fork brace fork clamp - installation notes

[gtgt_bangbang]

Pic.1 ; Paolo Tarozzi Fork Brace, a 5 component cast / machined aluminum assembly (Pic.1; two collars clamp around each fork slider + a bridge piece, all held together by 8 screws) , and a Mfg's name that is really fun to say with bogus Italian accent ...


I had previously aligned new fork tubes in a known flat lower yoke, clamping the tubes & yoke to a bit of a granite surface plate & checking layout with vernier calipers.
Everything was exceedingly well aligned before gently releasing the yoke clamps.

Results were great - it was a provable thing that the tubes were were dead flat / parallel & square to the yoke.
Even the tube ends were so co-planar ( same insertion length into yoke) , there was zero light under either end when assembly was set on-end on the surface stone.

I could put the top yoke ( clamping style) on the wrong end (lower end) of the tubes and it slooooowly slide down the entire tubes length with just gravity, like it was hydraulically controlled. Nice way to start off a good ride !

The sliders on the legs felt like buttah; took a couple lbs. pressure to get moving ( assembly oil only, no springs / no oil fill yet) , although there was a perceptible difference between the L & R sliders in force required to move (due to new rings & possible difference between surface prep inside the new tubes)

But no matter how I tried ( many times~ many ways) to torque the Brace screws, everything remained feelin good until the Brace was fully tightened down .
Then, slider motion was obviously & hugely hampered by the brace.

I had already trued up the Brace; flat-llapped the bridge bottom & square faced the bridge ends, squared the joints, relieved any corner interference, step-tightened screws in stages , ect, various snug-ups with axle & triple clamps holding alignment, ect, every assembly trick I could think.

The assembled forks continued to slide smoothly and easy as expected until final torque down of Brace assembly, then it was a heck of a work out to move it.

When installing the Brace, it seemed obvious to place the two collar's bores flat & fully on the machined fork slider tops (2nd pix) , since this resulted in the two "abutments" (the seats on the collars for the bridge plate ) checking out as parallel / co-planar to flatly seat the bridge.

When I took the Brace off again after many many snug-ups & slide tests & much worry & dismay, the bridge plate (previously flattened ) sive on the surface plate) was no longer flat; it was obviously re- tweeked. Clearly I had Hulked it. Of course its impossible to measure the fork tubes with the sliders and bellows installed ( nothing exposed to measure ! ) , but after disassembling most of the front suspension again, the fork tubes remained flat & parallel ( whew! I figured their alignment had been disturbed with all the force applied working the assembly ) .

Then I saw it and cant unsee it , like going down to the river first time & seeing sugar magnolia wading in a drop of dew.

Next time assembled , the sliders worked great as a unit, felt like two sticks of buttah but definitely headed the same direction together.

Pop quiz time ! Opened notes is OK ... who sees the problem ?
I'll post my answer later its time to beat the trash man to the curb

 

[gtgt_bangbang]

Brace collar & bridge distortion due to clamping screws

woah all the playas busy ! ok fair nuf.

The problem is seen in the sectioned picture above, the partial install;
solution pictured below

Note that when the Brace Collars are placed fully & flat , sitting flush down on the machined section of the slider tops ... ,
that the clamping screws are centered a wee bit below the irregular lower edge of the cylindrically machined section at the slider top.

Although the slider assembly ( including axle installed at correct length ) would move up/down on the fork legs fairly easily as long as the screws were only loose~snug,

upon final torquing of the collar screws , the aluminum collars are pulled off kilter, cocking or maybe just distorting the collars with respect to machined section & each other.
The distorted collar & collar-to-collar alignment then ruined the flat & level alignment of the abutments supporting the Brace bridge!

The whole assembly was almost un detectably distorted by the clamp screws

During the struggle sessions & various attempts to torque down the whole Brace assembly evenly and adequately,
the cocked / binding alignment of the Brace components, when fork assembly was lifted ( with increasing and yuge effort while lifting),
up to the much more rigid section of the fork legs ( just below the triple yoke) the strain was able to throw a permanent twist into the previously flattened Bridge Plate !

I had been measuring & trying to evenly split the gaps between each of the collar halves, but the cocking was small & the feeler gauge go/nogo measurements uncertain.

The twisted bridge plate was enough to throw the axle out of alignment with the two axle bores, where it had easily passed straight through before hand
This was actually the first clue as to what was bad wrong...

After again flat lapping the bridge, & trying best as possible to square the abutment pieces (dont have a mill , hard to create a precise angle & alignment)

and RE-locating the collars up a tad ... in order to center the clamping screws on the machined cylinder section, , the slider no longer caused significant binding.





once the collars are lifted up off the slider tops & the screws are well centered on the machined section ,
its a relatively minor trick to get all the pieces flat & square to each other, but easily done with carefulassembly & round-robin snug-up of screws.