I have a Caadx with 46 36 chainring up front and 12-28 in the back with a 105 derailleur. The gearing is a bit stout for some of the hills I encounter on road rides. What would be the best way to go? Go to 12-36 in the rear or change out the 36 for a 34 or even a 32. Would the rear derailleaur be able to handle going from a 28 to a 36?
Gearing question
Smilerz
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I have a Caadx with 46 36 chainring up front and 12-28 in the back with a 105 derailleur. The gearing is a bit stout for some of the hills I encounter on road rides. What would be the best way to go? Go to 12-36 in the rear or change out the 36 for a 34 or even a 32. Would the rear derailleaur be able to handle going from a 28 to a 36?
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36x28 should be enough to handle anything worth riding on a cx course. If it's too steep for that, running will be faster.
I use my CX bike for road also. 34 on small ring w 12-28 for me. 150lbs kitted up. Got forced up to Cat3 after Cat 4 wins last year (not bragging just saying fairly strong rider and w/low weight my strength is climbing. Lived in Cicago area at time)
maybe this will help you for starters - with 2x setup you are probably a short cage (3x = long)
Will Shimano 105 rear derailleur accept sram 12-32 cassette?
I prefer tight ratios (ex 32f w/ 11/32 casette on mtb), but to each their own, not sure how much gearing you may need. Front derailleur can only handle so much of gearing difference,
This can help you calculate mph in certain gear combo's at certain rpm's to get idea of what you want.
Sheldon Brown's Bicycle Gear Calculator
On above forum, readers are running 32-11 in rear, you could try that, but by sounds of it, you will make change in front also (34 or 32t)
maybe this will help you for starters - with 2x setup you are probably a short cage (3x = long)
Will Shimano 105 rear derailleur accept sram 12-32 cassette?
I prefer tight ratios (ex 32f w/ 11/32 casette on mtb), but to each their own, not sure how much gearing you may need. Front derailleur can only handle so much of gearing difference,
This can help you calculate mph in certain gear combo's at certain rpm's to get idea of what you want.
Sheldon Brown's Bicycle Gear Calculator
On above forum, readers are running 32-11 in rear, you could try that, but by sounds of it, you will make change in front also (34 or 32t)
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Agree with this. On the road 36x28 is insanely low gearing. Not too long ago a 42x24 was considered a low climbing gear.
Not trying to get into pissing match, but...
1. This is not answering OP's question. (We have no idea what climbs are, his age or state of fitness.
- its irrelevant)
2. There are plenty of road bikes out there with triple ring cranks w/30t for granny ring
You may be better served posting this in
Drivetrain - shifters, derailleurs, cranks - Mtbr.com
Or
Bicycle Mechanics
I put a set of 46-34 chainrings on one of my CX bikes last winter to use it as a gravel grinder. To my surprise, this setup also works really well for CX racing -- you just have to change your thinking from "small ring default" to "big ring default." I've done six races this year when I didn't use my small chainring at all.
But more to the point here, changing from a 36T small ring to a 34T small ring only drops your lowest gear by about 6%. It is, however, a very inexpensive change. You can get a 34T ring for under $15.
You wouldn't be able to use a 32T ring on that crank. I think someone makes a 33T that would fit, but they're very uncommon.
We'd need more information to know what your rear derailleur can handle. Shimano makes a 105 RD that will work with a 32T big cog on the cassette (and you could probably get away with 34), but if yours is a short cage model then 28T is specified maximum.
If you do have the medium cage model, changing to an 11/12-32 cassette would give you a 14% drop in your lowest gear without changing the small chainring, and if you change the cassette and the chainring you should have a low gear that will get you up some truly beastly climbs on pavement.
My suggestion would be to change the chainring first and then if you still find yourself wanting a lower gear consider a 12-32 cassette.
But more to the point here, changing from a 36T small ring to a 34T small ring only drops your lowest gear by about 6%. It is, however, a very inexpensive change. You can get a 34T ring for under $15.
You wouldn't be able to use a 32T ring on that crank. I think someone makes a 33T that would fit, but they're very uncommon.
We'd need more information to know what your rear derailleur can handle. Shimano makes a 105 RD that will work with a 32T big cog on the cassette (and you could probably get away with 34), but if yours is a short cage model then 28T is specified maximum.
If you do have the medium cage model, changing to an 11/12-32 cassette would give you a 14% drop in your lowest gear without changing the small chainring, and if you change the cassette and the chainring you should have a low gear that will get you up some truly beastly climbs on pavement.
My suggestion would be to change the chainring first and then if you still find yourself wanting a lower gear consider a 12-32 cassette.
Your crankset uses 110 BCD rings. This 34T ring will fit it:
Universal Cycles -- Shimano FC-6750 Ultegra Double Chainrings 10spd
As for the rear derailleur, there an RD-5700-SS, which is the short cage model, and an RD-5700-GS, which is the medium cage model, but also an RD-5700A-GS. The model number is imprinted on the inside of the derailleur body.
Shimano's specs say that 28T is the maximum cog size for both the RD-5700-SS and RD-5700-GS, but 30T for the RD-5700A-GS. I think you could probably make a 32T work with either of the GS models, but it's possible that you'd have issues with the top pulley being too close to the big cog.
I am curious what class you race with only using your 46t up front?
Believe it or not, I'm a bottom 10% Master C racer.
