Shakes on descents with 404
06-17-14, 12:45 AM
#52
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When i spin my rims on the Stand. The valve stems both on front and back always come to rest at the 6 o clock position. so indicates i assume weight is heaviest at valve stem? as i use 80 mm tubes. the rims are clincher?
so should i put some weight opposite to that then?
so should i put some weight opposite to that then?
Take them to a bike shop that deals with ZIPP and have them take a look at it. If they can't figure it out...then will send the wheel to ZIPP. Its totally possible that the rim itself could have some kind of manufacturer defect. If ZIPP finds nothing is wrong with the wheel...then its user error.
06-17-14, 01:27 AM
#53
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Very amusing thread.
I live in a VERY mountainous area and never experience this problem. I have used literally dozens of different wheels over the years here, some carbon, some alloy, some shallow, some deep and some with extenders. I have never felt a speed wobble that wasn't about frame alignments, headset adjustment or a wonky wheel.
ALL bikes will develop the some wobble in a bike stand. ALL bikes. That was just funny.
I would suggest pulling off the tire, tube and rim strip and shinning a flashlight inside the rim to have a look. There could be a piece of resin that wet out but stuck there and was missed at QC. It's possible but unlikely.
I would also look at the tire and see if there are any scuff marks on the sidewall just above the brake track. A slight cut there can cause the casing to unwind very slightly and this will produce a wobble but only under certain conditions.
A rim strip that has drifted up and become pinched between the tire bead and the hook of the rim will do the same thing. Check that, too.
If you have bladed spokes make sure they are all oriented in the same direction. They can wind during truing and will cause issues at speed.
If you really are concerned about the weight of the valve stem (and the extra rubber to glue the stem to the tube) put your wheel magnet opposite the valve. Problem solved.
Not all rims are pinned opposite the valve hole. Some are welded or fused. That doesn't mean that is always the heaviest spot on the rim. Anyone who has built enough KinLin rims know that their natural heavy spot is actually at the valve hole. I asked them why, and they were aware of this, but they didn't have a clue.
Flame away, BF braintrust.
I live in a VERY mountainous area and never experience this problem. I have used literally dozens of different wheels over the years here, some carbon, some alloy, some shallow, some deep and some with extenders. I have never felt a speed wobble that wasn't about frame alignments, headset adjustment or a wonky wheel.
ALL bikes will develop the some wobble in a bike stand. ALL bikes. That was just funny.
I would suggest pulling off the tire, tube and rim strip and shinning a flashlight inside the rim to have a look. There could be a piece of resin that wet out but stuck there and was missed at QC. It's possible but unlikely.
I would also look at the tire and see if there are any scuff marks on the sidewall just above the brake track. A slight cut there can cause the casing to unwind very slightly and this will produce a wobble but only under certain conditions.
A rim strip that has drifted up and become pinched between the tire bead and the hook of the rim will do the same thing. Check that, too.
If you have bladed spokes make sure they are all oriented in the same direction. They can wind during truing and will cause issues at speed.
If you really are concerned about the weight of the valve stem (and the extra rubber to glue the stem to the tube) put your wheel magnet opposite the valve. Problem solved.
Not all rims are pinned opposite the valve hole. Some are welded or fused. That doesn't mean that is always the heaviest spot on the rim. Anyone who has built enough KinLin rims know that their natural heavy spot is actually at the valve hole. I asked them why, and they were aware of this, but they didn't have a clue.
Flame away, BF braintrust.
Last edited by Bob Dopolina; 06-17-14 at 07:13 AM.
06-17-14, 05:26 AM
#54
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When i spin my rims on the Stand. The valve stems both on front and back always come to rest at the 6 o clock position. so indicates i assume weight is heaviest at valve stem? as i use 80 mm tubes. the rims are clincher?
so should i put some weight opposite to that then?
so should i put some weight opposite to that then?
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06-18-14, 02:49 AM
#55
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Now as a Test. If i were to take off my tires and spin the rear rim really fast. Should the bike not shimmy on the stand at all, if wheel is balanced weight . since be no extra with the stem gone etc?
06-18-14, 03:19 AM
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06-18-14, 04:09 AM
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+1.
Thirty years of putting all kinds of bikes in stands and they all shimmy if you spin the rear wheel up enough.
Thirty years of putting all kinds of bikes in stands and they all shimmy if you spin the rear wheel up enough.
06-18-14, 04:14 AM
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Does that vibration damage the workstand ?
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06-18-14, 06:20 AM
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I always harmonically balance my workstands to prevent just that. Most people don't know this, but an oscillating bike wheel in a non-harmonically balanced lightweight stand can do a lot of damage, and even damage your tools if it's a bench mount unit, which is of course, why I also counter-balance my tools. You can never reduce resonance enough is my motto.
06-18-14, 07:00 AM
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Rubber pads should go under the feet of the workstand to reduce resonance .
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06-18-14, 08:48 AM
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06-18-14, 08:51 AM
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You need a carbon fiber workstand to handle the stresses.
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06-18-14, 08:59 AM
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A good mechanic will be wearing a Kevlar shop apron & safety glasses.
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06-18-14, 09:04 AM
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and rubber soled shoes.
06-18-14, 09:05 AM
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SHV. Spontaneous Human Vibration is a b*tch.
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