Brace or no brace. that is the question, Whatson

Reading the latest post on fork brace's. Can any one tell me how they work?
Now dont think i have not done the maths on these.and trawled many race paddocks,suppling the Lansdowne Manx kits as opened many doors.

by fitting a brace i assume the forks are free or helped to be free from vertical twist.

I was in the paddock with S. Tonge he held the front wheel between is knee's Manx no brace]and pushed the bars side to side, and yes the forks allowed a twist to incure.
Surely the stanchions where not bending,possibly the wheel spindle?
I guessed the stanchions allowed a twist? if so a clamp between the sliders,with just a screwed insert in the oil seal holder thread is not going to provide a firm hold :?:

I think forget the brace and fit twin disc's....

Ugh, I can tell ya what I discovered, when going fast enough you barely have time to snap forks one way then the other to cut a turn before flying off edge of the world, the front tire is twisting bottom of forks one way while pilot and power is twisting top of forks the other way, the forks twist up, then rebound, so by time pilot imput hits the forces have combined to over shoot desired aim, OR fast pilot imput to tire gets delayed by fork twisting up to happen in time, SPLAT. It can begin to feel like rubber bands connect yoke to axle. Unless ya really get kinda nutzo or have to recover a nutzo situation fork brace is undetectable but for its added mass. Braced fender from factory does help on its own too.

Fork brace does two things at once, both stiffens up forks so less twisting and also raises the twist frequency above those the tire can react too. It tends to take out some imbalance of striction or spring/dampening side to side by tying sliders together.

Forks can twist because there is no real connection between the tubes and the stanchions. Also because of the great distance between the axle and the triple clamp. Adding a brace helps strengthen these.

Think of the fork assembly as a rectangle. Because it's relatively long there is not much twisting resistance, and even less because of the sliding action. So by adding a brace you now shorten the rectangle and increase the resistance to twisting, much like triangulating a frame.

Buddy bought my old triumph bobbed and put 8"over fork tubes on it. The amount of flex between the wheel and bars was unreal! This in combination with the "flop" from the new rake made the bike basically unrideable. I had a fork clamp laying around so we put it on at the uppermost travel of the sliders and the flex was greatly diminished. The bike still looked stupid thoough. And YES I did tell him that. Funny though, he sold it two months later for way more than he paid me for it! :?

Chris/Dave agree, Good picture Dave by the way, So ,,,,,,,lets do the Flex Test, We assembly with out the sliders,a pair of triple tree's and two stanchions, Clamp the yolks on a bed , place two Dial test clocks on each stanchion end, Now we PRESS one stanchion down, to produce a deflection What as happend? Well i guess we have distorted some thing? Proberly bent the stanchion [with in its elastic limit] other wise its now no longer straight, when the applied load is removed.

Now fit the sliders onto the "bolted down" stanchions IN APPROX THERE NORMAL RANGE, we have increased the length , reset the D.T.I on the stanchion wheel area,

First thing we notice is the DTI will move without much effort! Because the slider as ROOM to move due to the clearance inside BUSH/BORE
Fitting a brace will not remove this BUSH/BORE play, PLUS we have increased the leverage.

A brace will not offer any intial support ,simply because the sliders and bush's are "Loose" we have offered nothing Because the Brace is NOT CONNECTED to the other stanchion directly, But to a "Sloppy" tube on the other side!
I hope this all makes sence to someone.

john robert bould said:

I hope this all makes sence to someone.

Click to expand...

I think I get it, tightening up the front-end makes more sense to me than the brace. That's too bad as the brace looks good!

Vince

I designed a set of fork lowers, cast in one with the brace, basically an inverted "U".

They probably would have gotten people killed, so I never built a prototype.

Actually, casting aluminum, then boring the tubes accurately, would have been WAY beyond my capabilities and anything I could source nearby at that time. Maybe I'll have a go, now that i have much better resources.

Seems like a simple design that would work...

grandpaul said:

I designed a set of fork lowers, cast in one with the brace, basically an inverted "U".

They probably would have gotten people killed, so I never built a prototype.

Actually, casting aluminum, then boring the tubes accurately, would have been WAY beyone my capabilities and anything I could source nearly at that time. Maybe I'll have a go, now that i have much better resources.

