maartendc

Hello all,

I'm in the market for a new crankset, and was doubting between a 52.36t mid-compact or 50.34t compact chainset.

I currently run a 53.39t with a 12-26 cassette in the back. I live in a very hilly area, so this is not ideal. On some steep climbs, even the smallest gear (39-26) will not get me enough cadence to go up the hill.

The area where I ride is full of tiny hills and "bumps" that have me shifting back and forth a lot (switching between the biggest and smallest gears every 15 seconds or so. I hate having to go to the big ring in the front. So I am worried that getting a 50.34 Compact chainset will make my gearing too small. (I would hate having to shift front gears every 10-15 seconds)

Would switching to a 52.36t make a big enough difference to get me up steep climbs? Or should I switch to a 50.34 true compact? I've never ridden either, so any advice would be much appreciated!

Thanks!

10 Wheels

50/34 will work for you. I rode up a 22% hill with a 12/32 cassette.

f4rrest

Your area sounds a lot like mine, and I had the same gears as you but switched to 50 34 recently to help my knee recover.

The only gear combo that ever made me smile on the rolling terrain was the 42 tooth middle ring with the 12-26 in back, but that was on a triple.

All other modern chainring combos require a front shift. Especially the super annoying compact cranks I have now. But DI2 solves this.

Point is, get either compact and know you'll be shifting the front a lot, so be sure have a solid front derailleur setup.

topflightpro

Go 50/34. If you find you are spinning out all the time, then you can buy 52/36 rings to put on your crankset.

rockrabbit

I've honestly never seen the point of a Mid Compact.

A standard 53/39 vs a compact 50/34 makes sense

A Mid 52/36 vs a compact 50/34 does not

Here is why, if you compare the inner ring of 39 with 36, you are talking a gear difference of 1

Meaning if we both had the same crank arm length and same cadence and same cassette of lets just say 10 speed 12-23; if I was in 39x23 going up and you are in a 36x23, from a gear inch perspective you are technically in a 24!

Use a standard crank for the non-mountain stages and use a compact for the mountain stages!

Just my 2 cents!

RShantz

Can you explain this further? I'm confused. Also, what does crank arm length have to do with it - I think I'm missing something.

rockrabbit

Crank arm length is actually meaningless here, I apologise for the confusion. I just run 175mm crank arms and most everybody else i know run 172.5mm or 170mm.

So ignore that part and just focus on gear inches

BikeCalc.com - Bicycle Gear Inches Chart

maartendc

True, but chainrings (especially the big ones) aren't exactly cheap, so I rather get it right the first time. The small ones can be had pretty cheap though, so I could get both a 34 and 36.

Interesting. So you are saying, there is not a lot of difference between a 39 and 36? This answers my question I guess, since I want there to be ENOUGH of a difference to make the switch make sense.

If 39 to 36 means a difference of 1 tooth in the rear, does 39 to 34 mean 2 teeth?

So essentially by going from 39 to 34 in the front, I am "changing the feel" of my cassette from 12-26 to 14-28?

rockrabbit

BikeCalc.com - Bicycle Gear Ratio Chart

Its closer to a change of 3

so a 12-26 would become a 15-29

Conversely, the 53 to 50 change is only 1, i.e 12-26 would feel like 13-27

I cannot stress this enough, Mid Compacts make no sense!

GuitarBob

Hilly? Another vote for 50/34.

Banzai

52-36 makes sense on 10 speed.

With a 50-34 I need an 11-25 cassette for my preferred gearing range. Those 11-x cassettes nearly always have an ugly 15-17 jump in the middle.

With a 52-36 I run a 12-27, which smooths out the transitions, and keeps the range where I like.

For those of you only doing math at the extreme ends, you're missing the finer details in between.

Inpd

What RD do you have? If its a medium or long cage then a quicker and cheap fix could be to go with a 11-32 cassette.

I have a 53/39, 5800 STIs and the 5800 long cage RD. Given the 5800 has 11 speeds the gear jumps aren't too bad for a 11-32 cassette.

I live in a flat area but I find for short steep hills going into 39/32 combo is fine. I wouldn't want to climb a steep mountain though in that combo.

Good luck!

velociraptor

I live in a fairly hilly area (ATL metro) and I run 52/36 11-28 on all my bikes.

Haven't met a wall I couldn't spin up yet and it allows me to take rolling hills by only shifting the FD.

But if you're super-concerned about long climbs (like mountains), then I would gear 50/34 12-32 long cage or thereabouts.

RShantz

I'll be the one who actually thinks a 52-36 has it's place. Where I live a typical ride has 50'/mile average of climbing and we routinely visit the mountains where we'll average 100-120'/mile.


