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-   -   Uncle Sixty's Gearing Primer for Newbs (http://www.bikeforums.net/singlespeed-fixed-gear/716371-uncle-sixtys-gearing-primer-newbs.html)

ThermionicScott 10-17-12 09:52 PM

Quote:

Originally Posted by silmarillion (Post 14852915)
Because my cadence is too high on the flat areas I do ride. If I go to the the Silver Comet Trail, which is pretty flat. I would like to be able to ride a little faster and keep my cadence around 100-110.

Go ahead and try bumping up your gear a little, but as posted earlier in this thread:

Quote:

Originally Posted by Sixty Fiver (Post 12499231)
If you are not regularly spinning out the gear you have now a taller gear is going to slow you down as your cadence will drop.

My current gear of 71" isn't high by most standards but I'm thinking of dropping it back down to work on my spin. :D

silmarillion 10-18-12 05:50 AM

Thanks for the info.

Actually the 46/18 I'm riding now seems to be good for my commute to work. Especially when I get to the climbs. However I have a few long stretches that are flat, and I'm thinking I'm a little too low in those areas.

Your right though. I'm going to flip the wheel to ride fixed and go out to the SCT. That will be a 46/17 and I'll be able to ride 50+ miles on relatively flat terrain. This will give me a better idea if I need to bump it up or not.

That being said, let me ask this; My bike came with 130bcd. What brand names of chainrings are known to be better when it comes to construction, design, and durability? I've been glancing at Sugino, Chopsaw, Pake...etc (hope I got the names right...) I don't mind spending a little more to get a better chainring, but that may not be necessary if there is a particular ring that experienced riders prefer to use.

I'm a noob at this...And I realize that a lot is really going to depend on me, and the way I train/ride.

prooftheory 10-18-12 05:52 AM

Look, I'm really not trying to be a jerk here, it just seemed like you were doing something that didn't make the most sense. My point was that with a road single speed a 46t chainring should be adequate for just about every situation. You say you have a cadence of 100 to 110. At 46x14 that would be from 26 to over 28 mph. Do you really think that you are going to be going faster than that for very long? I have no issue with someone wanting to gear down but in that case
Quote:

The cheapest way to change gearing is to change your rear cog
Cogs are also a lot easier to change in and out for different situations like commuting versus time-trialing on a trail.

If you want a bigger chainring because there are better ones at 48t or 53t or you are trying to get more skid patches then it makes sense to get a bigger chainring, but the reason you gave didn't seem to justify it.

silmarillion 10-18-12 08:21 AM

Oh no, I don't think I can ride like that...I would say that I'm fairly strong and I ride well at a 90+ pace. There are some awesome looking chainrings out there. Bling

So you suggest dropping down to a lower fixed cog then? Okay good enough I did read that. I'm not worried about skid patches, and the chainring I have now is fine. If I TT on the bike I'm going to ride it fixed anyway, so it really doesn't matter about the freewheel I use for commuting.

Now that would make more sense to me now that I think of it. Same way on my geared bike. When I'm riding the 48, and I need more torque, then I shift to a lower cog. I don't run out and get a 52t chainring. That's a little clearer to me now.

The best way for me to be sure is to go ahead and ride the 46/17 I have now and see how it goes. I need to rig my bike with the cadence and speed sensors so I can monitor them with my HRM.

You're not being a jerk my friend. Nor are you being a post Nazi. (my apologies) Sometimes, knuckleheads like me need a little more clarity without having to sort through a field of opinions, but this thread is awesome. I have actually cut and pasted some of the good details to a document for future reference.

I'll learn. It's only my second week on a ss/fixie

prooftheory 10-18-12 08:28 AM

If you just want to test an even bigger gear inches Retro-gression.com has 16t cogs on sale for $1 right now.

silmarillion 10-18-12 10:43 AM

Quote:

Originally Posted by prooftheory (Post 14854398)
If you just want to test an even bigger gear inches Retro-gression.com has 16t cogs on sale for $1 right now.

