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rider
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Discussion Starter · #1 ·
Just wondering if anyone has had their hands on the new KH rims. His website says the new rims have an offset spoke bed. Weight is supposed to be slightly down from before due to larger drill outs on the inside wall of the rim.
 

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29erchico said:
Just wondering if anyone has had their hands on the new KH rims. His website says the new rims have an offset spoke bed. Weight is supposed to be slightly down from before due to larger drill outs on the inside wall of the rim.
I don't think that Kris is defining OSB in the same way that we do or would like him to. But I hope I'm wrong. Link to what you saw?
 

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rider
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Discussion Starter · #3 ·
Not much info yet, but these two links will show you what there is:

http://www.krisholm.com/khu/rims

Check item #8 here:

http://www.krisholm.com/khu/news/206

I emailed KH for more info, like how much lighter than the old 29er rims. I'll post the reply here when it comes in.

I remember a while back KH himself came on the 29er board and ask us what we wanted and he was talking about a lighter rim offering at the time...
 

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29erchico said:
Not much info yet, but these two links will show you what there is:

http://www.krisholm.com/khu/rims

Check item #8 here:

http://www.krisholm.com/khu/news/206

I emailed KH for more info, like how much lighter than the old 29er rims. I'll post the reply here when it comes in.

I remember a while back KH himself came on the 29er board and ask us what we wanted and he was talking about a lighter rim offering at the time...
OK. I'm not 100% certain here, but I *think* that Kris' idea of OSB is to offset the spoke holes to *both* sides of the centerline of the rim. Keep in mind that Muni's rarely use disc brakes, so offsetting the spoke holes the way we do for disc wheels offers no advantage for a rim-brake muni wheel. Make sense?

I'm basing my guess on the fact that I got one of these rims as a sample over a year ago, and (upon opening the box and seeing the drilling) instantly realized that when Kris and I had been conversing about "OSB", we each held a very different picture in our minds about what it meant.

I hope that I'm wrong here and that the KH OSB rim is all that and a bag of chips for aggressive (or heavy, or both) big wheel riders. But I don't think that's the case...

MC
 

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rider
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Discussion Starter · #5 ·
Hmmm, see what you are talking about. But, and this is going out on a limb a bit, if the orientation of the dual offset spoke beds were aimed so that a spoke that was anchored on the right side of the hub inserted into the left side of the rim, and visa versa, would not the bracing angle be increased? Would this not be an advantage to both a non-dished wheel (as found on most Muni's) and also dished wheels as found on most mtb's currently?
 

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Harmonius Wrench
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29erchico said:
Hmmm, see what you are talking about. But, and this is going out on a limb a bit, if the orientation of the dual offset spoke beds were aimed so that a spoke that was anchored on the right side of the hub inserted into the left side of the rim, and visa versa, would not the bracing angle be increased? Would this not be an advantage to both a non-dished wheel (as found on most Muni's) and also dished wheels as found on most mtb's currently?
It would make matters worse on the dished side of the wheel. Your spokes would nearly be perpendicular to the rim at the spoke hole looking at the wheel from the front. Hardly any angle would be there going from the rim to the hub. Lateral stiffness would be compromised, in my opinion.
 

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rider
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Discussion Starter · #7 ·
Guitar Ted said:
It would make matters worse on the dished side of the wheel. Your spokes would nearly be perpendicular to the rim at the spoke hole looking at the wheel from the front. Hardly any angle would be there going from the rim to the hub. Lateral stiffness would be compromised, in my opinion.
I don't think you are visualizing what I had in mind. Think of the axle of the front wheel as defining the x axis in the ever popular Cartesian coordinate system. Then imagine the x zero point on that line to be defined by a plane thru the centerline of the rim. Then we suppose that KH has offset half of the spoke holes to the position of -10mm along to the x axis and the other half are offset to +10mm. But each of these rows of offset spoke holes are aimed at the flange at the opposite side of the hub, so that all the spokes will cross the centerline of the rim, not originate from the middle of it.

Let's say that this is a dished 29er front wheel using the Hayes/DT 20mm T/A hub that sits behind me at the moment as an example. It's flanges are about 56mm apart & the dish looks to be about 10mm. So the left flange would be sitting at about -38mm on the x axis and the right flange would be at about +18mm on the x axis. In my spoking scheme a spoke originating at the right flange,x=+18mm, would insert into the rim at x= -10mm, giving it a total slope of 28mm along the x axis.

Using the diameter of the old KH rims (ERD=604mm), but with dual OSB's, laced to the above hub as an example, the spokes would anchor into the rim at a point at x= -10mm, y= 302mm. A little right angle trig gives us and angle of 84.7 degrees if we define perpendicular to the x axis as 90 degrees. If we insert a spoke that also originated from the hub at x=+18 into a rim with all of it's spoke holes in it's centerline, x=0, and with the same ERD, we get an angle of 86.6 degrees and also closer to perpendicular so a less favorable bracing angle would result. Granted, for simplicity, I have assumed a hub flange diameter of zero so the above degree numbers are only rough.

