what are compact cranks for? (Page 2)

I'm a regular steep hill rider and have a compact crank with a 12-27 - this combo has taken me everywhere I've needed to go  

I'm gonna back Joel up on this one..... looking at the top end first (kind of like working out gear rations for a racing car work out what you need at either end then fill in the middle as a start point....

My 50/11 - spins out (ie 100rpm when I would probably stop peddling) @ 35.3, your 53/12 @ 34.3mph

MY 34/23 - at 80rpm (slowest I would want to turn over in a race) = 9.2mph, your 39/25 @ 9.7mph

Now in a flat TT both of us would spend most of our day in the big ring, 11-21 (the useable part of an 11-23 when in the big ring covers me from 16.7 to 31.8mph assuming 90rpm

Your 53 with 12-23 goes from 16.1 to 30.9mph.

Now having a think about power usage and effecient pedalling etc.

My FTP is around 235W, in a 1/2 or longer I won't go over that and in an Olympic I will go up to 300W for climbs. So at 175lbs (race weight) that 300W equates to 9.7mph at only a 7% slope.... in longer events my 235W gets me up a 5% slope in my 34/23 at 80rpm.

In addition to all these #'s... a 50/34 is lighter... uses a shorter chain (lighter)... has a smaller contact are with the chain (so lower friction losses) vs a 53/39. Only if I could get my FTP over 300W would I think about going back to a 53/39... (3.75 W/kg - g'tee that's higher than 99% of people on this forum)

Yeah...that's basically what I was trying to say. I just didn't feel like typing all of that


Edited by TH3_FRB 2006-11-27 10:31 PM

The USA Cycling coaches manual summarizes a study that looked at different interventions that had been reported in peer reviewed literatur and the theoretical magnitude of impact on TT performance in novice/intermediate/expert riders.

They evaluted carbohydrate beverage ingestion, caffiene, lighter weight bike/components, aerodynamic positioning, aerodynamic frame, and finally, training.

From the USAC document (which is a summary):

"For the novice cyclist, the clear winner in providing the largest benefit is proper training in all scenarios except the uphill TT on a 6% grade (and just how often does someone compete in that event?). And that is just using the minimum estimated gain from training. If you look at the average impact, training more than doubles the benefits from every scenario except that 6% uphill TT scenario. As the cyclist progresses in fitness, other factors provide larger potential benefits although proper training still has a strong impact."

So, triple, double or compact, the biggest bang for your buck is to get out there and train.



Original article:
Jeukendrup, AE and Martin, J. Improving Cycling Performance: How Should We Spend Our Time and Resources. Sports Medicine, 31(7): 559-569, 2001.

Thank you ...... that was my point without having to type it all.

There are so many other variables not even mentioned ...... crank length and wheel/tire size being other influential aspects.

(And AusVirgin, I run an 11-21 or 11-23, haven't had a 12 on any of my bikes since about 1994 or so ...... which means my 53/11 has more top end than the compact!! ;-P )

In a tri (rather than a TT where you should roll over the line and off the bike), if you're spinning out the 53/11 regularly you should either workout whether those Joules of effort are better saved for a different point in the race (going uphill where increased Watts ->> greater relative speed increase) or step-up to join the elites ;-)

My training time is capped by outside features (work) those outside features give me the ability to choose what gear I have and play with alternatives. If other people are in the same boat then asking your LBS to swap out the 53/39 for a compact when you buy (probably free) or the $75 I just paid for an FSA Gossamer compact on eBay (BB incl) is money well spent.

If that money or time is stopping you getting out training or you could fit more time training rather than sitting in front of the TV (or BT!) then keep your money in your pocket and JFR!

STANDING?

Is that even a technique you should ever use on a Tri? Just kidding to some extent but standing on any climb, past stretching out for short periods of time, is going to toast your legs quickly for the run. The most effecient way to climb for a triathalon and save your legs is to sit and spin. It isn't a bike race after all.

A couple of posts mentioned gearing. The compact allows you to use a 11/23 or a 11/21 cassette and keep the gear jumps much smaller than a 12/25 or worse yet a 12/27.

A much better close ratio gear stack on a 11/23 and the same climbing ability and top speed as a 12/27. Hard to not like it.

Anyone running a 11/21 and a 53/39 and spinning out the 53/11 and climbing anything that remotely resembles a hill in 39/21 is far beyond most AG triathelets.

I have several bikes and lots of gearing options. I decided to go with a compact on my tri bike last summer at the end of a 10,000' century ride when I couldn't spin out my 53/11 going down hill a few miles from the end of the ride. If I couldn't spin out at the end of that century I sure wasn't going to want to, let alone force myself to, at the end of a IM bike before starting a marathon run.

Any Tris longer than a sprint is all about saving your legs for the run. Anything with hills on it for most of us is going to be all about saving your legs including Sprint length races.

I run a 54/42 on my TT bike which on occasion I'll use for a sprint Tri that is flat. But in our area there isn't a flat Tri past sprint length. So I ride a tri bike with a compact and a 11/23 rear cassette for most of them and normally finish in the top 10 or better in my AG. A decent OA placing for me is always anchored by a good bike ride. The bike is the easiest place to gain time OA in the race and the easiest place to trash yourself for the run and loose everything gained and more.

