Braces (Rubber Cows?)

[sumran]

I have seen several references lately to braces of various types, including the article on the CS restoration in the current ON (very enjoyable article). I have seen frame braces, stiffened swing arms, fork braces and high-performance triple-tree top braces. I am curious about how much difference these items make in real life.

I enjoy the occasional spirited ride but I am no road racer. I don't mind my valve covers being worried, but I don't want to drag them. I do travel two-up with substantial luggage and hope to do more of that as time goes on.

[flash412]

I have seen several references lately to braces of various types, including the article on the CS restoration in the current ON (very enjoyable article). I have seen frame braces, stiffened swing arms, fork braces and high-performance triple-tree top braces. I am curious about how much difference these items make in real life.

I enjoy the occasional spirted ride but I am no road racer. I don't mind my valve covers being worried, but I don't want to drag them. I do travel two-up with substantial luggage and hope to do more of that as time goes on.The fork brace and the top clamp give the biggest bang for the buck in terms of handling, in that order. But before you buy one or both of them... for the GREATEST handling improvement simply install 10wt or 15wt fork oil.

[sumran]

The fork brace and the top clamp give the biggest bang for the buck in terms of handling, in that order. But before you buy one or both of them... for the GREATEST handling improvement simply install 10wt or 15wt fork oil.

Thanks. I put in the heavy fork springs and 10wt oil and it made a nice improvement.

[Isamemon]

to a point Ill agree
progressivesive sprigs adn a LOWER fork brace make a big difference
heavier oil helps too
but dont forget the tail end ( flexing , rubber cows)
Id invest in better rear shocks/springs ( with the above said) before I would do a bigger upper tripple tree
rubber cows ( like all cows I know) have front and rear legs
and how much flex you get between your lower tripple tree and the top, after a good fork brace, to me, IMHO , would be marginal
look at it
look at your lower brace and the top, the distance, how much will that flex ?
I dont know
again IMHO
I can only base it on my exprience
progressives, a telefix and konis ( on the back, now ikons)
if I ned more then that, im riding the wrong kind of bike

[flash412]

I can only base it on my exprience progressives, a telefix and konis ( on the back, now ikons) if I ned more then that, im riding the wrong kind of bikeAgreed. I forgot his bike has dual shocks. Monolever suspension started in '81 in the USA.

[sumran]

I do have a good set of Konis on the back.

[26667]

the lower brace is a cheap ez install. the upper is considerably more labor intensive, but if you're working on steering hd bearings, forks, and that area in general, it might be worth the time. Even tho a number of years have passed btw the time i owned an R100 w only the lower brace and now, I can notice the difference. that is, the current bike has both and i can tell it handles better...not like a new oilhead, but better than the single lower fork brace.
trust me. idon't ride it hard. i'm fiftyeffingsixforfuxake!:violin

[vanzen]

Koni 7610s (or Ikon, as they are now marketed) are the quintessential "Old World" performance shock – meaning STIFF-STIFF-STIFF. One can do much better in a compliant and progressive shock (like Wilbers), but they are not cheap.

Appropriate spring and dampening rates with a light oil works better than masking a poorly set-up fork with heavy oil. Heavy weight oil simply forces the action of compression or rebound to respond SLOWLY.

Fork braces work – noticeably so. Telefix was a good one, because it is an easy install – self aligning. If one chooses the "hoop" type braces that were popular in the day, remember that they must be bent or shimmed to fit exactly correctly or they will cause more problems than they could ever cure.

Fork alignment is likely the one most important thing that can be done to improve fork performance.

Frame bracing is probably moot unless soft compound tires in wider than stock sizes are fitted, and / or engine output is increased.

I am skeptical of the aftermarket upper triple trees – because I had one crack in 3 places in a low speed get-off.

[ADAMLIVI]

The R100CS restoration article was mine ... thanks.

I have had a few ask me which of the modifications I made had the greatest influence in handeling ... as they were all done at one it is impossible to say. I suspect the order of impact is as follows with most impactful first...

