Hole in my 2X9 Gearing!!

[Skylark]

I'm running 2 X 9 speed :

Chainrings 36t & 22t

Cassette 11t to 34t

 

I'm happy with the range - excellent top speed and granny speed

Just theres a giant hole in the middle and I lose my cadence rythym...

I can use 7 cogs of the cassette in either chainring , I have noticed I am totally chewing up my bottom RD pulley tho.

Where should I ideally be changing up/down between the front rings - about 5 cogs from the top or bottom depending if I'm moving up or down?

 

I'm thinking of changing the big chainring to 34t or maybe 32t , but I think 32t may be a little drastic but that is what a typical middle ring would be.

But I may have a rather limited top speed with a 32t.

 

What you chaps think?

[patches]

I've just gone 2x9 on my new bike. All my other bikes have been 1x9 setups with a chain guide.

 

DH bike: 38T front, 11-32T rear

4X bike (which I used for trail riding): 36T front, 11-34T rear

FR/AM bike: 36T front, 11-34T rear

 

I guess rinding those made my legs used the the abscence of a granny gear.

 

The new AM bike is 36T & 24T up front, 11-34T rear, with a chainguide and bashring.

 

So yeah, I don't have any answers... but I'm interested to see what feedback is given from other 2x9 users.

 

BTW, what sort of riding are you doing on this 2x9 bike?

[Skylark]

Pretty much AM trail riding single track stuff , no Blazing XC racing

I'm on a Morewood Shova

[BushGoblin]

i converted to 2x9 on Rotors a couple of month ago, took a while to adjust but loving it. Mostly XC and Enduro, not that i am good at either. Running 40/27 11/34 setup on SRAM. i can pretty much use all gears, but i must admit i haven't checked my pulley.

[Skylark]

i converted to 2x9 on Rotors a couple of month ago, took a while to adjust but loving it. Mostly XC and Enduro, not that i am good at either. Running 40/27 11/34 setup on SRAM. i can pretty much use all gears, but i must admit i haven't checked my pulley.

 

Big legs you got!!

You don't notice at hole between your big and small chainring?

As in you on one of the middle 2 cogs on the cassette and if you drop from big chainring to small chain ring or vise/versa you lose your cadence

Edited January 18, 2012 by SkyLark

[NINER_boy]

Hi SkyLark

 

My advice would be to try and mimick the ratios and sizes of a tried and tested 2x10 ratios.

 

EG;

SRAM XX crainring ratio: 26 / 39 (your setup 22 / 36)

Now, this is a 1 x 1.5 ratio change between the small and large rings.

Thinking like this, your chainring ratio should be 22 / 33, and is far from that.

You increase the large ring T count to NOT run out of revs at top end, but in so doing increase the small blade / large blade ratios, witch in turn makes the ratio (and revolution ) jumps at the rear sprocket that much more accentuated.

 

Another issue you have is here;

11-12-14-16-18-21-24-28-32-36 (and this is a 10 speed cassette nuance)

 

You have a 9x setup, witch will make the jumps even bigger and earlier because you have one less gear.

 

So with your increased ratio jump at the Front, this will accentuate the ratio jumps at the rear sprocket as well.

 

My suggestion would be:

Get your F gearing ratios sorted as per 1 x 1.5 small and bigblade ratios.

 

Around 24 / 36 (if you want to keep the 36 bigger ring option for top end revs).

This will get the ratio difference at the rear down, and your gears "closer" to each other.

 

You will see that the difference in "granny gear" will be relatively unnoticeable.

 

Have a look at a chart of gear ratio calculations for track bikes and SS bikes.

Say all is measured in distance travelled per pedal stroke;

You will see that 1T difference in the rear will make you travel FURTHER than the same ratio with 1T increase in front chainring (if that does make sence???)

