Road Cycling - Interesting article on double v.s. triple

I don't know if this had been posted here before. A bit hard to read, but I think it contains good info.

......" How strong do you have to be to get away without a triple? Well, about the lowest possible gear with a double is something like 36/32, or 30 inches. That corresponds to a flat speed of at least 21.6 MPH. So, unless you're pretty strong, or like to suffer a lot, you really NEED a triple chainring. A typical double-chainring road bike, say with a 40/28 bottom gear, is really only suitable for someone whose flat speed is at least 23 MPH. Needless to say, there a lot of people with that kind of gearing who aren't anywhere near that strong. If the bottom gear isn't low enough, the only way to climb a long hill is at a painfully slow cadence. Or to walk.".....

http://danenet.wicip.org/bcp/gearing.html

I don't agree. With the right chainrings (48-34) and a wide range MTB cassette you can have a low gear of 34/32 which is plenty low enough for any reasonably strong cyclist.

I do wish my 10 speed (I don't know what gearings it is... its an older road bike) had a triple. The climbs here are short... but I always spend my time on the steep parts in the lowest gear, struggling to keep a worthwhile cadence. (there is one climb in particular... 5k long, and the first K is pretty damn steep. I wish I could measure the gradient somehow... (Any ideas?))

21.6mph?! No no no. Someone out there needs a reality check.

Typical rolling diameter of 700C road tire: ~2100mm or ~83 inches (I'm not bothering with lots of decimal places here)

Typical minimum RPM when climbing: let's say 75rpm

Low gear on a typical road bike: let's say a 39 x 25 as a reasonable one, that is a 1.56:1 ratio (wheel turns 1.56 times per crank revolution)

83 inches/wheelrev x 1.5 wheelrev/crankrev x 75 crankrev/minute = 9300 inches per minute

9300 inches per minute / (12 inches/foot) / (5280 feet/mile) x 60 minutes/hour = 8.8mph climb speed on a 39 x 25 at 75rpm with typical road tires.

Where are they getting 21.6mph? In a 39 x 25, the rider would be turning 180rpm+ cadence to hit 21.6mph.

Point well made Mechbgon, I thought there was something fishy about that 21.6 mph figure - if I have a cadance of about 90 with 52/17 at about 21mph and then threw the bike into bottom gear (39/26) my legs would most probably explode trying to keep up, let alone trying to spin a 36/32 combo!

Riding at the weekend, I had one short but steep climb which certainly reaches 10% gradient for 1/2 mile of its run - it is marked on the map. I managed this with 39/23, trying deliberately not to use the lowest gear of 39/26, "just because". Both my bikes have a double setup and these gears are plenty low enough for me. But that is the point - we each need a bike which satisfies our own requirement rather than be influenced by fashion or peer pressure.

Just my 2p as they say,

Cheers,

Ed

The lowest double I have seen is a 28/40 chainrings with 13-28 cassette.

Truth is.......the way most doubles roll off the showroom floor is overgeared for
a lot of cyclists if they live in a hilly area. As is the case elsewhere, people are buying the image; and not what they need.

Agreed.

I've just been using my tourer, with 48-38-28 front and 11-28 8 speed rear.

This gives me a 27 inch bottom gear (fine for me, if I can't manage that I'll walk :)), but the top gear is way too high for me.

Also, as I'm a newcomer to anything over 6 speed rear, I can really feel the deflection of the chain across the rear cassette. If I'm sympathetic to the chain it probably means using the outer 4 at rear with the 48 ring, the middle 4 rear with the 38 ring and inner 4 with the 28.

Means less usable gears. Not sure of the benefits of triples other than bigger spread, but no real increase in numbers of useable gears.

I think I'll swap to a 46 or 44 at the front, that'll still give me a 108 inch top (more than enough)

My Scot will remain as a 10 or 12 speed though.

Originally posted by MichaelW
The lowest double I have seen is a 28/40 chainrings with 13-28 cassette.

Do you have any idea who sells chain rings in these sizes? The reason I ask is I'm 99% sure I'm building my Lemond Nevada City back with a double chain ring and would like to have a combo like this if I decide to ride it instead of the K2 on the 3-Gap 1/2 century ride I'm going to do in September.

Thanks!

Zack

The 28/4o was built on a Stronglight-80 chainset with Stronglight rings. Its quite good quality stuff, and has a very small diameter BCD, so any ring from 28 to 52 will fit.
A 28/40 is really for little old ladies (like the rider). A good bet for non athletic average rider would be 36/48. You need a chainset with a 110BCD. You cant do this setup with a Shimano std 130 or Campy 135mm BCD.
Specialities-TA are the first port of call for this setup, if you have the $$
http://www.peterwhitecycles.com/zephyr.asp

Otherwise, check out the makes on production cyclo-cross bikes.

A speed of 21 mph!?!

