spoke tension for 26" Sputnik rims

For discussions about bikes and equipment.
mercalia
Posts: 14630
Joined: 22 Sep 2013, 10:03pm
Location: london South

spoke tension for 26" Sputnik rims

Post by mercalia »

spoke tension for 26" Sputnik rims, rear mainly. 36 spokes 8 speed

I thought I would try my hand at building a rear wheel from the broken one I have that uses an old Mavic X138 rim, but using Sputnik rims.

I have looked on the Ryde website and downloaded their catalog and cant find any reference to max spoke tensions

any one know where to look? I suppose tension will vary re which side and also spoke diameter used ?
Last edited by mercalia on 5 Aug 2015, 12:34pm, edited 2 times in total.
User avatar
jamesbradbury
Posts: 67
Joined: 7 Nov 2014, 4:58pm
Contact:

Re: spoke tension for 26" Sputnik rims

Post by jamesbradbury »

Based on what I've read in Roger Musson's wheel building book, I don't think there's a strictly defined tension. What seems to be important is that they're all of very similar tension and that you fix any twist.

I rebuilt a tandem wheel with help from his book, without a tension gauge. We had no problems or noises from the wheel on a 200km ride.
phil parker
Posts: 1033
Joined: 31 Dec 2009, 5:09pm
Location: Hants/Wilts

Re: spoke tension for 26" Sputnik rims

Post by phil parker »

The benchmark rule is an average tension over all of the spokes of 1000 Newtons.

I have had instance to contact Sapim in the past who informed me for on particular wheel build that I could easily go up to 1400 Newtons drive side.

If you have a tensiometer, I would start of with 1000 Newtons on the drive side, which will probably return you with about 700 N on the non-drive side and go upwards from there until you are happy with the tension. Using a conversion chart for spoke type & gauge to the same measurement whether it be lbs. Kgs or Newtons.
User avatar
NUKe
Posts: 4161
Joined: 23 Apr 2007, 11:07pm
Location: Suffolk

Re: spoke tension for 26" Sputnik rims

Post by NUKe »

Spoke tension is function of the spokes not the rims. Also for the rear the driver side will be tighter than the non driveside by about 20% . If you have tensiometer then it should have a guage and a table with it by knowing the spoke length and diameter you get the deflection reading , getting the wheel round and then true are much more important.

Colin is the real expert and knows the Rigida rims as well from his days as the wheel builder for Spa I am sure he will be along soon
NUKe
_____________________________________
Brucey
Posts: 44521
Joined: 4 Jan 2012, 6:25pm

Re: spoke tension for 26" Sputnik rims

Post by Brucey »

the limiting tension for spokes is usually set by the rim not the spokes in most builds.

Excess tension will either

a) cause the rim to collapse via Euler buckling (for less stiff rims, most modern rims are not like this) or

b) will be so high that in service, the rim will fail at the spoke holes e.g. via Stress Corrosion Cracking (SCC)

The tension differential on the rear wheel will vary with the hub width and overall dish on the wheel. IIRC Colin may have mentioned going as high as 130kgf with sputniks, but he will be able to confirm or refute this I am sure.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
mercalia
Posts: 14630
Joined: 22 Sep 2013, 10:03pm
Location: london South

Re: spoke tension for 26" Sputnik rims

Post by mercalia »

well thats a bit worrying. I just got one of the Park Tool TM-1 guages and tested it on a few wheels I have - the old rear Mavic X138 and the new Spa Sputnik rear. The gauge seems plausible in that the old Mavic that broke has deflections of 24 ds ( 120 kgf) and inconsistant 20 on nds( = 70 kgf) ( all over the place -/-2)

The Spa has deflections about 22 nds and 29/30 on ds and very consistent results so intentional The ds isnt on the table. I do weigh 16 stone and said would carry a heavy load when I ordered it. The builder did phone me up at the time and said that the silver rims couldnt take the tension, had tried a few so suggested I go for the black ones he knew to be good. The spokes are Sapim Strong on ds and double butted 2mm on nds. It is the standard rear wheel they make.

deflections - 22 nds = 85 kgf and 29 ds = 200 kgs!!!!?

