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by Matt Wikstrom
December 29, 2017
Photography by Matt Wikstrom
TECH NEWS BROUGHT TO YOU BY BIKEEXCHANGE
With three major groupset manufacturers, a range of transmissions (seven- to 11-speed), and an excess of aftermarket components on the market, it is inevitable that consumers will have to grapple with a variety of incompatibilities when replacing or upgrading worn parts. That’s because there is generally very little interchangeability between groupset components, but there are some exceptions.
In this post — an updated version of an article that we first published in 2014 — Australian tech editor Matt Wikstrom takes a look at the known incompatibilities for 10- and 11-speed road groupsets and highlights those instances where it is possible to mix parts from different brands.
There was a time when cyclists were free to mix and match transmission components, but that all changed when Shimano introduced indexed gear shifting in 1984. The new system provided very accurate shifting, but it depended upon precise compatibility of the shifter with the derailleurs and drivetrain.
Indexed shifting works because the rear derailleur travels a precise distance in response to a pre-set amount of cable pull within the shift lever. Cable tension is critical for accuracy, but the geometry of the derailleur and the sprocket spacing must match the indexed cable pull, otherwise the derailleur will not align with each sprocket.
Rather than work to a common standard, Shimano, Campagnolo, and SRAM have all developed their own specifications for their indexed gear systems. SRAM mechanical gear levers employ 1:1 actuation (1mm of cable pull moves the rear derailleur 1mm) while Shimano and Campagnolo use higher ratios (1.4 to 1.9:1). Thus, while it is physically possible to operate one brand of derailleurs with another brand of shifters, the quality of shifting will be greatly compromised.
The evolution of the transmission from six-speed to 11-speed created further incompatibilities. The introduction of eight-speed systems depended on an increase in rear hub width from 126mm to 130mm to accommodate the extra sprocket. After that, the width and spacing of the sprockets was reduced to allow more sprockets to be added. Chains were narrowed, too, slimming down to 5.50-5.90mm where once they were 7.80mm.
An increase in the number of rear sprockets over the last couple of decades has added to the incompatibility of groupset components.
As a result, there is not much forwards or backwards compatibility, even within the same brand. Such restrictions aren’t limited to shifters and derailleurs, either; they can also affect the rest of the drivetrain as well as the brakes. This makes for an amount of enforced redundancy, much to the displeasure of at least some buyers. However, the major manufacturers maintain that it is a necessary byproduct of their ongoing R&D efforts.
As a general concept, then, there is very little interchangeability amongst groupset components, which is something any shopper should keep in mind when selecting the parts for a custom road bike build. This is especially true when comparing one manufacturer with another, but it can also also apply to different levels of components from the one brand. Nevertheless, it is possible to mix some parts, so here’s a look at what will and won’t work for 10- and 11-speed road groupsets.
At face value, the distinction between compatible and incompatible parts should be an easy one to make, however there are a range of views. The major manufacturers are very unforgiving of any deterioration in performance but not all riders are so discerning. Some may not notice lazy rear derailleur shifting, extra chain noise, or a reduction in braking power.
For the purposes of this article, I recognise three levels of compatibility: go, no-go, and variable. Any combination that is a “go” will consistently deliver a high level of performance, in keeping with the view of the manufacturers, while “no-go” will signify an incompatibility where there is an obvious shortcoming in the operation and/or performance of the system.
Every other combination that falls in between these two extremes will be considered “variable”. In general, the performance of these combinations may be satisfactory but it is not guaranteed, or there is a risk of an incompatibility, depending on the specific components involved. Ultimately, the combinations that fall into this category should be considered unproven and subject to the needs and expectations of the individual.
When it comes to chains and cassettes, the market is awash with products from the major manufacturers and aftermarket brands, yet it’s not always obvious which chains and cassettes are compatible with one another and any given groupset.
When SRAM entered the road groupset market in 2006, it decided to adopt Shimano’s specifications for its chains and cassettes. As a result, the chains and cassettes from the two brands have always been completely interchangeable for any given type of transmission (e.g. 11-speed). Buyers are free to use a SRAM chain and cassette with their Shimano groupset, and vice versa, just as a SRAM chain can be paired with a Shimano cassette, and vice versa.
