Shimano chainrings - Mixing Standard/Compact

[hokoman]

We took out my wife's bike for a quick ride around the park today, and she is a pedal masher - doesn't like to spin at all. She has a compact with the new r8000 11-34 on the rear and she says the 34 is 'too easy' for regular riding without being in the smallest cogs. Has anyone done a 39/50 and did it shift ok? I suppose for $20 I can try it and then swap out for standard if it works better for her.

I'm actually thinking that the 39 will work better for me here too. I liked having a 34 in CA when I was actually riding some big climbs, but around NYC metro.. 39 should be fine.

TIA.

[David Tollefson]

"Compact" and "standard" refer to the bolt hole circle diameter, not the actual number of teeth on the chainring (though you can't put anything lower than a 39 (or in some cases a 38) on a standard...

ANYwho... Yes, a 39 with a 110mm BCD will work just fine.

[nooneline]

Originally Posted by David Tollefson

"Compact" and "standard" refer to the bolt hole circle diameter, not the actual number of teeth on the chainring (though you can't put anything lower than a 39 (or in some cases a 38) on a standard...

ANYwho... Yes, a 39 with a 110mm BCD will work just fine.

Not anymore - now that a lot of companies are on the 4-bolt/offset 110bcd crank that works for all chainring combos, standard is 53/39, midcompact is 52/36, and compact is 50/34.

[miguel]

I don't understand how 50/34x11-34 could be too little or too much. That configuration gives me all of it.

[jtbadge]

I'd just get a smaller cassette range, 11-28 or the likes. Then the ratios will be closer as you shift across the cassette.

[rellis]

I am running a 39/50 on Shimano 6800 cranks. No problems at all.

[hokoman]

Originally Posted by miguel

I don't understand how 50/34x11-34 could be too little or too much. That configuration gives me all of it.

She only rides the 11/13/15 in the 34. On the 11, her chain catches the 50 every revolution just enough to annoy me!

Originally Posted by jtbadge

I'd just get a smaller cassette range, 11-28 or the likes. Then the ratios will be closer as you shift across the cassette.

The 11spd r8000 cassette is mounted on a classic king hub. I can't really go smaller without getting a new rear wheel.

Originally Posted by rellis

I am running a 39/50 on Shimano 6800 cranks. No problems at all.

Perfect. Thanks!

[FlashUNC]

If she's that far down the cassette in the small ring, why doesn't she just slap it up into the big ring?

If you're cross-chained that much in the small, might as well be on the big ring in the middle of the cassette with options.

[Mark McM]

Originally Posted by hokoman

She only rides the 11/13/15 in the 34. On the 11, her chain catches the 50 every revolution just enough to annoy me!

If she only uses the 11/13/15 on the small chainring, why does she have a small chainring at all? A 34-15 gear is equivalent to a 50-22. If she stayed in the big chainring, and if the cassette is an 11-34, she still wouldn't use the lowest gears.

[hokoman]

Originally Posted by Mark McM

If she only uses the 11/13/15 on the small chainring, why does she have a small chainring at all? A 34-15 gear is equivalent to a 50-22. If she stayed in the big chainring, and if the cassette is an 11-34, she still wouldn't use the lowest gears.

The 11/13/15 is on 75% of the ride. There is a small uphill that she needs to shift for in the small ring too. I got the answer I needed for the front chainring. Thanks everyone. Attaching a pic of the bike.

Sent from my SM-G930P using Tapatalk

[Wasatch]

Originally Posted by Mark McM

If she only uses the 11/13/15 on the small chainring, why does she have a small chainring at all? A 34-15 gear is equivalent to a 50-22. If she stayed in the big chainring, and if the cassette is an 11-34, she still wouldn't use the lowest gears.

^ This. She can achieve the same ratio as the small-to-small combo she's currently using by shifting into the big ring. Plus your potential to drop a chain goes down substantially as well since you'd be taking a ton of slack out of the system.

[loxx0050]

Me thinks you should get a 1x chainring setup or just a 1x crankset and ditch the front derailleur. She isn't using it anyways. Something maybe a 36 ring if she needs it for the hill or a 42 sounds like it would work.

But that is just how I'd change it up (sell the parks you pulled off to recoup some costs).

[palincss]

Originally Posted by miguel

I don't understand how 50/34x11-34 could be too little or too much. That configuration gives me all of it.

50x11 is definitely too much unless you're a tandem, as far as I'm concerned. And as low gears go, 34x34 isn't. Now 24x34, that's a low gear.

[11.4]

Seems that she needs to learn how to use her gears properly. And she should realize that she may want to hold onto those lower gears for some time when she hits bigger hills.

However, to the point of your original question, I've mixed and matched in 6800 and 9000. What I've found is that if you do something like a 39/50, the 50 will have begun its taper towards the outside of the chainring and the 39 will thus be spaced farther from the 50 than a 34 would be. This means that the chain will tend to hang at times between the small and large ring and will skating along the tips of the small ring rather than settling down onto it and engaging. I could force a strong shift and avoid the problem, but I'd still get funky front shifts on hills. I finally abandoned the effort.