Leading Link procured. Want to "float" the brakes. Need help.

[rodekyll]

Hi!

I've found an early "UNIT" leading link front end to replace my raked trees. Part of the my motivation is driveability and part is that the LL more suits the visual style of the rig. I've gotten through the basic re-dimensioning of it to fit my unraked trees (Moto Guzzi 45mm), but I'm having a real problem getting the brakes set up.

The heart of the problem seems to be the oem mounts (dual caliper setup). They are intended for a certain Brembo caliper and a certain disk size. I'm ok with the caliper size, but I've got 320mm disks, and the mounts are welded in and spaced for ~180mm.

I can change rotors but I don't want to lose the extra area. I can replace the mount lugs in a better location for 320mm disks. I can find someone's caliper, somewhere, that has a proper mounting arrangement for the angles and distances, while maintain the piston sizes (not bloody likely). None of these solutions "improve" the OEM design, which I am told (but don't fully understand) is flawed.

Or I can abandon the OEM mounting altogether and use a floating design, which I am told (but don't fully understand) eliminates the issues of a fixed caliper mount. I have studied on the pictures you folks have posted to try understanding how to build the floating brackets, but I could use an essay or two from the folks who have done it and know.

So . . . why float them? How do I float them? What are the pitfalls to avoid while tinkering? Must I do both sides? Most important -- pics of how it was done on your build. Thanks!

Here's a look at the trike in question:

[stacebg]

Hi!

I've found an early "UNIT" leading link front end to replace my raked trees. Part of the my motivation is driveability and part is that the LL more suits the visual style of the rig. I've gotten through the basic re-dimensioning of it to fit my unraked trees (Moto Guzzi 45mm), but I'm having a real problem getting the brakes set up.

The heart of the problem seems to be the oem mounts (dual caliper setup). They are intended for a certain Brembo caliper and a certain disk size. I'm ok with the caliper size, but I've got 320mm disks, and the mounts are welded in and spaced for ~180mm.





I can change rotors but I don't want to lose the extra area. I can replace the mount lugs in a better location for 320mm disks. I can find someone's caliper, somewhere, that has a proper mounting arrangement for the angles and distances, while maintain the piston sizes (not bloody likely). None of these solutions "improve" the OEM design, which I am told (but don't fully understand) is flawed.

Or I can abandon the OEM mounting altogether and use a floating design, which I am told (but don't fully understand) eliminates the issues of a fixed caliper mount. I have studied on the pictures you folks have posted to try understanding how to build the floating brackets, but I could use an essay or two from the folks who have done it and know.

So . . . why float them? How do I float them? What are the pitfalls to avoid while tinkering? Must I do both sides? Most important -- pics of how it was done on your build. Thanks!

Here's a look at the trike in question:

not sure i understand the problem... why not weld tabs on the LL so u can use the stock brakes?

[rodekyll]

Why float the calipers? Because from what I understand (imperfectly, but researching and learning), having the calipers fixed behind and under the axle causes the front end to rise under braking, and the front wheel to scrub on the pavement -- skid. Floating the calipers, if I can achieve the proper parallelogram, should solve the rise/drop under braking and should not contribute to the front wheel skidding. It seems to me that if I have to dig the welder out of storage I ought to be using it to improve the braking, not to preserve what appears to be a design flaw in the front end. What I'm seeing in my innernick research are a lot of different ways to incorporate the same elements into the brake mounts:

An axle-borne bearing or bushing connected to a bracket.

Bracket connected to a caliper.

Caliper bracket then held to the VERTICAL tubes of the LL with an adjustable turnbuckle strut having heim (rose) joints.

The axle bushing allows the caliper to revolve around the centerpoint of the wheel.

The caliper seems to want to be about vertically-centered on the wheel.The strut needs to be a close parallel to the swingarm.

The strut needs to be a turnbuckle to adjust for rise or dive.

