Double chaninsets for touring- what are the cool kids using?

[Brucey]

translation; 9s MTB derailleur, An LX model...?   

In which case yes I agree that will work, any 9s shimano MTB rear mech will shift OK using your present STIs.

In theory road 9s STIs pull fractionally different amounts of cable than MTB 9s ones in the middle of the cassette, which is (I think) why shimano don't endorse this combination in their compatibility tables (the break in the HG ramping is different in 'road'  and 'MTB' 9s cassettes, and this shifters are different to suit the cassette, rather than the RD). However in practice plenty of people run this setup and they don't have a problem. Until very recently you could still buy an XT 9s mech, new, but they seem to have run out now, so there is a more limited choice of decent 9s MTB mechs.

Anyway if you fit one this should get you to a 36T sprocket....?

Also most compact doubles with 110mm BCD five bolt pattern will accept a 33T inside ring (eg made by TA) although in some cases you may have to file the ends of the spider arms slightly to get enough clearance for the chain.

34/32 is 28.7" and at the same wheel size 33/36 is 24.7", which is a worthwhile reduction in the bottom gear ratio.

cheers

[sojournermike]

translation; 9s MTB derailleur, An LX model...?   

In which case yes I agree that will work, any 9s shimano MTB rear mech will shift OK using your present STIs.

In theory road 9s STIs pull fractionally different amounts of cable than MTB 9s ones in the middle of the cassette, which is (I think) why shimano don't endorse this combination in their compatibility tables (the break in the HG ramping is different in 'road'  and 'MTB' 9s cassettes, and this shifters are different to suit the cassette, rather than the RD). However in practice plenty of people run this setup and they don't have a problem. Until very recently you could still buy an XT 9s mech, new, but they seem to have run out now, so there is a more limited choice of decent 9s MTB mechs.

Anyway if you fit one this should get you to a 36T sprocket....?

Also most compact doubles with 110mm BCD five bolt pattern will accept a 33T inside ring (eg made by TA) although in some cases you may have to file the ends of the spider arms slightly to get enough clearance for the chain.

34/32 is 28.7" and at the same wheel size 33/36 is 24.7", which is a worthwhile reduction in the bottom gear ratio.

cheers

Aargh. Auto spell... yes mtb and I think SLX, although it might be XT. Mines on 10 speed with Ultegra shifters, but I thought the pull ratios were the same until 4700 arrived to confuse matters. Thanks Brucey for clarifying.

[mrcharly-YHT]

Is a GRX going to be compatible with my tiagra shifters? I thought they were 4500 - but that can't be right, as all the tech spec docs for 4500 say they are 9 speed.

https://www.probikekit.co.uk/bicycle-cranksets-and-chainrings/shimano-grx-rx600-double-10-speed-chainset/12649549.html?affil=thggpsad&switchcurrency=GBP&shippingcountry=GB&variation=12649550&&thg_ppc_campaign=71700000077028938&gclid=Cj0KCQiAq7COBhC2ARIsANsPATE85fiwR8ZsgOvQGVL0eZDvwOpJNv-6JnPvyxZO_dYoPFg7WJiWB6EaAoa4EALw_wcB&gclsrc=aw.ds

[mrcharly-YHT]

Reading this: https://www.reddit.com/r/bikewrench/comments/f0fo0v/shimano_rx400_rd_with_older_10spd_levers/
suggests that a GRX derailleur would not be compatible with tiagra older than 4700.

I'm not planning on replacing the rear mech.

So - front 46/30, rear 32...11. Needs 37 capacity, Tiagra is 39.

32 tooth cassettes seem to be like rocking horse poo though.

[grams]

Which parts are you planning to keep/replace?

[Lightning Phil]

32 tooth cassettes seem to be like rocking horse poo though.

Unless 9 speed, in which case readily available 😁

[mrcharly-YHT]

Which parts are you planning to keep/replace?

KEEP
Shifters, front rear derailleur, BB
REPLACE
Crankset, chain, cassette, jockey wheels

[grams]

Which parts are you planning to keep/replace?

