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Chain Rings and Chain Length

MartynG

Well Known and Active Website User
VOC Member
I am considering fitting two different rear chain rings to my Comet (one each side) so that I will have a slightly lower overall gearing for city and mountain work, and a tad taller gearing available, by rotating the rear wheel, for longer distance cross country runs.

What I have in mind is a 50 tooth on one side of the rear wheel and a 46 on the other. Big question is will I be able to utilise both/either chain ring without needing to adjust the chain length? Does anyone have experience in this area?

If the answer is that for my proposed 4 link difference I would need to adjust the chain size (by insertion/removal of links) then what would be the maximum chain range I could use without the need to add or remove links??

Collective wisdom appreciated,

Martyn
Australia
 

davidd

Well Known and Active Website User
VOC Member
Martyn,

My racer may be too different regarding its setup as I run a 21T CS and I am using the short RFM, but I would think the relative differences would prove useful. I cannot safely change two teeth without changing the chain. Thus, I run a 106 link chain for the 46T, a 108 link for the 48T and 110 link for the 50T. Almost all the tracks I race can be done with the 50T and 52T except Miller in Utah where a 54T would be best. I am also red lining at 7000 RPM and you are probably sticking to 6000.

I can give you the speeds in each gear for each sprocket at various RPM, but if you are interested, you might as well input your own data and know for certain. It is an Excel spread sheet that has the calculations embeded in the cells. If you (or anyone else) wants a copy, write me at daviddunfey@hotmail.com.

I have the feeling that it is too much of a spread and that you will not be able to utilise the power well in 4th with the 46T on the street. If you are always starting and ending at home for the change, just use two chains. If you expect to change mid-trip I think you will have to tighten the spread.

David
 

chankly bore

Well Known and Active Website User
Non-VOC Member
You won't pull a 46 tooth sprocket with a standard motor, unless you like dropping to third gear every time you get a headwind or an upward slope. Some owners like 50 tooth for all-round use. You may use extra links with possible minor twiddling of the adjusters provided both extra links and chain are in similar condition.
 

Bill Thomas

Well Known and Active Website User
VOC Member
Hello Martyn, Don't worry about useing an extra link or 1 1/2 links with two split links, I did it for many years racing, Cheers Bill.
 

Colin

Well Known and Active Website User
VOC Member
Hi Martyn
My first ever Comet 40 odd years ago,, (when I knew nothing about them) came with a 46 tooth rear sprocket, and would never go very well. Too high geared.
My current, and long time owned Egli Comet Special runs a 49 tooth rear for everything. Seems to be a pretty good compromise.
Also whilst competing in various trials with the Arbuthnot Iron, I ran a 50tooth rear sprocket, and a chain made up of two bits and with a cranked link. (Necessity at the time!) I worried about it all the time on a trial but it never gave me a problem. However I don't recommend it.
 

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