CX Wheel build and hub advice

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LinusR
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Re: CX Wheel build and hub advice

Postby LinusR » 14 Jan 2018, 4:22pm

Gattonero wrote:
LinusR wrote:...
Rear wheel after building but before truing:...


One word of advice: on DB spokes is always a good idea to tap the spoke in the portion that leaves the flange.
This will make the spoke to follow the direction right towards the nipple from its very start at the flange: this is the butted portion and will keep at 90º while the flex will be in the thinned section. You don't want this, as with time the butted section will give up and make the spoke to loose tension.
This is easy to spot when the hub flange has a certain distance from the middle, like on the rear Lh side, and has to get a more shallow angle to the spoke; the rear Rh side for example is often on a more steep angle, due to the flange been closer to the middle of the hub, and this effect is less noticeable


I have a plastic mallet for such purposes. Jobst recommends doing this, and even bending slightly the other butted end (near nipple) so that it exits toward the hub in a straight line. I usually try to press both ends of the spoke with my thumb to get it aligned but I resort to a gentle tap with the mallet for the hub end and pliers near the nipple. I tend to do it rather conservatively and just coax it into position.

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LinusR
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Re: CX Wheel build and hub advice

Postby LinusR » 14 Jan 2018, 4:23pm

Brucey wrote:I'm not sure it makes a lot of difference, provided the wheel is properly built and the wheel is properly stress-relieved.


I was hoping you were going to say that... :wink:

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LinusR
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Re: CX Wheel build and hub advice

Postby LinusR » 14 Jan 2018, 11:02pm

Well that was interesting... Trued both wheels and full of enthusiasm decided to go for a dry run (without Stans sealant) and fit my cheapo Schwalbe Smart Sam (addix compound) 700x35 wired tyre which is supposed to be "tubeless ready" according to Acycles. https://www.acycles.co.uk/schwalbe-smart-sam-liteskin-tubeless-ready-folding-tyre-700x35c.html

So... rim cleaned with surgical spirit, 25mm wide strip of gaffer tape installed, Mavic UST valve installed, tyre on (easy with fingers), lots of soapy water around the rim, valve core out, and finally Joe Blow track pump connected ready to pump away at VO2 Max.

Ping, bang, pop... it inflates up to 40psi with hardly any effort. Bubbles everywhere but it's holding air quite well considering there's no sealant. Must be beginners luck.

Let's try the other wheel and an older Schwalble Smart Sam (Performance and wired bead). Nothing. Zilch. Let's try a Schwalbe Sammy Slick (Performance folding) tyre. This time it takes a bit more effort, but I get 40psi in there and it holds air almost as good as the Smart Sam.

Image

Tomorrow I'll try some more tyres. Wish me luck :D

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NATURAL ANKLING
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Re: CX Wheel build and hub advice

Postby NATURAL ANKLING » 15 Jan 2018, 1:03am

Hi,
Used tubeless tyres are incredibly difficult to inflate, by hand or foot pump.
on cars and motorcycles there is a knack of dropping the assembly firmly on to the ground, holding all the time, upright, and turning periodically, helps nudge bead onto rim and then sealed, air is compressed by squashing the tyre and further promotes seating.
This does not always help.
I would not try this on bicycle tyres, there is not enough bulk in tyre and they are too soft.

Second method is to tie a tourniquet around the circumference of tyre and tighten the tyre onto the rim.
Even with an air line it can be difficult.

New tyres are a doodle.
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LinusR
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Re: CX Wheel build and hub advice

Postby LinusR » 15 Jan 2018, 6:16pm

NATURAL ANKLING wrote:Hi,
Used tubeless tyres are incredibly difficult to inflate, by hand or foot pump.


That may be why the older tyres didn't pop onto the rim - failed with both an older Smart Sam and a (2001) Schwalbe Marathon XR folding tyre. Although of course neither are tubeless tyres.

I managed to get a new 28mm Schwalble Durano folding tyre to pop onto the rim but it leaked air from somewhere. But then I failed to get the second tubeless ready Smart Sam to hold air, too. After several attempts I realised that the tape I used wasn't tough enough. So I went out and bought some Gorilla Tape for a builders' shop and that did the trick. Tyre popped on and held air straight away.

Mavic recommends tape no thicker than 0.2mm but the Gorilla tape is twice that thickness at 0.4mm. The gaffer tape I used in the first wheel (and my first attempt on the second wheel) is very thin at 0.125mm thick. No wonder it leaked air. I may have to redo the first wheel as it could fail. Tape recommendations please.

However, one serious problem I came across when swapping all these tyres on and off is this: on the new Mavic UST rims, once the tyre is "popped" onto the rim it is held there very tight and when I tried to get it off to redo the rim tape it was extremely hard to do. After failing with a plastic tyre lever I had to resort to, very gently, putting a flat blade screwdriver between the rim and the tyre bead to push it over the "hump" to pop it into the central channel of the rim. (See the picture below). I wouldn't want to attempt this in the woods or at the side of a road.

Image

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NATURAL ANKLING
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Re: CX Wheel build and hub advice

Postby NATURAL ANKLING » 15 Jan 2018, 8:23pm

Hi,
Bead Breaker Tool.

There will be a purpose tool for that job. :?:
Cant find one...............

Basically..............bits of wood / plastic .......vise....................g clamp etc.

https://www.ebay.co.uk/itm/Park-Tool-PT ... Sw9KhZ5m1D
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LinusR
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Re: CX Wheel build and hub advice

Postby LinusR » 15 Jan 2018, 9:13pm

NATURAL ANKLING wrote:Hi,
Bead Breaker Tool.

There will be a purpose tool for that job. :?:
Cant find one...............

