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Discussion in 'Airheads' started by Airhead Wrangler, Dec 24, 2008.
DAmn. D A M N.
Rev it up. .
Some poeple have all the luck.
I have a 32:10 with a gs tubeless rim, about to be machined ala sbocher to throw on for some cruising. Im going to machine the hubb soon and will use the dimensions on sb' s thread but wanted to ask, given manufacturing tollerances, what to people suggest to be the ideal gap between hubb and bevel box?
I would measure the exisiting gap (mono hub and FD, or paralever hub and FD) and use that. The gap itself isn't really a gap. There is a set of ridges on the FD and a single ridge on the hub ... and they 'fit together'. So, if you keep the same tolerances, you will find that they fit together and the brake pad lands on the shoe correctly. If you go a bit bigger, you will allow sticks and other crap to have access to the inside of the hub.
But you probably won;t have to grind off 2mm off the spoke mounts in the hub
See the last couple pages in the linky in my signature for an explanation.
Spencer ... back to you.
No, carry on... I need this info too.
So you are saying we have an option of milling the spokeholes a bit... Or just adding a spacer to offset the hubb... Hmmm....let me think. I may off set the hubb and add a ring or something to take up the gap that it creates. Hmmmm.. AW, fancy trying something first?
OK ... This is what happened to me when I did this (FYI - The GSification thread in my sig is about to get a big update that directly concerns this).
I had an expert mill the hub, and he milled it correctly. He took off the amount of material mentioned in Stephen Bottchers writeup (21.5mm) (http://www.stephenbottcher.net/BMW/rearconv.htm) When I got the hub back, I put it on the mono-FD and it was sticky, and when torqued to the proper force, it was stuck. Wouldn't move. At all.
So ... I re-read Stevens writeup and really poured over the pictures. Then I saw this:
Do you see how the nipple mounts have been ground off a bit? Stephen doesn't mention this in his write-up. The Mono-lever hub doesn't have those mounts ... So he just took about 2mm off of them.
when I tried to do it (without grinding) It was that area in whick I was rubbing:
You can see the unground hub here, and where it was rubbing:
So ... It really is easy ... and structurally it still holds the spokes really well. I was very concerned at first, but once I saw what Stephen did, I took a dremel tool to it and haven't looked back.
PS - YES! I did it with a Dremel tool. When you put the tire on, you're going to balance it anyway ... right? Also, I will be running a 32:10 FD with the 18" wheel. This will be approximately the same overall ratio as a 33:11 FD with a 17" wheel.
PPS - If you put in a spacer in between the hub and the FD you will do two things that I think would be a negative ...
1. You will add another 'mating surface'. Hub to spacer, spacer to FD, instead of just Hub to FD. Yet another place for the joint to slip, and making a greater span for the bolts holding it together to take.
2. You start moving the brake pad off the brake shoe. Over time, the brake pad and shoe will start having 'shoulders' and get sticky ... might not release as well, or will lock up prematurely.
Makes sense... Thanks for sharing your experience. I was really hoping i could avoid re lacing my hubb and rim but it appears unlikely. I guess i can get it relaced offset a bit so i can then fit a 140 trye. Ill ask my machinist to do everything.
So the head of a spoke will fit neatly in the holes where the nipples go in the hubs? I plan to use an excel 18" rim on this rather than a cross-spoke BMW rim so I'll use conventional lacing with the nipples in the rim rather than the hub. Do the ends of these holes have a conical shoulder to fit a straight nail spoke like those used on monolever G/S rear wheels? Thanks for the writeup and pics.
I'm having someone do the lacing... he's a friend and well known in the Atlanta British Iron scene. Anyway, he said that I'd have more success using the cross laced rims because of the way the angles of the nipple seats were in the hub. They're flat ground and pointed at a specific direction instead of a ball as I had thought. So yes, those holes have conical shoulders to fit straight spokes. (And that is the way that Stephen Bottcher did it.)
Also ...because we were 'grinding off 21.5mm' at the beginning of this endeavor... we are already 'offestting' the wheel 21.5 mm. So, I am opting for only 6mm more offset than the 21.5mm already there... so the biggest tire I will be able to put on it will be a 130.
Is Eric doing it?
OK, so now I'm confused. I just had a look at the rear wheel on my GSPD and the holes where the nipples come out are REALLY fat. I measured them at 7mm. How is a spoke going to stay in there when laced conventionally?
Yep. He has questionable morals and friends... but he knows his shit.
OK ... define 'flat'. And 'laced conventionally'. The way it was explained to me was that those nipple mounts in the hub 'point' to a specific place in space. And that place is not the center of the rim ... it's the edge.
'Fat' not 'flat'. 7mm is extremely fat for a spoke. Conventionally laced as in not a cross spoke wheel. BMW cross spoke wheels have the spoke heads in the rim and the nipples in the hub. Everyone else does it the other way around.
It looks like Stephen solved the problem with spokes that have REALLY fat heads. Frankly, I'm not terribly shocked that this rim cracked. Look how every nipple is at a different angle from the spoke that goes into it. I dimpled rim is really necessary here due to the relatively shallow angle at which the spokes enter the rim.
It looks like HPN does this by using dimpled rims and some sort of insert in the hub to hold the spoke heads as their spokes don't have huge flared heads on them. Actually, now that I look a little more closely it looks like maybe they have spokes that are threaded on both ends, using the stock cross-spoke nipples in the hub AND conventional nipples in the rim. I might need to call Klaus about this. Weird.
OK I'm seeing this now ... and in the previous pic, you can really see the nipples bending at the hub ... scary. Please let me know what Klaus says ... I will drop by Eric's shop and see how he's coming ... I gave him fair warning that this was going to be a challenge.
Have you got any links/info on what's required to do this? I'm kinda partial to that under-seat toolbox. My G/S hub is about shot and it's not worth the money to pay the outrageous prices people want for them.
You want to put a paralever on your bike?!? I'd look for a different monolever final drive and convert a later 4 lug wheel if I were you... well, even though I'm not you I'm still doing that for the ST to run a higher final drive ratio. I'm guessing that end up being cheaper than all the mods necessary to run a paralever.
Getting wheel's built here is just so expensive. I don't want to put $1000 in to it and then end up with the same drum brake I had before. I certainly don't mind any effort it takes.
I think I could make that bracket for the center shock mount myself but I don't want to lose the storage.
I guess I'll stick to what I usually do. I'll wait to see what you figure out in your Para-Curious thread and use all your ideas
I'm a few years from this anyways. I gotta graduate to get money and the first thing I want is a WP front end. I might be able to get the fork this year but it'd take my road trip money. I'm not missing a bike trip for bike parts.