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Single chainring anyone?

Old 08-27-01, 06:12 PM
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HardBall
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Single chainring anyone?

I'm contemplating going to a single chainring on a Cannondale MTB. I have a 11-34 cassette. I believe something in the 36 tooth range would be Ok. Has anyone had experience in this area? Is there a manufacturer that makes a chainring for this purpose? No shifting pins, short teeth, grooves etc... Getting tired of hauling around all those redundant gears.

Any pitfalls? Any advantages other than the obvious.

Any info is greatly appreciated!! Thanks.
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Old 08-27-01, 06:46 PM
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Haven't done it but am thinking about trying it on a roadbike. Well I do have a fixed gear but that's a little different.

As I see it the advantages are this: Most riders don't use that many gears and with 8-9 now available at the rear you can simplify your driveline and save a small amount of weight w/o losing anything you don't use anyways. I have bikes with up to 27 "speeds" but seldom use more than 3-4.

OTOH as soon as you decide to do w/o something is exactly when you need it I seldom drop out of the 52 ring. I'm not very studly it's just very flat here and I'm fairly large so pushing the bigger gear is more efficient for me. However as local communities modernize their roads the relatively low drawbridges I ride over to the beach are replaced with bridges tall enough to let ships/sailboats pass w/o lifting. On THOSE things I do like to be able to drop to a small ring.
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Old 08-27-01, 07:47 PM
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you shouldn't have much problems getting that chainring. I've got 36 tooth Sugino on my singlespeed. Any bike shop should be able to order you what you need or check out www.webcyclery.com

The only problem that you may have is the chain may drop off the chainring on rough terrain. This can be solved by centering the front derailler over the chainring with the high and low stops and then locking the stops against each other. Try it without the derailler first though.
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Old 08-27-01, 07:57 PM
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Maybe I am reading your post too simply. Surely you know that there have been many models of bicycles with only one front sprocket over the years.

The only difficulty I see from your description is that you are going with a larger diameter sprocket (chainring) than your bike is presently equipped with.

This will surely cause stress on your derailure and will cause the derailure to pull harder against the sprocket teeth when you the chain is on the larger rear sprockets. This will cause your sprockets (chain ring) and chain to wear faster.

To overcome this, you should be able to add a couple of links to your chain.
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Old 08-27-01, 11:38 PM
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Originally posted by mike
The only difficulty I see from your description is that you are going with a larger diameter sprocket (chainring) than your bike is presently equipped with.
Um, a 36 tooth chainring isn't all that big. Just to clarify, chainrings and sprockets are not the same thing. Chainrings go on the front, sprockets go on the back.
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Old 08-27-01, 11:47 PM
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The single chainring set-up you mentioned is not as uncommon as you might think. I know several people who use it, at least one for off-road. It would be a good idea, for increased performance and better wear, to get a spindle length that will center the chainring in the chain line. I know of no reason why the single chainring will increase wear all by itself, sure the CR takes all the load and doesn't share it with other CRs, but you wo't be shaving off metal bits with shifting. You may have to try more than one size CR to find what works for you, you may use more than one size for different types of rides or for changing fitness during the year. The 36 tooth you mentioned would be as good as any other starting point. If you're more concerned about wear than weight try a steel CR, they're usually cheaper too
The Fr deraillieur idea may help, particularly in rough terrian
I know of people who prefer to train on and ride as their "main" bike, single CR bikes who have only one cog in the back, thus one speed, including mtn bikes. Overall maintence costs are less because there are fewer expensive parts to wear out, ( R derail. etc.).
One guy, I know, rode the Colorado District Championships on a ONE SPEED SCHWINN CRUISER and took 10th place, he would have done better if he hadn't had to stop to puke up some bad food he ate earlier. ( I found him his first cruiser and his first "Pro" bike, as well as teaching him to ride many moons ago).

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Old 08-28-01, 03:32 AM
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Originally posted by Allister


Um, a 36 tooth chainring isn't all that big. Just to clarify, chainrings and sprockets are not the same thing. Chainrings go on the front, sprockets go on the back.
Thanks for the clarification, Allistar. I am around machinery most of the day. To me, if it has teeth and a chain goes around it, it is a sprocket, BUT, for the bicycle folks, "chainring" it is, rather than "front sprocket".

Don't be fooled by the fact that a 36 tooth sprocket, 'er "chainring" is only "a little bigger" than the smaller chainring it is to replace. A small increase in diameter can make a big difference in circumference and the chain take-up. This results in a greater load on the derailure spring and the chain itself.
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Old 08-28-01, 04:25 AM
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Originally posted by mike
Don't be fooled by the fact that a 36 tooth sprocket, 'er "chainring" is only "a little bigger" than the smaller chainring it is to replace. A small increase in diameter can make a big difference in circumference and the chain take-up. This results in a greater load on the derailure spring and the chain itself.
To put it in perspective, the chainrings on my mountain bike are 24, 34 and 44 tooth. I believe road bikes use up to 59t rings and small wheeled bikes like Moultons can have 64t. The amount of chain takeup that the rear derailleur needs to handle is determined by the range from largest to smallest gear, so a single chainring bike actually needs less chain takeup that a triple ringed bike.

