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Discussion Starter · #1 ·
Trying to narrow up my rigid shovel and have been reading on here guys are boring out 39mm narrowglide tree's for 41mm tubes. Have any of you guys put any miles on this setup with good results? Just curious if any of these setups have been failing recently.

I bought a set of 39mm narrowglide with an aluminum lower tree and wanted to bore them out. 2mm isn't much of a material lost, just wanted to see if you guys had any updates.

Thanks
 

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Discussion Starter · #3 ·
i've got a set that have a lot of very hard miles on them (think tons of mexican "roads" and 2 up riding).
can't say i'd give mine a second thought, nor have i heard of any failing.
Yeah I've never heard of any failing except one guy told me his buddies cracked and he barely made it home. Could be full of shit for all I know.

Was just curious how the setup holds up over time.
 

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Couple things to think about.

You really only remove 1mm of material. That much all the way around makes the hole 2mm larger in diameter.

Fork stops. Most of the 39mm forks use two little stops on the lower tree, and a tab on the front of the frame. You can get a lower bearing cup with a tab on it, should be pinned to the frame when you install it. You could fabricate the tab and weld it to your frame. You could get a set of the hidden fork stops from Landmark or DNA, then smooth the stops off the lower tree for a cleaner look.

There are two ways to do the top tree. You don't have to bore it, you can make sleeves like the ones in post #68 of this thread http://www.jockeyjournal.com/forum/showthread.php?t=26910&highlight=39mm&page=4 Noodelz may still be making some.
Or you can bore the top tree and use the Custom Cycle Engineering fork tops which look like the 39mm ones but are made for the 41mm tubes. CCE makes them as part of their Tru Track triple tree sets, but you can buy them separately, part number 7LN-4100. (edit: correct part # FTN 4100)

And, if you're really worried about it, the very first 39mm forks had cast steel lower trees. '87 FXR I think.
 

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I ran a set for two years. Went to the smokeout in 2010. Around 3000 mile trip. Many miles before and after. This last summer some dipshit pulled out in front of me, I t-boned him at about 35. Bent the tubes around 45* but the trees are still good to go.
 

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Discussion Starter · #6 ·
Couple things to think about.

You really only remove 1mm of material. That much all the way around makes the hole 2mm larger in diameter.

Fork stops. Most of the 39mm forks use two little stops on the lower tree, and a tab on the front of the frame. You can get a lower bearing cup with a tab on it, should be pinned to the frame when you install it. You could fabricate the tab and weld it to your frame. You could get a set of the hidden fork stops from Landmark or DNA, then smooth the stops off the lower tree for a cleaner look.

There are two ways to do the top tree. You don't have to bore it, you can make sleeves like the ones in post #68 of this thread http://www.jockeyjournal.com/forum/showthread.php?t=26910&highlight=39mm&page=4 Noodelz may still be making some.
Or you can bore the top tree and use the Custom Cycle Engineering fork tops which look like the 39mm ones but are made for the 41mm tubes. CCE makes them as part of their Tru Track triple tree sets, but you can buy them separately, part number 7LN-4100.

And, if you're really worried about it, the very first 39mm forks had cast steel lower trees. '87 FXR I think.
Yeah I found that guy and PM'd him earlier.

Yeah I figured 2mm wasn't enough to worry about.

Thanks guys.
 

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gotta bring this back.. i am wanting to do the same, emailed the guy from the other post last week and still no reply.. so i was thinking i could just have a machine shop make them for me... all i would need is th OD of the top of the 41mm leg and the ID of the top tree, a slit in it so it can pinch, any idea of how thick the top flange area he had on them would need to be??? and then the flange is just the diameter of the milled surface for the fork tops.. just wanna be sure im understanding the dimensions of the bushing so i get it done right.
 

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I would make the OD of the bushing 39mm and the ID the same as the stem. I also wouldn't split the bushing just make it a nice tight fit on the stem.
 