I have a pair of Tokico radial mount calipers and a couple pair of Brembo axial mount units to experiment with. I'm inclined toward the radial mounts, since I can make a bracket from simple angle stock. If I use the axial mounts then I have to mill exotic shapes, and I don't have a mill. So unless anyone has a reason not to, they're my first choice.

I think I can use standard 2rs wheel bearings for the axle end of the mount. The question is how to fasten the bracket to the bearing. I was thinking about drilling a full hole in the bracket, inserting the bearing, and spot welding, since there will be no "force" on the rotating part. Anyone see a problem with that approach?

Initially, I'm contemplating a simple muffler clamp on the vertical tube to anchor the turnbuckle. Then I can slide it wherever I need to for the "sweet spot" of neutral rise/dive. A welded tab can come later.

I'm finding myself in an unexpected time crunch. I've got the telescoping front end removed and the LL rough-installed. I had anticipated a week to collect and fit the other bits, and a few days to sort out the best geometry. But I got a message this AM that a good friend in TX (I'm in WA) got balled up by a truck while riding. He's broken both arms, some ribs, clavicles, spinal processes, toes, and a leg, along with the other rashes and bumps that happen when you get squashed by a truck. He's 75 and lives alone with his cat. I think I need to speed this up and get down there to help him. Someone needs to antagonize the cat while he's laid up.

So any thoughts, answers, tips, would really be helpful.

[LarryA]

Sounds like you should reinstall the orig. fork, lash the leading link fork on the back of your trike, and head for Texas.....you can work on the LL down there! the homemade LL fork on last winter trike does raise the front when you brake.....but I find that the front end raising up, more to my liking, than having the front dive down.... kinda like stopping a horse! I think a floating caliper refers to the sideways motion of the caliper?? not the radial motion of the caliper when brakes are applied ?? all cars have their calipers floating sideways but ridgidly mounted to the knuckle....my .02 Larry

[rodekyll]

It sounds like you mounted yours rigidly to the swing arm. I could do that easily enough with a shaped spacer, but I lack a mill for shaping, and the spacer would be 1/4" thick -- more than I want to whittle. So I'm going to put the effort into trying to improve on the braking, instead.

In automotive terms, you're right -- a "floating caliper" refers to a caliper that has pistons on one side only (single-sided), and "floats" on pins to self-center on the rotor as the pads grab. In the Leading Link context a floating caliper is one that is fixed at the axle by a bearing or bushing and bracket with a "reaction rod" sort of strut. The bearing or bushing at the axle allows the caliper to move freely, or "float" around the axle, like a wheel bearing, while maintaining its relationship to the rotor. The reaction rod prevents that float. It sounds like they're working against each other, and they are. I'll try to explain. I hope someone corrects me if I'm not understanding it correctly.

A rigid caliper mount is generally done below the swing arm, behind the axle. This means that when the caliper grabs the rotor, it wants to rotate with the rotor in an upward direction. Since it's mounted to the swing arm, it levers the rear of the arm up, and the suspension rises. To a point. Then the same grabbing and levering limits further suspension travel, and the suspension "locks up". This causes the tire to start bouncing and skidding, and both braking and steering forces become less or non effective.With the floating setup, The axle point moves (acts) with the swing arm and moves up and down with the suspension, just like the fixed caliper.

If the reaction rod was also fixed to the swing arm, it would in effect be a rigid mount. But in a floating system, the reaction rod is fixed to the vertical fork leg, which does not move with the swing arm. The rod itself has heim (rose) joints, which float both ends of the rod. Floating both the rod and the axle point allows the caliper to rotate around the axle as the axle moves up and down So the jacking tendency is negated.

Ideally, the rod is positioned parallel to the swing arm, and the center of the caliper arc is adjusted (the rod is a turnbuckle) parallel to the vertical fork, making a parallelogram. Theoretically then, the levering on the swing arm is completely neutralized and suspension remains even during braking, but is still free to move with the road surface. So you don't get rise or drop, you don't bind the suspension, and you don't skid or lose steering in a hard stop.

