Hi everyone,
I’ve entered the “Ronde Van Calderdale” in a couple of months time. The very brief version is this is Yorkshire’s answer to the cobbled classics, with numerous cobbly hills. Their website has more details for anyone who is curious.
My road bike currently has a full R8100 Ultegra groupset (i.e. 2x12 Di2). I’m contemplating swapping out the rear derailleur for the GRX version (RD-RX825), primarily for the clutch mechanism, to reduce chain slap over the cobbles. Being able to use a 11-36T cassette is also another perk, albeit pretty minor gain over the 11-34T I already have.
Firstly, I just wanted to check my understanding is correct that this would be a straightforward swap?
Secondly, any thoughts on whether this is worthwhile. I already own a 11-36T cassette (on my gravel bike), and spare chains, so I think the only cost would be the derailleur itself. How beneficial is the clutch for rough terrain? Are there any downsides I’m missing?
I also ride an Ultegra 12s on my Wilier and swapped the 11-34 for a 11-36 (105) cassette last year before taking some crazy alpine roads in Italy, and the derailleur worked just fine. Don’t know if I’d do it for short, punchy climbs, but it did bail me out on 20km+ passes. It won’t offer you the clutch mechanism though.
Yes, it’s a straightforward swap to install the GRX derailleur.
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I can second that with the Shimano 105 11-36 cassette working fine with the 12 speed Ultegra rear derailleur. Going back a number of years, before GRX, in the early days of gravel, if you were running Shimano, you had no clutched derailleur options and I don’t remember chain management (dropping or slap) being any issue (although I normally ran neoprene chain protectors back then too, which would help with noise).
I’m going to do a “Well Actually” here, there was an Ultegra RX option that had a clutch (I know because one of my bikes still has one), a couple of pro-riders did use it in Roubaix.https://www.bikeradar.com/features/pro-bike/clutch-performance-degenkolbs-domane-with-ultegra-rx
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I have the 825 rear derailleur on my gravel bike and the mechanical Ultegra RX (with clutch) on my road bike. IMO the clutch is kind of nice, but not “clutch”. Definitely reduces a bit of noise.
I forgot to turn mine on for the Roubaix sportive last year and had zero issues. Here’s a photo of my chain doing wild things during the Arenberg.
In short, I wouldn’t bother unless you think you’d keep it on permanently. Edit: I bet you could get the 36t cassette to work problem free on your current setup. Shimano are pretty conservative with that stuff.
It’s doubtful whether either the clutch or 2T extra on the cassette would make much difference, but if you already have the cassette and a suitable chain I suppose swapping that on couldn’t hurt.
I’ve ridden the RVC a couple of times - each one with a massive hangover (club tradition).
First time I did it with a 11-32 on the back and I didn’t like it, I personally found the gearing too low and it was hard to keep the chain tight.
Second time I had a regular 11-28 and preferred it - got up everything successfully as well.
Appreciate this, it depends on how strong you are, and the cadence you climb at, but I’m 80kg and a I don’t mind spinning.
Tyres and pressure are probably bigger consideration than gearing.
Haven’t done the swap, so can’t 100% confirm, but like mentioned in other comments: road clutch came on Ultegra RX before GRX existed, so should work out fine.
When you set it up to use the clutch, I would recommend doing the indexing with the clutch on. Because I do notice a difference in shifting between clutch on/off.
Personally I wouldn’t swap out the RD just for cobbled climbs. You won’t be going fast enough uphill to get a lot of chain slap anyway. I never ride with the clutch on, on the Ronde terrain here.
Some transparent frame protection tape on the chain stays might be helpful, in case you do get some slap after all.
