AmeriDynaTechie Corp

One of my all time favorite commercials came during the dotcom era, when I was working in the Silicon Valley. It features two exec type dudes on an airplane, discussing their current investments. I don't remember what the commercial was for, but at one point, with a totally straight face, one of the guys refers to the fact that AmeriDynaTechie Corp looks strong. It was a brilliant satire of the day; pointing out how ridiculous all the high-tech startups (and their names) were, and how seriously we all took ourselves, as we all went to the same conferences, wearing the same polo shirts (with different embroidered logos), selling versions of the same product, and scrambling to see who would be the first to figure out how to make money on the Internet (other than porn, which accounts for about 2/3 of all money made on the web, so I'm told). It really was fun. We were all such a bunch of nerds. And there was so much money flowing around that you could easily get lost in it all.

In that spirit, this post is dedicated to the BMW /5 motorcycle community, as it will contain the entire, nerdy story of my recent front end rebuild on my 1972 R75/5, including my SWAG engineering method and end results. Through the process, I've discovered some things that may not be a part of the collective /5 knowledge yet, and I'm hoping to add something there too. I'm sure this one will take me a few days to write; check back if it doesn't seem complete right now. So strap on your propellor beanies, 'cause here we go.

This whole saga started when I decided to replace my top plate on the triples with the Toaster Tan brace, made by Stephen and Jeff. It is a beautifully crafted brace, which users say increases stiffness, improves handling, and so on. I couldn't resist. This decision turned out to be a blessing in disguise; though the addition of this brace (and all its precision) caused me a month-long headache, this happened because the brace exposed some potentially catastrophic problems with my front end.

At the outset, I want to publicly say that Jeff in particular has been a lifesaver--he has worked with me at every stage of this process, making multiple sets of spacers for me and even crafting a parallel-ness tool that I needed to continue fixing the problems at hand. He has been truly professional at every turn.

I began by following the instructions for installing the brace, which basically amounts to shortening the headlight ears and then putting on the brace. When I completed the installation, I checked for stiction, and it was impressive--I could push the front end down and just have it stay there until I lifted it up again. It was clearly way out of alignment, or worse.

I should back up for a moment and say that I bought this bike about four years ago. The fellow who I purchased it from had done good work on it overall, but there was a little evidence that sometimes he took the cheaper course instead of the right course. Little things, like using US clamps that required US allen bits on the exhaust, or using a pipe wrench on the top bolts of the forks. I had read the Randy Glass article on fork alignment (as hosted on Duane Ausherman's website) several times. If you haven't read it, it is the gold standard on the topic as far as I'm concerned. I had never examined my front end for alignment, and convinced myself that since I had little to no stiction, I was probably ok. Basically I was just too lazy and afraid to check it out. And I have to say that some on the /5 list call the whole alignment issue a load of BS, and maybe they're at least partially right. My bike rode like a dream; short wheel base, low euro bars, no fairing or windshield, no luggage, no rear pegs, solo gunfighter seat. It has been the bike I've always dreamed of owning. But in the back of my mind, I always wondered, "What if the alignment gurus are right? When will my beloved bike decide to send me on my first manned flight to theothersideoftheguardrail?"

Well, after I had added the new brace, it was clear that I no longer had a choice about whether to deal with the front end or not--it wasn't working and the bike was unrideable. I cleared space in the garage, rolled out the tools and got to disassembly.

Teardown was not a huge deal, but I did come across a few challenges. The only one that stopped me for a while was how to remove the threaded rings in the ends of the fork tubes. I got several suggestions from the /5 list, but in the end, chose to order Ed Korn's pin body and two pin sets (one for the fork threaded rings, one for the fork filler caps). Ed's tools are remarkably simple and well-made, and they are budget priced, being made from faily common materials. I also ordered his puller for steering head bearings (also on the previously linked page), and his tool for greasing wheel bearings without removing the bearing stack.

