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2- vs 3-Ring Crankset For A Not-So-Newbie(16 posts)

2- vs 3-Ring Crankset For A Not-So-Newbiedgangi
Sep 26, 2003 8:32 PM
Hello all -

I am buying my first road bike this weekend and need some advice -- 2 or 3-ring crankset? I searched the boards and have seen this topic debated a lot, but none of the discussions seemed to relate to me.

Most of the questions were posed by those just getting into biking. Even though this is my first road bike, I am not new to biking. I am a very strong mountain-biker -- light weight rider (150 lbs) who likes to sprint and climb. I am very fit and am not picking up road biking "to get in shape". I am already in shape and am picking up road biking because some of my friends are into it and riding my mountain bike with slicks just didn't seem a smart thing to do.

Anyway, I live in Arizona desert where the roads are relatively flat. I will occasionally ride in the northern part of the state where there are lots of mountains. But most of my riding will be done in Phoenix or Tucson.

So what do you think? 2- or 3-ring crankset for my situation? If I decide to go with a 2-ring crankset and want to swap out for 3-ring later, is this hard to do? Some bikes, especially the higher-end ones, only come with a 2-ring crankset.

Thx...Doug
If you're wondering if you should get a triple, then you...The Walrus
Sep 26, 2003 10:58 PM
...probably should. You could probably get away with a double around the desert, but between the climbing and the change in elevation up in the north end (Flag? Prescott? Sedona?), you'll be glad you had the 30t. Better to have it and not need it than to need it and not have it.
If you are in shape - go with a double crankGeoCyclist
Sep 27, 2003 12:02 AM
I bought my Dream road bike last fall (2002) with a double crank (two chain rings - 53/39). I hadn't been riding road bikes in 6 years, but I'd been doing a lot of mountain biking, and tandem cycling. My first few trips out riding on my new road bike I thought I had made a big mistake; as I'm surrounded by steep hills (15 to 20 % grade is not unusual). I started thinking about changing to a triple crank, and quickly changed my mind when I looked at the cost (new crank, front DR, Shifter, Chain on a DA set-up = $$$$). I was fortunate to meet up with a group of local road cyclist. These guys took me under their wing (lots of patience waiting) and taught me how to ride a steep grade. I can now climb hills in my 39 x 23 that I struggled to get up on my mountain bike. Last month I made it up initiation hill 1000 metres of 32% grade. If you are in good shape, want to ride in a fast group, go with the double and learn to climb! It you are planning to cruise, go with the triple. But whatever you do, just get out and ride!

Ride On!
try the mountains firstpowergyoza
Sep 27, 2003 12:04 AM
Hey, since you already have your mtb, you could give the hills a try first. Don't need to make a big ride out of it. All you need is 30-60 min on some of those mountains. Remember which gear combos work for you. Plug in the gear combos into sheldon brown's excellent gain ratio calculator: http://www.sheldonbrown.com/gears

After you get a list of useful gain ratios, you can easily test which gear combos would be identical on road chainring & cassette.

eg: The lowest gear you resorted to was say, 32/18 on 26" slicks w/ 175mm cranks. That'd be roughly the same as a 39/23 or 39/25 w/700c wheels & same length cranks.
That doesn't quite compute...NatC
Sep 27, 2003 4:33 AM
Simply using the same gears doesn't take into account that the road bike is about 10 pounds lighter, has about 110 psi in the skinny tires, has bigger diameter wheels, puts the rider in a more aerodynamic position, and lets the rider spin faster with the shorter cranks.

I used to live in Tucson and Ahwatukee, so I know the geography. If you're planning a ride with steep climbing you could toss on an LX cassette and derailleur (both for under $60).

Doug, get the double.
Fight the urge..go with the double!Wade03
Sep 27, 2003 5:13 AM
That doesn't quite compute...powergyoza
Sep 27, 2003 12:55 PM
NatC,

While I agree that bike weight, rolling resistance & rider aerodynamics would have an affect on rider speed and therefore gearing selection, I think the effect may be less than you imagine.

If the majority of Doug's climbs were at a significant grade, say 7% & up over long distances - I doubt RR & wind resistance will be huge at the speeds he's likely pushing - I mean, he's got high-pres. slicks already.

As for bike weight, 10lb is big, but if you factor that in as a % of total weight it's gonna be enough for 1 lower gear, maybe 2. Doug on his mtb: 150 lb + ~30 lb = 180 lb
Doug on a $2000 roadie: 150 lb + ~18lb = 168 lb
% weight savings: 6.7%
That's significant, but not a 40% weight loss if we took frame weight solely into account.

In addition, the beauty of Sheldon's gain ratio calculator is that it takes crank length and wheel diameter into account.

