Friday, October 30, 2015

Servicing a DT Swiss 350 through-axle rear hub

How do you get Matt, the DT Swiss after-market rep for North and South America, to come all the way from his base in Grand Junction, Colorado, to your home in Canada, to service your hub?

It all started more than 15 years ago when Matt was in Grade 8 at a school near me. One day I'm on a road ride when I meet Matt and a buddy of his trying to train for an upcoming mountain bike race. We got to talking, I offered to coach him, and despite our age difference (I was in my 30's at the time) my wife and I became good friends with Matt and his family. Fast forward a few years and Matt's family has moved back to Colorado, and Matt's Navy service has sent him far away. We kept in touch.


In 2007 we headed out together on an epic-a-day ride adventure across Colorado and Utah. While passing through Grand Junction we meet Creig from the DT Swiss headquarters there. Creig generously shows us some local rides and totally schools us on his one-speed.

Fast forward to last year, when Matt's in Chicago looking for a career change. While bouncing around some ideas I reconnect him with Creig in Grand Junction. Soon Matt is off to GJ to become the Americas rep at DT Swiss.

As I teased Matt when he visited last weekend, it was all just a long con for these hubs. Pretty sweet though, because he was kind enough to bring me a new freehub and tool to fix my 350 rear hub. The bearings on both the rear and front hubs had developed an annoying squeal after an extremely wet weekend of riding at Vallee Bras du Nord near Quebec City. Since this was something I could fix, it was going to get fixed!

The DT Swiss web site has a bunch of information on servicing their gear. My 350 rear hubs have the through-axle and ratchet so I followed the instructions on page 44 of this guide. The instructions are pretty good, but if you don't have all the tools in the guide, you can do what I did.

First, remove the axle end caps by sticking a wooden dowel in the end and yanking it sideways. The caps should just pop off. Then you can pull off the free hub by just grabbing it and pulling straight out. Here's the ratchet system that lurks beneath:

Here's the old and new free hub (bearing installed), and the special DT Swiss tool which you'll need to access the bearing left in the wheel hub. This is the only special tool you need to complete the job.

Remove the ratchets and springs, and give them a good cleaning. 

Now flip over the wheel and tap on the axle with a hard rubber mallet to drive out the bearing on the brake side. Don't beat on it because the axle is soft aluminum, and you could punch out the inner bearing race leaving the outer race stuck in the hub. 

The bearing is tight but should come out with gentle persuasion. Do not reinsert a new bearing now, no matter how tempting!

To remove the bearing on the free hub side, first you need to remove the ratchet outer part that's threaded into the hub. Slot the tool into the splines and clamp the tool in a vice. This is a real bitch to twist off and you will definitely need some full-out torque on the wheel. No way this comes off with one hand like in the DT Swiss manual!

Ta-da! Remove the thin black spacer that sitting on top of the bearing. 

Now you can use the axle placed from the other side to gently tap out the bearing if necessary.

You can use the square end of the tool to tap in a new bearing here. All the bearings in the rear and front hub are a 6902. ABEC 5 grade should be fine. I used a 6902 2RS (meaning 2 rubber seals) because I had those on hand; the original version is 6902 LLB (better seal). This is a great explanation of bearings for you to geek-out on. Turns out that both hub bearings in my rear wheel were fine, so I just cleaned and lubed them. However, the free hub bearing was rough. Replacing that with the new free hub (bearing pre-installed) and cleaning the ratchet solved the squeaking problem.

When reinstalling the bearings give them a thin coat of grease. I used Slick Honey. You can tap them in with the DT Swiss tool. Just be careful to keep the bearing square to the hub or you risk ovalizing the bearing or hub.

Reassembly is basically the reverse of disassembly. Grease the spacer, and thread the splined locknut over it. Note that the locknut goes flat side up. There's a recess on the other side that fits over the spacer; be sure the spacer is centered within it.

Use the tool to tighten the splined lock nut. Give it a good twist with a wrench; it doesn't need to be hernia-inducing tight like it comes from the factory (I have that on authority from the factory).

Then pop this gasket in.

Pro tip:

Insert the axle BEFORE installing the new bearing on the other side of the hub! 

If you do forget (like we did, in a boneheaded maneuver), you'll need to use a drift from the other side to gently tap out the bearing, because there isn't an axle already in there to tap on!

Now you can grease and install the bearing on the brake side. Note the axle now in place. If it sticks out further than this, pull it out turn it around.

Tap in the new bearing using the square end of the tool.

Fully seated:

Insert the bottom ratchet spring, narrow end up.

There's probably some exotic Swiss raclette ratchet grease for this next step. I used Moly 60 which is unnecessary geek overkill and expensive but was already on hand for servicing my air rifle pistons and assembling engines. A tiny amount goes a long way and it's slippery stuff indeed.

Insert top spring in the free hub, narrow end out.

Careful observers will note that you should now also insert the short aluminum spacer inside the ratchet mechanism.

Snap the free hub onto the hub. A little tap with a mallet will seat it.

Pop the axle caps onto both sides.

And that's all there is to it! A big thanks to Matt for years of great friendship, and to DT Swiss for sending Matt to me with swag. These are great hubs and should give many more years of reliable use.

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