SRAM’s cassettes and chains are compatible with all of Shimano’s groupsets, and vice versa.
Likewise, Shimano and SRAM buyers have the freedom to mix different levels of chains and cassettes so long as they are designed for the same kind of transmission. Thus, an Ultegra (6800/8000) 11-speed chain can be used with a Dura-Ace (9000/9100) 11-speed cassette. Similarly, there is no need to match the level of the chain and cassette to the rest of the groupset, so a 105 (5800) 11-speed cassette can be used with a Dura-Ace (9000/9100) 11-speed groupset.
That doesn’t mean that the mix will always please a rider. Shimano’s chains and cassettes are typically smoother and quieter than SRAM’s offerings, and durability can differ between the two brands as well as the different levels of components. While these differences may frustrate some buyers, it makes for a wider range of products to choose from, which is likely to suit thrifty shoppers and riders that enjoy experimenting with their equipment.
Campagnolo has always adhered to its own distinct specifications for its chains and cassettes, including a unique spline pattern for the cassette. The latter explains why a Shimano or SRAM cassette cannot be fitted to a wheel with a Campagnolo freehub body (and vice versa, save for Edco’s unique freehub body design, which will accommodate both). In addition, Campagnolo’s chains differ from Shimano/SRAM in overall width, and the company uses variable spacing for its sprockets (Shimano/SRAM cassettes have uniform spacing).
It is the difference in the latter that will produce a noticeable difference in shift quality for 10-speed transmissions, which is why a wheel fitted with a Campagnolo cassette performs poorly (lazy upshifts, extra chain noise) with a bike running a Shimano or SRAM groupset, and vice versa. With that said, the incompatibility is not so profound as to render the gears useless, so the mismatch is more than acceptable as an emergency replacement and short-term use.
The overall width of a chain has decreased as the number of sprockets on the rear wheel has increased. As a result, 11-speed chains are narrower than 10-speed chains, and the two are mostly incompatible with one another.
Those differences are far less noticeable for 11-speed groupsets. Indeed, it is now possible to mix and match 11-speed chains and cassettes from all three manufacturers with satisfactory results in most instances. Fussy riders and mechanics may notice a difference in the shift quality and/or some extra noise, however both are relatively subtle.
In contrast, attempting to mix 10- and 11-speed chains and cassettes from any brand is likely to cause more noticeable problems. Ten-speed chains are significantly wider than 11-speed chains, which, when coupled with narrower sprocket spacing for 11-speeed cassettes, will result in more noise, regardless of the brands involved. In the alternative scenario, an 11-speed chain is less likely to cause problems with a 10-speed cassette; indeed, some anecdotal reports actually suggest a reduction in noise.
Finally, for those that are interested in experimenting with chains from aftermarket brands such as KMC or Wippermann (Connex), they will suit all groupsets so long as they are matched to the transmission. Once again, the results of any specific combination may not satisfy all riders, depending on how sensitive they are to chain noise and the quality of shifting.
When SRAM introduced its 1×11 drivetrain for MTB in 2012, it was accompanied by XD, a new freehub body and cassette design. XD was developed so that the company could offer a 10T sprocket with its new cassettes to increase the range of gear ratios for the 1×11 transmission. Up until that point, a 10T sprocket was simply too small to fit to a standard freehub body.
The SRAM XD freehub body (or driver) is a stubby structure that is distinct from Shimano’s and Campagnolo’s freehub designs. Thus, it is not compatible with any cassettes from either of those companies, or SRAM’s conventional road cassettes. SRAM’s XD freehub body is only compatible with its XD cassettes, however owners are free to use any 11-speed chain with the cassette.
More recently, SRAM unveiled a new road-specific version of XD called XDR. The XDR driver is 1.8mm wider than XD (so as to suit the spacing of road hubs) but it remains compatible with XD cassettes provided a suitable spacer (1.8mm) is fitted. At this stage, SRAM has yet to release an XDR cassette but it seems likely that it will serve a 1×12 transmission specifically designed for road use.
