Sun Ringlé Dirty Flea front hub inspection

A friend of mine dropped few bits for me to build a new 29er wheelset.

Before the lacing process I had to keep an eye onto the front hub as one of the bearings had popped out from its original location and as a result the axle was moving back and forth. Time to take a look at a typical modern CNC hub that uses industrial bearings.

The tools you need are very basic. You will find these sort of hubs are even more simple than classic cup and cone units. The homemade bearing press consists on a threaded axle, washers and nuts. It is operated by adjustable spanners.

To service a rear hub you only need a couple of 5mm allen keys and wet lubricant on top to service the freewheel

To service a rear hub you need a couple of 5mm allen keys, a circlip plier and wet lubricant on top to service the freewheel

The first thing to do is pry out the end cups from the axle. I did with my nails :mrgreen:. Now the bearings are exposed, tap any side of the axle ends gently with a mallet or rubber hammer. Bearings are pressed inside the hub shell, that’s why we need to tap. A much more clever method like a bearing puller won´t help because there is no room. After tapping, the oposite bearing and axle will come out together. Take apart bearing and shaft. You are going to fit the axle inside the hub and bearing bore again to take this one off the same way.

Full front hub dissasembly

Full front hub disassembly. Notice this hub comes with a 9mm axle type

As you see, the axle supports the fork in their 9mm ends and is also perfect to remove bearings because it has a barb that protudes a little to push out the bearings. The 6001RS bore is 12mm, quite uncommon by the way if you are planning to look for them in a hardware shop.

You can upgrade the front hub with ceramic or hybrid rollers, but in my opinion it does not worth the price. It is possible as well for silly money to convert the hub to a 15mm Thru Axle. In that case, new size bearings and caps are mandatory.


15mm axles are easier to produce and at the same time noticeable stiffer

Checking that everyting was OK and after cleaning the shell I proceeded to put the parts back together.

Because bearing’s cage are made of steel and the hub from aluminium, I applied some anti-seize compound sparingly to the hub to avoid galvanic corrosion.


Finish Line copper based anti-seize paste

My cheap homemade press is essential not to screw up bearings when fitting them back.

I’ve got lots of washers to play with different bearing sizes

Once one of the bearings has been installed we can fit the axle. Thankfully the axle doesn´t go so tight inside the bearings as the outer race of them do against the hub. With just our fingers we will manage to insert the axle to the bearing that has been already pressed and then do the remaining one, this time without pressing.


At this stage there is one bearing left to be put on

Without the possibility to use the homemade tool anymore, washers and surprisingly helpful spanners will  ease the task of fitting the last bearing.


The hole of both spanners are perfect to tap the end caps safetely by buffering the 9mm axle ends

With only two washers on hand I decided to use the spanners to conceal the axle as I did with the washers on the other side of the hub. Otherwise the bearing would not go in.

Remember the axle middle section barbed design is made so that it helps to pop out bearings and hold the inner roller exactly at the place the stepped wall machined shell stops the outer bearing race. We start off fitting with our hands the bearing carefully so that it goes straight, and finally we put on the end caps and washers. Tap on top of the pile (picture 4) until you notice the bearings reach their final position. Washers will push the end cap, and this one, will do the same with the bearing. If we use enough stack height to hide both axle entries we should end up after tapping with both bearings inserted till the end.


This is a good weight for a front disc hub. Not a extreme light part but perfect for a bombproof wheel

If you’ve ever wondered how is it the Sun Ringlé Dirty Flea rear hub I will show you:


Yes you are right, the circlip is missing and the splines sheared off

We are done!


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