Audax gearing for Giant Defy - advice pls?

[andytheflyer]

Hi,

Done a few audaxes now on my 2009 Defy 2.5 (9 speed) and really enjoy it. But as a heavyweight (ex-rugby hooker and rower) I'm never going to be 70kg. I'd like to do some more 100-200k audaxes in my local Welsh Marches but most of them are up hills that I'll never get up with my current 50-38-30/12-27 setup. I need to fit some lower overall gearing. Not too bothered about the top end as I very rarely get into the big/small ring anyway.

Rode the Legend of Gelert on Sunday alongside a veteran and very experienced audaxer with a 24 inner ring and what looked like a preposterously long RD cage. I can climb up to about 10% for a short distance but I have to spin as a spinal cord injury restricts my ability to stand on the pedals for more than a very short distance - but I am reasonably fit.

Seeing an earlier post on here from @Ian H he has a 46-36-26 chainring setup and I could do that. I think my braze-on FD has enough travel to go a bit lower down the seat tube. Using Sheldon's calculator, if I had a cassette with at least a 30T (say 11-30) that would get me down to a 23" bottom gear. That would be OK I think. Current bottom gear is 29".

I think that means I need to change my Tiagra RD (with a jockey wheel spacing of 74mm) and a maximum tooth capacity of about 27 (?) to an MTB RD with a longer (84mm) cage (say a Deore).

Given that I have Tiagra shifters, will the Deore RD work with the STi's? Looking at an earlier thread on here (https://www.cyclechat.net/threads/rear-mech-problem.174107/#post-3525436) it seems that I can do this.

Have I missed anything here - anything else I need to consider? (Like, will I need a different hanger?)

 

[jowwy]

Hi,

Done a few audaxes now on my 2009 Defy 2.5 (9 speed) and really enjoy it. But as a heavyweight (ex-rugby hooker and rower) I'm never going to be 70kg. I'd like to do some more 100-200k audaxes in my local Welsh Marches but most of them are up hills that I'll never get up with my current 50-38-30/12-27 setup. I need to fit some lower overall gearing. Not too bothered about the top end as I very rarely get into the big/small ring anyway.

Rode the Legend of Gelert on Sunday alongside a veteran and very experienced audaxer with a 24 inner ring and what looked like a preposterously long RD cage. I can climb up to about 10% for a short distance but I have to spin as a spinal cord injury restricts my ability to stand on the pedals for more than a very short distance - but I am reasonably fit.

Seeing an earlier post on here from @Ian H he has a 46-36-26 chainring setup and I could do that. I think my braze-on FD has enough travel to go a bit lower down the seat tube. Using Sheldon's calculator, if I had a cassette with at least a 30T (say 11-30) that would get me down to a 23" bottom gear. That would be OK I think. Current bottom gear is 29".

I think that means I need to change my Tiagra RD (with a jockey wheel spacing of 74mm) and a maximum tooth capacity of about 27 (?) to an MTB RD with a longer (84mm) cage (say a Deore).

Given that I have Tiagra shifters, will the Deore RD work with the STi's? Looking at an earlier thread on here (https://www.cyclechat.net/threads/rear-mech-problem.174107/#post-3525436) it seems that I can do this.

Have I missed anything here - anything else I need to consider? (Like, will I need a different hanger?)

Friend of mine has the same bike - he changed his front crankset for a 48-38-28 and the rear cassette for 12/30 tiagra and was as happy as larry

 

[andytheflyer]

Friend of mine has the same bike - he changed his front crankset for a 48-38-28 and the rear cassette for 12/30 tiagra and was as happy as larry

Thx for that @jowwy - reassuring.

After doing a load more research, I ordered a long cage 9 spd MTB RD (XT) and I'll try that with an 11-34 spare cassette I have off my 'bent. May well stay with a 30T on the back and use a 28 on the front though. My research showed that the std Defy RD would not handle a 30T rear - but maybe it can.

 

[andytheflyer]

Finally got to a setup that not only works but also works for me. Since there are regular threads on here about getting lower gearing, and many replies are necessarily of the "it might work - you'll have to try it" variety, I thought I'd write up what I did so that anyone doing a search may find my results.

I'm a fairly big lad, (61yo, 100kg, ex-rugby forward and rower) and never going to look like Chris Froome. I'm no grimpeur, nor a sprinter, but I am fairly fit and a 100 mile day is no big problem. After spinal surgery in 2010 I now have balance issues and my leg control is poor - lots of power, but it means I can't dance on the pedals to get me up a hill for more than about 50m - I have to sit and spin. So, I need low gears. (and a recumbent!)

After trying the 11-34 cassette with the 50/38/30 up front, I thought it worth trying a 12-36 cassette. That works fine with the XT long cage MTB mech. It's a long MTB mech cage, which is longer than a long road mech.

Went off to the Dales for a few days and tried out some of their hills with the 12-36 - there aren't many in my part of Cheshire. I was certainly able to get up roads with a single arrow on the OS map (so 1 in 5 to 1 in 7) (like Barden to Embsay) but there was no way I was going to get up anything steeper than 1 in 5. So the road from Keld to Tan Hill wasn't going to happen. And Park Rash was never on my bucket list anyway. However, a 14% was still bl**dy hard work.

So, I then tried a 26T on the front (so now 50/38/26). There seemed to be plenty of spare capacity in the front mech cage length to accommodate the smaller granny ring, and so it proved. I reckon it could even take a 22T if you could find one with the right BCD.

Just been out around my local short sharp hills in and out of a steeply incised valley and I can easily spin up a 1:5 without getting out of breath. Doddle.

So, the upshot is that a standard road bike - a 2009 9 speed Giant Defy 2.5 with STi levers, and a Shimano Tiagra groupset, can easily be modified to get down to a 19" bottom gear by using a large cassette (12-36) and fitting a small (26T) granny ring. I needed an MTB long cage rear mech too. I also changed all the gear cable inners and outers for Shimano SiS kit. Spa Cycles have all the chain rings you'll ever need!

The drawback is that (inevitably) there's some big jumps in the rear cassette - like 28-32-36. That means that you have to be more sensitive to the steps. Looking at Sheldon Brown's gear calculator, I could see that a reasonably smooth transition through the cassette could be achieved but only by more intelligent use of the front mech. So, the lowest 3 gears go with the granny, the middle 3 with the 38T and the top 3 with the 50T. You can move the boundaries a bit, but you end up with some uncomfortable steps - but that's the price to pay. Cross-chaining is definitely out. The rear mech will, however, cope with the extremes of small/small and large/large - so that's a cracking bit of kit.

Hope that helps someone else. Now I can pick some of the hillier audaxes!