If you want a little rise, you can change the rear rod mount point lower than parallel or shorten the rod. For drop, do the opposite. This allows you to compensate for any other braking anomalies.

At least that's the way I understand it. I'll know better once it's built.

[LarryA]

Think I understand......transfer the braking torque to the fixed fork tube instead of the swing arm. I see that the swing arm rise could indeed max out to the point of no suspension left.....causing the loss of steering and braking, that said, front heavy trikes can lay down a lot of brake before this happens. I do think the idea you have is well worth persuing....what I'm thinking is of using a part of a motorcycle drum brake housing,which contains the axle bearing. or modeling a caliper mount after its principle.....maybe a laser-cut piece, with a thicker boss welded on for the bearing bore?? Larry

[vwbug72501]

Maybe a different approach: http://www.chopcult.com/forum/showthread.php?t=37074

Caliper / bracket already designed. Install on axle or reposition pivot bracket to fit?

[LarryA]

Looks good to me.......might be just what rodekyll needs....

[rodekyll]

Think I understand......transfer the braking torque to the fixed fork tube instead of the swing arm. I see that the swing arm rise could indeed max out to the point of no suspension left.....causing the loss of steering and braking, that said, front heavy trikes can lay down a lot of brake before this happens. I do think the idea you have is well worth persuing....what I'm thinking is of using a part of a motorcycle drum brake housing,which contains the axle bearing. or modeling a caliper mount after its principle.....maybe a laser-cut piece, with a thicker boss welded on for the bearing bore?? Larry

With the conventional teleforks I've had bad diving under braking when the weight shifts forward. If I stab the front brake only on anything other than clean, dry pavement, the wheel bounces, locks up, and I lose braking and steering. Depending on the weight in the bed of the trike the effect can be large. I've tinkered with the telefork suspension -- spring rates, shock fluids, etc., and can't find a combination that both handles this weight transfer and rides comfortably. I can choose one or the other.

Part of the weight transfer solution of course is to use some rear brake to trim the front. I plan to do that with the unique design of the MOTORTRIKE rear calipers. These have three 1-inch pucks per caliper. The two outside pistons operate on one hydraulic circuit, and the center puck is on its own circuit. I plan to link those center pucks to the front brake control, using a 3/4" Nissin radial M/C and a 2# residual pressure valve in the rear brake line to help with the increased lever stroke. This way I'm always trimming the rear brakes a little bit when the front brake is engaged. It will have no effect on the rear brake operation, other than to make the rears 30% more effective when I'm using both pumps.

I think I've got the physical layout of the floaters sorted. I'll have pics later , but I'll describe now:

My axle sets up with spacers to center the wheel. There is also a spacer inside the hub to keep the roller bearings (not tapered) spaced and tight. When I draw up the axle nut all the spacers and bearings become one solid stack along the axle. I needed to float a mount point around those spacers that center the wheel.

I found bushings to make spacers from at the local farm supply. I "machined" a couple of shaft collars to ride on the outside of the bushings, and then relieved the bushing bores to slide nicely on the shaft. With the bushings in place and the wheel assembled, the shaft collars can spin freely around the axle bushings and also float sideways, toward or away from the hub.

I'm using Tokico radial mount 2-pot calipers from a Suzuki. The radial mount simplifies the bracket work. Instead of milling out a serpentine plate to make the awkward mount points of a conventional caliper, and then do an offset to center the caliper on the rotor, I can make radial mounts with simple angle iron.

For those angle irons, also at the farm supply I found some fence mending hardware. They have right angle plates in 1/8, 3/16/ and 1/4", up to about 9" long and 3" wide. They should be perfect.

