Lowering gear ratios for Audax - potential pitfalls?

[badgerjockey]

Hi all,

I love my new bike, a candy apple red Genesis Equilibrium 20. It's been custom built, setup with SRAM Rival groupset apart from my old Shimano 105 34/50T chainset and chain.

It's such a comfortable ride and I am thinking about doing some Audaxing, however it is still a bit of a pig up the big hills sometimes seen in Audaxes and Sportives (and just generally for everyday riding around the Mendips!). So, I'm thinking about sorting out my gear ratios but have not done this before for a road bike and would appreciate your advice....

My casette is a 11-25T SRAM PG1070 and I have the short cage SRAM Rival derailleur of course.

My thinking is to switch this for a 11-28T same model cassette and possibly to switch the inner chainring for a 30T option. This would leave me with a low gear ratio of 1.07 which is fine for me and the hills. It is currently 1.37 and I have to get off and push up the biggies.

Can anyone think of potential problems in doing this?

-Will I need to change chain length?
-Will I need to change to a long cage derailleur?
-Will the shifting become a lot less smooth?
-Will chainging the chainring muck anything up?
-Will this make shifting to the 50T chainring horrible?
-Am I being too pedantic as it probably wouldn't make much difference?

Any thoughts would be welcome,
Cheers!

H

 

[Banjo]

You could look into fitting a Sram Apex rear mech and cassette which has a 32 tooth largest cog .with that you could leave the chain rings as they are.

I have a 30 tooth ghranny ring on my shimano 105 bike and changed the cassette from an 11 -25 tto a 11-28 which helps a lot on hills when tired .


PS just looked at the bike on online adverts etc, what a beautifull bike.

 

[asterix]

The step from 30 to 50 is too large in my experience. I'd agree with Banjo's idea although I don't know how the short cage derailleur would manage. Sounds a bit iffy.

 

[TheDoctor]

The smallest inner ring you can fit on a compact is 33T, so fitting a 30T won't work.
SRAM shifters won't do a triple, so that's out as an option.
As above, your best bet will probably be the Apex cassette and rear mech.

 

[Riding in Circles]

I would leave the front but go for an 11-32 rear with a mid cage derailleur, you will need a longer chain.

 

[badgerjockey]

OK, understood.

However, I love my Rival rear mech, its a great piece of engineering.

What would I be losing by stepping down to Apex?
I suspect the shifting would be chunky and clunky with the apex longer cage and the wider gearing of the 11-32T?

 

[RecordAceFromNew]

Why limit to Apex cassettes? Practically all current Sram and Shimano (and Shimano compatible) 10 speed cassettes are eligible, for the OP's purpose if I were him I would look from the mtb ranges.

Regarding rear mech choice, I would expect all from Sram's Exact series are eligible, it is a matter of deciding what maximum rear sprocket size requirement is/will be, and work from there, or alternatively play safe and get any mtb 10 speed X series rear mech, which should handle anything up to 36T at the back.

I agree with the others that changing cassette rather than the chainset is the preferred solution.

Rear shifts should always be smoother than front shifts. The reason is rear shifts derail a chain that is only under spring (i.e. rear mech cage spring) tension, while the front shift has to derail a chain under pedal tension, and with significantly larger tooth difference between adjacent rings.

You will need a new, longer chain.

 

[lulubel]

This won't be any help to you, but it might help others reading this thread and trying to choose between different chainsets, so I'll say it anyway ....

This is why I always recommend a triple (unless all your rides are going to be pretty flat). So much more flexibility at both ends of the gear range.

The advice others have given you is pretty good, I think. A friend of mine who lives in the Alpujarras (which includes the Sierra Nevada ski resort) has the 34/50 11-32 setup, and she doesn't have to get off and push!