Left side caliper for xs

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Walt51

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Hi Everyone I am new here
I have 2 xs650 78 &79
The question is, is there a left side caliper that will fit as the mag wheel is drilled and taped for a rotor on both sides and the fork tube (left) has mounting lugs.
 
yep. You need a left from a xs1100, or a british xs650, and a front rotor. they're not uncommon on ebay. Mike's xs has them new, and has the proper bolts, bolt retainers, and extended banjo bolt.

I would recommend getting the caliper new from Mike's, unless you can confirm that "caliper moves fine" is true. Else, you're going to be buying a new piston and rebuild kit anyway, and then you're well over what it would have cost you for a new one.
 
Yes, a new master cylinder would also be in order, while your at it, replace those 30 year old perished rubber hoses!
 
meh. The master cylinder is fine. Same one they used when they did put duals on at the factory. Oh yeah, replace the lines. The stainless steel ones are cheaper than the reproductions.
 
again, meh. While i don't dispute the 16mm master will give you a crisper feel, the stock one is, as i said, perfectly adequate to the task. Especially with the ss lines.

If you're that concerned, go get a 20 or 22 off some harley in the junkyard. Prepare to lock up the front wheel every time you get a little surprised. I prefer a more gradual feel. Still locks the front wheel at half a pull.
 
Let's do some math! Woo! I love math!

bore on the caliper is 38.1mm, = surface area of 1140mm
13 mm master cylinder surface area = 132mm
16 mm master cylinder surface area = 201mm

13mm single caliper ratio = 1140/132 = 8.63
13mm dual caliper ratio = 1140*2/132=17.27
16mm single caliper ratio = 1140/201 = 5.67
16mm dual caliper ratio = 1140*2/201 = 11.34

So, differences are 17.27/11.34, or 1.5.

What does this mean? Basically, all other things being equal, it will require 1.5 times the amount of pressure on the brake lever to apply to same force to the brake rotors with the 13mm vs the 16mm. But it doesn't matter, because you're applying twice as much braking force with two rotors, so you will still have a better response than with a single rotor.

Interestingly, in the article you referenced, if you check what his preferences are, (a ratio of 13 for single, 27 for dual), he'd have you running a 10mm apparently, or a 9mm if it went that far. Huh.

mastercylinder.gif


As another note, early XS's had a 22mm master cylinder - but that's because they had dual disc, dual piston.

As another side point, what *would* a 22mm ratio be?
22mm master cylinder area = 380mm (whoa)
22mm single caliper ratio = 1140/380 = 3
22mm dual caliper ratio = 1140*2/380 = 6

hm. That would be a *tight* brake.

Also, part of this ratio business is how sticky your pads are - and the stock pads just really aren't that sticky. Combine that with stainless steel which is slippery to begin with, and it's not an issue.

ps - by "sticky", i don't mean "won't stop you", i mean the tendency to suddenly stick, or grab, which is bad.

Cheers!:thumbsup:
 
Hmmmmmm, well I'm always happy to be wrong, that's how we all learn.
I always thought the late model calipers were 40mm. So if you ran 2 of these you (going by MMM's list) would idealy run a 5/8th m/c.

Yes the early twin discs ran a 22mm m/c, pretty sure they were 48mm calipers, so 4 active pistons. MMM sugests around a 19mm m/c for this!

P.S. I think your other brake theories are simarly flawed, too much for me at the mo though.

I guess Sundie, you have a fair bit to say, and that's great. You have an inteligent writing style. Unfortunately a fair bit of your stuff is not quite right. Your messages come across with a certain authority that the content doesn't always deserve. Sorry to be a prick, just need to put it out there for others to decide.

I fully understand if you hate my guts after reading this, though it's far from my intention. :cheers:
 
I do tend to pontificate, don't i?

I don't hate your guts, i just object to "i feel", or "check this information from people who know what they're talking about", or "it's my opinion", or "this is what this guy told me" handed out without critical analysis.

