DOS

I have been building wheels for only about a year and to date have done tension by feel; figuring that if I screwed up terribly, I would soon find out when spokes started breaking. So far I have had no problems but I finally broke down and bought me a Park tensiometer.

In checking tension on a rear wheel I just built but haven't ridden, it seems I have over tightened the spokes based on recommended values I have seen on BF and elsewhere, but I thought I'd run this by the crowd before dialing down the tension. Here are the values I came up with with the tensiometer -- Mavic Open Pro 32H 3x, double butted 2/1.7/2

Deflection readings on drive side -- 9 spokes read 23, 5 spokes come out at 24, and 2 at 23.5, for an average deflection of about 23.375 (its a new rim and the wheel is true in all directions).

Using the Park took chart, that amount of average deflection comes out to an average tension of about 139KgF.

I have seen recommended tension for open pros as between 100 to 120 kgf (although I gather Mavic recommends even lower).

Should I decrease tension? Also, how should I factor spoke count into tension calculations (i.e. should I go higher for this 32h wheel than I would for 36h)?

cachehiker

I've only built a dozen or so wheels but I probably would've stopped at about 120Kgf. My 32h Open Pro's are tensioned to about 115Kgf drive side rear and about 105Kgf on the front. I only weigh 150 lbs. but I've beat the living tar out of them and they're still true.

Anyhow, on an perfectly evenly tensioned wheel it's usually the spoke bed that gives it up and not a spoke. Gerd Schraner states somewhere in his book that good spokes can typically take up to 200Kgf. For that reason I usually look for the minimum spoke count the rim is commercially available for. If it's an old 36 spoke single wall rim, I stop at something less than 100Kgf. 32 hole double wall at 36/32*100 or 113Kgf, 28 hole double wall at 36/28*129Kgf, etc.

I think 129Kgf would be the start of the danger zone with Open Pros but I'd like to hear other people's opinions myself.

DOS

Yeah, I figured I was too high. I did the tensioning a couple of weeks ago before getting the tensiometer. I will dial back a bit.

sharkey00

I would stick with what mavic recommends. There should be a chart somewhere with the values for each wheel based on spoke holes and spoke used. I use Dt swiss stuff so that info is different. With too high of spoke tension you will probably prematurely blow out an eyelet. Just back everything about a turn or 2 and you should be good to go.

operator

Yes, 140 average is too high. Shoot for around 110-120 for rear drive side. Especially for a wheel that you describe with such a ridicously high spoke count.

interested

I think my Mavic CXP33 wheelsets are around 135 kg, never had a problem with that. Both the CXP and the Open Pro rims are made by better than average aluminum. Still, unless you do loaded touring like I do, there is little benefit in such a high tension and some risk of cracks at the eyelets, so backing off a 1/2 turn and measure the spoke tension again probably is a good idea. I wouldn't worry about spoke tension in the 120-130 kgf range with that rim, even spoke tension is more important.

Regarding Mavic's and others generic spoke tension advice, then I would stress that these are generic values. Eg. Mavic has the same recommendation (90-110kgf) for all their rims, regardless how many spoke holes or how strong the rim is. IMHO, the needed spoke tension depends on wheel configuration and use. Heavy riders, tourers, and those people who just are plain harder than on the equipment than their peers may benefit from higher than average spoke tension.

--
Regards

well biked

I built similar wheels to the OP recently, 32 spoke with Mavic Open Pros, DT 2.0/1.8/2.0 spokes, the average rear driveside tension is 118kgf I believe. I've ridden the heck out of those wheels so far, and they are still perfectly true and round, no touch ups necessary. I weigh nearly 190 lbs FWIW. I talked to Mavic tech support a few months ago and they said around 110kgf is good on all the rims I asked about.

DOS

Well after much tinkering, spoke tension is down but perhaps too much. I am a bit concerned about variance and am beginning to regret my purchase of a tensiometer; having been blissfully riding around on true wheels unencumbered by concerns about tension.

I did a quick check on one 36h 2.0/1.8/2.0) wheel I built and values seemd much more consistent and properly tensioned than the 32h 2.0/1.7/2,0 wheel i am working with. Perhaps the lower spoke count plus more flexy 1.7mm spoke is trickier, its a theory.

