Front derailleur capabilities - source?

[LittleGreyCat]

In a discussion about gearing and gear changing strategies I saw several different options for a triple.
So I went looking for some kind of table or specification which said what overall spread and inter-ring spread each derailleur was designed for (and how far you could go outside the design specification).

My searching skills are not up to this; I can find where to buy chain rings, I can find how to fit and adjust front derailleurs, I can find reviews.

However I can't seem to find a simple guide anywhere.

My Spa Wayfarer has a Sora front mech (band on if I am seeing correctly) and the current triple is 48/38/28 which is a 10 tooth difference.
This seems to be standard for a road triple.
However I would like to know the maximum tooth difference I can get away with, and also the biggest big ring and smallest small ring.

Is there a definitive guide anywhere?
I assume that this is the kind of information you would need if you were building up from just a frame.

[NUKe]

the shimano ones are on Shimano.com under technical docs s
or if you just want the answer the capacity is 30 assuming you have the r3030 50t max 20 min
Edit just had time to look yours if the standard is the R3000 capacity 16 teeth largestring 46 to52, i am guessing although the spec says 3000 that it’s a 3030 the triple version

[NetworkMan]

Best is to find a copy of Cycle April/May 2003 and read the article "Beat the System".
Short Summary;
1. Find the spec for your chainset from Shimano site. 50/39/30 for your (and my) Sora 9 speed.
2. Big ring: As spec +-4 teeth. So 46T to 54T.
3. Front difference: As spec. +0T -2T. So 9T to 11T (You have 10T).
4. Small ring. As in my other post. viewtopic.php?f=5&t=133184&start=30

When I get a chance I'll try to explain the reasoning behind all this!

There is, of course, an impact on the capacity of the rear mech..

[Valbrona]

1/ I've tried a 24t on various ROAD triples and the results have been poor. My general rule is to stick with a smallest chainring of 26.

2/ The typically lower-end front derailleurs, eg. Sora, Tiagra, 105, with greater curvature can do a smaller jump between middle and outer chainring than the typically higher end ones, eg. Ultegra, Campag Athena more suited to bigger gaps between middle and outer.

[Norman H]

It might help if you told us exactly what you are hoping to achieve.

On triples it's generally the outer to middle ring tooth differences which are most critical and that's governed by both the depth and the profile of the inner cage. Middle to inner shifts are much more forgiving. Since you already have a 10T difference working OK, a simple fix if you're looking for lower gears would be to change the inner for a 26T or 24T.


The problem when deviating from Shimano's specifications is setting the clearance between the outer cage and the teeth on the big ring. Shimano generally specify a gap of 1-3mm and it's achieved by raising or lowering the changer on the seat tube. This is to enable lifting the chain to produce crisp upshifts whilst at the same time avoiding overshifts and unshipping the chain between the crank and the chainwheel.

If the front mech is specified say for a twelve or thirteen tooth difference in tooth counts then the inner cage will be of a depth and profile to suit. If you try to run it with a lesser tooth difference there's a danger that with the correct clearance set the inner cage will foul the middle ring. If you compensate by raising the mech there's a danger the chain will unship on upshifts or that upshifts will be less than optimal.

There are also other factors to be taken into account. As you reduce the size of the outer ring the curvature of the cage will increasingly not match the curvature of the outer ring. Also as you lower the dérailleur the tail end of the cage risks hitting the chainstay and this is sensitive to chainstay angle. Sometimes you just have to suck it and see.

[PT1029]

Don't forget model designs (esp cage depth) sometimes change over time, so "Sora" capacity may change over time depending on the age/cage design, Thus probably best to search by model number (stamped on the back of the inner cage plate).
Modern Shimano cages are notably deeper than some older ones, which can give ride to the shifting/unshipped chain issues mentioned by Norman H. I use 28-38-48 and use Shimano mechs from the 1990's as they better match the ring sizes I have. I use friction bar end levers which allows some extra fudge/flexibility than STI levers.

[NetworkMan]

As promised, some background to the points in my post upthread.
Norman H has already addressed some of it.

The 2 mm rule.
Changing the size of a chainring by 1T changes the radius by 2 mm (actually more like 2.02 mm). This is useful, for example, when estimating how far you’ll need to move the FD when wondering about changing rings.

Shimano don’t necessarily tell you anything about the preferred chainring sizes in the front derailleur (FD) specification. If this is the case establish it from the description of the chainset supplied with the relevant groupset. I can't really help with Campag. or Sram.

