Spoke tension for Exal XR2 rims?

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Samuel D
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Joined: 8 Mar 2015, 11:05pm
Location: Paris

Spoke tension for Exal XR2 rims?

Postby Samuel D » 18 Oct 2017, 12:37pm

I’ll imminently have access to a tensiometer, which will allow me to check the tension in a front wheel I built a few months ago. I didn’t find any Exal documentation. What sort of figure should I aim at?

Specs are: silver Exal XR2 rim, Shimano 105 hub, 32 Alpina 2.0/1.7/2.0 mm swaged spokes, 3-cross.

I may not bother adjusting anything if it’s approximately correct and on the low side, since I’m light at 65-odd kg.

Brucey
Posts: 26897
Joined: 4 Jan 2012, 6:25pm

Re: Spoke tension for Exal XR2 rims?

Postby Brucey » 18 Oct 2017, 12:58pm

few rims have a tension limit that is much less than 95kg, and few rims have a tension limit that is much more than 130kg. I don't have the figures to hand, but for a 32 spoke front wheel, anything over 80kg (with DB spokes) is likely to be enough for light duty, and 100kg would be enough for the heaviest duty that that rim is likely to withstand.

If a wheel sees hard duty with insufficient spoke tension, it will usually let you know by the nipples starting to unscrew themselves. I have rarely seen this in any front wheel.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Samuel D
Posts: 1792
Joined: 8 Mar 2015, 11:05pm
Location: Paris

Re: Spoke tension for Exal XR2 rims?

Postby Samuel D » 18 Oct 2017, 1:23pm

Thanks! I’ll report back with the measured values.

Samuel D
Posts: 1792
Joined: 8 Mar 2015, 11:05pm
Location: Paris

Re: Spoke tension for Exal XR2 rims?

Postby Samuel D » 19 Oct 2017, 8:23am

Tensions are closely clustered (as I could tell from plucking spokes anyway) and seem to average just a hair over 100 kgf. Fairly high, then.

I think I’ll leave them unless Brucey or someone else strongly disagrees.

PhilD28
Posts: 51
Joined: 26 Sep 2016, 8:31am

Re: Spoke tension for Exal XR2 rims?

Postby PhilD28 » 19 Oct 2017, 9:28am

If I were building up with those rims (which I have done) and in the absence of manufacturers rim data, 100kgf would be what I would shoot for on the front. The ones I built, at a tad under 100kgf, are still running true after about 3 years on a friends bike.

These days many rim sections are so much stronger than 30 years ago, built tensions have more leeway.

Brucey
Posts: 26897
Joined: 4 Jan 2012, 6:25pm

Re: Spoke tension for Exal XR2 rims?

Postby Brucey » 19 Oct 2017, 10:03am

that seems just fine to me.

BTW if you were building with thicker/PG spokes a tension nearer 100kgf would IMHO be more or less mandatory; at lower tensions such spokes (which have less 'stretch' in them) are more likely to become momentarily slack and this risks the nipples backing out unless they are threadlocked.

FWIW I think that with many dished rear wheels, the manufacturer's tension limit is unlikely to be respected on the DS; if it is, NDS spokes seem very slack to me. I think it is more commonly the case that DS spokes are made tight (much tighter than front wheels are, typically) and that NDS spokes are brought up to a tension value that is more likely to be enough to prevent the nipples from backing out. This risks the rim cracking on the DS, which IME is not at all uncommon these days. Riding in the wintertime (with salt spray) seems to help this along nicely.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

PhilD28
Posts: 51
Joined: 26 Sep 2016, 8:31am

Re: Spoke tension for Exal XR2 rims?

Postby PhilD28 » 19 Oct 2017, 10:45am

Agreed, high tension on DS, particularly with Mavic mtb rims seems to often result in cracking around the eylets after a few winters. I've never had that problem with Exal LX 17 which I've used for a few years since I ditched Mavic even at 120 +kgf .

Samuel D
Posts: 1792
Joined: 8 Mar 2015, 11:05pm
Location: Paris

Re: Spoke tension for Exal XR2 rims?

Postby Samuel D » 20 Oct 2017, 11:05pm

Thanks very much, Brucey and PhilD28. I’ve left the wheel alone. Have to say I’m pretty pleased with how it turned out.