R65LS front end tweaks and aftermarket forkbraces.

[SteveD]

An interesting read.

AFTERMARKET FORKBRACES AND FRONT END TWEEKS
http://www.advrider.com/forums/showthre ... 726&page=5
JohnJen from ADVrider as editor note:
This tome was originally written by Michael Beresford in 1998 and was never ‘finished’ in that life took us both in different directions, so it lacks some details and wasn’t fully ‘fleshed out’ so to speak.
However for those with enough understanding, between this write up and what I remember, there should be enough to put together a means of utilizing these ‘techniques’.
In one of those ongoing 'threads' there was a question about aftermarket fork-braces and front ends. I thought I'd see what the responses to the questions were and then summarize my findings. I've seen a few postings that were close to what my experience has taught me, so at the request of some of those I have shared this experience/knowledge with, (“shared with” as in me incorporating this knowledge into the machines I've re-built for them), I decided to add my 2¢ worth here.

FIRST A LITTLE HISTORY.
I bought my first BMW after riding an friends R100 RS. At that time I had a shop in the Northwest and specialized in fuel delivery systems of all types (carbs and fuel injection), from stock to full race, and factory spec. restorations of all kinds. I also restored European cars at the shop.

At one point this one bikes owner complained that the stock carbs were not for him and came in asking about Mikuni square slides. We settled on some round slide Mikunis I had in the shop. I changed the jetting and installed them so they look stock and test rode it when I was finished.

A month or so later I bought a 1976 - R90/6. And as a matter of course I started fixing it up. I early on, (shortly after I started fixing it up) decided to write this M/C off on my business as a test platform/experimental test subject. I went to the local dealer looking for any and all information I could get ahold of and got the cold shoulder treatment. Needless to say, I didn’t feel like returning for any of their mechanical advise or help.

I have always had a knack at being able to make any engine produce more horsepower than an un-modified vehicle could safely handle, no matter what state/condition it is in when it first comes into the shop. When I was younger I used to build 'fire-breathing' stuff that needed to be torn down again and again. I then turned to maximizing stock stuff. Now my aim is to maximize long term durability, usable horsepower and torque, from basically stock components.

Today I choose oilhead beemers in the m/c class, Volvo's and Bimmers in the car division. My philosophical and mechanical intent is to do the work right the first time which allows me to guarantee the finished product, parts and labor, for one year.

The clients I choose to work with usually want to purchase a machine and make it drivable for another 100,000 miles with only regular maintenance as described in the owners manual. This is basically how my current partner got involved. While there are those who already own some sort of vintage machine that needs to be restored, they also want to ride/drive a vintage machine long term.

Owning my own shop allows me to play with/research many of the different aspects of being able to build and then ride BMWs fast, while having the m/c remain 'stable' under all operational conditions. By 'stable' I mean that I can use more of the available h.p. and torque without increasing the recommended maintenance requirements. Indeed, I have found that I could significantly reduce the wear and tear, thus greatly increasing the bikes useful life (an obvious advantage on a vintage machine). Or needlessly putting myself or a client in danger by building machinery that would behave badly when pushed to it's limits.

THAT WAS THEN, THIS IS NOW, WHAT’S THIS BRACE THING?
One of the first things I heard was, “put a fork brace on.” Two were available at the time. The one from C.C. Products was a round tube bent over the front fender unit and the other one was a four piece bolted together flat unit from Telefix. I bought a Telefix first and found that it helped. At this point I had not taken my front end apart, but it did seem to help.

I had also heard that Progressive springs were the way to go, so I bought front springs and rear shocks. I took the front end apart and cleaned it up, noticing the wear patterns, and took notes. I put everything back together using all the local tricks (plate glass etc.) for checking the tubes for alignment, new rings on valving, new seals everywhere, and 7.5 weight BMW oil from the local BMW dealer. Boy, what a difference, or so I thought at the time. Yes, the m/c handled much better at first with the new springs and shocks and fresh parts. I rode this set-up for about a year. "Harsh" is the best way to describe the way the ride became, though it did seem to handle well in the corners at first.

One thing became apparent to me from day one, the m/c sat much higher off the ground, although I didn't think too much about it at the time. When I took the front end apart at the end of a year to change the oil etc., I noticed the wear had accelerated and changed locations in the sliders and on the tubes. As a result of the changed wear patterns - out came the progressive springs.

The progressive springs which were purchased at the local BMW dealer kept the front end fully extended even loaded with the weight of the driver and passenger. By “extended” I mean that the stiffer springs did not allow the tubes to sit down in the specially machined areas inside the sliders far enough for the ends of the tubes to not want to dig into the sliders as the suspension tried to do it's job. This is the wear pattern that I saw and have seen numerous other times since on other front ends I’ve worked on.

