DA 7900 & chainline

[jpw]

I was wondering, with DA 7900 10 speed what would be the highest cog up the cassette to realistically pedal in whilst still remaining in the outer ring?

...and for the inner ring the lowest cog down the cassette?

Thanks, Jason.

[dekindy]

Recent articles that I have read indicate that with today's modern drivetrains you don't have to worry about wear from crosschaining.

On my Ultegra triple it makes noise when I am cross chained so I avoid cross chaining for that reason. In the middle ring I avoid the two innermost cogs and the two outermost cogs and in the large ring I avoid the two innermost cogs. I don't use the inner ring unless I need the two lowest gears.

To answer your question, technically it does not matter.

[Dave]

I don't agree about crosschaining not accelerating wear. With a double crank, I would never use the big/big or the small/small, except by accident or just for a few seconds. With a compact crank I do catch myself in the little/little combo occasionally, but I shift up to the big ring as soon as I notice that I've failed to shift to the big ring.

The only change with modern drivetrains 10 and 11 speed drivetrains is thinner cogs and thinner chains that both wear more rapidly due to the reduced surface area bearing the loads.

With regard to a triple crank, the middle ring is nearly as far to the right as the big ring on a double, so I treat it as such. Only use the middle/big briefly - otherwise shift to the little ring. Don't use any of the smallest 2-3 cogs with the little ring.

[Z3c]

The answer to this question is very dependent upon chainstay length; much more than componentry. Without that info, anyone will be quessing or providing an answer based upon their bike which may have no application to your bike.

Scott
I was wondering, with DA 7900 10 speed what would be the highest cog up the cassette to realistically pedal in whilst still remaining in the outer ring?

...and for the inner ring the lowest cog down the cassette?

Thanks, Jason.

[jpw]

The answer to this question is very dependent upon chainstay length; much more than componentry. Without that info, anyone will be quessing or providing an answer based upon their bike which may have no application to your bike.

Scott

42.5 cm.

[dave thompson]

Based on my experience with the 6700 gear, with 42.5 chainstays and a long enough chain, you should be able to run the big/big and small/small combos with no immediate issues. Chain wear will of course be accelerated when used in extremes like that.

[Pete Serotta]

The only change with modern drivetrains 10 and 11 speed drivetrains is thinner cogs and thinner chains that both wear more rapidly due to the reduced surface area bearing the loads.

.


Lightness and more gears have a price... Also those "ti" cogs wear faster and cost more than the steel. Ultegra and Chorus cog sets are cheaper than their big brothers Dura Ace and Super Record and will give you more miles with a minor weight penalty. WIth me on the bike the bike has a major weight penaly!!! :no:

[oldguy00]

I've cross chained for years with 7800 cassette/chains on Cannondales, big ring up front big cog on back. I'm just too lazy to shift out of the big ring a lot of the time. I've never had an issue with excessive wear. If you get noticeable wear from it, then IMHO your cassette was probably through most of its life regardless of what gears you used...

If you are desperate to squeak every extra mile of use out of your gear.....well...then don't cross chain....

[Peter P.]

Chainline, as a number, is irrelevant to your question. You should be able to use any gear on the cassette while in the large ring. Yeah; it may accelerate wear but so what-if you want the parts to last a long time then don't ride your bike. Otherwise, use all the gears and enjoy it.

[false_Aest]

Chainline, as a number, is irrelevant to your question. You should be able to use any gear on the cassette while in the large ring. Yeah; it may accelerate wear but so what-if you want the parts to last a long time then don't ride your bike. Otherwise, use all the gears and enjoy it.

WORD OF THE LORD!

Also, your bike is a bike.

If you treat it better than your significant other, stop.

If your bike is your significant other, time to start abusing it.

[RPS]

What is possible and what is advisable are two different things. Personally I prefer to limit crossing the chain on doubles by leaving one unused cog at either end; and with triples two unused cogs, particularly on the small cog side. Normally I don’t even get close to that because I like using the straightest chainline that gives me the gear I want.

Regarding your specific question, I expect equipment manufacturers anticipate riders will occasionally cross the chain fully in both directions due to the fact that their equipment specifications are based on that occurring. It is no coincidence that Shimano rear derailleur “maximum” capacity was listed at 29-teeth when it was based on a 53-39 and 12-27 combination. And the same goes for the new 7900 group, the new rear derailleur capacity of 33 teeth is based on combining a 50-34 with an 11-28. I think that if they wanted to make a big deal of excluding crossing the chain (to cover their @$$) they’d at least “rate” the equipment differently even if designed to handle it.

FWIW: I’m normally easy on equipment, but the last major mechanical I recall having (about 6 or 7 years ago) was when a friend bet me I couldn’t climb a steep section of road in my big ring. Having done that same section a couple of days earlier in a 42/21, I figured I’d have no problem in a 53/27 so I accepted the challenge even though it meant crossing the chain. Anyway, I probably didn’t go 100 yards up the first climb before wrapping the rear derailleur around and bending the dropout. Maybe it was pure coincidence, or it was due to the RD being old, and having it at near-maximum capacity certainly didn’t help, but one thing I took from this bad experience is that crossing the chain fully probably puts additional stresses on components. And if you don’t have to, then why do it (unless you are in a race and a split second to shift will make a difference)? :rolleyes: