CX Wheel build and hub advice

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LinusR
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CX Wheel build and hub advice

Postby LinusR » 5 Jan 2018, 10:10am

I want to build a spare pair of wheels for my Cannodale CAADX Tiagra cyclocross bike. I use it in the winter for group rides with 28mm slick tyres and in the drier months I ride it off-road with 35 mm grippier tyres (sort of easy gravel grinding). I'm happy with the wheels that came with it but I'd rather have a spare pair instead of swapping the tyres over. (Incidentally, I've already replaced the Promax render brakes with Avid BB7 on the front and TRP Spyre on the rear, which is a vast improvement.)

I've built wheels before (Campag on Open Pro) and can service a hub myself. I'm considering using Mavic XC 621 rims laced to Shimano Deore or XT hubs with centrelock for discs (160f; 140r), and using 32 double butted j bend spokes laced 3 cross. This build would cost around £250. I don't want to spend much more than that. If I go with Deore I'm limited to 10 speed, while XT I can use 10 or 11 spd. But I'm quite happy to use 10 speed. Lighter is nicer but I really want it to last ten years or more. I'd like the option to go tubeless.

However, I'm having second thoughts about the Shimano hub after reading reports about the freehub body failing (including this thread https://forum.cyclinguk.org/viewtopic.php?f=5&t=111550. I've broken spokes in the past (not very often) but I've never had a freehub body fail (yet). So are Shimano's M6000 and M8000 freehubs not recommended?

While I'm dithering over the hubs should I consider buying a pair of cyclocross wheels similar to the OEM wheels which came with the bike and are pretty serviceable as they have j bend spokes and loose ball bearing hubs. I'd rather not use cartridge bearings. Any suggestions?

iandriver
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Re: CX Wheel build and hub advice

Postby iandriver » 5 Jan 2018, 10:29am

You can still get the previous version of the XT hub, http://www.chainreactioncycles.com/shim ... p-prod3987
Still love these hubs personally.
Supporter of the A10 corridor cycling campaign serving Royston to Cambridge http://a10corridorcycle.com. Never knew gardening secateurs were an essential part of the on bike tool kit until I took up campaigning.....

Brucey
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Re: CX Wheel build and hub advice

Postby Brucey » 5 Jan 2018, 11:18am

IMHO the only reason for using a modern shimano hub design (with a fatter axle and a potentially less reliable freehub body) is that it is slightly lighter than an older design of hub. The thing is that such hubs aren't that much lighter, so..... if you are at all risk-averse, want reliability/easy servicing, and you are on a budget, my advice would be to choose a shimano hub model with a conventional steel axle.

BTW when er, weighing up hubs, don't forget to allow for the extra weight in the centrelock discs and retaining ring. Also note that large flange hubs generate significantly lower loads in the spokes when the brakes are used hard, so ought to allow the rest of the wheel to be built a bit lighter, for any given duty.

Finally the choice in centrelock discs is obviously more limited and they often cost more too. Some CL discs are marked as 'suitable for resin pads only', too, so if you intend to run sintered pads then you need to be even more choosy. There is much more choice in 6-bolt discs.

cheers
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LinusR
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Re: CX Wheel build and hub advice

Postby LinusR » 5 Jan 2018, 6:31pm

Thanks iandriver and Brucey for your speedy advice. The XT M756 seem a better bet for the reasons you've stated. I note the points about the disc rotors, and the large flange hubs.

reohn2
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Re: CX Wheel build and hub advice

Postby reohn2 » 5 Jan 2018, 7:09pm

iandriver wrote:You can still get the previous version of the XT hub, http://www.chainreactioncycles.com/shim ... p-prod3987
Still love these hubs personally.

Me too and much cheaper here:- http://www.rosebikes.co.uk
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LinusR
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Re: CX Wheel build and hub advice

Postby LinusR » 9 Jan 2018, 2:20pm

I just got the Mavic XC 621 29" rims for the wheel build. I was surprised to see no hook on the rim. Only a slight hook either side of the central channel. I do eventually want to try these tubeless but will they be ok with tubes? The max pressure for 1.3in tyres is 45psi or 3 bars which is exactly what I run the 35mm (1.4inch) tyres at present. The internal width is 21mm but Mavic states to use 25mm wide rim tape. Is that right? I would have thought it should be 21mm.

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LinusR
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Re: CX Wheel build and hub advice

Postby LinusR » 10 Jan 2018, 7:24pm

I've just got hold of the Shimano XT HB-M756 and FH-M756A hubs for the wheel build. I've checked the rear hub right side cone and locknut is very tight and that the movement is free. I've tried to do the same to the front hub but I couldn't get my cone spanner between the locknut and onto the cone. I noticed the metal dust cover on the cone was at an angle, so I gently coaxed the spanner onto the cone flats and the dust cover moved just enough so that I could get the spanner in fully and make sure it was tight against the locknut. I didn't tempt fate by taking them apart to see if there is enough grease in there. They feel smooth enough. I'll wait until the two year warranty's up before I re-grease them. I also notice the rear hub has a metal dust cover instead of a rubber one, unlike the previous FH-M756. (All the M756A hubs seem to be like this so it's not a case of the seal missing on mine.)

