Servicing the Cassette and Pawls on an XD Driver

This instructable covers how to identify an aging drivetrain on a mountain bike, how to remove/replace a cassette, and service the pawls on an XD driver.

Tools may vary a bit depending on bike and cassette manufacturer.

3mm Allen

4mm Allen

6mm Allen

T25 Torx

Torque Wrench (1Nm-5Nm range)

Pliers

Cassette Socket and Wrench

Chain Whip

Chain Breaker

Soft Brush

Light Assembly Grease

Isopropyl Alcohol

Nitrile Gloves

A clean bike is a fast bike. And they last longer, because moving parts don’t like to use gritty mud as lubricant. It’s also easier to work on. So step 1 is to hose it down. Avoid the pressure washer — there’s some debate, but most people agree that pressure washing bearings and seals damage them.

Cassettes and Chains are wear items. They’re not going to last as long as the bike, so they need to be replaced at regular intervals. Cleaning them after every ride, especially muddy and dusty rides, will help them last significantly longer.

Skip ahead if you don’t care how to identify a worn chain or cassette

How can you tell if they’re worn out?

Chains wear out faster than gears, and a worn chain will damage a cassette.

A bike chain has a 1/2” pitch, meaning the pins in the chain are exactly 1/2” apart. Or at least that’s true of a new chain. The pins and bushings wear down, so the chain stretches. The rule of thumb is to replace the chain at or before 0.5-1% stretch. They make special tools for measuring a chain, but a ruler will suffice. 12 links = 12”. If it’s 12-1/8”, that’s a stretch of about 1%.

A quality and well maintained bike chain should last around 500-750 miles.

When the chain stretches it wears the cassette faster than normal. If you’re replacing the chain often enough, the cassette can last 3-4 chain replacements; but if you're riding around for too long on a worn chain, a new chain won't fix a gear-skipping problem.

The cassette develops what’s called “shark fins” on the teeth. The valleys between the gears can also elongate and become misshapen from a stretched chain. Both of these problems can cause the chain to skip a tooth while under load.

First thing to come off is the rear wheel. To do this, disengage the clutch on the derailleur. It varies per manufacturer; this could be an on/off switch or a push-to-lock button. The axle comes out, usually with a 6mm Allen, maybe with a quick release.

I prefer to remove the brake disc too, because inadvertently bending it is a high probability and a nightmare to fix.

Now it’s time to get into the specialized tools. First up is the chain whip. I use the Park Took SP-1, but there are cheaper options on the Amazon. This tool is the USB drive of bike tools: you’re going to try using it upside down, then flip it but that doesn’t work either, then it’ll somehow work the first way you tried it. Check my image for a cheat on which way it goes.

You’ll need the cassette socket and wrench with the chain whip. Use the chain whip to hold the cassette while loosening the cassette nut in the center of the hub with the socket. The cassette socket is usually a 1” OD. I use a wrench to turn it. It takes bit of force to get it off, as they’re usually torqued to 40Nm. It is not reverse threaded. Lefty-Loosy.

If you’re not cleaning the pawls, skip ahead.

Disassembling the driver/freehub body:

Unthread the Top Cap. It is reverse threaded, so… Righty-Loosy.

Driver body should lift straight up with a little wiggling. Rotate to the left if it’s being stubborn. There shouldn’t be any loose parts in there that’ll spring across the work bench. If loose springs fly across your work bench, it's probably broken.

Now that the parts are out, it’s time to clean.

All the little bits of mud and dust that have creeped past the seals are what will cause premature failure.

I use isopropyl alcohol and a soft brush to clean everything inside the freehub body. The higher percentage, the better. An old toothbrush works well. I’m using a cassette brush in these photos.

The freehub body has a double sealed bearing at either end of it, separated on the inside by an aluminum tube spacer. The outermost bearing is usually removable without tools. Then everything can be thoroughly cleaned, lubed, and reassembled.

Lubricant

Light lubricant is best on all of these parts. 10wt oil is recommended for the pawls. I use sram butter on all threads, splines, pawls, and pretty much everywhere that metal contacts metal.

Axle Grease is not recommended. It's made for high-load applications where there is a LOT of pressure. In a bike hub, most of the bearings are sealed roller bearings, which you replace instead of lubricate.