Today I plan to locate the pivot center for the 1/8 plate stock. To do that I need mount the Tokico brakes to the plates and pump them up to clamp them by their own pressure in the optimum arc. When they have their natural center, I'll measure to the centerpoint of the axle, drill for the shaft collar, and weld the plate to the collar.

Then I reassemble everything for reals, connect rear brake line, bleed, and ride. End of story, I hope.

For the complete conversion to Leading Link, I'm in less than $100 in hardware right now, including false starts. Oddly, the turnbuckles and heim joints were the major expense. I have about 16 hours into actual work (head scratching and scavenger hunts don't count) over the course of three days. This includes removing the teleforks and reassembling the fairing, dash, and other things displaced by the construction.

The donor LL cost $500, and some custom welding (I want certified welds on the LL) to fit to my forks @$200. I have returned the steering to OEM rake, and have a trail of about 3.25". The axle rides about 1.5" higher than the swing arm pivot. If I have the theory and execution right, this has been a very cost effective mod. I hope it works as well as I hope it works.

[stacebg]

i find the axle above pivot point 1 to 1-1/2 gives a good ride i think you will find 3-1/4 in of trail may be a tad much but if you have adjustable pivot mnt thats not an issue as for the floating brakes... i like the anti dive .. non floating.. then if you hit a bump while hard on the brakes you have a lot more travel to suck up the said bump....

all the LL i have done are that way never an issue with losing control or any thing like that....if you go with floating..... where you attach mount to the leg will have no bearing on how much dive you get or dont get the"connecting rod" is there to stop the caliper from turning on the axle an although it seem as it would matter... it dosent... the attachment on the caliper OR on the leg could be any length at all ... up by the handle bar if you like.. no difference... only thing... the further from the axle the attachment on the caliper is,,, the less stress on your connecting rod...

also if you want to try you can always mount the connecting rod to the swing arm to try it

hope that makes sense

stace

[LarryA]

stacebg.......just thinking general principles here.......rodekyll's reaction rod or rods terminating to the fixed fork tubes would be highly desirable on a rear eng vw trike with a light front end where front wheel traction is limited. but on a front eng trike i would think the swing arm mounting would be just fine......if the front end got high, some rear brake should bring the front down.

to rodekyll......what kind of fenders are you using front....and rear?

Larry

[rodekyll]

Well, I have one side done, pending arrival of heim joints for the turnbuckles. I'm pleased with the result, even if my welds were sloppy to begin with (this is steel, I usually do aluminum). In the end I opted for 3/16 plate stock rather than the 1/8. The caliper moves around the axle smoothly, and no whirly bits interfere with by non-whirly bits as things go 'round. It's centered slightly above the brake rotor's center, but still in full contact with the rotor surface. I'll build the other one 1/16 shorter.

I've got a light front end by you guy's standards. It originally had an OEM Moto Guzzi telefork setup from an '03 EV, and a Lester mag from the '70s with a 120/18 Metzler 888. It's mid-engine, but it's an aircooled Moto Guzzi motor, and no transmission. So even with my burly 165# added, it's a bit anorexic. The combination of the light front end construction and the motorcycle tire contribute to the skidding I get under heavy front braking.

The fenders front and rear are from a Moto Guzzi Jackal/stone -- the untarted Guzzi "California" line. They are steel.

Still have pics to post, but I'm more excited about starting the other brake mount.

[rodekyll]

i find the axle above pivot point 1 to 1-1/2 gives a good ride i think you will find 3-1/4 in of trail may be a tad much but if you have adjustable pivot mnt thats not an issue as for the floating brakes... i like the anti dive .. non floating.. then if you hit a bump while hard on the brakes you have a lot more travel to suck up the said bump.... all the LL i have done are that way never an issue with losing control or any thing like that....if you go with floating..... where you attach mount to the leg will have no bearing on how much dive you get or dont get the"connecting rod" is there to stop the caliper from turning on the axle an although it seem as it would matter... it dosent... the attachment on the caliper OR on the leg could be any length at all ... up by the handle bar if you like.. no difference... only thing... the further from the axle the attachment on the caliper is,,, the less stress on your connecting rod...

also if you want to try you can always mount the connecting rod to the swing arm to try it

hope that makes sense

stace

I'm not sure what you mean by 3-1/4" trail being "a tad much". Do you mean it's been reduced too much, or that it is still too much?