I wouldn't trust what someone told me here without thinking about it fully, being open to the possibility that i'm wrong, or that i'll i'll come to the conclusion that they're wrong. As you said, that's learning. Simply trusting what someone says is just learning by rote, and doesn't really bring you to understanding of the problem.

Getting back to the issue at hand: Which theories are flawed? That the brake compound and rotors on the stock setup don't have the same friction coefficient as upgraded newer tech? That following his chart (and his preferences, as he clearly states they are) would have us running a 10mm master? Looking at his reasoning, he's clearly picked a preference, (13 - 14) and multiplied that by the number of active pistons (which kinda makes a bunch of his chart redundant - he could of just said "match the master to a piston, it will work for however many you have", which wouldn't work, which tells me there's more math he hasn't thought about), and you're taking that as gospel. Where i'm looking at the stock numbers, and (using his math, which i've just noted may not be dealing with all the factors) seeing how close that matches, and figuring out that while yes, you reduce individual force, you double friction area, thus you'll have more braking than you did before for a given pressure, though it may take more pull to get to that pressure, it's still *acceptable*, and you don't need to go off and buy a new part.

I'd be the first to be saying "get a bigger master" if, for instance, you went to dual discs and you couldn't get full pressure from the stock master and you touched the bar when you pulled the brake lever - but this isn't the case, and the stock master locks the wheel at around 1/2 to 3/4 pull. This may be a factor of using SS lines everywhere (not as much expansion as the rubber ones, even new). Regardless, the stock 13mm master works fine for a dual setup.

I'm comfortable with differences of opinion, as long as it clearly stated that's what they are - not stated as "you don't know what you're talking about, i have the truth!".

The attitude of "you're wrong, but i can't be bothered to prove you're wrong" is disingenuous, at best.
 
Xs850's ran a left side caliper that's the same as xs1100. Just for more searching options for a used unit.
 
Sorry for hijacking the thread Walt - the only piece of advice (and it may work for you or not) is to simply buy the new one from Mike's and save yourself some possible aggravation. You *may* get a perfectly good caliper from Ebay, or you could get what i did - one that had water in it and was rusted in place. You *can* fix that, but by the time you get the rebuild kit and a new piston and add everything up - i was $10 shy of the price of a new one.

Good luck!
 
Sundie said:
That following his chart (and his preferences, as he clearly states they are) would have us running a 10mm master?
Click to expand...

Not sure how you came to a 10mm m/c there Sundie. The way I read it:

For dual discs with late model (single piston 40mm calipers) MMM sugests in the region of 16mm m/c.

For a single disc (single piston 40mm calipers) he sugests a 11mm m/c

For a twin disc twin piston (old style, 48mm) a 19mm m/c

& for a single disc twin piston a 13mm m/c
 
but they're not 40 mm, they're 38.1, and the chart shows 41, not 40. I did the calcs based on his formula, there are fairly large surface differences for small changes in radius, since you square it. My point being, the stock ratio is 8.63. So either his preferences are off, or the yamaha engineers were.

And going to a bigger master decreases the ratio, making it worse in his opinion.

My preferences are to not buy something if i don't need to. And while having a larger master would be nice (possibly, i don't have any practical experience) the stock will do the job fine (with which i *do* have practical experience)
 
It seems one of us is reading the chart wrong, if they are 38mm (though I was always under the impression they are 40mm), he recommends around 15mm for the m/c. At least the way I read it.
 
Well there is one other consideration to be taking into account here, that's Insurance. If you put a second rotor on your bike and use the single rotor MC and not the factory recommended MC then do not hot a $500,000 car or any accident for that matter, the insurance company will default you if they find out you are not up to factory specs.........Your choice on what MC you use but for a couple of extra dollars piece of mind works for me and as Yamaman said i ain't an expert either so i wouldn't want to play with my brakes
 

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