ImageP1010012 by linusrees, on Flickr

Brucey
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Re: CX Wheel build and hub advice

Postby Brucey » 10 Jan 2018, 8:46pm

LinusR wrote: I didn't tempt fate by taking them apart to see if there is enough grease in there.

no need to look, there won't be enough grease inside!

They feel smooth enough.

they won't be correctly adjusted, they never are.

I'll wait until the two year warranty's up before I re-grease them.

Madness...... they'll be knackered by then unless you grease and adjust them correctly.

If you clamp a few M10 washers using the QR (in place of the dropouts) you will find that the hub bearings will start to bind. There should be a tiny amount of free play that just disappears as the QR is tightened. It is almost pointless doing this before the wheels are built, BTW, since the hub bearings adjustment is affected by the spoke tension in most hubs.

Some top tips for new shimano hubs;

1) The freehub body should be lubed with a SFG (or an oil if the sealing is good enough to keep it in there)
2) the main hub bearings should be packed with better (more plentiful, more waterproof, more corrosion resistant, more EP additives, preferably more fluid) grease than shimano use, enough to keep the seal lips wetted. The shimano grease confers almost zero corrosion resistance to the hub bearings.
3) In both front and rear hubs the RH cone and locknut should be tight against one another, preferably locked using threadlock (if these move in service, the hub will wreck itself). You will need to withdraw the rear axle by about 15mm on the RHS to check this. [Adjustment is done on the left side only; if the cone and locknut are not perfectly tight and they move, it won't wreck the hub.]
4) adjustment should be made so that there is a little free play in the bearings that just disappears as the QR is tightened to secure the wheel in the frame. Do this when the wheels are built.
5) precision bearings are manufactured with tolerances of a few microns. You can get your hub adjustments to be this accurate, but it requires that you are prepared to adjust the cones by as little as two or three degrees at a time until the adjustment is correct. QR pressure typically 'adjusts' the bearings by 70-80 microns, or about 1/12th of a turn of the cone) which is about ten times as much as the accuracy you should be aiming for.
6) A good starting point for adjustments is to wind the cone in finger tight and back it out about 1/5th of a turn. This allows a bit for the axle compression and a bit for the clearance in the axle screw threads.

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LinusR
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Re: CX Wheel build and hub advice

Postby LinusR » 10 Jan 2018, 9:33pm

Brucey wrote:
If you clamp a few M10 washers using the QR (in place of the dropouts) you will find that the hub bearings will start to bind. There should be a tiny amount of free play that just disappears as the QR is tightened. It is almost pointless doing this before the wheels are built, BTW, since the hub bearings adjustment is affected by the spoke tension in most hubs.


OK, I'll build the wheels and then make the adjustment. (I seem to remember doing this when I last built some wheels, Campag hubs on that occasion.)

Brucey wrote: Some top tips for new shimano hubs;

1) The freehub body should be lubed with a SFG (or an oil if the sealing is good enough to keep it in there)
2) the main hub bearings should be packed with better (more plentiful, more waterproof, more corrosion resistant, more EP additives, preferably more fluid) grease than shimano use, enough to keep the seal lips wetted. The shimano grease confers almost zero corrosion resistance to the hub bearings.
3) In both front and rear hubs the RH cone and locknut should be tight against one another, preferably locked using threadlock (if these move in service, the hub will wreck itself). You will need to withdraw the rear axle by about 15mm on the RHS to check this. [Adjustment is done on the left side only; if the cone and locknut are not perfectly tight and they move, it won't wreck the hub.]
4) adjustment should be made so that there is a little free play in the bearings that just disappears as the QR is tightened to secure the wheel in the frame. Do this when the wheels are built.
5) precision bearings are manufactured with tolerances of a few microns. You can get your hub adjustments to be this accurate, but it requires that you are prepared to adjust the cones by as little as two or three degrees at a time until the adjustment is correct. QR pressure typically 'adjusts' the bearings by 70-80 microns, or about 1/12th of a turn of the cone) which is about ten times as much as the accuracy you should be aiming for.
6) A good starting point for adjustments is to wind the cone in finger tight and back it out about 1/5th of a turn. This allows a bit for the axle compression and a bit for the clearance in the axle screw threads.


OK 1) I'm a bit squeamish about this as it's a long time since I took a freehub off. But I just need to get the axle out then unscrew it using a big allen key (I've got the Shimano exploded parts sheet) http://si.shimano.com/pdfs/ev/EV-FH-M756-A-3295.pdf Then I just gently pull the rubber seal off and squirt a bit of oil in there. My instinct is to use Finish Line wet lube. I've also got a tube of Finish Line teflon grease. Should I squeeze bit of that in as well. (I have a bad feeling about this...)
2) I have a grease gun and I'll use Finish Line teflon grease.
3) OK. I can do that. But I don't understand the need to pull the RHS of the axle about 15mm to check?
4) 5) and 6) I understand. No problem.

[edit] Do you know who at Shimano I should send my bill for getting their crappy hubs to work properly?

