Author Topic: Big-Arse Brakes Mod  (Read 5344 times)

Prophet Of Doom

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Big-Arse Brakes Mod
« on: July 25, 2013, 07:51:59 AM »
In my parts box I have a pair of shiny gold NOS Brembo 4 pot calipers (Ducati ST2, ST4), and a pair of R1 rotors.  The pic with the Tokico calipers are my rotors, but the owner wouldn't sell me the calipers :-(

The rotors just bolt on, so no issues there,  but I need to make adapters for the calipers.  These aren't floating calipers so will need to quite exact, and I'd rather not kill myself first time out.  It will also need to be certified by a government official, so needs to be done competently.

So who here has done this or something similar and wants to share their hints and tips?  There must be heaps of visionaries who would like to sex up their bike a bit.

What sort of material is best to use?
How to calculate perfect drill locations?
How to space correctly?
Safety considerations ?
etc etc



Rikugun

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Re: Big-Arse Brakes Mod
« Reply #1 on: July 25, 2013, 11:48:56 AM »
This is a great topic which should prompt some good discussions and maybe even some debate.  ;) I'll relate my experiences (over several entries) although some of it will only apply to using like components. Depending on the components used, the process may become more involved and possibly require some machining? In my case only a drill press and band saw was used although the band saw was a luxury that may be replaced with more manual cutting processes. I suppose even the drilling could be done by hand held drills but I felt more comfortable with the relative precision of a press.

In my parts box I have a pair of shiny gold NOS Brembo 4 pot calipers (Ducati ST2, ST4), and a pair of R1 rotors.  The rotors just bolt on, so no issues there,  but I need to make adapters for the calipers.  These aren't floating calipers so will need to quite exact I though so too but now think there may be some wiggle room which I'm sure we'll cover later...,  It will also need to be certified by a government official, so needs to be done competently.  hmmm, how picky are they!?  :o  :D

What sort of material is best to use? steel is heavy but stronger than aluminum and not as sexy. If you can afford even more exotic materials good for you!
How to calculate perfect drill locations? definitely was one of my concerns too
How to space correctly? yup, another good one. Ideally, find the clearance of rotor to caliper carrier on the component's OEM setup. I used components another member used so this work had been done for me.  :)
Safety considerations ? still in the testing stages with just under 200 miles on the setup so I'll keep you posted but so far so good.  :)
It is far better to grasp the universe as it really is then to persist in delusion, however satisfying or reassuring.  Carl Sagan

treedragon

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Re: Big-Arse Brakes Mod
« Reply #2 on: July 25, 2013, 04:33:10 PM »
Government official???  I just put mine on and it was accepted as normal at the next WOF  ;D
.... and of course it was nothing to do with the fact we do WOF checks anyway. These days your regular WOF station hasn't a clue what it should be like anyway.

Best tip I can give is to connect your calipers to master cylinder etc, place them on the rotors on wheel and clamp brake on. This will hold them in their natural position relative to everything else and make measuring a lot easier.

I used thick aluminium plate (because it was there) and milled out the inner side to suit the various mount points.

 
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Rikugun

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Re: Big-Arse Brakes Mod
« Reply #3 on: July 25, 2013, 07:35:37 PM »
I've noticed the 4 pot caliper adapter plates are mounted to the front of the fork leg caliper mounting bosses and the caliper attaches behind the adapter. Treedragon's FZR units, HarryTakeuchi's Brembos and the pic roro posted of TL1000 Tokico calipers are all like this. What I can't see from the picture angle is if the adapter plate is stepped or relieved in the back where the caliper attaches to facilitate the correct "offset" or rotor clearance? Treedragon, when you say you "milled out the inner side..." is this what you mean?

As far as clamping the caliper to the rotor via hydraulics to measure the offset or plate thickness requirement, aren't you relying on the pistons all starting at the same place and extending equally front and back when extended? Would it be wise to visually check that nothing interferes with the rotor and the wheel "spokes" when the caliper is hydraulically clamped to the rotor prior to committing to the adapter plate measurements?