Wheels are on my dawes 1-Down 26". Things havent broken yet. and all seems ok. And the wheel has taken a bashing over the last 8 months or so

wish I hadnt got the guage now, igorance is bliss :?
User avatar
531colin
Posts: 16083
Joined: 4 Dec 2009, 6:56pm
Location: North Yorkshire

Re: spoke tension for 26" Sputnik rims

Post by 531colin »

Driveside 120kgf....NDS 80kgf.

the Sapim "strong" DS spokes are 2mm centre section, the NDS Sapim Race spokes are 1.8mm centre section, so you have to use a different column of the Park tool table to translate from deflection to kgf.............. the deflections should read 25 DS, 19 NDS.
(and 21 front for 100kgf on 1.8mm DB spokes)

I have seen Park gauges read wrong out of the box
mercalia
Posts: 14630
Joined: 22 Sep 2013, 10:03pm
Location: london South

Re: spoke tension for 26" Sputnik rims

Post by mercalia »

531colin wrote:Driveside 120kgf....NDS 80kgf.

the Sapim "strong" DS spokes are 2mm centre section, the NDS Sapim Race spokes are 1.8mm centre section, so you have to use a different column of the Park tool table to translate from deflection to kgf.............. the deflections should read 25 DS, 19 NDS.
(and 21 front for 100kgf on 1.8mm DB spokes)

I have seen Park gauges read wrong out of the box



the 120/80 is what i thought from a previous post u made. I did read the 2mm one

The front deflection I get is 22-23 mostly 23 - that another spa wheel I got recenly not at same time as the rear. So guage could be accurate? so what to make of the rear wheel with a ds deflection of 29?
gregoryoftours
Posts: 2234
Joined: 22 May 2011, 7:14pm

Re: spoke tension for 26" Sputnik rims

Post by gregoryoftours »

531colin wrote:
I have seen Park gauges read wrong out of the box


Is this a common thing, and could lubricating the pivots/springs of the tool help at all? The choice of spoke tension meters is pretty limited at the cheaper end, I'm thinking of buying one of these, but do you think they are reliable/accurate enough to be worth using?
Pneumant
Posts: 278
Joined: 7 Oct 2010, 8:25pm

Re: spoke tension for 26" Sputnik rims

Post by Pneumant »

mercalia wrote:spoke tension for 26" Sputnik rims, rear mainly. 36 spokes 8 speed

I thought I would try my hand at building a rear wheel from the broken one I have that uses an old Mavic X138 rim, but using Sputnik rims.

I have looked on the Ryde website and downloaded their catalog and cant find any reference to max spoke tensions

any one know where to look? I suppose tension will vary re which side and also spoke diameter used ?


I have built up 36h Sputnik 26" rims with XT 8-speed hubs. They are such strong rims that you would probably strip the spoke threads before the rim pringled. So keep the tension on the high-side, I always pluck the spoke to assess tension. My ears are my tension meter!
phil parker
Posts: 1033
Joined: 31 Dec 2009, 5:09pm
Location: Hants/Wilts

Re: spoke tension for 26" Sputnik rims

Post by phil parker »

I started off with a Park gauge, after many years of building without a gauge, before I moved on to a DT Swiss gauge. I checked the calibration in comparison and it wasn't too far out, but much more difficult to use and interpret. For me the additional cost of the DT Swiss (second hand) was a worth while investment.
Brucey
Posts: 44521
Joined: 4 Jan 2012, 6:25pm

Re: spoke tension for 26" Sputnik rims

Post by Brucey »

IIRC all these gauges have a similar flaw in that the calibration assumes that the part of the spoke in the gauge length is

a) straight and
b) is able to bend elastically and
c) is not constrained at the ends in any way

In a 26" x3 rear wheel, the spokes have an exposed length that isn't much longer than the minimum for the tool to be used, and IIRC a sputnik rim leaves a small set in the nipples. It may be that the readings are not perfectly accurate because of these things. I'd certainly try the gauge twice on the same length of spoke (from opposite sides) before assuming that a spoke was straight.

