Needing lower gearing, how best to do it?

[fossyant]

Yeah, just throwing in a useless fact about big sprocket capacities.

Mind you, "new" is a relative term, I got my R7000 5 years ago, so not all that new.

I'm running some old stuff. Got a 7402 rear mech on a 26T rear, and that's the most - I wouldn't try and push it more as there is a nat's 'whatsit' between the jockey and 26T sprocket teeth - super small cage. You can generally get away with another 2T on more modern mechs, or push it with a hanger extender.

 

[slowmotion]

I bought my 33t chainring from Spa Cycles, they have a couple of options;

https://www.spacycles.co.uk/m8b0s210p3055/SPA-CYCLES-110-BCD-Zicral-Middle-Inner-Chainring

https://www.spacycles.co.uk/m8b0s113p4730/SPECIALITES-T-A-X110-110-BCD-inner-33-44t-Chainring

Tweeks have the TA for £23.99;
https://www.tweekscycles.com/ta-zep...VzaNmAh2MnAfUEAQYAiABEgKDJ_D_BwE&gclsrc=aw.ds

Yep, Spa Cycles is an excellent place to find chainrings.

 

[steveindenmark]

Indeed, and potentially a very dangerous from @steveindenmark, as big - big combo hasn't changed.

What did I suggest that you thought was dangerous.

 

[T4tomo]

What did I suggest that you thought was dangerous.

potentially making the chain too short, so when they change onto big- big they destroy the RD and come crashing off the bike..

 

[Ajax Bay]

potentially making the chain too short, so when they change onto big- big they destroy the RD and come crashing off the bike..

To be fair @steveindenmark suggested changing "chainringS" and a smaller large ring would likely be OK with the chain 1" shorter (but the chain advice was superfluous). You could have made your 'dangerous' comment a tad less hyperbolic / more nuanced imho.

 

[steveindenmark]

potentially making the chain too short, so when they change onto big- big they destroy the RD and come crashing off the bike..

Your idea of "Danger" is very different to mine.

The chance of what you describe is remote. But you obviously know that by your exageration to press your point.

 

[Dogtrousers]

Your idea of "Danger" is very different to mine.

The chance of what you describe is remote. But you obviously know that by your exageration to press your point.

TBH if you were suggesting a chain that's shorter than can be handled in big//big then that is most definitely dangerous by any definition.

I'm not sure if you were or not tho.

Not that it matters really.

I've read that some pro MTB riders knowingly ride with short chains, but they are taking their own risks.

 

[DaveyA]

Thanks for all the helpful replies. I've been wondering about whether I should just swap the whole crankset for a 46-30. The original one is over 10 years old now. Is there anything that would be a straight swap into the BB30 bottom bracket?
The front mech is 105. I had a look at the rear mech, its a RD6700 Ultegra. As far as I can tell the space between the jockey wheel centres is about 60-62mm, and about and inch between the jockey wheels where the chain runs between.

 

[Ming the Merciless]

According spec, max cassette tooth capacity is 28t, which you already have. Thus a wolf tooth type addition, new RD, or change front are your options.

https://si.shimano.com/en/pdfs/si/5X90B/SI-5X90B-003-ENG.pdf

 

[Ajax Bay]

Thanks for all the helpful replies. the rear mech, its a RD6700 Ultegra. As far as I can tell the space between the jockey wheel centres is about 60-62mm

Love the category of reply qualification!
This is a short cage (SS) rear mech: its wrap and largest sprocket capacity is less than a GS version (c-c = 75mm).
Change of chainset is the way to go.
Bear in mind the FD will have to drop down the seat tube several mm: 2mm for every tooth less on large ring. Easy if clamp-on; check whether a limiter on braze on.

 

[DaveyA]

I have discovered FSA do a 46/30, its not BB30 so I would have to use an adaptor. Praxis and Rotor seem decent stuff so I think it might work ok. The FD is clamp on so I can move it down easily enough.