There were few surprises in the forks, except that the "anti-dive" springs (sold in the 70's, I'm told) had been installed with the thicker bottom bumper rings (the springs would not be re-installed, and I went to the thinner bumper rings). The internal components (damper ball, wiper rings, etc.) all looked good, and I set that assembly aside. I happen to also be an amateur woodworker, so I took the fork tubes over to my table saw bed (flat within .001") and rolled them across. Ka-wump, ka-wump, ka-wump! Not good news. One tube wasn't too bad off, maybe .005" bowed, but the other was a good .025" bowed, maybe more. I can only guess that the PO turned the tubes such that the bows went front to back, allowing the bike to have minimal stiction in spite of the bends. I started investigating options for replacement fork tubes, and found that most places carry Frank's as an after-market option for about $220 per pair (contrasted with several hundred each for BMW). About this time, I came across a reference on Duane's site to The Frame Man in Sacramento, and how good his work is. I also heard his name from two other vendors I trust, so I gave him a call. Pat was the one I dealt with at all times, and he was amazing. Their policy is that they will look at anything for free, and only charge if you have them do the work. Also, they do nothing but C.O.D. return shipment, i.e. no credit cards. Not a huge deal. I sent Pat all of my front end parts--the fork tubes, lower triple with steering shaft, upper (new) triple clamp, front axle, fender horseshoe/brace and lower fork sliders. After he'd looked at it all, he determined that he could straighten the fork tubes and horseshoe and front axle (which was bent .012", a lot for such a short piece!). The rest was within specs, and the steering shaft was at right angles to the lower triple clamp. After the work was all done, it was a grand total of $135 including shipping, and I got to keep all my BMW parts. I can't say enough good things about these guys--the work was impeccable. I couldn't detect any bend in the tubes using my table saw after getting them back, and only found maybe .0005" variance in them during the alignment process.

At this point, I replaced my steering head bearings, with a set of "All Ball" brand from Re-Psycle. They use these on their bikes, and they're $40 instead of $67 for BMW, and they have had good luck with them. Using Ed's tool, the old bearing races came out in about ten minutes, and I used a Dremel to cut most of the way through the lower cone. I then made the cutoff wheel smaller by grinding it against cement, and the smaller wheel let me get even further through the bearing without touching the steering shaft or lower triple clamp. One good whack with a screwdriver and rubber mallet broke it, and it was ready to come off. At some point, it looks like someone torqued the acorn nut by using the steering shaft lock as a stop, and the slot in the steering shaft was flared out a bit on both sides. I just used a basic file to knock this burr down, and then the lower cone slid right off the shaft. The new races went in quite easily, and I had the idea that if you got a second bolt like the one in Ed's bearing removal tool (but longer), you could use the tool for inserting the races as well. For the lower, if you use the old race to push the new race into the head tube (it's recessed a bit), you can just use the puller to pull the old race again after the new race is in place. Easier if you keep the old race oriented the same way it came out, i.e. flared in at the top so the puller can bite against the flat upper surface when you re-pull it.

I switched over to the newer style steering bearing adjuster nut, and reinstalled the upper and lower triple clamps. Now I could see that even though I had shortened my headlight ears, they weren't short enough yet. Not wanting to re-route all the wiring to them (I have custom signals, and three wires to each signal--two for the signal, one for the lite-buddy), I marked and cut them again while still hanging from the bike. The fork tubes were to be set down in the new top brace 6.5mm, so I bolted up the acorn nut, and installed my new top spacer and the top fork bolts. I then loosened the lower triple clamp nuts, and allowed the forks to slide down until the new spacers made contact with the top clamp. I then tightened the lower triple clamp nuts again, and removed everything up top. This was my first big mistake. At this stage, I should have used a straight edge to ensure the new top clamp was flat--as it turns out, it was slightly bowed, higher at the ends than the center. I can't remember, but I believe I did this adjustment (of the fork tubes) with the headlight ears in place, since as I stated already, I didn't want to re-run all the wiring (I have since realized that I could have just disconnected the wiring in the headlight, and easily removed the ears for this step). Since the headlight ears are held by slight pressure from the upper and lower clamps, I believe that what happened was that I adjusted the fork tubes without compressing the rubber in the ears, so that the rubber was flexing the top clamp up slightly on each end. Next time around, I'll take the time to do this right, as it caused another big headache during the alignment process.

So now the front end was back together to the level needed to begin aligning the forks. The Randy Glass article encourages the user to try to get as close as possible to .000" of runout in two planes. The Y plane is defined as front-to-back, i.e. one fork being in front of the other, and the X plane is defined as how parallel the tubes are to each other. Duane mentions .004-.006" as being an amount that led to wobbles back in the day; with wear and so on, who knows what the numbers would be today--I suspect each bike is different based on its wear, etc., but I was shooting for .000" if possible.

Upon initial inspection, I found the Y plane to be out about .005 or more, and the X plane to be out .015+! This with newly straightened parts, indexed clamps, etc. I knew I'd have some work to do, but there was more than I thought. From here, I followed Randy's article, using a piece of maple and a ratchet strap on the Y plane. It took about 2 days, and then I had the Y plane dead flat. I was amazed how much force it took, for how long, to change the set of the lower triple. Next I set to work on the X plane, and tried using a strap clamp at first. While I could flex the forks inward with it, it just didn't have enough force to change things. After a couple of days with no progress, I bought two Jorgenson handscrews, as pictured in Randy's article, and used one of those. As an aside, the 12" screw size has just enough jaw opening to accommodate the fork width on a /5. I found a good trick that allows massive force to be generated with these clamps--open the inner screw (the one that will touch the forks) all the way, and cover it with a couple of pieces of vinyl tubing, etc. to protect the fork tube. Open the outer screw not quite all the way. Slide the clamp in place, and while holding the inner screw tight to the forks, tighten it as much as you can without moving it away from the forks. Then use the outer screw to really apply pressure. You'll be using the clamp as a lever, and the inner screw is the pivot point, so you're getting something like a 5:1 lever. Even at that, I had to leave mine clamped inward about .050 or more for two days to take out .015 of runout.

