How important are rear shocks... give a percentage?

[orbitangel]

Triple Clamps and Whatnot

San Jose BMW has a top triple to fit R100RS's for about 120.00. A pretty good price. I am going to purchase one, then install a pair of Progressive springs. I already have a Telefix brace on. I noticed an immediate difference after installing the brace. The front end felt "more of a piece". The Forsa shocks I put on back worked well as I rode the bike a couple of days ago.

This thread has my curiosity going. Let's begin with triple clamps. The stock one never impressed me much; basically 1/8 in. (approx.) alloy steel sheet, sitting on top of the fork tubes and attached to them only by the caps. Nothing to keep the tube from rotating in the top clamp. When I bought my second RS (a '78 in 1980) it already had one of these installed:

I never knew who made it (there are no markings of any kind) but I really liked it and it not only tightened-up my front end vs stock but also kept my nose out of the dirt during hard stops. I think it could be an old RPM (Reg Pridmore) part but I have never been able to prove that. I like the way it clamps the fork tubes tightly and ALSO pushes them down about one inch, thus raising the front-end an equal amount. * CORRECTION: It will actually raise the front of the bike by roughly one inch, multiplied by the cosine of the fork angle - maybe about .866 in. and increase the wheelbase by the sine of the fork angle, around .5 in. After I got my current RS (about six years ago) I was able to find one on fleaBay and now run it on my current ('77) RS. It is made of aluminum, anodized black. The stock speedo/tach bracket has to be altered a little bit in order to fit.

The San Jose clamp is also very nice as well but does not perform the second function.

Does anybody out there know of a certainty who made the black one? Inquiring minds want to know!

 

[orbitangel]

Chassis as System

Always consider the chassis as a SYSTEM.
Changing out one part or another of that SYSTEM often results in diminished handling capabilities.

There are a number of "old school" bromides which airhead pilots used to liberally apply to their trusty steeds (along with the Koni shocks, previously mentioned.) To wit:

The first one is I believe, a San Jose fork brace.

It is quite similar to this one which is I think a Luftmeister brace. I could have these backwards but I don't remember the SJ model having fender mounting tabs.

QUESTION: Who copied whom? DID SJ copy the Luftmeister part or was it the other way around?

NEXT QUESTION: I presume these were both designed to be used to supplement the stock brace (seen below) as opposed to being installed insead of the stock part. The front fender would fall off with the first part installed without the stock brace. Not true for the second brace.

That stock SS fork brace/fender mount is actually pretty damned stiff, all by itself.

Then, of course is the Telefix brace. I always thought it looked pretty elegant.

And, of course, the San Jose swingarm. Seems like a different vendor had a less elegant swingarm brace (a bit crude, actually) which was essentially a thick, steel strap, bent in a big 'U' shape and welded on the bottom of the swingarm. Somebody might remember who sold that mod.

Back in the day, I never had enough spare cash for any of this stuff. Now that I do, I wonder whether any of them truly deliver what they claim to, which ones are superior/inferior and whether they play nicely together, as a System. Every single part shown contributes to unsprung weight.

Can somebody elaborate on these mods, their history, known benefits, real or imagined, etc. Vanzen? Ikchris? Shire2000? Anybody? Thanks.

 

[bikerfish1100]

And, of course, the San Jose swingarm. Seems like a different vendor had a less elegant swingarm brace (a bit crude, actually) which was essentially a thick, steel strap, bent in a big 'U' shape and welded on the bottom of the swingarm. Somebody might remember who sold that mod.

QUOTE]

if you look closely, you'll see that your description of the U-shaped strap is essentially what anyone's swingarm bracing is. No one recreated an entire swingarm- brace it up and weld it on. This was just one done cleanly.

ANY of the aftermarket mods for suspension will be an improvement over a stock pre-80 era airheads. However, you are still dealing with a frame & forks that are, in comparison to a modern bike, pretty damn flexible. You can rapidly reach the point of diminishing returns on your dollar, especially given the estimated value of a modified antique. Do what is necessary to make it good, or even really good- but don't waste your time and money trying to attain "perfect"- it can't be found on an airhead at a price that justifies the results.

