Dont start out 42-18
 

I just finished converting my Surly to a SS and put on a 42T chainring with a 18t rear sprocket. I didnt want to over-do it so I went conservative on the gearing. I pedaled as fast as I could and I bet I was only going 15mph. I got on it and laughed the whole first mile. So my question is; What is a little better gear combination combination for all-round riding, moderate hills, mostly get around town type of riding.

I would very much like to avoid trying three different chainrings and three different sproket combo before finding a happy medium. Any thoughts?

42x15 or 42x16 are quite common. Lotsa folks in SanFran use the 42x16 combo and can get up all the hills. I live in Seattle and I run a 42x15 for around town, and am thinking about getting a 14t cog for the days I want to go faster and farther.

Yeah that is pretty low. My first double was a 52/42 with a 13-22 six speed. That 42-18 would have been one of the lowest gears on there. I would hate to ride on flat ground with something like that (good for hills though). It would take all day just to go anywhere.

Gearing questions are tough because we don't know the conditions you'd be riding.

I understand for sure. I am just looking to see what other people might be riding. I might be able to zero in on a good gear combo a little quicker and with less trial and error.

The conditions I ride in (90%of the time) are moderate hills, lots of flat open roads. Occasionally, I do encounter some very steep mountain climbs as I do live right up against some very large towering mountains.

Now if Im riding under varying conditions I bust out my bike with 2 chainrings and a gear cluster.

One gear is a tough comprimise. We also don't know how much you weigh and how strong you are?

I weigh in at 175lbs and I would consider myself an above average rider as far as strength goes. Pounding up a hill is something that is usually not a problem.

I understand the "tough comprimise" of just one gear, but for me thats the beauty of it. I love the simplicity of just one gear. I got so tired of trying to find the right gear all the time. Plus switching over to a SS took the weight of the bike down to around 15 or 16 pounds.

I'm still not clear of the advantages of calcultating gears with gain ratio vs. gear inches. I use gear inches, and I think 70 gear inches is a good starting point. Many people ride close to that ( a 42 x 16 is 69 and a 42 x 15 is ~73.5 ). Hills will be fine, but you won't be spinning like mad on flats. You just won't win any sprint races. People on flatter grounds will increase up to more like 75, and maybe people with more hills might drop down to 68 or so. FYI, your current gearing puts you at about 61, which yes, would make me laugh too.

Go for 70. Most people seem pretty happy around there.

Here is the link to the calculator:

sheldon brown gear calculator

Be sure to switch it to gear inches and put your cog size in one of the boxes where it says custom cassette. You can enter in numerous chain ring and cog sizes at the same time if you want to compare.

Exactly what I was looking for. Thanks. That Sheldon Brown never ceases to amaze me.

48x16 on my commuter, 48x15 on my track bike. I live in Pittsburgh for the summer and there are some killer hills which are challenging to ride with my ratio, but there are very few I can't mash myself up. Sure I was struggling at first, but after a month in this one gear I can FLY.

I lived in Seattle for 9 years and I used a 42x16 (69") and it worked just fine on most hills. Well not all. I never even tried getting up Queen Anne hill. But it worked just fine getting from downtown to say the top of Capitol Hill, or climbing from the UW to Broadway.

Its also enough to keep up with cars on normal streets. But you get enough control for gliding around peds.

I'm a wimp, I guess. I'm happiest around 65" for the road, and in the mid to low fifties for the dirt.

Most of what you are hearing doesn't mean anything. (these guys ride different areas and may or may not be same fitness) These are apples to oranges comparisons.

Best thing to do would have been to ride around with your geared bike on the course/road conditions you expect. Then experiment with what single gear works best on the gear bike.

Once you have determined that play around with the gear calculator and come up with the chainring/cog that is equivalent.

I disagree w/ 53-11. I tried that when I started and its not the same. At least if you are going fixed. Fixed pedals don't stop to coast and the momentum works with you, so what seems like a tough hill on a free wheel seems much easier to me on a fixed (given the same ratio) since the momentum helps me continue to pedal. Plus, after a pretty short amount of time of riding fixed, your stronger legs will get you up hills easier than you ever did before. I FLY over the bridge that used to kill me when I did it in an easier gear on my 10 speed back in the day.

At least that was my experience.

Well that and the cranks may be shorter (changes the gain ratio).

But gearing questions are like asking how long is a rope? (we don't what he needs)

What you said about the fixed drivetrain is interesting and is something to take into account.

i'd say also around a 42x15, I used that or a 42x14 in relatively flattish NJ/PA area. No major climbing but some steep grades here and there for short distance were ok.

I concur.

This I agree with.

I'll add in the difference in crank length if you have 165s changes things also. (gain ratio changes, but gear inches don't)

Momentum is the same with both bikes (fixed vs freewheel). Although drivetrain efficiency may be greater with fixed and I won't disagree with that.

Momentim is momentum that doesn't change.

shorter cranks = taller gear, given the same inches, right?

you're discounting the effect of "drivetrain momentum" (I think I just made that up)

Yeah...... it feels taller with a shorter crank , but the gear inches are the same.

On a shorter crank you pedal a smaller circle so you apply more force to get the same rpm for any given gear ratio.

Balancing this out ......On a Longer crank pedal speed has to be higher (at any given rpm) since the distance to pedal one circle is greater.

Don't ask me which one is better...that's controversial.

Yes, this so-called drivetrain momentum is what I mean. On a free wheel, if you are going up a hill and you stop pedalling, the drivetrain just stops cold, on a fixed, the momentum of the drivetrain re-enforces your own motion, helping you out during those moments where you just feel like you can't get another revolution out of your legs. Its probably not much, but I definitely notice it.

Also, if you're used to riding free on platform pedals then you're used to only getting power out of the downward motion of your pedal stroke, instead of being able to apply force at all parts of the revolution like you can when clipped in. This makes hills a lot easier as well and probably also added to my opinion about why hills seemed much easier with the same gear ration when I made the switch to fixed, but obviously this doesn't apply if your freewheel bike had clips as well.

Ok, if you stop cold that is a different story.

Drivetrain inertia huh? I think I can see that helping a little. As long as you are carrying speed the pedals pull your feet around a little. Ok, I see your point. The thing you still have to input energy though or else you will lose this.

The thing is any bike has momentum. When I pedal up hills with a freewheel bike I definitely try not to downshift to keep the the weight of the bike and me rolling forward.

drivetrain momentum is what makes some people complain that riding fixed actaully *hurts* their spin, rather than improves it.
It makes some people lazy, in that the rear wheel pushes the pedals past the dead spot in the crank rotation.

i also agree fully... i "practiced" on my geared bike at 42x16 but on the fixie 46x17 (slightly taller) turned out to be more appropriate.

difference here is that we all have fixed gear bikes and 53-11 doesnt. people giving advice over things they dont know about... such is the internet...

Wow....I can see your point about the dead spot.

I can see the rotational inertia guys now saying that's why they use deep V's citing some extra "dead spot reducing flywheel effect".

zing.