Mountain Bike Maintenance

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This is a guide for overhauling a rear Shimano Deore cassette hub, which uses cup and cone bearings. The cup is the bearing race which is built into the hub; the cone is the corresponding race which is threaded onto the axle. Whilst cone races can be replaced if they are worn or pitted, the cups of the hub can not. Any pitting or excessive wear to the cup races is terminal and means replacing the entire hub.

Although there are some very small variations in components (mainly seals) this guide should be relevant for hubs up to, and including, Deore XT. I have no experience of XTR hubs. The hub shown is the non-disc version, although I have no reason to believe there to be any notable difference in components in a disc hub (any information to confirm/correct this assumption would be welcomed). There are no procedures required to overhaul a front hub which aren’t covered in this guide.

I don’t re-use bearings. If you’re dismantling the hub for any reason other than general maintenance (broken axle?) and intend to re-use the bearings, keep the drive and non-drive side bearings separate as they may not wear evenly in relation to the cup/cone races. They should be cleaned with WD40/degreaser and a clean cloth, or tissue, rinsed with Isopropyl Alcohol (IsA) and then dried thoroughly. Keep an eye out for any dirt/grit or small pieces of metal as solid contaminates will lend themselves to the premature destruction of bearings and cup/cone races. Also look out for pitting on the bearing surfaces (see picture 15). Always replace bearings in sets as a new bearing will be larger than one which has been in operation and will cause uneven wear of the races.

The specialist tools required for this job are: a chain whip; a cassette removal tool; a set of cone spanners; 15mm (13mm for front) and 17mm, and, if you’re removing the freehub body, a 10mm Allen key.

It’s worth having a small plastic container handy to drop parts into, as they will all need to be degreased and rinsed.

The bearings in a Shimano rear hub are ¼” in diameter and each race contains 9 bearings. Front hub is 3/16″. Expect to pay around the £/$5 for good quality bearings, Grade 100 or better (try SJS Cycles in the UK).

Remove the wheel from the frame and remove the cassette (1) (seven speed bikes will also have an aluminium spacer (2)) and lay it down on the drive side. Using a small, flat-headed screwdriver, carefully prise the rubber seal away from the non-drive side end of the hub. The easiest way to do this is to nip the seal between thumb and forefinger to elongate it before inserting the screwdriver into the space created. I dismantle the hub assembly from the non-drive side. Picture (3) shows the cone/axle assembly. Whilst a 15mm cone spanner is required to hold the cone, I’d advise using either a ring spanner or socket wrench to hold the 17mm nut at the top of the assembly. Holding the cone in place, loosen the top nut (4).

One of the reasons I take pictures of the work I do is in case I forget how things go back together! One great way to keep assemblies in the correct order (thanks to Park Tool’s excellent website for this..) is to drop a large washer onto a cable tie, push the other end into the axle and feed all the components onto the tie as they are removed (5). The cone race itself has a metal shield pressed onto it which should be left in place (6). Holding the wheel vertically, remove the axle from the drive side (with cone assembly still in place). Tilt the wheel towards you and, using something like a pen top (not metal), carefully extract the bearings onto a container (7).

Flip the wheel and do the same for the non-drive side.

Remove all of the old grease from the non-drive side cup using tissues and cotton buds.

The drive-side cone assembly comes apart in the same way as non-drive side. Disassemble and thoroughly clean (remember to rinse with IsA) and dry all components.

If you wish, the freehub body can now be removed using a 10mm Allen key (8). Note the splined boss that the freehub sits on (9) and the unusually shaped washer (10). Servicing of the freehub body is limited. Remove all the grease from the cup race using tissue and cotton buds. Do not use a degreaser as it will spread into the freehub mechanism and ‘clean’ that out also. Wipe the exterior and carefully prise the ring seal on the back of the freehub body. Using a tissue, carefully wipe the ring of bearings. I apply a very thin ring of grease around the bearings before replacing the seal, although ideally you would use a very light oil. When the seal is fully in place, wipe away all excess grease as it will only attract dust. Refitting is simply the reverse of removal, just don’t forget the odd shaped washer. Also, make sure that the freehub body is sat firmly on the splined boss and that the retaining bolt is threading smoothly into the hub. Picture (11) shows the entire drive-side assembly. Note the flattened thread of the axle. The drive-side cone can now be re-assembled (12) leaving around six threads exposed on the end of the axle. The axle from an XT hub may have about 5/6mm without thread on each; set the outside of the cone assembly 1/2 threads in after the flat section.

