Spoke Tension Drop with Tire Installation

[Mr.Gib]

The situation: I am getting very significant 25% - 30% drop in tension on both sides of the wheel. (Pacenti SL23 version 2 rim.)

The question: If I set spoke tension to recommended level with the tire installed, will the rim be damaged when I remove the tire? Or what about adding just a bit of extra tension (10 - 15%) with the tire installed? Current build is around 120 kgf on drive side without the tire.

(I know this question has been asked before but a search only showed questions and no definitive answers.)

[jeffy]

will be interested in the experts opinion on this.

If a wheel with tyre mounted is tensioned, stressed and perfectly true (I have heard this done for tubeless setup - tensioning/truing with tyre mounted to reduce the tension loss from the 'tighter' tubeless tyres) is there a chance that once the tyre is removed the true of the wheel is lost/impacted?

[Mr.Gib]

jeffy, the trueness of the wheel should not be affected. The pressure of the tire is uniform. If it wasn't the wheel would go out of true when you mounted the tire in the first instance (and I guess return to true when you unmounted it).

[kavitator]

Check NDS spoke with inflated tire - also with tire inflated rear rim is pulled to DS a litlle (around 1-2mm)


http://kavitec.blogspot.si/2013/01/vpli ... ik-na.html

[kulivontot]

Read comments here
http://www.novemberbicycles.com/blog/20 ... -drop.html
And here
http://www.novemberbicycles.com/blog/20 ... ow-up.html


Sent from my iPhone using Tapatalk

[11.4]

Clinchers? Adding tire pressure on a new wheel can cause the sidewalls of the rim to flex and release pressure on the tire. And many rims come into trueness as tension is increased -- they will want to go out of true every time you stress relieve the wheel until they reach a critical tension where everything stays uniform. So not only can you lose measured spoke tension, but the wheel can come out of true somewhat. This is not unusual. It does happen with tubular rims as well, especially shallow box section tubulars, but less with deeper section rims. It's relatively rare with quality-made deep carbon rims.

Quoted or recommended spoke tension is supposed to take tire effects into consideration, but those are only approximations anyway. When building a wheel, you want to achieve that actual tension at which the wheel is stable. I find that at that tension level, tire effects are minimized as well. Modern rims, hubs, and spokes are all fully capable of achieving higher spoke tension, so there's plenty of opportunity to increase the tension, if needed, without risking any kind of wheel failure. To see the actual measure of spoke tension change that OP is quoting seems odd and excessive. I'd suggest he go back and re-test spoke tension with a different tensiometer, preferably one with direct dial read like the DT. It might drop 10%, but 25-30% is either an error in reading or a problem with how the wheel is built. Have an experienced wheel builder with the right tools test the wheels. If you didn't relieve the spokes sufficiently, or are still working at too low a tension level, or tension is uneven, a greater tension drop is understandable, but those are deficiencies in wheel building technique.

[mattr]

As an aside. Check your pump gauge.
I had a mate come back with a wheel that wouldn't stay true. Turns out the gauge on their pump was under reading by about 40-50 psi when showing 100psi on the gauge.
Pumping it up properly solved the issue. And getting a decent pump.
(Low spoke count factory build wheel that I was trying to sort out for them)

[Calnago]

I'm wondering if the wheels were properly tensioned in the first place. They would be a lot more susceptible to the degree of change you're experiencing if that's the case. I had a Park Tensiometer that read about 20% higher and then I wondered why NDS spokes loosened up. I also have a DT Swiss Digital Tensiometer. Trouble is, I wasn't sure which one was "more" correct. It was quite a while ago and I really didn't have a sense for when that optimal tension had been reached, so I relied pretty heavily on a Tensiometer. I was using DT spokes. I sent both meters back to the respective companies for calibration checks and the DT Swiss meter was bang on while the Park was, as I said, reading high, but even after being "calibrated" by Park it still read higher than the DT Tensiometer. I trusted the DT Swiss charts as they give charts for tension for all of their specific spokes. The Park meter charts has approximations I would guess and their charts don't take into account whether or not the spoke is double or triple butted or just straight gauge (not sure it matters). In any case, through trial and error and a lot of stress relieving I eventually concluded the DT Swiss Tensiometer was giving very accurate results versus the Park. This is where experience can help you know when you're "there" as opposed to just translating a chart. I originally got the Park Tool to help with thin flat aero spokes where the digital DT Swiss Tensiometer wouldn't even register. But with those kinds of differences they you're seeing that's what I would guess is going on. Seems like a lot otherwise.

