RyanMcVicker Posted May 30, 2009 Report Share Posted May 30, 2009 Hello everyone, Curious as to what the proper spoke tension would be on a 26" wheel with tryall H hub, double butted sapim spokes, and tryall hole rim. On the Park Tool Tensiometer my spokes are at about 15-20 right now.. What is the best tension for the spokes to be at?Thanks Ryan Quote Link to comment Share on other sites More sharing options...
psycholist Posted May 30, 2009 Report Share Posted May 30, 2009 (edited) Just keep tightening the spokes - you won't break them. When you either can't turn the spoke key due to the spokes being too tight or the spoke nipples start to round then you've got the strongest wheel you can get. Unless your rim, spokes or hub is shite the spoke nipples rounding is the first point of failure tensioning a wheel. A target tension of 1000N is sometimes used for spokes too. To find the theoretical maximum tension the spoke can cary, go to www.matweb.com and look up the properties of the spoke material you're using (This is difficult because most spoke manufacturers won't tell you exactly what they use, but if you put 'drawn stainless steel' in as a asearch term you should be able to get a rough idea).Look up the yield stress on the material - the unit should be N/m^2 or N/mm^2 - If the unit is in Pascals (Pa) this is the same as N/m^2.Multiply this figure by the cross sectional area of the thinnest section of the spoke (The root of the threads on straight gauge spokes, the butted part on butted spokes) in the relevant unit (N/m^2 x m^2 = N or N/mm^2 x mm^2 = N) and you've got the maximum theoretical tension the spoke can carry. Built wheels are usually a fraction of this though thanks to the nipples rounding once you pass a certain tension (You can get around this by building the wheel in your frame and flexin the rim towards the flange the spoke you're tightening goes to as you tighten it), but you're hitting diminishing returns in terms of wheel strength once you go to that territory... Edited May 30, 2009 by psycholist Quote Link to comment Share on other sites More sharing options...
RyanMcVicker Posted May 30, 2009 Author Report Share Posted May 30, 2009 wow thanks for the info! I was just wondering what most people do? I don't know if a super tight wheel would be better or stronger than what i have right now. I can bend the spokes around but it's still pretty tight. Maybe i could get better power transfer with tighter spokes? (gap farther, etc...) Quote Link to comment Share on other sites More sharing options...
psycholist Posted May 30, 2009 Report Share Posted May 30, 2009 More tension in the spokes means more load is needed to pop the rim into a pringle shape if it's loaded sideways as well as more vertical load needed before the spoke pointing towards the ground loses tension. If a spoke goes slack it will start to loosen, so the more tension the longer the wheel will stay true (Bending the rim notwithstanding of course). Unless the wheel is very slack you're not really going to notice the difference in power transfer, though on a slack front wheel with a disk you'll see all the pushing spokes go slack under heavy braking. Quote Link to comment Share on other sites More sharing options...
RyanMcVicker Posted May 31, 2009 Author Report Share Posted May 31, 2009 Cool. So when i had heavy gauge spokes I would tension them hardcore and not care. Now i have double butted sapim spokes (from tarty) that are thinner, how do I know when to stop tensioning? Quote Link to comment Share on other sites More sharing options...
eskimo Posted May 31, 2009 Report Share Posted May 31, 2009 Your always in wheel threads. You need to do a wheel thread. Cool. So when i had heavy gauge spokes I would tension them hardcore and not care. Now i have double butted sapim spokes (from tarty) that are thinner, how do I know when to stop tensioning? Sounds like your worrying to much. You know what your doing so just gradually tension. I know mine are real tight on my stock. Though if you are using a thin rim too much tension might not be overly great. Quote Link to comment Share on other sites More sharing options...
RyanMcVicker Posted May 31, 2009 Author Report Share Posted May 31, 2009 Yeah, i just got the tryall hole rear rim... single wall. I haven't ridden on it yet so i just want to make sure it's okay, i don't want to taco it my first ride lol. Quote Link to comment Share on other sites More sharing options...
Fixed Pants™ Posted May 31, 2009 Report Share Posted May 31, 2009 Generally 25 is gonna be good, maybe up it to 30 but too much tension f**ks a wheel. They'll start pulling through the rim much quicker if you have too much tension, same with the hub, it'll rape it. Quote Link to comment Share on other sites More sharing options...
psycholist Posted May 31, 2009 Report Share Posted May 31, 2009 Cool. So when i had heavy gauge spokes I would tension them hardcore and not care. Now i have double butted sapim spokes (from tarty) that are thinner, how do I know when to stop tensioning?I build all my wheels (XC/trials/commuting etc.) with double butted spokes and the spoke nipples will round before the DB spokes will break too (Unless you go for something ridiculously lightweight - I'm talking about general DB mountain bike spokes). Double butted spokes build more durable wheels because they stretch more for a give spoke tension (Due to the middle having a smaller cross section), which means the rim can deform more before the spokes can go slack and progressively loosen. Trials wheels tend to fail from crashes and overload or the rim getting too thin to stay stiff from grinding, so the progressive loosening and fatigue failures you see in wheels with high mileage will be less of a worry, they'll just take longer to show up... This also means that just because you're replacing a worn out rim you don't usually need new spokes unless the spoke length is wrong. Quote Link to comment Share on other sites More sharing options...
