IMKY13 finish!!
Okay….doing a little research/learning here and I’ve come across something I don’t quite understand (being the newbie that I am). Could someone please explain (in plain English) the difference/benefits of a 50/34 chainring vs. a 53/39 chainring. Thanks!!
Fitness/weight goals for 2014
1) STAY INJURY FREE!!!
2) Get to 189 lbs by the end of July 2014...and stay there (as of 4-25-14 was at 203 lbs)
3) Complete Ironman Chattanooga in under 14 hours
4) Break 4 hours in a stand alone marathon (Goal race=Rocket City 12/13/14)
5) 4,500 total overall miles for the year:
Swim: 100 miles
Bike: 3,000 miles
Run: 1,400 miles
Gear Ratio basics...
front gear / back gear times = gear ratio.
Gear Ratio indicates the number of rear tire rotations per 1 stroke of the pedal.
Therefore, a 48 front gear, and a 16 rear gear means that the rear tire will revolve 3 times for every pedal stroke (48/16=3.0). The more tire revolutions per pedal revolution indicates speed (provided that cadence is constant).
With a 2.080 meter rear tire circumference, and a gear ratio of 3.0 (48/16), the rear tire travels 6.240 meters for every pedal revolution.
Now, specifically relating to the 50 vs 53....
For a 50 gear, the rear gear may go as low as 12, so the maximum ratio is 4.166 (as I have on my Cannondale Synapse).
With the same rear gear, but changing the front gear to a 53, the maximum ratio increases to 4.416 (as I have on my Cannondale Slice).
That's the basics.
For the higher front gear, the separation between gear changes in the rear is more drastic (see below). Basically, (as I understand it) the more you need to change gears due to hills, the better the compact (50 front) would be so that the change is less radical and the cadence is more fluid. The more flats you ride (or the more power you have), the more top speed you can maintain because of the higher ratio.
50/12: 4.16
50/13: 3.85 (= 0.31 difference)
53/12: 4.416
53/13: 4.076 (= 0.34 difference)
53/14: 3.786
Life Goals:
#1: Do what I can do
#2: Enjoy life
Pablo
The 50/34 is refferred to as a compact crank. I haven't replyed to your "Another New Bike" thread but that bike has an FSA Compact crank.
What you are doing is decreasing the size of your drive sprocket. It's like the same thing as moving to a larger sproket on the rear cassette. Essentially what you are doing is giving your bike a lower gear without going to a triple front sprocket. This save weight on the bike. The trade off is you also give up top end speed since you have lowered your overall ratio. Since most of us amatuers rarely use the 53 - 11 or 53 to 12 combos unless were rocketing downhill this makes good sense. Where I live I find myself looking for another easier gear mor often than I'm looking for another harder gear.
Standard Crank (53 tooth) to 23 tooth rear = 2.3 = EASY
Standard Crank (53 tooth) to 12 tooth rear = 4.42 = HARD
Compact Crank (50 tooth) to 23 tooth rear = 2.17 EASIER than the EASY above
Compact Crank (50 tooth ) to 12 tooth rear = 4.17 Easier than the hard above.
The bigger the ratio the harder the bike pushes but further it travels for one revolution of the crank.
Over the winter I built up a Litespeed. I outfitted this bike with a compact crank and a 11 - 25 rear cassette. I load this bike down for RAGBRAI, I hate triple cranks so this way I get another lower gear and I really don't care about top end speed.
I see more and more TRI bikes going to the triple crank. I suspect to reduce overall weight since the big ring is smaller.
For a beginning cyclist I would recommend the compact crank. I would avoid a triple crank at all cost unless you plan or riding the Rockies.
Very good question and very important to understand.
I see KerCando snuck in while I was multi tasking.
He did point out another benefit that I didn't consider when it comes to TRI bikes and Time Trial bikes using the compact cranks and that is the smaller jumps between rear sprockets. This helps maintain a more consit cadence.
I don't live in an area that allows a consistant cadence so I wouldn't know what it's like to pedal down the road an maintain the same speed and rpm for 30 mins. I CAN do this on my trainer but that's pretty boring.
Either way...I like that the compact crank is gaining popularity.
Your next question will probably be crank length...don't worry about it ! It really doesn't matter that much although some will argue differently. We're only talking about 5mm's...the impact isn't noticable. Go with the 172's if you have an option. That way your right in between the two ends.
(I created, and provided the full gear options for the standard 50-34 and 53-39 in descending gear ratio order... See below).
The other benefit of a compact relates to the ability to stay within the tall front ring without needing to shift between the gears up front.
With the 50, you can operate in a normal range (2.9 to 3.8???) without needing to go to the lower front gear. Some bikers stay within the 50 the entire ride and manage well (hill or flats).
With either option, there are duality gears (ie 53/19=39/14, 50/19=34/13) that end out being a useless option. However, the compact has 1 useless option, while a 53 has 3 useless options (2.79, 2.30, and 2.05). Therefore, of the 18 true gear options (9*2), the 53 really has 15, while the 50 really has 17.
(I seldom find myself struggling with the 1.50 gear ratio while doing hills... but, as SloHand alluded to in a previous post, if you live in the mountains, then a low gear ratio will be a beloved gear on a portion of your ride).
