Countless reviewers have compared the components from Campagnolo, SRAM and Shimano but there’s a key feature that often gets overlooked – What happens when you ask for one last easier gear but your bike has no more cogs to offer? We’ve all been there, struggling up a steep climb on our last legs. We reach down and try to initiate a shift of the rear derailleur but we’re already in our largest cog. What happens next is very different depending on whether you’re using Campagnolo, SRAM, or Shimano. The gold standard for this situation was set by good old-fashioned downtube shifters. Downtube shifters indicate where you are on the cog by their position. With some experience you can tell at a glance. You can reach down and brush the shifters with your hand to feel whether that right-hand lever is horizontal. If you try to move it it will firmly resist. When you run out of ammunition it fixes bayonets. Among contemporary gruppos, Shimano’s mechanical offerings fare the best in this test. Although they offer no visual cues, if you try to shift beyond the biggest cog the lever won’t move. It provides immediate feedback and allows you to pretend that you were just resting your fingers there, not really trying to shift. It says, “I’ve done all I can, now it’s up to you.” When you run out of ammunition it whispers, “Use me as a club”. Campagnolo’s mechanical gruppos aren’t terrible, but they don’t give up as resolutely as Shimano’s. The upshift lever will swing freely but no cables or ratchets will be engaged. It’s harder to play this off as an accident but it’s also pretty silent and inconspicuous. When you run out of ammo it clicks when you pull the trigger. Shimano’s electronic Di2 gruppos work pretty similarly to Campagnolo’s mechanical ones when you run out of gears. You can still push the little button but the derailleur doesn’t do anything. I don’t know much about how electronic Campy and SRAM perform. Worst of the lot on this test is SRAM. I love SRAM and I use their fine products at all price levels on many of my bikes, but they’re just the WORST when you accidentally try to shift beyond your biggest cog. The doubletap ratchets rattle and grind, you can feel your expensive parts being worn down, and if you’re unlucky it just might dump you DOWN one cog, making matters worse. There’s no faking it when you make this mistake. Every rider around you knows that you’re out of gears and looking for more. When you run out of ammunition it fires a damp squib, burns your trigger hand, and leaves you wondering if your gun is jammed. Surrender is your only recourse. Tweet