Shaving material off heavy rim of Shimano WH-R500 wheel

Discuss light weight issues concerning road bikes & parts.
justkeepedaling
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Location: by Crystal Springs (Sawyer Creek Trail)

by justkeepedaling

We are talking about stiffness to resist stress aka resist plastic deformation. You're just asking for your wheels to taco and fold. There has never been a design of road bike wheels in production with holes drilled in between every spoke (and that's even considering they use that as a design feature, not some amateur who wants to modify the initial design). Think about that. You're going to weaken the rim until it will flex like a piece of paper. The rim Aluminum thickness is far too thin to be cutting holes everywhere. Typical load bearing structures that have holes cut in them to save weight are far beefier than a wheel rim and are considerably overbuilt with supporting trusses. There's tuning aesthetic non load dependent pieces and then there's tuning significant load dependent functional parts. This is the latter. And yes, you will likely endanger your life if you do this.

I am an mechanical engineer by trade. This is an INSANE thing to do. Don't do it unless you are prepared to die. I'm not even joking.

jsinclair
Posts: 397
Joined: Sat Aug 27, 2011 3:26 am
Location: Sydney, Australia

by jsinclair

Here is a legitimate idea. Sell your R-500's and buy a lighter set of wheels. That way you will save on grams and dentistry bills.

kai-ming
Posts: 97
Joined: Mon Dec 03, 2007 12:53 pm

by kai-ming

justkeepedaling wrote:We are talking about stiffness to resist stress aka resist plastic deformation. You're just asking for your wheels to taco and fold. There has never been a design of road bike wheels in production with holes drilled in between every spoke (and that's even considering they use that as a design feature, not some amateur who wants to modify the initial design). Think about that. You're going to weaken the rim until it will flex like a piece of paper. The rim Aluminum thickness is far too thin to be cutting holes everywhere. Typical load bearing structures that have holes cut in them to save weight are far beefier than a wheel rim and are considerably overbuilt with supporting trusses. There's tuning aesthetic non load dependent pieces and then there's tuning significant load dependent functional parts. This is the latter. And yes, you will likely endanger your life if you do this.

I am an mechanical engineer by trade. This is an INSANE thing to do. Don't do it unless you are prepared to die. I'm not even joking.

Hi there, I am an qualified mechanical engineer too i.e. Chartered Engineer. Please explain to me why you wouldn't worry about the valve holes which go through both bridges of the rim, while you worry other hole on the lower bridge only. I understand cutting holes will weaken the rim to an extend, but all these talk about explosion of the wheel is just exaggeration. I have not heard of tests on the strength of rim at the valve hole. Enve worry about the strength at spoke holes, so they do test on that http://www.bikeradar.com/gallery/articl ... 96/?img=31" onclick="window.open(this.href);return false;
I suppose the thickness of lower bridge has been designed to have the strength to take the force of spoke, therefore it could be considerably overbuilt in between spokes. Proof me wrong if you have better answer i.e. testing/calculations/computer modelling that you have heard of on this subject.
Last edited by kai-ming on Sat Jun 30, 2012 10:35 am, edited 1 time in total.

kai-ming
Posts: 97
Joined: Mon Dec 03, 2007 12:53 pm

by kai-ming

jsinclair wrote:Here is a legitimate idea. Sell your R-500's and buy a lighter set of wheels. That way you will save on grams and dentistry bills.

I probably have not explain myself clearly. The R500 was brought with the intention to experimenting on tuning of a heavy cheap rim, so that has to be a heavy rim. I don't think there will be anything bad happen to my teeth.

kai-ming
Posts: 97
Joined: Mon Dec 03, 2007 12:53 pm

by kai-ming

kai-ming wrote:I suppose the thickness of lower bridge has been designed to have the strength to take the force of spoke, therefore it could be considerably overbuilt in between spokes. Proof me wrong if you have better answer i.e. testing/calculations/computer modelling that you have heard of on this subject.

As a matter of fact, Mavic think their rim is considerably overbuilt in between spokes, so they do ISM3D to their rim.:smartass: http://roadcycling.mavic.com/en/technol ... hno__ism3d

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DMF
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by DMF

In fact trials riders use rims with massive holes drilled all the way thru in between the spokes, and those are fairly plain rims with no extra features or reinforcements to make that possible, they're just plain simple drilled holes. And well, if a trials rider don't taco their rims - and believe me they both punish their rims AND put down a serious pedal kick for acceleration... well then I just don't see a roadbike rider doing it either.