 

[orbitangel]

Diminishing Returns

if you look closely, you'll see that your description of the U-shaped strap is essentially what anyone's swingarm bracing is. No one recreated an entire swingarm- brace it up and weld it on. This was just one done cleanly.

Sure. I never meant to infer that anybody did anything other than MODIFY the stock BMW swingarm. It's just that I always thought that SJ's method was a hell of a lot more elegant (and a lot better looking) than welding on a big, ugly hunk of boiler plate, and probably a lot lighter, though not necessarily much stiffer.

ANY of the aftermarket mods for suspension will be an improvement over a stock pre-80 era airheads. However, you are still dealing with a frame & forks that are, in comparison to a modern bike, pretty damn flexible. You can rapidly reach the point of diminishing returns on your dollar, especially given the estimated value of a modified antique. Do what is necessary to make it good, or even really good- but don't waste your time and money trying to attain "perfect"- it can't be found on an airhead at a price that justifies the results.

I certainly agree with that analysis. When I first started riding these things, I quickly learned something. Unlike the Japanese bikes of the era, the BMWs (the RS, in my case) were capable of being ridden much faster than I was capable of riding them. That was true then and it is also true that I have mellowed slightly in the thirty years since I was thirty. I do want my bike to handle as well as it reasonably can, without being obsessed with every possible "enhancement." I also have an aversion to broken bones, hospitalization and death. I've been riding since I was fifteen. During that time I have broken only one bone (collarbone) and have never been hospitalized from the sport of motorcycling. I have, however, come very, VERY close to getting killed on many occasions. Many of these events involved the use of a LOT more throttle than was prudent. I do not need to press my luck too far!

If I WERE obsessed with maximum handling I'd do something like Vanzen is doing, namely his "Lufthaptprojekt." Maybe I'll get there, someday - not there yet.
Buying a "modern" machine would be another option, though I don't think I will ever sell my trusty R100RS. Creating a "Vanzen-esque" machine actually appeals to me more than buying something "off the rack." Challenging and FUN!

My main problem is this: I do not possess enough airhead knowledge or experience to know how far to go with the traditional "mods" without just wasting time and money adding junk without adding performance.

Thanks for your input, Mr. bikerfish!

 

[shire2000]

I have been riding airheads for close to 40 years. Have modified the heck out of some of them and left others as I got them. The absolute best mods I have done and still do are as follows:

1. Replace rear shocks with Progressives or better quality. Koni's or now Ikon's are great but I find them too expensive for the small differences from some of the other brands.
2. Replace front fork springs with progressively wound new ones and up the weight of the oil to 7.5. I also usually add at least 10cc more oil per fork leg. On some bikes a bit more.
3. Teleflex or San Jose fork brace, whichever I can find at the time. Both do the job very well.
4. On some of the older ones I will replace the top triple clamp with a billet aluminum one. I have used numerous brands, and do not have a big preference.

Once all that is done, I will play with shock settings in the rear to get the feel I want and will also play with the amount of oil in the front shocks to get it just right. It is all personal preference. I know what works for me, and the only way to get there is to make small changes till you find that sweet spot. Every rider is different. There is no magical adjustment that will work for everyone.

One thing that a lot of people forget about is that the frame is supposed to flex a bit. If you are used to a more modern bike, it will seem very dangerous to you. But, if you forget all that you have learned on the new bikes and remember that frames were designed to be a part of the suspension. Then you can begin to understand how and why the bike handles as it does. You can make that frame flexing an advantage.

Over the years, lots of people have modified the heck out of the frames and suspensions on old bikes. Some have made the frames so stiff that they become more dangerous than when they started.

I have seen lots of old bikes out manouver new ones because the old codger riding it knows what he is doing. It may look like he has pushed the bike beyond it's limits, but in reality, he knows exactly where those limits are and takes advantage of them.