[mrcharly-YHT]

Having confirmed that the shifters are tiagra 4600, I've taken the plunge and ordered
GRX chainset
10sp chain
11-32 Cassette
jockey wheels
BB/chainset tool

Spa were the only place I could find the cassette at anything approaching a 'reasonable' price. They warned me that they have a covid staff issue and NY backlog, so it 'might be a while' before they can despatch.

Frightening amount of money for 4 parts.

[ElyDave]

I agree, I've just ordered a 105 front mech and 105 shifter with some gear inners (already have a spare 50-34 chainset), lack of availability and prices both surprised me.

[mrcharly-YHT]

Having confirmed that the shifters are tiagra 4600, I've taken the plunge and ordered
GRX chainset
10sp chain
11-32 Cassette
jockey wheels
BB/chainset tool

Spa were the only place I could find the cassette at anything approaching a 'reasonable' price. They warned me that they have a covid staff issue and NY backlog, so it 'might be a while' before they can despatch.

Frightening amount of money for 4 parts.

Seems I might need to replace front derailleur - GRX crankset has different chainline.

I'll try fitting and see. Need a pedal spanner first.

[MartinC]

Seems I might need to replace front derailleur - GRX crankset has different chainline.

This was my experience when I replaced a Tiagra c'set with a GRX one, the 46mm chainline was just too much for the Tiagra front mech so I had to replace it with an hopelessly overcomplicated GRX one.  You might be lucky, nothing to lose by trying.

[mrcharly-YHT]

Seems I might need to replace front derailleur - GRX crankset has different chainline.

This was my experience when I replaced a Tiagra c'set with a GRX one, the 46mm chainline was just too much for the Tiagra front mech so I had to replace it with an hopelessly overcomplicated GRX one.  You might be lucky, nothing to lose by trying.

It is 2.5mm

Seems so little, I'm tempted to try something like shimming out the derailleur. If I can get it outboard by even 1mm, that might be enough.

In good news, the pedals came off. Step one complete!

[mrcharly-YHT]

Bottom bracket is knackered 

[MartinC]

Seems I might need to replace front derailleur - GRX crankset has different chainline.

This was my experience when I replaced a Tiagra c'set with a GRX one, the 46mm chainline was just too much for the Tiagra front mech so I had to replace it with an hopelessly overcomplicated GRX one.  You might be lucky, nothing to lose by trying.

It is 2.5mm

Seems so little, I'm tempted to try something like shimming out the derailleur. If I can get it outboard by even 1mm, that might be enough....

If I'd known how a GRX FD worked I would've tried that before I bought one.  I probably still will when the GRX mech inevitably seizes up with crud so I'd be interested to know how you get on.  I'd have thought a 34.9 band on an eccentric shim for a 28.6 tube would do the job, depends on what you've got.  A cheap Super Compact chainset (Spa or FSA) on a ST BB will allow you whatever chainline you like.

[Cudzoziemiec]

What's different and "hopelessly overcomplicated" about the GRX front mech compared to others? I don't think I've ever seen one except in photos.

[MartinC]

It's got an extra set of pivots and convoluted cable routing - I believe it's supposed to maintain the cable tension better and make the mech less affected by the angle the cable arrives out now that BB areas can be larger and internal cable ports vary.  Without having one in your hand it's hard to explain.  If you go to techdocs and dig out the installation instructions it'll give you some idea.  I believe 105 and Ultegra are the same too.  The net result is that the mech has more components and more pivots to collect and harbour crud so they can wear and seize and is more fiddly to fit.

[Cudzoziemiec]

Thanks. Sounds like something that needs to be looked at to understand it fully.

[mzjo]

It's got an extra set of pivots and convoluted cable routing - I believe it's supposed to maintain the cable tension better and make the mech less affected by the angle the cable arrives out now that BB areas can be larger and internal cable ports vary.  Without having one in your hand it's hard to explain.  If you go to techdocs and dig out the installation instructions it'll give you some idea.  I believe 105 and Ultegra are the same too.  The net result is that the mech has more components and more pivots to collect and harbour crud so they can wear and seize and is more fiddly to fit.

Now you know the great advantage of a 1x transmission. I was thinking  "why not fit a shorter chainset", thinking in terms of square taper but of course these outboard things have axles that are part of the chainset I suppose so they can't be changed or bodged to order, other than mounting the rings inboard and shimming the little one.

