Apologies, I know this has been done before, but I'm struggling to get my head around this... I've spent most of the morning looking at various articles on gravel gearing and changing to a larger cassette to get the illusive easier gears for steeper stuff which I really struggle on.

So I went ahead and ordered one of those Deore 11-42's that were going cheap on Wiggle. Current set up is Tiagra with an 11-34 on the back and a 34-50 on the front. From what I can see, it's looking like the present 4700 mech won't accommodate the Deore cassette, plus Wolf Tooth stuff isn't compatible. Anyone advise what my options are - a new mech? Send the Deore back?

Thanks

The 4700 medium cage mech has a capacity of 39 which is what your current setup adds up to (34-11)+(50-34) so you cannot safely go much bigger on the cassette.

You either need to swap the mech to one with a greater capacity (marginal gains and possible shifter compatibility issues) or reduce the size and range of the chainset. 30/44 or lower such as a mountainbike 26/38 would be advisable but then you may get poor shifting from the front mech as well as needing to reposition it to suit the smaller ring. Even if you could fit one, a Wolftooth roadlink won't increase capacity, they only serve to move the top jockey wheel further from the axle so the chain will climb onto the bigger sprocket. It's about time manufacturers stopped speccing road groupsets on gravel bikes but I guess it's similar to sales of 4x4 MPVs where a small percentage actually get used off road.

The newer (R7000, GRX and UX) rear mechs all only officially support 11-34 but will all cope with 11-40 cassettes with a wind in of the b-screw. Bikepacking.com just did a video this week with a GRX rear mech where he could only get 11-42 to work nicely if he used a goatlink.

Tiagra 4700 is from the previous generation so probably isn’t as flexible

you can fit a 9 speed MTB mech but not sure that it works with tiagra - you will need to google this to be certain

9 speed mtb mech is worth a try.

Shimano are notoriously conservative with their numbers. I'm running 50/34 and 11-40T 11 speed with a R8000 mech and it's fine, even though it is well outside the published maximum capacity.

I had a tiagra set up working with 34/50 11-40 fine but it wouldn't work on 11-42

ScotRoutes wrote: ↑Sat May 09, 2020 1:02 pm 9 speed mtb mech is worth a try.

4700 Tiagra stuff uses a different pull ratio so don't think this works any more unfortunately.

I was in the same boat and decided it would just be easier to change chainset + front derailleur to GRX - around €100 from one of the German websites. The front derailleur is much neater than the 4700 one too (more tyre clearance).

I reckon the standard gearing on most gravel bikes is more focused on racing (which seems to be more of a thing in the US than here) and is poorly suited to real adventure riding. My solution after trying a few options was to swap to a 2x mountain bike chainset with 22/38 chainrings. I use this like a reduction box on a "proper" 4x4. 90% of the time I'm on the 38 ring which gives me a reasonable range of gears for the road and on some off road, the 22 is reserved for really steep off road stuff (or road climbs when I have luggage on). The 38 spins out on steeper road descents but only at speeds where it's probably more efficient to coast and adopt an aero tuck anyway. On the rear I'm currently running an 11-32 10 speed cassette although I have an 11-25 as well. I didn't want to go for a wider ratio cassette as I don't want the gaps between ratios to be any bigger than I have currently (and even upgrading to 1x11 would do this). A lot depends on the terrain that you ride but I've found that if you try to climb steep off road slopes by standing up and pushing larger gears you end up spinning the back wheel, so seated climbing in a really low gear seems to work better for me.

I'm running 11/40 cassette with a 46/30 chainset on tiagra mechs and shifters. All runs fine and not too much difficulty setting up. You'll need a wolf tooth to extend the rear mech so it can get around the large cogs... Another way to do it is to change the rear mech to a MTB one and use a j/tech pull adjuster to make your tiagra shifters work with it.... Essentially what I'm saying is it can be done :) although I think I'd be ditching the 11-42 cassette for an 11-40. Because if go for smaller chainrings as well then something like a 42/30 combo will have you spinning faster than a washing machine and moving slower than an ant! I Find the 40/30 combo is only of use on really steep hills fully loaded.

