compact chainsets: better acceleration?

skippy-do-da-day

gonna buy a bike with one on, just wondering if it provides better acceleration. also, you guys know any downfalls or advantages for going compact? cheers! it will have a custom 25-11 cassette on it.

Nuggs

Que? Why would it have better acceleration?

skippy-do-da-day

a 39 tooth provides better acceleration than a 42 that i usually train on. just wondering if the same thing applies to a 34 tooth. i want better acceleration up hills, to pull away quicker as im usually a hill climber grinding one gear all the time, but now riding in a peleton i feel i need more acceleration to pull away.

John.T

If you are riding in the same gear ratio it should not make any difference. I do find that using the same ratio on the big ring seems to have more snap. Probably just phsycological though. If you are using the same cog on the 42 and the 39 then the 39 will accelerate quicker but you will not reach the same top speed on it. The same will apply to the 34.
You would get pretty well the same gear ratios with a 53/39 and a 12/27. The main advantage of a compact is you can run a 34/27 bottom gear which is close to that on a 'standard' road triple but without the complication of a triple.

thetrotter

skippy-do-da-day wrote:

you guys know any downfalls or advantages for going compact?

I have had compacts on three bikes but have just reduced it to two and will utlimately go down to one. The reason? Great for long hilly rides like most sportives where the 34X25 really comes into its own. Not so good for day to day commuting or generally flat rides because I spend most of my time on the big ring and on a couple of sprockets at the back. Result worn out big ring (first time I have ever managed that in decades of riding) and frequent changing of rear cassette. Ultimately down to personal preference.

John.T

thetrotter. I have gone the other way and now have 3 bikes on compacts. With 53/39 I was wearing the inner ring out and only used the big one for racing. I now use nearly all the cogs on both of the rings and everthing is lasting longer.

Kafka\'s Doll

thetrotter wrote:

skippy-do-da-day wrote:

you guys know any downfalls or advantages for going compact?

I have had compacts on three bikes but have just reduced it to two and will utlimately go down to one. The reason? Great for long hilly rides like most sportives where the 34X25 really comes into its own. Not so good for day to day commuting or generally flat rides because I spend most of my time on the big ring and on a couple of sprockets at the back. Result worn out big ring (first time I have ever managed that in decades of riding) and frequent changing of rear cassette. Ultimately down to personal preference.

Ah, I wondered about this. I got a new bike before Christmas, with a compact, and now do my 35 miles a day entirely on the big ring. This will cause problems then? How do I switch to something more appropriate?

thetrotter

John.T wrote:

thetrotter. I have gone the other way and now have 3 bikes on compacts. With 53/39 I was wearing the inner ring out and only used the big one for racing. I now use nearly all the cogs on both of the rings and everthing is lasting longer.

Rather reinforces my point about personal preference. Will depend on riding style and terrain. I wouldn't be without a compact for hilly sportives. I just wouldn't use one for general riding again.

John.T

That is why I made the point. From my home if I head East it will be big ring most of the day but if I go any other direction the 34 will see quite a bit of use. You need to look carefully at how and where you ride before commiting yourself to either set up as changing is rather costly. It is cheaper to convert a compact to a standard (or anything you want really) as you can get TA or Stronglight rings in most sizes to fit 110 BCD cranks. That should help Kafka\'s Dolls problem. Spa Cycles can supply, also St John St I think. A bit of Googling will find a supplier.

skippy-do-da-day

mainly racing on roads where the races are won in the hills. also going to alps and pyrinees to train and race in this simmer / winter coming. so i think i will go compact. if not i will just wack on the standard again. atleast from then i will have the option.

cheers for the help chaps!

juggler

Run a 50/34 on my 'nice bike' and a '53/42' on my commuter.

My thoughts - with a 10 speed cassette you can get a good range on either (although in my case the commuter is a 6 speed classic ;-) . Top gear on a compact is 50 - 12 rarely if ever feel the need for something heavier than that, someone on the forum can probably do the math on pushing that gear at 100+rpm, but if you ain't racing can;t see you need anything heavier. The compact gives you way lower gears, which is great on a hilly sportive at 150km and you have a 10%+ climb and you are cooked... down side i have found is that i always wimp out and opt for the lower gear on the climbs... 'what the hell got the 34 - 27, why not use it, i'm not in a hurry' - not always the best option... especially when i get dropped by the regular 53/39 boys ;-(