I am not saying that the setup on the new bikes is bad. Just saying that you really don't have to do a lot to the old ones to make them handle well. Even when leaving them totaly stock, they handle just fine, if you remember the age and era they come from.

 

[Rinty]

Can anyone elaborate on these mods...their...benefits...Orbitangel

I once had an '82 RS on which I had installed almost all the chassis and engine mods know to Airheadkind.

Eventually I bought an oiler RS, which had twice the performance and capability, sold the airhead, and got killed in the process.

These bikes were known as Gummikuhe (rubber cows) in Germany, for good reason.

This is purely my opinion, based on costly experience, but my suggestion to anyone who likes airheads, is to accept them for what they are, ride them and use them accordingly, and don't try to turn a goose into a duck. However, by all means replace the front and rear shocks with quality aftermarket items.

 

[orbitangel]

Knowing One's Limits

I have seen lots of old bikes out manouver new ones because the old codger riding it knows what he is doing. It may look like he has pushed the bike beyond it's limits, but in reality, he knows exactly where those limits are and takes advantage of them.

I am not saying that the setup on the new bikes is bad. Just saying that you really don't have to do a lot to the old ones to make them handle well. Even when leaving them totaly stock, they handle just fine, if you remember the age and era they come from.

Excellent advice. And thanks for the tips based on experience, rather than just wishful thinking! I am VERY fond of my old Rubber Elephant (CORRECTION - Rubber COW) but have nothing against incremental improvements - IF - they are actual improvements! Thanks again.

 

[orbitangel]

...my suggestion to anyone who likes airheads, is to accept them for what they are, ride them and use them accordingly, and don't try to turn a goose into a duck.

I am quite happy with my old Rubber Cow. I could always be even happier!

Thanks for your input on this!

 

[Rinty]

I could always be ... happier...Orbitangel

I admit that if I had another airhead, I would install quality shocks front and rear, and an aftermarket upper triple tree. You don't need the fork brace, then.

Yer welcome, and good luck.

 

[shire2000]

If you are going to replace the triple clamp or install a fork brace, do the fork brace first. You will be extremely surprised at the difference. Then do the triple clamp if you want things even tighter.

Myself I look at the physics of it. OK, you install the upper clamp and now that end is nice and stiff, what about the bottom end? It is still out there and capable of waving about. You may not see it, but those fork tubes do bend under normal use and they don't always compress equally. By installing a fork brace, you eliminate over 90% of flex and 100% of compression issues. Both sides will compress equally, as they will have no choice being tied together by the brace.

In my experience, the fork brace is more important that the triple clamp. If you are going to ride agressively, then definitely do both.

 

[orbitangel]

Fork Braces, etc.

If you are going to replace the triple clamp or install a fork brace, do the fork brace first. Then do the triple clamp if you want things even tighter.

In my experience, the fork brace is more important that the triple clamp. If you are going to ride agressively, then definitely do both.

I already have the triple clamp, have had it for years. (see above - "Triple Clamps & Whatnot")

I will go for the fork brace next. I think I like the Telefix best. I AM going to ride aggressively - I always have!

Any input on favorite (dual) rear shocks (beyond what has already been said) ?

Thanks!

 

[8ninety8]

ONe thing I didn't do.....

Many years ago, after seeing the Pridmore bike, I thought I saw in the picture a second lower yoke just peeking out from under the S fairing. So-o-o, I got an extra lower yoke, polished it up and figured the next time I took the forks apart I would slip an extra lower yoke on, thus shortening the length of the tubes exposed to flexing.

Physically it makes sense, that is shortening a lever decreases its leverage. I've never seen another closeup of those old superbikes of '74-'76 front ends. And I know a newer bike would be a hundred percent better than a '74 S, but WTH I've got the yoke, just wondering if anyone has seen this done or did it.

 

[JAMESDUNN]

Fork brace.

If you are going to replace the triple clamp or install a fork brace, do the fork brace first. You will be extremely surprised at the difference. Then do the triple clamp if you want things even tighter.

