de linking brakes on a Cal Vin what size rear MC?

[lazlokovacs]

So... digging around in the parts books, it seems like the Cali Stone, with it's unlinked brakes, just uses the same master cylinder and rear caliper as the other Calis with the linked brakes... Is this right?

So I can source the correct front MC and then just use the existing rear caliper and MC for the rear??

Ps I've already read all the posts in the history of the guzziverse about why de linking is a bad idea

[John Croucher]

You will go smaller on rear and larger on front.  I don't remember the sizes.  You will need to change one front brake line.  I used a longer banjo bolt on the right caliper and ran a second line from the right to the left caliper. No need for a splitter.





Use HH Type pads on rear for a better feel. 

[Joliet Jim]

You will go smaller on rear and larger on front.  I don't remember the sizes.  You will need to change one front brake line.  I used a longer banjo bolt on the right caliper and ran a second line from the right to the left caliper. No need for a splitter.





Use HH Type pads on rear for a better feel.

Hey John, what front fender is that in your pics? I need to replace the front fender on my old Stone due to some rust I didn't catch last year or sooner.

Always wondered whether I'd notice a difference with linked brakes, but the single disk on the Stone front is mostly up to the task

[John Croucher]

Hey John, what front fender is that in your pics? I need to replace the front fender on my old Stone due to some rust I didn't catch last year or sooner.

Always wondered whether I'd notice a difference with linked brakes, but the single disk on the Stone front is mostly up to the task

It is a stock fender that has been cut down and chromed plated.


The rear is original cut down and chromed also. 


 

Saint Louis Metal Plating does automotive chrome repair.

[Joliet Jim]

 

Saint Louis Metal Plating does automotive chrome repair.

That is beautiful

[pressureangle]

It's been a while but I think I used a V50 front master cylinder on my '85 LeMans rear when I disconnected them.

https://photos.app.goo.gl/s9WhNDcQ8zjfvmLM6

[Frenchfrog]

Standard is a 15 mm so maybe a true 12mm for a single caliper
You'd need a piston and sleeve the bore unless the right master  can be fitted by fabrication.

[wrbix]

Guzziology has a nice discussion of master/slave combos - don’t know if this particular is covered but would start there.
You do have a copy don’t you? (Seems few references to Guzziology here of late…..)

[lazlokovacs]

if it was covered in guzziology I wouldn't be asking here!!

will try keeping the stock rear m/c (like guzzi did on the stone) and post the results

[John Croucher]

http://www.vintagebrake.com/mastercylinder.htm

This explains sizing and the affects of caliper i.d. 

To small and the brake lever feels like it neve pumps up.  To big and the lever is hard, but has no brakes.  Just right and two fingers will stop the bike. 

Brake pad compounds make a difference also.

It always amazes me that a small brake caliper can do more work slowing a vehicle to a stop from 100 mph than 500 h.p. can do getting to 100 mph.

[wirespokes]

If it's like any of the bikes I've converted, there's no need to change the front master - it's already overly large and adding a second caliper makes it just about perfect.

It would be nice moving to a smaller master in the rear, but for the earlier bikes than yours that I have - T3, LM3 and LM4 - no smaller master is available. The stock size will work but don't expect to lock up the rear. But it will work fine.

What's to lose? If you don't like it, get the smaller master for the front. Add another line for the left caliper, remove the line from the rear and plug the hole. I sweated over it the first time, but truly, there's nothing to it.

If there's a proportioning valve on the rear system, it's even possible de-linking will give stronger brakes.

[Turin]

I'm a fan of the 15mm master cylinder on my 850T with 4 piston calipers. It brakes like a modern sportbike. 16mm would also be a great choice for the front.
I'd try and find any rear master that will fit. 12-13mm

[lazlokovacs]

thanks guys, front is already sorted and I'm very happy with it (can't remember what size it is though!!)

My enquiry is really limited to the rear m/c

I'll be back in the garage with the bike in may so will update you all then

Cheers for the input

[blackcat]

I would email Gordon at MG Cycle, he will know which MC is correct for the rear brake.

[luthier]

I used a 12 on the front of my Cali3 way back when and that was a very good feel. But I left the rear standard and that hardly worked at all so it also should have been sleeved down. Strange to say I think they should both be 12.
But, now I'm back on linked brakes and they work better than my Ducati with a normal setup. Probably need new pads there.
Finally I just want to mention BMW linked brakes. Seems to me they got that part right. Of course they got hardly anything else right, but those brakes all work together , with a compensator, from the hand front brake lever.
Makes sense, you brake as you would with a car with abs and you get maximum of everything with that hand, but if you should desire to only operate the back one then you use the pedal.
I really can't understand why Guzzi had to be stupidly different about this, except it does work the Guzzi way, just it's slightly flawed.

[Dukedesmo]

I De-linked the brakes on my LM2, used a 12mm master on the rear and a 15 on the front - works perfectly.


Found a 12mm version of the same design as the original 15mm, except that it's 'reversed' as in it's designed to sit the other way round so needed to do some minor machining so that it fits like the original. Apparently they were used by other Italian bikes of the era that had conventional brakes; Ducati, Laverda etc.


Some info here if you're interested;   https://wildguzzi.com/forum/index.php?topic=91902.msg1451175#msg1451175 

[Klinkhammer]

This.
A little costly but very nice.
https://hmb-moto.de/Master-cylinder-PS-12-T3-Le-Mans-1-2-3-etc

[Dukedesmo]

Quote from: Klinkhammer on Today at 08:07:02 AM

This.
A little costly but very nice.
>https://hmb-moto.de/Master-cylinder-PS-12-T3-Le-Mans-1-2-3-etc

Nice piece but the seller of the new-old-stock master cylinder I bought still has them listed on ebay at $70; ebay item 363298063045 - requires a little work to fit but nothing too complex.

[rocker59]

I really can't understand why Guzzi had to be stupidly different about this, except it does work the Guzzi way, just it's slightly flawed.

I think Guzzi was stupidly first with the idea...  In 1975...

[wirespokes]

I think Guzzi was stupidly first with the idea...  In 1975...

Back then, a lot of riders were afraid to use the front brake. Guzzi made it impossible not to. But for those of us who use the front 90% of the time, linked brakes aren't a help. There are times I absolutely DON'T want the front brake, so linked can be scary.

Thanks for the link Klink - I'm seriously thinking of grabbing one.