It's not bad if you aren't paying to replace your cassette/chain combo. I cross-chain often in races, but my team covers the costs of expendibles like chains and cassettes. When out riding my own bike, I avoid cross-chaining as it accelerates wear and tear on the chain and cassette.

 

In a word, yes. Like the above poster siad, it will accelerate wear. If you occasionally do it for short distances, it's no big deal, but try not to do it on a regular basis.

 

Depends entirely on your priorities. As said, cross-chaining is better than a front shift in many racing situations, especially if the front shift would force a rear double shift. Cross-chaining also doesn't matter if you throw out your chain and cassette long before they're worn, as many people do. There's some loss of efficiency when the chain runs at a zig-zag. But with modern chains, it's much less than it used to be and doesn't matter unless you're racing.

For what it's worth: I used to ride big-big all the time to keep from shifting my front compact, but stopped doing it when I put my 52-42 back on.

 

Test it on the bench, make sure your chain is long enough.

It will happen in most situations, no probs. Not terribly sensible to ride it around all day though.

 

I am not certai, but big/big is better than small/small, it seems to me, because of the risk that the big chainring teeth will catch the side of the chain as it enters the small chainring. This depends on frame geometry, trim, and gearing, I suspect.

 

my big ring is a 53 and my largest cog is a 25. i use this combination when i'm on flats and hit climbs which aren't incredibly steep or long.

Results in a nominal increase in wear. Not really a big deal with the flexibility inherent in today's chains, but still something to be avoided.

If nothing else, it's a few percent less efficient than the equivalent gear that has a better chain line. And it's not like we're in the dark ages of down-tube friction shifting, when double-ended shifts required some thought and talent.

As a previous poster mentioned, it's a less heinous crime than small-small, though not particularly for the reason of big ring rub. While that can be a concern with compact cranksets, the larger concern is the higher chain tension, which when combined with the poor chainline will (relatively speaking) increase wear.

 

I'll admit I cross-chain in that combo (53-25) whenever I need a low gear. I absolutely hate shifting up front. It's loud and scary. I don't stay in it very long though, just enough to get me up the hill or whatever.

 

Go to sheldonbrown.com and look up gear ratios. You can input your cassette and chainset and see what you're doing. Why not the small chainring and a slightly smaller cog? Less wear on the cassette/chain and you can run the same (or almost exact same) ratio.

 

I'll admit I cross-chain in that combo (53-25) whenever I need a low gear. I absolutely hate shifting up front. It's loud and scary. I don't stay in it very long though, just enough to get me up the hill or whatever.

loud and scary? you're kidding, right?

 

Not quite

Go to sheldonbrown.com and look up gear ratios. You can input your cassette and chainset and see what you're doing. Why not the small chainring and a slightly smaller cog? Less wear on the cassette/chain and you can run the same (or almost exact same) ratio.

Added drivetrain wear by briefly using the large-large combination is minimal. Added drivetrain wear by consistently using the small chainring and smaller cogs is significant. If you're only using that gear ratio for brief "roller" climbs, then it makes no real difference.

 

My cassette is an Ultegra 12 - 25. Which gears should I avoid then when I'm on my big chainring to prolong the life of my hardware?

 

When on the big chainring, avoid the 2 or 3 largest cogs; when on the small chainring, avoid the 2 or 3 smallest cogs (talking about 10-speed cassettes here).

 

Not quite, again

When on the big chainring, avoid the 2 or 3 largest cogs; when on the small chainring, avoid the 2 or 3 smallest cogs (talking about 10-speed cassettes here).

From a chain and drivetrain wear stanpoint, you really only need to avoid the largest cog when in the big chainring, and it really is a minor issue. When on the small chainring, using the smallest cog will almost always result in the chain rubbing against the inside of the large chainring, and that can cause damage rather quickly. The main reason to avoid "small-small" combinations is that the chain is engaging far fewer teeth on both the cassette and the chainring, and this means a lot more "stress per tooth" and so causes faster wear.

 

shifting a front der

I'll admit I cross-chain in that combo (53-25) whenever I need a low gear. I absolutely hate shifting up front. It's loud and scary. I don't stay in it very long though, just enough to get me up the hill or whatever.

I understand. I have an older Trek and it has a front 52 42. The front der shifts like a rear der, it just snaps into place. You wouldn't have a problem shifting one of those, plus you would be stronger because you wouldn't have any low gears. I think that a lot of people don't realize that these big gear changes like in a Compact just require more precice shifting and are a little harder to shift than close gear range cranksets. That's what you get trying to get something (lots of gears coverage) for nothing (2 front gears only). I have 4 bikes, one of which has a double. I used to have 2 doubles. I could go "almost" anywhere I could go with the triple, not quite but almost.

 

I don't quite understand why the OP is running a low gear on the flats......If I happen to find a level piece of road I usually end up in my highest gear (52/12) ..

 

I guess this is a moot point for me now, my new Sram Red, (Compact, with 11/26) will no longer go Big ring, Big cog. 2000 miles on the bike/drivetrain and the chain is well within limits, I had been using this combo for short rollers. The head wrench at my lbs says "never use the big/big combo, or small/small for that matter."
Any suggestions for getting my big ring, big cog combo back? New chain? (currently using a D/A).

 

Never say never.

The head wrench at my lbs says "never use the big/big combo, or small/small for that matter.

I guess head wrench never raced, or listened to stories about racing. Sometimes you get caught napping in the wrong ring, and big-big or small-small is the proper choice until you're all sorted out again.