JJUAN 32/30mm Front Caliper Binding?

[ESokoloff]

2016 Zero DSR 72k (ish) with 4-5 pad replacements. 
 

They seem to me that their dragging excessively. Using a fish scale it takes

3-3.5# of force to spin the tire when the brakes are warm from a ride & only

2-2.5# when cool.  
 

Can the square ring(s) never-used if I decide to split the caliber?

 

I’ve re-used bango bolt copper gaskets with success (after anneling & Re-serfacing.   
 

Tia 

[dirtrider]

7 hours ago, ESokoloff said:

2016 Zero DSR 72k (ish) with 4-5 pad replacements. 
 

They seem to me that their dragging excessively. Using a fish scale it takes

3-3.5# of force to spin the tire when the brakes are warm from a ride & only

2-2.5# when cool.  
 

Can the square ring(s) never-used if I decide to split the caliber?

 

I’ve re-used bango bolt copper gaskets with success (after anneling & Re-serfacing.   
 

Tia 

Morning  ESokoloff

 

"Can the square ring(s) never-used if I decide to split the caliber"?

 

Is this a mis-type? Are you asking if you can re-use the square edged piston seals? Or are asking if you can re-use the seals between the caliper half's (if your calipers even use those)?

 

If you are asking about the piston seals then you probably can re-use (stick them in clean brake fluid when removed so they don't dry out or swell up). Also try not to change their install direction as some piston seals are directional with a slight angular cut to them. 

 

Problem is: if you have dragging brakes & can't find corrosion or dirt causing the lack of pad return, or lack of smooth pad release,  then it might just be the piston seals themselves as the cut & shape of the piston seals are used for the initial slight piston retraction after brake release. 

 

Is your hand or foot lever allowing full brake pressure release?  If the small fluid port in the bottom of the master cylinder is plugged, or is not being cleared by the piston at brake release, then it can trap some pressure in the brake system (typically gets worse as the brakes heat up & the fluid expands). 

 

If you are asking about the seals between the caliper half's (then I'm not familiar with your caliper design) but if just standard square ended caliper seals then you probably can re-use (if you need to) but replacement is usually desired if you can find new proper seals.  

 

 

[Lowndes]

What brand calipers are on the Zero??

[dirtrider]

4 minutes ago, Lowndes said:

What brand calipers are on the Zero??

Morning  Lowndes

 

Look at his thread heading, says it has  J.Juan  calipers. 

[ESokoloff]

On 7/15/2022 at 3:47 AM, dirtrider said:

Is this a mis-type? Are you asking if you can re-use the square edged piston seals? Or are asking if you can re-use the seals between the caliper half's (if your calipers even use those)?

A bit of both (fat fingers & ignorance).

 

I did a bit of YouTubeing & found some good info here 

 

 

I contacted my (not so) local dealer via email asking about availability of new seals & waiting on a response.
 

Re master cylinder trapping pressure….

I hadn’t thought of that but certainly worth pursuing.
I will perform a test next week after I get home from work (brakes will be nice & warm). 
I’ll check the spin resistance & then crack the banjo bolt thus relieving any pressure & measure the resistance again. 
I’ll do this before ordering seals. 
 

Thanks for the input.  

[ESokoloff]

On 7/15/2022 at 3:47 AM, dirtrider said:

 

Is your hand or foot lever allowing full brake pressure release?  If the small fluid port in the bottom of the master cylinder is plugged, or is not being cleared by the piston at brake release, then it can trap some pressure in the brake system (typically gets worse as the brakes heat up & the fluid expands). 

I performed the “just got home from work” hot brake test and had 3.5-4# of pull resistance on the front wheel. 
I cracked the banjo bolt (guess I coulda/shoulda just cracked the lead screw) & voila..... pull force dropped to zero!!

I rode around the neighborhood a bit to re-warm brakes & pull was only 2# (brakes likely not fully warmed up).
I again bleed off pressure via banjo nut but this time there was no change.  
 

Also I heard back from the Zero dealer & no parts are available so I’m searching for a Brembo(?) solution now for rotor & master cylinder. 
 

Thanks DR for your help 

[dirtrider]

7 hours ago, ESokoloff said:

I performed the “just got home from work” hot brake test and had 3.5-4# of pull resistance on the front wheel. 
I cracked the banjo bolt (guess I coulda/shoulda just cracked the lead screw) & voila..... pull force dropped to zero!!

I rode around the neighborhood a bit to re-warm brakes & pull was only 2# (brakes likely not fully warmed up).
I again bleed off pressure via banjo nut but this time there was no change.  
 

Also I heard back from the Zero dealer & no parts are available so I’m searching for a Brembo(?) solution now for rotor & master cylinder. 
 

Thanks DR for your help 

Morning  ESokoloff

 

I am not familiar with the  J.Juan master cylinder but it should work the same as all master cylinders. 

 

If the master cylinder piston does not FULLY return all the way out then it can trap fluid pressure in the brake system. 

 

There is (should be anyhow)  a very small hole in the bottom of the master cylinder fluid reservoir. (basically a take-up port) 

 

What that small hole does is is two fold.  First it allows more fluid into the piston compression area with hand lever released, but it also allows any fluid pressure that remains in the brake system to escape after brake lever release.

 

If that small hole is plugged then any brake fluid pressure remaining in the system (like from heated fluid from riding) can not escape back into the fluid reservoir  (so that can cause brake drag).

 

Or if the master cylinder piston does not FULLY return or fully retract all the way out then the piston can keep the take-up port hole covered (any chance the front lever to piston push rod  (or whatever links the lever to the piston) was ever adjusted or messed with?

 

If the lever stop, or push rod, (or something) does not allow the piston to fully return then that can keep the take-up port closed & not allow full fluid return.  

 

The other very/very slight possibility is a delamination inside your front brake hose causing a sort of one way check valve situation allowing fluid to pressurize the front brake OK for normal stopping  but not allow all the fluid pressure to escape back to the master cylinder. (unlikely on a newer motorcycle but still possible)

 

 

[ESokoloff]

One thing I failed to mention is that the bike has a Bosch ABS system but I don’t know how it works IE if that makes a difference.  
I do know that the unit is silent (unlike my 03 RT’s whizzy brakes.