Top Fork Plate/Yoke for a R75/5

[Duane Ausherman]

This whole subject is one of controversy. How hard do you ride? Very few ride hard enough to need a stiffer fork. Back in the day, this fork was the stiffest of the major brands. Very few riders are good enough to even know the difference. Most that claim that it is better are just justifying spending the time and money on the hot set-up.

The real problem with the top plate isn't related to the stiffness. It is that the holes are punched in the wrong places. They won't allow the fork tubes to be aligned. So, you may think that the billet is better. Think again, as it isn't that simple. The holes in the top plate/billet must be the same at the lower clamp. The lower clamps aren't all made the same, so is the billet that you buy going to fit your lower clamp? Maybe, maybe not.

Riding straight down the road while touring, the stresses on the fork are equal on each side. You don't really need a better fork. If you have a single disc, then you have an unequal force during braking. If you have the drum or double disc, you have equal forces caused by braking.

While riding in a curve you have slightly unequal stresses. If you ride very hard in a curve, the stress is greater.

By far, the greatest improvement doesn't require a single new part, just align the forks. If you want to spend money on parts, then here is the list in order of positive change.
1. Floating bushings, they were supplied in 1972 and used after.
2. Changing the number of holes in the damper rods. I don't recall which adaption worked out best.
3. Changing the amount of oil in the fork tube to alter the rebound.

If you haven't aligned your forks, then any work with after market parts is just a waste. Info on my website.

We have gone over this dozens of times. Just do it.
The major is correct in his comments. For 95% of riders it just doesn't matter one bit. There is another advantage to a properly made billet top clamp. It fixes the vertical location of the fork tubes. That results in the axle fitting. It is very discouraging to put it all together and find that one fork is a few thousandths too high and the axle won't slide through easily.

[Major Softie]

Good simple explanation there Major, it makes sense!....though I'm alittle hesitant bout fitting a Bulky Billet Alloy Brace
mainly for wanting to keep a more Original look of my /5 around that area, and without having to trim headlight ears,
some even say they don't notice any difference with the Billet alloy unless you were racing it, I'm also hearing that fitting another lower Fork brace/Clamp would do a lot more towards stiffening and improving tracking of the front?...I wouldn't know myself.

Like Duane says, it makes little difference to most riders. I think most better riders can actually feel the difference - especially on bumps on turns - but there's a difference between feeling a difference and it really mattering to the rider.

Personally, unless I was building a cafe bike, I think the /5 is enough of a classic that it's better to keep it as designed. No amount of bracing is going to change the fact that those are skinny little tubes compared to modern suspension, and how fast you gonna go with your 50 hp and those drum brakes anyway on a 40+ year-old bike? I figure: keep it stock and ride it like it was built to be ridden, or put a GSXR front end on it and be done with it.

[Roy Gavin]

Mt experience is pretty much much the same as Duanes - on a R75/7 with 50,000 km on it and straight, well aligned fork the billet triple made little to no difference.

But on the well worn, bushless, forks on a 300,000 km R80 G/S , the billet triple, together with a tubular lower brace, the forks were much improved.

But the old bent and twisted flat top was fatigued to the the point that it was twisting in normal use, and would unscrew the top nut even with 120 ft/lbs torque, and any more than that crushed the head bearings.

It wasnt the flex that was the problem for me - I learnt to drive on a $10- Triumph and the little twitch of the bars to load up the suspension before you get into the corner becomes second nature PDQ , it was that the misalignment cased a lousy action, and I was riding it back to back with a well set up R100GS so it was more obvious to me.

Getting it all straight sure improved the action and compliance , but the feel and way it held a line didn't change a lot,

[ME 109]

but there's a difference between feeling a difference and it really mattering to the rider.

If one has wobble problems at 40 mph, one has 'things' that need to be addressed.
If one has wobbles at 120mph, relax. It's an airhead. What are you expecting.

Fix the wobbles at 40 (which a billet top clamp can't do, and shouldn't be expected to do imo) and the bike will be ready to benefit from a billet top clamp at 120.

Appropriately torqued top plates and fork braces and axle nuts should apply zero load to *perfectly aligned forks.
Top plates and braces are not tools to be relied upon to bring forks into alignment
As close to *perfect as us old bastards can get anyway.

A /7 should function well enough under most conditions as to not need added/modified bracing. imo again.
Racetrack riding not included.

Edit, If I don't get a gold star for this, that's it. No more trying. He's never given me one.

[PITAPan]

This whole subject is one of controversy. How hard do you ride? Very few ride hard enough to need a stiffer fork. Back in the day, this fork was the stiffest of the major brands. Very few riders are good enough to even know the difference. Most that claim that it is better are just justifying spending the time and money on the hot set-up.

I didn't spend anything. The PO did. It's better. (not to be contrary or anything )

It's not the good rider that notices, it's the less good one. Hit a bump in the sweeper and the good guy floats through and barely notices. The less good guy has his hands full clenching down on a bike slipping around. I've had better riders outride me on lesser machines. Had we switched they would have outridden me on my own. I need something several of orders of magnitude better to keep up (or more skills/balls).

