Super Compact chain set for touring?

[T4tomo]

if you swap to GRX stuff you need to change the FD. if you change to 40T max cassette you likely need a new RD or a wolf tooth.

if you swap to Spa subcompact double, you likely need a new BB as I believe they are all square taper (unless your current bike is a ST BB) but the chainline & FD will still be good.

a single chain ring the worst idea

 

[AlanW]

It was @StuAff that first alerted me to the fact that you would need to replace the front mech, something that I had not even considered to be honest.

However, I then "Googled" running a GRX chain set with a std front mech and while I appreciate using GRX FD is the best option, a number of people have quite successfully done it with no issues. It also helps that my FD is a band-on type as the only real issues appear to be with the braze-on type.

My current rear derailer will allow up to a 39T max, but again, searching the internet folk are running a 40T with my RD type with no issues, but adding a wolftooth wouldn't be a bad idea

 

[roubaixtuesday]

No way would I go for a single chain ring but fitting a 11-40 cassette with my current 34/50 chain set might be worth exploring as a cheaper option.

Not quite what I'm used to with regards to the big steps in ratios, but it's certainly a much cheaper option for the odd weekend away. This would give me 22.4" bottom gear compared to 26.4" with the 11/34 I'm using now.

With a GRX 30/46 chain set and the 11/34 cassette, which would give me 23.3" bottom gear. But the cost to change is going to be circa £200, vs around £75 for the 11-40 cassette.

Certainly, a less hassle just swopping the cassette over, if I can live with the big steps in the larger capacity cassette. I might ask some of my cycling friends if anyone has one that I can borrow for a test ride before I take the plunge.

An 11-40 cassette is very unlikely to work directly on your current set up.

You'll likely need a new rear derailleur, and a new chain.

You need to check two things on the derailleur spec:

(1) largest sprocket
(2) total capacity

Capacity required for your suggestion is (50-34) + (40-11) = 45

Current Ultegra 11 speed, just for instance, has max sprocket 34, and capacity 39.

https://bike.shimano.com/en-EU/product/component/ultegra-r8000/RD-R8000-GS.html

Often it's possible to go a little beyond nominal specs, but I doubt you'd get away with that.

There is one golden rule when doing this: always, always check the bike will run in big/ big on the stand before riding. If the chain is too short, and you accidentally use that gear, you'll tear the whole thing apart.

 

[AlanW]

Capacity required for your suggestion is (50-34) + (40-11) = 45

Current Ultegra 11 speed, just for instance, has max sprocket 34, and capacity 39.

My bad, I was speed reading the forum that was discussing the options and I took it that 39 was the max sprocket size as opposed to the max capacity ......doh!

I have a longer chain by two links that I fit when I use the 11/34 cassette, compared with the everyday chain/cassette ratio of 11/28

So worse case, it's a different RD to use with the 11/40, which again is cheaper that replacing the chain set I suppose. I assume I would need to go with a MTB style RD?

 

[roubaixtuesday]

I assume I would need to go with a MTB style RD?

Not sure, sorry. Is cable pull the same on mtb? Or do you need to use a "gravel" rd? I'd recommend to check cable pull as well as max sprocket and capacity.

 

[AlanW]

Not sure, sorry. Is cable pull the same on mtb? Or do you need to use a "gravel" rd? I'd recommend to check cable pull as well as max sprocket and capacity.

Just looking at that now, it seems that Ultegra shifters dont play to nicely with an XT RD

 

[T4tomo]

Just looking at that now, it seems that Ultegra shifters dont play to nicely with an XT RD

No not at 11 speed. Up to 10 speed life was grand and road and MTB shimano played with each other nicely (baring 4700 tiagra which has 11 pull ratios but is 10 speed) You need GRX to gte large sprockets with road shifters, but the GRX RD whilst having a max 42T sprocket capability, has a lower 31 T capacity (its aimed at 1x systems).

The other option is a Jtek shiftmate and a MTB RD. Have a search for @rivers thread on Mullet drivetrain for more details.

I still reckon a sub compact chainset will be your easiest & cheapest conversion, provided you have a threaded bottom bracket, and wont leave your with any suboptimal shifting set ups. A 30-34 lowest gear should be suitable given you're not hauling tents and camping gear around and cassettes up to 34T are a lot cheaper than their 40/42T counterparts

 

[roubaixtuesday]

Just looking at that now, it seems that Ultegra shifters dont play to nicely with an XT RD

There's a compatibility chart here

https://productinfo.shimano.com/#/com?acid=C-454&cid=C-453

A quick glance doesn't show up anything that suits, assuming you're on 11 speed, but I've not checked carefully. Not sure about cross compatibility with other brands.

You can fit a hanger extender (wolftooth is a well known brand) which allows a bigger rear sprocket. I've use that to get from 32 to 36, I would guess it would probably allow you to get from 34 to 40, but it doesn't address the capacity issue, so you get chain slap in little/little combinations. That's not a big problem, so might be your best "quick and dirty" option.

If you want to explore the chainset option, a useful thread here

https://forum.cyclinguk.org/viewtopic.php?t=153478

 

[AlanW]

Thanks all for the replying, your observations and some great suggestions, as is usually the case when I start to go of what is considered to be the norm, its not going to be as easy or as straight forward as I first thought....dam it

 

[AlanW]

I still reckon a sub compact chainset will be your easiest & cheapest conversion, provided you have a threaded bottom bracket, and wont leave your with any suboptimal shifting set ups. A 30-34 lowest gear should be suitable given you're not hauling tents and camping gear around and cassettes up to 34T are a lot cheaper than their 40/42T counterparts

I think you are right @T4tomo, fit a GRX 30/46 chain set and see how it functions with the Ultegra FD, and the 11 speed 11/34 cassette. Worse case I may have to replace the FD for a GRX one. If I cannot get up a climb with a 23.3" gear, then I'll just walk......

 

[T4tomo]

also consider a Miche Graff sub compact - that wont have the chainline issue of a GRX, maybe cheaper and is Hoillowtech II type.
You will need to check you BB type for compatibility.

 

[AlanW]

also consider a Miche Graff sub compact - that wont have the chainline issue of a GRX, maybe cheaper and is Hoillowtech II type.
You will need to check you BB type for compatibility.

Good shout.

 

[faster]

No not at 11 speed. Up to 10 speed life was grand and road and MTB shimano played with each other nicely (baring 4700 tiagra which has 11 pull ratios but is 10 speed)

10 speed road and MTB are also incompatible. 10 speed road retained the same pull ratio as 7/8/9 (4700 excepted, as you say), but 10 speed MTB is only compatible with itself.

 

[rivers]

I put a 46/30 chainset on my gravel bike- it's an fsa omega, I also had to swap out the bottom bracket, which wasn't a huge job if you have the right tools. It took me abput 2 hours, most of which was spent gently tapping the BB out of my brand new bike. FD is the the same (shimano 105). Total cost £100ish, but I've had the crankset for years, so might be slightly more expensive now.
Then I did a bit more swapping of bits- MTB rear derailleur, 11-42 cassette, and a jtek shiftmate to make it all play nicely. Slightly bigger job that required new cables. It took me a few hours each evening over 3 days i think. Again, cost about £100. And I can get up almost anything fully loaded.

 

[AlanW]

Bargain at just £333.98.........

https://www.dolan-bikes.com/sugino-0x2901d-compact-plus-including-bottom-bracket-black/