The curve on the cage must closely match the curve on the large ring, with, according to Shimano, a gap of 1 to 3 mm. This becomes hard to achieve with a large alteration in the size of the big ring. If reducing the size of the big ring there is a possibility that the bottom of the FD cage will hit the chainstay. Check using the 2 mm rule above.

As Norman H mentions this is important. If the difference between middle and large ring is smaller than spec. it becomes likely that the inner cage plate will interfere with middle ring and chain. A small reduction may be OK and may even make shifts from middle to small better. If there is interference, raising the FD by 1-2 mm may stop this, but raising it too much will make shifts off the big ring worse or in extreme cases allow the chain to fall off the big ring.

If the difference is too large, the shift from middle to small gets worse, or even impossible when using some sprockets on the back, due to the chain and middle ring being too far below the relevant part of the outer cage plate. This shift is important since it’s the one that you may need to do when under load on a hill that turns out to be steeper than expected. Note that things can’t be made better by moving the FD down since it will then hit the big ring.

The size of the small ring is not very critical and you can often increase front difference by 2T or 4T. If, for example, the designed front difference or capacity is 20T, with a 48T big ring you should be able to fit a 26T or 24T ring. When reducing the little ring size there is a risk that the chain will rub on the bottom of the derailleur cage especially when using the small sprockets on the rear. To check, engage the highest gear you like to use with the proposed little ring and measure between the cage bottom and chain using the 2 mm rule.

[LittleGreyCat]

It might help if you told us exactly what you are hoping to achieve.
<snip>

As in the OP, I am hoping to find some kind of look up table which lists the capabilities of individual components such as front mechs.

So that, for example, if I have a Sora AB-1234 front mech I can quickly check what the capabilities are if I am considering changing my current set up.

Likewise rear mech, brifters, etc. to aid mix and match planning. For example I might consider a different FD or RD as long as it was compatible with the brifters.

I realise that I can ask specific questions on the forum and get helpful specific answers, but I would like to be able to research initial information without relying on others.

I am currently working my way through shimano.com and there is an overwhelming amount of information about individual components on how to fit and service them. However, for example, I haven't yet found a document for a front derailleur which says something like "this FD is designed for a road triple with a maximum chainring of 50 teeth, a minimum chainring of 20 teeth, and a maximum chainring spread of 30 teeth, with chain ring gap between 10 and 12 teeth".

I assume that there must be a higher level of documentation which helps you to decide which components you are going to use in your build (assuming that you don't just order the whole combined groupset). That is, if you decide that you want a 28/38/48 front triple then you can look up which components support this.

I keep looking at the specification of my Wayfarer and it has Shimano Sora 9spd STI brake levers, front derailleur Shimano Sora, rear derailleur Shimano Deore. So Spa have mixed and matched some components.

As an aside I find it mildly frustrating that the minor variations in components with nominally the same name seem to require detailed investigation instead of having the details shown on the outside of the components and the detailed part number niftily embedded somewhere down amongst the hidden bits.

[slowster]

I am currently working my way through shimano.com and there is an overwhelming amount of information about individual components on how to fit and service them. However, for example, I haven't yet found a document for a front derailleur which says something like "this FD is designed for a road triple with a maximum chainring of 50 teeth, a minimum chainring of 20 teeth, and a maximum chainring spread of 30 teeth, with chain ring gap between 10 and 12 teeth".

First Google result for "Shimano Sora FD-R3030" is the Shimano website, which gives that information:

https://bike.shimano.com/en-EU/product/component/sora-r3000/FD-R3030-F.html

As for mixing amd matching, Shimano want you to use components from the same groupset, and are not interested in supporting mixing and matching other than to a limited extent, e.g. using a higher spec mech like Ultegra with 105 shifters or vice versa. They are certainly not interested in telling people whether MTB and road gear parts are compatible, still less whether another brand's component will work with their's.

So the only way you will find that sort of information out is by asking questions, ideally after you've tried googling for an answer and/or searching this forum (tip - this forum's search function is not good for seeing if a question has been asked before, because it throws up all posts with just one of the search words in it - it's better to search the forum using Google by adding "site:https://forum.cyclinguk.org" to your Google search terms).