Easiest way to figure out what gearing is right for you is do a LT test on a TT course that most closely resembles what you race or will be racing on. If you can hold a 5 mile flat TT course at 90/100 rpm and 25+mph without blowing up your MHR then by all means run a 53/39 front set up. If you can't , you might be better served with a compact up front and be able to then use more of the 10 gears you have available on your bike. (haven't seen anyone here posting 25+mph race splits)

I race a dozen or so Tris a year. My gearing is specific for every race and dictated by the hardest climb or climbs on the course. For me spinning legs, are happy legs when it comes to the run If I hit a low of 65 cadence during a race I know I have done something terribly wrong in my planning or training.

No, but what?

"HR got over 156 I backed off"

so you blew past your LTHR

"needed to get back on the 39 to spin up"

you had to drop to the small chain ring on a 40' hill?

"Barely managed to average 20 going up"

39x14 @ 90rpm is 20mph. 90rpm spinning up?

"There's a ~40-foot hill about 3/4 of a mile in, that you cross again at 9.25 miles. Other than that, it's flat as a pancake"

Did you average 90 rpm or higher on your cadence? Hitting 90 rpm isn't needed for a TT but might be nice for a Tri.

And you didn't make a 25mph average let alone 25+.

FWIW as I mentioned before I wouldn't use a compact on that TT course either. 53/39 or 54/40 would have been fine for most on that course as a TT. Without knowing what your cadence average was and what gears you used it is hard to say what chain rings your numbers would indicate as optimum.

Here is the gear chart I use....

http://www.bicyclesource.com/bike/gear/gear-javascript.html

It is very helpful...I have decided a 50/34 11/23 is what I will do...I should get a little more top end and a little less bottom end than I have now....I will have to just work harder on my hills, I am ok with that....

If you had a serious problem with the hill work you could do a 12/25 but you top end would suffer a bit but still pretty good....

I have had compact cranks for a few years. I really like them but you have to have the right front and rear setup...I don't believe you can go out and just buy compact cranks and that is it and have it work out as a benifit....

Just my opinion...

Been doing this long enough that I don't feel the need to publish race results or training load in a public forum for bragging rights. Also been training long enough to make a 30 sec analysis from the limited info you posted.

"Yes, my cadence stays above 90, when racing it probably exceeds 100"
If it did average above 90rpm with a 53/15 you'd easily average 25+.
Your datas shows you riding the majority of time on the 16/21 side of a 11/21 and in the small ring on small hills @ 39/15 or more or you are spinning a lot less than 90rpm.

Joel pretty much covered it.
"Until my training gets me to the point where I can spin 95rpm up a hill (i ssuspect he means soethting over 40' when he says "hill" ) with a 53/23 and stay in Z3 I'll be running my compact."

Smart man and also kicked serious azz in Florida @ 02:16:28 | 56 miles | 24.62 mile/hr. All on a compact even with the Peleton. Congrads are appropriate.

I prefer to train and race smart. That was my point. Figuring out if a compact will help you is part of that. A 5 mile TT course on the kind of terrain you'll be racing on can easily do that for you.


Looks to me like the Bear could use a compact, a nap or just needs to ride lots...more.
Those first two years can be so full of new info

Wow, for once it's the Bear who's getting the smackdown from someone else. Nob, you are coming across pretty high and mighty on this topic. you just need to chill out and head on over to slow twitch of you want to continue your rants in this manner. Education on gear ratios & cadence is a welcome thing, but your criticisms of someone else's training & racing reports is really uncalled for in a public forum.

Sorry it came across that way. No personal criticism intended. Just my observations on the stats offered in the link.

AB, I see your signature line has two coaching certs on it. How about a coach's thoughts on the advantages or disadvatages of a compact crank? How would you suggest a beginner triathlete make an educated decision whether to use a compact or stick to a typical 53/39 ? In a coach's eyes how does a triathlete's needs for gearing differ, or does it, from the needs of a cyclist?

Your thirty-second analysis is worth both the time you spent on it and the price you charge. Just because I'm not pushing the top range of my gears I should go out and spend money on a compact? I'm not using most of the lower range as well, by your assessment, the lowest gear I used was a 39/14, leaving, what, five, six gears lower that I didn't use? Going compact would only add to the number of lower gears I wouldn't be using.

If I was training and racing on different courses I could see the benefit of a compact, but given limited financial resources and unlimited equipment needs and wants, buying a different set of unusable gears is not a priority.

Edited by the bear 2006-11-29 5:14 AM

I'll stick with my previous post that training is most important for a beginner anything. As far as buying a bike new, if it comes stock with a triple I'd stick with that. If it comes stock with a double and you live in CO or WV or anyplace with extremely steep grades I'd go with the compact. A triple will give you a better low end than the compact will. I'm sure you're not asking me in order to educate yourself on the matter, and I hope you're not trying to pick a fight! But that's really just my opinion as an athlete...none of the coaching certs I've done (USA Tri level 3, USA Cycling leve 1 & 2) so far have approached the topic of compact vs. regular vs. triple in the formal curriculum. As long as you know how and when to switch gears, you're golden. If you run out of range then you're probably not a beginner anymore.

Hills are my weakness. I run a triple with a 12/27. Blasphemy for most, I know.

Edited by AdventureBear 2006-11-29 2:36 PM