Rims, Spoke vs. Cast - Safety vs. Convenience

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Rims, Spoke vs. Cast - Safety vs. Convenience

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Harley Davidson Forums >> Harley Davidson Motorcycles >> Dyna Glide Models >> Rims, Spoke vs. Cast - Safety vs. Convenience

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Rims, Spoke vs. Cast - Safety vs. Convenience - 5/21/2008 10:28:51 AM

Travlinman314

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As most of you know, I totaled my bike in a head on collision with a kid not paying attention. He turned into me, we collided, boom, end of that story.

Last week, while getting a few important documents from the bike, and taking pictures, I noticed a few things, but I was kinda druged up with pain killers. Well, the front end snapped off the bike, and the way it was sitting last week, the rim looked like it took a little of the impact.

Wow, I went back today to get the rest of my stuff before it gets taken away to the scrap yard. I turned the rim upside down, and wow, the small dented part I noticed last week, was nothing compared to the other side, almost 180 deg. away.

Seems the rim took almost all of the impact, first into the car front bumper, then after snapping the forks, it hit a cross member in the frame. This gave the rim two areas to bend and the spoke cusioned the blow, and the cross member of the frame also gave in and bent. (not sure if it was designed to do all this, but it worked)

I'm no expert or scientist, but I know I basically walked away from a head on collision with a car. Me travelling about 35 to 40 mph, and him about 20 to 25 mph. With the impact of the rim, (twice), and the crossmember of the frame bending, all must have cusioned my blow initially, and then me hitting the hood and windshield, both fairly soft cushioning materials (considering) let the result be fairly satisfactory in my eyes.

Anyway, my point is, I had the FXD, with the cast rims, but changed them to the spoke rims. Do you think the cast rims would have had the same effect and cushion the blow the same? Besides being a lucky SOB surviving the crash the way I did, do you think the result could have been worse with a more solid cast rim?

Just asking, maybe there is an expert out there somewhere....

< Message edited by Travlinman314 -- 5/21/2008 2:05:35 PM >

Post #: 1

RE: Rims, Spoke vs. Cast - Safety vs. Convenience - 5/21/2008 11:23:42 AM

hk_shooter

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Very good question, Travlinman.
I know they build "crush zones" into cars/trucks but not sure about bikes.
I hope your recovery is going well.
Heal quick brother, the road is calling.

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Post #: 2

RE: Rims, Spoke vs. Cast - Safety vs. Convenience - 5/21/2008 11:34:23 AM

2007fxdc

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I'm not engineer but it would seem to me, at best case, the cast wheels would have snapped/broken instead of bending like the spoked rim did. That might also have been a good thing though. Basically the more stuff between you and what you hit that can give way and dissipate energy, the better. If the rim had not bent and the forks not snapped, I believe you would have hit that windshield with more force than you did and the outcome may have not been quite as good.

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RE: Rims, Spoke vs. Cast - Safety vs. Convenience - 5/21/2008 12:24:17 PM

kk6pg

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You bring up an interesting question
I suspect it has everything to do with the alloys in the cast wheel. Spoked wheels are designed to flex under severe stress, whereas cast will fail under the same conditions.
Ive seen cast wheels twisted like a pretzel, and only have some stress fractures in them. I've also seen cheaper cast wheels explode under duress.
Only the moco knows for sure what they'll withstand.
Unless someone has some cast wheels they want to do some scientific testing with.

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Post #: 4

RE: Rims, Spoke vs. Cast - Safety vs. Convenience - 5/21/2008 12:57:16 PM

subculture08

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I do not know the answer, but from my experience the cast wheels do not crush on impact.
My 04 FXDI...

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RE: Rims, Spoke vs. Cast - Safety vs. Convenience - 5/21/2008 2:03:07 PM

Punty

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my $.02 for what its worth,

10 plus years ago, while traveling at 40-50 I once hit a pothole (for a lack of better words) and wound up bending both cast rims. NO cracks just flattened out 2 nice spots on the rim.

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RE: Rims, Spoke vs. Cast - Safety vs. Convenience - 5/21/2008 6:29:17 PM

Wyde Glyde Bry

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quote:

ORIGINAL: Travlinman314

I'm no expert or scientist, but I know I basically walked away from a head on collision with a car. Me travelling about 35 to 40 mph, and him about 20 to 25 mph. With the impact of the rim, (twice), and the crossmember of the frame bending, all must have cusioned my blow initially, and then me hitting the hood and windshield, both fairly soft cushioning materials (considering) let the result be fairly satisfactory in my eyes.

Interesting perspective. Here are a few random thoughts from someone who is also no engineer or physicist...

I'm not sure how the bike can act to dampen any significant portion of the impact energy. As the bike slows down during the collision, our body keeps moving forward at the same speed until something slows it down. That something usually ends up being parts of our own bike, whatever it is we're crashing into, and the ground.

It's not as if we're belted into the bike (as in a car/truck if you wear your seatbelt), thereby becoming part of the vehicle and slowing down with it as forces act upon it. Crumple zones designed into cars/trucks are designed to work along with seatbelts and airbags.

With a motorcycle, if not for the force of gravity holding our butt down in the seat, and the force of our grip on the handlebars... we're basically just along for the ride.

