Gearing Advice

by hurns   March 12, 2013  

Hi All,

So I finally bought a new bike (Cervelo R3) that I found on ebay but need some help / advice on changing the current gear ratios.

It has come with full campagnola athema carbon groupset with 53/39 chain set and 11 speed 11 - 25 cassette.

My other bike had a triple chain set so this race set up is a little shock to the system and I simply dont have enough gears to get up the steep climbs I’m training on.

I'm 6 foot 2 and weight around 235 pounds, so not the smallest or lightest of riders. But the big ring on the new bike is a lot of fun and fast on the flat!

I'm currently training for the Wiggle Dragon ride (127 miles and 3500m of climbing) and so want to get a new gear set up to cope with this.

This is a link to the bike if you need to see the componants

So my questions are:

Can I get away with just a new rear cassette? If so what ratio would be best? Do I need to change anything else if going for a 12 - 29, like the chain or rear derailleur?

Would it be an option to change just the bottom chain ring and keep the 53 or is not the done thing? Again would I need to change anything else?

Any help would be great as I really don’t know much about gears or campagnolo.



19 user comments

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Normal solution is to get a compact chainset. Not sure with Athena, you may simply be able to get 2 new chainrings or you may need a whole new chainset....

posted by jimmo62 [59 posts]
12th March 2013 - 17:52


Hi, glad to hear you are enjoying the big ring experience, even the hilliest event has a lot of flat and downhill so stick with it, you don't want to be spinning out when there is juice in the tank. Okay advice...
1.) your link is broken, I am sure you have a sweet ride.
2.) here is a link to a thread I started last year when I was struggling with a particularly steep local hill:
There is a lot of advice from some wise posters on there about just how big a back cassette you can fit on a normal cage. You can get long format ones if you really want a big back ring but for most hills a long cage is not needed and a lot of fuss and cost to get. I would just say if you do get a new back cassette make sure you are not loosing too many teeth at the top end as well 11 down to 12 might be worth it if you need the 29.

I am stronger than Mensa, Miller and Mailer, I spat out Plath and Pinter.

bikeboy76's picture

posted by bikeboy76 [1434 posts]
12th March 2013 - 17:58


You could get away with just the cassette.

But the other option is keeping what you have and changing the crankset. I dare say you'd get a good price for your standard and then change to one of the compact options which seem to be

34-50, 36-52

Gkam84's picture

posted by Gkam84 [9040 posts]
12th March 2013 - 17:59


Sadly the Athena only offers a 12-27 cassette so a change of the main chainset may be in order.
You could go standard compact 50/34 or go 52/36 which would deliver you close to current top end speed.

Have a look here for your options

posted by Gazmanmeister [3 posts]
12th March 2013 - 18:06


Thanks for the links and advice.

Instead of changing the whole chainset can I just change the bottom ring to a 36 or 34? Leaving the 53 on it.

The chainset has screws not revits so it looks like they can be changed?

this link should give you an idea of what chainset is on it at the moment.

Thinking definitely need to change the rear cassette to an 12 - 29.



posted by hurns [9 posts]
12th March 2013 - 18:17


Maybe changing the cassette to something like an 11-28? Or go compact? Personally I'd go for cassette change Smile

posted by Cycle_Jim [282 posts]
12th March 2013 - 18:22


Nice, here is a ratio tool to give you a calculation:

A bigger cassette is a cheaper option than a new crankset. Changing a single ring is possible but more tricky than the whole set actually, the rings can require special tools.

First thing you need to establish is what size your rear mech can manage as some can only go up to 28. 29 or 32 might require the long cage.

I am stronger than Mensa, Miller and Mailer, I spat out Plath and Pinter.

bikeboy76's picture

posted by bikeboy76 [1434 posts]
12th March 2013 - 18:30


Okay, okay, I am getting all exercised about this:

What you have: 39/25 to 53/11 = 1.6 to 4.8
With a compact: 34/25 to 50/11 = 1.4 to 4.6
With a cassette: 39/28 to 53/12 = 1.4 to 4.4
With both: 34/28 to 50/12 = 1.2 to 4.2

so a compact crankset will cost more and cut your top speed more for the same 1.4 ratio, and if you can squeeze more than a 28t cassette on the back it will be even more in its favour. Start with the cassette then see if you want to think about the crankset.

I am stronger than Mensa, Miller and Mailer, I spat out Plath and Pinter.

bikeboy76's picture

posted by bikeboy76 [1434 posts]
12th March 2013 - 18:45


I'm not going to be the only one thinking it and as a "known" figure around these parts.

Its falls on my shoulders....... Devil Devil

Is your stem not a bit erm.....angled Wink

Gkam84's picture

posted by Gkam84 [9040 posts]
12th March 2013 - 19:04


New cassette to start it is then!

Thanks Gkam84 for the observation, I was thinking the same thing, when I bought it he had it the other way round as he raced vet races on this bike.

