Would you put dual disc on a 72 XS2

[CalsXS2]

I have every factory part I need to do a dual disc set up.

Now I have to decide if I want to stick with the original plan and put the dual disc brake set up on the 73 TX750. Which was a factory option. And that's what the parts were bought for.

You see it's turned cold here and I'm not working on the 73 in the cold garage. So it could wait until spring. But it's a running bike. I don't have to put brakes on it.

Or I could put it on my 72 XS2 650 that I put a TX750 front end on. I know there's not any of those running around with dual disc. I just don't know what to do. BTW. It's in the house so I can work on it,,,lol. And I have to put some kind of brakes on it. Could just as easily be dual disc.

 

[CalsXS2]

WOW!

There's been 85 views and not 1 opinion. Come guys. At least say it would look stupid on a 72. Just say something.

 

[retiredgentleman]

There's no value received by using dual discs on these bikes. I proper working single disc will give good braking. The second disc/caliper just adds more unsprung weight, which reduces the ability of the front suspension to do its job.

Guys that add the second disc, do it for the "look", and don't care that it actually adversely affects the front suspension.

These stock discs are heavy compared to modern discs, so best to not add that extra weight.

Yes, I know that some models in Europe came with dual front discs. However the Euopean discs had smaller diameters.

 

[gggGary]

We will assume you are using non 72 wheel the 72 wheel cannot dual disk. I'm with RG on this one, use a lighter single disk with fairly small MC and the best pads you can find. I don't have this set up dialed in for an early double puck caliper yet.

 

[Xmarksthespot]

Dual disc is a good look, bike won't go fast enough to need it, might be a bit concerned with the extra weight, blah blah blah. However if it's the look you like, why not, not going to see to many others like it. You will notice the extra front end weight should you stuff it in a corner without other mods. Have fun with the build.

Nice you have it in the house, don't think my wife's sense of humour is that good.

 

[CalsXS2]

We will assume you are using non 72 wheel the 72 wheel cannot dual disk. I'm with RG on this one, use a lighter single disk with fairly small MC and the best pads you can find. I don't have this set up dialed in for an early double puck caliper yet.

I would be using a 73 wheel and rotor. Remember my TX750 fork swap thread.

I was really only wanting to do the duals on the 72 because I have all the stuff. I could get the project farther along and have the brakes done. It's a real money thing for me right now.

If I keep the 72 original brake set up it will be tax time before I do anything. I need new lines and a master rebuild. I'll try taking it apart and clean it though and see how it looks.

I was really on the fence rather to do the duals on the 72 or not. I needed someone to talk me out of it. I think I'll still put them on the 73 since it was a factory option.

Thanks guys.

 

[5twins]

As mentioned, it's over-kill and really not necessary. If you really want to do something that will help, add a fork brace. Heavy braking really applies a lot of twisting force to the forks on a single disc set-up. It was very evident on my '78 with the later forks. My guess is the effect on older forks would be just as bad, if not worse.

That old style caliper with two moving pistons is actually supposed to be a better stopper than the later single moving piston caliper. All cleaned up and in good working order, one should be more than good enough.

 

[650Skull]

Australasian market XS's that came to Aus and NZ had twin disk set up from 76 and later models. 77 and later had twin larger front disks, the same as the States have on the front

Safety standards a very stringent over here, could be the reason they went for the twin disk set up to stop the twisting of the front forks in an emergency stop?

What ever the reason that's what we lived with and the bikes still got us there in piece, baring stupid mistakes or crashes

 

[CalsXS2]

The original factory option was just a second big disc. Look at the pic below.

Is the fork twisting you guys are talking about only with a single disc. Don't forget the TX750 has a beefier front end. Would I have this twisting issue.

I'm not road racing. I still have the chicken strips on my new tires. Hell. I still have them on my 82 Susuki 650,,,lol. I'm not a thrill seeking rider. I just put around. And when I do get out on the highway, I do try to do "DO THE TON". Don't think I ever made it except on the Suzuki.

That being said. I think since I all ready have the parts, and it was an option and all, I'm for sure going to dual up the 750.

I could the take that brake system off the 750 and put on the 650. I just hate to tear into the 750 right now, out in the cold.

Hmmm. I wonder if I I could fit it in the bedroom with the 650.

 

[650Skull]

The fork twisting is something i have had in the back of my mind and never gave it a hell of as lot of thought. When 5twins mentioned it i figured it may have had something to do with why our countries went for the twin discs.

