Question: I’ve read on various Internet forums where riders are using 10-speed chains with SRAM XX1. Can you confirm that it’s possible to run a 10-speed chain on SRAM’s 11-speed mountain groups?
Possible? Yes. Prudent? Well, read on…
Why it’s possible
Some of the cleverest design elements of SRAM’s 11-speed mountain groups are also the most subtle. Take for example the cassette: SRAM didn’t attempt to cram 11 cogs in the same space previously occupied by 8, 9, and 10-speed cassettes. In these three previous cog additions, the chain as well as the teeth of the cassette were made increasingly narrow to fit onto the freehub body.
In the case of XX1 and XO1, the smallest 10 cogs occupy the same space as a 10-speed cassette. The 42-tooth cog is essentially dished inward from the actual freehub body. (If you look at an XX1 or XO1 cassette installed on a wheel in profile you’ll see what I mean.) As a result of “cheating space” from the cassette, the teeth on SRAM’s 11-speed mountain bike groups are only marginally narrower, as is the spacing, compared with its 10-speed groups.
Last summer, I was riding a test bike equipped with XX1 when I managed to wedge a branch in the drivetrain. The stick won; the PC-XX1 lost. I shortened the chain and limped home. I had a race the next day and was in a bind. I replaced the shortened PC-XX1 with a properly sized PC-1071 I had in my toolbox.
The 10-speed chain shifted through all 11 cogs just fine, though I removed it and installed a PC-XX1 at the earliest possible opportunity. Although it worked OK and the differences in spacing and tolerances are “only marginally” different, those margins matter.
Why it’s not the best idea
Many of the riders running 10-speed chains on SRAM’s 11-speed mountain groups are likely going this route for one of two reasons:
1. They have an existing stockpile of 10-speed chains to burn through.
2. Many 10-speed chains can be found cheaper than SRAM’s XX1 offerings.
In both cases price is the primary concern, not performance. I can understand this; like any other high-end mountain bike group, SRAM XX1 and XO1 come with a premium price tag. But if you’re going to spend the money, it’s prudent to take care of your investment.
As one would expect, SRAM cautions against running anything other than a PC-XX1 with a XX1 or XO1 drivetrain. The company states that using a 10-speed chain with one of its 11-speed drivetrain will void the warranty.
The difference in the external width between 10-speed and 11-speed chains is very slight, but could be enough to cause premature wear to the cassette. You are essentially attempting to save money on a chain while risking the longevity of a very costly cassette.
Don’t be penny wise and pound foolish. A 10-speed chain can work in a pinch, but the risk of premature wear to one of the most expensive parts of the drivetrain is worth avoiding. Replace your worn or broken PC-XX1 chain with another one. A better option if need an immediate replacement is to use an 11-speed road chain, as it has similar dimensions to the PC-XX1. SRAM contends this is the next best option, though the company also points out that the PC- XX1 uses a Hard Chrome plating and is designed specifically for the rigors of off-road use.