Dual Front Discs

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Crab_Cake

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(I did a search but I didn't find much)


So when I got my 1980 650 the PO included an extra set of mag wheels (my bike has spoked rims) and a bunch of extra parts, including an extra brake disc and caliper.

My forks have a spot to bolt up the extra disc. What else do I need to get this thing working? I was looking at Mike's site and he has a front brake master cylinder for dual discs.

Screenshot2010-07-10at23557PM.png


Is this part all that I need to bolt everything up? Thanks for the advice, very appreciated.
 
Both caliper and bracket are different left to right you could probably get by with a wrong side caliper (bleeding might be hard) but you HAVE to have the LH bracket. The good news is that early XS750 and XS1100 use the same calipers and were sold in the US with dual brakes so they can be found.
 
I used to have all this stuff memorized, but it's faded away now. The XS850 is also one that can be included as a parts donor, right? As my fading memory recalls -- the XS750 and 850 twin disk rotors are smaller than the XS650's single rotor, but their calipers will bolt up to the XS650 forks and work with its disks. The XS1100's twin rotors are the same as the XS650s.

I've seen an XS650 on another forum that had a dual disk conversion done where it was using the smaller front rotors a la the XS750/850. The guy bought it that way, so he wasn't much of a help. I'd be interested in finding out what all's involved with that type of conversion, since it makes better sense to me.

EDIT: forgot to mention -- the above applies only to '77 and later bikes.
 
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Well progress has been slow but I am in the middle of a dual disk conversion myself. The donor bike needs to be early, 76 up to 78 maybe, they went to a different fork (bracket, caliper) style on the later bikes. To use the smaller rotors you need the 750 fork. That is what I am using. It gets a bit involved because 750 tubes are 1mm larger (a good thing) but the stem on the 750 is shorter so I ground out the weld on the lower triple and welded in a 650 stem. I got a pair of maxim rotors which are a lot thinner and are slotted. A single 650 rotor weighs 6.3 pounds the maxim rotors are 3.7 each (from memory) The rotors are bolt ons. I will need to check clearances I may have to put spacers on the calipers (or watch pad thickness) for proper range of motion. I have to replace the seals and have a set of mikes cartridge emulators I want to install but I am not sure if they will work in the 750 legs yet.
 
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It seems like this is a bit more involved than I originally thought. If I was to keep the stock brakes what is the best way to get better braking?

I am a big guy and I really want to be able to bring the bike to a halt quickly.
 
#1 Overhaul them and replace parts as needed.
#2 teflon lines.
#3 mess with different pads for improved performance.
#4 resurface the rotor or an aftermarket or slotted, drilled rotor.
#5 with Teflon line(s) you might be able to go to a slightly smaller master cylinder which should reduce the amount of finger pressure needed.
 
Crab_Cake said:
It seems like this is a bit more involved than I originally thought. If I was to keep the stock brakes what is the best way to get better braking?

I am a big guy and I really want to be able to bring the bike to a halt quickly.
Click to expand...

Especially gggGary's #5. #4 will trim some weight and will probably give you better performance also. MikesXS and 650 Central sell a lighter, drilled rotor that's a bolt-on replacement. It looks way cooler besides :cool:

I've tried various pads on my bikes. Michael "Mercury" Morse, owner of both 650 Central and Vintage Brake, can fix you up with a set of pads that will work well. I've been using the Ferodo Platinums he sells, and have been happy with them. MMM can also recommend a master cylinder with a smaller bore size, that will increase the clamping pressure substantially without increasing lever travel by an objectionable amount. Both Mikes and 650 Central sell the optimized MCs.
 
I had done a couple of dual disc set ups on one of my bikes and a project for another fellow and was pleased and displeased at the same time. Pleased with the braking but.....displeased with the added weight, effect on handling and a bear to bleed well. Ended up doing what I should have done first. Called MMM at 650 Central/Vintage Brake and followed his specific advice re disc cleaning, fluid change/purge and new pad installation front and rear (different) Vesrah & Ferrado pads on my 78 SE. Found that set up right my braking was more than adequate front and rear without the added weight of dual discs up front.

In any event and or either way Michael is the man when it comes to braking of 650's
IMO, us heavyweights included! Though the dual set up looks cool and does give extra braking I have since returned to single disc optimized as my preferred way to ride and stop. Best, Blue
 
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Quote
"brake lines consist of a Teflon® inner line that is covered with a layer of stainless steel woven braid. The Teflon® tube is very resistant to expansion under pressure and will not degrade from exposure to brake fluid. The stainless steel braid provides support for the Teflon® and the weave is extremely durable against incidental impact and abrasion."
End Quote
The Teflon is really the operational part of the brake line.
 
The 750/850/1100 calipers and rotors from the standard models are usable. The special calipers are not. The specials used a leading axle fork, this used a different caliper. They also used the 10.5 inch rotors.
If you do add the second caliper and rotor, try the M/C you have. It should be a 14 mm bore. This size works very well with two calipers. I have added a second rotor and caliper, Mike's braided lines. I ran one from an 82 Special. I thought it looked bad, it sloped for the buckhorn bars and looked like crap on my lower more standard bars.
I put the 16mm bore M/C from the Seca back on. It works ok but has less feel to it.
I'm gonna get a 14 mm from a standard bike or get Mike's 13mm bore M/C.
 
The guy I bought my 80 xs from had taken off the front end and put an xs1100 with duel disks on it. But the tubes are air over,and it rides very strange to me. If any one needs any of the parts for duel let me know . I already bought the springer for that bike and will not need the front end.
 
I'm in agreement with bluebikerblan on this subject. I don't think the additional unsprung weight is a good thing. If you can find lighter rotors then that may be OK.

On my 78SE, I have found the stock disc brakes (front and rear) to be easy to modulate and have excellent stopping power. I had a panic stop at an intersection this spring and was amazed at how powerful the brakes are. The brake pads I have are from Mikesxs and they do a good job, but sounds like 650central sells quality pads.

I drilled my brake rotors on my drill press. Its not hard to do, and I believe it improves the braking.
Dual or single front disc is a subjective matter...............they look cool so enjoy them if they work for you.

Oh yeah, almost forgot.............my discs were scored and looked poorly, so I turned them on my drill press and that cleaned them up nicely.
 

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Well, cooltouch, its not hard to do. I just made up a tool from metal I had laying around. A flat piece of steel is drilled with 3 holes and bolted to the disc with 2 bolts. I bolted another longer bolt to the centre hole and cut the head off the bolt.

Put it in the chuck and run the drill press at low rpm such as 200 or 300 rpm. I used emery paper to remove the grooving.............can't remember the grade but you can experiment..............probably 150 and then 200 or 250.

You of course don't want the disc surface to be super smooth, but they do clean up nicely. Once or twice a season I use some 80 grit sandpaper to rough up the disc surface...............I do this with them on the bike, and only rough the surface rubbing in a radial direction.
 

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