I honestly don't think it is a factor unless your going to be racing to the next intersection and braking hard. In average normal every day use, a single front disk is going to be fine. Hell the early XS650's with their 34mm forks are still around.

Great brochure.

 

[kopcicle]

Okay I'm sure this has been addressed elsewhere and to death but I'll bite .

The attachments are from my long running project "The Red Bike"

The "Heritage Special" came with dual disc . So what ?

I did the dual disc and admittedly it's the later calipers and rotors but ...

I do have a point . That extra rotor and caliper are like 7 pounds of crap that doesn't need to be hung off that axle just to think you can stop better harder faster quicker .

I did it anyway . The bike is a period piece and so are the brakes . If I wanted it to stop it would be a FZR something or other rotor and disc . For that matter it would be a whole modern front end .

I did it anyway because I had the parts and the time and ...

Okay for your application it can be done but should it be done ? I did it to a TX500 some years back and what i remember it was a pain to change the front tire .

If you understand that leverage in a hydraulic system is surface area of the M/C piston to surface area of the caliper piton then sizing a M/C to the additional area of a second piston should be easy . If not then find something on hydraulic ratios , read , and read again .

This is one of the few times I'm going to ask you to do as I say not what I do .

Now if you want to put a disc on a spoke rear that's a whole different deal .

So to recap;

second disc , heavy

second caliper , heavy

not worth the extra weight in stopping power

modern disc and caliper is better

complete front end is best

Its entirely possible I'm full of crap and have no idea what I'm talking about .

~kop

 

[jetmechmarty]

I don't have any of the old stuff. I just weighed the late model rotor and it comes in at 6.75 lbs. The late model aluminum caliper without any pads is another 1.85 lbs. I'm sure the early stuff is much heavier and the caliper is mounted on the wrong side of the fork. Unless the bike is strictly for display in your living room, the second brake is a bad idea. Besides, we get a good view of the lovely spokes on the non braking side.

Have you ever gone too fast over a speed bump in a four wheel drive pickup truck? That's what unsprung weight feels like.

BTW, that's a lovely TX750!

 

[kopcicle]

You can make adjustments to the dampening rod and or use "real" cartridge emulators but why ? Again it's a (corrected) 9 pounds of pork on the axle that can not be justified by the additional stopping power .

Again , I did it because [insert ridicules reason here]_____________ [/insert ridicules reason here]. Not that i don't care what anyone has to say about it (I do actually) I did it anyway and that is the way it is .

~kop

 

[CalsXS2]

Just for the record, the old big stuff rotor and caliper weighs around 8 pounds. I guess my scale could be off trying to weigh something that light. Each time I weighed it, it read about a pound different.

 

[CalsXS2]

I just want to make sure you guys know I'm scrapping the dual 72 idea. I'm talking about the 73 now.

Another just for the record.

This is quoted from a TX750 only Austraillian forum where there's a lot of dual disc's.

"The standard disc measures 298mm (11-3/4") diameter Calvin. Euro TX's were the same, not smaller. If you use the single disc master cylinder (16mm) with the twin discs you'll get much more than a minute improvement in braking performance!!"

 

[jetmechmarty]

Don't do it to the TX, either!

 

[650performance]

AHRMA 750 Sportsman road race bikes do just fine with a single disc. Add a fork brace, new steering head bearings, flush and bleed the brake with new fluid, add emulators and get some upgraded brake pads from Michael Morse at Vintage Brake/650 Central and the bike will steer and stop better than ever.

 

[CDNTX650]

I made a bracket to fit a 2 piston brembo caliper from a ducati monster. Was doing some front end work today and forgot how rediculously light it is....i bet the pads weigh the same. The old cast iron was like 3 of these calipers together. Now i get to fit some nice galfer organic pads too.

 

[grizld1]

I'm surprised this didn't get mentioned, but if you alter the hydraulic leverage with a smaller MC (a very effective improvement), you need to replace rubber brake lines with braided stainless. The old line is probably shot anyway; every Japanese factory manual I've ever read specifies 4 years as max service life for rubber lines.

 

[CalsXS2]

I'm surprised this didn't get mentioned, but if you alter the hydraulic leverage with a smaller MC (a very effective improvement), you need to replace rubber brake lines with braided stainless. The old line is probably shot anyway; every Japanese factory manual I've ever read specifies 4 years as max service life for rubber lines.

I all ready have them.