1.) Top Triple Clamp
2.) Proper Fork alignment
3.) Rear Wilbers
4.) Frame Braces
5.) Swing Arm Brace

All somewhat conjecture but based on research and discussions with people smarter than myself. While the individual impact of each item is unknown, the complete package is pretty amazing. I am not a racer boy by any means but the stability leaned over at speed is remarkably improved. Espically with bags loaded or a passenger. I took a ride last month with some of the GA BMW MOA guys and on the way home in a long sweeper at about 75 fully loaded dragging my toe the old cow was rock solid.

In the restoration process all of the modifications kinda made sense ... if I was going for incremental improvements I would go in the order above noting not to over do it on the fork oil weight and not to go to HD fork springs unless you're north of 200 lbs.

[sumran]

Good to hear from you. The bike is fabulous. I have visited the pictures and information presented several times and am currently visualizing scenerios on my own bike.

Based on your criteria, the HD springs are (sadly) appropriate in my case. I am looking to reduce some of the dead weight, but will probably keep the springs as I like the effect on handling while braking .

The feedback has led me to the conclusion that a fork brace might be worthwhile, but I doubt I will go any farther than that. I am fairly happy with the bike as-is, so I doubt that the benefit of the other items would justify the cost.

Again thanks for your story. The things you shared about your father made it feel like I met two riders sharing one motorcycle. I hope to meet you and see the CS in person someday.

[sumran]

trust me. idon't ride it hard. i'm fiftyeffingsixforfuxake!

And to think, after all those years, you still don't sit up straight when you ride!:rofl

[rinty]

Sumran:

On my '82 RS (since sold) I had Luftmeister anti bottoming springs with Progressive Suspension springs up front, and heavy duty Konis on the rear. The upper triple tree was replaced with a CC Products .060 aluminum one, and the swing arm was braced. This bike was very fast and handled wonderfully at all speeds and on all paved surfaces.

My tech does not use the fork brace, and I did not experience any front end squirm. Not using the fork brace eliminates potential binding from fork tubes that are not perfectly aligned.

Rinty

[The_Veg]

I have heard that frame braces (the ones that go on the sides, crossing above the cylinder) are only effective if welded to the frame rather than clamped.

[sumran]

I have heard that frame braces (the ones that go on the sides, crossing above the cylinder) are only effective if welded to the frame rather than clamped.

Definitely not going there! I might need to pull the motor to do all those hod rod modifications:D .

A reinforced swing arm that needed clean-up and paint just sold on eBay for almost $500! If I had known we were talking that kind of money, I might have decided I couldn't afford to start this thread.

[rinty]

If I ever got another airhead, I would just do the frame mods and would leave the engine alone.

I think the side frame braces are probably frosting on the cake. My frame modified RS handled superbly without them.

But the motor is what it is, and you can't turn it into an oiler engine by hopping it up.

Rinty

[ADAMLIVI]

I have heard that frame braces (the ones that go on the sides, crossing above the cylinder) are only effective if welded to the frame rather than clamped.

Yeah, I heard also from my restoration guy that they must be welded... but that too must be cautiously done not to weaken the frame.

[The_Veg]

Yep- welding frames is tricky business. The whole idea of those braces is to reduce the amount of twist-flexing that happens between the steering-head and the back-end, which is why the braces are at an angle instead of straight across. The difficulty with engine-removal is OK if you're a racer and have to tear-down the top-end on a regular basis anyway, but probably not worth it for anybody else.

[vanzen]

I have heard that frame braces (the ones that go on the sides, crossing above the cylinder) are only effective if welded to the frame rather than clamped.

This is completely untrue.
Fitting braces is not a situation where either the braces are helpful or they are useless – this in spite of a dogged prevailing attitude on Boxerworks.
Design and method of fastening are certainly factors that will determine where a given set of braces will fit into this range of functionality.
The method of fastening, if mechanical means are used, IS IN FACT CRITICAL to the effective function of such braces, but to claim that braces are "only effective if welded" is COMPLETE NONSENSE. The pre-eminent chassis / frame designer and builder, Tony Foale, rec'd. bolt on braces for the Type 247 as well as an effective method to attach them. Welding is simpler and easier in some cases, but not necessarily more effective, and often impractical to implement.

