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

[Capn Ron]

A radial master cylinder has the piston oriented in line with direction of the pull of the lever.
conventional (axial) master cylinders have the piston at right angle in direction of the pull of the lever.

Here's a good discussion: http://www.ducati.ms/forums/80-hall-wisdom/27159-conventional-axial-vs-radial-master-cylinders.html

Cheers

Thank you for posting that link Pat...It's exactly the tech information I was looking for in regards to why all the chatter about a 14mm M/C during the blue dot swap.  I'm supposing it's a closer hydraulic match for the original blue dot setup?

As to Noel's point...What is the technical difference between the blue dot calipers and the late model factory calipers?  Piston size, piston distribution, flex of the housing, and to some degree, weight?

I'm down with a cold at the moment and have SimiEd's old factory calipers ('89) in the garage.  I'll go measure up the pistons (has this been done already?) and if someone with a set of blue or gold dots laying around could do the same, it'd help put this topic in perspective.

Cap'n Ron. . .

[Pat Conlon]

Ron, the best explanation on why the 14mm vs oem 16mm (5/8") m/c works better with the R1 blue spots was explained to me as follows:
The 28% smaller area of the 14mm piston means that the stroke has to be accordingly longer to move the same volume of fluid to exert the same pressure on the caliper pistons.
It's this longer stroke that gives better modulation (feel) to the brakes.

Both m/c's have the ability to lock the front wheel so overall force (pressure) is not the issue, it's all about the control, or feel of the lever prior to, or just below, the threshold.

Does that help?

I'm sure something is technically wrong with the above explanation, but fear not, Noel will chime in shortly.  

[Capn Ron]

Ron, the best explanation on why the 14mm vs oem 16mm (5/8") m/c works better with the R1 blue spots was explained to me as follows:
The 28% smaller area of the 14mm piston means that the stroke has to be accordingly longer to move the same volume of fluid to exert the same pressure on the caliper pistons.
It's this longer stroke that gives better modulation (feel) to the brakes.

Both m/c's have the ability to lock the front wheel so overall force (pressure) is not the issue, it's all about the control, or feel of the lever prior to, or just below, the threshold.

Does that help?

I'm sure something is technically wrong with the above explanation, but fear not, Noel will chime in shortly.  

Oh, yeah, I get that.  On my earliest post in this thread, I mentioned the hydraulic issue mostly because a lot of folks change to the 14mm M/C along with the blue dot change.  I wasn't aware of the factory size M/C being 16mm and in which direction (more or less modulation) this would take you.  All this good information is trickling in in bits and pieces and I will be adding the factory caliper measurements in my next post.

So...would the modulation (lever feel) change from factory if one were to *just* change the calipers to blue dots?  Or is that exactly the problem...that the OEM 16mm M/C pushes too much fluid for the blue dots making the lever too "hard"?

Cap'n Ron. . .

[Pat Conlon]

I can't answer that based on my experience.

I never tried the 14mm m/c with either the '84 or '92 oem calipers.

[Capn Ron]

Just funneling in some more data...Not sure if this has been posted somewhere over the years, but I have a spare set of '92 front calipers in the stockpile so I did some measuring:

There are four moving pistons in each front caliper and they are 32mm in diameter each giving 1608mm^2 of piston area:



They are placed 10mm apart from each other:



Giving a total pad contact (including the 10mm gap) of 74mm long x 32mm high:



A single front caliper (minus the bleed screw) comes in at 1124 grams:



So far, all I can find on the blue dots shows the weight to be 720 grams??    Sheesh, that's getting near a pound of unsprung weight savings per caliper!  The gold dots with the aluminum pistons are listed at 650 grams each...well over a pound savings each over OEM.  Not bad at all!

They also appear to use different size pistons within the same caliper.  27mm and 30mm...both smaller than our OEM pistons and having 1279mm^2 of total piston area.  This would certainly explain why folks would want to change to a 14mm master cylinder...the OEM 16mm M/C would give too hard a lever feel with just a caliper change.

There is talk of some heat advantage of having the trailing piston be larger than the leading piston...short of that, the blue dots have just over 20% *less* piston area contacting each brake pad than the factory caliper.  Given that, WHY are they providing better braking?  Is it the different sized pistons approach?  Eh...maybe.  Lighter weight?  Nice, but no braking advantage there.  Less flex?  I'd buy that as it would allow more clamping force, but are they actually stiffer?  ...and does that over-compensate for the smaller piston contact area?  Is it just that we're changing 20+ year old setups that haven't been serviced in years with a complete brake system makeover (SS lines, fresh master cylinder, serviced calipers, fresh fluid, high-end pads (EBC HH) and a proper bleeding)??  

