options for 6600 39/53 9 speed? Switch to compact or replace cog?

peanstein

I'm not too experienced with this and have come up with bits and pieces about options when it comes to swappoing out the rear cog.
I'd like to either convert to a compact crank or replace the rear cog to give me similar gearing a compact would(if that's even possible)

I think if switching cranks, I think I'd need a 6650 correct and new cog? what about rear derailleur?
If I have the option to simply get a new cog w/different gearing, what options do I have?

Knees are not what they used to be and need to ease the burden on them by spinning a bit easier up hills.

Any help would be appreciated.

Wirral_paul

Well worth doing to make life easier in the hills - no point struggling with big gears (and especially you should ignore the "advice" from anyone who says you should stick with 53/39 just because that's what racing bikes are supposed to come with). I'm a strong rider but have deliberately specified a 50/34 on my new bike with my local hills being STEEP!!

Worth looking at the 6750 chainset also - both 6650 or 6750 should be a straight swap. You'll need to take a link or two out of the chain too though

ugo.santalucia

What I did with Shimano 9 speed was to replace the rear mech with a MTBike 9 speed one (needs to be 9 speed) and then use MTB cassettes, which give you up to 36 T capacity... 39 x 36 is a pretty small gear.

Bear in mind MTBike derailleurs have no barrel adjuster, so you need an in line barrel adjuster too, not a big deal, but worth pointing it out... it's less expense than a new chainset, as the RD is 20-30 quid and a 9 speed cassette is 10-15... the barrel adjuster is 5 quid or so

jomoj

+1 what Ugo said. FYI Chain Reaction have the MTB 9 speed XT derailleur for £35 at the moment. That would do the trick and will work for road 9&10 speed.

http://www.chainreactioncycles.com/mobi ... -prod20700

peanstein

Thanks for the info.
I found a similar post talking about a MB RD so before I swap out to a compact crank I think I'll go that route to see if it works. I guess I'm in a bit of luck since my current 6500RD is a GS and might be able to just use that?
The cassette I have is a CS6500 12 T Type- http://si.shimano.com/php/download.php? ... -1680A.pdf

I took the cassette apart and replaced the last 3 gears that are together (#11) and replaced them with the last 3 gears of a 10 speed that I have. It fit and shifted but was a bit tight so will go back and try adjust the B Adjust since the bottom gear on the RD was almost touching the cassette.
A also had to add the spacer (1mm) that goes on behind the 10 speed cassette so the 9 sp. cassette would fit correctly.
I might need to add a tooth or two to the chain as well.

Is this an acceptable swap or the fact that it's from a 10 sp. cassette a deal breaker?



This is one of the reads I found on a different forum.


The 6500 SS and the 6500 GS have the same large cog limit of 27 teeth but that limit can usually be extended up to 30 or possibly in some cased up to 32 teeth. The 6500 GS has a long cage and a greater chain wrap capacity. A Shimano mountain bike 9-speed rear derailleur will work perfectly with the 6500 shifter and will definitely work with a big cog up to 34 teeth. A Shimano 10-speed rear derailleur is not compatible with your 9-speed shifters due to a change in actuation ratio. A 9-speed Shimano rear derailleur and 12-32 or 12-34 9-speed cassette would work well for you. The ratio jumps and cadence jumps with each shift will be pretty big but for a serious mountain ride it may be the best choice. A 9-speed SRAM cassette will also work with the Shimano 9-s mountain RD.
With a mountain cassette you will also need a longer chain.

jomoj

The capacity of the RD6500 is 37T and the max sprocket size is 27T - its a rear mech from the triple chainset era really so big sprockets on road weren't really a thing then.

Using the power of maths and assuming you have a cassette with a 12T smallest sprocket then an RD with a capacity of 37T would allow you to use a 34T sprocket with your 53/39. That's a pretty good gear but the limitation is going to be the max sprocket size of the RD. They tend to be conservative - I use a short cage Shimano mech of max 28T with a 32T sprocket and its ok but I think you might struggle with the one you have.

I'm a fan of tinkering around with swapping bits to get things to work but my advice here would be to splash out on the mech, chain and cassette and save yourself the faff. A SGS shimano MTB mech would do the trick and any of these in long cage version will suit

Deore m591 / 592
XT m771 / 772

. SRAM or shimano cassettes & chains will all be compatible with this set up too.

peanstein

jomoj,
You are right .
It will almost work but I can't get the shifts to be perfect(close)since the 3 large cog piece I am using from the cs-6700 has spacing a tad bit slimmer than the 9 speed 12-25 cog I have. It skips a gear sometimes when it transitions from the 9 speeed gears to the 10 speed gears.

Can I use the 10 speed cog i have(CS-6700) on the MTB mech (XTm77x)? Or does the cog have to be a MTB one?

nm, saw you said long cage...
Oh yeah, the link you posted shows the SGS and GS version, which would I want? I think the longer cage but want to be sure.


Thanks again for the help.
Learning is part of the fun, the rest is doing the work and figuring stuff out.
Victor

jomoj wrote:

The capacity of the RD6500 is 37T and the max sprocket size is 27T - its a rear mech from the triple chainset era really so big sprockets on road weren't really a thing then.

Using the power of maths and assuming you have a cassette with a 12T smallest sprocket then an RD with a capacity of 37T would allow you to use a 34T sprocket with your 53/39. That's a pretty good gear but the limitation is going to be the max sprocket size of the RD. They tend to be conservative - I use a short cage Shimano mech of max 28T with a 32T sprocket and its ok but I think you might struggle with the one you have.

I'm a fan of tinkering around with swapping bits to get things to work but my advice here would be to splash out on the mech, chain and cassette and save yourself the faff. A SGS shimano MTB mech would do the trick and any of these in long cage version will suit

Deore m591 / 592
XT m771 / 772

. SRAM or shimano cassettes & chains will all be compatible with this set up too.

ugo.santalucia

You can use any cassette you want with a 9 speed MTB derailleur, but the clearance is designed for bigger sprockets, ideally with a maximum sprocket of 34 or 36

peanstein

ok,
I'm buying the M591 since it has the barrel adjuster already on it.
I'll also get a pg-1070 12-32t cassette and see how it rolls.

switching gears a bit... can I fit the pg-1070 12-32t on my other bike that has a DI2 setup currently running a 34/50 & 12-30 CS-4600?


Thx to all for the tips!

ugo.santalucia wrote:

You can use any cassette you want with a 9 speed MTB derailleur, but the clearance is designed for bigger sprockets, ideally with a maximum sprocket of 34 or 36

Wirral_paul

Dont you need to stick to a 9spd cassette for this bike? The PG-1070 is a 10 speed and so would need 10spd shifters.