Anyway, I read somewhere that between 10 and 20 percent variance from target is ok but I don't know how true that is. At the moment my average tension is around 105 with a low of around 90 (1 spoke) and a high of about 122 (2 spokes). With an average of 105, it would appear my low and high are within the 20 percent of the average. I will say that my deflection numbers, and thefore my individual spoke tensions, are somwhat scattered, ranging from a low of about 19 and a high of 22, with the greatest number at 21 and 22 (each with 5 spokes each). Theses deflections average out to 20.5 or so, which the park table equates to an average spoke tension of ~105kgf. My specific tensions are:

2 spokes@ ~ 90
1 spoke @ ~ 94
5 spokes@ ~ 98
5 spokes@ ~ 109
1 spoke @ ~ 116
2 spokes @ ~ 122.

Since I have a couple spots at 122, I am a bit hesitant to increase the tension anymore to get the average up over 110kgf. Should I continue my tinkering in an effort to get my tensions more even and my average up a bit more?

davidad

Mavic reccomends a max of 110kg. I built up a set a few years ago and the back began cracking around the eyelets. Because of this I went to an Open Sport (more Aluminium) and kept the tension at 110 on the drive side.

DOS

"Mavic reccomends a max of 110kg."

Mavic seems to recommend 90-100 for all its rims but I am still confused. Does that range mean one should shoot for an average tension of between 90 and 110 or should one strive to have each individual spoke tensioned somewhere north of 90 but less than 110 (which would by definition give an average of between 90 and 110 but at variance lower than I currently have of probably <10%). With ranges I have, I am okay on average tension since I am within the 90-110 average, and my variances from my average are maximum of about 15% (so within the 20% range I have seen referenced inother threads on this site). However, I have max tension on three spokes above the 110 number (116 in one case, 122 in two). If the Mavic recommendation regards individual spokes, it would seem I need to lower tension on three spokes and tweak tension around the rim to get more even tension, no? In short, do I keep working or am I in danger of letting the prefect being enemy of the good?

well biked

When I talked to the their tech dept., we talked about maximum tension, and he said to shoot for 105-110 on the rear driveside spokes. I took that to mean they don't officially recommend any spoke being tensioned higher than 110 kgf, but I could be wrong. Most of what I've read on the subject says that's a little low. On my above mentioned wheelset, I was able to get the spokes so evenly tensioned there's not much variation at all. I think that's the biggest key for a reliable wheel: even tension. For me, the key to achieving even tension is to not get too far ahead of myself regarding radial truing, lateral truing, or dish. Work in small increments and "refine" the wheel as you build it. That way, nothing gets too far out of whack.

In regard to average tension, have you seen the bit in the TM-1 instructions about how to figure this, what's considered acceptable, etc.?

DOS

Wll Biked

Thanks for the input

I did read the TM-1 instructions, thats where I got the 20% number. My tension ranges are well within the 20% TM-1 recommends (I am somehwere around 15%). I think I will keep playing a bit to see if I can get range below 10%. Your advice about small increments in well taken; one of my weaknesses as a wheel builder/truer is lack of patience.

DOS

Cahcehikere Said:

"I've only built a dozen or so wheels but I probably would've stopped at about 120Kgf. My 32h Open Pro's are tensioned to about 115Kgf"

Well Biked said

"built similar wheels to the OP recently, 32 spoke with Mavic Open Pros, DT 2.0/1.8/2.0 spokes, the average rear driveside tension is 118kgf I believe" and "Mavic recoomends 110kgf ... Most of what I've read on the subject says that's a little low."

After much more tinkering, I am now at about 117.5KgF with a variance of about 7% on the low side and about 4% on the high side. I played around with gong a bit lower on the tension, but everytime I did, I seemed to end up larger variances. At my state of development as a wheel builder, I am gonna call this wheel done. Thanks for all the advice.

operator

You'll never get perfectly even spoke tension. And also the TM-1 is as accurate as a shotgun at a kilometre. In other words even out the relative tension as much as you can and don't get so hung up on minor variations that don't mean anything.

The most durable wheel is the one with the lowest acceptable spoke tension that takes all the loads of a regular trip without going out of true.

bigfred 

DOS,

I'm running a OP, 36, 3X, 2.0 at around 129. No problems after thousands of miles under my Clyde ass. I only know the tension because I touched them up this past week for the first time in eon's. I wouldn't imagine that 134 would be too much an issue for them. But, do you need the tension? I'm a 2mtr, 125kg monster, so for me it's necessary.

Panthers007

I've heard many people remark they had run 145Kgf and more on Mavic's for years with no problems. Not that I would recommend it - but no one seemed to have problems. And these were skinny training rims usually. I would council to back it off to the Mavic specs on a new build, but don't have a heart-attack either if you find the wheels you've been riding on for 5 or 10 years is well over the Mavic recommendations.

One other thing to take into consideration: Always check spoke-tension without a tire/tube on and pumped up with air. The pressure from a tire/tube will give you readings on a spoke tension-meter that are always higher.