Lithium Grease is better, but still too thick. It works well for threads and quieting metal-on-metal clamps, but would slow the effectiveness of the pawls. I can't confirm, but I would expect some missed engagements in the pawls if you used lithium grease.

Wipe off any excessive lube, as it will attract dust and dirt on the trail.

Reassembly procedure is the reverse order of Disassembly. Don't forget the Freehub cap is reverse threaded.

I'm installing an E13 TRS+ cassette instead of the factory Sram Eagle, and they use a completely different system to hold the cassette to the freehub. On both cassettes, you need to be aware of the asymmetrical splines on the free hub.

If you look at the splines on the freehub body, you'll see there is one spline that is smaller than the rest. This is an indexing spline, and it ensures that the cassette can only be installed one way.

The Eagle cassette is a one-piece design and is threaded onto the freehub body (righty-tighty). It's held on by the threads, but all of the forces from pedaling are transferred directly to the splines on the hub. To install the Eagle cassette, line up the splines and drop the cassette onto the freehub body. Use the cassette socket to torque to 35-40 Nm. Careful lining up the threads - they're a very fine thread pitch, so cross-threading is easy.

Installation of the E13 cassette is just as easy, but it's very unique to E13's design. It's manufactured in two halves, connected by a tab-and-slot with an indexing screw.

First, the splines on the cassette are pretty universal - in my case, it slid right on there without any difficult alignment. There's no threading onto the freehub body. Press the cassette firmly in place and torque the clamp as indicated. 3Nm is not much force. You definitely can't use the same torque wrench as your lug nuts on your car.

Next, lube all contact points of the small half of cogs. Try not to get grease everywhere. It's difficult to clean off here, and best-case scenario is only attracts dirt, worse-case scenario it will contaminate your brakes when it flings off at high speeds.

Align the indexing screw to just-before its hole. Using the chain whip, rotate the small, top-half of cogs righty-tighty (CW). It looks easier on paper - I had to apply downward force on the cogs to get the tab/slot to line up correctly.

The indexing screw is torqued to only 1 Nm. Even with a bike-specific torque wrench, it's difficult to feel the faint click of reaching torque. It's basically: once the head of the screw is flush with the face of the nearest cog and you feel the slightest increase in resistance.

To finish installation, clean it with isopropyl alcohol. Remove any excess grease so it doesn't attract dirt.

Don't forget to reinstall the brake disc if you removed it.

Always install a new chain when installing a new cassette. New chains need to be sized to the appropriate length.

Most chains are going to need to be disconnected in order to take them off. Locate the master link or quick-link and use pliers or a pair of master link pliers to remove it.

If you replaced your old cassette with the same gearing, you can count links or lay your old chain next to your new one to get the correct length.

As you can see in the photos, I had quite a bit of stretch on my old chain, but laying the old and new chains next to each other was still within a link of overall length.

Use a chain breaker to press out a chain pin at the appropriate location.

Check your chain length by putting your bike in your tallest and shortest gears and checking derailleur angle. Keep in mind that on full suspension bikes you may need to allow for what's called chain growth. When the bike suspension compresses, the rear axle moves away from the pedals, effectively growing the minimum chain length. It varies per bike, but you can deflate or remove the rear shock and compress the suspension to check.

In the lowest (biggest) gear, the derailleur should point mostly forward, but still have a little forward movement available.

The highest (smallest) gear, the derailleur should keep the chain from hanging loose and the chainline should not touch the body of the derailleur. You can see in my picture that the chain was too long and the chain was touching the body of the derailleur in the highest gear. This is easily fixed by removing a link and rechecking.

It's entirely possible that everything will shift perfectly and you won't need to do any adjustments. But if you do, here are some helpful tips..

First of all, if you changed your cassette with a new gear ratio, you'll need to adjust your B-limit screw or get a longer one. This screw adjusts how far your derailleur is from the axle centerline. If you now have a larger big cog, you'll need to turn the screw in, which pushes your derailleur out.

If you need to realign your gears so they shift right, there's a guide on the Youtube for it: Here

Assuming you're not adjusting your high and low limit screws, here's a quick and dirty:

There's a fine-tune adjustment on the shifter on the handlebars. Turn it all the way in.

Shift into the lowest gear.

On the derailleur, loosen the 4-5mm screw that holds the cable taught.

Put just enough tension on the shift cable to make it straight, not tight. Then re-tighten the 4-5mm screw.

Fine-tune via the adjustment on the handlebars.