[Andy W]

I replaced my shimano 105 7000 series chainset 50/34, for a shimano GRX 46/30 on my Genesis Croix de fer. I wanted lower gears across both chainrings for both bridleway routes, and for a LEJOG unsupported. One of my better decisions with regard to changing bike components. The tall50/11and12 ratios are IMO hopelessly overgeared for this bikes intended use.
The existing shimano 105 7000 front mech would not work without chainrub at either end of its capacity.  I fitted a grx front mech and shifting was and is clean and reliable. It was marginally more fiddly to fit the cable than earlier iterations of both Shimano and Campagnolo front mech in that the cable is secured in a fairly convoluted way. Shimano recommend pairing both GRX front mech and chainset.

[Andy W]

In response to the above post by MJZO, I'd consider a 1 by system with wide range cassette if not racing and are happy with greater cadence ranges that are inevitable with bigger sprocket gaps. My MTB 12speed XT is flawless in operation but then again it's intended use is a far cry from fast road riding

[mrcharly-YHT]

It's got an extra set of pivots and convoluted cable routing - I believe it's supposed to maintain the cable tension better and make the mech less affected by the angle the cable arrives out now that BB areas can be larger and internal cable ports vary.  Without having one in your hand it's hard to explain.  If you go to techdocs and dig out the installation instructions it'll give you some idea.  I believe 105 and Ultegra are the same too.  The net result is that the mech has more components and more pivots to collect and harbour crud so they can wear and seize and is more fiddly to fit.

Now you know the great advantage of a 1x transmission. I was thinking  "why not fit a shorter chainset", thinking in terms of square taper but of course these outboard things have axles that are part of the chainset I suppose so they can't be changed or bodged to order, other than mounting the rings inboard and shimming the little one.

The rings are already inboard - so there is little that can be done.

I'm going to try to shim out my tiagra front changer.

There is a stupid price difference between grx bracket and band-on derailleurs. Hoping I don't have to replace derailleurs.

Basically I'm doing the same as Andy W, on a CDF.

[ElyDave]

I replaced my shimano 105 7000 series chainset 50/34, for a shimano GRX 46/30 on my Genesis Croix de fer. I wanted lower gears across both chainrings for both bridleway routes, and for a LEJOG unsupported. One of my better decisions with regard to changing bike components. The tall50/11and12 ratios are IMO hopelessly overgeared for this bikes intended use.
The existing shimano 105 7000 front mech would not work without chainrub at either end of its capacity.  I fitted a grx front mech and shifting was and is clean and reliable. It was marginally more fiddly to fit the cable than earlier iterations of both Shimano and Campagnolo front mech in that the cable is secured in a fairly convoluted way. Shimano recommend pairing both GRX front mech and chainset.

Should I be feeling an impending sense of doom? I've just bought a 105 7000 series to fit with a 50/34 front double.
It definitely looks more complicated than the 105 triple that  is on there now.

In response to the above post by MJZO, I'd consider a 1 by system with wide range cassette if not racing and are happy with greater cadence ranges that are inevitable with bigger sprocket gaps. My MTB 12speed XT is flawless in operation but then again it's intended use is a far cry from fast road riding

This is my spec on my Airnimal, 52t up front, 1x11 with a wide range cassette and mtb shifter and derailleur,  with 26" wheels its perfectly geared for audax

[mzjo]

In response to the above post by MJZO, I'd consider a 1 by system with wide range cassette if not racing and are happy with greater cadence ranges that are inevitable with bigger sprocket gaps. My MTB 12speed XT is flawless in operation but then again it's intended use is a far cry from fast road riding

It was not a serious comment about 1x, more a tongue in cheek commentary on how the complexity of the fd was to encourage you to avoid fitting one!

[Andy W]

Fair enough Mjzo. BTW, Ely Dave, the new 105 7000 front mech isn't that difficult to set up. There are some good YouTube tutorials to follow.
I'm still running campag centaur triple with rivendell bar end shifters, front mech stop screws are set so it's nearly impossible to throw the chain. I occasionally manage to do so ascending a steep hill.
The 105 7000  and grx are far better functionally.