I don't ride hard, especially in corners. I touch a footpeg down here and there, typically on a bumpy freeway on ramp, on the left, at low speed. But it's the bumps and ripples that matter. Even in a sweeper at speed, hit some ripples and the stiffer fork makes a difference. If the fork twists, that motion is not damped. Comparing the 100/7 with billet top and telefix lower braces to my K100RS, the /7 is almost as good. It is light years away from either the /5 or single disc /6, both unbraced---despite the greater weight (tho' lighter than the K).

The real problem with the top plate isn't related to the stiffness. It is that the holes are punched in the wrong places. They won't allow the fork tubes to be aligned. So, you may think that the billet is better. Think again, as it isn't that simple. The holes in the top plate/billet must be the same at the lower clamp. The lower clamps aren't all made the same, so is the billet that you buy going to fit your lower clamp? Maybe, maybe not.

I've never had identifiable misalignment except the time I rear ended a guy and fell over. (The /5 with /6 front) I resolved that with the bouncy-bouncy routine. Pull the top nuts so there is no pressure on the springs and the forks go up and down like silk. So some bikes may have poorly punched top plates that don't match the variation in the lowers---I personally haven't seen it. But I haven't seen that many bikes. While variation in manufactured parts is to be expected it can also be minimized (below what affects anything) by grading parts. BMW does this on some things--they might have done it on the front ends. You can also design the assembly so it is tolerant of a degree of misalignment. That means you can get as elaborate as you like later aligning things and realize no functional improvement.

GD&T has been around since WWII and it produces the kinds of parts that stack up nicely into very accurate assemblies. That's what it's all about. You can check your parts on a go/no-go fixture and either reject or grade them however you like.

You haven't fixed your website so I can't comment on the procedures you posted. (delete a couple lines of code to fix it) I have seen sites where someone was aligning the front end by bending something with a 2x4 and checking things with glass plates. Sorry, but I have to laugh. Establish misalignment by observing the action of the forks. If that's bad then fix it---but anything you can bend with a 2x4 will bend right back the first time you smack a pothole.

Riding straight down the road while touring, the stresses on the fork are equal on each side. You don't really need a better fork. If you have a single disc, then you have an unequal force during braking. If you have the drum or double disc, you have equal forces caused by braking.

Unfortunately touring doesn't involve riding strait down the road. And that road isn't smooth like racetracks. That's why you need a better fork. Even crummy touring on really strait roads. I've ridden real strait road all day leaned over about 15 degrees into the wind. Boy was my butt sore sitting on the edge of the seat. Some parts were strait and fairly flat but passed through cuts in close steep hills. The wind blasted down through the valleys between the hills and it could be tricky to hold the lane unless you anticipated as you came out of the cuts.

I've found touring loads can do all sort of weirdness. Too much weight far back lightens the front end. It gets unstable. More weight in one saddle bag, the wiggly passenger---you need all the chassis stability you can get. But the bumps in the corners are the big ones followed by parallel dropoffs in the pavement (Ride across the Sacramento river delta, any road, for all the pavement weirdness you can stand--but it's deadly at night---really that weird.)

While riding in a curve you have slightly unequal stresses. If you ride very hard in a curve, the stress is greater.

By far, the greatest improvement doesn't require a single new part, just align the forks. If you want to spend money on parts, then here is the list in order of positive change.
1. Floating bushings, they were supplied in 1972 and used after.
2. Changing the number of holes in the damper rods. I don't recall which adaption worked out best.
3. Changing the amount of oil in the fork tube to alter the rebound.

If you haven't aligned your forks, then any work with after market parts is just a waste. Info on my website.

We have gone over this dozens of times. Just do it.

Logical problem here.

For 95% of riders it just doesn't matter one bit. There is another advantage to a properly made billet top clamp. It fixes the vertical location of the fork tubes. That results in the axle fitting. It is very discouraging to put it all together and find that one fork is a few thousandths too high and the axle won't slide through easily.

The axle goes through the sliders. The vertical alignment of the sliders is the business of the the fork brace at the fender. This gets loosened every time you remove the wheel exactly so the sliders can align themselves in all axes when you replace the axle. If the height of the fork tubes at the yoke is 1/4" off the axle is not affected (but the spring preload and dampening is. ).001???.mmmmm...

The overall geometry is a pair of telescoping two rung ladders. The upper yokes are the rungs of the inner ladder, the fork brace and axle the rungs of the outer one. Fatter tubes and bigger rungs moves more forces out of the plane and increase the bearing area at the connections yielding greater rigidity (as in resistance to twist). Thus BMW going to bigger tubes, bigger braces, fatter axles, etc. They didn't do it for racing, they did it to make a better feeling touring bike. Something anyone can enjoy.

I shuttled a Katana 750 for a friend once--maybe 100 miles. Gave me an instant appreciation for just how bad the /5 handing was in every way. Gentle riding on someone elses unfamiliar bike with him following in the car. No Joe Racer going on---but just changing lanes was an eye opener. So the /5 was old technology--no need for dissatisfaction. But yeah, not too hard to tell the difference and I would opine that anything you can do to update will be noticed in the performance.