My bike as chain rings with 53/39 teeth. I ride a 13-26 rear cassette. That means my low gear is 39/26 times 27 = 40.5 chain inches. 100 chain inches at 100 rpm is 30 mph. So at 100 rpm 40.5 chain inches is 12 mph. And if a hill is really steep, you can slow to about 60 rpm or 7 mph. With this gearing, one might not want to go up a really long steep climb but it works pretty well here in Central Florida where we do have some hills but they are all short.

In Shimano 105, the triple chain ring is 30 teeth. So with a 28 rear cog (the highest Shimano 105 allows), you have 29 chain inches or 9 mph at 100 rpm or 5 mph at 60 rpm. If you really like to spin, you might even want to have a lower gear.

there's just WAAAAY too much math on this thread! ;)

i don't much get into the math side of it. i've got a triple now that i hate. i never use the granny, partly out of pride, partly because i've never needed it (i ride in the n.c. mountains, so we've got some hills here). my new bike (which is still a pipe dream) will have a 53/39 and probably a 12-25 in the back. if i find a hill i can't get up, i'll go down, train harder, and come back later in the season.

Brent_dube,

Bike Nashbar has chainrings on clearance for $15. You probably need the 110 mm bolt circle. If you swap out the 52-42 chainrings for something smaller (like 46-34) you will have a much easier time on those hills.

The whole "triple-crank" thing isn't really anything about fitness or cadence or any of the gear inch "jazz".

Fat people and cyclists with heavy touring loads need triples to be comfortable. Everybody else can "gut it out" if they want..

I'm not saying there aren't plenty of hills that need something lower than a 39x27, it's just that they are not that common.....and if they are, then ride someplace else....

Originally posted by mechBgon
21.6mph?! No no no. Someone out there needs a reality check.


Originally posted by Ed Holland
Point well made Mechbgon, I thought there was something fishy about that 21.6 mph figure - if I have a cadance of about 90 with 52/17 at about 21mph and then threw the bike into bottom gear (39/26) my legs would most probably explode trying to keep up, let alone trying to spin a 36/32 combo!

According to the article, the 21.6 was the speed a person could sustain for 15 minutes on a flat course. It is not a speed obtained in the low gear. I think the author is just trying to arrive at a reasonable gearing for the amount of effort someone is willing to exert over a 15 minute period.

Where I ride, there is no avoiding the hills. They are not high, but with 15% grades and steeper in places, you need a triple to avoid busting a gut. There are times I like to ride up a hill at something less than max effort. There is one hill where I bust a gut with my 27" low gear.

Originally posted by Richard Cranium
The whole "triple-crank" thing isn't really anything about fitness or cadence or any of the gear inch "jazz".

Fat people and cyclists with heavy touring loads need triples to be comfortable. Everybody else can "gut it out" if they want..

I'm not saying there aren't plenty of hills that need something lower than a 39x27, it's just that they are not that common.....and if they are, then ride someplace else....

From a FAT person to apparently a thin one...I hope you never have to eat your words!!

Originally posted by Richard Cranium
I'm not saying there aren't plenty of hills that need something lower than a 39x27, it's just that they are not that common.....and if they are, then ride someplace else....
I guess it kinda depends on where you live, doesn't it? Around here (SF Bay/ Peninsula/Silicon Valley) most of the flat places are all built up and no fun to ride. If you want to get a nice ride you have to climb hills. Most of the climbs are 3.5 to 6 miles long and are 6% or steeper. Lots of these climbs have significant sections (a mile or more) at 10% gradients or greater. I've timed myself on these climbs with and without the triple and my times are about the same, and my 50+ year-old knees feel a lot better. Yes, I could do these rides (and have) with a double but I get a lot more enjoyment out of the ride with the triple since I have the option of shifting between seated climbing and standing. I could put on a wider range cassette but then I would have difficulty trying to maintain a good cadence in a paceline where the speed would range between 20-26 mph.

Besides, bike riding is supposed to be fun and busting your gut up a 12% grade after you've already put in 75 miles ain't my idea of fun. Oh yeah, and I don't want to have to avoid some routes because they're too steep. I want to do them all!

SteveE

Richard Cranium! I object to your post!! Your response is so limited in scope and understanding of the realities of the abilities and physical limitations of many of our members. Grow up and then post again!
Hockey

Originally posted by Richard Cranium

I'm not saying there aren't plenty of hills that need something lower than a 39x27, it's just that they are not that common.....and if they are, then ride someplace else....

Been to my part of Scotland recently have you? :D

Believe me, in the UK we need a good spread of gears.

I agree with Cycletourist I disagree too. I run double chain rings and have done so for 35 years and can't see a reason for triple. Sure I climb some long steep mountain roads where I'm cranking in first going about 7-8mph and only turning about 35rpm-so what? I've done this for years.

I run a 42/ 54 in front and 28/12 in rear-someone else do the math for me, I'm not good that.

