Wheels

[XS1100carbon]

Has anyone ever had any luck finding other wheels to use or lightening the original ones? Seems to be a lot of extra weight on these wheels that could come off. Such as in the middle of each spoke.

[natemoen]

I have taken the center ridge off of rim. I don't think I would risk taking the middle of the spokes out. I think that is just asking for a rim failure.

You have to remember, these rims are just crappy sand cast rims.

[WMarshy]

I've thought about throwing some holes through the middle web before... That would be an alternative to cutting the entire web out, and it would maintain its structural rigidity. Still a gamble if the web has porosity it could be compromised further by adding the hole.

[TopCatGr58]

I remember a similar discussion, and someone pointed out that the XJ swirly spoked wheels are also just cast, but they are thinner and smaller/narrower in the spokes, and swirly/bent, and they still hold up to the stress.

Another option is going with newer/lighter brake rotors. Others have done some serious drilling of the rotors.

I'm no structural engineer, but I've seen many parts on racing vehicles with the holes drilled into them to lighten the weight and maintain structure and functionality. It looks to me like the strength of the spokes is in ribs/edges and not necessarily in the web section....but what do I know??

T.C.

[crazy steve]

These are pretty poorly cast wheels....

The majority of the weight in these is in the outer rims and hubs, the two places you need to be very careful about removing strength. The little bit of material you can remove safely won't materially change the overall weight much. With that said, I think you could drill the spokes if you don't get crazy but the weight savings would be minimal.

I heavily modified a set of wheels....





... mostly for appearance; the weight savings is only ounces and given the amount of work involved, not worth it if that's the main reason. I can tell you I'll never do another set like this; too much work!

Want to save some unsprung weight? Find some lighter rotors to replace the 6 lb dinner plates these come with. You can buy them, but they're not cheap...

[XS1100carbon]

Wheels

Those look great steve, now just think if you removed the webbing too.A whole different wheel comes out.I already have EBC rotors on Carbon.They took off a bunch of weight.Anyone make custom wheels for these bikes?

[Eveready1100]

Just for the record, my original tube type wheels off my 78E (manufactured by Enkei) are the heaviest.
My tubeless rims off my SF weigh in at 1 lb less each.
Discussion on the Aussie site have found the spoke width and minor differences in the centre hub casting is where the weight saving is between the two types.
And the swirly wheels off an XJ are another pound lighter each.
The swirly wheels were fitted to the RH and 5K7 Sports models but were 17" on the rear as opposed to the XJ's 16 incher.

Another option would be to have a peek on the Yamaha triples sites to try to glean some info off them, as the 18" rear wheel would have to be different again and the front wheel could be of the lighter build design.

[TopCatGr58]

Okay, I did a bunch of research, and realized how much I do NOT know about a lot of stuff!!! Structural design, stress, beam design, theory, etc., etc.!

The spokes are an I-beam design, but act like columns, not like bike tire spokes because they are not under tension. The front spokes are longer, reference Steve's photos above, they are also tapered, and I did some measurements with my calipers.

The Webbing is appx. 5mm thick, spoke web is ~14mm wide at rim, and widens to ~25mm at the hub, it's appx. 160mm long. I calculated allowing ~5mm distance of holes from ribs, and from each other, and increasingly larger holes from narrow to wide section, minimum hole 8mm diam, max hole 14mm, would allow appx. 9 holes. One suggestion I read was to allow 1/2 of the width of the hole as space between the hole and the edge of the web for structural integrity!?
I found a site that provided the weight of alumiunum plate...a 1" sq 5mm thick piece was appx. 0.019 lbs, 0.3 oz! This was for 7075 material, cast might be heavier or lighter, but not by much!

I then calculated the area of each hole, added them all up, came up to about 900 sq mm's. 1 sq inch is ~625 sq mms, so the total amount of material removed with the drilling would be appx. 1.3 sq. inches, which would be about 0.4 oz!!!!!!! I've put on balancing weights heavier than that!
DOH...I forgot to multiply that by the 7 spokes, so that raises it up to a whopping 2.8 oz!!!

So...even though I found lots of interesting info on I-beams, material strength, stresses on I-beams, stress patterns in plates with holes as well as I-beams, etc., I won't post it because the amount of weight reduction doesn't seem to be worth the effort.

T.C.

[crazy steve]

TC was willing to do the math....