Heck yeah, that's what I'm talking about. I'm gonna go get one right now. At least I'll have it...

chas58 10-18-12 11:37 AM

Silmarillon, To choose gearing, I pick my realistic cruising speed, and my target RPM.

When commuting, my cruising speed is 20mph with and RPM just under 100. So 71 Gear Inches works good for me. If I have a max RPM of 130, that would give me a sprinting speed of 27mph (this will vary with conditions and length of sprint).

If you are realistic of your comfortable cruising speed and RPM, choosing gearing is straight forward. If in doubt I would go lower. Lower gearing gives me a higher average speed on a route (better FG acceleration and deceleration) with a lower ultimate top speed.

silmarillion 10-18-12 12:33 PM

Quote:

Originally Posted by chas58 (Post 14855201)
Silmarillon, To choose gearing, I pick my realistic cruising speed, and my target RPM.

When commuting, my cruising speed is 20mph with and RPM just under 100. So 71 Gear Inches works good for me. If I have a max RPM of 130, that would give me a sprinting speed of 27mph (this will vary with conditions and length of sprint).

If you are realistic of your comfortable cruising speed and RPM, choosing gearing is straight forward. If in doubt I would go lower. Lower gearing gives me a higher average speed on a route (better FG acceleration and deceleration) with a lower ultimate top speed.

Thanks chas, sounds like we are pretty close. Now is your cruising speed of 20 your avg speed, or just the sweet-spot between candence/speed?

Right now I'm at 67gi.

frantik 11-01-12 06:07 AM

Setting up a single speed rain bike.. Using 42x18 right now (60.1 gear inches with 26x1.9 tires) good for acceleration but really have to spin it in the flats (and it's all flat around here) I tried 42x16 (67.6gi) which was much better for top speed but for "cruising" I felt like I was well out of my desired cadence and having to mash . I guess that's part of riding a SS.. basically feeling like you're in the wrong gear most of the time LOL. Gonna try to hit someplace in the middle and see how it works out, though I haven't actually tried riding in the rain yet.. usually I recall wanting a slightly lower gear than when running on dry streets. On my main ride I'm running a 46t front ring and I usually end up in 46x19 (62.3gi).

I'm not sure if it's because I'm riding 26" fat tire MTBs in city traffic but gear inches of 70-80 sound pretty nuts to me.

ningnangnong 11-01-12 09:30 AM

I'm about to go and pick up a Langster and will be changing the gearing since I find the 69" too low, but having read a number of threads and thought I was clear on what I was going to go for, no longer am.

What makes some people opt for even numbered rings and others odd?

The Langster is 42/16, and I would naturally think of dropping to 42/15, but some opt for 39/14.

Why?

Thanks

ThermionicScott 11-01-12 11:05 AM

Quote:

Originally Posted by ningnangnong (Post 14902730)
What makes some people opt for even numbered rings and others odd?

The Langster is 42/16, and I would naturally think of dropping to 42/15, but some opt for 39/14. Why?

In a nutshell, this: http://sheldonbrown.com/fixed.html#skid

JohnDThompson 11-01-12 02:34 PM

Quote:

Originally Posted by ningnangnong (Post 14902730)
What makes some people opt for even numbered rings and others odd?

If you do skid stops, a chainring with a prime number tooth count will give you the maximum number of skid patches regardless of what the rear cog tooth count may be. The only "even" prime number is two, and both 43 and 47 are prime numbers with tooth counts in the range where most people prefer their gearing.

prooftheory 11-01-12 02:47 PM

Other considerations:
It is cheaper and easier to change a cog than a chainring.
A longer chain (by using a larger chainring/cog combo) wears out less.
Larger chainring = more street cred.
I thought that sheldon brown had a theory that said something like you should have an even number of teeth (cog + chainring together) to have a longer chain life but I can't for the life of me think of why that would be the case.

lhbernhardt 11-01-12 04:36 PM

Just a few other things to consider:

Yes, it's cheaper to change the cog, but in general, a one-tooth cog difference is about 6 gear inches. A one-tooth chainring difference is about 2 gear inches, so you get a finer gradation in gearing. This is mostly useful in track racing, where you might do a mass start in 49x15 (88 inches), then go up to 50x15 (90 inches) to ride a pursuit, or because you felt you were getting spun out when the pack dropped the hammer, but you didn't want to go as high as 49x14 (94.5 inches).