On the wear question: yes a single chainring will wear quicker, but you could always use a heavier duty item without too much of a weight penalty - and to be honest, I don't believe the few grams that getting rid of a couple of chainrings saves will be all that noticeable anyway.

Actually, that brings up another question. How much weight do you have to shave off a bike before there is a noticeable improvement in perfomance? 1 gram? 10? A hundred? I'm more interested in 'static' weight here, not so much the rotating weight of rims and tyres. Any insights?

Last edited by Allister; 08-28-01 at 04:31 AM.
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Old 08-28-01, 04:54 AM
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Originally posted by Allister
...On the wear question: yes a single chainring will wear quicker, but you could always use a heavier duty item without too much of a weight penalty - and to be honest, I don't believe the few grams that getting rid of a couple of chainrings saves will be all that noticeable anyway.

Actually, that brings up another question. How much weight do you have to shave off a bike before there is a noticeable improvement in perfomance? 1 gram? 10? A hundred? I'm more interested in 'static' weight here, not so much the rotating weight of rims and tyres. Any insights?
Thanks everyone for the info!! I'm 6'-1" 270 lbs so a little extra weight of a steel CR will not be noticed! I am weight conscience (at least on my bike) within reason, but with the fore mentioned attributes I can't really tell much difference other than changes in the rotating weight.

Sometimes it's that psycholcgical boost of having the newest, coolest, lightest toy on the block. No, I'm not a pozer I really ride but hey I like the new stuff too. After all as much as I hate to admit it I'm human too. ;-)
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Old 08-28-01, 05:33 AM
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Umm...could you explain how the DERAILLEUR (please, note spelling) can PULL HARDER on the cogs?:confused:
The derailleur is on the "slack" side of the cogset, and will pull the same amount, regardless of how much force is transmitted through the chain. The only "pulling" a derailleur does is that which the return spring does.
Please clarify this, Mike. Don't worry about using technical jargon, as I am a mechanical engineer.
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Old 08-28-01, 08:11 AM
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Old 08-28-01, 08:32 AM
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O.K., that is a possibility. It is usually easily solved by adding 1 link to the chain (but not always-see below). Easy solution to a problem which was made more complicated by a misunderstanding.
While we are on the subject of derailleurs, chains, and cogs, let me talk for a minute about capacity. This is a technical term, which refers to the amount of slack which the derailleur is capable of handling. Simply put, it is the difference in the # of teeth in the big-big combination, compared to the small-small combination.
If you were to have, say, a 30-40-50 ring setup, and 13-28 cogs, you would need a derailleur with a capacity of (50+28) - (30+13) = 35 teeth. If the derailleur doesn't have that kind of capacity, then the chain will be under tremendous tension in the largest gear combination. The jockey wheels may hit the cogs, and you may not be able to shift up at all. Of course, everybody knows (don't they?) that you should never use the big-big combination, right? The solution to THIS problem is a longer derailleur cage, not extra links.
Some people who use "alpine" gearing know that, in order to get that "really low" cog on the bike, they will exceed the capacity of the derailleur. As long as there is a decent tooth count gap between this cog and the next lower cog, and the rider doesn't try to use the big-big combination, there should be no problem.
For people who wish to do this, it is VERY important that they know what the limitations of just such a setup are. People do this all the time without any problems.
On a single chainring, however, there is ONLY the derailleur capacity to work with. On road bikes, the better derailleurs rarely come in long-cage versions. The longer the cage, the more clumsy the shifting. If you are trying to get a larger range (say 11-34) with a single chainring, you may very well need to use an ATB derailleur, or at least a touring derailleur.
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Old 08-28-01, 09:40 AM
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I think that is kind of what Mike was leading to. With a single medium size chainring, one would have to use correspondingly larger cogs to acheive the same gear inches. On a mountain bike, this could get kind of extreme. Good point about derailleur capacity, D*Alex. I actually run an XT derailleur on the otherwise 105 group on my commuter because I am still at a modest conditioning level and paranoid about hills. My commute is flat, but with a quick cassette change and derailleur adjustment, I can handle anything I might encounter on a hilly country ride. Shifting might be a little crisper with a 105 derailleur, but, hey, it's a commuter not a racer. I would probably go with the road derailleur now, but my conditioning was even MORE modest at the time.
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Old 08-28-01, 01:17 PM
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I use a 1x8 drivetrain. My chainring is a 32t, I'm about to switch to a 34t or 36t. I use a 11X32 Sram 8 speed cassette. I also use a BlackSpire chainguide to keep the chain in place(see pic). This set up works really well for me here in Louisiana, its really flat here. When I go some place with hills and climbs I struggle up hill a little more than my buddies. Oh yea I use just a regular truvative chainring with ramps and pins.
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