Realistic chainring/cassette combination

[jarlrmai]

When I first got my road bike I knew very little about riding, I didn't even know what came with it. I rode the big ring a lot and didn't really do any hills as my 100 miles a week commute was pretty much my only riding.

When the rear cassette wore I took the bike in to the LBS and got a new cassette and chain and had a discussion with the shop owner (an ex pro) about cadences and the like. Since then I only ever ride the small ring on the flat infact I don't remember the last time I used the big ring even down hill at 30-40. He put on a cassette I think it was a 12 - 28 Deore and off I went. Next cassette I got given a new 11 - 25 105 cassette for free by a mate so when the old one went I got this one put on and it's generally okay but I notice that I don't have the range for a decent cadence on steeper hills.

Now I need new front chainrings and I want to get the gearing right.

So my question is given, i'm light and skinny and like to spin (now) and there are a few hills around here and I average about 17-18 on my own, what chainrings/cassette should I go for? I'm thinking a compact set with an 11-28.

 

[JasonHolder]

Compact is nice to have. I'd probably just put a 28 on the back again if it worked just fine

 

[HLaB]

What chain rings have you got at the moment and how do you feel about them? FWIW I'm running a 38/52 compact with an 11-28 on the back. I've can spin up everything round here (which isn't hard) and just last week up Winnats, etc and its perfect for me, for that terrain but if I was going to the Alps I'd want to fit a smaller inside ring, but that transition would be too much of a jump round here.

 

[jarlrmai]

its a 53-39

 

[HLaB]

its a 53-39

Do you feel you turn it well or is it a strain, do you feel at the limit close to the limit on your existing hills?
If you want to go for a compact you'll need to change your entire crank not just the rings.

 

[boydj]

I think you might find the standard 34/50 compact a bit uncomfortable. The 34 is too low and the 50 too high for a high cadence, since you'll rarely be running in the middle of the cassette. 38/52 compact or a standard 39/53 would probably suit better.

 

[jarlrmai]

Yeah I feel close at the limit to be honest even on the 28 I could have done with a bigger cog on steepest hills, I literally stay in the middle and up of the cassette on the little ring all the time and my cadence goes badly low on steep ramps so what's the point in the big ring at all? I'm not even using more than half the gears on my bike, is this common? Is it just the way bike gearing works or are standard chainsets and cassettes designed for pros and good club riders? Or maybe I don't do enough fast descending.

I realise I need to change the crank which is why I'm thinking about it rather than trying it out.

 

[jarlrmai]

Yeah 38-52 sounds like a good compromise to me.

 

[Rob3rt]

What sort of speed do you cruise at on the flat?

 

[jarlrmai]

Strava gives me 0% for 2 miles or so at 18-19, lot less if I get lost and have to ask for directions.

 

[User16625]

Do you feel you turn it well or is it a strain, do you feel at the limit close to the limit on your existing hills?
If you want to go for a compact you'll need to change your entire crank not just the rings.

Why do the cranks need changing? Cant you just fit smaller rings on the original cranks?

 

[jarlrmai]

Nope the holes don't match up.

 

[AndyPeace]

Why do the cranks need changing? Cant you just fit smaller rings on the original cranks?

BCD (Bolt Circle Diameter). Traditionally full chainsets (i.e. 52+ outer ring) have the bolts positioned further out. chainrings will be sold stating which BCD it fits.

@jarlrmai

what cadence are you aiming for? Descending at 30-40mph? on your 39x11 the you'll get 30+ pedaling at a cadence of 120+rpm but thats a fair sprint.
That said your 53 is big! I am running a compact 50/34 X 11-28. I'm only in my second year of cycling and I find a 50 great on the flat, as long as my pace dosen't fall below 16/17mph I find I'm on the better part of the block, averaging around 90rpm.

 

[AndyPeace]

Just an after thought but have you had a play with Sheldon's Gear Calculator ? It's pretty useful if your contemplating a new setup. You can get a better picture of the range of speeds a chainring/cassette offers.

 

[HLaB]

OT, I believe the new 105 four bolt clamp takes compact and traditional double rings (4 bolt of course )