Ultegra mods for gravel

[Neillp]

Hi all,

I have bought a second hand Ribble Ti gravel bike that came with an mechanical Ultegra 8000 groupset - 50/34 upfront and 11-32 on the rear.

I found that this gearing is not ideal for serious off road uphill work but I do like the double chain ring upfront as I intend to use this as my winter road bike too.

I have changed the rear cassette to a 11-40 and after adding an extra 4 links to the chain it works to a point but the rear mech is totally maxed out and I am concerned that that is will let me down or start throwing the chain when on the granny ring as the chain is so slack.

My question is would a GRX mech work any better? and if so which one do I worder that will work with a double chain ring up front.

Cheers

Neill

[fastezzie]

I would recommend subcompact chainrings up front. Absolute black makes ovals in 46.30 and 48.32 that bolt onto a R8000 crank, they feel really nice and have surprisingly good shifting too. 46x11 is a pretty tall gear.

[Neillp]

I would recommend subcompact chainrings up front. Absolute black makes ovals in 46.30 and 48.32 that bolt onto a R8000 crank, they feel really nice and have surprisingly good shifting too. 46x11 is a pretty tall gear.

Thanks I will have a look at that, I could then put my 11-32 cassette back on or maybe a 11-34

[MayhemSWE]

Officially the GRX derailleurs aren't any better. RD-RX812 can clear larger cassettes, but as it is intended for 1x use only it does not have any increased chain wrap capacity. Still I do believe people have been using it for 2x with decent results…

[zmjones]

Officially the GRX derailleurs aren't any better. RD-RX812 can clear larger cassettes, but as it is intended for 1x use only it does not have any increased chain wrap capacity. Still I do believe people have been using it for 2x with decent results…

i'm curious about the performance of the rx812 w/ the garbaruk cage mod in 2x config. really wish i could run 50-34 x 11-40 w/ a proper capacity rd. When i ran mechanical i had an xtr sgs rd w/ a tanpan and although the shifting wasn't as good as di2 i did have better chain security. in really rough stuff i can tell the chain is too slack now.

[Aesch]

Officially the GRX derailleurs aren't any better. RD-RX812 can clear larger cassettes, but as it is intended for 1x use only it does not have any increased chain wrap capacity. Still I do believe people have been using it for 2x with decent results…

They do have the clutch for chain tightness.

[pdlpsher1]

The best gravel bike gearing IMHO is the GRX sub-compact crank (48/31) and the 11-34 cassette. The Shimano 11-34 cassette is great for gravel. It has very tightly spaced gears in the middle of the cassette. A 11-32 or 11-40 aren't ideal for gravel riding. If you must have lower gearing than a 31-34 you can use a 11-40 cassette with an XT long cage modification (video link below). I don't know if the XT long cage can fit on your Ultegra. It probably would. As for the clutch I find it as unnecessary. I have a RD with a clutch but I always leave it off. I ride a lot of rough stuff and never had a dropped chain or chain bounce issue. I'd say if your budget is tight you would do just fine without a clutch.

https://www.youtube.com/watch?v=7kUxmkuJWNg

[bobrayner]

Hi all,

I have bought a second hand Ribble Ti gravel bike that came with an mechanical Ultegra 8000 groupset - 50/34 upfront and 11-32 on the rear.

I found that this gearing is not ideal for serious off road uphill work but I do like the double chain ring upfront as I intend to use this as my winter road bike too.

I have changed the rear cassette to a 11-40 and after adding an extra 4 links to the chain it works to a point but the rear mech is totally maxed out and I am concerned that that is will let me down or start throwing the chain when on the granny ring as the chain is so slack.

My question is would a GRX mech work any better? and if so which one do I worder that will work with a double chain ring up front.

Cheers

Neill

A left-field suggestion: Get a different rear wheel with a smaller radius, maybe 26", which lowers gearing in addition to any cassette changes you make. MTB wheels tend to be built for harsher terrain, and it'll be easier to find tyres with an off-road bias. Keep the existing rear wheel as a winter road wheel. No?

This assumes you have disc brakes. It's less practical with old-style brakes.

[boots2000]

Yes- get GRX rear mech and 11-40 cassette. Works really well. Maybe neeed a new or longer chain for this.

[Neillp]

Thanks for all the advice, it seems I need to focus on my gear ratios, then chain wrap capacity and then choose a rear derallier to suit.

I belive my current chain wrap requirement is (40 -11)= 29 + (50-34)= 16 - Total chain wrap is 45 (29+16).

Shimano states my Ultegra GS has a chain wrap capacity of 39
The GRX810 has a chain wrap capacity of 40 so not much better.
The XT SGS has a chain wrap capacity of 45 which would work.

So the cheapest option right now is to try and convert my Ultegra with the XT SGS long cage - would cost about £25.

Alternatively I could go with a 46/30 upfront (Absolute Black chain rings) and a 11-34 at the rear which would probably give me a low enough gear and reduce the chain wrap to 39. I can then keep my rear mech standard.

I think I am going to go for a couple more careful rides to confirm if I am happy with the current gear ratios and will report back on what I decide to do and how it works out.

Cheers

Neill

[fizzaz]

FWIW I haven't had any issues with my 46T chainring, 11-46 XT Cassette, GRX 810 derailleur, and Ultegra Shifters.

[Neillp]

FWIW I haven't had any issues with my 46T chainring, 11-46 XT Cassette, GRX 810 derailleur, and Ultegra Shifters.

Is that on a single or double up front?

[CampagYOLO]

I use a SRAM PG1170 11-36 cassette with an Ultegra RX rear mech and the shifting is perfect, no issues what so ever.
It's paired with a 48/32 crankset and IMO it's the perfect gearing for any kind of gravel riding.
Also you don't have the 11-13 jump that I hate and the Shimano 11-34 cassettes have.

[fizzaz]

FWIW I haven't had any issues with my 46T chainring, 11-46 XT Cassette, GRX 810 derailleur, and Ultegra Shifters.

Is that on a single or double up front?

Single Wolftooth ring. The derailleur doesn't seem to be maxed out either.

[pdlpsher1]

Also you don't have the 11-13 jump that I hate and the Shimano 11-34 cassettes have.

The 11-13 jump never bothered me since I'm not using the 11 or 13 very often on my gravel rides. Most of the time my chain is in the middle of the 11-34 cassette where the jumps are small. IMHO Shimano got the gearing right with the 11-34 for gravel. I don't think the Sram 11-36 was really meant for gravel riding but if you like it then that's great for you.