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 Post subject: Mismatched hub/rim
PostPosted: Wed Jun 27, 2012 1:05 pm 
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Joined: Wed Jun 27, 2012 2:44 am
Posts: 5
I was hit by a car and my front wheel was run over. The rim and about 10 spokes where ruined, but the hub seems fine, so I'll reuse that. The weight weenie bug has hit me now that I need to buy some new parts (replaced the stem, bars, and fork too from the accident), and I would like to run less spokes.
The wheel was an H+son rim laced with straight gauge spokes to a dura ace 7600 hub, so it was quite heavy, 1140g for just the front according to my postage scale. I have a few options I'm looking at and am wondering what kind of advice within those options you guys can give.

I'm going to replace the rim with a kinlin xr-270, which will drop the weight by itself is 180g.
Buying much better Sapim laser spokes which drops the weight 110g.
And the kicker, I want to lace the front 24h, which drops another 50g and means buying less spokes lol.

So yeah, a 36h hub laced to a 24h rim. I know it's been done before, by quite a few people. Sheldon Brown has an example of one on his site. The wheel was laced 3 leading 3 trailing, and I think the general pattern can be kept while just removing some of the spokes in it, making it a 2 leading 2 trailing.

The original 3 leading 3 trailing: Image
If I were to remove the outside two spokes from the design to fit a 24h rim: Image
If I were to remove the inside two spokes instead: Image

Or I could simply use a radial lace, although I'm hesitant to relace a hub radial after it already has about 4k miles on in another pattern, since I know relacing a hub in a different pattern than was originally used on it it a nono, and radial lacing a hub is a questionable, and lacing a hub skipping 6 holes on each side is a questionable. nono+questionable+questionable = probably avoid that.

As far as spoke length, 2 leading 2 trailing uses 2x spokes. I can't quite wrap my head around how having a few more holes in the hub would change that length. Would it make the spokes a few mm shorter on the skipping outside version since they are slightly closer to the rim where they lace, and inversely a few mm longer on the skipping inside version since they are slightly further away?

And which version seems like it would stress the hub less? I'm inclined to believe the skipping outside holes version because it gives some empty space on the outside of the pattern, so the tension of those last spokes can be spread out over a bit more flange. Does anyone see any real issues doing this?

Edit: sorry everything looks so dirty. I've been waiting for a reason to clean the hubs and spokes. Since I'm getting a fresh rim and spokes both in silver, I'll strip the paint off the hub and polish it again for a clean look once more. Don't worry, the bearings are kept in very good condition even though the outside is painted and dirty. I clean those things inside like 4-5 times a year.


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 Post subject: Re: Mismatched hub/rim
PostPosted: Wed Jun 27, 2012 2:25 pm 
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in the industry

Joined: Sat May 12, 2012 7:25 pm
Posts: 1602
Location: Glermsford, Suffolk U.K
Personally I would by a new hub - plenty of lighter alternatives out there. Also with many other hubs you can lace radially and keep the warranty.

Sell the 36H front hub to put some cash back in the kitty. It has to be worth something.

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 Post subject: Re: Mismatched hub/rim
Posted: Wed Jun 27, 2012 2:25 pm 


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 Post subject: Re: Mismatched hub/rim
PostPosted: Wed Jun 27, 2012 3:35 pm 
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Joined: Tue Sep 14, 2010 3:28 pm
Posts: 1405
The only way to build a symmetrical wheel with a 36 hole hub to a 24 hole rim is to use different lacing patterns on each side of the wheel.
Example.
Attachment:
complete.JPG
complete.JPG [ 55.43 KiB | Viewed 884 times ]

This works fine on a rear wheel but probably not so much on a front wheel :noidea:


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 Post subject: Re: Mismatched hub/rim
PostPosted: Thu Jun 28, 2012 12:15 am 
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Joined: Wed Jun 27, 2012 2:44 am
Posts: 5
bricky21 wrote:
The only way to build a symmetrical wheel with a 36 hole hub to a 24 hole rim is to use different lacing patterns on each side of the wheel.
Example.
Attachment:
complete.JPG

This works fine on a rear wheel but probably not so much on a front wheel :noidea:

Why would it work fine on a rear but not a front? A front wheel has less weight on it and no torsional torque from the gears.

That being said what about a 2 leading 2 trailing is not symmetrical? Assuming a standard 3 leading 3 trailing is symmetrical, which it would seem to be if it's using all the same length spokes and are mirroring the pattern between sides, this is the exact same design minus a few spokes.

And to the guy above, I know I could probably sell the front hub for enough to just buy a hub from bhs that weighs less and is 24h, but honestly I have a lot of nostalgia with these hubs. First ones I ever bought, first ones I ever laced, first loose ball bearings I cleaned. I'll probably replace the steel bearings with ceramic ones to cut some of the weight off and I could always buy a hollow axle for it, but I'm not toooo worried about weight on this bike, it's the next one that'll be my light weight baby.