In the early 90's it was, well maybe not common but atleast not unusual, to drill your own MTB rims in between spokes the DIY way, and they held up just fine.

But I think weight wise you might do better with shaving (á la Mavic) than drilling, if you can just find a way to tell exactly how much you're shaving off. I remember someone did the math on that on another forum a couple years back, and shaving actually takes away more material than drilling would (when all things done within reason). Still tough, we are talking savings in the 15-25 grams range per rim, at best.

BobSantini
Posts: 292
Joined: Sun Jul 10, 2011 9:03 am

by BobSantini

Hyperbole aside there are some simple structural principles to consider. Side to side (lateral) stiffness depends mainly on the sidewalls. The spoke bed and rim bed are not highly stressed in this loading mode. However loading in the vertical plane is resisted most by the material at the extreme top and bottom of the rim section i.e. at the bead hooks/brake tracks and the spoke bed. Putting a row of holes through the spoke bed will certainly compromise the vertical stiffness and strength to some degree. How much I couldn't say.

As far as vertical compliance is concerned, so called 'soft riding' rims actually don't flex very much and probably not significantly. In other words the soft ride is much more a function of tyre pressure and seat stay/seat post/seat flex. If a rim flexes significantly spoke tension fluctuates significantly through the load cycle. If it's too much it leads to spoke fatigue failure. Also the rim itself is setup for early fatigue failure so a flexible rim is not a good thing generally.

If you were to drill a line of holes through the spoke bed between the spokes there is a very real danger of cracks initiating at the drilled holes and going up the side walls. And just because the rim survives for some months/years does not mean it wont happen. The longer the rim is ridden the closer it comes to failure.

That said heavy rims are heavy partly because its cheaper to build them that way and partly for reliability for heavy riders, so they are somewhat stiffer/stronger than they need to be. With that and your light weight in mind I think it would be safe to drill the holes. If you do you should take care to leave ample web between the holes, don't drill near the spokes and make the holes smooth to avoid stress risers.

I googled for drillium and found only 1 reference to drilling rims. That was a fat tyre mtb rim with heaps to spare. Even so I think its obvious that the author has forgone a lot of rim life. If you look at the distribution of material around the spoke heads you can imagine that with a bit of cyclic spoke tension the web between the holes will fail. Many of the examples of drillium you will find on the web are stupidly fragile. Its a pity they dont post the failure photos.
http://fat-bike.com/2011/11/tech-drilling-fat-rims/" onclick="window.open(this.href);return false;

In summary I wouldn't do it myself because there is little to gain and potential for dangerous failure. Regular inspection should reveal incipient cracks, but then again it could happen very quickly. I'd sell them as they are and build some light weight clinchers if I were you. That way you learn some handy skills and acquire some cheap light wheels. You can build a set at ~1300g for about $300 materials cost not including tools.
r o y g b i v

kai-ming
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Joined: Mon Dec 03, 2007 12:53 pm

by kai-ming

Alright, SIT TIGHT! :mrgreen:
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Phill P
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by Phill P

you could start small to start with if you really want to do this....

justkeepedaling
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Location: by Crystal Springs (Sawyer Creek Trail)

by justkeepedaling

Do it, drill that sucker. Do it for the lulz

jsinclair
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Location: Sydney, Australia

by jsinclair

I can tell by the super accurate cutting line that a lot of technical thought has been put into this.


+1. Lulz will be had.

Andrew69
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Joined: Thu Feb 19, 2009 10:52 am

by Andrew69

justkeepedaling wrote:Do it, drill that sucker. Do it for the lulz

And make sure you have someone take a video of you on your first ride with them :thumbup:

Phill P
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by Phill P

:thumbup: :beerchug: :popcorn: :faint:

liam7020
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by liam7020

Appears like it's going to be a nice neat professional looking job...
Belgian Flag S-Works Tarmac viewtopic.php?f=10&t=144553

"Sometimes you don't need a plan. You just need big balls." Tom Boonen

Zakalwe
Posts: 433
Joined: Sun Jun 17, 2012 3:15 pm

by Zakalwe

Why even ask the question when you intend to do it anyway and dismiss every answer that explains why it's a bad idea? Baffling.

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