I finally got the X plane down to .001, and was satisfied with that. As Randy had predicted, the Y plane was now a little out. I went back and forth for another couple of days, and finally used the board/strap plus the handscrew all at once, and that was the trick that got things near perfect in both planes. Y was dead flat, X was .001. Golden.

So now I'm thinking it's smooth sailing. Remember that little flex in the top brace? Well, take a straight line and curve it, and the end points are now closer together. So I went ahead and torqued up the top bolts and acorn nut, and re-checked the forks. Both planes were out. I tried several different methods of torque relief, and finally found one that would keep the Y plane flat, but the X plane always jumped up to about .0035 runout when I torqued the top clamp pinch bolts--a bit too close to that "magic" number of .004. When it finally occurred to me to check flatness of the top clamp, I immediately saw what was happening--the flex in the top clamp was bringing the end points (the holes that clamp around the fork tubes) together, and that was splaying my forks. I tried all sorts of things, including changing the order of torquing things, torquing 5 pounds at a time and alternating, etc. In the end, bringing the fork top bolts to a higher torque reduced the flex in the brace enough to bring the runout in the X plane back to .002. The new top brace no longer requires these top bolts to be torqued to 80+ lb./ft., but I do have them higher than the new spec of 30 lb./ft. Not wanting to start the whole process over, I decided that .002 was close enough until the next time I feel like tearing down the front end (yeah, right!).

After all that work on the top clamp, the Y plane was out again. I used every torque relief method I could think of, but nothing would keep it flat when I torqued the acorn nut. I braced against the bolts, against socket extensions in the extra top clamp holes, etc., but always wound up with some "rock" in my glass on the fork tubes. Finally, as a last ditch effort, I torqued the acorn nut, and then used the ratchet strap and board to put serious pressure on the forks to try to move them back to neutral, i.e. let the top clamp rotate under the torqued acorn nut. Success. The Y plane was dead flat, and the X plane was still .002 or less.

This is the main thing that I've never read anywhere on a /5 site, and I would love to hear comments on it. At least on my bike, it doesn't seem that there is any way to relieve torque in such a way as to protect the Y plane. Think about it: no matter how you hold a torque relief arm, you are still putting 80+ lb./ft. of torque against the acorn nut. This is twisting the steering shaft, and that is twisting the unsupported lower triple clamp! That in turn is putting a twist into the upper vs. lower triple clamp. Any torque relief arm I've ever seen in a photo supports the upper clamp/brace only. So this led me to a thought--is the steering lock strong enough to withstand the torque applied to the acorn nut? If so, that lock would keep the steering shaft from twisting, while the torque relief arm would keep the upper clamp/brace from twisting. Any other ideas on how to support both upper and lower clamps at the same time, truly relieving torque/twist in the assembly?

With the forks finally acceptably aligned, it was just a matter of putting the front end back together. With my newly straightened parts, and newly aligned forks, everything just glided back on. The front axle, much like Randy's experience, almost wants to fall out of the fork sliders on its own! A very welcome change from how it was. I adjusted up the front wheel bearings using Duane's shim kit (towards the bottom of the page), and am now ready to button things up with handlebars and controls. I'll also adjust/lube the rear wheel bearings before I head out for the big test ride and see how it all feels.

Although not everyone agrees on what tolerances are required here, I am glad that I did the full alignment process and got things very close. I am sure I won't be sorry for too much precision! I have also been afraid of tearing into the front forks for a long time, and was pleasantly surprised at how simple they are. I would encourage others out there to take the time to check them out and be sure they're working as well as they can. Randy's excellent description played a major role in getting me down this road.

I have had a lot of support out there for this project, and would like to thank everyone on the /5 list for putting up with my OCD on this one, Randy Glass, Duane Ausherman, Jeff Brower, Stephen "Toaster Tan", Richard at Re-Psycle, Chris at Eurotech, Snowbum, Pat at The Frame Man, and Ed Korn. I am grateful to have so many people out there dedicated to keeping these great old bikes on the road, and so willing to share their knowledge and experience with me.