Bike gearing suggestion, 52/36, 11/28, want slightly lower gear(s)

Hello, I am looking for some help on where to start.
I have a Cervelo S3 that’s a few years old, Ultegra drivetrain.
I have a 52/36 up front and an 11-28 rear cassette. I did my biggest ride yet yesterday (122Km, 2,588m elevation gain, about 5 hours 20 min).
I was climbing with a cadence in the low 70’s mostly in my easiest gear. I dipped in the high 60’s in the toughest sections but that didn’t last long.
I think this cadence is lower than ideal?
I am thinking my sustained cadence while climbing should at least be in the mid to upper 70’s?
Higher?
I am wondering what my options are and what option is “best”.
If I want a 30 or 32 in the back do I get an entire new cassette or do I just get the 30/32 cog?
I think I may have troubles going bigger than 28 without some modifications?
I could go smaller in the front but would I replace both chain rings or just get a smaller, small chain ring?
In general the riding I do is mixed.
I rarely run out of hard gears and only go into the hardest on descents.
I would probably get more use out of a gear or 2 that are easier than what I would lose if I lost a gear or 2 at the top end (if I described that correctly).

Edit: I do hope and plan for my fitness to improve as well. I am at 3w/Kg currently, maybe slightly higher at my ramp test next week. I would love to get to 4w/Kg but that may be a stretch goal at 46 and mid volume time commitment, consistently, year round, is tough, but I am trying.

I just got a brand new chain and full prepared it for waxing. Am I likely to need a brand new chain if I go down this route?
Can I put back in links that I broke off when it was a brand new chain?

Thanks for any suggestions and information you can share.

The first thing to look as is if you have a short cage or medium cage rear derailleur. If you have a short cage derailleur you are limited to either a 28 (on older ultegra 7800) or 30 (on newer 8000) for your lowest gear. But If you have a medium cage (gs) derailleur then you can go up to 34.

If you go with the front ring change then the Shimano recommenced thing is to swap both rings to a 50/34. There a tons of people out there who run 52/34 without issue though. You probably just wouldn’t have as crisp shifting up front.

For the rear, you would have to replace the whole cassette. I swap between an 11-28 and an 11-32 without having to shorten my chain. So it is possible but not always if your chain is on the shorter side of what works for 11-28. I just have to mess with my b tension screw to get it to shift well and that’s it.

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Do you know if you have Ultegra 8000 or 6800 rear derailleur? The S3 most likely came with the short cage derailleur. The 6800 has a 28t max cassette size and 30t for the 8000. My experience is that you can usually go another 2 teeth larger and it will work fine, but that is outside of shimano’s guidelines. Going 32t on a 6800 could be stretching it a bit but maybe others can confirm if will work.

You would need a new cassette as they come 11-28, 11-30, 11-32. In a Shimano cassette the first few cogs are singles but the larger ones are bonded together on an aluminum carriers. You will need a longer chain. I’ve put a link(s) back in using a Shimano pin a few times. Again Shimano says don’t do this but it can be done. I will also reuse quick links a few times. So basically I’ve done everything Shimano says not to do…

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I think I’m 6800.
How do you decide between changing your cassette or changing your front chain rings?

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Is there a rule of thumb about “how much you get” from just an extra 2 teeth on the rear (going from 11-28 to 11-30) or going down 2 teeth on the front chain rings (going from 52-36 to 50-34?

Would anyone have a guess based on the description of my cadence in my OP is 2 teeth enough or do I need more to get my cadence up (assuming the hills I ride are the same in general as the ride I described)?

If I’m honest I think you could swap both to a compact 50/34 chainset and a 11-32 cassette. If you can use your current rear derailleur, the cassette swap is probably the cheapest option, but the chainset will help you more, because it lowers your gears across the cassette.

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30T isn’t supported by Shimano on previous generation groupsets, but it will probably work. Shimano are pretty conservative with these things. I’m running an 11-30T cassette with DA 9000.

I was running 52/34 for a while and the shifting was only ever okay, I recently bit the bullet and got the matching 50T ring just for the improved shifting.

In your position I’d get an 11-30 cassette and a 34 small chainring. If the front shifting isn’t good enough you can get the 50T big ring later. You can check what your cadence will be with different gearing here.

(Just thinking further, there’s a decent chance the 11-32 will work with your current rear mech too, I’m running 11-34 on my cross bike with a 5800 mech, which is miles out of spec, and it works. It’s dependent on your frame to an extent though, so there is some risk).

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I had a similar decision to make recently. I had the same cassette and chain rings as you, I live in Switzerland, and had a ride with some steep climbs coming up. I spoke with a local bike shop and also made my own calculations.

