Why Glide-Forks Slam on Re-Bound by Robert Luland

From the forum of http://hydra-glide.net/ > Panhead > Fork Tube Bushing Puller :

VT (aka Plumber), I’ve been sending mine (forks) to Bill's (Pennsylvania) for the last twenty-five years. He’s got the right tools and experience to get the job done the right way the first time around. That (Kent-Moore) puller head is more precise than you can believe. The catch on the end has to be .064 on the money to grab these things (lower bushings) and that’s no guarantee. I’ve done it in the past scoring it with a saws all blade tack welded to something but it wasn’t worth the time wasted, but I can turn ya on to some helpful tips when it comes to the glide front end.
The bushing to tube relationship is important. With out that seal the hydraulics don’t work. I’ve seen a lot of people on the forums complaining about their front end banging back. Some buddies of mine back in the eighties did some experimenting. Our conclusion was simple. Original tubes are hard chrome plated. If you look at one closely you will see what looks like a cross-hatch pattern similar to a newly rebuilt engine cylinder. This forms a seal to the bushing. Every front end that banged back we found had show chrome tubes. That smooth finish leaves no seal. Forking by Frank can still give you the good tubes. I also found that I don’t like the way the factory reamer finishes the job. I prefer to have the bushings pulled and inserted by some one else but that’s were it ends. I prefer using a dingle-berry hone with honing fluid. You can get one from McMaster-Carr for twenty bucks. Using this hone also leaves a cross-hatch on the bushing surface.
Well that’s it for today’s science project. Bob and Katie Dog.

••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••

With Correct Tubes from:
http://www.frankmain.qpg.com/

Correct Bushing Installation from:
http://www.billscustomcycles.com/

I read it.
I don't believe it.

You must. If you don't, then why not? If you have no reason, then Robert Luland's explanation stands without any needed support.
I suggest you motor over to Hydra-Glide.net and read the chatter first, to follow other threads of reason, none of which make any mechanical sense. There are well meaning riders over there, but they're stuck on heavier fork oil as being a cure. Harley and Davidson had rooms full of engineers, all trying to make themselves useful. Unfortunately their manufacturing reasons and methods for the Hydra-Glide never survived . Robert and his friends reverse-engineered Bill and Walters work.
I think Robert Luland should be inducted into the AMCA hall of fame and be given an honorary life-membership to the club.

I disagree with Roberts idea that bushing to tube fit has much to do with dampening, unless they are way loose. When the forks compress, the oil is forced thru the dampener, restricted by it's valve, effecting a dampened movement downward. On rebound, the oil has to get back where it was, passing thru the dampener again, it's movement restricted thus dampened. If Roberts' idea was correct, you would have no dampening on compression as well as rebound. I'm planning to replace my 2" over tubes with stock lenght ones, so I'll be more educated in Hydra-glide theory soon. Mike

I read over on hydra-glide that you got the satin finish tubes from Frank's. Did they have anything to say about the dampening effect, or did you order them online?
Looking forward to hearing the results. Hope you use HD fork oil. Hope your lower and upper bushings are sized and honed for the tubes. Thanks for rebuilding them online and sharing the info.

They ask for COD or pre-pay before delivery. I'll get some pics when they arive... Mike

I put a couple hundred miles on the new front end and I'm happy with how they work. THe old setup had 2" over tubes and I wanted to get back to the stock look. I used Progressive springs to soften the harsh ride, turned out the springs that were in there were also progressive but about an inch longer. I set up the preload at 3/4". One glitch I ran into was the dampener kit I bought from JP came with new snaprings that were .008 too thick to fit the grooves in the Franks Legs, so I used the old ones to hold the dampener assembly into the bottom of the tubes. The handeling with the stock lenght tubes is much better, especially at low speeds and the "harsh dampening" is completely gone. I do have a bit of "top out clunk" when I pull over the curb at the end of my driveway, I probably didn't have that before due to the stiff springs. I may try some heavier oil at the next oil change. The Franks tubes fit into my sliders real well, no play at all that I could feel, and the tubes measured exactly the same size from top to bottom. I was thinking an updated seal would eliminate the felt rubbing on the tubes for a bit less "sticktion" but they were back ordered so I went OEM. The dampener kit came with all new paper washers (6 of each) and I had no problems with leaks. Mike

sounds feasible to me. I've seen the same sort of thing done with various old British forks, by people like Dresda who know their business, and it seems to work.

given the amount of general reaming and fitting that you get on older H-Ds, I would hardly be surprised if something like this was the case. It would be consistent with the overall Company philosophy

A sloppy bushing in the slider would leak or maybe bind if it was very bad. The damping has to do with forcing oil thru a restricted and metered orifice. I would suspect poor assembly of the damping rod and low oil levels a long time before I would blame the slider bushings. Ever wonder why the top nut is vented? To let air go in and out as the volume in the assembly changes. The real trick is to let the air move and keep the fluid in. With the spring in there and the fork at full compression there is not a lot of space left for the "damping fluid" when it is at the correct level. What makes the front end rebound so hard is an air bubble. Air will get by the damper rod way easy. Typical clunk can be heard and felt. So put me with Panic and Panacea, I don't belive it either. Just my humble opinion.

Why not use the same solution that the japanese forks have. A short spring is located on the hydraulic unit. This spring only takes load the last inch or so of the travel outwards and works in the oposite direction of the main spring (hard to explain with words, take look at an exploded diagram). This prevents the "clunk". Might take som macinining to do though.

The only fork I have seen with vent-holes is the Hydra-fork. Air compresses like a spring. Many forks are preloaded with air-pressure to.

I was considering doing just that, the problem is the early tubes only have a shoulder machined into the bottom deep enough to hold the dampener valve/ snapring, you would need a flange at the tube base to hold the topout spring against the dampener tube top just under the big spring. I wonder if Forks by Franks could modify a set as an experament? Mike