Hi all Escapees.
I have a question relating to lowering gearing on a bike for 2 events I have coming up in the next few months. They are mountainous and have 8000m or more climbing in one day, which and I was wondering what, if anything I can do to lower the gearing to give my legs an easier time of it.
The option I have just now, if a 50/34 crank and a 11-36 cassette, crank comes off an old bike as the existing bike runs a 52/36 crank which suits me more on my local roads. The drop in gearing is a bit, done the sums, but I wonder if it’s enough for what I will be tackling.
Is there anything which would allow me to increase cassette size, I see Sunrace make 11-42 cassettes, while keeping the existing Shimano Di2 RD on?
Just for reasons of fiscal prudence more than anything as it is just 2 one day events so not keen on dropping £000’s on parts which I’ll not use much or at all after the events are done.
TIA for any answers.
So your issue is going to be chain wrap. Which RD specifically do you have? It’s possible to avoid the chain wrap issue if you’re careful with your gear selections. Avoid big-big and small-small and you can make it work provided you can meet the clearance for the big cog.
Wolf Tooth make the Roadlink and variations. Wolf Tooth RoadLink Derailleur Hanger Extension – Wolf Tooth Components I have not used one.
The problem with using a larger cassette is that the RD won’t be able to wrap all the chain if you go from large/large to small/small. You’d have to set limits on cross-chaining to avoid chain tension issues.
A subcompact crankset, like a 46/30? There are several brands and you don’t need high-end.
As a shop mechanic, you can’t let a wrap issue out the door. But if you know the issue, set chain length for big-big and stay away from the bottom three cogs in the small ring.
It’s a Dura-Ace RD. I have used the 11-36 cassette with it and it works fine, avoiding a big - big chain line.
I’ve seen them but it says it’s for 10/11 speed, I’m running 12 speed.
Another crankset I’ve considered but, I ride with PM and use that to pace myself. So removing that removes a lot of what I use to control pace effectively on longer rides. In the space of time I have left, I don’t want to start training on solely HR. But thank you for replying.
Which crankset and power meter are you using? For Shimano cranks with a left arm power meter, you could switch to a GRX crankset with 46/30 chainrings. Yes, the chainline is a bit wider, but most of the time the standard road di2 derailleur can be adjusted to work.
If it’s an aftermarket crankset, there are a couple chainring sets that have clever workarounds to fit a 48/32 on a 110 bolt circle, available for four bolt and five bolt patterns.
It’s a Dura Ace R9200 crankset with 4iiii dual sided power meter.
Does the bikinGreen 46/30 or 48/31 rings work with Dura Ace 4-bolt?
If you can accept a lower top gear for these events, and if you can move the FD lower.
I shall look at that option, yes I can cope with lower top end for the two events, the downhills I will use as recovery anyway and I won’t be pushing hard on any flat sections.
Cheers
https://www.ebay.com/itm/113800283451
The 46/30 will have same chain wrap from 52/36, if you keep cassette the same and shorten the chain (again, assuming you can lower the front derailer).
Chainline may also be slightly different. In my case that was fine as I end up using 46 as a 1x and the 30 on longer or steeper climbs.
Assuming your 4iiiis left crank will work on its own, I’d go with combining it with a grx crankset. That way you don’t need to worry about ruining one of your focus events trashing the mech by pushing it beyond it’s limits (eg by, when tired, changing into a ratio you meant to avoid).
Can’t the Di2 be programmed to avoid some cross-chain combinations?
I think you can fudge it by using the sequential shifting mode (where it chooses when to change the big ring), but I’m not sure you can manually change which gears are forbidden when you control the front mech.
This is looking like the best option I have, I’ll see how my training progresses over the next few weeks and if I feel I’m lacking slightly I’ll go this way. Thanks for the advice and ideas from everyone. You’ve all been a great help.
There are subcompact chainrings for Shimano Cranks from Absolute Black (I might have a set lying around at home), and maybe Rotor. You could go to 46/30 I think in the front.
I have a Wolf Tooth Road Link on my gravel bike. It originally came with full Ultegra 8000 (11-34, 50-34) but I wanted more (or less). The road link allowed me to run an 11-40 XT casette, with only little-little combinations vaguely problematic. But I never ride down there so rarely come across the issue day-to-day, and on the rare occasion I do it’s at low power.
I’ve since swapped to a GRX crank for even lower gears with the same rear set up and it’s been like that for a couple of years now.
Works for me but YMMV.
- The Bikingreen rings can be had in 4x110 (Shimano) or 5x110, but note the chainline moves in 2-3mm
- The AB rings are oval and (I think) retain the normal chainline as the minor axes avoid the spider arms; these were intended for 11 not 12 IIRC
- The largest Shimano 2x12 cassette is 11-36, but larger ones are available elsewhere, i.e., 11-39/40/42/45 from ZTTO (Aliexpress). These are most likely to work with GRX, then 105, Ultegra and Dura-Ace RDs, in that order
- The smallest normal rings to fit 110BCD (4 or 5 bolt) are from TA, and maybe others. FWIW, oval/squarish ones can be had from Sugino and others with <33T, and these should retain the normal chainline
I’d probably just buy a new bike 
Ok. Some good advice so far. I have spent the last 2 years trying to wring as much as i can out of my di2 setups so here are my findings.
On your rear derailleur you can make an 11-40 cassette work but it is close and requires perfect chain and b-tension adjustment. Better results will be had with a long cage or larger jockey wheel upgrade. Only 2-3 teeth is needed across the 2 jockey wheels for significant improvement.
There are many 33T small chainrings on the market to fit the 4x110 cranks so grab one of those.
With those upgrades your low ratio drops from .94444 with 34-36 to .825 with 33-40.
Be sure to tune the Di2 with the app to exclude the 3 smallest sprockets on the rear when in the small chainring and the 2 largest sprockets in the big chainring.
Enjoy the climbing!
Cam