If you take a slider off a BMW and clean the inside of all oil and dirt you will be able to see that there are two distinct surfaces machined into the cast slider along its inner length. The upper load bearing portion of the machined surface is only about two inches in length. Then next there is a relieved cast area that is not machined, then another longer load bearing machined surface below. If one takes a ruler and measures inside the slider where this lower surface begins and then transfers that measurement to the outside of the slider and thinks about how far the tube extends down inside, it may clear up some questions. My conclusion is that using stiffer springs, the tubes rarely ever reach far enough down into the lower machined load bearing surface which constitutes the second guide surface as was intended by BMW engineers.

Another way to understand what is happening is to strip down and clean a tube and slider, and remove the upper seal.

Being careful not to scratch the slider, measure from the top of the slider to the top of the lower machined surface.

Carefully (this procedure is usually done best, clamped in a vise) insert a clean dry tube the same measured distance into the slider adding at least one more inch. While holding the tube and slider so they can not slide in or out, push either the tube or the slider back and forth and notice the maximum amount of side to side play between them. Next insert the tube two more inches into the slider, for a total of three inches now inserted beyond where the lower machining surface begins and check for of side to side play again. Most people can feel the difference.

With the tube inserted one inch more than the initial measurement to the lower machined surface, is approximately where the m/c rests with the Progressive springs installed.

Now, with the tube inserted one inch more than the initial measurement, slowly slide the tube into the slider about four or five inches while pulling and pushing the slider side ways against the tube. This side force represents normal loading of the front end because the forks extend forward. I have noticed a great deal of difference as the two pieces slide deeper into each other, the deeper tube is inserted the smoother the sliding action. Also the deeper the tube (up to the limits specified by BMW), the less 'rattling' I get while pulling or pushing the slider side ways while sliding the tube up and down a couple of inches.

There simply isn't enough surface contact to keep the tube aligned with the slider as the m/c is rolling over bumps and moving up and down when it's “oversprung.”

I'm going to change the subject slightly and say something that some people may take offense at. I still can’t understand why BMW of N.A. doesn’t mandate certain basic tools be in each dealers repair area. The most basic tool is a granite surface plate and a real measuring table-grade Vernier height gauge with a rudimentary dial indicator set up to measure everything from piston retaining ring thickness to the accuracy of brake shoes seating on the shoe spreader. One of my all time favorite responses from a local dealer was "We (BMW dealers) don’t have the money to buy this equipment.” My problem with this claim is that anyone can buy an 18”x 24” surface plate that is guaranteed to be flat within .000015 of an inch, and vernier height gauge with a dial indicator accurate to .0005” for $250 or less. This isn’t the highest quality equipment available, but it is more than adequate to measure damn near everything on a BMW, tubes, fork-braces, etc.

Another thing I have noticed is that for all the slamming I hear and read about Harley’s, they (dealers) usually are set up to measure and straighten front ends. Almost all of the factory repair manuals for H.D. show all the tools required to do this type of job. Harley front tubes are the only tubes I’ve seen that have a material (wall) thickness comparable to that of BMW’s. Although I personally haven’t owned a H.D. since I was a teen, I do restore and build them for the long term for those who have the money. Yes it is possible to do this in spite of all the rumors to the contrary.

In the factory repair manual, BMW gives all the specs for all the twins from 1970 thru the mid 1980’s. Front fork tubes are allowed no greater deflection than .003937", which is slightly under four thousandths of an inch. BMW says the clearance between the tube and the slider is the same thirty-nine-+ hundredths of an inch. The manual also states there is approx. 4.29" of upward/unloading travel, and 3.82" downward/compressible travel. Simply putting an identical-length yet stiffer spring in the front suspension doesn't allow the front suspension to take advantage of BMWs design. If you look carefully at the length of the valveing rod inside the tube you will get a rough idea of the total travel up and down as designed by BMW.

To cut to the chase here, for this suspension to work as designed, you need to see about 10 inches of the length of the tube below the upper slider seal (m/c off all stands with rider on seat) in order to work best under all driving conditions. Stiffer -SHORTER- springs, which allow the tubes to be inserted 10" past the upper seal with m/c fully loaded and off all stands ---- might actually work. However, there are other aspects to consider if one were to doing something like this which I won't go into here.

[SteveD]

http://www.advrider.com/forums/showthre ... 726&page=6
Part 2
SO, TO GET BACK TO OUR (PROGRESSIVE?) STORY…
AND TO DROP THE OTHER SHOE (OR IS IT M/C BOOT?)

In went BMW h/d springs with the white paint on the tops with new oil and all worn parts replaced. I noticed a difference once again. The front end was more supple and easier to control. It didn't feel like I was bouncing along on a pogo stick that had too stiff a spring.