Just to add...I used absolute black chainrings... Not cheap... Other options are FSA tempo adventure, Shimano grx, or spa cycles do some really interesting combo's

thanks for all for the comments, much appreciated.

i'm probably even more confused now, as there do appear to be a few different ways to get this cassette to work, however they come with possible downsides and likely extra expense. i guess i'm concerned that (1) i'm not a particularly competent bike mechanic and (2) the extra cost for something that might/might not work! i'll think it over and see if I can come up with a solution! CHEERS!

Just wondering why a goatlink won’t work, is the hanger an odd shape/design?

I generally think the simplest solution to getting a set of gears suited to the real world (mine, not yours. Yours might be different) is a switch of cranks or rings if appropriate / possible. I recall my Arkose has an 11/36 ont' back and 28/36 rings or something similar. However, I tend to view such a bike as a lightweight mountainbike rather than a heavy road bike, so take from it what you will.

Amazes me that with all the hype around Shimano Gravel and GRX, they still haven't got a 26-40 range or 28-42 chainset. I really rate Shimano's kit but they're still too far off the mark in this area.

Same / similar to Stuart here, XT 28-40 MTB 10s chainset and 11-32 or 11-36 rear (650B wheels). No ego problems related to my chainring sizes Bar end shifters make it easy to get past compatibility limitations. It's not perfect, a narrower Q crank would be nice, but it's pretty good. Oddly, imo still more suitable for gravel and touring than anything made for drop bar bikes. I use the bike as more of a gravel/road tourer than MTB most of the time. I spin out at 28-30mph and that's fine.

Gari wrote: ↑Sat May 09, 2020 5:38 pm Just wondering why a goatlink won’t work, is the hanger an odd shape/design?

When I checked the Wolf Tooth site, it says it's not compatible with the current Tiagra mech, it only works with Shadow+ mechs.

Now I need to work out what i need - new rear mech/new cranks....!

Other option is to get a 10 speed grx rear mech which will work with tiagra 4700. It's rated to 36t but I got it working easily with an slx 40t cassette. The wolf tooth goatlink would work if you wanted it as its shadow+ and all simple to set up. 10spd grx rear mech is a lot cheaper than 11spd, has a clutch which keeps it quite off road, and will work with 11speed if you upgrade shifters later.

All because you bought a cassette!

EDIT - just seen you have a compact chainset, which might be too big for grx, not sure. Either way 50t isn't needed on a gravel bike, so glad I ditched my compact chainset...

Right, gotcha. Been ages since I used one so can’t really remember what they do/don’t work with.
It is a minefield for sure.

Won't one of the cheapo mech hanger extenders work with that one?

jameso wrote: ↑Sat May 09, 2020 6:50 pm Same / similar to Stuart here, XT 28-40 MTB 10s chainset and 11-32 or 11-36 rear (650B wheels). No ego problems related to my chainring sizes Bar end shifters make it easy to get past compatibility limitations. It's not perfect, a narrower Q crank would be nice, but it's pretty good. Oddly, imo still more suitable for gravel and touring than anything made for drop bar bikes. I use the bike as more of a gravel/road tourer than MTB most of the time. I spin out at 28-30mph and that's fine.

Same here

For many of us, our "gravel" bike carries out many roles. I'm certainly happy to have 50:11 at my disposal on occasion.

As above, me too. It is pretty hilly hereabouts too:)

https://www.bikeinn.com/bike/shimano-de ... 36627490/p

Hopefully this link works , but this mech claims to be compatible with 11-42 cassette. Should be ok, or would I still have issues with my chainset?

Won't work with tiagra shifters if that's what you have. Shimano mtb and road isn't interchangeable. 10spd tiagra is the same cable pull as 11spd Road derailleurs, but 10 and 11 spd mtb are not compatible with road stuff unless you get a cable pull converter like a wolf tooth tanpan or a shiftmate...

My gravel bike had (broke the frame) XT 26/36 cranks, and an XT 11speed 11-40 cassette
Ultegra shifters.
Gearing was fine for pretty much all bikepacking; and went up some nasty hills in Norway.

faustus wrote: ↑Sat May 09, 2020 10:07 pm Won't work with tiagra shifters if that's what you have. Shimano mtb and road isn't interchangeable. 10spd tiagra is the same cable pull as 11spd Road derailleurs, but 10 and 11 spd mtb are not compatible with road stuff unless you get a cable pull converter like a wolf tooth tanpan or a shiftmate...

Darn. Ok thanks