Like I said, just a layman's opinion -- I'm not sayin' I'm right or wrong. This is just what makes sense to me at the moment.

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RE: Rims, Spoke vs. Cast - Safety vs. Convenience - 5/21/2008 7:18:15 PM

ssls6

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spoke wheels absorb more energy before and after they bend. That's why you see them on dirt bikes. They can take a big strike and not loose air either. With the exception of flat repair, spokes offer several advantages over cast. I love the 21" spoke wheel on the front of my wide glide. I may change the rear for a cast wheel only for roadside flat repair...it's pretty rare for a front to pick up a nail.

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Post #: 8

RE: Rims, Spoke vs. Cast - Safety vs. Convenience - 5/21/2008 7:23:08 PM

mikedmeyer

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If you're coming down on top of the wheels, then this makes sense, but in a head on collision it doesn't. They still absorb energy, but you're a separate body from your bike long before this can help you.

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Post #: 9

RE: Rims, Spoke vs. Cast - Safety vs. Convenience - 5/21/2008 8:04:14 PM

YoCon

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Wydle glyde bry has it correct. The spoke wheels probably helped slightly with bike, but if moving the rider will always be held to rules of inertia and mass.

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Post #: 10

RE: Rims, Spoke vs. Cast - Safety vs. Convenience - 5/21/2008 9:05:41 PM

KBFXDLI

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Having had the same type of wreck.......I think the rider is the crumple zone...

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Post #: 11

RE: Rims, Spoke vs. Cast - Safety vs. Convenience - 5/22/2008 3:34:44 AM

Travlinman314

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Joined: 8/10/2007
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quote:

ORIGINAL: Wyde Glyde Bry

quote:

ORIGINAL: Travlinman314

I'm no expert or scientist, but I know I basically walked away from a head on collision with a car. Me travelling about 35 to 40 mph, and him about 20 to 25 mph. With the impact of the rim, (twice), and the crossmember of the frame bending, all must have cusioned my blow initially, and then me hitting the hood and windshield, both fairly soft cushioning materials (considering) let the result be fairly satisfactory in my eyes.

Interesting perspective. Here are a few random thoughts from someone who is also no engineer or physicist...

I'm not sure how the bike can act to dampen any significant portion of the impact energy. As the bike slows down during the collision, our body keeps moving forward at the same speed until something slows it down. That something usually ends up being parts of our own bike, whatever it is we're crashing into, and the ground.

It's not as if we're belted into the bike (as in a car/truck if you wear your seatbelt), thereby becoming part of the vehicle and slowing down with it as forces act upon it. Crumple zones designed into cars/trucks are designed to work along with seatbelts and airbags.

With a motorcycle, if not for the force of gravity holding our butt down in the seat, and the force of our grip on the handlebars... we're basically just along for the ride.

Like I said, just a layman's opinion -- I'm not sayin' I'm right or wrong. This is just what makes sense to me at the moment.

Good point, and I realize we are not belted in. However, not knowing it at the time, I must have held on for dear life when I saw it coming, as the handlebars were flipped fowrard and around by almost 2 feet. The throttle cables kinda held it back, or that was the longest I could hold on, not sure.

I'm guessing I unknowingly sacrificed my forearms and wrists, (as they are strained and hurting). How long I held on, not sure, did it make a diffference in that "Crumble Zone", I'm not sure.

Everything you say makes sense, but did my instinct to "hold on" help take advantage of the intitial impact and "Crumble Zone" cushioning?

It's funny, I remember the "Oh Sh!t" moment, and then the "rolling to the ground" from the windshield moment, but nothing in between comes to memory. So I really can't say what my reactions were, except for deciphering the evidence of the pain spots on my body and the visual damage done to the bike and windshield.

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Post #: 12

RE: Rims, Spoke vs. Cast - Safety vs. Convenience - 5/22/2008 3:39:22 AM

Travlinman314

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Joined: 8/10/2007
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quote:

ORIGINAL: ssls6

spoke wheels absorb more energy before and after they bend. That's why you see them on dirt bikes. They can take a big strike and not loose air either. With the exception of flat repair, spokes offer several advantages over cast. I love the 21" spoke wheel on the front of my wide glide. I may change the rear for a cast wheel only for roadside flat repair...it's pretty rare for a front to pick up a nail.

Now here's an interesting and funny point here.

While the rim had two major dents, and spokes were bent, broken and dislodged, the tire and tube still are holding the original air. Not saying it means anything, I just thought that was funny.

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Post #: 13

RE: Rims, Spoke vs. Cast - Safety vs. Convenience - 5/22/2008 6:01:20 AM

Punty

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Joined: 3/12/2007
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quote:

ORIGINAL: Travlinman314

quote:

ORIGINAL: ssls6

spoke wheels absorb more energy before and after they bend. That's why you see them on dirt bikes. They can take a big strike and not loose air either. With the exception of flat repair, spokes offer several advantages over cast. I love the 21" spoke wheel on the front of my wide glide. I may change the rear for a cast wheel only for roadside flat repair...it's pretty rare for a front to pick up a nail.

Now here's an interesting and funny point here.

While the rim had two major dents, and spokes were bent, broken and dislodged, the tire and tube still are holding the original air. Not saying it means anything, I just thought that was funny.