I'm pretty sure that by spacing the two rows of offset spoke beds 10mm to each side of the rim's centerline we have given the wheel a better bracing angle equivalent to having hub flanges spaced 20mm farther apart. Not an original idea, BMW has been doing just this for years on it's GS series of mondo enduro street/dirt motorcycles.
 

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Hey,

Thanks for the comments and feedback on my rims. Yes I did define offset as symmetrically to either side of the rim centerline, not to one side, as unis don't have dished rims. Sorry if that confused you.

In my opinion, wheel strength with respect to offset spokes is not as simple as just the spoke angle, for wide rims.

That is particularly the case for the wider 47 mm KH rims in 19" and 24" size, and is most noticeable on a unicycle because the lateral force can be way higher than a bike, due to the way drops are landed (or screwed up!). In testing, offset spokes (no dish) resulted in a more durable rim for the wide rims. I think that is because on a wide rim, force is not simply on the rim centerline; there is significant twisting force on the inside sidewall (inside with respect to the direction of force). That means that there must be a compromise between spoke angle and supporting the rim across its entire width. Hence the need for offset spokes. On a 700c rim, the slight offset doesn't have nearly the same influence on spoke angle as a bigger offset does on smaller diameter 47 mm wide rims.

Since unis don't have dished rims, I never tested it in that setup so would be interested in your feedback. Spoking across to the opposite offset spoke is an intriguing idea; haven't tested that either but it would be interesting to try.

By the way, I don't know if this would be useful in the biking world, but 36h x 47 mm wide 700c KH rims will become available in Spring'09.

Kris Holm
 

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rider
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Discussion Starter · #12 ·
So are these OSB's angled outward towards the hub flanges? If they are, it may eliminate the possibility of spoking across to the opposite offset, as you call it, as it could cause a bending of the spoke just as it enters the nipple.
 

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29erchico said:
So are these OSB's angled outward towards the hub flanges? If they are, it may eliminate the possibility of spoking across to the opposite offset, as you call it, as it could cause a bending of the spoke just as it enters the nipple.
If you did this I think it would mess up the placement of the valve stem. I think you'd be rotating the rim one spoke hole from the correct placement thus putting the valve stem in a pair of spokes that are angled toward each other. Probably not a big deal, but worth looking at.

And the hub label would be off too. Seems like if it would help, it would have been done already.
 

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Harmonius Wrench
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29erchico said:
I don't think you are visualizing what I had in mind. Think of the axle of the front wheel as defining the x axis in the ever popular Cartesian coordinate system. Then imagine the x zero point on that line to be defined by a plane thru the centerline of the rim. Then we suppose that KH has offset half of the spoke holes to the position of -10mm along to the x axis and the other half are offset to +10mm. But each of these rows of offset spoke holes are aimed at the flange at the opposite side of the hub, so that all the spokes will cross the centerline of the rim, not originate from the middle of it.

Let's say that this is a dished 29er front wheel using the Hayes/DT 20mm T/A hub that sits behind me at the moment as an example. It's flanges are about 56mm apart & the dish looks to be about 10mm. So the left flange would be sitting at about -38mm on the x axis and the right flange would be at about +18mm on the x axis. In my spoking scheme a spoke originating at the right flange,x=+18mm, would insert into the rim at x= -10mm, giving it a total slope of 28mm along the x axis.

Using the diameter of the old KH rims (ERD=604mm), but with dual OSB's, laced to the above hub as an example, the spokes would anchor into the rim at a point at x= -10mm, y= 302mm. A little right angle trig gives us and angle of 84.7 degrees if we define perpendicular to the x axis as 90 degrees. If we insert a spoke that also originated from the hub at x=+18 into a rim with all of it's spoke holes in it's centerline, x=0, and with the same ERD, we get an angle of 86.6 degrees and also closer to perpendicular so a less favorable bracing angle would result. Granted, for simplicity, I have assumed a hub flange diameter of zero so the above degree numbers are only rough.

I'm pretty sure that by spacing the two rows of offset spoke beds 10mm to each side of the rim's centerline we have given the wheel a better bracing angle equivalent to having hub flanges spaced 20mm farther apart. Not an original idea, BMW has been doing just this for years on it's GS series of mondo enduro street/dirt motorcycles.
Gotcha! (See Shimano road rims from about six years ago) I think it has validity. It would make for an interesting experiment.
 

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Harmonius Wrench
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Kris Holm said:
Hey, it is amazing how much burlier this rim makes the tire feel. Testing has been with a WTB Stout and it feels way bigger volume with way more sidewall stability.

Kris
Well, I know a bunch of us snow bound 29"er freaks that would be very interested in that 47mm wide rim!

Yeah, I'll bet that rim does wonders with a Stout. Very cool and thanks for dropping that on us. Hey, one more question: Will QBP distribute those? (I'm hoping so, and I'll bet alot of us other bike freaks are too. ;) )
 

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29erchico said:
So are these OSB's angled outward towards the hub flanges? If they are, it may eliminate the possibility of spoking across to the opposite offset, as you call it, as it could cause a bending of the spoke just as it enters the nipple.
Yes- good point. So I don't thing spoking across to the opposite offset would work.

Kris
 
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