[dvdslw]

I was interested in a set of American Classic Argent's not to long ago until I started hearing about instances where the spokes would loose tension with some tubeless tires. I contacted AC about this and they confirmed that using any tire with a reinforced bead would in fact cause tension issues and possibly make the wheel out of round once inflated. I wasn't comfortable purchasing a wheel that I couldn't use whatever tire I wanted so I did my business elsewhere. I know its a different brand but they also use a thin walled aluminum rim which I believe to be the problem.

[Mr.Gib]

Wheel build seems quite good. Wheel has covered a few hundred kms, retensioned, and stress relieved. Wheel has stayed quite true. I am using a Park TM1 but only to assess relative tension - I do not consider it accurate and assume it reads higher then actual as is often reported. My pump is perfect - checked against a digital pressure gauge.

A whole lot of worthwhile info (thanks all) but only one response that remotely addresses my question - thank you 11.4:

Quoted or recommended spoke tension is supposed to take tire effects into consideration, but those are only approximations anyway. When building a wheel, you want to achieve that actual tension at which the wheel is stable. I find that at that tension level, tire effects are minimized as well. Modern rims, hubs, and spokes are all fully capable of achieving higher spoke tension, so there's plenty of opportunity to increase the tension, if needed, without risking any kind of wheel failure.

[sugarkane]

it is thing and the pacenti sl23 rims and most tubeless rims suffer from it pretty bad. it's too do with the way the tire bead interacts with the upper part of the rim bed.. non tubeless rims suffer a lot less but inflated tires will cause a small tension drop. the new ENVE 2.2 rims are really bad like 25kgf bad and around 2mm of swing.. to be frank the Parentis are not rims i will build with unless the customer supplies them. the extra cost of a pair of belgiums is money well spent. my suggestion is to offset the dish to the left around 1.5mm then you'll get a nice perfect dish in use. you can F around truing the wheel with the tire on but.. time is money and once you understand whats gona happen its not exactly necessary

[Mr.Gib]

Thanks sugarcane - that's been my take on things with the SL23's. The shift to tubeless style bead seats definitely changes things.

I ended up re-tensioning the wheel with the tire on and inflated - about a half of a turn per nipple - not much. The dish was never that far off but I still ended up making some final adjustments to get the tire dead center between the stays.

I did take the tire off afterward with no drama (to re-pin a loose sleeve at the seam - a shame this is still a problem with these rims) .

I will say that the latest version of these wheels creates enormous tire volume. My 25mm Michelin Power Comps measure almost 30 mm! Only 27 mm on the older SL23 rims. A lot of bikes will be limited to 23 mm using these rims.

[sugarkane]

thats a common thing with the wider rims.. with a 23c tire at least you'll only end up with the tire as wide as the rim. i think the profile is better too and leads to a better handling situation

[Zigmeister]

I would agree about the tension and initial build as well. I just got a new set of Strike SLG. I always put the wheels on the bike and put the brakes close to check how true the rim is from the factory.

All was good on the front/back.

After mounting my GP4000S II 25c tires and pumping them up. The front wheel went out of true.

So then I went around the wheel and trued the wheel.

November is right, and other good wheels built by some great builders, never had this issue. Reynolds obviously doesn't build the wheel, mount a tire/tube and pump it up to full pressure, and check the tension/true of the wheel.

November does this, and all is good.

Furthermore, I've read places where people say "don't true the wheel with the tire mounted". Huh?!?! If you have external nipples, makes sense to true it with the tire/air pressure where it should be just because of this situation above I write about.

Oh well. Rear wheel has stayed pretty good. Ride them a month or two and check the tension/true again. See how it holds up.

[whosatthewheel]

Tension drops, by how much depends on the rim (I would have thought the SL 23 wouldn't drop that much), the tyre pressure and whether you run tubeless or tubed. Generally tubeless is believed to drop more, but when I made some measurements on my HED + rims I didn't find any difference between tubed and tubeless.

https://whosatthewheel.com/2015/04/26/r ... e-tension/

120 KgF is healthy, provided the hub geomtry gives you a decent NDS tension and provided it is measured with a calibrated gauge (the Park Tool one is typically over-reading by up to 20%, so your 120 might be only 100). Going up to 130 KgF might help if you experience severe drop when you fit the tyre.