adding second brake caliper-?

[doubletrouble]

I bought a brake rotor for the left front side of my 81' H from e-bay recently. It was listed as a late seventies xs650 and it matched the overall dia. and the bolt pattern was the same. When I got it in the mail it had a thinner braking surface,but I thought i could live with it, but the left side brake caliper bracket is hard up against the rotor surface. its just a little too wide overall?
My question is, do I need to find an 81' front brake rotor or is there any production years that will work? Did Yamaha make rotors with thinner braking surfaces?
Any help would be great!!
DT
(winter is half over!!)

 

[inxs]

- youre correct, there are different diameters, thicknesses and offsets... i dont know very much about this topic yet so cant specifically help you, there is some info filed in the tech section under 'brakes' that may help you...one day, hopefully, someone will pull all the info together and write the brake bible

 

[grizld1]

DT, you have an incorrect part there. The same front rotor--Yamaha part no. 1J3-25831-00-00--was used on all XS650 models equipped with 35 mm. forks and floating calipers, from the 1977 D-model through the close of production.

 

[doubletrouble]

So grizld1, I think you are saying that any front rotor from the 77 D-model and later will work,is that right? I havn't seen anybody listing rotors with Yamaha parts numbers on e-bay yet. Anybody else have any imput on this? I know I'll be asking sellers for more info this time.
thanks!!
DT

 

[KevC]

Found some basis information which seems to be very similar to the Minton mods here
http://www.biker.net/650/dual_disk.htm
Im sure there used to loads on this subect, I looked at loads of stuff before converting mine to a Fazer Blue spot Caliper, better braking & much less unsprung weight But cant find what I remember seeing now
Maybe it was on 650Rider

 

[KevC]

As grizld1 said, part number for disc is 1J3-25831-00-00 from 77 on
Here are a few that are very similar part numbers, the ones in blue are an exact match.
Cant be sure about others but sure I read somewhere a SR500 disc fits but is 3mm thinner

EBC do a decent replacement part # MD2024LS (left side) MD2024RS(right side)

1J3-25831-00-00 Disc, Front Brake XS11002H9, XS11002H9, XS11003X0, XS11003X0, XS1100E, XS1100E, XS1100F, XS1100F, XS1100G, XS1100G, XS1100SF, XS1100SF, XS650SG, XS650SG
(Also XS500, XS750 77 on)

10M-25831-50-00 Disc, Brake XJ1100J

1J3-25831-50-00 Disc, Brake Rear XS650SG, XS750-2D, XS750-2D, XS750D, XS750D, XS750E, XS750E, XS750E-227501, XS750E-227501, XS750F, XS750F, XS750SE, XS750SE, XS750SE-311211, XS750SE-311211, XS750SF, XS750SF, XS850G, XS850G

3H5-25831-00-00 Disc, Brake XJ1100J, XS1100H, XS1100H, XS1100SG, XS1100SG, XS1100SH, XS1100SH

3H5-25831-10-00 Disc, Brake XJ1100J, XS1100H, XS1100SG, XS1100SH

3J2-25831-00-00 Disc, Brake XS850H, XS850H, XS850SG, XS850SG, XS850SH, XS850SH

3J2-25831-10-00 Disc, Brake XS850H, XS850SG, XS850SH

4H1-25831-00-00 Disc, Brake XS850LG, XS850LG, XS850LH, XS850LH

4H1-25831-10-00 Disc, Brake XS850LG, XS850LH

4H3-25831-00-00 Disc, Brake XS11005K7, XS1100LG, XS1100LG, XS1100LH, XS1100RH, XS1100RH

4H3-25831-10-00 Disc, Brake XS11005K7, XS1100LG, XS1100LH, XS1100RH

4H3-25831-50-00 Disc, Brake XS11005K7

4W1-25831-50-00 Disc, Brake XS1100LH

 

[doubletrouble]

thanks kevc, thats some great info. new(used) rotor is on its way!!

anybody need a front brake rotor from a mid seventies xs650? in perfect shape. $25. includes shipping

DT

 

[KevC]

DT
Also have a look at this thread by 80xs650
Rotors that fit XS

 

[XSLeo]

Some of the xs1100 rotors are 5 mm thick instead of 7 mm thick. The ones I used on my 75 are 5 mm thick. On the left side is where the axle clamps to the fork. loosen the fork clamp bolts and move the fork over enough to center the caliper over the rotor. Tighten the clamp bolts. Good to go.

 

[inxs]

- if i understand right youre suggesting pinching the forks inwards to centre the discs...wouldnt that upset the long term fork dynamic and increase wear on the seals?