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 Post subject: Re: Mismatched hub/rim
PostPosted: Thu Jun 28, 2012 12:40 am 
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Joined: Tue Sep 14, 2010 3:28 pm
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You can't do 2 leading and 2 trailing with a 36-24 combo. You simply cannot lace both sides of the wheel with the same pattern. It's math it just doesn't work.


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 Post subject: Re: Mismatched hub/rim
PostPosted: Thu Jun 28, 2012 1:59 am 
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bricky21 wrote:
You can't do 2 leading and 2 trailing with a 36-24 combo. You simply cannot lace both sides of the wheel with the same pattern. It's math it just doesn't work.

I kinda of beg to differ?

24 spokes is 12 per side. 2 leading 2 trailing creates groups of 4 spokes. 4 spokes per group into 12 spokes per side is 3 groups per side. This creates the same "tri spoke" look of a 3 leading 3 trailing on a 36 spoke design.

A 36h hub has 18 holes per side. 12 spokes leaves 6 empty spaces. 6 empty spaces divided between between 3 groups means 2 empty hub holes per grouping of spokes. Place those 2 holes either in the middle or at the ends of the groupings like I showed in the above pics and the spokes come out 2 leading, 2 trailing, 2 empty holes, repeat.

If I am missing something please let me know. I'm not trying to be argumentative I just literally don't see the problem with it.


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 Post subject: Re: Mismatched hub/rim
PostPosted: Thu Jun 28, 2012 2:52 am 
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Joined: Tue Sep 14, 2010 3:28 pm
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Which would be fine if you had a 24 hole hub and a 24 hole rim. If you try and draw it up and you'll see. If you do a search on here you can find and read my thread about building a 36-24 hole hub, and rruff answers all the questions your asking.


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 Post subject: Re: Mismatched hub/rim
PostPosted: Thu Jun 28, 2012 9:18 am 
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Joined: Wed Jun 27, 2012 2:44 am
Posts: 5
bricky21 wrote:
Which would be fine if you had a 24 hole hub and a 24 hole rim. If you try and draw it up and you'll see. If you do a search on here you can find and read my thread about building a 36-24 hole hub, and rruff answers all the questions your asking.

I'll read your thread, I'm sure it has a lot of helpful information in it.

As far as drawing it up, I found a template for 24 holes wheel and 36 hole wheels and just used photoshop to switch the hub out. I added color and drew in the spokes for 2 leading, 2 trailing, skip 2. Unless there are some small angles off that I'm not seeing it looks fine.
Image


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 Post subject: Re: Mismatched hub/rim
PostPosted: Fri Jun 29, 2012 4:44 am 
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Joined: Tue Sep 14, 2010 3:28 pm
Posts: 1405
That looks ok with that mock up,but only because it isn't laid out very precisely. Below, I drew up your pattern with one of my templates, added the angles, and blew it up so you can see that the corresponding spokes are coming of the hub at different angles on each side, and even worse if you look carefully you can see that all 4 yellow spokes are coming off at different angles. That is because you can only line up one side of a 24-36 build when using identical lacing patterns on each side.
Attachment:
111111111111111.JPG
111111111111111.JPG [ 66.47 KiB | Viewed 649 times ]


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 Post subject: Re: Mismatched hub/rim
PostPosted: Fri Jun 29, 2012 12:00 pm 
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Joined: Wed Jun 27, 2012 2:44 am
Posts: 5
Oh I see what you mean.

Is that a certain software you used or did you manually calculate those angles. Either way can you give some links to the program or the formulas you used. I'd love to be able to mess around with random designs and see accurate results. It's been 4-5 years since I took trig but I'm sure I could understand and use a formula.

And once again thanks for the help. Too many forums for bikes are just full of trolls and people who tell you that if you don't ride what they have you're stupid. :thumbup:


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 Post subject: Re: Mismatched hub/rim
PostPosted: Fri Jun 29, 2012 2:21 pm 
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Joined: Sat May 12, 2012 7:25 pm
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Location: Glermsford, Suffolk U.K
Having read Briky21's thread his solution looks good. Respet for putting the effort into finding a workable solution.

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 Post subject: Re: Mismatched hub/rim
PostPosted: Fri Jun 29, 2012 3:42 pm 
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Joined: Tue Sep 14, 2010 3:28 pm
Posts: 1405
unordinary wrote:
Is that a certain software you used or did you manually calculate those angles.


I just downloaded a free geometry program I found with google. Mine is GeoGebra. You'll have to mess around with it for a bit, but it has everything you need. The Spoke hole formula is simple "360 / #of holes" Example:A 24 hole rim has a spoke hole every 15 degrees (360/24=15).


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 Post subject: Re: Mismatched hub/rim
Posted: Fri Jun 29, 2012 3:42 pm 


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