Brucey
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Re: CX Wheel build and hub advice

Postby Brucey » 10 Jan 2018, 9:38pm

you don't need to remove the freehub body to lubricate it. Just run gear oil into it from the RH end. If it leaks out too quickly, use something more like a SFG instead.

You can't usually get a cone spanner on the RH rear cone without withdrawing the axle a little.

I recommend that you don't use finish line wet lube inside a hub under any circumstances; it reacts with some other lubricants and turns to a foul gunge that trashes the seals.

I don't know of any hubs that will go for years with no maintenance, apart from midrange shimano ones that have been set up properly as per my suggestions.

If you just do nothing to a new set of hubs (any make) they will IME fail inside a few years. It is your choice but I'd rather set up hubs correctly when they are new than deal with a load of stuff that is knackered a few years down the line....

cheers
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LinusR
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Re: CX Wheel build and hub advice

Postby LinusR » 10 Jan 2018, 10:33pm

Brucey wrote:If you just do nothing to a new set of hubs (any make) they will IME fail inside a few years. It is your choice but I'd rather set up hubs correctly when they are new than deal with a load of stuff that is knackered a few years down the line....


I take your point about preventative maintenance. And thanks very much for your help with this.

With regard to the RHS of rear hub I can get a cone spanner on, no problem.

Image

But to get the oil or SFG (semi-fluid grease?) in, I don't see how I can get it past the cone.

Image

Here's an old Shimano freehub body that I took off about 20 years ago, and I can't see how I would lube it without taking off the rubber seal on the reverse side.

Image

Brucey
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Re: CX Wheel build and hub advice

Postby Brucey » 10 Jan 2018, 11:47pm

withdraw the axle 15mm (or remove it) and whack a load of gear oil into the hub, where the RH ball bearings usually sit. The hold the freehub body in your hand and spin the wheel so the freewheel mechanism is working. The gear oil will work its way into the freehub mechanism. You will hear the freewheel action go quieter; once that happens it is job done, more or less.

BTW you did well to get the cone spanner on the RHS like that. A lot of hubs won't allow that.

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reohn2
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Re: CX Wheel build and hub advice

Postby reohn2 » 11 Jan 2018, 12:20am

Brucey wrote:withdraw the axle 15mm (or remove it) and whack a load of gear oil into the hub, where the RH ball bearings usually sit. The hold the freehub body in your hand and spin the wheel so the freewheel mechanism is working. The gear oil will work its way into the freehub mechanism. You will hear the freewheel action go quieter; once that happens it is job done, more or less.

BTW you did well to get the cone spanner on the RHS like that. A lot of hubs won't allow that.

cheers

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LinusR
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Re: CX Wheel build and hub advice

Postby LinusR » 11 Jan 2018, 10:09am

Brucey wrote:withdraw the axle 15mm (or remove it) and whack a load of gear oil into the hub, where the RH ball bearings usually sit. The hold the freehub body in your hand and spin the wheel so the freewheel mechanism is working. The gear oil will work its way into the freehub mechanism. You will hear the freewheel action go quieter; once that happens it is job done, more or less.


OK, if I understand this correctly, the gear oil will pass around the outer edge of the bearing cup (there must be a gap around the edge) and work its way past the first set of freehub body bearings, then the pawls and springs, and finally towards the back ball bearing race behind the rubber seal. Then I pack some grease into both cups on the hub, adjust the hub from the LHS, tighten and I'm done.

Brucey
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Re: CX Wheel build and hub advice

Postby Brucey » 11 Jan 2018, 10:49am

yes that is it more or less. I'd add that if the seals are good in the hub, not only is gear oil OK in the freehub body, but a SFG can be used in the main hub bearings too, and is to be preferred because it keeps the seal lips wetted better than a typical #2 grease.

If you mix a quantity of your finish line Teflon grease about 50:50 with an EP90 gear oil, you usually (experiment with a small quantity first, why not) end up with a reasonable SFG. If this also migrates into the freehub body, it shouldn't foul the pawls so that they won't engage cleanly. There are better SFGs for this application, that contain more corrosion inhibitors for example, but these are usually only of very much benefit if you are riding on salted roads.

BTW if there is an excess of SFG in the hub, it will ooze out past the seals for the first few hundred miles, even if the seals are in good condition. With a disc hub this could lead to disc contamination unless it is wiped away. If this oozing is excessive or persistent it is a good idea to use a slightly thicker consistency of grease in the LH bearing.

Also note that if a #2 grease is used in the RH bearing, and no oil is added to the freehub body first, the gap between the freehub body and the RH bearing cup can, after a time, become fairly well blocked with dried grease. This can prevent the freehub body from receiving its usual (parsimonious) trickle of oil that gradually separates from a typical #2 grease; the result is that the rear seal on the freehub body runs dry, wears, then lets the water in, and the freehub body is doomed.

With many older models of freehub body, there is no rear seal. With these (or newer ones with worn seals) oil will run out of the back of the freehub body. In this case it is best to lubricate the hub/freehub body with an SFG. This can be forced into the freehub body using air pressure but in use it should work its way from the main part of the hub into the freehub body anyway.

cheers
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