While the demands for the chain and cassette are fairly stringent, chainrings (and cranksets) are far more forgiving, so it is possible to mix brands as well as 10- and 11-speed versions without having an impact on the quality of shifting.
Thus, cranks from Shimano, SRAM, and Campagnolo are freely interchangeable along with those from all aftermarket brands (e.g. FSA, Rotor, Praxis, etc.). And while it is preferable to match the chainrings/crankset to the transmission, there is no strict need to do so.
Thus, owners of 10-speed cranksets fitted with a power meter do not need to replace the chainrings if they upgrade to an 11-speed transmission. Similarly, an 11-speed crankset will readily mesh with a 10-speed transmission. This is not something crank manufacturers recommend, though, with some pointing to a difference in the spacing of the chainrings as a potential problem, however the weight of anecdotal evidence clearly suggests otherwise.
Mixing and matching cranksets and bottom brackets is a completely different matter that depends upon the specifications for the frame and the crank axle. See our article Bottom brackets, crank axles and bearings: Your guide to a compatible fit for more information on this topic.
As the brains behind the operation, each brand’s shifters (mechanical and electronic) must be matched with its own derailleurs in order for the indexed system to function properly. In many instances, it is possible to mix different levels of shifters and derailleurs from the same brand (e.g. Dura-Ace/Ultegra/105; Red/Force/Rival; Super Record/Record/Chorus), however it’s not safe to assume that this will always be the case. Shimano, SRAM, and Campagnolo have all prepared compatibility charts to help consumers identify potential problems, but none address all of the possible permutations or include components that have been discontinued.
As noted above, there is little or no backwards or forwards compatibility for Shimano, Campagnolo, or SRAM, so earlier versions of any given shifter may not be compatible with current derailleurs (and vice versa). For example, Shimano’s mechanical Dura-Ace 7900 shifters are not compatible with a Dura-Ace 9000 derailleurs because 7900 was a 10-speed groupset and 9000 is 11-speed. In contrast, Dura-Ace 9000 and 9100 shifters and derailleurs are interchangeable.
For those contemplating a piecemeal upgrade from 10-to 11-speed, there may be no need to replace the derailleurs, at least for SRAM mechanical groupsets. Owners need only replace the shifters and fit an 11-speed chain and cassette, and the hybrid system will perform much like a complete 11-speed groupset.
In contrast, Shimano and Campagnolo owners will need to replace both derailleurs and the shifters. At face value, it may be tempting to ignore the front derailleur; however, the latest mechanical shifters from each brand have a new pull-ratio to suit long-arm front derailleurs that won’t suit earlier short-arm versions.
At this stage in the development of electronic groupsets, there are far fewer options available, but already there are marked differences in compatibility between the major manufacturers. Shimano’s Dura-Ace and Ultegra Di2 components are highly interchangeable provided they all bear the company’s e-tube technology (the one exception being the original Dura-Ace 7970 groupset, which uses a unique wiring harness). In contrast, Campagnolo’s Chorus EPS parts are completely incompatible with the company’s Record/Super Record EPS components, including the wires, batteries, and chargers.
There is a limit to the size of the sprockets that can be used with any given rear derailleur. It’s a physical constraint based on the geometry of the derailleur and the amount of clearance between the upper jockey wheel and the sprockets. When that clearance is defeated, the jockey wheel will run into one or more of the largest sprockets.
According to manufacturer recommendations, the maximum sprocket size for short-cage rear derailleurs is typically 28T (Shimano/SRAM) or 29T (Campagnolo), while mid-cage derailleurs can accommodate sprockets up to 32T.
As with all manufacturer recommendations, these limits are conservative, and it is possible to use larger sprockets (e.g. 30T for a short-cage derailleur) after adjusting the so-called “B screw”, but it does depend on the design of the derailleur hanger. Bikes with relatively long hangers may be able to accommodate even larger sprockets (sometimes, up to 32T for a short-cage derailleur) but there is no way to tell without experimenting with different-sized sprockets. For those hoping to use an even larger sprocket, Wolf Tooth’s Road Link can increase the clearance of a mid-cage derailleur to accommodate sprockets as as large as 40T.