Think a bike fit is in order too!

posted by hurns [9 posts]
12th March 2013 - 19:28


Yeah the other way round would look about right, I think you will need to change the stem out for something else, it just looks wrong.

Bike fit would be a good idea first Wink

Gkam84's picture

posted by Gkam84 [9040 posts]
12th March 2013 - 19:34


To get a similar range of gears to the triple I had previously, I went with 34-50 compact and 12-29 cassette, lets you go up hills whilst in training mode.

To get 12-29 cassette in campag 10 speed, I had to buy a 13-29 and a 12-25 and mix them up

posted by jengy [67 posts]
12th March 2013 - 21:28


That's a nice bike but perhaps a bit racy for the OP hence flipping the stem? I see it was normal way around on the Ebay ad. The Dragon Ride was quite lumpy last year with one particularly steep climb which I say many walking up so a low bottom gear is definitely needed by lesser climbers. I'd say switch both the chainset to a 34/50 and cassette to 12/27 at least. As a Shimano guy I don't know if you need to change to a longer cage rear mech with yours but I guess you would for a 12/29 cassette.

posted by mudshark [36 posts]
12th March 2013 - 23:24


I would change the stem! that will make it easier to climb, I ride here in taiwan with some big mountains with a 12-27 cassette, its not easy on the big climbs sometimes but its doable. Just practice more and get fit before do the final change to a wider range cassette.

posted by guyondebike [34 posts]
13th March 2013 - 0:44


This is the best calculator....,38,52&RZ=14,16,18,21,24,28&GR=DERS...

The OP is sixteen stone and riding hills. His gearing is that used by elite athletes weighing 30% less. Whippets on here might try loading their bikes with brick-filled panniers and using the same gearing to understand the point.

I think any concern about losing top end speed is way wide of the mark. A cadence of just 90 gives 35mph with his current set-up, and going 50/36 and 12-29 only reduces this to 30mph. He shouldn't be spinning out until he hits 40mph at 120RPM. That isn't the problem.

I know Shimano and SRAM and not Campag, I'm afraid, but I'd be looking to change the cassette to 12-29, and the front to 50/36. Note this is not the more common 50/34 for two reasons. The fourteen-tooth front difference is close to the existing making double-shifts easier and ensuring the front shift is not compromised. It also puts most of your gears and your smallest increments between 16mph and 22mph which I would expect to be your cruising speed.

For the hills this gives you two gears below your current bottom gear of 41", at 37" and 32". This still isn't really low, but there is a point on a road bike where you do have to HTFU. But it is quite a bit lower than at present.

I'd hope it was possible just to change the rings and cassette to acheive this, but you'll need a Campag fan or a good LBS to advise. If the stated capacity of the mech is max 12-27 you can usually get away with an extra tooth or two unless the derailleur is hung very close to the axle. Since the front gets smaller while the back gets bigger you may even get away with using your existing chain if it isn't worn.

posted by Malaconotus [48 posts]
13th March 2013 - 9:41


guyondebike wrote:
Just practice more and get fit before do the final change to a wider range cassette.

Easier said than done, which is why the Martin is asking the question.

I would swap the chainset for a compact and get a 27 or 29t cassette. He's said he's no mountain goat and that's a really nice bike so why scrimp on a chainset? No point spending money on riding the Dragon (and future hilly rides) if you end up struggling and walking.

@bikeboy76 - top speed is not his priority. In the real world dropping 3 teeth on the big ring is not an issue for anyone outside the pro ranks.

Simon E's picture

posted by Simon E [2059 posts]
13th March 2013 - 10:11


I agree with Simon.
It's an expensive approach but if you want to ride the Dragon on your new bike then it is probably what you need.
Alternatively, save the Cervelo for sunny days on the flat and ride the Dragon on your Cannondale. You won't run out of gears on the triple and you'll save a lot of money too. Keep riding and have another crack at the Dragon on your new bike when you are 180lb. Happy training and good luck with the ride in June.

Ah! Condor

posted by Bedfordshire Clanger [329 posts]
13th March 2013 - 13:38


Some great advice and thanks all for taking the time to respond.

Been training now for the past year and have dropped over 3 1/2 stone in weight, still no "whippet" but getting there. The turbo, sufferfest, trainer road and long hilly rides have been the key!

Im only 32 so a bit ashamed that i'm not as flexible as the vet racer I bought the bike from but have a bike fit at Cadence booked in for the 26th and will surely swap out the stem.

In the case of gears im going to order an 12 - 29 and see how I get on. May then purchase a campact 50 - 34 chain set for the dragon or ride the cannondale.

Once again thanks for the amazing advice!

posted by hurns [9 posts]
13th March 2013 - 16:29


It looks like it's been quite a year for you. Congratulations on the weight loss, keep up the good work. Another year like the last one and you'll really be flying.

Ah! Condor

posted by Bedfordshire Clanger [329 posts]
13th March 2013 - 20:17