I'm using a 12-28 cassette, so my bottom two gears with the big ring, 46-28 and 46-24, are roughly equivalent to 36-21 and 36-19, which are fairly low gears, right? The 46-24 combination is 52 inches. If I stay there very long I'm sight-seeing off the back.
The six races I'm talking about were pretty flat (4 Blind Dates, Het Meer and Heiser Farms for those in the OBRA area). At a few other races I dropped onto the small ring for a couple of hills, and one race had a pair of long hills that were wearing me out so I ended up spinning the 34T all day and finished WAY off the back (the Achilles' heel of this gearing).
The thing that really makes the 46/34 work when used with a mindset of trying to stay in the big ring is that as long as you're in the big ring your gearing goes up quicker but not so much quicker than it would with a smaller ring that you notice it being hard.
For example, let's say I'm pushing up an incline in the 46-28 gear (44.6 gi). That's slightly lower than a 36-21 (46.6 gi). Then the slope starts to level off so I shift up a gear to 46-24 (52.1 gi vs. 51.5 for 36-19). Finally, I hit something flat and shift up again to 46-21 (59.5 gi vs. 57.5 for 36-17). So with the same psychological process of nudging up a gear at a time when I could, I essentially got two gear inches for free. And as long as I maintain the same cadence I normally would that's free speed.
Note that what's happening here isn't that my legs magically got stronger. It's that I tricked my mind into using a higher gear than it would normally want to.
By this point you're probably thinking that I'm spending an awful lot of time cross-chaining (and if you're a roadie it's probably making you twitch). I have two answers for that. First, it cyclocross and my chain is destined for a short life anyway. Second, I'm using the Gevenalle HOUP, which pushes all my cogs over by one slot so except for the 46-28 combination (which I want to try to stay out of anyway) it's not that bad.
By the way, this may sound ridiculous coming from a duffer like myself, but the idea of using a 34T small ring has the stamp of approval of no less a racer than Katie Compton.
She's uses a 42T big ring, which would be more than enough for me too (obviously), but I can't justify springing for the very nice WickWerks chainrings so I just live with the wasted top end gears. Maybe I can get a second HOUP and ditch my 12T cog too.
Thanks for detailed answer - I guess there is more than 1 way to skin a cat.
So far I always stayed in 34t. I won Cat 4 open races in Chicago series and got bumped up to 3's. The one race in 3's I entered i ended up 19th after being staged 63rd. I have a teamate that top 10's in 35+ and he is somewhat faster than me on mtb (we never went head to head on road or CX)
Maybe I'm a spinner? Sheldon Browns gear calculator says 34f/12r = 20.5mph @ 90rpm
So far I always stayed in 34t. I won Cat 4 open races in Chicago series and got bumped up to 3's. The one race in 3's I entered i ended up 19th after being staged 63rd. I have a teamate that top 10's in 35+ and he is somewhat faster than me on mtb (we never went head to head on road or CX)
Maybe I'm a spinner? Sheldon Browns gear calculator says 34f/12r = 20.5mph @ 90rpm
Yeah, so in that sense I could just about go 1x10 with a 34T ring. My problem is that I'm mentally lazy and have a bad habit of drifting into my lowest gear and staying there. Thinking of the big ring as my default forces me to make a decision to drop into the really low gears.
You said you like tight gearing, so going up the ladder with a smaller ring is probably better for you. I tend to need more of a nudge, so the bigger gaps with the bigger ring gives me a little incentive to ramp up the speed after I shift, because I also like to keep a higher cadence.
I run a 33/46 rings and a 12-30 cassette on my gravel/CX rig. Love the super low gears on the gravel, but the 33 is pointless for CX or pavement unless there is a wall to climb.
TA specialties makes the 33 chainring. As mentioned before, they aren't common, 32's don't exist since they simply won't fit. And I end up with a "big ring default" when doing CX races and training.
TA specialties makes the 33 chainring. As mentioned before, they aren't common, 32's don't exist since they simply won't fit. And I end up with a "big ring default" when doing CX races and training.
Why would you like small ring in gravel, but not CX?
What class are you in?
When racing CX, where do you think you are at usually in your casette?
I run the big chainring and the middle to big side of the cassette during the cross races so the chain is tighter and less likely to come off. Yes, I end up cross chained.
Racing Cat 5 for now. Won yesterday's race. Hope today's race goes as well.
The 33 chainring is useful on gravel for the extended climbs. CX races don't have extended climbs.
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The only number I can see on the derailleur is 5701?
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I won't be racing cross. I am 60, ride MTB 2-3 times a week. I will be using the Caadx to ride mostly road and we have some steep climbs in Norcal. Would a MTB derailleur work on the rear?
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54 here. I run a 42/30 up front using a converted ultegra triple , a 11-32 cassette, sti shifters and xtr short cage RD. Its nice to not run out of gears.
I missed that one.
Shimano doesn't have the usual specs for it on their tech-docs page, but other online sources seem to indicate it will work with a 32T cog if it's the GS version and 30T if it's the SS version. The difference between these is the length of the cage (between the pulleys) and you should be able to judge it visually. The SS version will only have about a finger width of space between the pulleys.
You can use a 9-speed Shimano MTB derailleur, but SRAM MTB derailleurs and 10-speed Shimano MTB derailleurs won't work. If you get a "shadow" type derailleur, you'll need an inline barrel adjuster somewhere.
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