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Old January 18th, 2020, 12:13 PM   #1
MrAtom
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Have you ever been hit with a wheel-weight while riding?

When riding my bicycle, I see these things on the road all the time. I do occasionally see one or two when riding my motorbike as well. In fact, I see enough of them to assume that wheel-weights falling off of a wheel is probably a fairly common occurrence. I can only imagine that it would probably hurt to get clobbered by one of these, and it might be actually deadly on the freeway (imagine getting hit in the neck, or getting hit in the center of your chest. Might be enough to cause an abnormal rhythm/heart attack?) I seem to remember @csmith12 saying he tapes his down on his track bikes, and I have always done that myself on my streetbike since reading that years ago.

That said, I've never heard of a rider getting injured by one of these, and have never heard of them hitting cars, cracking windshields, etc, which makes me think my concerns might be entirely hypothetical. Does anyone here have any experience or insight on the matter?
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Old January 18th, 2020, 01:07 PM   #2
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Yup, been hit by these things couple times and seen countless others fly off. Mostly while riding my bicycle from Santa Barbara on Hwy-101 north to Vandenberg AFB or south to Ventura. It’s worse now that they’re made from steel instead of lead. Can cause chips in windshield now due to hardness of steel. Not as damaging as rocks or other debris which tends to be larger and may actually have backwards velocity. Those can cause cracked windshields.

Wheel-weights always have forward or zero velocity when they fly off. At bottom of wheel rotation, they have zero velocity and if they fall off there, they would fall straight down to ground. At top of wheel rotation, they are moving forward at twice speed of car. Falling off there, they would fly forward at twice speed of car. This explains why I’ve always been clobbered by them from behind when riding my bicycle on side of hwy-101. Only been hit twice in 15-yrs of riding there (~37k-miles on hwy-101).

Actual impact energy is quite low due to their low weight. And they typically bounce couple of times before they hit you, slowing them down significantly. That’s from reference point of almost stationary observer on side of road.

From reference point of motorcyclist following car, it’s slightly different. A wheel-weight flying off top of wheel would be moving forward away from you at same speed of car. So 80mph car would launch wheel-weight forward at 160mph. Weight would appear to be moving away from you at 80mph and bounce off to side of road.

If fell off at bottom of wheel, it would have zero velocity and fall straight down. Now if somehow bounced up higher, it would appear to be flying towards you at your speed. So if you were following car at 80mph, it would look like it’s flying towards you at 80mph.

What kind if impact are we looking at? Let’s compare to more common household objects like... a baseball. A 1/2-oz wheel-weight is 1/10th mass of baseball. Or have momentum of baseball moving at 8-mph. Which is speed of baseball dropped into your hand from 2.3-ft above. Not that bad at all.


Relevant equations:

momentum P = mv
free fall t = v/g
free fall h = v^2 / 2g

Last futzed with by DannoXYZ; January 18th, 2020 at 02:40 PM.
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Old January 18th, 2020, 02:34 PM   #3
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Now the reason wheel-weights are required to be taped up on track is that they can cause crashes. Running over one in corner would lift your wheel off ground and lack of contact would cause crash. Heck, I've crashed on street when cornering over bottle-cap! Others have crashed over wet-leaves.
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Old January 18th, 2020, 03:09 PM   #4
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Thankfully I have never been hit by or crashed due to wheel weights. I can see how they could pose a danger.
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Old January 18th, 2020, 03:46 PM   #5
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DannoXYZ's above post is the main reason, traction concerns and general debris on surface.

They come off, fall to the track surface, a hot, sticky tire picks them up and it becomes a high speed projectile. Been hit by a few of them over the years, mostly no big deal overall. They do chip paint and can sting your fingers a bit while at track speeds.
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Old January 19th, 2020, 08:55 PM   #6
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Well, that was a way better explanation than I was even hoping for. Thank you, Danno! I guess I'm not worried about it now, seeing as how even getting hit by rocks only kind-of hurts sometimes. One time a big one hit me in the fingers, and that sucked, but with this new info, rocks are still a much bigger concern than wheel weights. And even then, I don't worry about rocks a whole lot.
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Old January 22nd, 2020, 07:48 PM   #7
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Interesting how motorcycle track orgs are worried about taping wheel weights, but car track orgs are not. Same tracks, same stick-on weights.

Side note: I definitely lost one off the Miata at my last track day. The shake is real.
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Old January 30th, 2020, 10:25 AM   #8
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Quote:
Originally Posted by choneofakind View Post
Interesting how motorcycle track orgs are worried about taping wheel weights, but car track orgs are not. Same tracks, same stick-on weights.

Side note: I definitely lost one off the Miata at my last track day. The shake is real.

different dangers.

What happens if a car runs over a loose wheel weight in a corner? probably nothing.

What happens if a bike runs over one while leaned over in a corner. A big wiggle and a rider needing a new pair of underwear at least, a crash and injury at worst.
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Old February 1st, 2020, 08:34 PM   #9
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What happens if a bike runs over one while leaned over in a corner. A big wiggle and a rider needing a new pair of underwear at least, a crash and injury at worst.
Oh definitely! but at the end of the day... same tracks, and not every track cleans their tarmac with a toothbrush between events. There's a good chance that car parts will affect moto riders, that's all I was thinking.
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Old February 9th, 2020, 02:21 AM   #10
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Originally Posted by choneofakind View Post
Oh definitely! but at the end of the day... same tracks, and not every track cleans their tarmac with a toothbrush between events. There's a good chance that car parts will affect moto riders, that's all I was thinking.
Every weight I put on at the two scca races I worked got taped; and everyone else was supposed to tape theirs too... never saw any untapped weights except the hammer on weights on two sets of wide fives
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Old February 9th, 2020, 03:06 PM   #11
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Every weight I put on at the two scca races I worked got taped; and everyone else was supposed to tape theirs too... never saw any untapped weights except the hammer on weights on two sets of wide fives
Weird!! Wasn't mentioned, written, discussed, etc anyhere. Never came up in tech, no one that I saw in the paddock had any tape on their wheels. Must be a thing that comes and goes over time.
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Old February 9th, 2020, 09:39 PM   #12
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Originally Posted by choneofakind View Post
Weird!! Wasn't mentioned, written, discussed, etc anyhere. Never came up in tech, no one that I saw in the paddock had any tape on their wheels. Must be a thing that comes and goes over time.
Hoosier tire tapes everything unless you tell them you have your own tape every tire I saw had tape pulled off; weight done, an taped again. I saw Goodyear taping too... maybe it’s just the Hoosier races only been to 2 SCCA races ... we taped all the weights at all the drag races I went to as well; hate to see some weights fly off
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