I left the 'new' rear shocks ("oversprung" is the description I like the best) as they were. A three month time period went by and I decided to look things over again. This time I noticed wear on the new tubes and realized it was due to the fork-brace. I am most fortunate in having resources available that most people just don't have. I then had a jig made to hold all the pieces of the forkbrace and then measured them all using a granite surface plates as described earlier.

Every Telefix front fork brace I've ever seen has been way out of tolerance as measured through the centers of the slider clamp pieces. So after taking measurements of a fork-brace, I would then “true” it up so that it is quite easy to accurately install and it will tend to stay accurate. It's now possible to pull over and loosen the clamps and allow the front end to reset itself after running thru huge chuck holes. This does make a huge difference in smoothness and long term wear.

While it is possible to install the Telefix as it comes out of the box and have good results, it is a time consuming job as one gentleman indicated. What he didn't mention is that if your front end isn't straight to begin with, adding a fork brace doesn’t make it so. If anything it accelerates the inevitable destruction of both tubes and sliders.

What I've learned about all of this is --- if the tubes are straight (and remember BMW’s maximum permissible deflection of 0.0039"), and are set in the upper and lower clamps parallel, (both side to side and front to back), then when the fork brace is accurately installed, a BMW front end becomes extremely supple and responsive. Handling in corners becomes a constant joy and is a confidence building experience. Also, as an added bonus I discovered that normal wear and tear is greatly reduced as a result of a properly dialed in and strengthened front end.

By means of these explorations I utilized a dozen different ways of testing/measuring nearly all the different aspects of these front ends, including buying and measuring new tubes from the dealership. The factory book says .004" and I have only seen one new tube outside this specification. So I took that tube and had an old tool maker machine a set of blocks to accurately hold the tubes so they could be straightened. I believed I could straighten that tube to within BMW’s specs. After getting all set up to straighten slightly bent tubes, I found that it was possible to straighten tubes within 0.002" fairly easily. A properly tuned BMW suspension can be amazingly dependable and safely supple.

The most common problem I’ve encountered comes from the m/c and rider going down. The front tubes get twisted as a result, (NOTE: BMW tubes are by far the thickest and strongest steel out there and so lend themselves to being straightened). Experience has taught me, and I have come to believe that BMW engineers figured a $36 REPLACEABLE clamp plate is an easier repair (better design?) than a $100.00 (or more) triple tree clamp and/or $200.00 ea. for tubes, when your rig goes down and twists up the front end. Having a BMW upper clamp plate bend also seems to minimize tube damage.. One of the most common sources of front end problems is the stock BMW upper clamp plate, and unfortunately unless its actually measured there is no way to tell if it is a major problem.

To illustrate my point I present this true life testimonial. Once after throwing my RT down on the left valve cover at around 65 mph on I-5, and then after picking myself and the bike up, I pushed it over to the side of the road. I then rode straight to the shop and measured the front end. the only thing that bent was the stock top clamp. The tubes were straight along with all else. The tubes had twisted slightly, bending the upper clamp about 0.0015" thru the center. All I replaced was that BMW piece with another stock piece and I’m still riding that m/c nine years later and have added an additional 65,000 miles since that “get off”.

During my research I have bought one of every aftermarket top clamp or plate that was available for BMW, because of the potential promise of added stability. And they too are also a potential source of front end misalignment. When I measured aftermarket clamps and compared them (as installed on a bike) with otherwise stock BMW parts as the standard, I found them to be somewhat close to the measured finish specs that new BMW parts measure to, both mathematically and in real life. BUT, all of them (except the factory clamp) either push or pull straight tubes out of parallel in relation to each other on the motorcycle.

BRACE YOURSELF HERE COMES ANOTHER HIT

I tried a C.C. Products fork-brace too and found they work well, if, like the Telefix, you know ‘how to’ and spend the time (assuming that all the individual stock pieces are somehow close to spec when you start the install). With one installed on the R900, and on my 3rd or 4th annual run of the Isle of Vashon TT Race, I turned chicken (road surface tilted away from the corner and some jackass in a Ford something or other was coming down the other way across the center line) just as I entered the beginning of the first hard corner and I momentarily started to back off the throttle a bit. A real no-no on an oversprung BMW.

I ended up bouncing my shoulder off the pavement and going up and over the guard rail heading into that first main corner after leaving the Vashon ferry, all in front of 150 or so other riders. I got bruised and had one scratch under my right eye (flying through tree branches with no helmet on--my helmet was on my tank bag just where it belongs).

The 900 ended up against the guard rail on the pavement side. At some point in its bouncing from one valve cover to the other it twisted its tubes in the clamps and bent the fork brace. No damage to anything other than some metal scraped off the valve covers and a twisted front end. But since I couldn't get the C.C. Products brace off and we were on the Island, I rode home (10 miles) and it completely trashed the front end. Had I been able to unbolt and remove the brace, or come back with a truck, I might not have trashed the front end beyond repair (just the bent brace would have been trashed).