Another thing to consider is equivalent gears using big/big vs small/small. Track racing lore holds that sprnters will generally use a small/small combination, while a pursuiter will use a large/large. You might scoff at this at first, but let's take a closer look:

Most people thinkj that it's all about leverage, but the only thing that affect leverage is the length of your cranks. So assuming you're using 165's with both ratios, what's gong on? Let's take an 88" gear. You can do this with 46x14 (88.7) or 52x16 (87.7). Close enough. So if you spin them at 120 rpm's, you're moving the chain at 92 links per second (46x2 revs per second) with the 46, and at 104 lnks per second with the 52. That's a 10% difference. So if you're accelerating the bike with the 46x14, you only have to accelerate the chain to 90% of what you'd accelerate it to with the 52. But once you've got the gear moving, it's way easier to keep the chain moving at the greater momentum provided by the faster chain speed.

And it's not necessarily easier to change the cog. Changing the chainring is really quick, especially if you have the old Campag 5mm "pregnant" wrench and you are using the actual Campag track fixing bolts. These allow the allen key to go all the way thru the bolt, so you can stack all five bolts onto the wrench. So it's an easy thing to move quickly from bolt to bolt, stacking each bolt as you move along, then swap chainrings, rebolt, then adjust the rear wheel. You don't even have to take off the rear wheel (as long as the same chain length is accommodated), you just adjust it in the track end.

Back when I first started riding fixed in the winter back in California back in the 70's most guys rode 66". I remember Mike Neel coming for a group ride one day on a track bike with front brake, and a tubular wrapped under his saddle along with a Campag peanut butter (15mm) wrench. It was early in the season, but he was right up there in the town line sprints against guys on gears. I was really impressed; I've been riding fixed ever since; in the winter while racing, and now just about all the time. My best gear on the road is 44x17 (69"), but I live in a hilly area around Vancouver, BC. I think that the fitter your are, the lower you can go (up to a point). I rode the 44x17 in Paris-Brest-Paris last year & for all of my California Triple Crown rides this year, and all of them were quite hilly! You can ride fixed for just about anything.

Luis

DrDuktayp 12-01-12 12:41 PM

Hi all

I am putting together my first SS (although I am considering SS/Fixed). I am a new older rider at 47 years old 5'10" and 160lbs and live in a hilly community. My ride home is up hill from about 15 feet elevation to about 260 feet. Most of the ascent is a steady grade over a distance of 1 3/4 miles. There is a short dip and then a very steep section that is about a hundred yards or so just before my home.

After reading through many posts and threads on gearing, cranks etc. I have come to the following conclusions for a start point on this conversion. I hope that as I put in time and miles I will be able to increase my gear inches.
165mm or 170mm cranks (I currently have the 170mm but looking at 165's)
Gearing at or below 60" (learn to spin)
brakes front and back (rain and ice)

This thread being all about gearing I am so far planning 42/20 or possibly 42/18 to start. Does this sound like a good start point for me?

Thanks
Tom

ThermionicScott 12-01-12 02:24 PM

Quote:

Originally Posted by DrDuktayp (Post 15004804)
Hi all

I am putting together my first SS (although I am considering SS/Fixed). I am a new older rider at 47 years old 5'10" and 160lbs and live in a hilly community. My ride home is up hill from about 15 feet elevation to about 260 feet. Most of the ascent is a steady grade over a distance of 1 3/4 miles. There is a short dip and then a very steep section that is about a hundred yards or so just before my home.