What I mean is, imagine the caliper mounted on an adapter plate and it just so happens the pistons are all extended equally. Actually I guess this would be the goal provide it coincided with all clearance requirements. Anywho, now imagine you modified the plate by removing some material just where the caliper mounts and reinstalled the caliper effectively changing the caliper's offset relative to the rotor. Pumping the brake lever advances the caliper pistons but now on one side of the rotor they are extended further than the pistons on the other side. Lets assume there is still proper rotor clearance but that's not necessary for this exercise. In both scenarios the adapter plate has defined where the pistons end up - not the whims of hydraulics and path of least resistance. My point is, prior to creating the adapter, simply pumping the lever to clamp the caliper to the rotor may not guarantee the pistons extend equally front and back and/or proper clearance has been established. Yes? No?
« Last Edit: July 25, 2013, 07:40:01 PM by Rikugun »
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jefferson

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Re: Big-Arse Brakes Mod
« Reply #4 on: July 25, 2013, 11:13:49 PM »
The pistons don't really have to be equally extended for everything to work ok, but then I don't think that was exactly your question. The main thing is to get the disc in the center of the slot in the caliper and to get the caliper raised off the outer edge of the disc the proper distance. A friend of mine was doing some very intricate mounts for the calipers on a Squalo (beautiful bike) and he used a piece of wire layed on the edge of the disc to get the proper spacing to the caliper. Very easy and it worked perfectly.

Rikugun

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Re: Big-Arse Brakes Mod
« Reply #5 on: July 26, 2013, 08:58:31 AM »
Yes, my point exactly - holding the caliper in position using brake pressure is handy during fitment but simply pumping the brake lever doesn't necessarily guarantee the caliper is centered left to right correctly or is repeatable. The "up and down position" if you will, is yet another factor.  I laid the brake pads on my "new" used rotor (FJR1300 in my case) leaving a margin of rotor showing and otherwise placing them where they looked right. I then took the highly scientific approach of tracing their outline onto the rotor with a Sharpie marker. After reassembling the pads into the Suzuki SV650 caliper I positioned the caliper onto the rotor using the pad outline as a guide.

I wanted to find a way to quickly locate the caliper into position without using the marker outline much like your tip of using a length of wire as a shim. There are pad guide pins at either end of the SV caliper. I found that placing a sleeve from proper sized (wall thickness) tubing over the exposed portion of pin spaced the caliper just right. These sleeves were cut to length then slit along their length to facilitate slipping over the pins. This way, every time I removed/replaced the caliper during fitting it was a simple matter of resting the "padded" caliper pins on the edge of the rotor and the placement was perfect making the marker guides unnecessary from that point on.

Only then did I bolt the rotor to the wheel, install the wheel and introduce the caliper into the system and bleed the air to make it functional. Obviously I had gone through the caliper prior to ensure it was serviceable.  :)

Getting back to caliper position left to right, in my case someone else already did the work. Jasonm used SV calipers (floating 2 pot) on his twin disk setup although with R1 rotors. His adapter plate is 1/4" thick steel bolted behind the leg bosses with the caliper bolted behind it utilizing the caliper's threaded mounting holes. It just so happens this places the caliper correctly so no spacing or milling was needed in my case.
« Last Edit: July 26, 2013, 09:12:14 AM by Rikugun »
It is far better to grasp the universe as it really is then to persist in delusion, however satisfying or reassuring.  Carl Sagan

Prophet Of Doom

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Re: Big-Arse Brakes Mod
« Reply #6 on: July 26, 2013, 11:58:30 PM »
I think I'd like to use alloy rather than steel.  It's easier to work with and for small quantities the cost makes no real difference.   
Treedragon - how thick was your plate?  I have some 6mm 6061, but it looks a bit thin - should I go to 8 or 10mm do you think? and will 6061 be OK ?

Here's a pic of the Brembos tied on with safety wire with the R1 Rotor.  (see pic 1) Pretty happy with the look.  This will enable me to make a rough outline in metal.  I'll make a transfer punch out of the correct sized bolt to mark the hole locations.  I'll use the wire trick for the spacing with some Tig rod I have lying around for the offset from the rotor.

