coasting 

Does anyone have a picture of their bike in the big ring big cog gear?

I know you're not supposed to use this gear, but i'm just a bit concerned that i cut my chain too short and when in this gear the rear derailleur pulleys are pulled a lot so the bottom pulley is quite a bit forward. i wouldn't mind seeing how much pulley stretch should be on a proper chain length.

Thanks

Matt Gaunt

Give me 5 minutes while I create a picasa album for you.

Yes, I'm unemployed at the moment...

El Diablo Rojo

Rule of thumb is:

Big ring/small cog=derailleur vertical.

coasting 

thanks guys. very useful info diablo. i'll go check it this evening.

AngryScientist 

use any gear combination you want with modern components.

Matt Gaunt

One picasa album: https://picasaweb.google.co.uk/matthe...eat=directlink

Let me know if you have any problems.

coasting 

thanks a lot matt. that was really useful. i think my chain is a a tad short but according to your pics it isn't too far off.

Matt Gaunt

Yeah, I should've included a pic of the chain angle really. It's not pretty! You'll be fine if you follow the chain length advice above and if it's a bit short, as long as you're aware of it you should be ok.

BLACK BIKE

Read this article. It will answer your questions: https://www.sheldonbrown.com/derailer-adjustment.html

DaveSSS 

The big/big plus 1-inch method is not what I use. The little /little method insure the longest possible chain and maximum wrap capacity from any RD. Set the length to the longest that cause the lower pulley to swing down slightly when the ends of the chain are brought together. The chain must not hang loose or rub on the upper chain guide tab.

The only time this would not work is with some setup that exceeds the RD's wrap capacity. Then you have to decide whether you want to avoid the big/big or not use the smallest several cogs, if the chain is 1 inch longer than it should be. 1 inch of chain equal four teeth of wrap capacity.

The big/big can produce ambiguous results. If the ends brought together can't be joined (both inner or outer plates), you have to add 1-1/2 inch or 3 links, not 1-inch.

Wanderer

Dave, I think you are saying the same thing. Sheldon says that if they CAN be connected, add one complete link (really 2, inner and outer) to the chain. Which just happens to equal 1 inch. Your way, adding 3(inners and outers) when they can not be connected, is the same. But, this involves adding a half link.

BLACK BIKE

Are you saying you use the little ring/little cog when determining chain length? How does this work? Wouldn't the chain be to short?

coasting 

This is what I was trying to do. Big big + 2 links (1 inch). On my bike the ends were both inner plates and instead of adding a 3rd link i reduced by 1 link. I had to do this because I didn't realise that I was left with 2 inners until after I had cut it and then had no choice but to cut off another link. The moral of the story is check the ends before cutting.

In the absence of Psimet's tip of the day, I offer this cautionary tale.

Retro Grouch 

I'm from Missouri. You'll have to explain that one to me.



FWIW, I'm a devotee of the big/big school of chain sizing and I don't care how far forward it pulls the derailleur arm. That's how it's designed to work.

urbanknight

It wouldn't be too short because you are doing that method with the chain running through the rear derailleur. I actually hadn't considered it until now, but it would in fact give you the longest possible chain length.

telebianchi

Timely thread --- I've got a mtn bike rear dr on my CX bike (Deore LX). Crankset is a 50/34 compact. I have two sets of wheels: one has a 26 large cog but the other is a mountain bike casseette wtih a 34. I think the small cog is a 11 or 12 on both.

Can I use this measuring technique just using the wheel with the larger cog? Or would there be a need to compromise between the two?

Thanks!

urbanknight

telebianchi, yes you should be able to make the chain for the 34 and it will work fine on the other wheel. I had 3 cassettes for my road bike at one time (12-23, 11-25, and 11-28) and I just set the chain for the 11-28.

DaveSSS 

I thought that since I mentioned the chain causing the lower RD pulley to swing forward that it was obvious the chain is wrapped through the RD as it would normally be. This is a true functional test, with no links added. Pull the end pair of outer plates up to a pair of inner plates and you have a chain that can be joined. If in doubt, leave the chain an inch longer and it will be obvious if it's too long.

DaveSSS 

Although 4 teeth is 2 inches of sprocket circumference, a sprocket that is four teeth larger requires only 1 inch more chain length since the chain only wraps half way around the sprocket. If you use the big/big method with a 12-23 and later want to use a 12-27, the chain will be 1-inch too short. If the little/little method was used, the chain would be 1 inch longer and work with either cassette, or even an 11-21.

As an interesting note, I've used the same 53 inch chain length on my LOOk frames, with a 53/39/28 triple crank, a 53/39 double or 50/34 compact. With this length and a medium cage RD, any Campy road cassette except a 13-29 could be used. That requires 1 inch more chain length (and a long cage RD with the triple).

merckx_rider

You can use any gear combination you like as long as it falls withing the limits of your derailer specs.
When replacing your chain just count the links on the old one and cut the new one the same.

DaveSSS 

You should never have to count links on a chain. Just compare the length. A worn chain may be 1/4 inch longer than a new one, over the full length, but that's easy to see when layed side by side.

Chains must always be an even number of inches long. I use the same 53 inch length on all of my bikes.

DaveSSS 

This is a case where the little/little method should work perfectly. The Deore RD should have enough wrap capacity for the 11-34, so handling a cassette with a 26T large cog is no problem.

coasting 

???

DaveSSS 

A derailleur chain that is not an even number of inches long cannot be joined together. You didn't know that the minimum increment of length change is 1-inch?

My bikes all have the same chainstay length, so the same chain length works with all of them. Double crank, triple crank, compact crank and any cassette except a 13-29 that requires a long cage RD with a 54 inch chain.

urbanknight

Counting links or measuring them side-by-side, either would work fine since 1/4 would not throw you off a whole inch.

Also, I'm guessing Coasting thought you meant even as an integer divisible by 2, not even as in a whole number. Minor misunderstanding (I'm guessing)