Still looking for the smoking gun and obviously have too much time on my hands.  

Oh...and don't anyone tell my girlfriend that I used her food scale to weigh greasy motorcycle parts...Thank you! 

Cap'n Ron. . .

[movenon]

"So far, all I can find on the blue dots shows the weight to be 720 grams??  shok  Sheesh, that's getting near a pound of unsprung weight savings per caliper!  The gold dots with the aluminum pistons are listed at 650 grams each...well over a pound savings each over OEM.  Not bad at all!"

On the weight issue, I also found that the Race Tech springs also take some weight out of the system.  My FJ calipers weighed in at 1.065 kg each with pads. Not a big thing but it all adds up.  I imagine aftermarket rotors are also lighter.

Talk to Mark, I think he is, or was running a stock 5/8 MC with the blue dots.  

Good information Ron.  Keep up the flow 

George

[FJmonkey]

Talk to Mark, I think he is, or was running a stock 5/8 MC with the blue dots.  

George, if you mean me as the Mark you refer to then yes, I have Blue dots, SST lines, HH pads, Arashi wave rotors and OEM master. I have not commented as I have no good reference that I think would help in the discussion. When I changed over it was a night and day difference, but considering that I changed nearly the entire front end at once. In addition to the above I also put on 89' fork lowers, new fork bushings and seals, RPM vales, straight rate springs, RPM fork brace. So it is no wonder it felt totally different, it was. My brake feel at the lever is stiffer, I feel like it needs less travel to apply the same amount of braking force. Is it from the SST lines? The HH pads, rotors? I have to imagine all the above contribute to the new stiffer feel. I like the stiffer feel and hesitate to try a 14mm master because I am used to the new feel of my brakes. I feel that I have good control over modulation of braking force without any over braking, even in corners when I enter a little too hot for comfort. I am not knocking the 14mm as I have no comparison, perhaps I will get bored and pull out the 14mm master and give it try. The problem is, when I get bored I suit and go for a ride. If we had an off season for riding in SoCal these projects would be easier to plan. So I hope this helps in some way.

Now back to your regular programming....

[Capn Ron]

When I changed over it was a night and day difference, but considering that I changed nearly the entire front end at once. So it is no wonder it felt totally different, it was. My brake feel at the lever is stiffer, I feel like it needs less travel to apply the same amount of braking force. Is it from the SST lines? The HH pads, rotors? I have to imagine all the above contribute to the new stiffer feel. I like the stiffer feel and hesitate to try a 14mm master because I am used to the new feel of my brakes. I feel that I have good control over modulation of braking force without any over braking, even in corners when I enter a little too hot for comfort. I am not knocking the 14mm as I have no comparison, perhaps I will get bored and pull out the 14mm master and give it try.  So I hope this helps in some way.

That's great feedback Mark!   On the first point, you noticed a great improvement in handling and braking, but as you say...you changed out a LOT of components!  On the other point, you noticed less brake lever throw with the new calipers and keeping the stock M/C.  That aligns with the new hydraulic scheme.  You have the OEM ~16mm master moving more fluid than the R1 Calipers...with their smaller piston area...need.  That leads to a shorter throw and a "harder" lever feel.  Based on the great info in the link that Pat provided, lever feel/modulation can be altered by M/C choice and is a personal preference.

Mind you, I'm not trying to be talked into...or out of...changing to blue dots over my OEM setup.  I'm perfectly happy with the braking performance of my bike.  That may well be because I've changed to all SS lines, a new OEM M/C, did a proper service on the calipers, fresh pads, fresh fluid and an anal-retentive bleeding job on the front end.  I just like to understand things and if someone comes along with something more solid on the blue dot calipers than "way better than my old setup", I might just look into a pair for an improvement in braking I'm not even imagining at this point.  Until then...for me anyway...the blue dots are a solution for which there is no problem.

Cap'n Ron. . .

[movenon]

Talk to Mark, I think he is, or was running a stock 5/8 MC with the blue dots.  