Errm, slice of humble pie for me please..... I just went back and actually read the article, as I ought to have done in the first place before posting. It seems actually to be very well written and gives guidelines for a wide range of cycling abilities. Certainly no mention of riding at 20+mph in the lowest gear.

Sorry folks,

Cheers,

Ed

funny how everyone with a double seems to know more than the article author......

I think the gear ratio recommendations are on the money, but I have to agree that doubles shift better. Maybe the answer is doubles with smaller chainrings inner and outer. maybe a 44/32 with a rear 12/34?

seems like folks are getting a bit tense here. i really don't think anyone's trying to say anyone who uses a triple is a bad person. it's really more what you're after. Me, i want to use a double (even though i've got a triple) because, darn it, Lance uses a double and of course I want to be like Lance. Does it mean I might wind up pushing a gear that's too big sometimes? probably. that being said, it's still an awful lot of fun to crush someone in a sprint with my triple when he's got a double...

triple cranksets would not be needed if doubles came with better gearing.

Originally posted by pgreene
seems like folks are getting a bit tense here. i really don't think anyone's trying to say anyone who uses a triple is a bad person. it's really more what you're after. Me, i want to use a double (even though i've got a triple) because, darn it, Lance uses a double and of course I want to be like Lance. Does it mean I might wind up pushing a gear that's too big sometimes? probably. that being said, it's still an awful lot of fun to crush someone in a sprint with my triple when he's got a double... I don't mind what anyone rides :) It's your bike, your knees, your heart and your money. The premise as originally stated seemed to not make sense from a mathematics standpoint, is all.

I like the tighter sprocket ratios I get with the triple. Haven't yet resorted to the largest 2 (21 & 23) so the smallest I've used is 42" (same as 39/25) even on 16% grade. I can climb in much larger gears out of the saddle. Fact is, I get a nice corn-cob to boot and smooth shift intervals. For me triple has nothing to do with small ratios.

Doubles do not shift better than a properly tuned tripple, the shifting precision is the same, most bike shops don't tune them properly and most riders don't shift them properly. The wieght of a quality tripple crankset verses a double is not noticable to the average rider. The benefit of having the small ring is well worth it at the hilly end of a 125 plus mile day. The benefit of having the big 52 or 53 tooth ring lets you ride with the club and keep up. If you want to ride a double, ride one, if you want a tripple, well then, ride one of those, but do it because that's what you want to do, not what others perfer. The only persons day that will be ruined by the wrong gearing on the bike for your fitness level, is yours. If you want, you can have it all, A D.A. tripple XTR rear 30, 39, 53 up front andd 12 - 34 rear, properly tuned and go for it, all of it

I have been riding a double chainring 53/42 with a 13-21 casette here in Washington, DC for 3 years now. It gets a little hilly but nothing bad. If I had to bike long, steep hills I would consider going to a smaller chainring for the double. It just seems to me that the 3rd chainring would get so little use. But then again, if I rode a ton of hills I might think differently.

Originally posted by pgreene
seems like folks are getting a bit tense here. i really don't think anyone's trying to say anyone who uses a triple is a bad person. it's really more what you're after. Me, i want to use a double (even though i've got a triple) because, darn it, Lance uses a double and of course I want to be like Lance. Does it mean I might wind up pushing a gear that's too big sometimes? probably. that being said, it's still an awful lot of fun to crush someone in a sprint with my triple when he's got a double... I dont crush anybody.I just ride.

Originally posted by farrenator
I have been riding a double chainring 53/42 with a 13-21 casette here in Washington, DC for 3 years now. It gets a little hilly but nothing bad. If I had to bike long, steep hills I would consider going to a smaller chainring for the double. It just seems to me that the 3rd chainring would get so little use. But then again, if I rode a ton of hills I might think differently. You just have to learn to look for the hills. they're here.

Originally posted by farrenator
I have been riding a double chainring 53/42 with a 13-21 casette here in Washington, DC for 3 years now. It gets a little hilly but nothing bad. If I had to bike long, steep hills I would consider going to a smaller chainring for the double. It just seems to me that the 3rd chainring would get so little use. But then again, if I rode a ton of hills I might think differently.

I use my triple for commuting with the front changer low screw adjusted to lock out the inner ring (effectively converting it to a double), but when touring, bring it back into play as a loaded touring bike and Scottish hills lead to a need for very wide gears.

I've always have had trips but never shift out of the middle cog so i guess a double would'nt hurt me much.

Whats wrong with singles. These days a 1x9 should suffice for rolling terrain. You have as many gears as an old 2x6 system. In London a lot of MTBs seem to be setup using singles.

I hear ya, I konw they are out there and I have done some, but for the most part it is flat and rolling hills as you know. No reason to go looking for that triple chainring just yet. In fact, my newest conversion is a fixed gear bike. Looks like I am regressing, hahaha.


Originally posted by FOG
You just have to learn to look for the hills. they're here.