The Brembos have a 7.75mm slot where the 4.75mm rotor goes, and I've found that the wheel is not dead centre - there's a 3mm difference between left and right side from the rotor to the fork leg.  That's wider that the margin of error.  I'll have to pull my wheel off and figure why it's not lining up properly - seems the front axle is poking through too far, but I can't see that there's anything to stop it. (See pic 2)

Once I've sorted the wheel left/right alignment the next question will be the caliper offset - looks to be about 5mm inside of the fork lugs, so I'll need to either build that up with a couple of washers, or mill out the part where it mounts on to the fork and add that to the overall thickness of the plate I use.  I don't have a mill, but may be able to get access to one.  Are washers OK or should I find out about milling?


fret not

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Re: Big-Arse Brakes Mod
« Reply #7 on: July 27, 2013, 12:34:05 AM »
Roro, check the wheel alignment before you start changing wheel spacing and stuff like that.  Some bikes have intentionally offset components for alignment and balance.  Just because it looks odd doesn't mean it is.
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Rikugun

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Re: Big-Arse Brakes Mod
« Reply #8 on: July 27, 2013, 06:46:25 AM »
Roro, since my adapter plate goes behind the fork I was limited to nominal 6mm thickness and steel was a better choice. I'd agree alloy would work for yours and seems to be the common material when space permits. The 4 pot caliper's mounting hole location seems to dictate the plate has to go on the outside of the fork bosses. The first pic is an adapter plate (not for a Vision) being made. The material is aluminum and quite thick and ended up going on the outside of the fork.

With your wheel alignment issue can I suggest loosening (or removing) the fork brace, loosening the axle and pinch bolt, then jouncing the suspension a bit. Snug up the axle and jounce some more then snug up the axle pinch bolt and see where the wheel ends up. Leave the fork brace loose during all this.

Since my caliper position (L/R) had been figured out by someone else  :) and the tubing shims placed it where it needed to be up/down, the only thing left was to create the adapter. Jason had suggested using 1/4" acrylic as a template material as it machines easily and is sufficiently robust for the job. I found another good reason to use it although I used some 1/8" I already had.

I printed a picture of the caliper/rotor mock up (second pic) that I merely eye-balled into what seemed like a good position relative e to rotor and caliper. I printed it out at various sizes until the fork boss center to center distance was actual. Then I laid the clear acrylic on the pic and drew with a "Sharpie" the basic adapter plate shape. After cutting the template out it was a just a matter of transferring the hole locations and drilling them. I used the finished template to bolt everything together. It looked good so I transferred everything to the steel plate and finished the part.
« Last Edit: July 27, 2013, 03:08:25 PM by Rikugun »
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jefferson

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Re: Big-Arse Brakes Mod
« Reply #9 on: July 27, 2013, 11:27:18 AM »
I am having visions of 35mm forks bent backwards!

QBS

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Re: Big-Arse Brakes Mod
« Reply #10 on: July 27, 2013, 05:39:25 PM »
Me too.  However, the small V front tire may not provide enough traction to bend the forks.  That raises the question: Is huge braking power necessary if it can't be be used?  Once the front tire locks up, maximum deceleration has been achieved.  End of story.  Having said that, there is a case to be made for the ability of big brakes to make it easier to modulate ones approach to lock up.  But, that can probably still be achieved with less braking power bolted on.  The benefits of less unsprung weight are also worthy of consideration.  None the less, the enhanced appearance of trick modifications is hard to deny.

Consider that bikes that have this level of braking power from the factory also have more power, bigger front rubber, and stronger forks.  They can therefore use big braking power. 
« Last Edit: July 27, 2013, 10:46:03 PM by QBS »

jefferson

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Re: Big-Arse Brakes Mod
« Reply #11 on: July 27, 2013, 06:16:41 PM »
I like having really good brakes. The one thing that really helped me out with the 83 setup I had on the racebike was getting the rotors cryo treated. There was a chicane on the backstraight at Heartland Park that would get the old pulse accelerated at least once every race weekend. I just didn't know if I was going to get slowed down for the corner. After the cryo I never had another issue of doubt. Psychological maybe, but I will take it. Now the guy here in town that did it is out of business.

Jeff

treedragon

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Re: Big-Arse Brakes Mod
« Reply #12 on: July 27, 2013, 09:20:11 PM »
A slightly different point of view..........

If you need to stop THAT urgently you haven't been paying attention and likely you don't really care at that point as long as you live  ;D ;D
I KNOW this  ::)

Without a decent master cylinder as well, the full potential will not be there anyway judging from the changeover on my bike that is why I found another master cylinder.
Generally speaking when under full braking the front forks are compressed so that means there is very little fork slider length to bend......