[boxertwinjeff]

I'm doing a Semi café job on the /5, Tommaselli Clubman bars
and alittle bling, wanting to have the top brace Chromed,....going to leave any other brace mods alone & stick to standard.
I found at 120mph,.. speed digitally verified.., the bike still felt nice & firm, so one would say the forks are aligned
correctly etc, could I have any dramas when refitting the top brace as in fork alignment or should everything be as it was?
excuse my ignorance, learning as I go.

[PITAPan]

I'm doing a Semi café job on the /5, Tommaselli Clubman bars
and alittle bling, wanting to have the top brace Chromed,....going to leave any other brace mods alone & stick to standard.
I found at 120mph,.. speed digitally verified.., the bike still felt nice & firm, so one would say the forks are aligned
correctly etc, could I have any dramas when refitting the top brace as in fork alignment or should everything be as it was?
excuse my ignorance, learning as I go.

if the lower clamps (lower fork yoke) are left tight, it will stay as it is. But loosen those and you have to do the full tighten-from-the-top-down routine.

If you ever pull the tubes and things are working well, it is good to index them so they go back, rotationally, just like they are. Things are good so preserve it. You make a tiny punch mark in the top brace with a very sharp punch and a mating mark on the top rim of the tube. And these things are tiny. I would mark the top plate now, with a punch or small filed V-notch--- just so it's under the chrome.

The hard red washers under the top caps seal poorly. Fat rubber o-rings from the hardware store work better, keeps fork oil off the plate--more clean with less work.

If you chrome the top caps (I have) a wrap of tape on your fork cap pin wrench keeps the wrench from scratching the chrome. Using a fat o-ring those things only get tightened gently.

The central cap nut is a rust magnet, not to mention getting chewed up by poorly fitting wrenches and technique. Think I'll paint mine---it just takes a lot of force for chrome to last and I can touch up paint in place.

I really liked the handling improvement with the lower bars. But I also cut them narrow. That hurt me (literally) one day making some violent evasive moves at low speed. No leverage but a lot was needed. My back hurt for a long time after that one, despite not hitting the ground.

[ME 109]

if the lower clamps (lower fork yoke) are left tight, it will stay as it is.

Torquing the fork nuts can misalign the fork tubes even with the triple tree tight. Nothing to say the triple tree is true.
Don't torque the fork nuts using the steering stops.

[boxertwinjeff]

Yeh, I'm buying Chrome fork caps,.. at the price their asking its not worth chroming mine,...also buying all new centre nut
casings bits etc, bar clamps polished & bar end mirrors,... never had low bars so should be fun,...as you & a lot of others say, handling improvement or atleast feels like it, my Tommasellis are adjustable which is great & these particular
bars will except my Switchgear being designed with the /5 in mind... so I'm told...should look Sweet, and reversible back to stock in a few hours if need be.

[PITAPan]

Yeh, I'm buying Chrome fork caps,.. at the price their asking its not worth chroming mine,...also buying all new centre nut
casings bits etc, bar clamps polished & bar end mirrors,... never had low bars so should be fun,...as you & a lot of others say, handling improvement or atleast feels like it, my Tommasellis are adjustable which is great & these particular
bars will except my Switchgear being designed with the /5 in mind... so I'm told...should look Sweet, and reversible back to stock in a few hours if need be.

The /5 switchgear goes with the /5 starter protection relay. Know how all that works. Gotta keep the switches out of the tank. They will hit a tank bag---that is why you have that relay and get to test the horn at left full lock.

The low bars put your weight lower and forward and more weight on the front end. It is fun and good for more speed and confidence diving into a corner. On the open bike it works for touring too as long as you don't have a lot of tailwind---you can lean on the wind. A long day with tailwind and your wrists can get sore if you aren't disciplined with your wrist alignment.

I would spend money on your throttle cam. If worn, replace it. You want the responsiveness and shorter throttle wind-up. The better solution is new controls and you want them anyway for the bar mounted MC for the dual discs on the front. My 90/5 would outrun the stock /5 brake AND a single disc /6 setup. Looked good but if you really want to run you really want to stop too. In the end the bike got parted largely because of this. Bad motor to brake ratio. I like to run.

You might look on the left frame downtube, sort of on the inside, for the boss for the /6 style hydraulic steering dampener. Works much better than the /5 friction one. You don't want it often but when you do you really do. My SWB /5 had that boss. The only advantage of the /5 style is locking down the steering for some tuning operations--Cinder blocks work too when needed.

Bear in mind you will likely be getting into different cables. So switching back to stock requires you keep the old ones.

Keep the /5 instruments out of the sun. Cover them when you stop---like with the plastic lid off a container of coleslaw or something. The needles warp up and rub the glass then you need new needles.

Watch for erratic instrument operation and disconnect immediately if seen. Cheaper repairs.

Do something intelligent with the fusing---BMW sure didn't.

If you are keeping the stock 75/5 rear drive, reinforce the alternator rotor. You are gonna need it.