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that seems to makes sense too seeing as how on the wide glides their not a pinch fit like the narrow trees, fork tops keep them from sliding down and their pinch fit on the bottom tree. the machine shop would just have to make sure the ID of the bushing hole is an exact, no slop fit.

Anyone else have an opinion on this?
 

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The way the Harley wide glide tubes fit into the stock wide glide top tree is not a particularly good design. Ever notice that no one else does it? The next time HD designed a hydraulic fork, for the K model, they did it the British way, fitted the tube to the top tree with a taper, better. Next redesign for the 39 mm forks, they clamped it to both trees like a ceriani, even better. (the Brits made the change to clamping in '71, HD waited 'til '87.)

I'm saying if you're going to go with the spacer inside the top tree, split the spacer and get that tight, no slop, clamped fit. For the spacer, o.d is 39mm, (the trees are designed to clamp on that diameter) i.d. a hair over 1" (measure your fork tops to be sure.) and thickness of 1 3/16" or so. (I measured two wide glide trees, an early one was 1 3/16" thick at that point, a later one was 1 1/8" and the 39 mm trees are 1 1/4". You can live without the flange on the spacer, but if you want it, thickness isn't really critical. Also, unless you're into patina, the spacer needs to be made of something that won't rust, or it has to be painted/plated/whatever.

I still think the CCE fork caps mentioned in one of my earlier posts above, are the way to go. Look at the pic. The bottom is the spacer way. 5 pieces. Upper right are a pair of the CCE fork caps. Look just like the 39mm caps but are made for 41 mm. These will shorten the overall fork length by about 1 1/4".

You do have to bore the top tree to use the CCE fork tops, but as long as you're already set up to do the bottom, it's not that big of a deal. When you press the stem out of the bottom tree, (makes set-up on the mill a lot easier.) do it the long way, from the top. The other way the groove for the snap ring gouges the aluminum in the bore.

One more note about the fork top nuts upper left. The domed ones won't fit through a 39mm hole, means you'd have to assemble the spacer, etc. on the bike. The flattop ones have rounded corners and will fit a 39mm hole, so you could assemble the whole thing on the bench and slide it up through the trees. Not a big deal, but...

 

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The new fxs blackline has a nut like the 39mm forks but screws into the 41mm tube ,but still won't fit until you machine a bit of the top of the fork tube which is what I did and then just machined the triple clamps out,also I wanted the bike to sit at a certain height so had to make my damper rods as well if you want pics just e-mail me.
 

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Couple things to think about.

You really only remove 1mm of material. That much all the way around makes the hole 2mm larger in diameter.

Fork stops. Most of the 39mm forks use two little stops on the lower tree, and a tab on the front of the frame. You can get a lower bearing cup with a tab on it, should be pinned to the frame when you install it. You could fabricate the tab and weld it to your frame. You could get a set of the hidden fork stops from Landmark or DNA, then smooth the stops off the lower tree for a cleaner look.

There are two ways to do the top tree. You don't have to bore it, you can make sleeves like the ones in post #68 of this thread http://www.jockeyjournal.com/forum/showthread.php?t=26910&highlight=39mm&page=4 Noodelz may still be making some.
Or you can bore the top tree and use the Custom Cycle Engineering fork tops which look like the 39mm ones but are made for the 41mm tubes. CCE makes them as part of their Tru Track triple tree sets, but you can buy them separately, part number 7LN-4100.

And, if you're really worried about it, the very first 39mm forks had cast steel lower trees. '87 FXR I think.
Old thread but I'm attempting this conversion myself. Could not find 7ln-4100 on their website but shot them an email. Waiting to hear back on it.
 

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Made me look. I thought I had gotten that 7LN-4100 part number right off the package. Oddly enough, I still had the package with my fork stuff so I would remember the part number. It wasn't in the older catalog I had, and I remember calling them to ask. See the scan below, and you'll see why I was confused.

I see they went up in price. I think I paid about $100 for the ones I bought, but it's been a few years.

As for the cheaper fork top nuts, I'm wondering if those are replacements for 39 mm forks. When you find out, please post to this thread and let us know.

 
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