pbass

Interested in trying slightly lower gearing on my ss Cross Check, because it's basically doing mountain bike duty in very hilly terrain. Sees very little pavement or flats. Currently I'm at 42x19 which is around 61 gear inches. Low, I know, but not for where I ride I'd like to knock it down a little and see how it feels. I used to ride a ss 29'r MTB at 32x20 but I don't want to go THAT low, just a bit lower.
I'm a mechanical noob for the most part. At 42x19, I'm pretty much at the front of the sliding dropouts - any more forward and I'd start worrying about the grip there. I have a 38t chainring in the bin, but it's an 11speed SRAM and my chain is a 10 speed chain--I guess that won't work? I also have a 17t and 18t rear cog in the bin that were previously on this bike w the existing 42t front. So, I figure I could go with the 17t rear cog and get a new 36t chainring that'd put me around 58 gear inches which might do the trick. Just trying to get my head around this. Any suggestions appreciated.

seau grateau

I can't think of any reason the 11 speed ring wouldn't work with a 10 speed chain in this scenario.

pbass

Thanks. Just need a chainring nut tool and then I will try swapping it in. Might even see if I can put both chainrings on a la what this guy did: https://www.cxmagazine.com/gravel-bi...ost-found-2018

ofajen

How about you use your 38t chaining with the 19 for about 55 gear inches? If you remove one chain link, you should be pretty close to the same spot on the dropout as you are with 42/19. Or run 38/18 which would move you back about 3mm and be right at 58 gear inches.

Otto

pbass

I like this idea. Thanks. Just ordered the chainring nut wrench - seems I have everything else!

Sonofamechanic 

If your climbing that much, have you considered switching over to a heaver 1/8th style chain and rings? With that much torque the thicker rings might perform/last better? I would have guessed the chain would last longer too but recently have read that there isn’t all that much difference in wear between the wider/narrower chains.

Mikefule

1 tooth change makes a bigger difference if it is on the smaller of two cogs — which is usually the sprocket rather than the chainring.

Once you've decided on the ratio you wish to achieve, there are always several ways to reach it. I would choose on the basis of parts availability and price.

The practical differences of using one pairing or another to achieve a given ratio are debatable and probably not detectable in normal riding.

Whatever you choose it will not be forever. You will buy more chainrings and sprockets, We all do.

Personally, I think smaller looks better. That is, I'd rather have a smallish chain ring paired with a smallish sprocket rather than achieve the same ratio with 2 larger cogs.

pbass

Hadn't thought of that. Hmmm. I guess I'll see how it goes with what's in the bin, but that's something to consider for sure. I'm definitely "underbiking" the way I ride this sucker!

Moisture

For you, I think that ensuring your inseam is a precise fit for the crank arm length you're currently running would be more important
.

pbass

Interesting. New stuff to me. My inseam is 31 which based on the formula (I just Googled "inseam inches x 5.48 = crank length in mm" comes out to 169.88, and my cranks are 170, so pretty spot on. I would hesitate to get longer cranks as I've already got as much toe overlap as I like on this beast! It's a size 50 Cross Check, I'm around 5'7" fwiw.

Moisture

Definetly wouldn't want to go longer, you can probably get away with 175mm, but its not worth it.

Going short is also bad. My inseam is 34.6 . This puts me at 190mm. My knees simply dread the idea of ever going back to 175mm. I would have been forced to stop biking if I continued on with the wrong size cranks. You're getting a nice smooth spin with a full range of motion by using the right size crank arms, and this will give you a far better idea of what sort of gearing will work best for you needs.

Now, for 5'7, a 50(cm?) Frame might be a little small for you. What sort of bike is it? Some pics of your frame fit would be helpful. Before you decide for certain that you need a different gear, make sure that you're riding with an optimized frame fit.

aniki

ffs!

pbass

It's a Surly Cross Check with the notoriously long top tube. I actually had a 52 first. I could never get it quite right (with drops or flat bars - you should see my stem collection). I swapped the frame for a 50 and immediately felt more comfy, can make it work with drops or flats now too. Aside from overall comfort, I like the smaller size for the off-road handling in the rough stuff. I went with a 50 on my 650B geared gravel rig too (drop bar) - was also a little inbetween 50 and 52 when I tested them, but again I ride this one like a mountain bike for the most part, so I like the more compact frame.

Koyote

This has absolutely nothing to do with pbass 's question.

As usual, you are projecting your current obsession onto someone else's post.

pbass

Hey, rather than make a new thread - since I've got you all here.. Quick question: I've got these two freewheels/cogs here in my bin - the 17t and 18t. Looking at what tool I need to play around with these - one has 4 notches, the other has 6. Not sure about the one on the bike--will have to pull the wheel forward later and look. I'm looking at this: https://www.parktool.com/product/freewheel-remover-fr-6
But I'm not seeing a tool for a freewheel with 6 notches - is that unusual?