In the end I went with an 11-34 cassette on the back and left the front chain rings as they were. The reasons were:

  • Limited availability of chain rings (I have some FSA ones with a 5-hole asymmetric bolt pattern)
  • based on what my lbs said, supported by my calculations, I would get a bigger percentage change in ratio from changing the cassette versus changing the chain rings:
    Going from a 36-28 combination to a 34-28 combination changes the gear ratio by around 5-6%, but going from 36-28 to 36-34 changes it by around 17-18%. So I imagine your cadence for a given speed should increase by that sort of percentage.

If you went for changing at front and back, you get around 22% change versus the current configuration.

Last thing (if you’re still reading!): I was able to make my Dura Ace short cage rear derailleur work with the 34 tooth cassette by tightening the b-screw. I replaced the chain as I heard that’s good practice when you replace the cassette, so not sure if the previous chain would’ve fit.

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I recommend checking out the difference using an online calculator like the one below to see the effective speeds for gearing changes across a few cadences.

http://bikecalc-staging.herokuapp.com/speed_at_cadence

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You can calculate it yourself using ratios in a simple Excel spreadsheet, or use one of the online calculators. This is one of the better ones.

That’s pretty big gearing for mountains for most people (ie unless you are a strong rider). I live in Colorado and have 50-34 and 11-32.

At 34-32, my cadence is 20% higher than it would be at the same speed in 36-28. So 70 rpm in 36-28 would be mid 80s on 34-32.

If you have the $, and will be doing more climbing in the mountains, Probably worth changing your rings, cassette, derailleur and chain.

A cheaper option is to try an 11-32 (or 11-34 if you want to push it) cassette. You might be able to make this work with your existing derailleur and adding a wolftooth roadlink.

You’ll probably also need to lengthen your chain (by maybe 1 inches) to make this work.

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if you think of your gearing as a range from say 1-10 then changing your chainrings is kinda like shifting your usable range within that. So if a 52-36 gives you 4-8 then a 50-34 will give you a 3-7. Changing your cassette will widen that range from say 4-8 to 2-8. The cassette also determines the jumps between gears. So an 11-28 will have smaller jumps between gears than a 11-32.

So if you don’t want to have a slower ‘fast’ gear but you want an easier ‘slow’ gear and you don’t mind the slightly larger jumps between gears then you will want to swap your cassette.

If you don’t want larger jumps between and are okay with a slightly slower top speed then you can change your chainrings.

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It’s all just math and the increases or decreases are linear with gearing. So going up in the back and down in the front will be easier. From a 28 to a 30 is a 2 tooth jump and will be about a 2/28 or 7.1% difference. So if you are going up a hill at 70 rpm with a 28 then to go the same speed with a 30 you will be pedaling at about 70*1.071=75rpm. (I’m rounding these numbers)

If your’re good with mental math then you can just get a rough idea in your head but the gearing calculators that others linked make comparisons a bit easier.

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I did all of this decision-ing last spring and found this calculator to be the most helpful. You can input multiple cassette/chainring scenarios and visually compare them on the same screen. Part of your decision may be the cost of the parts, a lot of times you can find new take-offs of chainrings and cassettes pretty handily on eBay and facebook groups. In my case I was spinning out on downhills and my zone 2 had me cross chaining frequently during windy seasons. Changing from 50/34 to 52/36 helped both problems and rings were cheaper than a cassette with generally similar results.

Hey folks,

I’m running ultegra di2 52 36 chainset and 11 28 cassette on my TT bike. Fairly regularly finding myself spinning out as my fitness improves and wonder if changing the front chainrings is the best way to gain a bit more speed?

I could accept a slightly higher, lowest gear if that’s the compromise.

Thanks for any input

Can you define “spinning out”…what is you cadence / speed?

The only time I have ever spun out my 52x11 is on downhills going 35+mph…at that point, you are better off tucking and saving your legs.

Even on the flats with a strong tailwind, I have never needed more gear than that…

I run a 53 on the front with an 11 - 28 on the rear and I rarely spin out even with a tail wind in TT but then I am a smaller rider at 60/61 kg and I race at a cadence of 95 - 100 rpm anyway. You can have a bigger front chainring - in the UK a lot of TT riders use a single big front - often from 54 - 58 teeth and take out the front derailleur …it is supposed to save a few watts aero wise and with chain angles…that said I think they come with longer teeth and you may need to adjust your chain as otherwise the chain can jump off as there is no chain catcher…some of them are non circular as well for more marginal gains…Aerocoach sell these so it’s worth a look if you are going that direction with your set up…It does need setting up properly though - a club mate of mine who puts out more power than me uses a single and has dropped his chain in a few races this year so you do need to get it set up carefully.

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I know a guy that runs a 56-34 chainring set up with an 11-42 cassette so that he doesn’t have to stop pedaling on descents during his long endurance rides. So yeah it’s definitely possible. The front shifting is probably crappy though.