Tomm Posted May 31, 2009 Report Share Posted May 31, 2009 I don't know anyone that uses a tensiometer for building wheels. Except for maybe Fatpants, but then he does have a Cytech level 1 mechanic certificate Seriously, just do them up nice and tight so it feels like all your other non-f**ked wheels. Quote Link to comment Share on other sites More sharing options...
mr kenny Posted June 1, 2009 Report Share Posted June 1, 2009 i will disagree with the tighten it till you cant turn the nipple.you need to find out what kind of spoke it is( double butted i know but what is the butt in the spoke? is it 2mm/1.5mm/2mm like the dt revolution meaning the spoke goes from 2mm at the end of the elbow to 1.5mm to 2mm at the threads. once you have determoined the thickness at the centre of your spoke then you referance it with the chart that you got woth the park tool.ideally you are looking to get a rim to be around 95 to 100 kg of pull from the spokes wich off the top of my head for the dt revolution like i described will be around 16 17 on your tension tool.when you stars going above that the rim is harder to true, and get the up and down adjusted.yeh make them super tight, that doesn't make a super strong wheel.kenny Quote Link to comment Share on other sites More sharing options...
Tristan Posted June 2, 2009 Report Share Posted June 2, 2009 Just keep tightening the spokes - you won't break them. When you either can't turn the spoke key due to the spokes being too tight or the spoke nipples start to round then you've got the strongest wheel you can get. Unless your rim, spokes or hub is shite the spoke nipples rounding is the first point of failure tensioning a wheel. A target tension of 1000N is sometimes used for spokes too.1000N is quite low for the 'tight' side of a wheel - you will still have the risk of spokes becoming slack at this tension. Using a normal trials hub with symetrical flanges both sides of the wheel should be tensioned to around 120N or 120Kgf (not quite the same but close)To find the theoretical maximum tension the spoke can cary, go to www.matweb.com and look up the properties of the spoke material you're using (This is difficult because most spoke manufacturers won't tell you exactly what they use, but if you put 'drawn stainless steel' in as a asearch term you should be able to get a rough idea).The theoretical max of the spokes doesn't come into effect - the rim is the limiting factor here.Look up the yield stress on the material - the unit should be N/m^2 or N/mm^2 - If the unit is in Pascals (Pa) this is the same as N/m^2.Multiply this figure by the cross sectional area of the thinnest section of the spoke (The root of the threads on straight gauge spokes, the butted part on butted spokes) in the relevant unit (N/m^2 x m^2 = N or N/mm^2 x mm^2 = N) and you've got the maximum theoretical tension the spoke can carry. Built wheels are usually a fraction of this though thanks to the nipples rounding once you pass a certain tension (You can get around this by building the wheel in your frame and flexin the rim towards the flange the spoke you're tightening goes to as you tighten it), but you're hitting diminishing returns in terms of wheel strength once you go to that territory...All stainless steels are around 201GPa tensile strength but this means nothing.More tension in the spokes means more load is needed to pop the rim into a pringle shape if it's loaded sideways as well as more vertical load needed before the spoke pointing towards the ground loses tension. If a spoke goes slack it will start to loosen, so the more tension the longer the wheel will stay true (Bending the rim notwithstanding of course). Unless the wheel is very slack you're not really going to notice the difference in power transfer, though on a slack front wheel with a disk you'll see all the pushing spokes go slack under heavy braking.If you keep applying spoke tension the rim it will eventually buckle. The spoke has no role in the max tension, nor does the spoke nipple as a correctly lubed nipple (no giggling please) will have no problems transmitting this tension to the rim. A normal light-weight mtb rim like a Mavic 719 will start buckling at 140 to 150Kgf, some deep section road rims will take more tension than this. Most trials rims are not especially stiff due to their shallow, box-section design and will start buckling at a reasonably low tension. This will be quite evident when building the rim because adding an extra 1/4 turn of tension will cause it to go quite badly out of true. Backing the nipples off 1/4 turn will usually return the wheel to true.Building wheels with the rim close to it's buckling tension is not usually considered a good thing. A decent side load will increase the spoke tension on one side of the rim pushing it over the buckling point and will cause more of an effect than the side load by itself.Aiming for 120Kgf is a good idea. Use the Park TM-1 to calculate what number this relates to on it's scale based on the diameter of the thin section of the spoke...the included steel gauge tester will help you find this out. Apply a good quality lube or antiseize to the spoke threads and apply a small amount of grease or oil to the shoulder of each nipple to allow nice easy (and quiet!) turning up to your desired tension. If you can end up with a wheel which is reasonably true (lets say +/- 0.5mm in both directions) and with spoke tensions within 10% of each other you should end up with a very strong, durable wheel.Cheers, Tristan Quote Link to comment Share on other sites More sharing options...
psycholist Posted June 2, 2009 Report Share Posted June 2, 2009 Building wheels with the rim close to it's buckling tension is not usually considered a good thing. A decent side load will increase the spoke tension on one side of the rim pushing it over the buckling point and will cause more of an effect than the side load by itself.I'll second this one - what I find though is that the spoke nipples will tend to round before you get to the buckling tension, so unless you've got a very weak rim, having the wheel pop into a buckled shape as you tension it won't really arise. This can be seen on the cheap ass wheels bike shops sell for £20 though if you want to do a cheap experiment ...1kgf is 9.81 Newtons - I mostly hate kgf as a unit because it's a side effect of people who have got used to the imperial unit system applying the faulty thinking that made that unit system a mess to work with to the already consistent SI unit system ...I've never measured the tension in spokes in a wheel I've built, but I've ridden the same wheels on one bike for XC/DH/Touring/Street for 6 years now and had no issues until one spoke failed in each wheel a couple of months ago - the spokes both failed at the root of the nipple threads rather than at the bend too, indicating that the wheel was stress relieved properly too. I can't remember the last time I even looked at the wheels to true or tension them either, but they were D521's . Quote Link to comment Share on other sites More sharing options...
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