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Need a lesson on narrow glide forks

19331 Views 28 Replies 14 Participants Last post by  govmule84
Want to put narrow glide forks on my hardtail fx frame build. Is it the sportys that got 35mm tubes and the fx got 39mm tubes?? Do the sporty forks/trees fit in the fx/flh neck?
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Early FX and XL both came with 35mm. The later models came with 39mm.
Do the sporty forks/trees fit in the fx/flh neck?
Sportster steering stem was smaller diameter than Big Twin until 1982. With regard to diameter, the fork tubes are interchangeable between the two models.

Bob
There are 3 basic types of Harley narrowglide forks. The first ones are 1 5/16" (or about 33.4 mm) and were used on K models, Sportsters, and the first Superglides through about 1972. Only those two years of Superglides had 1" stems and will fit directly in your FX frame. Forks are kinda light, too and are set up for drum brakes. Sliders are steel.

35 mm forks, made first by Kayaba and then Showa, in Japan, showed up with the disc brakes in the early '70's. The FX trees will have a 1" stem, as will the XL ones after '82. Earlier XL trees will be either 7/8" or 15/16" ('78-'81) These are available set up for the pie slice caliper and cloverleaf rotor, dual disc calipers with 10" rotors, or a later single (or sometimes optional dual) disc caliper with 11.5" rotor(s.) These forks are small enough to look light and minimal, but strong enough to work well and hold up.

The best ones (my opinion,) and probably the easiest to find, are the '87 and later 39mm Showa built forks. The lowers are set up for the pre 2000 single piston caliper, the 2000 and later 4 piston caliper, or the XL Nissan caliper, all in single or dual disc. Sometime in the early part of last decade, HD changed over to 1" and then 25 mm axles. All the trees will have 1" stems. I think the '87 FX had a steel lower tree, but the rest are all aluminum. Fork stops are little nubs on the lower tree that bump up against a stop on the front of the steering tube. Watch for nubs that have been sheared off, an indicator of accident damage. Also, for a Sportster tree on your FX frame, you may have to cut off the lock tab.

There are also aftermarket steel trees for most of those forks as well as the 41 mm And, you can bore a set of 39mm trees to take the 41 mm tubes, if that suits you. Lots of options.
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I don't wanna hijack your thread but what did the 33.4mm come on? That's what I have. They're steel instead of aluminum and they taper at the bottom a little and I think they were front drum only. Just wondered because I wanna buy as many sets as I can because I love them!
I have 33.4mm also....called 1.3whatever inch in the harley books. I don't think they were actually called 33.4mm until the 35mm came out.

I assumed (I know, I know) that when he said 32mm he meant the 33.4mm. otherwise an excellent post with great detail.

That was a great post with a TON of info in it.
M.O.Ther ,

Damn fine write up. Thanks.
You guys are right, of course. It's 1 3/8" and 33.4 mm. That's what I get for doing stuff from what's left of my memory. I will edit my post.
I have 33.4mm also....called 1.3whatever inch in the harley books. I don't think they were actually called 33.4mm until the 35mm came out.
Before Harley got on board with the metric system (Japanese forks), the fork tubes were specified in inch dimensions. 33.4 mm is a "soft" conversion to metric. 33.4 mm = 1.315", 1 5/16 = 1.3125. Same way with the Wide Glide which was originally 1 5/8" (1.625") until the Japanese version came along at 41 mm, or 1.614".

Bob
Getting a set of 80's sporty trees with the 1 inch stem. So, when I get the tubes, they can be 35mm or 39mm and will fit just fine?
Getting a set of 80's sporty trees with the 1 inch stem. So, when I get the tubes, they can be 35mm or 39mm and will fit just fine?
35mm tubes only fit 35mm trees, same for 39mm.

Bob
I just picked up narrow glide trees, 35mm and 1" neck, to put on my '75 FXE build. I want 4 over tubes and need some help. Here is a pic from a popular parts catalogue,

Which part number should I order?
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I just picked up narrow glide trees, 35mm and 1" neck, to put on my '75 FXE build. I want 4 over tubes and need some help.
Which part number should I order?
First you need to know whether you have Showa or Kayaba sliders. Easy way to tell, the Showa have bolt on axle caps on both lowers, the Kayaba only on one side. As for the length, the FXS (Lowrider) and FXB (Sturgis) came with fork tubes that were 2" longer than the FX and FXE.

So, if you have Kayaba forks, you want the 230-595, and for the Showa fork, 230-573.
All i have right now are the trees. I expect to buy Showa sliders as they are more common. These trees musta had come from a sporty because they have the neck lock loop on them.
If the bottom tree came from a Big twin they have a "stand-up" fork stop welded to the Typical "flat" sportster stop. I'll try to find pictures...
RP

EDIT;
This is a sportster tree...note the stops
http://www.ebay.com/itm/Harley-35mm...Parts_Accessories&hash=item1e76b3b9b6&vxp=mtr
This is a Big Twin tree..Note the stops welded onto the Sporty type stop.
http://www.ebay.com/itm/Harley-73-7...Parts_Accessories&hash=item589c380667&vxp=mtr

Big ass link..But I don't know how to "Borrow" the pictures
Ah thanks, I actually have the second style, Bigtwin tree.
2
I don't know how to "Borrow" the pictures
scroll over a picture, then right click and go down to "properties", then it will show the picture address (URL).
Sportster-

Big twin-
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Has anyone bored a set of sportster 39mm trees to accept 41mm tubes?
Is it safe or the trees will break at the first pothole?
There are at least two pretty detailed threads here somewhere on that very subject, bored 39mm trees. Good hints and at least a couple different ways to deal with the differences in the way the 39mm and 41mm atach to the top tree.

Here, I'll save you the search:

http://www.jockeyjournal.com/forum/showthread.php?t=95146&highlight=39mm+cce

http://www.jockeyjournal.com/forum/showthread.php?t=26910&highlight=39mm+cce
^^^thank you M.O.Ther, I did search but couldn't find a better match than this thread, mustn't have used the best key word
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