm higher than normal, i.e. to clear 5-6mm above the big ring instead of 1-2mm as per the normal recommendation. IME this is high enough that the chain will be at some risk of unshipping off the big ring occasionally.

As per a previous post, if the chainline is wrong (wrong length BB spindle fitted) then this will stop the FD from working too.

cheers

Yes, 50-39 is 11T not 9T my error OP now has 10T. I think we agree in principle.
I reasoned as follows Drop FD to just clear big ring perhaps 1-3 mm away. Now need to allow for the middle ring being 1T larger (smaller difference) so raise the cage by 2+ mm since 1T at circumference equates to 12.7/(2*pi) or 2.02 mm change in radius. Spa do this with the 9 speed tourer, and they sell loads I imagine, using a 50-39-30 Sora FD but they supply 48-38-28 by default and OP has smaller rings (46-36-26). Just how much this matters I don't know.
Years ago CJ wrote that a 4T reduction in rings was OK. He also wrote "Never exceed the specified difference, or else middle-inner shifts will suffer. You can generally reduce middle-outer difference by a couple of teeth............. " Beat the system, Cycle April/May 2003.
Last edited by NetworkMan on 27 Aug 2018, 4:18pm, edited 1 time in total.

NetworkMan
Posts: 700
Joined: 25 Aug 2014, 11:13am
Location: South Devon

Re: Gearing again

Postby NetworkMan » 27 Aug 2018, 4:13pm

slowster wrote:
NetworkMan wrote:Slowster, is your super-compact double 10 speed? Do you use a triple FD - so it's essentially a triple with a missing big ring and a different BB to tweak the chainline.

It's 10 speed with a CX70 front derailleur. Mine was a 2 x 10 set up to begin with, and I had to fit the CX70 because the original Microshift FD could not be lowered sufficiently to work with the smaller rings of the Super Compact double without fouling on the chainstay.

Oh, I see. Just wondered if their were any clues to OP's problem. You are probably better off with the CX70 since the cage is a more simple shape and you don't need triple shifting.

Brucey
Posts: 35610
Joined: 4 Jan 2012, 6:25pm

Re: Gearing again

Postby Brucey » 27 Aug 2018, 4:24pm

note that if the chainline is too wide, at least three things happen;

1) the FD may not reach to the big ring at all

2) the FD may not reach to the big ring when using an indexed shifter; the shift ratio changes through the stoke such that the wider you go, the more cable pull you need for less and less actual lateral FD movement

3) the FD movement alters; because the parts swing around a radius described by the linkage, there is more vertical movement in the FD cage and less lateral movement. This can affect the 'correct' height for the FD.

The last of these means that the 'correct' clearance to the big ring may not be enough, even if the middle-to-big interval is about right, and you may need to sit FD further above the big ring in order to avoid a clash with the middle ring.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

NetworkMan
Posts: 700
Joined: 25 Aug 2014, 11:13am
Location: South Devon

Re: Gearing again

Postby NetworkMan » 27 Aug 2018, 4:42pm

Brucey wrote:note that if the chainline is too wide, at least three things happen;

1) the FD may not reach to the big ring at all

2) the FD may not reach to the big ring when using an indexed shifter; the shift ratio changes through the stoke such that the wider you go, the more cable pull you need for less and less actual lateral FD movement

3) the FD movement alters; because the parts swing around a radius described by the linkage, there is more vertical movement in the FD cage and less lateral movement. This can affect the 'correct' height for the FD.

The last of these means that the 'correct' clearance to the big ring may not be enough, even if the middle-to-big interval is about right, and you may need to sit FD further above the big ring in order to avoid a clash with the middle ring.

cheers

Yes but upthread OP says that he'd made an error and chainline is indeed 45 mm as it should be since he has same chainset and nominal BB as me - just smaller rings.
Edit:
This is all rather a mystery - it's not even clear to me if the increased resistance occurs before or after the FD contacts the chain.

Brucey
Posts: 35610
Joined: 4 Jan 2012, 6:25pm

Re: Gearing again

Postby Brucey » 27 Aug 2018, 6:12pm

the other thing that might be happening is that the chainline is too far the other way. This will tend to make the shifting force get higher than normal on the small to middle shift.

FWIW shimano triple 'road' mechs have a shorter cable pull per shift than most other FDs, and require a slightly higher shift force than most. FD-4703 uses (I think) the same shift ratio as older shimano road triple mechs, whereas FD-4700 (the double mech) shares a shift ratio with the current 11s FDs.

There may well be something making it worse than normal (like a badly lubed or badly prepped cable) but the shift force is a bit higher than it would be for a double anyway.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

molzor
Posts: 113
Joined: 21 Dec 2014, 12:34pm

Re: Gearing again

Postby molzor » 28 Aug 2018, 3:00pm

The mech is definitely a 4703, but apparently there are two versions of this.