I was able to measure that set of tubes also. Though the tubes and sliders showed the most damage where the brace mounts and from being ridden with the fork-brace holding them in a twist, it was possible to measure them. One had 0.008”deflection, the other 0.015”. Although these deflections are enough to cause some of the damage I encountered. I don’t believe it was the sole cause of all the damage that was present.

I say this because I measured those parts, and over the years have seen many m/c’s come through the shop bent and twisted. Many as bad or worse yet having sustained less overall damage because there was no fork-brace on the motorcycle holding things out or twisted. Just as a fork-brace is meant to hold sliders in accurate tandem, a fork-brace can also hold it where it does not want to be/need to be. At some point the pressure applied to the tubes during an accident goes past a point of no return and though everything is clamped tightly a fork-brace will eventually give up something. As will all the clamps and tubes.

If you buy a C.C. Products brace and it's properly installed and you "go down" leave the m/c hidden in the weeds and get a truck and or trailer for taking said m/c anywhere.

I say this after the fact. The C.C. Products brace is a real good one. I might not have been out the money once again for a new front end if I had either been able to get the brace off or carted the m/c itself to the shop by other means. For you see, fellow riders, the brace twisted in that accident and then held the sliders in the finished twist, oooooooooooooooohhhhhhhhhh.

Since I now have more than one (somewhere near a dozen) BMW m/c's, I've had to go through each one because all of my machines are older, early ‘70s to ‘83. I also set up BMWs for other more discerning riders. I have accumulated tools from BMW, and lots of custom ones that no dealership has.

I have a partner here at the shop who has "seen" and experienced these things first hand, that at one point even he, and probably most of you, could only dream of.

So in conclusion for now, if you can get a Telefix trued up, and installed properly, it's easy to reset and remove it if you have a "get off". This assumes you are in good enough shape to get the forkbrace off. So far I've ridden home from every dump.


End part 2

[Zombie Master]

A most excellent post Steve!

I purchased my 1984 R100S new and the front end was just too soft for the roads I was riding. I installed hd bmw springs, a set of damping adjustable Konis and a CC fork brace. At the time I had no shop so when installing the CC brace I made sure it wasn't pulling the forks out of line when tightened. As I remember the front end was a little bit stiff, but over the years has softened to perfection. If I fall down, I will make sure to loosen the fork brace before traveling on! Or get a truck.

Steve, do you still do repairs on Airheads?

[SteveD]

Steve, do you still do repairs on Airheads?

Only my own! To clarify ZM, those articles above were lifted from advrider...I'm not the author.

JohnJen from ADVrider as editor note:

[enigmaT120]

What does the writing have to do with an R65LS?

[Major Softie]

What does the writing have to do with an R65LS?

Well, after searching for "65" in the thread, thinking that maybe I'd missed something, I discovered that it was about going 65 mph, and traveling 65,000 miles.

Other than it having the same forks as the bike in the story, that's as much of a connection as I was able to make.

[enigmaT120]

Other than it having the same forks as the bike in the story, that's as much of a connection as I was able to make.

But it doesn't, at least not the top fork plate. I've always wondered if fork braces would even make a difference on an R65, since the fork plates hold the forks so strongly.

[Rob]

Well, and the R65 had a fairly stout fender bracket that acts like a fork brace. Not Telefix stout, but impressive, esp. with the upper triple clamp.
I don't know where BMW came up with the flat plate for the upper for the 247. I guess it was a carryover from the Earles?
I'm glad I bought a R65 when it was my time to buy a new BMW. I got a lot of advances. G/S would have been more fun, maybe, but that was 2 years in the future.

[Major Softie]

Other than it having the same forks as the bike in the story, that's as much of a connection as I was able to make.

But it doesn't, at least not the top fork plate. I've always wondered if fork braces would even make a difference on an R65, since the fork plates hold the forks so strongly.

Hey, I'm not saying the connection wasn't tenuous, I'm saying it's all I could find.


And, yes, fork braces control/reduce the forks flexing out of alignment below the triple clamps, so, yes, they still make a difference. A stronger more rigid triple clamp assembly can make sure any (perceptible) flexing will be limited to only below the triple clamps, which definitely reduces fork flex, but they can't do anything about the flexing that is below the clamps.

OTOH, I can't imagine ever riding hard enough myself to need more than strong triple clamps, except in the dirt.

[SteveD]

What does the writing have to do with an R65LS?

If you were to open the link where this info was sourced, it's a thread re: the R65LS and this info was written by a guy and edited by his friend that had worked on a R65LS to improve it.