Strange rim behavior

[perwjensen]

Hi all,

Need some help on a strange wheel issue. I bought a carbon rim AR56 PRO tubeless and hookless earlier this year and built up a wheel on DT240 hubs. Here is the issue: with the tire at low pressure (20osi) I center my brakes on the rim, then pump it up to 60-65psi but then the rim moves toward one side of the brake by 1-2 mm. When the pressure drops again overnight to 20psi it's back on the original center. What is going on? Is that normal or is it an indication that I haven't build the wheel up correctly?

My guess is that the differential spoke angles DS vs NDS affect the movement, but I haven't experienced it with another wheelset I built from scratch. Please note I'm a beginner wheelbuilder but have used the right tools to get a good build (a good stand, dials, tensiometer, etc.). THe constant movement of the rim on the brake is driving me crazy, so any advice is appreciated.

[TobinHatesYou]

Tire pressure is exerted in all directions including inward, compressing the rim. Increase the tension in all your spokes and try again.

[pdlpsher1]

Do you have a dishing tool? Re-dish the wheel with the tubeless tire mounted and pumped to 65psi. Good wheelbuilders will do this on tubeless wheels. On tubeless wheels the compressive force on the rim is far greater than on a non-tubeless setup. There was a published article on a pupular cycling website recently about this.

[wheelbuilder]

It's both answers above. Most tubeless wheels drop a considerable amount of Spoke tension from when built with tire mounted and aired up to normal or higher psi.
Air your tires to max allowed psi and tension spokes again. It will be good after this is done once.

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[chrisw91]

What's the tension balance like between DS & NDS on the build? If one side (usually NDS) is significantly lower than the other (usually DS), you'll find that the inward compressive force from the inflated tyre will detension the spokes to a different extent, causing the wheel to move out of dish.

I'd revisit the spoke tensions & as suggested above try balancing when you have a tyre fitted & inflated.

[perwjensen]

Thank you all for your advice it's super helpful!

I'll tension spokes with tire inflated to preferred pressure.

@chrisw91. Given the wheel is dished to center how can I rebalance DS vs NDS tension? Right now I have DS:NDS tension of 2.0:0.7 roughly. Given the angles I would've expected more like 2.0:1.0 but that moves the rim out from center line quite a bit.

[pdlpsher1]

What I would do is to increase the tension on the DS only (say, one turn of the nipple on all DS spokes), then use a dishing tool and lowly increasing the NDS spoke tension until the wheel is centered. Of course do it with a tire mounted to the rim. In general a high spoke tension will minimize the effects of tension loss from a tubeless tire.

[perwjensen]

@pdlpshr1 That is exactly the approach I took, however with the tire off. I'll redo with inflated tire, built tension on DS and then dish with NDS spokes. Good to hear it from experinced people

[goodboyr]

Perhaps it's implied, but if you tension to spec with the tire inflated, then depending on the wheel, you might end up with too high a tension when the tire is deflated. Not sure that's what you want. I always assume the tension specs are for a rim without tire installed.

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[perwjensen]

Perhaps it's implied, but if you tension to spec with the tire inflated, then depending on the wheel, you might end up with too high a tension when the tire is deflated. Not sure that's what you want. I always assume the tension specs are for a rim without tire installed.

Sent from my SM-G998W using Tapatalk

Good point! I'm inflating tire to ensure dishing is correct and then measure the tension change to correct the tension specs.

[wheelbuilder]

Perhaps it's implied, but if you tension to spec with the tire inflated, then depending on the wheel, you might end up with too high a tension when the tire is deflated. Not sure that's what you want. I always assume the tension specs are for a rim without tire installed.

Sent from my SM-G998W using Tapatalk

This is true, but some tubeless tire/rim combos just drop so much tension with tire aired up you have to bring it to tension with tire mounted as the final process. Sounds to me like the OP has one of these combos if the dish is changing when he airs up. Tension is too low.

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[romanmoser]

Now image having that dropping tensions issues with internal nipples ahah
Or external nipples that have to be serviced like internal nipples ( winspace , tape n tire off n sealant )

Except for example the bora wto ultra , only internal nipples wheels serviceable without dismounting tire and sealant with their special tool