I doubt that even if you could find a lighter wheel (excepting the exotic big $$$ aftermarket ones) that the weight savings would be very much. And there would be that nagging thought that a lighter wheel will likely be off a lighter bike and may not be up to the weight of the XS.

[WMarshy]

Okay, I did a bunch of research, and realized how much I do NOT know about a lot of stuff!!! Structural design, stress, beam design, theory, etc., etc.!

The spokes are an I-beam design, but act like columns, not like bike tire spokes because they are not under tension. The front spokes are longer, reference Steve's photos above, they are also tapered, and I did some measurements with my calipers.

The Webbing is appx. 5mm thick, spoke web is ~14mm wide at rim, and widens to ~25mm at the hub, it's appx. 160mm long. I calculated allowing ~5mm distance of holes from ribs, and from each other, and increasingly larger holes from narrow to wide section, minimum hole 8mm diam, max hole 14mm, would allow appx. 9 holes. One suggestion I read was to allow 1/2 of the width of the hole as space between the hole and the edge of the web for structural integrity!?
I found a site that provided the weight of alumiunum plate...a 1" sq 5mm thick piece was appx. 0.019 lbs, 0.3 oz! This was for 7075 material, cast might be heavier or lighter, but not by much!

I then calculated the area of each hole, added them all up, came up to about 900 sq mm's. 1 sq inch is ~625 sq mms, so the total amount of material removed with the drilling would be appx. 1.3 sq. inches, which would be about 0.4 oz!!!!!!! I've put on balancing weights heavier than that!
DOH...I forgot to multiply that by the 7 spokes, so that raises it up to a whopping 2.8 oz!!!

So...even though I found lots of interesting info on I-beams, material strength, stresses on I-beams, stress patterns in plates with holes as well as I-beams, etc., I won't post it because the amount of weight reduction doesn't seem to be worth the effort.

T.C.

If I had more time this post would be a little more constructive but, I wanted to point out that even though a weight savings of only 2.8 oz seems small it will translated into noticeably less force to turn the front wheel to overcome the inertia force from it. If you dont believe me, go add two 1.5 oz wheel weights to your front time 180 degs apart from each other and go for a ride.

[WMarshy]

If you have the time and interest, you can figure out the force required to overcome the inertia of our front wheel at some speed. Then adjust it for the lightened wheel to see the difference... Obviously this wont be exact but could give you some insight as to the impact the change in weight will have...

http://www.inertia-calc.com/

[TopCatGr58]

Hey Marshy,

Okay, you talked me into it! Surprisingly while I was looking for a post/thread that told the WEIGHT of our wheels/rims so I could "Play" with that inertia calculator, and I came across this 2+ y/o thread that YOU started on this same topic!
http://www.xs11.com/forum/showthread...ight+front+rim

And Steve, you stated that you were able to "shave" off some 10-12 ounces from the weight of those polished rims....now that is a substantial amount of weight reduction vs. the lightening holes....albeit a considerable amount of work! BTW, can you tell me how much the rims weighed before and after the smoothing?

In it you spoke(pun intended) about a program that would allow you to create a CAD rendering of our wheel/rim, and then perform some FEA stress type measurements on it....did you ever get to do that??

Another point I brought up, was not only are the XJ wheels spokes swirly but they do NOT have any webbing between the pairs of spokes in them...see photo below for reference!



SO...it seems to me that a majority of the strength of the wheel design is in the actual presence of the # of spokes/ribs, their thickness, and not so much on the webbing! In my reading about beams and stresses and such, the angled design of the swirly spoked wheels really does add stresses and weakness to the joints where the spokes attach to the rim and hub being on an angle vs. perpendicular, and yet they are strong enough to withstand both the bike's weight as well as the torque forces of both accel for the rear wheel as well as the braking torque forces of both front and rear!

Okay, here goes: This first link on Wikepedia describes the old hot rod technique of lightening holes, but says that it was banned way in the early 1920's or so because of the failures that were seen...but these were holes that were put in FRAME and AXLE type components!
http://en.wikipedia.org/wiki/Lightening_holes

Next are some quotes from various articles I found regarding beams and such:

An I-beam is a beam with an I- or H-shaped cross-section. The horizontal elements of the "I" are flanges, while the vertical element is termed the "web". The web resists shear forces, while the flanges resist most of the bending moment experienced by the beam. Beam theory shows that the I-shaped section is a very efficient form for carrying both bending and shear loads in the plane of the web. On the other hand, the cross-section has a reduced capacity in the transverse direction, and is also inefficient in carrying torsion, for which hollow structural sections are often preferred.