[NetworkMan]

Just to underline the point about advertised compatibility or lack of it.
You can look at the Shimano "Compatability Chart"
https://productinfo.shimano.com/#/com?c ... acid=C-455
.. If you look for 'drivetrain for road' -> 'front drivetrain compatibility' -> '3 x 9 speed'
.... you'll see in the FD column the Sora FD-R3030 front dérailleur.
You'll also see in that in the FC column only one chainset is compatible, the FC-R3030 which has rings of 50/39/30 with no options.

It's all very sad but it's been like this for years and years and we just have to live with it

[LittleGreyCat]

I am currently working my way through shimano.com and there is an overwhelming amount of information about individual components on how to fit and service them. However, for example, I haven't yet found a document for a front derailleur which says something like "this FD is designed for a road triple with a maximum chainring of 50 teeth, a minimum chainring of 20 teeth, and a maximum chainring spread of 30 teeth, with chain ring gap between 10 and 12 teeth".

First Google result for "Shimano Sora FD-R3030" is the Shimano website, which gives that information:

https://bike.shimano.com/en-EU/product/component/sora-r3000/FD-R3030-F.html

As for mixing amd matching, Shimano want you to use components from the same groupset, and are not interested in supporting mixing and matching other than to a limited extent, e.g. using a higher spec mech like Ultegra with 105 shifters or vice versa. They are certainly not interested in telling people whether MTB and road gear parts are compatible, still less whether another brand's component will work with their's.

So the only way you will find that sort of information out is by asking questions, ideally after you've tried googling for an answer and/or searching this forum (tip - this forum's search function is not good for seeing if a question has been asked before, because it throws up all posts with just one of the search words in it - it's better to search the forum using Google by adding "site:https://forum.cyclinguk.org" to your Google search terms).

I went to the web page linked, and saw:

"The SHIMANO SORA R3030 front derailleur is compatible with wide ratio, 3x9 speed gear combinations."

That's about it.
No mention of tooth counts, maximum, minimum or gap.

[LittleGreyCat]

Just to underline the point about advertised compatibility or lack of it.
You can look at the Shimano "Compatability Chart"
https://productinfo.shimano.com/#/com?c ... acid=C-455
.. If you look for 'drivetrain for road' -> 'front drivetrain compatibility' -> '3 x 9 speed'
.... you'll see in the FD column the Sora FD-R3030 front dérailleur.
You'll also see in that in the FC column only one chainset is compatible, the FC-R3030 which has rings of 50/39/30 with no options.

It's all very sad but it's been like this for years and years and we just have to live with it

Well, yes.
The chart didn't even show the details of the FC-3030 but Google found it, as you say.
I would probably have foundered before the last step because I was looking for a "tooth" word.

So as far as I can tell there is no obvious published source of this information, but you have to "ask someone who already knows".

It is obvious that the FD can support a 48/38/28 because that is what the Wayferer comes with.
I suspect that it will support a 10 tooth gap with lower sizes all through (but don't know).

As advised, swapping in a 24 tooth lower ring would be worth trying.

I'll just have to keep on forum bothering.

[slowster]

I went to the web page linked, and saw:

"The SHIMANO SORA R3030 front derailleur is compatible with wide ratio, 3x9 speed gear combinations."

That's about it.
No mention of tooth counts, maximum, minimum or gap.

Scroll down to the section headed "PRODUCT SPECIFICATIONS". At the bottom before the next section ("SERIES LINE-UP") is a downward pointing arrow. Click on the arrow.

[Sum]

I went to the web page linked, and saw:

"The SHIMANO SORA R3030 front derailleur is compatible with wide ratio, 3x9 speed gear combinations."

That's about it.
No mention of tooth counts, maximum, minimum or gap.

You have to click on the little down arrow to expand the table:-

MODEL NO FD-R3030-F
SERIES SHIMANO SORA R3000 Series
Color Series color
Action_Down Swing ✔
Action Down Swing
Angled clamp band design ✔
Applicable Top-Mid tooth difference 11T
Chain line (mm) 45
Chain stay angle 63 - 66
Mount_Brazed-On ✔
Mount Brazed-On
Speeds_Front 3
Speeds_Rear 9
Top gear teeth 50T
Total capacity 20T

[LittleGreyCat]

I went to the web page linked, and saw:

"The SHIMANO SORA R3030 front derailleur is compatible with wide ratio, 3x9 speed gear combinations."

That's about it.
No mention of tooth counts, maximum, minimum or gap.

Scroll down to the section headed "PRODUCT SPECIFICATIONS". At the bottom before the next section ("SERIES LINE-UP") is a downward pointing arrow. Click on the arrow.

Ah.

Artfully concealed.