Basically..............bits of wood / plastic .......vise....................g clamp etc.

https://www.ebay.co.uk/itm/Park-Tool-PT ... Sw9KhZ5m1D


Ha - I don't think it will fit in my seat pack. But I could file down the end of a plastic tyre lever to resemble the shape of a flat screwdriver to prise it off, and that would fit in my seatpack :wink:

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NATURAL ANKLING
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Re: CX Wheel build and hub advice

Postby NATURAL ANKLING » 15 Jan 2018, 10:01pm

Hi,
Correct size one of these -
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Gattonero
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Re: CX Wheel build and hub advice

Postby Gattonero » 21 Jan 2018, 10:34am

LinusR wrote:...
However, one serious problem I came across when swapping all these tyres on and off is this: on the new Mavic UST rims, once the tyre is "popped" onto the rim it is held there very tight and when I tried to get it off to redo the rim tape it was extremely hard to do. After failing with a plastic tyre lever I had to resort to, very gently, putting a flat blade screwdriver between the rim and the tyre bead to push it over the "hump" to pop it into the central channel of the rim. (See the picture below). I wouldn't want to attempt this in the woods or at the side of a road.

Image


The trick is to PULL from the opposite side, deflate the tyre as much as possible and grab it pulling opposite the side you want to release. Once the seal is broken on a short section, then it's easy!
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LinusR
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Re: CX Wheel build and hub advice

Postby LinusR » 23 Jan 2018, 10:23pm

Gattonero wrote:The trick is to PULL from the opposite side, deflate the tyre as much as possible and grab it pulling opposite the side you want to release. Once the seal is broken on a short section, then it's easy!


I'll try that. But I'm pretty sure I'll need to coax it off with a modified lever or gently with a flat blade screwdriver on my Swiss army knife. Myabe it will loosen over time.

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LinusR
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Re: CX Wheel build and hub advice

Postby LinusR » 23 Jan 2018, 11:30pm

This is the final tally for the wheels

Mavic XC 621 £44 (These are cross-country 29er MTB rims and the max recommended pressure is 45psi or 3 BAR)
Mavic XC 621 £44
XT M756A rear hub £40
XT M756 front hub £30
Rotor 6 bolt £18 (nominal price, I actually had these spare)
Rotor 6 bolt £18
ACI Alpin DB spokes £45 (cost of 144 spokes)
Mavic UST valves £18
Schwalbe Tyres £40 (Smart Sam wired liteskin 700x35)

Total £297

Preparation, build and observations

I calculated the spoke lengths by using this online calculator http://www.prowheelbuilder.com/spokelengthcalculator/ which gave me sizes of 287mm and 288mm for 32 spokes laced three cross. I opted to use 288 for all the spokes. On completion of the build this actually left a couple of threads showing (outside the nipple) on the LHS of the rear wheel and the RHS of the front wheel. So the calculation is slightly short for the longer sides and less threads than optimal are engaged in the nipples. I used the 12mm nipples that came with the spokes. Mavic however recommends 14mm spokes with these rims and this would have hidden the shortfall but of course masked the lack of thread engagement. (I believe the internal thread length is the same for both 12mm and 14mm nipples.) I didn't use threadlock or any lubricant on the threads, only some gear oil around the eyelets when truing. Because they are single eyelet I dropped the occasional nipple into the cavity of the rim when building, which was a bit of a fiddle to get out. I resorted to inserting the nipples with a spare spoke.

I disassembled the hub bearings and added some gear oil to the freehub side to lubricate the freehub body. I also packed in more grease to both sides of front and rear hubs. I then adjusted the hubs allowing for slight play until the quick-release lever was tightened. (As advised by Brucey earlier in this thread.) The reason being that Shimano do not put sufficient grease or oil in the hubs and they are usually adjusted too tight. While there was a fair bit of grease in the bearings there could have been more so this advice was good. The freehub body benefited from extra gear oil. Bearing adjustment is certainly required. I used Finish Line teflon grease and EP90 gear oil bought from a motor spares shop (1 litre costs about £6. I decanted some to a small bike lube bottle. I can share the rest with my club mates for the rest of my life). I'm a bit concerned about the lack of any real seal on the LHS of the rear hub. Previous models have had a chunky rubber outer seal which the front hubs have. I may try to get a spare to try to fit on the rear.

The rims are Mavic UST tubeless but I was using cheap Schwalbe cyclocross tyres with a wire bead. According to the retailer are tubeless ready, though this is not mentioned by Schwalbe and it is not marked on the side of the tyre. They are the new Addix compound variety and the tread and sidewall is slightly different to the older version. I used Gorilla tape on the rims and getting the tyres on was easy, and seating them was possible with an ordinary track pump. I used Stans as sealant. As mentioned above they are very difficult to get off once they are popped onto the rim.

Thanks to everyone for your help and suggestions.

Image

Image

Brucey
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Re: CX Wheel build and hub advice

Postby Brucey » 24 Jan 2018, 1:39am

that spoke length calculator gave very similar answers to most others when I tested it recently

https://forum.cyclinguk.org/viewtopic.php?f=5&t=118702&start=30

so if you came up with spoke lengths that are short, the most likely explanation is that a measurement (most likely the ERD value) entered was not correct. Mavic quote an ERD value but IME it is really a NSD value, and will generate spoke lengths that are at least 1.5mm too short unless corrected.

It is always a good idea to measure the rim ERD yourself; manufacturers quote numbers that are (in various ways) wrong or misleading, and in the past they have made rims that vary slightly in size from one batch to another anyway. Whether this will carry on in this, ahem, 'glorious age of tubeless rims' remains to be seen.

cheers
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