There is more to fitting a larger rear sprocket to a road bike than simply clearing the upper jockey wheel, though. The chain must also be long enough to accommodate the extra teeth without hanging slack on the bike when the smaller sprockets are used with the small chainring. This is where the length of the rear derailleur cage becomes important, because a longer cage can take up this slack, thereby increasing the overall “capacity” of the derailleur.
The rear derailleur must be matched to the size of the largest rear sprocket.
This capacity, which is expressed in terms of teeth, accounts for both the difference in size between both chainrings (e.g. 14T for a 53/39T crankset) and the largest and smallest sprockets on the bike (e.g. 17T for an 11-28T cassette). Ideally, that sum total should be equal to, or less than, the manufacturer’s stated rear derailleur capacity.
According to manufacturer recommendations, the capacity of a short-cage rear derailleur is 33-34T, and this increases to 37T for mid-cage versions. Once again, these are conservative numbers that can be exceeded in some instances, but it should be obvious that bikes fitted with a standard crankset (53/39T) are more likely to accommodate a bigger difference in rear sprocket sizes than one fitted with a compact crankset (50/34T).
Be that as it may, it is possible to ignore this capacity and use a larger sprocket without changing the length of the chain so long as the rider is prepared to avoid cross-chaining when using the big chainring (albeit with potentially dire consequences if you forget). Alternatively, the chain can be lengthened, but then the rider will have to avoid cross-chaining when using the small chainring, otherwise the extra slack may cause the chain to derail from the chainring.
When Shimano and SRAM introduced its 11-speed groupsets a few years a go, buyers had to replace their freehub bodies or wheels in order to enjoy the extra sprocket. That’s because the 11-speed cassettes were wider. In contrast, there was no such need for Campagnolo’s 11-speed cassettes since there was no change in the overall width.
Now all current wheels, hubs, and bikes fitted with Shimano/SRAM are 11-speed-ready, but for those riders than have yet to upgrade from nine- or 10-speed groupsets, it remains an important consideration if their wheels hark from the same era.
For those that own Mavic wheels, there won’t be any need to replace the wheels since the company’s 10-speed Shimano/SRAM freehub bodies were always longer than they needed to be at the time, and thus happened to be 11-speed-ready. As for other brands of wheels or hubs, it is often possible to buy a conversion kit to address the incompatibility. Failing that, it may be possible to machine the existing freehub body and/or the cassette (an extra 1.8mm is all that’s required); otherwise, the Shimano/SRAM freehub body can be replaced with a Campagnolo version (if available), remembering that Campagnolo’s 11-speed cassettes will perform well with Shimano’s and SRAM’s 11-speed transmissions.
The width of Shimano/SRAM-compatible freehub bodies increased with the introduction of 11-speed groupsets, and are typically marked as such, so that they can be discriminated from 10-speed-only versions, which are unmarked. A 10-speed Shimano or SRAM cassette can still be fitted to an 11-speed body, but a spacer will be required to make up for the difference in width.
There is another, more subtle, incompatibility that affects different brands of hubs and wheels, but it will only have an impact on those riders using multiple wheelsets. The issue arises from subtle differences in the spacing of the rear hub and freehub body, which can vary the position of the sprockets relative to the rear derailleur. As a consequence, the rear derailleur limit screws and cable tension may have to be reset when swapping wheels. This will not only ensure crisp shifting across the full cassette range, but may also prevent damage from a chain that derails into the spokes or frame.
In some instances, shims can be added to the rear axle to achieve perfect interchangeability, however there are many brands of hubs where this is not possible. Aside from machining new fittings for the hubs, there’s no easy way to address this issue, but sticking to the same brand of hubs/wheels wheels will often do a lot to avoid this situation.
Variation in hub spacing has a more profound effect on disc brakes, where even very minor differences (<0.5mm) in the position of the rotor can ruin its alignment with the calliper. Once again, shims can be used to normalise the alignment of the rotors for multiple wheelsets, but this is only possible for 6-bolt rotors, so those using centre lock hubs may have to consider a switch to a 6-bolt adapter.
