It works! We test SRAM Red backwards compatibility
SRAM’s new Red group is a clear step up from the previous Red generation, providing vastly improved front shifting, drastically reduced drivetrain noise, and a further reduction in weight. But can some of those improvements be had without buying the whole group? SRAM says no, but after testing on our own, we disagree.
The company claims that the new group, particularly the front shifting components, is designed as a system and should therefore only be used as such, with all the correct parts in place. We swapped old SRAM and even some Shimano parts into the mix to see how the drivetrain performed without the full complement of new Red components. Here are the results.
The old SRAM rear shifter and the new rear derailleur are 100% compatible and work flawlessly. You miss out on the improved ergonomics of the new shifters, but performance does not suffer. The same goes for using the new rear shifter with an old derailleur: no issues whatsoever.
Using an old SRAM cassette (or a Shimano cassette) with the new derailleur works perfectly as well. The drivetrain is a bit louder than when used with the new Red cassette.
SRAM isn’t lying; the full complement of new Red shift components (shifter, front derailleur, crankset and chainrings) provides the best performance. No huge surprise there, though. Shimano puts forth the same claim, but that doesn’t mean you can’t get very, very good shifting with aftermarket or old parts.
However, there are a number of small changes to the new Red group that make the individual components play a little less nicely with their predecessors. Most obviously, the front shifter no longer has any trim function. The chainrings also use new ramp/pin timing and are spaced slightly differently than they have been in the past. The Yaw front derailleur is designed with these two changes in mind.
Nonetheless, every combination of old and new we tried still worked; not quite as well as the full system, but still better than the old group. Here’s the rundown, along with a little grading scale to give an indication of how much performance is lost. 10/10 is optimal performance using the entire new Red system. Old Red gets a 5/10. All the mix-matches we tried fell somewhere in between the two.
Disclaimer: Setup always varies slightly from frame-to-frame. We tested on a Trek Madone provided by SRAM. Just because we were able to get a certain mix of parts to work isn’t a guarantee that you will be able to — and vice versa.
New shifters + new front derailleur + old SRAM SRM crank + old SRAM Force chainrings: 8/10
As expected, the new crankset and rings are responsible for a significant share of the shifting improvement over the old group. The different spacing of the old rings made front derailleur alignment during setup quite tricky, though. You’ll need to be a decent mechanic or have a lot of patience to get the group rolling with minimal chain rub, and even so, the small/small combo will likely be noisy. (But who rides in the 39/11? Certainly not our well-informed readers.)
Tech tip: Derailleur alignment is absolutely critical with the Yaw front derailleur, even more when not using the new Red crankset. Align the Yaw front derailleur’s setup lines with the big ring, as SRAM suggests, then twist the tail out just a hair before clamping the derailleur down.
Old shifters + new front derailleur + new crankset: 10/10
Performance appears flawless, but you get an extra trim stop out of the front shifter that is not needed thanks to the design of the front derailleur. Depending on which generation of SRAM shifter you have, that extra stop may be for the big or small chainring. Older shifters, which have the trim stop for the smaller chainring, actually work better with the new front derailleur, because the chain rub is most prevalent in the small/small gear combo.
Old shifters + new front derailleur + old crank: 9/10
Throwing on the new Yaw front derailleur offers up the same performance increase as the first setup, except you also get the superfluous trim stop provided by the old front shifter.
If you want the new front derailleur and the new shifters, you need the new crank as well unless you don’t mind chain rub.
New shifters + old front derailleur + new crankset: 6/10
The old derailleur still shifts poorly, no surprise there. But the new chainrings do help a bit. Again, we could not eliminate chain rub in the small/small combo, but that doesn’t matter much.
Old shifters + old front derailleur + new crankset: 8/10
We still experienced a bit of chain rub, and we couldn’t shift under power as you can with the new FD and crankset. But the shifting is still better than with old Red.
New shifters + Shimano Dura-Ace front derailleur + new crankset: 8/10
Good, except for the chain rub issue in the small/small gear combo. (Noticing a theme?)
Old shifters + Shimano Dura-Ace front derailleur + new crankset: 9/10
With its stiffer steel cage, Shimano’s 7900 front derailleur is vastly superior to the old Red front derailleur, so it is no surprise that it mates well with the new, stiffer chainrings of the new Red crankset. The new crank is very light, so this single upgrade is a good option for the weight weenies out there.
Tech tip: The neat little chain catcher that comes with the new Red front derailleur also works on braze-on Shimano and old SRAM front derailleurs.
The improvements in front shifting come from a combination of the new Yaw front derailleur and drastically improved chainrings, which have been made significantly stiffer and include improved ramp and pin timing. Why not, therefore, just put the new rings on an old crankset and save some cash?
Turns out that is not such a good idea. The new rings may still be five-arm with a 130BCD (bolt circle diameter), just like other standard road rings, but SRAM now uses a hidden bolt behind the crankarm rather than five independent spider arms. That means that the new Red rings have to be rotated 180% in order to mount up to a regular crankset. The pin that normally sits behind the crankarm to prevent chain jam sits either to the left or right of the crankarm, making it useless.
Further, the inner ring doesn’t fit on a regular crankset at all unless you’re willing to file it down a bit. The tab that is intended to sit behind the crankarm on the new Red crank is a bit too long to attach to a five-arm spider on a regular crankset. Running an old little ring seems to mess up the spacing sufficiently to negate the advantage brought by using the new big ring.
Whether the improvement in shift quality that comes from the new rings is worth the risk of jamming the chain in between the rings and crankarm, and spending time filing the little ring, is up to you.
The takeaways from this testing are rather simple. With both the new front derailleur and new crankset, no trim is needed so you can use any generation of shifters. If you want the new shifters, though, you must buy both the crankset and the front derailleur unless you don’t mind chain rub.
If you don’t mind chain rub (in gears you shouldn’t be riding in anyway), you can mix and match just about anything, with varying degrees of performance. But as long as the front derailleur is aligned correctly, any make and model of crankset should function just fine.
If we had a bike with old SRAM Red, our first upgrade step would be to pick up the new front derailleur. With our old shifters and old crankset, the new front derailleur would improve shifting considerably with minimal mechanical headache.
Next up would be the crankset, which drops quite a bit of weight. With the new FD and new crankset, front shifting performance is as good as it is going to get from SRAM. We’ll have an extra trim stop in our left shifter, but that doesn’t matter.
Following the front shifting upgrades, the decision is between the new cassette and the new brakes. The cassette is even lighter than before and completely quiet, but the new brakes are designed around, and work much better with, the new wide rims we love. So, since we ride wide (25mm+) rims often, we’d go with the brakes first. If your rims are narrow, go with the cassette.
After that we would buy the new shifters for their improved ergonomics and shift feel. Then, finally, we’d pick up the new rear derailleur.
Questions? Requests? Email Caley at firstname.lastname@example.org or Tweet him @CaleyFretz.