Happy Trails!

<edit> If you get a chance to use/purchase an FSA tension-meter, go for it! It's much more accurate than the Park. Or the Hozan, DT, Wheelsmith, etc. It's the one designed, and approved by him for FSA to construct, by Jobst Brandt - author of The Bicycle Wheel.

DOS

One last question on Tension. Since starting this thread, I have checked three additional wheels I built without use of a tensiometer and found them to be consistent is two ways; too much average tension (between 125 and 137 Kgf), but pretty good eveness (variances within 10-15Kgf). What got me thinking about tension and buying a tensiometer in the first place was that a friend of mine had a Open Pro rim fail around several eyelets, cause of which very likely was too much spoke tension. Since I have been riding around on wheels -- in some case for quite some time for many miles -- that also had too much tension , yet had no problems, I am wondering, just how far above recommended tension does one need to go before a rim will fail as badly as my friend's did (the eyelets weren't just cracked, they were almost completly pulled out of the rim)? I mean, my tension level was only marginly above recommended so I am assuming my friend's wheel was much higher, but I can't figure out how whomever built the wheel got that much tension on the spokes without rounding over the nipples.

Panthers007

Generally quite high. Before this inaccurate $60 toy arrived, from my research, people were blissfully riding about at around 145Kgf on their Mavic's for years and years - decades in my case. As soon as the Park TM-1 hit the market, we began hearing a flood of high-readings. But not of wheel failures. How high does it take before you suffer failure? Some Mavic's were rolling around at 180+Kgf. without breaking. Much depends on the weight of the load and the type of cycling the wheels are going through. And are the wheels being maintained for trueness? Bottom line: There is no set point.

I think the Park TM-1 has done a lot to encourage new builders to begin a new hobby/meditation form. For everyone else, it seems to have increased anxiety.

By the way - if you are serious about checking spoke-tension - get the FSA tension-meter. Leaves the Park in the dust. And forget the Hozan and DT models. A bit of searching will show you why FSA is what is best for close-to accuracy.

DOS

Since the wheels I ride around on cost less per pair at most shops than the FSA guage, making that kind of investment seems a bit over the top for my needs. I think, since my wheel building by feel had me pretty close to acceptable levels of tension and eveness anyway, I figure using TM-1 gets me close enough, any error factor notwithstanding. And the meditative benefit has also been nice.

Panthers007

I agree - you likely don't need one - they cost around $250 - unless you are gung ho! about building wheels. My point is not to let the $60 Park toy drive you batty. Nobody's wheels magically folded-up when they found out they were riding on 149Kgf spokes for 8 years, now clutching their TM-1 - and their heart at the same time. "ShrieeeeeeK!!!" <thud>

rydaddy

If spoke tension was too high, you would have known after stress relieving (or after some hard impacts while riding). Your wheel would have taken on the the 'potato wedge' shape. This is discussed in Jobst Brandt's book. The strongest wheel is one that has the highest possible tension without getting too close to the limit, where said potato wedge occurs.

Just my $0.02

DOS

Thanks, your point was clear. I can get a bit obsessive about this sort of stuff, no so much out of anxiety but I can be a bit of a perfectionist about these sorts of things (but not so much that spending 250 bucks for a tensionmeter is worth the strife on the homefront it would cause).

On that whole issue of of reaching point of folding up the wheel, how do people even get close to that much tension? I run out of spoke threads and start rounding off the corners of nipples before I get anywhere near that much tension.

rydaddy

I don't mean to suggest you should build your wheels this way. I'm just saying if you're worried that spoke tension was too high, you would know it. If you're winding up the spokes excessively, rounding nipples, or have sore wrists, you've reached the limit in tension.

DOS

Understood; I just meant I don't think I could get spokes to that high tension if I tried. But perhaps if I had a better spoke wrench...

jack002

I don't know when it was that the spoke tension tool came in and took over common sense. Well, its not 'common sense' really, its between that and 'zen' somewhere I suppose. I've only built a couple wheels, and they were years and years ago, but I keep my wheels true and de-taco a few here and there. I use a method where I pinch a pair together on the same side and feel how tight they are. I do that for the entire side and study it. If one or two seem really loose or tight I see how I can adjust that out, repeat. I have not read these wheel building books, and maybe all this math and measureing are needed for high end racing wheels, but for the plain jane almost-a-wal-mart bike wheels some psudo-zen spoke pinching should be all you need. And even on the high end stuff, if you can feel and pluck a 'perfect' wheel and then check yours and it has no perceptable difference, can it really be built wrong?

Jack