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Spoke tension for Exal XR2 rims?

Posted: 18 Oct 2017, 12:37pm
by Samuel D
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.

Re: Spoke tension for Exal XR2 rims?

Posted: 18 Oct 2017, 12:58pm
by Brucey
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

Re: Spoke tension for Exal XR2 rims?

Posted: 18 Oct 2017, 1:23pm
by Samuel D
Thanks! I’ll report back with the measured values.

Re: Spoke tension for Exal XR2 rims?

Posted: 19 Oct 2017, 8:23am
by Samuel D
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.

Re: Spoke tension for Exal XR2 rims?

Posted: 19 Oct 2017, 9:28am
by PhilD28
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.

Re: Spoke tension for Exal XR2 rims?

Posted: 19 Oct 2017, 10:03am
by Brucey
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

Re: Spoke tension for Exal XR2 rims?

Posted: 19 Oct 2017, 10:45am
by PhilD28
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 .

Re: Spoke tension for Exal XR2 rims?

Posted: 20 Oct 2017, 11:05pm
by Samuel D
Thanks very much, Brucey and PhilD28. I’ve left the wheel alone. Have to say I’m pretty pleased with how it turned out.