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Wheel Not True at Seam

Old 10-21-16, 08:28 AM
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Abe_Froman
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Wheel Not True at Seam

I recently began breaking spokes (2 in 100 miles). I've replaced the most recent one, and realized my wheel was undertensioned. I took all the spokes up to 110-120KgF, and retrued the wheel.

I can't get it perfect. Right at the rim seam/joint, it's off about 1.5mm radially, and maybe 0.50-0.75mm laterally. I've got the rest of the wheel perfect, or at least as perfect as I care to try and get it. This small wobble is by FAR the worst part of the wheel.

My question is - is this normal? It seems like my attempts at truing on this spot don't have any effect. I'm assuming this is a function of the seam itself and is normal? (I hope) Any reassurance would be helpful
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Old 10-21-16, 08:52 AM
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dabac
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"Normal" is a tricky word in these circumstances.
Rims being less round at the seam is quite common.
All rims made from extrusions rolled into a hoop probably are, if you measure close enough.


Usually, it's not functionally important.


Roads certainly aren't flat within a millimeter or two for a length of an average wheel circumference.


And who knows how uniformly high/wide tires actually are?


1.5 mm sounds a bit more than average off round though.


The seam being off laterally has never troubled me so far, but the phenomena as such wouldn't surprise me.
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Old 10-21-16, 09:06 AM
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1.5mm out of round is a bit on the high side, but as long as you can adjust the brake pads so they will not touch the tire then it won't be a problem at all. 0.75mm of lateral movement is insignificant, unless you have BP-OCD (Brake Pad OCD, which means you believe brakes need to engage at 1mm of lever movement).
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Old 10-21-16, 09:12 AM
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I certainly do not have Brake Pad OCD. If anything, I like them a bit on the loose side...better leverage when the lever gets closer to the bars. Thanks for the help. The 1.5mm is also on the high side of my estimate, might be a shade less than that. And since it's a hop not a flat spot the tire will actually move AWAY from the pad a shade when the hop comes around.
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Old 10-21-16, 09:15 AM
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If the seam is pinned and the joint is misaligned laterally it can be sanded smooth to help reduce the irregularity. I've done that before. Use a block and the right grades of sandpaper. If the irregularity is up and down it will be tougher to correct but probably means more spoke tension at that point.
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Old 10-21-16, 09:24 AM
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I respoked a Mavic Open Pro recently after straightening a ding and while truing I noticed a flat at the seam. I decided to just replace the rim since it had damage anyway. I tensioned the spokes different on the replacement rim than on the used rim I respoked that had the flat spot.


On the one with the flat spot, I brought all spokes to the threads disappearing at the nipples, and then used this as a starting point to turn all nipples the same. On the new replacement rim, I left a few threads exposed and started tensioning by increments, then as they got tighter, I went by feel and by judging resistance.


When I was done tensioning by feel on the new rim, I noticed the spokes near the seam weren't as deep in the nipples as the rest. The wheel was rounder than the rim I had tensioned just by turns and not by feel. Then I read on Sheldon Brown about wheel building, that some rims have defects near the seam that can cause the spokes near them to require a different setting.
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Old 10-21-16, 09:33 AM
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Originally Posted by thumpism View Post
If the seam is pinned and the joint is misaligned laterally it can be sanded smooth to help reduce the irregularity. I've done that before. Use a block and the right grades of sandpaper. If the irregularity is up and down it will be tougher to correct but probably means more spoke tension at that point.
Everything is aligned correctly and there is no damage. It just seems as if the wheel is stiffer and much less cooperative at the seam. I'm assuming it isn't worth the difference in spoke tension it would take to true it in this area. I rounded off a spoke nipple fussing and trying to make it perfect. I replaced the nipple, trued it up again to how I had it before at a good tension, and am now going to leave well enough alone lol!
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Old 10-21-16, 10:30 AM
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When the wheel is used do you notice anything amiss? Do the pads rub at the seam? Do the pads catch at the seam when applying the brakes (resulting in a moment of grabbiness)? Can you feel a up or down sensation when rolling along on a very smooth road? If none of these are present you have no effective problem.


I'll add that a wheel lasts longer with the spokes as consistent in tension as possible. So how "perfectly" true a wheel is is not the sole goal when building, too bad many customers don't realize this. Andy.
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Old 10-21-16, 10:47 AM
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Originally Posted by Andrew R Stewart View Post
When the wheel is used do you notice anything amiss? Do the pads rub at the seam? Do the pads catch at the seam when applying the brakes (resulting in a moment of grabbiness)? Can you feel a up or down sensation when rolling along on a very smooth road? If none of these are present you have no effective problem.


I'll add that a wheel lasts longer with the spokes as consistent in tension as possible. So how "perfectly" true a wheel is is not the sole goal when building, too bad many customers don't realize this. Andy.
I put over 5000 miles on the wheel and never realized it was there until I was replacing a spoke
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Old 10-21-16, 04:27 PM
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I use a file in cases like these. I don't aim for perfection but do enough to make it close enough.
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