A beam under bending sees high stresses along the axial fibers that are farthest from the neutral axis. To prevent failure, most of the material in the beam must be located in these regions. Comparatively little material is needed in the area close to the neutral axis. This observation is the basis of the I-beam cross-section; the neutral axis runs along the center of the web which can be relatively thin and most of the material can be concentrated in the flanges.

Though I-beams are excellent for unidirectional bending in a plane parallel to the web, they do not perform as well in bidirectional bending. These beams also show little resistance to twisting and undergo sectional warping under torsional loading. For torsion dominated problems, box beams and other types of stiff sections are used in preference to the I-beam.

Now, our spokes are I-beams that are fixed at both ends, so they are not susceptible to torsional/twisting type flexing. The Neutral Axis is essentially right down the middle of the webbing between both thick ribs/flanges of the spoke/beam.

This image shows the stresses on beam that is secured/fixed on only 1 end, and the other end is allowed to flex/torque, and you can see the stress loads being concentrated down the ribs/flanges, with very little in the center webbing.



This next image shows the stresses thru a beam when a bending load is being placed in the direction/plane of the webbing.



This type of stress/load IS exerted on our spokes during braking and for the rear wheel, acceleration.

This next image shows the concentration of stress forces thru a PLANE....not an I-beam when a hole is placed in the middle of the PLANE! And it's at these concentrations of stress forces/lines where stress fractures/cracks can occur.



However, with an I-beam a majority of the stresses are born by the ribs/flanges and not the PLANE of the webbing as shown in this next image. The neutral Axis is vertically down the middle of the beam denoted by the dashed black line.

A material's strength is dependent on its microstructure. In general, the yield strength of a material is an adequate indicator of the material's mechanical strength. Considered in tandem with the fact that the yield strength is the parameter that predicts plastic deformation in the material, one can make informed decisions on how to increase the strength of a material depending its microstructural properties and the desired end effect. Strength is expressed in terms of compressive strength, tensile strength, and shear strength, namely the limit states of compressive stress, tensile stress and shear stress, respectively. The effects of dynamic loading are probably the most important practical consideration of the strength of materials, especially the problem of fatigue. Repeated loading often initiates brittle cracks, which grow until failure occurs. The cracks always start at stress concentrations, especially changes in cross-section of the product, near holes and corners.

It has been stated that holes would stop a stress crack from spreading thru a material, but the last bolded statement above seems to contridict that? That said, as has been stated with the earlier I-beam strength characteristics described, the webbing provides very little strength to the I-beam design of our spokes on our wheels, and so it does seem to me that placement of lightening holes...when well spaced both from the edges of the ribs/flanges as well as each other would not be detrimental to the overall compressive strength of the rims, and due to the thickness of the ribs/flanges and the additional external webbing on the spokes to Rim/hub junctions provide adequate strength against the shear/torque forces exerted with braking/accel, and would not be significantly weakened by the lightening holes in the central webbing. As always...YMMV!

T.C.

[XS1100carbon]

webbing

Sounds like I need to find an cnc machine and have the web removed plus what steve had taken off.Now that would be a nice looking wheel.As far as a stress test,Sometimes you just have to go for it(WFO).Have one wheel maker checking about a custom set but i'm sure there big bucks.

[donebysunday]

Wow

T.C. awesome !
I was going to drill holes and clean the edges but just about that time I saw a bunch of folks beat me to it. So I ended up just slightly drilling the rims where the spokes meet them.

[crazy steve]

TC, I doubt if I cut any more than 6 oz off either wheel. I didn't weigh the 'after' product (and they now have tires mounted) but I couldn't feel any appreciable weight difference.

And if trying a CNC machine to cut on these, be aware that they're really not very precise castings. Mine were all hand work, and the amount of 'blending' I had to do to get rid of mold shift and differences from one side to the other were pretty extensive. I found almost 1/8" of variation in finished rim thickness on the front wheel (obvious heavy spot), and the rear wheel had issues with how well the pattern was 'centered' in relationship to the outer rim... on just one side!