On the original acceleration question - no idea... can not see that there would be any difference. But as there is minimal difference at the high end (50-12 against 53-11 say) and big gains on the lower end think compacts are a good idea for the non-competitive rider... just have to be stronger than me on the climbs and resist the temptation to change down ;o)

John.T

The compact gives you way lower gears

Not really true. Way lower than your 42 will give but for the same cassette a compact will only give you one lower gear than a 53/39. 39/27 gives a 38" gear which is almost the same as the 34/24.

andrewgturnbull

skippy-do-da-day wrote:

mainly racing on roads where the races are won in the hills. also going to alps and pyrinees to train and race in this simmer / winter coming. so i think i will go compact. if not i will just wack on the standard again. atleast from then i will have the option.

cheers for the help chaps!

Hi there.

The races may well be won in the hills, but not by those on the 34 chainring...

Cheers, Andy

Mettan

I'm currently running a 50/34 compact (previously a 53/39) - prefer the 34 (with a mtb cassette) over the 39 for going uphill - however, I prefered the 39 on the flat as opposed to the 50 or the 34 - with my setup/level/&injury the 34's too minimal on the flat, whereas the 39 with a smallish sprocket gave me a nice resistance on the flat. You can obviously work around it with different ring/sprocket combo's, and it obviously varies from person to person. Main benefit, as said, is the 34 and a decent cassette for going uphill - bike suddenly has a nice cushy "luxury" feeling to it

aracer

andrewgturnbull wrote:

The races may well be won in the hills, but not by those on the 34 chainring...

Depends who's racing and how steep the hills are. For normal mortals on steep hills, it may well be the chap on the 34 who can keep his gear turning over fast enough to put the power in.

aracer

thetrotter wrote:

Not so good for day to day commuting or generally flat rides because I spend most of my time on the big ring and on a couple of sprockets at the back. Result worn out big ring (first time I have ever managed that in decades of riding) and frequent changing of rear cassette. Ultimately down to personal preference.

Not the fault of the compact I'd suggest - I spend most of my time in big ring, and have yet to wear one out on a road bike, compact or not. Meanwhile if you're only using a couple of the cogs with the compact, why do you expect to use more with a standard chainset? I reckon you actually need to look at your chain replacement regime if you're having to replace cassettes that frequently.

John.T

I ended up on the 34 during the Yorkie Roads Hilly 10 on Sunday. The legs went and I was not confident that I could hold it on 50/21. With only a 23 left I went for the 34/15 while I still had momentum. Sometimes it feels good climbing on the higher end of the block knowing you can go a lot lower. It does not help your time getting in this situation though. Must train more before the Circuit of the Dales. I will be using 50/34 and 12/23 for that.

DavidBelcher

Kafka\'s Doll wrote:

thetrotter wrote:

skippy-do-da-day wrote:

you guys know any downfalls or advantages for going compact?

I have had compacts on three bikes but have just reduced it to two and will utlimately go down to one. The reason? Great for long hilly rides like most sportives where the 34X25 really comes into its own. Not so good for day to day commuting or generally flat rides because I spend most of my time on the big ring and on a couple of sprockets at the back. Result worn out big ring (first time I have ever managed that in decades of riding) and frequent changing of rear cassette. Ultimately down to personal preference.

Ah, I wondered about this. I got a new bike before Christmas, with a compact, and now do my 35 miles a day entirely on the big ring. This will cause problems then? How do I switch to something more appropriate?

Not a problem - if you want to convert to a non-compact chainset like a 53/39, firms like TA or Stronglight do the appropriate rings to fit a compact (110 BCD, I think) spider. TA chainrings aren't cheap, but the finish and lifespan are very good indeed.

David

John.T

I believe I said that some time back David.

DavidBelcher

John.T wrote:

I believe I said that some time back David.

Oops - sorry John, must've missed that one (as Q would have put it, "Do try and keep up, 007")!

David

scak456

This summer, have set up bike as follows:

Compact with 50/34 for hills/sportives

Will swap 34 for a 38 for flat/tris/TTs

Cheers
SK

wheeler585

I race on a 34/50 with a 11-23 and its perfect for me,never get out of the big ring like!! But its the perfect contrast for both hilly and flat races. Who said compacts are for puffs!!! Im sure alot of people will be converting in the race scene,not unless they already have done!! I must admit that im forever in the big ring and dont find that it wears the teeth down as much as you say!

Its all in the legs baby!!!