Standard Front Brake Upgrade

[TopCatGr58]

More thoughts and ideas.

Thanks Steve, I did search and find the link to the replacement OEM pistons, but I'm still wanting to do an upgrade of some sort. Was also looking at other types....wondering about the FZR 600 calipers, they are dual piston..but I'm not sure if they are the same size..they look like they used 2 different sized pistons in the same caliper, will check the microfiche soon.

Both the Harleys and the FZR's are solid mounted, do the Harleys use floating discs...do the 90+ FZR's use floating discs? The Harley ones even mounted on the Standards have to be mounted solidly, and so I would expect very close to the rotor at least on the INSIDE edge since the caliper body can NOT float/slide sideways to even it's position while grabbing the rotor??

YES I was/am planning on modding the Specials mount to allow a 2 bolt type configuration to mount an adapter plate to it!

I just checked, and there's quite a bit of space between the inside edge of the OEM caliper body and the spokes, so I'm hoping the FZR's aren't made too wide there so there'll be room for it to be mounted?? Any thoughts, I don't know how I could find the dimensions of the FZR calipers?

T.C.

[crazy steve]

You could use nearly any brand/type of caliper for a upgrade, but it might pay to find out ahead of time what parts cost; because there's so many different types of metric units, not all of them will be cheap to rebuild and you might run into issues with availability. That's one thing about HD stuff; no problem getting parts....

Also find out what the rotor thickness is on the source bike; the XS uses thicker-than-normal discs, make sure the calipers will fit them unless you're willing to have them machined down.

Floating rotors.... a good question, without a simple answer. Ideally, you should have a floating rotor with a rigid-mount caliper, but there's lots of examples that don't. Harley changed their rotor design when they went the rigid 4-piston units; they're still a solid rotor, but they cut a swirly pattern into the center to allow 'some' flex, kind of a 'poor boy' floater. They have switched to front floaters on most of their's as of the '12 bikes, but still use solid rotors at the rear. The FJ1100 forks I'm using on my 'modder' had rigid calipers and non-floating rotors as OEM, so it's not a necessitity. If your existing rotors are flat, I don't see why they wouldn't work.

And rather than remachining the Special lowers, have you thought about finding a set of LH/XJ lowers? I think those will interchange, and already have more suitable mounts cast-in while having everything else the same. Worth looking into...

Caliper width may be a problem; the Harley calipers are pretty shallow on the wheel side as they have to clear laced as well as cast wheels so there's lots of room. That may not be the case with sport bike calipers. As both Phil and I noticed, the FJ calipers got pretty close to the wheel....

[TopCatGr58]

Steve,

Well, the bikes have been made for 10 years or so, found out the pistons for the FZR 600 are 2 different sizes, available on PNM, also rebuild kits, the brake fluid line uses the same bolt as the XS11 so my SS lines will fit, or at least they will bolt in, but not sure if they will be long enough?

The replacement pistons appear to be gold/brass colored not steel? Not sure what they are or would be made of, maybe even anodized aluminum??

The pads are avialable in regular material at $20.00 a set/per caliper. But hopefully the pistons are not pitted?

As for getting some other forks, nope, wanting to do this more for folks who have specials that might want to perform a similar upgrade, I think it can be done without doing any kind of "damage" to the fork lowers, just that there's a rather thick section of aluminum as part of the bracket that holds the single bolt, I should be able to drill thru it to afix a bolt there as well as in the main oem location to provide the desired 2 point fixation. I'm figuring that I'll have to use a bracket with an "L" shape.

T.C.

[crazy steve]

I went and looked at a set of those, they look pretty wide on the wheel side....

Price is right through....

[TopCatGr58]

Update!

Update,

Well, after checking with several local H-D Dealerships and a custom bike shop, nobody had any leftover dual piston caliper sets. I didn't want to pay the $$ for them on Ebay, so I found a set off of a '05 Yamaha FZ600, they actually only have 2 pistons, not 4, and the caliper is mounted on a sliding mounting plate, so they will move to keep in good position over the rotor as the pads wear.

Steve, all of the fiche I've been able to see do not show the caliper body separated, but with the 4 piston types I assumed that brake fluid was needed behind all of them to squeeze evenly around the rotor, so there must be channels between the 2 halves, and that would complicate a bracket to widen the space to fit around our ~7mm wide rotors. This is why I decided on the 05 FZ600's dual caliper design, and being newer hopefully will not require an actual rebuild/replacement of the seals, just a good cleaning??

The FZ's rotor is only 4mm, the pads thickness are 4.5mm with 0.5mm minimum wear limit. IF I can't design a spacer bracket to widen the grip zone, then I could grind off 1.5mm of the surface of each pad, leaving 3.00mm, still 2.5mm more than the minimum wear, but hopefully I can make a spacing bracket to work! Will take photos and such WHEN I get it done!!

T.C.

PS, I did some simple calculations, measured ~40mm space between inside edge of our rotor and the wheel spoke. The 4 piston units pistons are 21mm long, 5mm for pad and 5mm for backing of pad, plus possibly another 5mm for caliper housing, = 36mm, possibly 4mm clearance from the wheel spoke...but without actual measurements of one, this is conjecture, and as stated above, the complexity of the brake fluid channels and a possible spacer..... why I opted for the dual caliper type!