George, if you mean me as the Mark you refer to then yes, I have Blue dots, SST lines, HH pads, Arashi wave rotors and OEM master. I have not commented as I have no good reference that I think would help in the discussion. When I changed over it was a night and day difference, but considering that I changed nearly the entire front end at once. In addition to the above I also put on 89' fork lowers, new fork bushings and seals, RPM vales, straight rate springs, RPM fork brace. So it is no wonder it felt totally different, it was. My brake feel at the lever is stiffer, I feel like it needs less travel to apply the same amount of braking force. Is it from the SST lines? The HH pads, rotors? I have to imagine all the above contribute to the new stiffer feel. I like the stiffer feel and hesitate to try a 14mm master because I am used to the new feel of my brakes. I feel that I have good control over modulation of braking force without any over braking, even in corners when I enter a little too hot for comfort. I am not knocking the 14mm as I have no comparison, perhaps I will get bored and pull out the 14mm master and give it try. The problem is, when I get bored I suit and go for a ride. If we had an off season for riding in SoCal these projects would be easier to plan. So I hope this helps in some way.

Now back to your regular programming....

Yes I did mean you, and the input is helpful.  I am going to use the stock MC to start with and when I come across a good deal on one of the 14mm GL 1800 MC 's I will go for that.  Wish we could ride year around up here. The colder weather is a show stopper.  And when the weather starts to clear up you have to contend with rain and sand plus a few pot holes........
George

[FJmonkey]

In that case, I am happy to have helped. Just to make one thing clear, the stiffer feel does not mean I need to squeeze harder to stop. I can lock up the front with only two fingers, not something I felt I could do with the 86' OEM setup.

[Capn Ron]

In that case, I am happy to have helped. Just to make one thing clear, the stiffer feel does not mean I need to squeeze harder to stop. I can lock up the front with only two fingers, not something I felt I could do with the 86' OEM setup.

Do you still have your '86 calipers?  I'd love to get a look at those...

Cap'n Ron. . .

[ribbert]

Just funneling in some more data...Not sure if this has been posted somewhere over the years, but I have a spare set of '92 front calipers in the stockpile so I did some measuring........

Cap'n Ron. . .

I suspect not.

[ribbert]

......... but fear not, Noel will chime in shortly.  

I hate to disappoint you Pat, but sometimes it's better just to sit back and watch. A lot of people are enjoying this thread.

Noel

[ribbert]

"So far, all I can find on the blue dots shows the weight to be 720 grams??  shok  Sheesh, that's getting near a pound of unsprung weight savings per caliper!  The gold dots with the aluminum pistons are listed at 650 grams each...well over a pound savings each over OEM.  Not bad at all!"

On the weight issue, I also found that the Race Tech springs also take some weight out of the system.  My FJ calipers weighed in at 1.065 kg each with pads. Not a big thing but it all adds up.  I imagine aftermarket rotors are also lighter.

Talk to Mark, I think he is, or was running a stock 5/8 MC with the blue dots.  

Good information Ron.  Keep up the flow 

George

George or Cap'n Ron, can you find out the total unsprung weight of the front end (someone must have one in bits) Forks, wheel, discs, calipers (applied), tyre (inflated to max pressure) mudguard etc.

Thanks

Noel

[Capn Ron]

George or Cap'n Ron, can you find out the total unsprung weight of the front end (someone must have one in bits) Forks, wheel, discs, calipers (applied), tyre (inflated to max pressure) mudguard etc.

Thanks

Noel

That's a fun question...I have two full sets of OEM wheels hanging around with tires and rotors mounted that would be easy to weigh out, but there would be variations in weight based on tire choice...I would certainly be splitting hairs over the weight of air pressure.  I have already given OEM caliper weights with brake pads (new or worn?)... I have spare front fender halves lying around (pretty insignificant in the grand scheme, I'm sure)...Then there's the unsprung part of the front forks?  How much of the spring do you consider "unsprung"?  How much of a brake line do you weigh figuring one end is attached to an unsprung part and the other end is attached to a sprung part?  What about the speedo cable?  Are you looking to get accurate numbers or just a ballpark estimate?

I'm certainly not going to change calipers for a weight savings alone...but if there IS a yet-to-be-clarified improvement in clamping force to be realized with the blue dots, a weight savings just goes into the "pros" side of the pros/cons list.

I guess I'm saying that I can weigh out some of these things easily...but being completely accurate with unsprung weight will be difficult, so I can't furnish the full, accurate answer.  Still want rough numbers?

Cap'n Ron. . .