 

[doubletrouble]

I would never do that. By bending the fork outward in order to center the rotor in the caliper it would increase play for the speedo drive exposing the wheel bearing abit. Not to mention messing with the fork and possible handling issues.
I would rather keep a single brake rotor than have to worry about all that crap...

 

[KevC]

Some of the xs1100 rotors are 5 mm thick instead of 7 mm thick. The ones I used on my 75 are 5 mm thick. On the left side is where the axle clamps to the fork. loosen the fork clamp bolts and move the fork over enough to center the caliper over the rotor. Tighten the clamp bolts. Good to go.

I believe some rotors are thinner (SR500? for one) but as the caliper on the XS is floating & even with a 2mm thinner rotor, that only puts it only 1mm off centre, assuming the rotor offset does not compensate for this. The floating caliper would certainly compensate for this, otherwise you would never be allowed any wear in your brake pads. (one pad is fixed and the whole caliper slides when braking)
Pays to keep that sleeve, bolt and rubber cover greased up so the caliper is free to move

 

[grizld1]

The correct procedure for installing a thinner rotor is to install spacers to reposition the caliper mount to reduce the distance between the rotor and the passive pad. The piston will reposition itself, taking care of the active pad. It isn't difficult; just get the passive pad as close as you can to the rotor without dragging, using new pads.

 

[650Skull]

The XS650 rotor is is not to be used if less than 6.5 mm thick. Why ? these rotors do warp if they are to thin so why would you put on a thinner rotor.........An SR500 weighs a lot less than a XS650........... I would not like to have the weight difference of the 2 calipers on the front wheel, also an insurance concern if one rotor was undersized

 

[grizld1]

Second that, Skull! You'd want the rotors matched on a 2-disc setup, that's for sure, and even with light rotors that's a lot of unsprung weight added to the front end. Much can be done to improve stopping power with a smaller MC, braided stainless lines, and upgraded pads. But minimum thickness has less to do with bike weight and caliper design than with the design and composition of the rotor. I used a slotted 5 mm. OEM rotor from an XS850 IIRC for some years before switching to a still lighter semi-floating rotor from Mike's XS--a very good item, BTW--and finally to a full-floating Brembo rotor from 650 Central. You can really feel the weight difference, and stopping power with Vesrah sintered pads and 11 mm. Brembo MC is light years ahead of OEM.

 

[KevC]

Why even bother going for a twin disc set up, with all that added unsprung weight, when so much can be done to improve the single disc set up.
Like grizld1 says

......... and even with light rotors that's a lot of unsprung weight added to the front end. Much can be done to improve stopping power with a smaller MC, braided stainless lines, and upgraded pads. ........and finally to a full-floating Brembo rotor from 650 Central. You can really feel the weight difference, and stopping power with Vesrah sintered pads and 11 mm. Brembo MC is light years ahead of OEM.

Even better with a caliper off an R1
HERE

 

[XSLeo]

I'm using two 5mm thick XS1100 rotors. The right side lined up ok. The left side was off almost enough to rub on the caliper bracket. I moved the forks about 1 to 1.5 mm. I don't think this will cause any handling or wear problems. It handles just fine, to soon to detect any wear.
The European bikes came with the dual rotors. Perhaps some one from there has a manual that explains just how the second caliper lines up.
I have an '03 Harley Super Glide Sport. It has dual disc on front. In the repair manual it explains how to line the rotors up. With everything installed you tighten the axle nut, this lines up one rotor. The other rotor get lined up by putting a 7/16's drill bit through the hole in the end of the axle. Move the fork over till it just touches the drill bit, tighten the clamp bolts. If this works on the Harley forks it should be ok on our 650's.
I agree that a single disc setup has certain advantages.I like the look of the dual setup, mine works very well.
Like everything that we do to our bikes a single or dual setup is just personal preference. Keep a bike stock, chop it, tracker, bobber, hardtail whatever, it's just personal preference.

 

[XSLeo]

Doubletrouble, moving the fork over on the axle won't expose the bearing or effect the speedo drive. All that is pulled to the right when you tighten the axle nut.

 

[inxs]

- european models have 2 x 267mm disc with floating pad mounts in the calipers...no need for fork pinching when setting these up

 

[650Skull]

Two important things here.

1: the distance from the back, ( the face that sits against the hub), to the back of the rotor, determines where the rotor sits in relation to the caliper.

2: tighten the axle nut before you tighten the axle clamp on the left end of the axle. If you tighten the axle clamp first, then tightening the axle nut will pull the bottom ends of the forks together.