Double Chainring Ratios / Clearance.

[Petero]

Hi All,

Currently have a 2 x 10 set up. Rather than going all out to 1 x 11 just yet (trying to get fitness up first), am looking at reducing the gap between the big 36T and tiny 22T (ruins cadence everytime). I can buy a 64BCD ring with up to 28T - this may be a stretch so more likely 26T with 11-36 rear. Question is -> These normally come as a set with defined difference between rings (shimano) would there be any issues (clearances, derailleur settings?) in going to 36/28 or 36/26?

Thanks gang.

 

[The Duckmeister]

The main reason for the defined sets is the alignment of the shift ramping. You can run mismatched rings, but shifting, especially up to the big ring, can get a little bit crunchy.

 

[BKMad]

You can compensate for the cadence issue by shifting up one or two gears at the rear when you drop to the smaller chainring. Once you get the hang of it, its not far from any other downshift depending on the jump between chainrings. Back in the day of triple chainrings, it was pretty easy as the jump between chainrings wasn't so much so you only needed to shift up one gear at the rear to compensate. A 36 to 22 jump is pretty big, so you'd probably need to shift 2 gears to get an acceptable jump.

Of course, this is a lost art these days of 1x drivetrains.

 

[rowdyflat]

I have 34/22 x 11-34 and my wife 36/24 x 11-36 and both these work fine ,I agree 36/22 is a bit of a jump without a double shift.
It depends on the terrain you ride ?

 

[rowdyflat]

Wow I seem to have that effect , as soon as i post something the thread shuts down.
Its either they are still digesting my wisdom or they are speechless about the fuckwittery ?

 

[Zam]

Yeah I run 36/26 and even with this i find myself downshifting at least one if not 2 gears when going to the smaller chain ring, although i very rarely use the small change.

 

[Petero]

Thanks guys. Yeah I know the double shift and all but even then it's still a PITA due to the large gap. I can get buy on my usual trails with around a 0.75 ratio so a 26 at the front would be fine. Can the FD be tuned to change shift ramping? (never even touched the front derailleur...)

 

[The Duckmeister]

Shift ramping is built into the big chainring; FD just mashes the chain against the ramps. A 38T ring to pair with a 24T small ring will have different ramping to the same size ring to pair with a 26T small ring, due to the larger climb from the smaller small ring.

You could get a triple.... Bigger range, smaller jumps between rings. :wink:

 

[Flow-Rider]

Maybe try dropping into the small ring a bit later up the climb. I'm the only one running a 3x and 2x in my main riding group and I'm not having any issues of spinning out.
Most of the Xt stuff of the same speed and year seems to work ok, you might just need to adjust the way you up shift. Sometimes just a good fast flick or hold the lever depressed for a bit longer for a better shift going up.

 

[stirk]

Wow I seem to have that effect , as soon as i post something the thread shuts down.
Its either they are still digesting my wisdom or they are speechless about the fuckwittery ?

Nah, not you, most of us cool kids went 1x years ago and so have nothing to add.



Personally I'd be using a spreadsheet to calculate all the different ratios I'd get changing any ring combination and base it on required granny and what big ring I could actually push downhill to go faster. Using the data you could see where the optimum shift point is for front and rear to keep ratio jumps smooth through the range.

 

[Petero]

Shift ramping is built into the big chainring; FD just mashes the chain against the ramps. A 38T ring to pair with a 24T small ring will have different ramping to the same size ring to pair with a 26T small ring, due to the larger climb from the smaller small ring.

You could get a triple.... Bigger range, smaller jumps between rings. :wink:

Honestly, the triple on the hardtail is more user friendly than the double... Thanks for the info mate, just boggles that shimano would design a chainsset where the equivalent ratio is ~4 downshifts on the rear...

Maybe try dropping into to the small ring a bit later up the climb. I'm the only one running a 3x and 2x in my main riding group and I'm not having any issues of spinning out.
Most of the Xt stuff of the same speed and year seems to work ok, you might just need to adjust the way you up shift. Sometimes just a good fast flick or hold the lever depressed for a bit longer for a better shift going up.

I was actually thinking maybe earlier into the climb, that way climbing = in the little front, and descending = in the big. Could work.

... using a spreadsheet ...

I love spreadsheets so this is already done. Optimum point is still 3 downshifts away..

Based on the advice i'll probably just live with it and play around with shifting habits and timing- Just thought this might be a easy $20 fix.

Thanks all.

 

[hifiandmtb]

Tape the spreadsheet to your handlebars - you'll probably need it.

 

[stirk]

Just go 1x!

I manage .71 granny, sometimese would like lower but push harder and cope on all but the steepest slogs. Only spin out on long mild sloping decents with 2.7 rear. I'd like a higher gear on 2% of any trails I've ridden so it's an easy compromise to lose top end.

Do it.

 

[rowdyflat]

I've said this 10 times before BUT
Dont listen to any advice about 1x gear ratios from others, they are macho, dont know you or the hills you ride up and are probably 16 years old and clueless= as useless as second hand toilet paper.

 

[Daniel Hale]

id still just but a 30t oval & run one-by, you l get used to it pretty quick, then if confident get a 32, but the 30t shoudl be fine