For many years, road brake levers from each of the major manufacturers offered cable pull ratios that were sufficiently similar that it was possible to pair any brand of rim callipers with any brand of brake levers with good success. More recently, though, Shimano increased the cable pull of its brake levers and re-designed its rim callipers to suit. As a result, Shimano’s newest brake/shifter levers aren’t well suited to SRAM or Campagnolo brake callipers, and vice versa, or even earlier versions of its own dual-pivot callipers (e.g. mixing Dura-Ace 7900 levers with 7800 callipers results in less braking power), but none are strictly incompatible.
As for aftermarket brakes, there is very little information that is readily available on their performance with different levers; generally, they’re designed with some sort of compromise so as to accommodate all levers with varying degrees of performance. At present, it appears Campagnolo and SRAM road brake levers enjoy greater compatibility with at least one brand than Shimano’s latest design (eg. eebrakes), however some variability in performance should be expected.
It is worth noting that there are different fittings for rim callipers on road bikes that dictate what kind of brake can be used. A single centre-bolt is the most common, and up until the dawn of aero road bikes, it was the only fitting. Shimano’s two-bolt direct-mount system has become a common sight on aero road bikes, but there is another two-bolt direct mount system developed by TRP that pre-dates Shimano’s design, that can be found on some TT bikes (eg. Specialized Shiv). Finally, there is yet another two-bolt system specifically designed for linear-pull brakes. All four systems require dedicated frame and fork fittings, and none of them are interchangeable.
It is probably more important to pay attention to the fittings for a rim brake (single-bolt centre-mount or dual-bolt direct-mount) than its compatibility with any given brake lever.
There are also two kinds of brake pad holders for rim-brake callipers: Shimano/SRAM and Campagnolo. The brake pads designed to fit one type will not fit the other. Fortunately, aftermarket brands like Swissstop and Kool Stop typically create pads to suit both types of holders, so it is simply a matter of matching the style of pad to the brand of callipers in all instances except one: Campagnolo’s Potenza brake callipers are actually fitted with Shimano/SRAM-style brake pad holders.
For those using road disc brakes, hydraulic levers and callipers from Shimano, SRAM, and Campagnolo are not interchangeable. Part of the reason for this is that SRAM uses DOT 5.1 fluid for its disc brakes while Shimano and Campagnolo use mineral oil. There are also differences in fluid transfer from the master cylinders, hose specifications, and fittings that will further complicate mating one brand to another.
Each brand of disc brakes also employs its own brake pad shape so it’s not possible to swap the pads from one brand to another. Furthermore, there can be differences in the pads used by different models of disc brake callipers from the same manufacturer (e.g. Shimano’s flat-mount callipers use a different pad from its older post-mount callipers), so buyers need to know the brand and model of calliper when shopping for new pads.
Those differences do not extend to the rotors, though, so it is possible to use any brand, including aftermarket versions, so long as it is the right diameter. The only other consideration relates to the calliper mounts, for which there are two: flat-mount and post-mount. Both require dedicated fittings on the frame and fork, so they aren’t interchangeable. An adapter can be used to attach a post-mount calliper to a flat-mount, however the reverse is not possible.
For an inventive industry that is largely free of standards, it is not really surprising that there is so much variation in the design of groupsets. While cynics may be quick to dismiss much of the resulting incompatibility as a marketing ploy to enforce a certain amount of brand loyalty, it has generated a pleasing array of unique and distinctive products.
Would there be any benefit to standardising the design of groupsets? Absolutely. Consumers would find it easier to replace any part at short notice, retailers would be able to offer more options to their customers, and service centres would be able to attend to all repairs and servicing in a timely manner rather than being forced to wait on the delivery of proprietary parts.
But there would always be a risk that those standards could get in the way of progress, slowing the evolution of groupsets. One need only look at how long it has taken the UCI to contend with the prospect of professional riders using disc brakes in road events to understand how much of an obstacle a system of standards can be.
Perhaps there will come a time when there will be widespread compatibility amongst components, but for now, consumers will have to continue to wrestle with the intricacies of groupset compatibilities.
What incompatibilities or surprising compatibilities have you come across when building or upgrading your bike?