View Full Version : Ironhead follow on question about 33.4mm triples

10th November 2010, 12:53
So, I'm cruising ebay trying tp round up a set of triple trees for my 72 drum brake forks. I have a few questions for the gurus. First, I know that the 71-72 triple trees had no tabs for the gaiters. Was that basically the only difference? Would the casting number still be -62? I'm just trying to differentiate these visibly between the 33.4mm lowers and the 35mm lowers which have a -72 casting number. Can someone give me some guidance so that I know what questions to ask ebay sellers? Thanks. Also, if someone has a set they are willing to part with, please PM me.


Ferrous Head
10th November 2010, 17:58
The early ones also had straight tubes, later ones "narrow" down at the bottom. And the top of the sliders is slightly different on the later ones - doesn't have the wider section where the gaiters fit on. Pictures would be better - I just don't have any at the moment. But there's a good chance if you get a set without the fender tabs you'll have the right ones.

10th November 2010, 18:57
I figured that would be the case regarding the fender tabs. Those ended in 1969, right? What about casting numbers? These guys are usually calling those the part numbers. I know the 73+ lower tree ends in -72. I think the early early ones ended in -62? Just wondering about the 1971-1972's.

Moon Wolf
10th November 2010, 20:22
No, the lower trees casting number ends in -52A at least through the sixties. The first top triple tree casting number ends in 52 as well (obviously), and will work on any of the 33.4 mm forks, but it has different style ears. The next to tree was the 59 casting, which is identical to the 62 except it's made from steel. In 62 the moco switched to the -62 aluminum version because frames were bending in collisions, and it's a lot cheaper and easier to replace a bent aluminum triple tree. Joestuff claims that the 62A is the same top tree with different riser mounts, but I'm not sure about that (even though he's almost always right). I'm a sixties guy, so my knowledge pretty much ends in 69, probably making this post fairly useless to you.

11th November 2010, 10:06
...I'm a sixties guy, so my knowledge pretty much ends in 69, probably making this post fairly useless to you.

A for effort :D

I guess all I need to know is whether the casting numbers on the 71-72 lowers are the same or different from the 73-Up lower triple trees. I think those were 45707-72. It makes sens that the 71-72 casting would end in less than 72. I just want to make sure. Would someone here with a 71 or 72 stock drum brake front end be willing to verify this?

11th November 2010, 18:53
Hey man, I gotta stock '71 XLCH. I'll see if I can get the numbers for ya tomorrow.
As far as the ears for the gaiters on the lower tree, my lower tree has those ears. They're not drilled to accept the vent hardware though. The ears were a carry-over from '70. I know for a fact that my trees came on this bike from the factory.

Moon Wolf
11th November 2010, 19:10
That was my impression, too, Camojoe.

In some cases the casting numbers remain the same even though the fork tube size is different. Casting numbers are simply not a reliable way to distinguish the parts.

12th November 2010, 08:39
Ok, here is the source of my confusion (at least in this case).

The drawing in the parts manual shows the ears for the 1970 and earlier, as highlighted here:


In the drawing from the parts book for the 1971-1972 forks, the ears are not shown:


That's what I have been saying about the 1971-1972 appearing to look like the 1973+ lower triple tree. If the ears are in fact supposed to be there, I won't worry about it and I'll assume that the drawing is wrong. It's just that if I'm going to bother with buying something, I want it to be right. Thanks again and I'll look for those pictures.