The majority of the faster local guys (that don't have specific climbing bikes) run a 52-36 with a 11-32 cassette. This allows one to stay in the big ring all the time on our 50'/mile rides, gives us good ratios for climbing and gives a little more top speed on descents. Not to mention I personally like spinning a low cadence while drafting in a group and the 50'/mile rides have a good bit of areas with gradual declines where the pace can really pick up. I know we give up close gear ratios, but to me it's the best option if only using one bike and not wanting to change gearing every week or two.


My point is that I don't see how mid compacts can be said to make no sense. Around here the make a lot of sense to some pretty quick guys -not talking about myself. When they really pick it up, I'm hanging on for dear life.

cyclezen

Only you're gonna know what works for you...
so you say a 39/26 is not small enough (from your cassette 12-26 ?) which is 42 inches.
pick the gear you think will work to do the climbing - say a 34 inch gear, and put it into a gear calculator - along with all the other gears...
here's a visual calculator I like:
Mike Sherman's Bicycle Gear Calculator
& one which allows you to easily drag the gears around to get different combos:
HTML5 Gear Calculator

look at the ranges around which you'll have to double shift and see of this is OK - having to double shift in gear zones which you use constantly is a GIANT PITA.

For me a 50/34 ring means I only am ever in the small ring when I have some real climbing, It means staying only in the big ring (50) for many rides. Biggest issue is having a hole between 82 and 73. I really like to have at least a 78, which gets used a lot when I'm ridin 19-21 mph...

so put in the cassette range you want to use and then play with the chainring combos. You'll have to understand either gear development or gear inches as relates to your riding.

EDIT: Easier and a great way to quickly adapt a drivetrain to different ride plans - have multiple (2 or more) cassettes - I like having a 12-25 as my daily ride, and iffn I'm gonna do some serious uphill (and not wanting to ride the bike with the triple) I'll put on a 12-28 cassette. And for those times when it' rolling and/or fast 12-23 (single step 12 to 19 -like the good old days...) Personally I like 52/36 for a good spread, over 50/34.

gsa103

If your hills are less than <6% grades go with the 52/36, the larger small gear will let you stay on the small ring for shallow grades.

If you ever ride on 8-10% stuff then the 50/34 will get you lower gearing and you can just cross-chain for hills.

Bike Gremlin

36 and 34 are both too slow for flats.

52 is too big for flats, even 50 is too much for headwind. You ride quite cross chained.

So without a 39 (or a 42 ) chainring, I'd rather go for 50-34. That way a big ring is not too too big and the small one is more useful for climbs.

Though a 46-30 compact would be perfect IMO.

redlude97

the difference in rpms for a equivalent cog in the rear is 5-10rpm between 39 and 36. That make a big difference even if the equivalent GI is only equal to 1 cog.

redlude97

you average more than 25mph on the flats?

PepeM

Don't we all?

maartendc

Thanks~! Sadly the Rear derailleur is short cage, so going with a big cassette like that isnt really an option right now. Maybe I can get a 11-28 though.

I live in Atlanta as well Well, some hills around here that I do on a regular basis are too much for me on 39-26. But my cassette is 12-26 not 11-28.

Thanks for the tip.
I just measured some of the hills I do, and the steepest goes up to 11.5%, and is about a 1/3 mile long. Some of them are 8%. Most of them are probably less, but its on the toughest ones that I really struggle.

Thats interesting. I guess I could start riding in the big 50t chainring most of the time, and only use the small 34t one for hard climbs.

maartendc

Those are very helpful calculators, thanks! It makes me understand better the differences between all the combos.

I think I might end up going with a 50.34 in the front, but also switching out to a 11-28 in the rear. Seems like this would give me a better spread of gears while staying on the small ring in the front.

It seems like the 34-28 would give me plenty of climbing capacity, while the 34-11 would still allow me to go pretty fast without shifting in the front (as opposed to 34-12).

k_kibbler

I agree that only considering the 34-28 and 50-11 is missing the finer details. Having suitable gearing should mean that you're rarely at the extremes for the majority of your riding, and having enough granularity in between to handle different conditions.

When I was on a 52/36 I found that I spent most of my time in 52/16 or 17. Down shifting from 17>16 or 16>15 was a nice small 1t difference but upshifting was 17>19. Changing to a 50/34 means I'm now mostly riding in 50/15 or 16, the chain is slightly more centered, and 1 gear in either direction was down to an agreeable 1t difference, with smaller overall GI between each gear. And I'm still exceedingly rarely in 50/11 or 34/28.

Dean V

50/34.

Silvercivic27

50/34