I have 2 bikes, and 1 of each described. I like both, and find both to be comfortable to ride while enabling a great workout. If you plan to race triathlons, and you live in flat terrain areas with flat race courses (ie. Florida), and you consider yourself to have strong legs, I'd consider the 53. For me, the 4.17 ratio could be higher, and although I ride in the 4.08 frequently on my triathlon bike, I know that I have the 4.42 gear to go to when I have wind at my back on a flat course.
Thanks,Brian
See below:
50-34 53-39F R ratio F R ratio
50 12 4.17 53 12 4.4250 13 3.85 53 13 4.0850 14 3.57 53 14 3.7950 15 3.33 53 15 3.5350 17 2.94 39 12 3.2534 12 2.83 53 17 3.1250 19 2.63 39 13 3.0034 13 2.62 53 19 2.7934 14 2.43 39 14 2.7950 21 2.38 39 15 2.6034 15 2.27 53 21 2.5250 23 2.17 53 23 2.3034 17 2.00 39 17 2.2950 26 1.92 39 19 2.0534 19 1.79 53 26 2.0434 21 1.62 39 21 1.8634 23 1.48 39 23 1.7034 26 1.31 39 26 1.50
Therefore, of the 18 true gear options (9*2), the 53 really has 15, while the 50 really has 17.
Someone has to much time on their hands today.
And a 9 speed cassette is old school. It's all about having 10 today !
If I were going to be the uber weight weenie I'd set my bike up with 170mm crank arms, a compact crank and a 9 speed 11 - 23 sprocket but I'd run 10 speed hollow pin chain.
But then you have my latest build. One is all you need. Karate Monkeye 29'r single speed. You won't see it racing any Tri's but you might find it at one these. Gravel Grinders Check out the video at the bottom...pretty cool.
As Queen so elequently put it...
"I want to ride my bicycle, I want to ride my bike. I want to ride my bicycle, I want to ride it how I like. You say black, I say white; you say bark, I say bite, ...."
Regardless, there are many ways to enjoy biking, and, yes, I'm been considered by many to be guilty of over analyzing.
Cheers,
Brian
Puttin' on the foil
You guys nailed it. With a standard set up, on a hilly course (like Wildflower, IM Wisconsin, IM St. George or IM Coeur d' Alene) one needs to rock like a 27-12 or a 25-12 rear cassette. With the compact crank, you can ride a 21-11 or a 23-11. The gaps between gears is significantly less with your 21-11 or your 23-11, meaning you can make minor adjustment, like causing your cadence to go from 95 to 90 with a down shift instead of going from 95 to 85 because there is a big gap (like you get with a 27-12).
Don't be obsessed with your desires Danny. The Zen philosopher Basha once wrote, 'A flute with no holes, is not a flute. A donut with no hole, is a Danish.'
Friends don't let friends ride triples.
A 172.5 is a pretty standard crank arm length for bikes that are sized from 52 to say 56.. I have a friend who is 6'3" and he rides a 175. I think he rides a 58 frame, which is about the size of a small horse. I have other friends, shorter people, like under 5'4" that ride 170. That would be on a frame of 48 or 50, or someone who rides a bike with 650 wheels.
There is some though that shorter is better because you spin more and there is an aerodynamic benefit to the short crank. I almost went shorter on my bike I got this spring, but now I am on it I'm glad I stayed with the 172.5.
I just looked at the B2 that I just bought and it has a 55/39 chainring. 55 WTF? I'm gonna need to swap that out. I think I'm going to find a 50/34 set.
Do I need to shorten the chain if I switch to a 50/34? If so, how much?
The pain that hurts the worse is the imagined pain. One of the most difficult arts of racing is learning to ignore the imagined pain and just live with the present pain (which is always bearable.) - Jeff
2014 Goals:
Stay healthy
Enjoy life
I just looked at the B2 that I just bought and it has a 55/39 chainring. 55 WTF? I'm gonna need to swap that out. I think I'm going to find a 50/34 set. Do I need to shorten the chain if I switch to a 50/34? If so, how much?
BT
I don't know that I'd worry about it. Whats your rear cassette set up? 9 or 10 ?
I've been riding and racing (on and off) bikes for over 25 years. This is the first year I've been on a compact crank set. But my racing bike is still a 55/39 set up. The compact crank is on the "social" ride bike.
The "hot" set up is always changing. Don't get caught up in chasing it.
Training is far less expensive and 100x more effective than equipment. Which I will prove to a fellow triathlete this weekend when he takes his Cannondale slice out for it's inagural ride. He didn't invite me on his little training ride because he doesn't want to hear me give him shit so I am planning on a little ambush.
I rode the B2 to work today and after reading your "slowtwitchers" comments on my new bike thread, I shifted into the big ring and was mainly up in the large gears on the cassette (10 sp). I found I had to work my ass off to stay there. Maybe I'll drop it down to a 53 instead of the 55 like my road bike.
The cassette on my road bike is a 10sp 11-23. I'm not sure on the tri-bike but I'll have to check it out.
Thanks for the GREAT responses!!
I am really learning alot, and your answers really proved helpful...even to a dummy like myself.
Wow this is another language to me, I need to learn this stuff