I'm in the ballpark of 1.5" rise on the axle. I need to sit on it and have someone else measure it.

I appreciate the comments about the connecting rod. If the angle of the rod doesn't matter, it makes finding a mount point easier.

I got the other mount welded up and roughed out. Cutting a 2" hole in 3/16 plate takes a while. All I have is a little tabletop drill press. I start with a hole saw bit and lots of wd-40, which cuts a groove in the surface. Both sides. Then I go around the circle with a smaller bit, drilling as close to the previous hole as I can. Takes about 36 holes, following the groove. Then I use the hole saw bit again and it chews right through it. Not recommended for finish work, but I welded a bushing into the hole, so the raggedness didn't matter.

I'll give it a trim and paint in the morning, reassemble it all for the unteenth time and move on to fitting the fender.

[stacebg]

I'm not sure what you mean by 3-1/4" trail being "a tad much". Do you mean it's been reduced too much, or that it is still too much?

generally i find around 2" works but i do like em very light

[stacebg]

stacebg.......just thinking general principles here.......rodekyll's reaction rod or rods terminating to the fixed fork tubes would be highly desirable on a rear eng vw trike with a light front end where front wheel traction is limited. but on a front eng trike i would think the swing arm mounting would be just fine......if the front end got high, some rear brake should bring the front down.

Larry

agreed with the 1st part.... but dont thing any amount of rear brakes will bring the front end down

[LarryA]

stacybg.....just figuring.....that if adding power lifts the front wheel.....then braking the rear wheels would transfer weight to the front wheel.

[stacebg]

stacybg.....just figuring.....that if adding power lifts the front wheel.....then braking the rear wheels would transfer weight to the front wheel.

you would think so... heck i would think so.. but doesnt work that way...when u hit the front brakes the suspension goes right to full extension and it takes more than brakes to move it

[LarryA]

Staceybg...I for one, have not even tried this on my trike. Just assumed a large weight transfer would make the front come down. I will give it a try soon. I'm sure it will be as you say, because I am anchoring to the swing arm also......Larry

[rodekyll]

Staceybg...I for one, have not even tried this on my trike. Just assumed a large weight transfer would make the front come down. I will give it a try soon. I'm sure it will be as you say, because I am anchoring to the swing arm also......Larry

If it was just a weight transfer issue, you'd be right -- braking transfers weight forward. But with the brake caliper under the swing arm and behind the axle there's a physical, mechanical levering that takes place when you brake. The fulcrum is the axle, the force is the rotation of the caliper around the rotor, and the load is the pivot of the swing arm. As the brakes are applied, the caliper (and therefore the swing arm) wants to follow the rotor around its circle. The direction of rotation levers the pivot of the swing arm (and therefore the trike's front end) upward. No "braking" occurs until the levering force of the rising swing arm end is "stalled" by the weight of the trike.

Now if you hit a bump while the the swing is caliper-locked/arm rising, what happens with the suspension? Will the front still rise against the springs, or is the suspension effectively locked up? My imagination says that the front of the swing arm can't rise when the rear is already rising and locked by the caliper. My imagination sees that the entire front end will hop as though there were struts instead of springs at the spring position.

Any thoughts on that (because I can't know . . .)?

[LarryA]

just guessing here.....if you were braking and the front had raised to max, then you hit the bump, I would have to think the suspension springs would start to compress,after the braking torque was exceeded.....in other words your suspension suddenly has stiffer springs. if the front wheel dropped in a chuck hole,the down travel of the suspension is already used up and the trike front would drop further???? Any how I'm interested, but confused!