Myself I look at the physics of it. OK, you install the upper clamp and now that end is nice and stiff, what about the bottom end? It is still out there and capable of waving about. You may not see it, but those fork tubes do bend under normal use and they don't always compress equally. By installing a fork brace, you eliminate over 90% of flex and 100% of compression issues. Both sides will compress equally, as they will have no choice being tied together by the brace.

In my experience, the fork brace is more important that the triple clamp. If you are going to ride agressively, then definitely do both.

According to Bill Srermer in his book "BMWR100RS" replacing the top triple clamp, "was the single best handling fix for the R100 fork". I agree about the fork brace first install, however. It makes a big difference and is a simple installation; at least in the case of the Telefix. It may be enough to satisfy the owner and he/she need not do the top triple clamp swap. New springs by Progressive are a good idea though and the occasional fork rebuild ( I did that one year ago). Rear shocks must be replaced now and again.

 

[ccolwell]

Ditto. I did the triple clamp first and then the fork brace on my R100. Always thought afterward that the fork brace would have been enough. Having gotten the R90S with only the fork brace, I know I was right. If you can afford it, do both. If not, stick with the brace and you'll be perfectly happy. The Telefix is the way to go.

 

[keelerb]

Ikon rear shocks, Progressive fork springs and 7.5W fork oil, and a Telefix fork brace worked wonders on my 84 R100RT.

 

[VANZEN]

reinventing the wheel

Noted motorcycle chassis designer, builder,
and author of MOTORCYCLE HANDLING AND CHASSIS DESIGN the art and science,
Tony Foale, has this to say about the BMW upper 3-tree:

"I've ridden BMW twins for over 35 years, and started with the Earles' fork
models which also used the flat plate at the top. I've used them on the
road, in enduros and raced them. I've done this with the standard fork
arrangement and with machined yokes and noticed no difference at all.
On most of the leading link forks that I built I went for a similar flat
plate idea (although welded to the stantions), subconciously inspired to a
large extent by the BMs. no doubt.
When you consider the loads imposed on that BMW plate it is quite an
appropriate design for the job.
I think you'll find that most opposition to the standard plate stems from
the fact that it's not how others do it, and it certainly doesn't look
"trick".

A fork brace, on the other hand, can do wonders for maintaining slider alignment and improving forks action.
However, a word of caution here regarding "HOOP TYPE BRACES":
If these are not fitted PERFECTLY to forks that have been meticulously aligned ...
meaning:
1) the forks MUST be aligned (see: Duane Ausherman's proceedure), and
2) the "hoops" will very likely need to be bent or shimmed in order to fit the forks properly ...
just "bolted-on", these "hoops" can CAUSE a misalighnment of the sliders
and introduce stiction to the system ÔÇô to the detriment of forks action and performance.
Simply put: IF not installed carefully & correctly, they are junk.

The TELEFIX is "user friendly" and easier to install.

Do not make the mistake of installing fork braces to compensate for
the ills of poorly maintained or worn-out forks components !
... and while we're on the subject:
Fork oil of heavier than factory rec'd weight is most often used to mask poor forks maintenance or improper set-up !
In theory, the lighter the oil, the more responsive and compliant the forks will be,
however, the system must be in good order, damping and spring rates must be correct ÔÇô
thick oil just makes forks action sluggish.


If a fork brace will be the first,
then, perhaps, the "second best forks improvement" one could employ
would be to fit a LARGER DIAMETER WHEEL SPINDLE.
But such a spindle is not easily marketed as an after-market goodie,
requires machining of the sliders, purchasing re-sized bearings, as well as the spindle,
... and certainly is not a pay-n-play / bolt-on "mod".

Oddly enough, a larger diameter spindle is exactly what the factory introduced in 1984
with the adoption of "K-type" forks to the Type-247 (30mm hollow vs 19mm solid spindle).
This fork also incorporated an integral cast fork brace ÔÇô
AND the same old plate upper 3-tree ...
a considerably improved forks system.


my 2?ó

 

[JAMESDUNN]

2 cents!

Vanzen, your two cents is worth a lot more than two cents! A lot of "hands on" information there....thanks.