Grind My Gears

Be careful who you listen to...

Why Other People's Drivetrain Reviews Suck

Because they don't know how to shift gears. So, you're complaining that the gears on your expensive cassette bent? You need to learn how to shift. This is not a defect of a gear cassette. This is a defect of you.

How not to shift

Start to ride up a hill in a nice high gear, realise you need to change down, poke the shifter into the lowest gear, continue to apply power to prevent loss of motion... and listen in horror to the scary noises coming from the drivetrain. Hugemungous sideways load on the gear teeth. Instant bent gears.

Perhaps expensive, precision-made components are not for you.

What to use instead, if you are a ham fisted chimpanzee

• No gears at all, perhaps a nice singlespeed.
• Really cheap cassettes made of steel.

Joking aside, by the way, I'm talking about angry users who've just broken something, posting up comments about why it sucks (mtbr.com reviews, etc). Not exactly unbiased reporting. So after all that, I'm going to do a quick review of XT and PG990 cassettes, yes, 9 speed, so not even the latest ones... Loads of us are still riding 9 speed bikes.

XT M770 and SRAM PG990 Cassette review

USA vs Japan, all star shootout featuring the top-of-the-old-9-speed-line for SRAM, and XT - the one-step-from-crazy-lightweight-race-bling-of-old-9-speed-XTR, for Shimano. 

Cost

No score draw here. I paid almost the same amount for each one - £40 and £42. Shop around, punters - there are deals out there. The RRP of approx £70 on these is crackers. Who wants to pay that much for a bunch of cogs? Yikes.

Construction

I'm going to subdivide this one...

Spider (with the big cogs)

Well, the XT has 5 cogs on the aluminium spider. And the SRAM has 6 cogs on the aluminium spider. Small win for SRAM.

SRAM PG990	Inside SRAM spider	SRAM gear #8 = failure to take advantage of double width gear

Remaining "loose" cogs

Shimano has 4 cogs and a couple of spacers. SRAM has 3 loose cogs, and managed to stitch the spacers to the 8th cog. Not a lot in it. The Shimano will chew up slightly more of your freehub.

So whilst I like the large spider with its big splines, I'm not that impressed with the small gears on either of these cassettes. Why? Because the entire force of the drivetrain is transferred through those very narrow splines, for these small gears. What would be better was if the spacer was integral to each small cog, the splines were double width. SRAM sort of managed it for just one of those three gears (double width gear but single width spline, gah!) but failed on the others. Shimano just bang out a flat gear and call it a good job (boo).

Of course none of that matters one little bit if you have a steel freehub, which would last intact until the death of the sun. But there does seem to be this somewhat common fashion for making freehubs entirely from aluminium...

XT M770, used and abused	Inside XT spider	XT loose gear = more narrow splines!

Durability

I have no idea how long the SRAM will last. I haven't ridden it to destruction. Yes, the pictures are of a brand new cassette, no, that's not the one I've been riding on for some time. Anyway, because of that, I can't really score them in this category. However, I got 2 years out of the XT cassette before it started to jump in my 'most used' cog. General concensus seems to be that the SRAM is slightly less durable... but as I want to write this post now, instead of in two years time, I can't call this one.

Shift Quality

Always had quick & precise shifts with both cassettes, using several different mechs (XT, LX) on several different bikes, yes, with different shifters as well. I have used a selection of chains (SRAM, KMC, Shimano) on both blocks. No, I never wrote down what combinations of chain and shifter and mech. None were stand-out bad, all worked just fine.

I couldn't tell which one of these was on the bike if you paid me. I'm going to conclude that means they both shift pretty damn good. That's unsurprising - both seem to have a similar looking arrangement of teeth that are cut just so to allow the chain to slide up and down the block like grease in a frying pan.

Overall

You know what, I make that one tiddly little point in favour of SRAM, who managed to make the 7th cog part of the spider. Honestly, I don't think there is a anything worth a damn in it between these two. They're both great bits of kit, narrow splines aside.