Tech Tip: Assembling Special front and LH/XJ rear calipers

[crazy steve]

I'm posting this one as I found that alignment seems to be pretty critical with these. There's been lots of reports of problems with these not quite working right, and particularly if you got a 'project' bike where these may be disassembled or if you're unsure if the PO put them together right or you suspect missing/wrong parts.

Before attempting installation of the Special fronts, make sure the forks are aligned with the rotors centered in the slots in the forks. This isn't an issue with the LH/XJ rear. Got it aligned? Let's go...



Here's the needed hardware. You've got the long mounting bolt, make sure this isn't bent, even slightly. If it is, you should replace it. There should be a washer under the bolt head, this is to prevent the bolt head from eating away at the aluminum caliper body. Next is the pivot sleeve; this is what you bolt down tight and the caliper pivots on this as the pads wear. Note the o-ring on the end; this is important. This performs two functions; one, it helps 'seal' the sleeve from 'stuff' that may prevent free movement. Two, this acts as a 'bumper' to allow the free play but prevent rattling. A 9/16 x 3/4 x 3/32 o-ring will work here if yours is missing. Last, there's a thick washer. The one I have here isn't original, but was fitted.



All bits in order on the caliper. Time to bolt it on....



This is where you want to check for proper clearance. With the mounting bolt tight and the caliper pushed towards the mount, install your pads. Keeping the pads firmly against the retainer, try slipping in the pad retaining pin. If it drops right in, you're good. If you have to pull the pads away from the retainer to install the pin, the washer is too thick. This can put stress on the mounting bolt and sometimes bend it. If you have to force the pin in, the washer is too thin and you won't get free movement of the caliper. If the retainer is missing (even if you have the right parts), you'll have an 'extra' .030" clearance between the pads and the mount, which may cause problems with the bolt. In this case, the washer needed to be .200" thick due to the homemade retainer.

Questions or comments welcome!

[Rasputin]

The mounting bolt on these should never be tightened to the point that the brake assembly will not freely move. The bolt is to be tightened only enough to allow movement of the caliper. Then the lock nut is installed to basically double nut the bolt so it does not move. Most Common mistake on these front pads is to overtighten the bolt and then tighten the lock nut.
Do that and you will guarentee yourself problems with your brakes. If the bolt is so tight that the brake can not freely move what else would one expect?

[crazy steve]

Uh, there's a torque spec for that bolt you say shouldn't be tightened. And a separate spec for the locknut.

If tightening the caliper bolt causes it to not move freely, you have an alignment problem and/or the wrong parts and/or in the wrong order...

[Rasputin]

I do not find those specs in my Yamaha service manual. The Clymers I have does say to torque the bolt to 18 ft.lb but says nothing about the nut. I am not saying it aint so, I just would like to know where you are seeing this so I can check it out.

[crazy steve]

Not easy to find, but it's on page 9-27 (Yamaha '78-80 combined FSM, SF supplement) in the torque specs....

'Caliper and front fork (8mm bolt) 19.0 ft-lbs (8 mm nut) 14.5 ft-lbs'

It's even more problematic on the rear LH/XJ brake, as you don't have a locknut....

[crazy steve]

After thinking about this for a bit, I think I see why so many owners have had trouble with these.

The manuals give virtually no direction about mounting the calipers, and make no note of any 'special' considerations that should be taken when doing so. But if you aren't aware of the 'fit' of the parts, it would be extremely easy to mis-install these and never know until you have issues. I suspect that all the reports of bent bolts are from this cause.

First, the manual merely says that 'it is not necessary to disassemble the brake calipers and brake fluid hoses to replace the brake pads'. I'll go further and say that you shouldn't install the calipers/pads as an assembly unless you're positive you have the all the right parts in the right places and order, and I'm not so sure I'd do it even then. If you install the caliper only (no pads) onto the rear bracket or front fork first, making sure it moves freely, then when you install the pads you'll quickly know if the alignment is off by using the method I outlined above. If everything is right, the pads will install easily. If they don't, you've got missing/wrong/misplaced parts. Loosening the main anchor bolt to 'fix' it merely masks the problem, and leaves open the likelyhood of bending the bolt. With the larger-diameter sleeve and washer firmly clamped against the mount, they have much better leverage against bending forces. Loose, all of that force will be transferred to the bolt...