These are now assumed values for explanation purposes

32x18; Distance per one pedal stroke =2m

32x17; Distance per one pedal stroke =2.7m

33x18; Distance per one pedal stroke =2.15m

 

I hope this helps.

 

I will try and find this mentioned chart online.

 

The bottom line is:

for a 2x9, get your fron chainring ratios closer than what they are.

 

Happy hooping

[NINER_boy]

Hi SkyLark

 

My advice would be to try and mimick the ratios and sizes of a tried and tested 2x10 ratios.

 

EG;

SRAM XX crainring ratio: 26 / 39 (your setup 22 / 36)

Now, this is a 1 x 1.5 ratio change between the small and large rings.

Thinking like this, your chainring ratio should be 22 / 33, and is far from that.

You increase the large ring T count to NOT run out of revs at top end, but in so doing increase the small blade / large blade ratios, witch in turn makes the ratio (and revolution ) jumps at the rear sprocket that much more accentuated.

 

Another issue you have is here;

11-12-14-16-18-21-24-28-32-36 (and this is a 10 speed cassette nuance)

 

You have a 9x setup, witch will make the jumps even bigger and earlier because you have one less gear.

 

So with your increased ratio jump at the Front, this will accentuate the ratio jumps at the rear sprocket as well.

 

My suggestion would be:

Get your F gearing ratios sorted as per 1 x 1.5 small and bigblade ratios.

 

Around 24 / 36 (if you want to keep the 36 bigger ring option for top end revs).

This will get the ratio difference at the rear down, and your gears "closer" to each other.

 

You will see that the difference in "granny gear" will be relatively unnoticeable.

 

Have a look at a chart of gear ratio calculations for track bikes and SS bikes.

Say all is measured in distance travelled per pedal stroke;

You will see that 1T difference in the rear will make you travel FURTHER than the same ratio with 1T increase in front chainring (if that does make sence???)

These are now assumed values for explanation purposes

32x18; Distance per one pedal stroke =2m

32x17; Distance per one pedal stroke =2.7m

33x18; Distance per one pedal stroke =2.15m

 

I hope this helps.

 

I will try and find this mentioned chart online.

 

The bottom line is:

for a 2x9, get your fron chainring ratios closer than what they are.

 

Happy hooping

 

I hope it helps MORE than confuses...

[NINER_boy]

I hope it helps MORE than confuses...

 

Use the attached Track cycling chart as a refernce and explanation in what I tried to describe in words...

Track-Cycling-Gear-Chart.pdf

[Skylark]

I hope it helps MORE than confuses...

 

Stoked!! Thanks NINER_boy thats very helpful

A good point you made that I could rather increase the small chainring size to minimise the hole

[patches]

Stoked!! Thanks NINER_boy thats very helpful

A good point you made that I could rather increase the small chainring size to minimise the hole

 

yup! when I was deciding on my ratios, I read that 22T and 32T are a good combo, or 24T and 36T. I know my crank tech documents say not to put a 22T and 36T together.

[Skylark]

I reckon dropping 2 teeth on the big chainring to a 34t will sort things out pretty much perfectly - the ratio will be 1.545

But probably the most ideal is 24t - 36t thats exactly 1.5 ratio.....

But then again I've noticed that 36t is not very useable for the first 4 small cogs (unless flat or downhill) so having a perfect ratio with few useable gears is still not totally common sense.

I suppose thats why 10-speed is so kif , just gives you enough range to get the ratios etc on 2 chainrings up front just perfect

I only need to change my 36t ring becuase its stuffed but maybe I'll just replace the whole lot!!!

[Skylark]

I reckon dropping 2 teeth on the big chainring to a 34t will sort things out pretty much perfectly - the ratio will be 1.545

But probably the most ideal is 24t - 36t thats exactly 1.5 ratio.....

But then again I've noticed that 36t is not very useable for the first 4 small cogs (unless flat or downhill) so having a perfect ratio with few useable gears is still not totally common sense.

