Would these fit my stock '87 and be an improvement ???

[Country Joe]

Ron,
You had the same thought that I did, as far as checking flex of the calipers.  I guess I can do a flex check of a blue dot caliper. Honestly, I don't think .010 flex is much at all.

George,
 My FZR wheel just got delivered  by  the FedEx man today, I will hang it on my digital scale as soon as I get back home. It looks like Wills Rim Repair did a bang up job in straightening the pothole dent. t

[ribbert]

.....but the rotor should be held steady by the opposed pistons.

That's assuming a 100% equal initial force by the pistons. A few thou initial deflection in the disc doesn't take much and with a dial indicator on one side only it's possible that as more force was applied and the pistons centred, the disc move back to it's resting position.
The fact these are floating discs may well account for some movement too, both visual and as a mount for measuring.

I can't believe I got sucked into this again.
No more.

I'm more fascinated by Arnie and CanDmans hair at the moment.

Noel

[Capn Ron]

Cap'n, the real figure is likely less. You should measure it with no more pressure than required to lock the wheel, a couple of fingers worth. In reality, even that would be an exaggerated figure because nearly all braking done with road use is at way less than max. Very hard road riding is probably only going to see 75% of that.
It also remains possible that all or some of that measurement is disc flex.

Noel

Yeah Noel, that's exactly right.  The flex in the real world would be FAR less as I was applying a *ridiculous* amount of lever force!  My only purpose in going to the extreme was to establish a baseline of maximum flex of the OEM caliper in the worst case scenario.  Which really isn't a riding or braking scenario at all...just how much stiffer might the blue dot calipers be in the same worst case scenario.

When FJMonkey gets back stateside, I might be able to talk him into letting me do the same test to his blue dots...then we might get a handle on a possible difference in stiffness between the two.

Any perceived "naked eye" flex would have to be the rotor flexing...at least part of it anyway.  I'd be hard pressed to believe anyone could feel less than .005" of measured caliper movement by hand.  In this test anyway, I'm discarding the disc flex variable as I'm mounting the dial indicator to the disc itself.  The measurement remaining after the pads contact the rotor is the just the flex of the caliper.  

Cap'n Ron. . .

[Capn Ron]

Ron,
You had the same thought that I did, as far as checking flex of the calipers.  I guess I can do a flex check of a blue dot caliper. Honestly, I don't think .010 flex is much at all.

Yeah, I'm with you on this one.  The other factor is that even with that tiny amount of flex at the near breaking point of the lever (or so it felt), the lever still had another inch before it hit the grip.  It's as if the caliper will flex a tiny amount and then stop flexing...even as more force is applied.  That would seem like the .010" of flex may add a tiny bit of "sponginess" to the system, but shouldn't limit it's ability to clamp the pads to the rotor.

Cap'n Ron. . .

[Capn Ron]

I am of the opinion this is a HUGE amount of flex. Even if you're getting 1/2 of the total, 0.005", that's' probably 2-3x the pad movement.  Consider how much clearance is there typically between a brake pad & rotor?  My guess is ... 0.001"  to 0.002" maximum.  We've all had to pump up the brakes after pad replacement, then the new pads will squeal because they're riding the rotor.  How about (extreme example, granted) the MotoGP guys that will blow a corner and run off the track after a headshake incident causes the pads to retract?  

I also disagree that this an extreme amount of pressure. Now, I haven't seen Ron in several years, but as I remember he did have little girly-man hands, so his claim of " squeeze as hard as he can" is a bit dubious!  (Ron, just kidding!)  I typically ride 2 up and use a lot of front brake and 0 rear brake.  Maybe that's why I noticed such a huge improvement.
Now, I'd measure the clearance between the pads & rotors, but my FJ is still doing the snowbird thing in Modesto, so I have no real point of reference.
(this is me doing my "no bike, I'm bored" shit-stirring   )

Ron. are you still free?  

I'm with Noel at this point...I'm stepping out of this discussion until I can possibly measure a blue dot setup...until then, there's just a lot of supposition.  "No decision is difficult once you have all the facts."  I hope my input has helped some.

Cap'n Ron. . .

[FJscott]

SimiEd PM'd me with a good suggestion to test the flex of the calipers.  This did interrupt my busy schedule of sitting, but off I went to measure the flex.   

I wasn't sure what to expect or what I was hoping to find other than some accurate number.

The setup:



I attached the dial indicator base to the rotor just below the caliper.  I then aligned the dial indicator tip to the piece of flashing just below and between the two pots.  This was as far away from the clamping bolts as possible to try to realize the most movement.

I then zeroed out the dial to make readings easier:



I then squeezed (squoze?) the front brake lever as hard as I could and noted the deflection of the dial:



Good lord, I thought I was going to snap the brake lever and I was reading .005" of flex.  That's "five thousandths" of an inch.  I repeated this several times and adjusted the markers on the dial face.  I couldn't get the needle to swing any farther than what you see above.  If I'm being honest, the needle start point was a smidgeon off the "zero" and it never quite touched the fifth line making the delta more like .0045".

