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Discussion Starter #1
I mostly ride my TW off road. It may see a little blacktop around town or to gain access to a trail. I'd really like to re-gear so that 2nd pulls better. Often 1st is slower than I want, but 2nd I'd have to go too fast to develop the power to maintain speed. Same with engine breaking downgrade.
 

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It sounds like you want a 47 to go a bit faster in all the gears, but if you want to go a bit faster yet you want the 45. There is a gear calculator (search the old forum) and you can play with the obvious possibilities}. Some combinations have bad juju so don't get too radical. Tom
 

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Discussion Starter #3
I want to go the other way, making 2nd more useable to me. I don't want to give up first. A lower first won't hurt. I really have no normal use for 5th.
 

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I'd go with a 14/54, or 14/55. I have the 14/55 combo. I use third gear mostly while riding, second in the turns, and first for steep hills (up or down).
 

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Discussion Starter #5
I've found a 55 by JT. Decent sprocket? Anything available bigger than 55?



Anything to the concept of not having two even numbered sprockets (wear)?
 

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Sprockets are available through 70T.



The higher the lowest common multiple of the tooth count and number of links in the chain the more even wear will be spread amongst the various teeth and links. The more spread out the wear, the longer the set lasts. 14/55 to 14/60 would be a good place to start. A 14/79 sprocket set would put 2nd exactly where 1st is with 14/50 sprockets.
 

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Discussion Starter #7
Some recommended vendors/mfg's? I haven't found anything bigger than 55 and that is by JT. I was wondering if someone here had compiled a list of available sprockets and where to purchase.



Also, can chain length required be readily calculated?
 

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Sprockets are available through 70T.



The higher the lowest common multiple of the tooth count and number of links in the chain the more even wear will be spread amongst the various teeth and links.


I've read about this somewhere before, but it didn't make sense to me...care to elaborate?
 

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Discussion Starter #10
I've read about this somewhere before, but it didn't make sense to me...care to elaborate?


It has to do with wear being distributed. If you've had a nick in a chain and it keeps working on the same tooth, the wear will be accelerated. If it contacted every tooth the same number of times the wear would be distributed evenly extending the service life. Qwerty or someone prolly has some math examples.
 

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It has to do with wear being distributed. If you've had a nick in a chain and it keeps working on the same tooth, the wear will be accelerated. If it contacted every tooth the same number of times the wear would be distributed evenly extending the service life. Qwerty or someone prolly has some math examples.
Exactly. Say you run 15/45 sprockets and 135 links. You chip the rear wheel sprocket. That chip will bang the same three links on the chain over and over. Once the links are damaged, those three links will bang the same tooth on the countershaft sprocket every third time it goes around. That damaged tooth will in turn damage every 15th link in the chain, which will damage every 15th tooth on the rear wheel sprocket.



Now suppose you run 15/47 sprockets and 122 links. You damage a tooth on the rear wheel sprocket. Every time the sprocket goes around, it hits a different link. The rear wheelm sprocket rotates 122 times before the same tooth hits the same link again. More than likely, before any one link is damaged enough to damage the countershaft sprocket, every link is just slightly damaged and the damage to the rear wheel sprocket is worn smooth. The process of progressive damage stops.



Determining chain length:

http://www.rbracing-rsr.com/chainlength.html

Pitch for 428 chain is 0.5 inch. Use 22.3 inches for center-to-center of sprockets.
 

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Exactly. Say you run 15/45 sprockets and 135 links. You chip the rear wheel sprocket. That chip will bang the same three links on the chain over and over. Once the links are damaged, those three links will bang the same tooth on the countershaft sprocket every third time it goes around. That damaged tooth will in turn damage every 15th link in the chain, which will damage every 15th tooth on the rear wheel sprocket.



Now suppose you run 15/47 sprockets and 122 links. You damage a tooth on the rear wheel sprocket. Every time the sprocket goes around, it hits a different link. The rear wheelm sprocket rotates 122 times before the same tooth hits the same link again. More than likely, before any one link is damaged enough to damage the countershaft sprocket, every link is just slightly damaged and the damage to the rear wheel sprocket is worn smooth. The process of progressive damage stops.


OK...it makes sense, but is there a formula to figure this out? Say I wanted to change rear sprocket, but wanted to increase (or decrease) chain length to minimize wear..

Does it have to do with neither of the sprockets (or chain) having a common factor? I must be doing something right as my sprockets have worn evenly over the last few years!
 

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Discussion Starter #13
So where can I find something bigger than 55? I'm really leaning toward something in the 60 class.
 

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I have a 60 tooth country sprocket from www.sprocketspecialists.com.

It puts 5th right about where 4th used to be and makes 1st utterly unnecessary for street use.

Absolute top speed that I've seen is about 50.



What I get is the ability to bog along all day at a slow walk, as slow as you can keep the bike upright, doing tree, fence and noxious weed surveys on the ranch.

Needed a longer chain (140 tooth?) and breaker to make the right length for the 60 tooth.



Here's my 46t street sprocket from Sprocket Specialists, on top of the stock 50t, on top of the 60t from Sprocket Specialists:





Gear Comparison 46t-50t-60t by Asiago55, on Flickr



Here's a view of the 60t mounted on the country wheel - yes it does clear the chainguard:





Terracross Left View by Asiago55, on Flickr
 

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Discussion Starter #17
Still nothing bigger than 55 over=the-counter. Sprocket specialists doesn't have pricing on their site. Guess I gotta call. I presume I want steel vs. aluminum? When I go for a sprocket, I'll go o-ring chain. Anything else to consider like the chain guard still fitting?
 

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Discussion Starter #18
Does the chain guard work with the 60t sprocket? I am think changing my dual real sprockets from 45t and a 55t to a 45t and a 60t if it fits.


Ha...I just asked the same. Do you add a length of chain with 2 masters when changing sprockets? I see you're in San Jo.
 

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The chainguard works fine with my 60 tooth - barely clears but has never scraped.



Sprocket Specialists lists 3 stock sizes of imported steel rear sprockets - 44, 50 and 55.

Was quoted 21.99 for the 55 tooth



All other sizes are made to order from aluminum.

Never inquired about their hardening options - I don't ride my TW that many miles.



I paid $60.99 for my 60T and was quoted $66.99 for a 70 tooth.



My 46 tooth city sprocket arrived this week at $67.85 with shipping.

8 days from my phone order to arrival on my doorstep.
 

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Discussion Starter #20
So what's the lifespan of alum vs. steel? I'd think it would be significant. I'm obviously not racing or anything, so even a pound of un-sprung weight is no big deal.



Anyone know of a steel 60?
 
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