79pmooney

+1 You say ss Cross Check but go on to talk about cogs, not freewheels so I am assuming you are running fix gear. You say you want to keep your gears small, I assume for real hills. Now, if you ride up these hills, I trust you ride down them. In small gears, that means high RPMs (unless you walk or brake a lot). High RPMs means a high likelihood of throwing the chain off unless you set the chain slack to near zero. But: you are also talking of running cogs smaller than 42 teeth. That means you are not running a velodrome level crankset. (Those cranksets are made to be very round with accurately located chainrings about the bottom bracket centerline. On the velodrome, this matters big time. When a 200 pound muscleman throws his chain at 40 mph in tight company, it isn't pretty. But on the road, using derailleurs to take up chain slack, gears to keep RPMs reasonable and a freewheel mechanism so crazy pedaling is never needed, chainrings do not have to be round. In fact, being a touch oblong probably speeds shifting.)

Now, another factor in good fix gear setup is having real slack in the chain at all times. If the chain goes tight, the stresses it puts on the hub and BB bearings is very high. (If you go to the velodrome, you will see that everyone rides slack chains. They have this strange obsession with low friction and winning races.) We fix gear roadies have a more demanding requirement than those trackies, We ride bumps. We have chain tossing road feature they do not. This suggests we should ride slightly tighter chains. Yes, but ... not all of us are riding those carefully machined $200 cranksets. A lot of us ride road stuff. Those trackies can throw their bikes on a stand, spin the pedals and the chain slack stay exactly the same through several pedal revolutions. We do that and we watch our chains go tight, then loose. If we set the tight to still have a touch of slack to be kind to the bearings, the max loose is quite loose.

Now, to your chainring and cog choices - 10-speed and 11-speed chainrings are designed to shift easily. "Shifting" on a fix gear is throwing the chain. To prevent throwing the chain, you have to set your chain tighter. But if the crankset is not round (or hub but hubs are usually not much of a roundness issue) the tightest point of the chain slack/tight will be too tight. Far, far better than any modern 8, 9, 10 or 11 speed chainring are the old 5, 6 speed rings with squarer teeth and no pins, ramps or cutouts. (Getting harder to find though 144 BCD 3/32" rings for velodrome use are still made.) Even better are the 1/8" chainrings and cogs which must be used with 1/8" chains.

So if you want to use the small chainrings and a non-velodrome smaller BCD, look for MOJO 1/8" chainrings (I use down to 36 teeth on a 110 BCG crankset). (There are other brands that I have not tried. Ordering on-line from Mojo was straightforward and I have been pleased with the rings.) Really good cogs with nice square teeth are the Eurasian Industries 1/8" cogs. Chains that do not throw, last a long time and are not expensive are the Izumi Eco 1/8" chains (in several colors - all very good chains. Now that chain and cog combo is not quiet. I have found a near perfect relationship between quiet and easy throwing. I'll take noisy every time.

This is just based on my experience riding roads and hills fixed the past 45 years. I've thrown some chains and killed some bottom brackets.

Edit: I wish I'd seen those photos before I started writing!

pbass

Ha--sorry! That's the noob factor talking. I meant freewheels!

79pmooney

Apology accepted. Welcome to BF!

Moisture

79pmooney

I've noticed that the newer shimano derailleurs allow the chain to flop around quite a lot more than the vintage suntour and shimano's I've tried.

I always thought that the chain should be tight enough not to flop around too much. Whats better?

pbass

Thanks - I've been here for a while actually, but I've just recently decided to try and up my mechanic skills! I actually did the frame swap from 52 to 50 myself - had to buy a few tools. It was easy since I wasn't changing anything - I even had my same fork (I swapped frames w a guy who had the same color as mine - total score). So, little by little I'm acquiring tools, etc. The Cross Check is a great project bike.

Koyote

The discussion is about single-speed drivetrains. No derailleurs.

abshipp 

ACS makes their own tool for the "Crossfire" series freewheels

If you ever end up with an ACS "PAWS" freewheel, the FR-6 will work for those.

pbass

Awesome--thanks. I found this in that thread too - looks convenient, but it's almost $50.
https://www.amazon.com/ACS-151265-FW.../dp/B004IFP986

Cheaper to go with the FR-6 and the Crossfire-specific one you link to.

pbass

Well for the cost of a $5 chainring nut tool, I slapped the 38t I had on there, replacing the 42t, left the 19t freewheel on, so we'll see how I do at around 55gi. Will hit some fireroads today with some climbing. Didn't have to remove a link which was nice, so if this is too low for all-around riding I'll get a 40t and it'll be another easy swap.
After doing this I decided not to bother with the two-chainring experiment. Looks like it'd be interesting to try but with rim brakes it's clear I'd have to futz with the rear brake any time I made the switch. Plus, I already have a geared bike
Thanks for all the advice!

Sonofamechanic 

Now that’s exactly the right mantra for owning a single speed!