After reading through many posts and threads on gearing, cranks etc. I have come to the following conclusions for a start point on this conversion. I hope that as I put in time and miles I will be able to increase my gear inches.
165mm or 170mm cranks (I currently have the 170mm but looking at 165's)
Gearing at or below 60" (learn to spin)
brakes front and back (rain and ice)

This thread being all about gearing I am so far planning 42/20 or possibly 42/18 to start. Does this sound like a good start point for me?

Thanks
Tom

Since you're using a freewheel, 60" won't be a problem going down hills. I like it as a starting point. :thumb:

aquateen 05-16-13 07:20 AM

I'm thinking of changing my rear cog on my SSCX. Right now I'm running 38/16 and thinking of moving up to 18 with 700x38 tires . It's mostly my around-town bike but I just moved to a hilly area and would also like to take the bike out on some easy single track. Thoughts?

hairnet 05-16-13 09:06 AM

Won't hurt to try.

sinikl 05-16-13 09:20 AM

i would think you'd be spinning to F on group rides (having just done a group ride last week with someone on a SSCX bike), but if you're solo, who cares. it's only ~25 bucks for a cog.

aquateen 05-16-13 09:25 AM

Won't be taking this on group rides. This is an around-town bike/grocery hauler that I can hopefully take on some trails.

1 spoke 10-18-13 03:15 PM

I don't get what gear inches are

prooftheory 10-18-13 03:18 PM

Sheldon Brown:
Quote:

One of the three comprehensive systems for numbering the gear values for bicycle gears. It is the equivalent diameter of the drive wheel on a high-wheel bicycle. When chain-drive "safety" bikes came in, the same system was used, multiplying the drive wheel diameter by the sprocket ratio. It is very easy to calculate: the diameter of the drive wheel, times the size of the front sprocket divided by the size of the rear sprocket. This gives a convenient two- or three-digit number. The lowest gear on most mountain bikes is around 22-26 inches. The highest gear on road racing bikes is usually around 108-110 inches. Unfortunately, the handwriting is on the wall for all inch-based measurement systems.
You could multiply by pi to get the actual distance traveled per revolution of the crank in inches.

seau grateau 10-18-13 03:19 PM

http://bit.ly/16lqPQ3

Coluber42 10-18-13 03:47 PM

For what it's worth, I have done a lot of long distances fixed (multiple hilly 1200k's, 1000k's, etc) and have ridden with a number of other people who made a habit of doing the same thing. I ride a 42x16 with 165mm cranks and 25mm tires for everything, IOW, about 70". Most of the other guys I've ridden with who were experienced distance riders on fixed used gear were using gears between around 64" and 76". What I have found is that getting comfortable and efficient over the long haul requires a couple of things: the first and more obvious is spinning fast, smoothly and comfortably downhills. It takes some time to get really smooth and comfortable so you aren't slamming your butt against the saddle on every stroke and so that it doesn't wear you out too quickly. The other thing is figuring out how to find a comfortable rhythm at really low RPMs. On short hills you can afford to just power up, but if you have longer, sustained climbs you have to be able to figure out how to get up slowly enough that you aren't going to just blow up, and easily enough that you don't over-strain your knees, achilles, etc. Which one of those two things you're better at might also inform your gearing choice - for example, if you have a hard time getting over the top of the pedal stroke at really low RPMs but you can spin fast comfortably, go with a lower gear. If you can keep it going at really, really low RPMs but spinning fast is uncomfortable, go higher.

My commuter bike has the same gearing (slightly wider tires though), and although I am too lazy to change it, if I were to do anything I'd go lower. I often carry heavy panniers on that bike, and I ride it with street shoes and toeclips which don't give as much leverage as being clipped in. I also let the drivetrain get a WHOLE LOT skankier before doing anything to it maintenance-wise, and I ride it through snow and stuff in the winter. All of those things add up to making it harder to pedal, so that's another reason to go with a lower gear (although as I said, I am too lazy and it's ok the way it is).

1 spoke 11-27-13 01:39 AM

so im 15 and weigh 126, would pushing a 50/18 ratio be good


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