matching mc to caliper

[Tapartacus]

Hi everyone I know this has been beaten to death but I have a R6 blue spot caliper question. I have installed R6 calipers with braided lines on a stock master cylinder on my 92. brakes work ok but not as magical as everyone says they are supposed to. Some say the 14mm mc that comes with the R6 blue spots is the one to go with, better feel etc.(compared to the very stiff wooden feeling I have right now). Also some say the 19mm nissin radial is the way to go. I guess my confusion comes from the fact that if the blue spots are matched to a 14mm mc for best ratio why would going to the other end of the scale at 19mm work. I understand the stock mc is 15mm. Any explanation would be appreciated. btw also installed news chinese wave rotors.
Andrew

[SlowOldGuy]

You can't directly compare the size of a conventional MC with a radial MC.  Their levers have different mechanical advantage/pivot points. 

Changing to either 14mm conventional or 19mm radial will improve the wooden feel you are currently experiencing.  Are you re-using old pads (that possibly came with the calipers) or using new pads?  When I first converted, the pads that came with my monoblocs were contaminated and putting in new pads helped.

DavidR.

[Tapartacus]

The calipers came off a R1 with 1000 miles on it. Pads looked brand new. I understand there is a pad/rotor bed in period so I'm not expecting too much right now in the way of stopping power, but I guess I expected more out of the blue spots. This is what i bought:
http://www.ebay.com/itm/150817338301?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649#ht_1690wt_1008

[SlowOldGuy]

I have the measurements and calculations somewhere, but I moved recently and can't find shit lately.

Here's what I remember from measuring the caliper piston diameters and calculating the resulting areas.

The monoblock calipers have slightly smaller diameter pistons than the stock FJ 4-piston calipers.  So, if you kept the stock MC then you've actually lost some hydraulic advantage in swapping to the blue dots.  You can "supposedly" make up for some of that loss with better pad composition and stiffer caliper construction.

Compared to the older 2-piston calipers, the loss is even greater.  The single larger diameter piston provides more pressure area than 2 smaller diameter pistons.

You gain back the lost hydraulic advantage when you use the smaller 14mm MC.

So, if you keep the stock 5/8" MC, a straight up comparison between the brakes before and after the swap might not be the night and day difference that you expected.  I know I wasn't all that impressed, but the blue dots were less expensive than rebuilding the stock calipers.  And maybe one day I'll get that FZ1 MC so I can keep the stock screw-in mirrors.

DavidR.

[nurse]

Andrew have just done this exact mod to my 93 3xw I fitted r1 blue dots new pads, kept original rotors and put on braided lines. I fitted a 14mm master cylinder from a 1999 fazer (keeping black block style as opposed to the urine cup - personal preference) loads of them in the uk so plenty of spare mc's about and therefore v reasonable ( I paid £30 IIRC). I Promise u I now pull up quicker than a paedophile outside a toy shop!   I was quite cautious bedding them in and have only given them a proper work out today and they are the dogs bollox, the cats pyjamas or very VERY good in plain English!  The only problem is that they highlight how soft the front forks are which now dive further than Tom Daley (uk entry for Olympics).

[Arnie]

nurse,

You now know what your next purchase for the FJ should be - a set of springs and a set of cartridge emulators (from Randy or RT) if you can swing that extra cost.

Arnie

[Pat Conlon]

 Moditis....That's exactly how it starts...

Bypass the Race Tech emulators and go directly to Randy's valves....

[yamaha fj rider]

Cool this is very helpful I was going to do what Tapartacus did. Thank you saved me time and headaches. Guess I now know why every changes there master cylinder.
Quit overthinking it and just what worked for everyone else!!! Thank's again.

Kurt
 

[nurse]

Well I feel a thread hi-jacking coming on.  The springs I understand but not sure what the rt valves or emulators even do. Can someone explain in laymans terms! Or Is there an 'fj front suspension mods for dummies' section on here!

[Arnie]

There probably is a susp for dummies explaination on here somewhere, but I'll try and explain.

Springs support the bike and when you hit bumps or potholes compress or extend quicker than the supported (sprung) vehicle and rider, so this reduces the hobby horse effect you'd otherwise feel.  This is done best by springs (and preload spacers) that have a spring rate that prevents using up ALL the suspension even when you hit a big bump.
The fork oil (hydraulic fluid) within the fork also moves as the bike has these changes of attitude and there is some device within the fork to control (damp or slow down) this movement of the oil.  This device can be a set of:
1. Fixed holes that the oil must flow through, OR
2. A set of spring leaves that will vary the size of the opening that the oil must flow through, OR
3. The device can be a valve with an "inertial port" (I think I'm describing Randy's fork valve correctly) that will also vary the flow rate of the oil depending on how hard the bump is.

Ideally you want your suspension to allow the bike & rider to maintain a steady stable position insulated from the undulations of the road whether they be foot deep potholes, freeway expansion strips, or logs that have just fallen off a truck lying in the road.  Not only does this make the ride more comfortable, but it maintains consistent steering and keeps you from being thrown off the bike (as if you were on a brahma bull).

HTH,
Arnie

[nurse]

Ok I think I'm getting it.  So what your saying is that various scientific factors mix with magic and fairy dust to deliver a smoother ride. A bit like how turbo chargers work. Exhaust gases spin turbines which change air flow and then fairies make the tyres go round faster!

Being serious, I get the basic principles. Are the race tech emulators and randys valves fundamentally the same in functioning principles? But randys valves I assume are better in some way, shape or form!

Is there a general concensus of what combination gives the best result?

The 'magic' valves as stand alone mod? or combined with updated springs and changing weight of fork oil?

I appreciate that it will be personal preference and what you want to do with it in the end (race, tour or climb rock faces!) but I'm fairly middle of the road and would like a happy medium to be able to give the beans on the twisties when on my own but still take the wife out for a nice lunch along the cost in relative comfort. I'm not a racer nor am I goldwing (sofa on two wheels) type rider

P.s. who is this mysterious randy character and where can he be found?

[fj11.5]

randy, is the magical fj fairy  ,, actually he owns rpm selling fj parts cheaper than your local yammy dealer can or will, and lots of after          market items to keep our fj,s happy, and moditis medicated 

[nurse]

Don't suppose you happen to have a key (or hyperlink) to his medicine cabinet do you??

[fj11.5]

sorry i dont, but take a google dose, and try rpm fj parts,    raduchel performance parts may also work if i spelt it correctly

[Arnie]

http://www.rpmracingca.com is his website.
He's a regular contributor on this list and a joy to work/buy with/from. (my opinion :-)
If you go to the "vendor" category on this list, you'll find him.

Re: your questions about R-T emulators and Randy's magic valves,
I have R-T emulators and .95kg/mm springs and am happy with them. 
Those who have tried Randy's magic valve units claim they are even better than the R-T units and I have no reason to not believe them.

If you decide to go with either of these devices, you should do the damper device, appropriate springs, and appropriate fork oil as a set.

Arnie