Find answers to the most frequently asked questions below (click on the question to see the answer)
Choosing narrow/wide chainring
To know whether you need GXP or BB30 chainring for your SRAM crankset, you should be aware of the type of bottom bracket (BB) installed on your bike. The BB type name is usually imprinted on the crankarm. However, in case it is not visible, you can measure the BB spindle diameter. GXP bottom bracket has a spindle diameter value of 24mm and BB30 - 30mm.
If you have a GXP BB installed, you will need a GXP chainring, and if your bottom bracket is BB30, then BB30 is the chainring you should opt for.
Also, modern BB30 bottom brackets' vary in width. Choosing GXP or BB30 chainring is up to the width of your BB spindle too. We made a simple scheme that will help you define what chainring to pick depending on the width of BB spindle on your bike.
In order to install the chainring directly on the crankarm, your crankset must offer an option to remove the spider. It is easy to find out if you can remove your crankset spider by using method shown in the picture below. Small but visible gap between crankarm and spider indicates that spider can be removed.
There are two ways to find out BCD value:
- from the specs sheet for your crankset provided by the manufacturer;
- by using our scheme below. Simply measure the X value as shown in the picture and find corresponding BCD value.
While designing our direct mount chainrings, we aimed at getting highest possible ring offset - that would result in much more appropriate chainline. Unfortunately, it is impossible to use big chainrings (e.g. with 38T and bigger) with high offset, because the ring will contact the lower chainstay on most bicycle frames.
Different manufacturers apply their own mounting standards to their cranksets, for example:
- SRAM uses a mounting system where crankset spider is attached to the crankarm with three TORX screws, so you will need a TORX screw driver;
- RaceFace crankset spider, as well as Cannondale and Specialized-designed ones are mounted using lockring: in order to detach these spiders, you will need a bottom bracket tool.
Tuning your bike drivetrain
In order to get the most reliable bicycle drivetrain it is important to maintain optimal chainline. Mis-tuned drivetrain entails intense sideward chain movement, resulting in high chance for the chain to come off. The most common reason this happens is because of inaccurate frame design. For example, bottom bracket, which usually has shell width of 83 or 100mm, is narrower than rear hub, which is 135 or 142mm wide - this causes significant sideward chain movement when shifted to the biggest cassette sprocket.
If you own a DH, FR or enduro bike, you can use chain guide with our chainrings to get a trustworthy transmission. For reliable yet minimalistic setup you can use merely top guide - this should be enough for keeping the chain on even in extreme conditions. If your riding style is not all about fast jumps and sharp movements, there is no need in using chain guide with our chainrings.
Derailleurs with friction clutch greatly improve drivetrain reliability. We highly recommend using derailleurs with friction clutch as they are very effective at not allowing the chain to slap around too much.
Oval chainrings work as good as round ones with SRAM type 2™ or Shimano Shadow Plus™ rear derailleurs. Derailleur cage position diverges in 2-5mm range, which does not affect pedaling nor shifting.
No, our narrow/wide chainrings are incompatible with front derailleurs. We designed our chainrings in a such way that wider chain link has to be put exactly on the wider ring tooth and narrow link should be on the narrow tooth to ensure maximum drivetrain reliability. When shifting gears, the chain cannot always stay in correct position on the ring, which causes the chain to drop.
Our chainrings are compatible with 9, 10 11 and 12-speed bicycle chains produced by all existing manufacturers. Keep in mind that 10, 11 and 12-speed chains are less likely to drop compared to 9-speed. This has been achieved by making chain links narrower, which resulted in smaller gaps between the chain and chainring teeth. If you have any doubts, feel free to drop us a message here
Chainline. What is it and how it affects riding efficiency
Chainline is a distance between bicycle frame center and a front chainring, measured in mm.
You can determine whether your chainline is good or not by looking at the chain position. Perfect chainline ensures that the chain is not bent when shifted to the center cassette cog. Optimal chainline value for 10-speed drivetrains is 45.5 - 46.5mm (with 135 or 142mm rear hubs), which varies depending on model of the cassette and rear hub installed.
Chainline on most of modern bikes is far from perfect: take, for example, a single chainring SRAM XX1 crankset, which has chainline value of 49mm. On one hand, companies making bike frames should consider design of the cranks that will be installed on the same frame (and they not always do such researches). On the other hand, cranksets manufacturers do not make cranks that will fit perfectly into every bike frame. All this results in incompatibility issues as the worst case scenario and poorly aligned chainline as one of the most common issues.
When chainline is improperly aligned, this causes additional noise and faster drivetrain components wear. Moreover, incorrect chainline increases the chance for the the chain to drop.
Our direct mount chainrings, as well as 76BCD SRAM XX1 and FSA 386BCD rings offer the best chainline values with our Variable Chainline Technology. We recommend installing BCD rings as close to the frame as possible: on a triple crankset, for example, you will need to install chainring in the position where second ring would be by default. When replacing the original chainring on a double or single crankset, you can use spacers to get the best chainline for your bike.
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