Big Ring vs. Small Ring

HI! So I am wondering about using the Big Ring vs. Small on my indoor sessions in SYSTM.
In Essence, I usually train using the Big Ring (53T). I find it manageable in terms of hitting power targets and meeting the objectives of the workout.
Similarly, the Small Ring (39T) works too with similar results.
The RPM difference between the two during a workout is around 8-10RPM, marginal really.
So, is there any preference or need to use one or the other? Naturally when doing the 4DP etc, bigger is better, but for Cobbles/ Attacker/ all the usuals, is there a rule of thumb?
Best
Kevin.

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In ERG mode, most smart trainers respond and stabilize more quickly to commanded power changes when using the small ring and a middling cog. I generally use the small ring and put the chain on the cog that best lines up with it and call it good. For Level mode, set the Level to something appropriate and shift as you normally would.

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Always use the small ring for workouts and 4DP unless you’re doing some free ride. Smaller ring is more accurate to the power since the flywheel won’t be spinning as quickly and won’t carry as much momentum and the plus benefit is that the small ring is cheaper to replace.

Your power numbers on 4DP will be a bit more accurate with the small ring unless it’s the sprints.

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As for me, I generally use the small chainring during the warm up and cool down sections of the ride but for the main efforts it will be the big chainring. It’s easier for me to get on top of the power targets on the big chainring than the smaller one granted I ride on a dumb roller/turbo trainer.

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Thanks for the insights, I’ll do the next couple of sessions on the Small Ring and see what comes out of it. Hopefully a little less fatigue too.
Regarding ERG mode, I do prefer ERG, so generally i stay there.

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I’ll pipe in with an alternate view. It depends on your trainer, gearing, and your ability. My trainer bike only has a 12t in back. My trainer can’t hit low cadence high power efforts (like G.O.A.T.) in the 39/12 (It may be 36/12, and maybe I’m also not willing to cross chain quite that badly), so big ring it is. If I’m using level mode, I’ll switch back and forth, but for erg mode, I just keep it in the big ring. It also warms up the trainer (or tire probably, yes, it’s that kind) faster. As for cost of chainrings, yes small rings are cheaper, but big rings almost never wear out, because there’s less leverage (smaller radius ratio from pedal to teeth) and more teeth to share the load over.

There shouldn’t be any RPM difference when things are working. The whole point of erg mode is that the trainer will produce the right resistance to hit your power target at whatever RPM you do. In level mode if you can’t get to a high enough gear in the small ring to hit the power target withohut going over the rpm target, that just tells you you need to be in the big ring.

Why not just try both?

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For me small ring for ERG mode and I try to use say the middle 3 sprockets on the cassette over different sessions just so I don’t have all of the wear on one sprocket. I only use the small ring on 4DP for the recovery parts as even as a old codger I would never hit the power targets (and go over them of course!) in the small ring so for those bits I use the big ring @1% level mode my ratios are 52/36 with 11/28.

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Sorry to break it to you, but using the small ring in Erg mode is actually harder than the using the big ring and is likely to leave you more fatigued because you don’t have as much flywheel momentum to smooth out your pedal stroke. The first time I did G.O.A.T on my smart trainer in the small ring was a revelation, it worked muscles I didn’t know I had.

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In ERG mode the ride feel is different between big and small ring. For workouts that look like climbs, I use the small ring to get a similar feel. For flat workouts like Team Scream and Cobbler, I use the big ring. As for the rear cogs: I try to keep the chain as straight as possible to keep the wear low.

In the 20 minute sections of FTP and HM, I use the big ring and Level 1. I find it much better to ‘tune’ the power at lower level resistance than riding it in the small ring at higher resistance.

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I just add reference to older blog post by Wahoo about this topic (I recommend also to view the embedded video by GPLama): https://eu.wahoofitness.com/blog/erg-mode-gear-selection-matter/

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Unless you’re starting and stopping a lot (in which case higher flywheel speed makes things easier), in ERG mode you shouldn’t notice any difference in the small chainring except for incrementally improved power accuracy and stability (because ERG works better on most trainers with slower flywheel speeds).

One thing is to watch out for using ERG on workouts that have short duration sprints as the ‘meat’ of the workout. Violator is a great example but some of the 40/20 tabata workouts are more fun to do in Level mode vice ERG as this requires you to do some planning.

I generally try to mimic how I’d ride outdoors, small ring on the climbs and big ring on the flat.

I do try and stick with silent gears as indexing is not perfect on my direct drive and centre cogs on the cassette tend to provide the smoother and quieter experience.

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I suspect that will be influenced by which smart trainer it is. Mine has a big effective moment of inertia (flywheel moment of inertia x internal gear ratio), so for me at least, I don’t notice it lacking using the small ring and middle cog, and the improvement in response and settling to ERG mode power changes is significantly better. It’s also quicker and easier to make called for changes in cadence than in a high gear.

As far as being more fatigued, I’m not sure that’s worse, better, or irrelevant.

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I recently did the Antelope workout which has 10-min intervals at around 90% FTP. Since I use a smart trainer in ERG mode, I normally do not shift gears and just leave it in my small chainring and a cog that makes the chain straight.

Five minutes into the first interval, and holding a cadence of 85-95 (Antelope recommendation), I found myself really struggling.

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I also have found that there seems to be less strain on my knees. There never was excessive strain etc. as I have had a professional setup so no niggles at all. Its just seems ‘better’ on the knees.

The idea of ERG mode is that it will keep you at the target power regardless of cadence and all you need to concentrate on is pedalling. If 5 minutes into your first interval at 90% FTP and you are struggling then maybe you are just tired or your FTP is set too high. I use ERG mode all of the time apart from when rapid changes to power are needed or the workout recommends it because it is so easy to “cheat” in level mode and drop the power slightly as things get harder

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In reality it should make no difference to the strain on your knees. Target cadence/power should be constant if you select the correct gear when in level mode or as near as you can get. Unless of course in level mode you use a bigger gear and naturally spin slower to hit the target power and therefore there will be more strain on your knees

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Yep. With respect to knees, In ERG mode, gearing should mainly have no effect as the trainer will adjust resistance so that you get the same power irrespective of gearing. Power is equal to pedal torque x cadence. That means for a given power, you’ll need the same torque (pedal force) at the same cadence no matter what gear the bike is in (within the limits of the trainer). If you increase cadence, torque will decrease in proportion, and vice versa. If, at a given power, your cadence starts to decrease, the required torque will increase so as to maintain power. Where gearing does matter in ERG mode is when you need to change cadence. It’ll take more torque to increase cadence, and take longer for it decrease.

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