Seems like a simple design that would work...

Click to expand...

I hope beng dosn't read this, all hell will break loose! The fecal matter will hit the rotational air dispersment unit!

bwolfie said:

grandpaul said:

I designed a set of fork lowers, cast in one with the brace, basically an inverted "U".

They probably would have gotten people killed, so I never built a prototype.

Actually, casting aluminum, then boring the tubes accurately, would have been WAY beyone my capabilities and anything I could source nearly at that time. Maybe I'll have a go, now that i have much better resources.

Seems like a simple design that would work...

Click to expand...

I hope beng dosn't read this, all hell will break loose! The fecal matter will hit the rotational air dispersment unit!

Click to expand...

:lol: :lol:

If you have money to burn then buy a fork brace, but if you want to improve handling put the money towards modern type rear shocks, and a cartridge upgrade kit for fork internals.

Fork braces and cartridges have two totally separate functions, producing affecting handling in very different ways (both complimentary)

john robert bould said:

A brace will not offer any intial support ,simply because the sliders and bush's are "Loose" we have offered nothing Because the Brace is NOT CONNECTED to the other stanchion directly, But to a "Sloppy" tube on the other side!
I hope this all makes sence to someone.

Click to expand...

It seems you are trying to make a point, not ask a question.

Bracing the stanchions will add some support, but with drawbacks.

What you really want is a front end like this...

I ain't speculating that I've got scary fork twist up- spring back delay and over reactions until I put on RGM brace. Brace did not help the slight blurring of the sliders moving fro/aft d/t the slack in slider bushes on stanchions fit, but it was a total non issue on directional control or tire grip > going in and out harsher than I could approach on tract bike or my SV650. Can't ignore the effects of rear patch pivoting through rear iso to slap front iso silly which is felt in fork wiggles but is not coming from the forks. If forks don't twist up as much or twist/untwist at fast enough rates they cause less upset to rear grip on leans. There may be much better modern forks or Roadholder upgrades but I ain't been able to upset Peel anymore no matter what, so I"m done with handling mods just seeking more power and less weight to see how bad I can embrass the elites on track days and my own solo fun in public roads and woods.

john robert bould said:

Chris/Dave agree, . . . .lets do the Flex Test, We assembly with out the sliders,a pair of triple tree's and two stanchions, Clamp the yolks on a bed , place two Dial test clocks on each stanchion end, Now we PRESS one stanchion down, to produce a deflection . . . .the applied load is removed. Now fit the sliders onto the "bolted down" stanchions . . . First thing we notice is the DTI will move without much effort! Because the slider as ROOM to move due to the clearance inside BUSH/BORE . . . . Fitting a brace will not remove this BUSH/BORE play, PLUS we have increased the leverage. . . . . But to a "Sloppy" tube on the other side!

Click to expand...

John - With a single disc or a TLS drum, the twist is a complication no rider needs, especially if trail braking.

Imagine that the stanchion is a male splined shaft and the sliders are internally splined female to match.
Can you now see that the twist is also a function of the ROTATION of the sliders around the stanchions?

To me, the solution is stop that twisting by way of a fork brace that has lots of depth front to rear AND that is bolted to each of the sliders by bolts that are at least 4" apart from each other, front to rear. That is, while bolting to those little fender brace/mounting studs is OK, it would be better if the mounting bolts were in front of and behind the top of each slider and at least 4" apart, or more.

Also, at the other end of the slider, a large diameter axle, clamped by both sliders, will complete the job.

Pastbacksideslider, I'm going to try to do Peel similar to you wider braced design to take knock downs better and hit fender high animals to knock down on aggressive power. I made a hole in arc of RGM brace to hold fender in past but gives place to triangulate crash bars off the slider ends.

About all the fork braces that I've ever seen are capable of is preventing bowing of the forks. They never have the strength or purchase on the sliders to be begin to have any other effect. When you put a modern tire on a set of Roadholders it shows up the limits. It's an old school fork and always will be. Modern conventional forks have big bore axles with 4 bolt caps and strong lower yokes with broad clamping area with 2 bolts. Which came first, the great tires or the great forks?

Great imput Bpatton