Which reminds me of an early Suzuki GSX something or other I met on the HAAST road when parts were still gravel, his forks were nearly vertical after having hit something, his brakes still worked..............   I do believe he was traveling rather slowly as a result though  ;D  ;D  ;D

 I agree with QBS re bigger brakes maybe being easier to modulate however the original brakes were good at this, you just slammed them on hard and they slooowly and predictably slowed you down and in this case the "paying attention" bit meant allowing enough room ahead.......... ahem ::)
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jefferson

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Re: Big-Arse Brakes Mod
« Reply #13 on: July 27, 2013, 10:43:09 PM »
The bent forks thing was a joke.

Jeff

Rikugun

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Re: Big-Arse Brakes Mod
« Reply #14 on: July 28, 2013, 06:58:56 AM »
I assumed you were joking but the takeaway is 2 four pot calipers almost seems like overkill for the smallish V tire's potential. I can say this not from having ridden a V with this setup but rather extrapolating from the significant improvement on mine with only one disk w/2 pot caliper. I can also appreciate the "can't have too much braking available" school of thought though....  :D

To treedragon's comment re the master cylinder, I noticed a diminished initial firmness in the lever after the swap. One reason may be the SV caliper has nearly 25% more piston area than the XZ piston requiring more volume to keep the same initial lever feel?  I'm guessing the area difference between a XZ caliper and a 4 pot caliper may be greater yet. On a related note..... prior to doing the swap I spoke with several people about using a dual disk caliper (larger piston) on my single disk setup. All parties hypothesized there would be less feel/feedback and didn't advise it. Still curious though...  ;)

At 298mm stock RJ rotor vs. 320mm for the R1 and FJR, there is not a dramatic difference. Going from the RK's 267 to 320mm on the other hand, combined with significantly more capable calipers should enable locking the front wheel at any legal speed an easy task.
It is far better to grasp the universe as it really is then to persist in delusion, however satisfying or reassuring.  Carl Sagan

Rick G

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Re: Big-Arse Brakes Mod
« Reply #15 on: July 28, 2013, 08:35:58 PM »
Look up Jasom Morris comments on his modern front brake set up . He listed the whole recipe .
Rick G
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Rikugun

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Re: Big-Arse Brakes Mod
« Reply #16 on: July 29, 2013, 07:26:53 AM »
Mine is modeled after Jason's work but only some of the particulars apply to what Roro is doing.

Getting back to rotor diameters....  If you have a stock twin disk setup and wanted an economy upgrade I'd suggest using '82 Vision rotors and Tokico calipers similar to what I used. Both are plentiful and can be sourced economically yet will yield an impressive gain in stopping power.  :)
« Last Edit: July 29, 2013, 07:41:33 AM by Rikugun »
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QBS

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Re: Big-Arse Brakes Mod
« Reply #17 on: July 29, 2013, 01:27:55 PM »
Could two '82 brake sytems be installed on an '82? 

Prophet Of Doom

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Re: Big-Arse Brakes Mod
« Reply #18 on: July 29, 2013, 04:08:53 PM »
Could two '82 brake sytems be installed on an '82?
The mudguard mounts would be facing the wrong way on the right hand side.

fret not

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Re: Big-Arse Brakes Mod
« Reply #19 on: July 30, 2013, 12:18:39 AM »
For the '83 there is a distinct difference between the right and left calipers (mirror ) which would be needed for the '82, plus a suitable lower fork leg (slider).

I think one strong 4 piston caliper and larger disc would provide the stopping power, and larger diameter fork stanchions would help resist twisting under braking with one disc and caliper.  Treedragon is absolutely correct in that you don't need quite such massive stopping power but a lighter front wheel really helps going over rough surfaces while leaning over.  The more time the tire spends in contact with the road surface the more control you have.

In the early 70s I had a Yamaha TR2 production racer which had a front brake (brake only, not rim and tire) that weighed 32 lbs. (14.5kg), and what a marvelous difference when the front wheel was replaced with one that weighed 25 lbs (11.37 kg) INCLUDING the rim and tire.  Going over choppy pavement bent well over was so much smoother and more controllable with the lighter front wheel. 

The technical aspects of handling come down to the sprung vs the unsprung weight of the vehicle.  The heavier the vehicle the heavier your brakes can be, and the lighter the brakes are compared to the rest of the vehicle the better contact the tires will have with the road.
« Last Edit: July 31, 2013, 01:20:15 AM by fret nut »
Retired, on the downhill slide. . . . . . . . still feels like going uphill!