As I said at the beginning, corrosion, or pitting, of the cup surfaces more or less spells the end of a hub. Now that everything is spotlessly clean (at least it should be!), you can inspect the bearing races. As you can see in picture (12) a race may have a line worn into it; this is acceptable as long as the surface of the race is smooth. Closely inspect both cone races for any signs of uneven wear or pitting (you could even use a magnifying glass). Generally speaking, a cone race will wear out before a cup race, so if you catch corrosion on the cone you’re in with a good chance of being able to remedy it before it affects the cup race. A worn cone will cause uneven wear to the bearings, which will transfer that damage to the cup race. As you can see in pictures (13) and (14) the cup races on this hub are immaculate. The cup in picture (15) is clearly not. This kind of pitting will destroy bearings in a very short amount of time (and it did!) and is not repairable.

Once you’re satisfied that all is well you can fit fresh bearings. I use Pedro’s Syn Grease, and recommend it highly. It’s a good, thick grease which doesn’t break down (like white Lithium will), and works well to help seal water out of your bearings.

A grease gun or syringe is perfect for running a ring of grease around the cup race. A small amount of grease on the end of the pen top will stop them from rolling away (16). Starting on the non-drive side, carefully replace all the bearings and run another ring of grease over the top of them (17). Smooth it down with the back of the pen top. Don’t go mad with the grease; too much will create its own excess friction. Flip the wheel and follow the same procedure to install the drive-side bearings into the freehub body (18). Once you’re done, insert the axle (with drive-side cone assembly already fitted) into the freehub body, taking care not to dislodge any bearings from either side on the way through. Keeping a finger on the drive-side end of the axle, flip the wheel and refit the non-drive side cone by screwing it down the axle until it just touches the bearings (19). Refit the rest of the assembly, turning the top nut to finger tight.

All refitting adjustments from this point should be made from the non-drive side.

The idea behind cup and cone bearings is that the two races sandwich the bearings, but with the smallest amount of compression possible. Too much and the excess friction on the bearings/races will eventually cause them to disintegrate under load; not enough and the assembly will move around on itself, ultimately causing uneven wear on the bearings and races.

So, once you’ve screwed the cone down to the bearings, back it off again by 2/3 minutes (60 minutes being one full rotation) and, holding the cone with the cone spanner, tighten the top nut.

Hold the axle at each end and wiggle it, then rotate the axle. Remember that you’ve just put fresh grease in the hub, so it’s not going to be super-smooth, but the axle should spin feely (try over-tightening slightly to get a feel for this). There should be no lateral play in the axle.

Sometimes the tightening of the top nut will compress/relieve the assembly slightly, adjusting the adjustments you’ve made. If this happens, you’ll have to go back to square one and re-adjust the cone, taking into account the affects of the top nut. Loosen the nut; adjust the cone; tighten the nut; check; repeat until axle spins freely and without play…

When all feels right, the final check is done with the wheel in the frame. Refit, tighten the bolts/QR; this will compress the assembly a small amount and should be considered part of the cone adjustment procedure. Then give the wheel a gentle spin. It’s actually easier to determine how freely the bearings are rolling by the way the wheel stops. Of course, listen out for any obvious friction, but the wheel should actually be brought to a halt by the friction of the pawls in the freehub. Hold the wheel at top and bottom and check for play in the axle. With experience, any adjustments at this point can be done with the wheel in the frame, but it is much easier at first to remove the wheel.

This guide and the photographs contain within it are my property and as such are covered by copyright. Please feel free to provide links to this guide, but do not copy or reproduce any part of it without my permission.