You can easily check the calibration of the meter by constructing a lever assembly with a spoke in it, such that it multiplies an available dead weight (eg your body weight) to near the spoke tension you intend to use. You can knock something up to do this out of scrap lengths of 4x2 timber and a few other odds and ends.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
User avatar
531colin
Posts: 16083
Joined: 4 Dec 2009, 6:56pm
Location: North Yorkshire

Re: spoke tension for 26" Sputnik rims

Post by 531colin »

Just considering the Spa wheels, where i think i know what spokes they will have used....
front...22/23 is 111/124 kgf on a 1.8mm spoke. ...possible, but damned tight.
Rear....22 nds is 111kgf on a 1.8mm spoke....again, possible, but damned tight
29/30 ds is 200/225 kgf (its off the chart, I'm extrapolating!)..on a 2mm spoke....frankly, I doubt its possible to get a spoke as tight as this....at DS 130/140kgf my hands are screaming, and i'm wearing safety glasses because a spoke that breaks under that sort of tension shoots out from the rim like a crossbow bolt, and they let go with a crack like a pistol shot.
also rear wheels are correctly dished at 120/80kgf, ie the DS spokes are at 1.5 times the tension of the NDS.
Your wheel the DS are twice as tight as the NDS

your Mavic rear has 24 DS which is 107kgf for a 2mm spoke or 138kgf for a 1.8mm
NDS is 20 which is 68kgf for a 2mm or 89kgf for 1.8mm

Can't make much sense of it, I'm afraid.
User avatar
531colin
Posts: 16083
Joined: 4 Dec 2009, 6:56pm
Location: North Yorkshire

Re: spoke tension for 26" Sputnik rims

Post by 531colin »

gregoryoftours wrote:..........
Is this a common thing, and could lubricating the pivots/springs of the tool help at all? The choice of spoke tension meters is pretty limited at the cheaper end, I'm thinking of buying one of these, but do you think they are reliable/accurate enough to be worth using?


Thats a very open question.
I suppose I have built wheels on and off for half a century, maybe longer. Its only in the last 6 or 8 years i have used a tension gauge, but i now prefer to use one than not to use one.
If you are just building the odd wheel for yourself, there is much less pressure....if your NDS spokes slacken off, you can simply crank up the tension a bit. Its seriously unlikely that you would build a wheel too tight, unless you have some very fragile rims.
If you are posting wheels out all over the country then its a real pain if they go wrong, so the stakes are much higher.
If you work somewhere there are several wheelbuilders and years of "herd experience" building wheels, you can easily spot random events like duff tension gauges, duff batches of spokes and rims, etc.
If you are on your own, you arguably have more need of an accurate gauge, but are much less likely to be able to judge whether any one gauge is accurate, so i think there is room for something like Brucey's suggestion of hanging a weight on a spoke and actually checking the gauge.
User avatar
531colin
Posts: 16083
Joined: 4 Dec 2009, 6:56pm
Location: North Yorkshire

Re: spoke tension for 26" Sputnik rims

Post by 531colin »

somewhere on these pages there is some stuff from CJ about tensioning by tone.
As I recall CJ has reasonable pitch (I'm tone deaf) and found (an app.?) that gave pure single pitches, that let him derive the tension.....again, CJ can do the maths, I
can't.......

EDIT....found it.....Google works really well to search here, if you put "CTC" into the Google search... http://forum.ctc.org.uk/viewtopic.php?f=5&t=48694&start=15

More here.....http://forum.ctc.org.uk/viewtopic.php?f=5&t=72718&start=15

Old man whingeing mode "on".....
Seems to me this Forum was a different place back then, with proper discussion, and an absence of people slagging each other off in interminable wrangles about the merits or otherwise of the latest spangly bits..........mode "off", but may return...
Post Reply