I have checked all the routing, cleaned, regreased. new outer cable. everything.
I guess, the problem really is that it will not shift up, particularly to the big ring.

I can make it shift up, but this means using a tonne of cable tension, which in turn makes it very stiff and just isnt useable.

I have tried various heights trying to experiment with the channeling on the mech but I suspect it is quite simply best suited to a 30/39/50 chainset.
I notice the old chainset also has a very rough/bumpy inner surface on the chainrings, which the new spa one does not. I suspect this aids the jump.

Ross K
Posts: 39
Joined: 25 Oct 2013, 8:14pm

Re: Gearing again

Postby Ross K » 28 Aug 2018, 3:01pm

I recently went from a compact (50-34) to a lower-gear set up (44-30) for a cost of £25.

1. Take a 5703 triple crankset.
2. Remove the 50 and 39 rings.
3. Replace the middle ring with a TA 44T 130BCD, using single chainring bolts.
4. Move front derailleur down a bit.
5. Fiddle about with cable tension and limit adjusters.

The result is surprisingly good considering the new mid ring has neither ramps nor pins.

I'm a reasonably strong rider/TT-ist living in a hilly area and the new gearing of 44-30 with 11-25 is much better than a compact, for me personally. Great chainlines on my most used gears and virtually no front changes, with a lovely set of close ratio climbing gears via the Granny ring. I was motivated to do it because I'm entering the Fred Whitton again and wanted to avoid putting on one of those dinner-plate sized cassettes.

While still retaining my standard short cage rear mech, I also have the option of putting a 28 front ring on with an 11-28 cassette for a Hardknott-bashing 1:1 ratio! Top gear on 44-11 is equivalent to approximately 50-12.5.

I see they're marketing the "new big thing" (ie old thing) of a "supercompact" for lots of ££££ (Sugino, FSA, Praxxis) but as always there's usually a perfectly good alternative for much less cash. SPA cycles do their version (a triple with the outer ring removed) but it's square taper and far heavier.

The side bonus of my new set up is that the chainset in its reduced form is the same weight as an Ultegra double, 715g. Win win!
Last edited by Ross K on 28 Aug 2018, 3:54pm, edited 1 time in total.

molzor
Posts: 113
Joined: 21 Dec 2014, 12:34pm

Re: Gearing again

Postby molzor » 28 Aug 2018, 3:15pm

Ross K wrote:I recently went from a compact (50-34) to a lower-gear set up (44-30) for a cost of £25.

1. Take a 5703 triple crankset.
2. Remove the 50 and 39 rings.
3. Replace the middle ring with a TA 44T 130BCD, using single chainring bolts.
4. Move front derailleur down a bit.
5. Fiddle about with cable tension and limit adjusters.

The result is surprisingly good considering the new mid ring has neither ramps nor pins.

I'm a reasonably strong rider/TT-ist living in a hilly area and the new gearing of 44-30 with 11-25 is much better than a compact, for me personally. Great chainlines on my most used gears and virtually no front changes, with a lovely set of close ratio climbing gears via the Granny ring. I was motivated to do it because I'm entering the Fred Whitton again and wanted to avoid putting on one of those dinner-plate sized cassettes.

While still retaining my standard short cage rear mech, I also have the option of putting a 28 front ring on with an 11-28 cassette for a Hardknott-bashing 1:1 ratio! Top gear on 44-11 is equivalent to approximately 50-12.5.

I see they're marketing the "new big thing" (ie old thing) of a "supercompact" for lots of ££££ (Sugino, FSA, Praxxis) but as always there's usually a perfectly good alternative for much less cash. SPA cycles do their version (a triple with the outer ring removed) but it's square taper and far heavier.

The side bonus of my new set up is that the chainset in its reduced form is the same weight as an Ultegra triple, 715g. Win win!



Glad to hear someones chainring ventures are going well. Im thinking about giving up and putting the old chainset back on. I would survive with a 30T but it would just make life a lot easier to have less. I dont know why they are stocking "round the world" tour de fer bikes with this gearing.

Brucey
Posts: 35610
Joined: 4 Jan 2012, 6:25pm

Re: Gearing again

Postby Brucey » 28 Aug 2018, 4:25pm

molzor wrote: ...... I dont know why they are stocking "round the world" tour de fer bikes with this gearing.....


because shimano don't make a suitable product that gives you low gears on a road bike. It is as if they have a corporate blind spot.

In fact things have been getting worse, in that their 'road triple' chainsets used to be able to take a much smaller chainring (even if they came with a 30T attached) but now they don't....

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~