Compact v semi compact

Discuss light weight issues concerning road bikes & parts.
wilwil
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by wilwil

Seems like everyone is going semi compact (36-52) these days. What are the advantages over compact (34-50) other than the one higher gear that is achievable?

PinaF8
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by PinaF8

Depending on your strength and condition you may overspin with compact. I've tried compact then moved to mids, now on standards.
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raisinberry777
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by raisinberry777

wilwil wrote:Seems like everyone is going semi compact (36-52) these days. What are the advantages over compact (34-50) other than the one higher gear that is achievable?


There's really very little between the two. This link shows the extremely minimal difference:

http://www.gear-calculator.com/?GR=DERS ... 8&UF2=2135

fromtrektocolnago
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by fromtrektocolnago

Semi compact has virtually no difference in the big compared to standard. A bit easier in the small ring. You'd probably notice the benefit of the compact more on longer climbs. I'm on semi-compact having come down from a standard on my older road bike. I have a compact on my gravel bike and it feels like over-kill to me on anything but the most brutal of climbs.
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Marin
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by Marin

If you ride a high cadence and climb a lot you want a compact. All my high efforts are at a cadence of about 100, and I really dislike not having the option of riding a high cadence uphill, so I ride 34/46 with 11-28 or 11-32 in the rear.

IMO, no one should need a 53-11 or even a 50-11 unless they are trying to beat a downhill speed record.

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MJB
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by MJB

Occasionally I run out of gearing running 50/34 compacts, usually on a prolonged decent I can top out @ circa 115 rpm cadence on a 12t cog and just freewheel instead. This might happen 2 or 3 times in 5,000km /a year of riding for me. As a high cadence rider (I average around 97 to 100rpm on a ride) and being a pleasure rider it's not a biggie. So a semi-compact will buy you a tad more gearing but that is all. I'm happy to stick to compacts on all my bikes.

topflightpro
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by topflightpro

Semi-compact is a good compromise between a standard and a compact.

I like to race crits, and for that, I prefer a standard crankset. (I did run a 52 ring for a couple years.)

But when I go to the mountains, I'd really like something smaller than a 39. A 36 or 34 would be great. (As a workaround, I ended up going with a long cage RD and a 11-32 cassette. The 39-32 runs equal to a 34-27, still, it would be nice to have an even easier gear sometimes.)

One caveat though, the 52 on some mid-compacts can be a bit flexy. I think FSA really nailed it several years ago when it offered a two-bcd system, with 130 bcd for the big ring and a 110 for the little.

PinaF8
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by PinaF8

Marin wrote:If you ride a high cadence and climb a lot you want a compact. All my high efforts are at a cadence of about 100, and I really dislike not having the option of riding a high cadence uphill, so I ride 34/46 with 11-28 or 11-32 in the rear.

IMO, no one should need a 53-11 or even a 50-11 unless they are trying to beat a downhill speed record.


I use 53-11 when sprinting. For climbing yes that would be impossible to some but when sprinting it is useful.
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cmcdonnell
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by cmcdonnell

Marin wrote:If you ride a high cadence and climb a lot you want a compact. All my high efforts are at a cadence of about 100, and I really dislike not having the option of riding a high cadence uphill, so I ride 34/46 with 11-28 or 11-32 in the rear.

IMO, no one should need a 53-11 or even a 50-11 unless they are trying to beat a downhill speed record.


Needed an 11 last night when I was passed in a sprint at over 40 mph peddling at >110rpm but that was usual and there was a tail wind.

In all honesty there is no right answer. I always (almost) use a 12-25 cassette, have done in 8 speed, 10 speed and 11 speed. Chainset wise, for me a 52/36 is brilliant, found 50/34 a pita and never seemed to have the right gear, always used a 53/39 before that and when I went to the 50/34 had to swap in a 11-23 cassette so that defeated the purpose. I spend most time in the 52 and when I need the little ring the 36 is fine, just one click more than the 39 offering an additional lower ratio. Never really noticed any difference between the 53 and the 52 so the 52/36 has been a win win for me
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glepore
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by glepore

I'm on a full compact now. I miss my 52/34 that I ran previously, but with spiderings you don't have that choice.
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by Valbrona

[quote="cmcdonnell]In all honesty there is no right answer.[/quote]

Eureka!

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Calnago
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by Calnago

^ I was thinking exactly the same thing when I read that.

I have all manner of gearing at my disposal, but I will say the one combination of chainrings that I just do not like is the compact 34/50. It's not so much the gearing it provides as the jump. I would find myself shifting between big and small rings far too often, and even with a simultaneous shifting of 1, 2 or 3 cogs at the back I never really seemed to be landing in the "right gear". Versus with either the 36/52 or the "standard" 39/53 a quick change at the front with a simultaneous 2 cog shift at the rear and boom, I'm pretty much where I want to be. The physical distance the chain has to fall is also greatest on the 34/50 and creates a more awkward shift than either of the other two. With a 12/29 cassette at the rear, I can manage most anything with the 36/52 up front. I do prefer close ratios at the back over wide spacing so the 12/29 is good for areas with a lot of climbing but a smaller cassette is what I prefer on more flattish terrain. I think the only time I would choose a 34/50 is if I knew I was going to be in the 34 for a great majority of the day. I prefer the 39/53 for most things. The 36/52 is a nice compromise between the two.
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RyanH
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by RyanH

I have both. The one thing I like about the 50t chainring is that I can big ring most of my group rides with a 28 in the back without often needing to touch the biggest cog. I dislike riding on the flats on either a 36 or a 34 as they do not feel nearly as smooth as a 39t does. Now, since this is WW, full compact is the lightest.
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Lelandjt
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by Lelandjt

I'm used to a standard crankset so that colors my perceptions but a couple days ago I road a bike with a compact and I felt that the small ring was only usable on climbs. I'm used to using the small ring when I get into a town and will be stopping frequently and then only getting up to 18mph or so. On the compact I kept finding myself cross chained either using the big ring and the bigger cogs o get away from a stop or spinning like mad in small and smallish to go traffic speed between stops. Also, there's the fact that I found myself using the 11 and 12t cogs much more than usual. I'd expect the 36 and 52 to feel better in both these respects. Though I'll never trade in my standard for either of these I guess if a 39 is too hard for you on climbs a semi-compact could be a good compromise.

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pdlpsher1
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by pdlpsher1

RyanH wrote:I have both. The one thing I like about the 50t chainring is that I can big ring most of my group rides with a 28 in the back without often needing to touch the biggest cog. I dislike riding on the flats on either a 36 or a 34 as they do not feel nearly as smooth as a 39t does. Now, since this is WW, full compact is the lightest.


+1. With a 50 chainring and a wide-range cassette I end up shifting the front less. I can big-ring all the rollers and only shift to the 34 on extended climbs. This is helpful on fast group rides where the pace is high and you just don't want to have to shift the front if you know you only need the cross-chain gears for ten seconds or less. I'm running 50/34 and 11-28. I'd like a cog larger than 28 but I fear losing my 16 cog is too big of a compromise. I hope I can buy a 12-32 cassette just for the mountains but that also means I have to upgrade my RD.

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