To put things in perspective, that's less than the thickness of this piece of paper:



To be fair, I would just have to assume the other side of the caliper flexes the same amount for a total of ten-thousandths of an inch.  I don't have a blue dot setup around to measure the flex of those and compare, but ten-thousandths seems like a scant amount of flex in the OEM setup.  Or am I way off here and that's a HUGE amount of flex for a caliper?   

Cap'n Ron. . .

If you want to determine caliper flex should you not place the dial base on the floating rotor? I would think to get a true measurement of caliper flex the base should be fixed to something independent of the floating rotor...like the fork maybe?
I understand the mag base wont work on the lower fork but if you hose clamp the base around the fork and close to the caliper bracket as possible id bet you would get a much different and better representation of caliper flex.

lets get some more sticks on this horse, hes still movin!

I like my Blue Dots...they look cool

Scott

[Country Joe]

That's great information Ron 69.16lbs is a lot.  I wasn't much help in weighing things. I have a front wheel with a tire on it but no rotor and the wheel on the bike is a 87/88 FZR.

So the biggest gain in reducing the wieght would probably be evalution of a another front wheel and rotors.  Somewhere I seen the FZR wheel weight. I will do some digging.   Good facts for the camp fire Ron.
George

George,
I just weighed my FZR 1000 wheel without rotors but with bearings and center bearing spacer. I came up with 11.4 lbs.

Joe

[hein]

 Threads that go on for too long tend to go in strange tangents and this one is no different. From improving a 87 brake system we've gone to weighing fork components, which is at least usefull, to testing caliper deflection using a flawed and thus useless method.

  Look for the elephant in the room. Its called the FJ fork assembly, complete with wheel and calipers. Its a long 41mm. damper rod fork cursed with a pencil dick 15 mm. axle and today would be considered suitable for a small displacement budget oriented entry level bike. If .005 deviation worries you do a dynamic deviation test on these forks, you won't need a dial indicator, a tape measure would be more suitable. The amount of movement in these forks will scare the crap out of you.

  If you still want to test both styles of calipers for flex or swelling remove them from the forks and test them on their own.

Hein.

[jscgdunn]

Is this the digital campfire way of saying "How about them Packers...?

[Capn Ron]

You're right Hein...Sorry I bothered...

[simi_ed]

yup!

[hein]

To Ed and Ron

  If I offended you I apologize, that was not my intent, neither did I say that a comparitive deflection test of the two different calipers was a waste of time. My intent was to show that a flexible reference point from which to measure was flawed. If I havn't bored the crap out of you please reread the last part of my post. Remove the caliper from the fork and test them on their own.

Hein.

[Capn Ron]

To Ed and Ron

  If I offended you I apologize, that was not my intent, neither did I say that a comparitive deflection test of the two different calipers was a waste of time. My intent was to show that a flexible reference point from which to measure was flawed. If I havn't bored the crap out of you please reread the last part of my post. Remove the caliper from the fork and test them on their own.

Hein.

Hein...Thanks for that.  I definitely don't have the answers and really enjoy the process of figuring things out.  Sometimes that leads to a circuitous path in a thread.  Probably should have opened up a new thread for unsprung weight.  I am gaining a better understanding on the brake system...an area I've never had a need to dig into.

After re-reading Noel's and Scott's replies about a flexing rotor, I pondered this in the garage for a bit last night.  I tried to mount the dial indicator to read the inside half of the caliper, but it's just too crowded.  I took a break from it and watched some show on the tube and then wondered if just pulling the two caliper bolts from the fork (as you're suggesting) would do the trick.  Makes sense to me to isolate things.  I may have been re-inspired.   

Cap'n Ron. . .

[hein]

Ron

Now that we've got our differences worked out maybe I can point out a way of testing the calipers. Removing just the caliper bolts will not help because now you have another moving reference point. One way would be to bolt the caliper to a chunk of aluminum mounted on a stable surface, milling machine bed comes to mind, then slip either a disc or a piece of steel the same thickness between the pads, hook up a m/c to this and using two dial indicators apply pressure and scan both sides of the caliper to check for deviation. This would get a bit complicated and time consuming. Another easier way might be to remove the rotor bolts so that the engagement part of the rotor would not have any tension from the wheel hub. Hooking up one or two dial indicators in this configuration will be a bitch.

The problem with you first method was that you assumed the caliper was at fault. Its like measuring for crankshaft runout and finding it exessive that you assume the crank is at fault. It could be a bearing or bearing bore thats bad. I've spent a good part of my working life diagnosing and measuring stuff and still end up walking down the wrong street.

Hein.

[Pat Conlon]

Spindly 41mm fork tubes and a pencil dick 15mm axle.....I just spit coffee on my keyboard...I hate that...