I suppose thats why 10-speed is so kif , just gives you enough range to get the ratios etc on 2 chainrings up front just perfect

I only need to change my 36t ring becuase its stuffed but maybe I'll just replace the whole lot!!!

 

Aye I'm a retard .... the first 4 small cogs are for flat or downhill riding , what goes up must come down

But I suppose thats the limitation of 2x9 - with 3x9 on a 32t middle ring the small cogs from cog 2 are useable in normal low speed manoeuvre riding or small uphills

 

The 36t onto the 11t cog is very fast on my Shova - scary fast , I actually want to go 34t so I cant go that fast . Its that speed where you know if you fall things will be very pear shaped and involve titanium pins and people talking softly to you from the side of your head

Edited January 18, 2012 by SkyLark

[Seadog]

I started running 36/26 with a 32 cassette.....changed to a 34 cassette and have now just ordered a 24 for the front. Mainly cross country and I think that's as close as i'm going to get to my perfect setup on 2x9. Next stop 2x10 with a 36.

Edited January 18, 2012 by Ride4yalife

[Skylark]

I started running 36/26 with a 32 cassette.....changed to a 34 cassette and have now just ordered a 24 for the front. Mainly cross country and I think that's as close as i'm going to get to my perfect setup on 2x9. Next stop 2x10 with a 36.

 

Where'd you get a 24t from?

I just found out now standard shimano 9 speed chainrings are 22t or 26t & 32t or 36t

24t & 34t doesn't seem to be easily avail

I use 104mm pcd 4 bolt middle rings

[Caerus]

Hi SkyLark

 

My advice would be to try and mimick the ratios and sizes of a tried and tested 2x10 ratios.

 

EG;

SRAM XX crainring ratio: 26 / 39 (your setup 22 / 36)

Now, this is a 1 x 1.5 ratio change between the small and large rings.

Thinking like this, your chainring ratio should be 22 / 33, and is far from that.

You increase the large ring T count to NOT run out of revs at top end, but in so doing increase the small blade / large blade ratios, witch in turn makes the ratio (and revolution ) jumps at the rear sprocket that much more accentuated.

 

Another issue you have is here;

11-12-14-16-18-21-24-28-32-36 (and this is a 10 speed cassette nuance)

 

You have a 9x setup, witch will make the jumps even bigger and earlier because you have one less gear.

 

So with your increased ratio jump at the Front, this will accentuate the ratio jumps at the rear sprocket as well.

 

My suggestion would be:

Get your F gearing ratios sorted as per 1 x 1.5 small and bigblade ratios.

 

Around 24 / 36 (if you want to keep the 36 bigger ring option for top end revs).

This will get the ratio difference at the rear down, and your gears "closer" to each other.

 

You will see that the difference in "granny gear" will be relatively unnoticeable.

 

Have a look at a chart of gear ratio calculations for track bikes and SS bikes.

Say all is measured in distance travelled per pedal stroke;

You will see that 1T difference in the rear will make you travel FURTHER than the same ratio with 1T increase in front chainring (if that does make sence???)

These are now assumed values for explanation purposes

32x18; Distance per one pedal stroke =2m

32x17; Distance per one pedal stroke =2.7m

33x18; Distance per one pedal stroke =2.15m

 

I hope this helps.

 

I will try and find this mentioned chart online.

 

The bottom line is:

for a 2x9, get your fron chainring ratios closer than what they are.

 

Happy hooping

 

Sorry to sound really ignorant here, but is it possible to explain in lay-mens terms what going on here with Gear ratios and the teeth on your cogs that you so expertly explained, cause that went way over my head.

Edited January 18, 2012 by Caerus

[Skylark]

Just got back from a ride now and I can see exactly why the ratio must be so close to 1.5

If the ratio is not almost spot on , the change up or down between front chainrings will also need a change up or down on the back cogs to maintain cadence - and doing that everytime is a load bollocks!!