So I stand by the process I recommended, which was not meant to be precise anyway. Ride those mountains before you buy Doug! If for nothing else but the fun.
...and let's not forget about suspensionNatC
Sep 27, 2003 5:30 PM
If Doug owns a long-travel full-suspension mountain bike like many other southern AZ riders, then that'd make a big difference in climbing efficiency too. Sustained 7% grades are few and far between in AZ. Given that I ride both mountain and road, I think the difference between the two bikes is very noticeable.

Double!!!
re: 2- vs 3-Ring Crankset For A Not-So-Newbieal0
Sep 27, 2003 10:32 AM
There is absolutely nothing wrong with triple. Really there are absolutely no serious reasons against it. I'm unable consider in earnest "aethtetic" or or 100 gram weight increase. And I guess that few bucks more are of critical importance. Definitely it more then few if you go with DA, but in this case you likely aren't in very narrow circumtaints. So, go on with triple. And remeber - it is much cheaper to go with triple from the beginning then make double-to-triple upgrade.
Disadvantages of a triple vs. doubleChainstay
Sep 27, 2003 7:21 PM
A double will have a shorter cage on the rear derailleur and will shift crisper. There is more trimming involved when riding the middle chainring on the triple as opposed to the small ring on the double. The triple costs more and weighs more. The triple is less macho if that is important to you.

I switch my cassette to a lower gearing for the few times a year I get to ride mountains. Works fine.
Interesting pointsdgangi
Sep 27, 2003 9:48 PM
Thanks for the interesting points. The "long cage" vs. "short cage" derailleur setup was explained to me today for the first time. I did not know that a 3-ring front chainring required a long-cage derailleur (need to pick up the slack in the chain) whereas a 2-ring setup could go either way (most manufacturers equip with a short-cage if bike is spec'd with a 2-ring chainring). Since mountain bikes all come with long cage derailleurs, I never considered that short-cage derailleurs even exist!
That means I never considered the shifting difference between a long and short cage derailleur.

Somebody else also mentioned that they simply bought an extra cassette in the event they needed extra climbing power in the mountains. That seems like a cheaper alternative to swapping out the bottom bracket, crankset, and rear dearilleur for the few times I would want the granny gear (which is debatable in some circles). Some bikes do not have a 3-ring chainring option, so the only way to get there is to do all of this work.

Knowing this information, it definitely makes sense to go with the 2-ring chainring with my new bike purchase. Not only will I save face with my roadie friends, I will have a better shifting bike. And if I stay with the 2-ring setup on the big hills, my riding strength will hopefully improve...the reason I am getting a road bike in the first place.

Thx...Doug
Interesting pointsal0
Sep 28, 2003 3:37 AM
I would say that shifting difference between double and triple is much more imaginary than real. Feeling may be slight different but realibility is the same.

Price difference (if left out DA) is much less then extra cassete, especially if you buy new bike. It is possible to by bike with Ultegra triple for about 10 bucks more than the same bike with Ultegra double (the difference is much bigger for DA and, surprisingly, for 105).
Interesting pointsdgangi
Sep 28, 2003 7:42 AM
The price difference you mention is only if the manufacturer makes a 2- and 3-chain ring option for a specific bike, right? Some of the bikes I have been looking at ONLY come with a 2-chain ring crankset. If you want to swap it out for a 3-ring setup, you have to pay the difference.

Fortunately, the local bike shops have all been more than willing to accommodate me if I want to swap a 2- for 3-ring crankset. But in some cases the best they can do is change out the parts at cost, which still adds another $100 or more, and that did not include changing the derailleur to a long cage version.

Thx...Doug
Consider a compromise...dawg
Sep 27, 2003 11:41 AM
You could keep a double but get smaller chain rings such as a 46/34 set-up, if you aren't fond of the typical a 53/39. Most folks rarely make use of the harder gears with a 53.

Rivendell (search Yahoo) has a website, they carry some out of production 46 or 48/34 combos.

Good luck.
Good idea, but not so simpletorquer
Sep 29, 2003 1:04 PM
In order to fit the smaller chainrings, you need cranks with 110mm bolt circle diameter. The typical double road crank has a 130mm BCD, which limits you to a 38 tooth min. inner chainring.

The hot model in 110mm is the carbon fiber FSA "compact", used by Tyler Hamilton when he won his stage at this year's Tour de France, but they are $330 at Colorado Cyclist. TA, among others, produce 110mm models for much less; although their quality is probably somewhat less, its surely a more cost-effective approach.
Another Alternitive.......Len J
Sep 29, 2003 1:22 PM
is to equip your Double chainring bike with a medium cage rear Mountain Derailler (XT or XTR) and buy a Mountain Cog (12/32 or 12/34) This would allow you to have a low gear of 30 X 32 (or 34) for any Moutain endurance riding and still use a 12 X 23 for reqular riding. Cheaper & it works great with the Shimano STI shifters.

Len'