Carcinogent

Hello fellow bicycle mechanics,

Something very strange is happening with the new wheelset i just built. Some details.
DT Swiss RR440, Chris King r45, DT Comp 24 spokes x2 front, Velox tape (95-100kgf tension), brass nipples
DT Swiss RR440 Asymmetric, Chris king r45, DT Comp 24 spokes, x2 NDS and Crow's foot DS, velox tape (117-120kgf tension)

After i rode it for the first time, some spokes on the NDS came loose (I had greased the threads and lubed the nipples, thinking the asymmetric would add enough tension...). So I rebuilt the rear wheel with new clean nipples on the NDS and degreasing the rim/threads. The second time around the wheel came together as if by magic...it was super easy.

However once i put a tyre and inflated it on the rear the wheel came out of true at the joint. Once i deflate it it comes true again. I was thinking there could have been some spokes left twisted so the pressure of the tyre caused to untwist, however, once deflated there is no problem. That happened with 2 different tyres (Conti GP4000 and Vittoria Home trainer). One thing i noticed is that the rim tape (Velox) has gotten skewed to one side of the rim on a couple of places. I am thinking the thick rim tape caused the tyre beads to push more on some parts of the wheel causing it to come out of true. Other than that I have absolutely no idea on what is going on, especially that before I rebuilt it the tyre installed just fine. Could it be a rim defect since it happens at the joint? This is not the first wheelset I have built, and I am riding/training/racing the other ones I have put together myself with zero problems for 2-3 seasons. I am no stranger to wheelbuilding, tension meters, stress relieving etc.

Does anybody have input or suggestions as to what could be causing this?

Thanks in advance!

Andrew R Stewart 

First- how out of true is the wheel becoming with inflated tire?

Second- Why a funky spoke pattern (crows foot)? Andy.

ThermionicScott 

Did you stress-relieve the wheels?

Since the rim is double-walled, it wouldn't hurt to re-true it with a tire on and inflated.

Bill Kapaun

Did you actually use a tension meter?
Tensions within 5% on each side?

I'm familiar with intramedullary nailing of the tibia, but I wouldn't perform it.

hkhailey

Putting the fully assembled and inflated tire back on the stand is always my final truing step. Sometimes it needs a bit more and others, not so much. But this is the step where I go for lateral perfection and just a check on the vertical. (I have seen inner tubes cause similar problems but generally with wider (32-38C) set ups.)

Remove the air, tire tube and rim strip and inspect the seam (a good magnifying glass helps to differentiate between scratches and minute cracks). If it passes the visual inspection, you may try tapping close to the seam (use a cone wench handle or anything similar that has a plastic coating) with your ear close and listen for any out of place vibration or slight buzzing sound which could indicate a defect.

If all seems good, do a final truing on the stand with the tire inflated. Then try it on the bike and recheck after a few blocks, then a few miles if it's still good. If not, I'd see how good the warranty on the rim is.

FBinNY 

It could be anything, from something in the rim to something you did. It might somehow be related to the spoke pattern, or not.

So rather than fret over the cause, you could cut to the chase, and simply correct the true based on the mounted tire and be riding tomorrow. If it stays true, don't argue with success, if not, then you can go back an sweat what the issue might be.

Carcinogent

Thanks for all the suggestions.

I followed FB's advice and i re installed the tire the next day. I readjusted the rim tape on the places it has gotten really skewed. Since i assumed the tire must have pinched it (the RR440 seems to be quite a tight fit for the tyres I put on it) I put some dish soap on the beads with a wet sponge to aid tire installation. After i pumped the tyre up to 120 psi i could hear the beads popping in to place. It took 3-4 'pops' for the tire to get fully seated and when i put the wheel on the stand it was perfect. As per FB's advice I didn't argue with success and I rode the wheel for about 30-40miles and it was fine. Therefore an improperly seated tyre in combination with a tight fit rim must have caused the wheel coming out of true...strange but i guess it happens.

To answer questions from others, I did use a tension meter and stressed relieved the wheel before the final truing. Thanks to a lot of the information and expertise on these boards, this was probably my 4th or 5th wheelset built in the last 3 years.

About the Crow's foot pattern, for those not familiar with it, the spokes are in groups of 3. The middle one is radial heads OUT and the outside are x2 heads IN, therefore that way I maximized the DS bracing angle by a certain amount as compared to a regular x2 pattern. That coupled with the asymmetric rim, led to a wheel with the NDS spokes having about 70% of the tension of the DS (as compared to 45%) which is not bad especially given the fact the hub is Shimano 11 speed compatible. Therefore with 24 spokes I got a rear wheel that is as balanced as my 32 spokes track wheel. The goal behind that particular wheelset was having wheels that are lighter than my 1900g all day training wheels. I didn't want to sacrifice performance/stiffness so i had to look for non-classical ways=) So with nearly 500g saved i got something for nice roads/weather days and climbing where I hope the wheels would shine the most.

FBinNY 

Not strange at all, as every fireman knows. When a flexible tube is pressurized (such as a canvas fire hose or tire) it want's to straighten. At high pressure it will fight hard to be pencil straight.

So it the tire is unevenly seated, the rim and tire can't both be straight at the same time, and a bit of a shoving match ensues. Who/what wins is a matter of the pressure inside the tire, vs. the rigidity of the rim, and it seems that in your case the tire was winning, or at least gaining a concession from the rim.