from Tony Foale, on the Type 247:
The main "weakness" of the BMW series /5 /6 /7 frames is in the area of the
SA pivot mounting. Side loads on the rear wheel will tend to make the
upright tubes holding said pivot move fore and aft.
This can largely be prevented by mounting a bracing tube on each side.
These tubes can be attached to high up on the front down tubes or to the
underside at the front of the mini backbone. At the rear I mount them above
the SA pivot. Some others put the rear mountings below the SA pivot (see
p182 of the Clymer manual 500-1000cc twins 1970-1979, October 1979) but the
under side is better supported by the bottom rails which are tied to the
rigid crankcase anyway.
****These tubes obviously need to be detachable*** for engine removal etc. and so
the detail of the fixing can be very important to the success of the mod.
I don't like the simple drilled flat brackets combined with a flatened tube
end that I've seen. I've used mating bosses with one counter-sunk at 45deg
and drilled and tapped, and the mating one turned with a male 45deg, the
other side counter bored for the head of an allen bolt. These are mounted
at right angles to the bracing tube and so the taper takes the main load and
the bolt simply holds them together, as long as the bolt is tight then there
is no slop, and I've never known the bolts to come loose.

Another though less important frame mod. is to put a short bracing tube from
the rear of the top of the head stock back on to the backbone, this will
reduce some distortion under braking.
Other than that the frame loop needs no other bracing, afterall it's heavy
enough as is.

The above refers only to the main frame loop, and is not meant to indicate
that the other factors mentioned by others, such as suspension units,
correct maintanence etc. are not important. You'll get no worthwhile
results from such mods. unless all the other bits are in good nick.

On machines with earlier engines there is one mod that I've found very
useful to help general handling as well as gear changing, and that is to
reduce the flywheel mass as much as possible, you just can't go too light.
Later engines had a different flywheel which was about as light as they
could go from the factory. Probably the easiest way to go is to use the
later flywheel assembly. It saves a lot of machining, drilling and
balancing work. Those BMW flywheels were made of tough stuff.

Tony Foale

(my emphasis added)

[rinty]

I understood that the later (post '80) flywheels were incompatible with earlier engines.

Rinty

[vanzen]

I understood that the later (post '80) flywheels were incompatible with earlier engines.

Rinty

The post 80 (1981 and on light flywheel) will fit an early** engine, however, either a 1981 or later trans must be used OR the input shaft and rear cover w/ actuating mechanism of an early trans must be swapped for the 81 or later input shaft and rear cover – which means reshimming, and then there are issues of the helical gears pressure face angle change ...
in other words – easiest to swap to a late trans.

**Up to 1975, the flywheel is retained by 10mm bolts, while after 1975 the flywheel bolts were upgraded to 11mm. So retro-fitting a post '81 flywheel to an early crank can provide some headaches. The flywheel ring gear changed after 1976, requiring a change of starter motor. Again, the starter motor would need to be changed for a pre'76 conversion.

[rinty]

Vanzen:

I might have guessed that some gifted mechanics / machinists would be doing these conversions. :)

The complication may be worth it because the lighter flywheel really is an elegant piece; more of a clutch carrier than a flywheel, perhaps.

Now to get myself another MG-B and swap a T-5 Ford tranny into it.......:laugh

Rinty

[vanzen]

"The complication may be worth it because the lighter flywheel really is an elegant piece; more of a clutch carrier than a flywheel, perhaps."

I am definately a fan of the late model "ring-gear carrier"
The light weight allows the Type 247 to behave like a motorcycle rather than a tractor.

[Polarbear]

Owning my /7 for near 30 years now and I like my heavy flywheel and won't change it. Its just me:). The handling issues/mods are all old school and been around since the 70's too. ALL good stuff:). I need more for mine too, as I've yet to add most of these to mine through the years. I have the springs, Koni's, fork leg braces from San Jose and nothing else. It still flexes under heavy loads, but still quite a nice ride and quick in the twisties for a 70's Beemer. Its funny, as the only one I've kept as many other newer BMW's have come and gone in thirty years! R100/7 bought new and I'm proud to have her still, ridden every day @ 300000+ miles now, too. Randy13233:thumb

[The_Veg]

Thanks Vanzen! That makes sense. And I don't believe everything I read on Boxerworks. :D
The stuff I post should be especially suspected.

Guys, Vanzen knows his stuff.