Let's Talk About My Chainwheel...AND THE ANSWER IS.....

[55ColumbiaBuilt]

I recently got a Rollfast with a skip-tooth configuration and a 24 tooth chainwheel. I also got some fenders for the bike from right here on the forum. The problem is the clearance between the rear fender and the tire....tight at the top, wide at each end of the fender.The axle sets deep in the dropout. Here's the question. If I convert to a 26 tooth chainwheel, will this move my axle forward in the drop-out, the wheel/tire further from the fender brace on the seat stay, and closer to the fender brace on the chainstay? Enough to make a noticeable difference? Thanks in advance.

My Rollfast

The Fenders

 

[X-RAY]

Re: Let's Talk About My Chainwheel

why do you want a new chainring, for gearing or just to move the tire? i would think playing with chain lenth would do the same as changing the ring, but you almost sound like you want a different ring and wanna know if it will work.

 

[deorman]

Re: Let's Talk About My Chainwheel

Changing the ring will definitely effect wheel positioning. It may work, but too much change and you'll have to add a link.
You're probably not going to get more space at the top mount that way.

 

[55ColumbiaBuilt]

Re: Let's Talk About My Chainwheel

why do you want a new chainring, for gearing or just to move the tire? i would think playing with chain lenth would do the same as changing the ring, but you almost sound like you want a different ring and wanna know if it will work.

Playing with the chain length means pulling TWO links...one short one long. How big a difference will that make? Might that cause the axle to fall short of nesting in the dropout?


I'm looking for my best option to make the bike and the fenders get along.

 

[deorman]

Re: Let's Talk About My Chainwheel

The axle moves back or forth 1/2 the distance you add or remove in chain links.

 

[55ColumbiaBuilt]

Re: Let's Talk About My Chainwheel

The axle moves back or forth 1/2 the distance you add or remove in chain links.

And if I get a bigger chainring?

 

[deorman]

Re: Let's Talk About My Chainwheel

The axle moves back or forth 1/2 the distance you add or remove in chain links.

And if I get a bigger chainring?

Too much math for me. :lol:

 

[55ColumbiaBuilt]

Re: Let's Talk About My Chainwheel

The axle moves back or forth 1/2 the distance you add or remove in chain links.

And if I get a bigger chainring?

Too much math for me. :lol:

Okay then...What is the diameter of a 26 tooth skip tooth chainring. I'll do the math. I'll move the axle forward in the dropout, measure the distance to the fender braces, and look at the slop in my chain to see if it will accomodate a 26 tooth. The reality now is, something's "jacked"! If it isn't, then why the big difference between my tire and two fender stays? I bet Shyder built this bike with fenders. Just so you know, I bought the bike from a "picker" who told me he moves 200 bike annually. When I got it, he had done a considerable amount of work to the crank assembly....but no other part of the bike. I thought nothing of it at first, but could there have been a more desirable chainring on the bike?? A 26 tooth maybe?? I don't know, and I want you all to know that I'm not being argumentative with you, honest. :wink: I appreciate all the help you will share with me. I also know that a larger chainring will change the preformance of the bike...probably for the better. Maybe a more simple question from the very beginning would have been...

Does Anyone Have A 26 Tooth Skip Tooth Chain Ring That Will Fit On My Rollfast?

 

[B607]

Re: Let's Talk About My Chainwheel

I've got this ring. PM me if interested. I'll sell it to you cheap. Gary

 

[55ColumbiaBuilt]

The question was.

"If I convert to a 26 tooth chainwheel, will this move my axle forward in the drop-out, the wheel/tire further from the fender brace on the seat stay, and closer to the fender brace on the chainstay? Enough to make a noticeable difference?"

AND THE ANSWER IS.......

YES!

I'd post a picture, but I didn't post or take a "before" picture to compare it to, but the answer to the question I posted at the beginning of this thread is a simple YES!

 

[sailorbenjamin]

Changing from a 24 to a 26 will give you almost exactly the same change at the axle as taking one long and one short link out of the chain.
Think about it like this, the chain goes halfway round the big ring. If you make it got 13 teeth instead of 12 teeth to go the half way, that will leave one less pair of links to go the rest of the way to the little cog and back.
Here's the question. Is it hilly where you live? The 26 will give you almost 10% higher top speed but it will also cut your hillclimbing ability by that same amount.

 

[Unchained]

I'm kind of a hack when it comes to gearing, but here's my experience and brute force solution.

I have an EMORY (Snyder tubing, made after Snyder went out) cruiser that had this same exact problem. (Go figure... I have the same rear triangle as your frame I think)

I had a 46 tooth 1/2" pitch chainring up front, the original one, and with an 18 tooth cog on the rear wheel, I just could not get my wheel to sit right in the fender. It was tight at the top, that was never the problem really. I couldn't get the chain adequately tight by removing links without the tire rubbing up front at the chainstays. The wheel was pulled as far back as the chain would allow, and it was just no good.

So I add two links... the wheel sits ok but the chain is too loose. :x

I had an idea at this point. I traded my 18 tooth cog on the hub for a 19 tooth and left the front chainring. That solved it. I think I put two links back into the chain and that combined with a 19t cog out back was just the trick.

Experimenting with rear cogs might work for you as it did for me. I think, correct me if I am wrong please, that what trading a cog with an even # of teeth for one with an odd # count does is break the two link cycle, where removing two links is too tight and adding them is too loose. It just adds an extra, odd tooth into the mix.

I believe, I could be wrong here too, that you can get what's called a 1/2 link- has male and female chain ends, so to speak, that replaces 2 ordinary chain links. I've never used one, but I think it would solve the problem the same way my brute force odd count cog method did.

Interestingly, I can run an even tooth count cog out back if I put an odd one up front. It seems to be reversible.

Granted, these solutions are kind of finicky because you're altering gearing for a visual appearance thing. :| It's not all that ideal, but it seems to work.

At least in my case, I think somebody goofed when making my frame. The stamped steel dropouts stick out of the chainstays more than on other frames, and I assume that's sort of accidental and the source of the funkiness. It's just my gut feeling that if they had been pushed into the stays a little more, the length of the drivetrain would have been a bit "better'. I can't prove or disprove that yet, just a hunch. Kinda.

If anyone knows if there is a connection between here that I'm onto, I'd love to know! I never assumed that rear stay geometry affected gearing much but I really am starting to wonder if it does. It seems a bit more than coincidental that two Snyder frames have this same issue... and I had it with another before.

For reference, this is my bike:

viewtopic.php?f=6&t=32346

***Edit: I have to admit, this was all with 1/2" pitch. With 1" pitch like you have, it could be more complicated. I know that odd tooth count rear cogs exist in 1" pitch, not sure about the front, and I don't even know if this is relevant, because of how 1" pitch chains have two differently sized links. I hope some of this is even remotely useful afterall! :wink:

Edit again, I also didn't see that you had already solved your problem

 

[deorman]

The differences in dropout length and distance from the crank do effect which gears fit best. If you were to change the front by 1, or the rear cog by 1 and the front by 2 or 3, the gearing change will be less than if you just change the rear by 1. If you don't have a pile of sprockets to experiment with though, that could get pretty costly. I'd have to say that if exact gearing was critical to your needs, then a half link or a custom front fender bracket/spacer would probably be the best solution. Just another reason my fenders tend to get shelf-worn, given away, or tossed. :mrgreen:

 

[B607]

then a half link or

Except skip tooths don't have half links. Gary

 

[deorman]

then a half link or

Except skip tooths don't have half links. Gary

DOH!! :lol: