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Old 05-01-2018, 01:59 PM   #1  
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Default RHD Brake master cylinder

Does anyone know of a brake master cylinder upgrade that will work for a right hand drive car? The Wilwood 1" listed on many miata vendors sites seems to be non side specific with the downward facing outputs, but I'm not sure as I haven't seen one in person, and I'm unsure of the routing. I reached out to 949 and they weren't sure about the right side fitment. I'd prefer not to go all out and get a pedal box. Alternatively are there measurements I could pull to confirm it would fit? I'd prefer a remote reservoir, but I doubt that's a determining factor. I assume any issue in fitment would be related to length of parts and orientation.
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Old 05-02-2018, 04:55 PM   #2  
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Here is the part number for the USDM brake booster for a 1991

NA23-43-800

Call your dealer and check what their part number is. This will give you a point of reference.

This is the part number for a booster from a 2003 that uses the factory 15/16 master.

N066-43-800A

If your part numbers is the same then you will have reference to talk to 949 about.
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Old 05-02-2018, 05:08 PM   #3  
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I appreciate the response, but my car is right hand drive, so my BMC is on the other side. I know the Wilwood 1" will fit on the USDM 1991, What I don't know and neither did 949, is whether there are differences with the JDM car because it is on the other side. I don't know if the cars are simply mirror images in that respect, if they are, then the 1" Wilwood will fit, but if there are length or shape or mounting differences because it's on the other side, then it might not fit.
I'm mostly asking to see if anybody has already done this or knows enough about it to be sure of the answer. I'm capable of ordering the part and pulling the old one and trying to install it, but I'd rather not disassemble my entire brake system without being relatively sure it will work. I'm hoping somebody from a RHD country will have already tried this or something similar.
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Old 05-05-2018, 04:55 PM   #4  
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That is why I said check to see what your part numbers are not order our part numbers. I bet they are the same part number. Just because it is on a different side does not mean that mazda did not use the same part. So go check the numbers.
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Old 05-05-2018, 08:28 PM   #5  
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I can't tell if I don't understand or you don't. I'm in the U.S. so calling up the dealer will result in the same part number you'd get by calling up the dealer, which is NA01-43-400D. The only way I've been able to find odd part numbers for miatas is here: https://www.miata.net/garage/90-99Parts/index.html unless they're super common main parts in which case google works faster. This doesn't solve the problem because it all refers the USDM LHD cars, and I'm not sure if they're interchangeable. As far as I'm aware, and correct me if I'm wrong, the part number isn't just slapped on the side of the BMC for me to go read off and compare. I've checked and haven't seen it located anywhere. So checking my part number isn't a solution currently unless you know of a parts index specifically for the JDM versions. I've reached out to several people in other countries who appear to have done the upgrade, but none have gotten back to me about which part they used and where they got it.
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Old 05-06-2018, 06:38 AM   #6  
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949 were happy to sell me one for my NB, which last time I looked had the steering wheel on the right side (see what I did there?). There is the one off a 929 that people get too.

FFS, its not rocket science. If it doesn't fit, you get new lines made up, or adapters, or ... whatever you need. There are threads on here that I read before I ordered mine, so the information is not just 'out there', its 'in here'!

If you must use the easy button, just go to a UK, Japanese or even an Australian outlet and order it there. You don't need a part number (though it helps if you have it), just specify its for a RHD fitment.

I'd be careful about ordering from Australia though, sometimes you have to turn the parts upside down to get them to fit.
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Old 05-06-2018, 12:45 PM   #7  
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Australians are ******* great. Thank you.
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Old 05-06-2018, 01:30 PM   #8  
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I'm interested in this too Zajicek. I've got a leaky master cylinder on a Eunos in the states. MX5 Parts in the UK has a new cylinder for $320, but that's pretty expensive. If the Wilwood works I might just go with that too.
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Old 05-06-2018, 01:39 PM   #9  
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Looks like it will, I'll update with success or failure. I'm thinking of doing a brake booster delete as well. The wilwood master seems longer than the stock one, so there might be fitment issues with the booster, no idea. Would need to do a BBK as well to keep everything leveled out with the delete. Also going to run the wilwood instead of the usual for the booster deletes since it's a dual instead of the single for redundancy and safety. I'm seeing the wilwood master at like 130, and the delete at 150, so ad some really nice fluid and it's still cheaper than a replacement master.
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Old 05-06-2018, 11:45 PM   #10  
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Quote:
Originally Posted by Zajicek View Post
Looks like it will, I'll update with success or failure. I'm thinking of doing a brake booster delete as well. The wilwood master seems longer than the stock one, so there might be fitment issues with the booster, no idea. Would need to do a BBK as well to keep everything leveled out with the delete. Also going to run the wilwood instead of the usual for the booster deletes since it's a dual instead of the single for redundancy and safety. I'm seeing the wilwood master at like 130, and the delete at 150, so ad some really nice fluid and it's still cheaper than a replacement master.
Don't go to a 1" master, no booster and a BBK. It will suck.
You need a 0.625" master, no booster, BBK and proper race pads that have low compressibility. Otherwise your pedal will be soggy and not do much stopping. If its a street car, then don't delete the booster.

Read my thread on booster delete / dual masters... it's even for a RHD.
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Old 05-07-2018, 06:40 AM   #11  
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I also have a RHD car here in the states and I'm pretty sure that there isn't any clearance issue with the Brake Master Cylinder. What I do know is that there is a clearance issue with the US clutch master cylinder due to the intake manifold being close to it. When my clutch master went out on me one day I was in a bind and bought a US clutch master cylinder and swapped the guts out. The US clutch master had the outlet port facing at a 45 angle where the JDM is at a 90

In terms of the BMC I don't see why a US one wouldn't fit and if by chance the ports are different in terms of angle or direction, you could buy some brake line stock and some fittings to make extensions to the factory hardline. That to me would be a better option than trying to bend your JDM/EDM lines because if you mess those up it would probably be worse than having to redo custom short hard lines.
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Old 05-07-2018, 05:28 PM   #12  
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Madjak, read through your thread and I've got a few questions,
So from what I've been reading, upgrading to a BBK with everything else stock makes the pedal have a dead area before it bites. Upgrading the master cylinder eliminates this according to what I've read. is it the delete of the booster that makes it soggy again? I figured the booster delete would make the brakes harder to depress but more linear and firmer.
From what I understand the difference in booster size comes down to force vs area. the smaller area, the higher pressure you can get, and therefore the better braking with the same amount of force. But with the bigger brakes you'll need more force, so the smaller master cylinder seems better, but line pressures would get much higher? So you increase the size of the master cylinder to keep a reasonable line pressure at the cost of some pedal effort. It seems most people are just relocating the master to achieve a better pedal ratio to overcome this issue. Is the smaller master size you recommend dependent on the dual master setup and distribution block you used? Is there a benefit/drawback to using dual single reservoir masters as opposed to a single dual reservoir master like the wilwood 1" most vendors stock? The welding and distribution block machining you did is out of my abilities, are there alternatives? Is not deleting the booster for a street car just because of pedal effort, or are there other consideration besides it being a pain in the ***?

Unrelated, but can you DM me about the 3d printed wing you did? I've got a printer and was considering doing the same, curious to see how it worked out.

L337, sweet, good to know, thank you. I just try to make anything I have to replace an upgrade instead of a replacement, so I figured I'd try to work out some sort of upgrade for it instead of just replacing it with a stock cylinder.
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Old 05-08-2018, 01:43 AM   #13  
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Here are some rules: based on a set pedal pressure

1. increasing master diameter you decrease line pressure but reduce pedal travel.
2. increase caliper piston diameter you increase pad clamping force but increase pedal travel.
3. increase rotor diameter you increase braking leverage with no change on pedal.
4. increase pad sizing has zero net effect, however gives longer life and better modulation.

you ideally want less pedal travel as too much pedal movement makes the brakes 'spongy'. You can reduce this effect with pads that are less compressible.

BBK do 3 and 4. Most of the calipers are sized to match the larger miata calipers so there is fairly little change to brake pressure, bias and pedal travel. You do get better leverage due to the larger rotor diameter so you need less pedal for tge same stopping power. The larger pads make ot easier to modulate and the rotors and pads have bigger thermal volumes and don't get as hot.

Removing the booster reduces the brake assist. The amount of assistance depends on the model miata. On cars with big cams the vacuum isnt sufficent to make the booster work linearly so you can get fluctuations in the amount of assist depending on throttle poistion. When removing the booster you normally decrease the master sizing to get more leverage, which has the side effect of increasing pedal travel. You can also change the pedal pivot ratio which basically has the same effect.

The best setup for racing: largest diameter rotors, largest pad area, smallest pedal travel, adjustable bias, linear pedal (no booster), least pedal force.

Some of those combined are impossible so you have to compromise and find the best for the driver.
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Old 05-08-2018, 02:42 AM   #14  
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So if I'm understanding these relationships right, removing the booster, keeping the master the same size (but replacing it because that was the whole point) and running the BBK will net me an increase in braking effort but an increase in braking leverage, which should net out because for a given force on the brakes I'll have more force slowing the car, so it should stay more or less even compared to the current setup.
And if that's correct I'll need a dual master cylinder the same diameter I currently have, a booster delete, and a BBK to achieve my goal, with some lines to attach the master to the distribution block I have stock. And I should attach the delete in the current location to keep the same setup, or slightly higher for a braking leverage increase to reduce the effects of the booster delete.
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Old 05-08-2018, 03:00 AM   #15  
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Removing the brake booster is around a 5:1 loss in pedal leverage. So if you use to apply 10lbs of force to slow the car, without a booster it will be 50lbs... it's a massive disadvantage. Dropping the master a few ratios will only have a 15 - 50% effect. When you drop the booster, you really need to also drop the master diameter, or increase the pedal ratio as well as running a BBK and then you still need to push the pedal 3-4 times harder. Also the pedal will now move a lot more so you also need to get higher performance pads with less compression and run braided lines to stop you getting a smushy pedal. That is why you don't do it on a street car.

On my car I hardly notice it now, but then I'm strapped into a noisy vibrating race car in a tight race seat with no power steering, braking at 1.5G's so I don't really notice the extra leg force. When you first get in the car you'll definitely notice there is no booster. You'll hit that pedal and nothing will happen and you'll have to push harder, then harder and harder and you'll finally start to slow the car. There is no initial bite from the booster kicking in. It's definitely not a mod to do just because you don't like the look of the booster... it majorly changes to how you have to apply brakes. Force in equals braking power linearly, instead of the weird curve the booster gives. (ie 50% brakes with 10% force)
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Old 05-08-2018, 03:09 AM   #16  
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Oh also, the stock master is a tandem master which has two pistons internally so they are 2 x the area of the piston for calculation purposes. It's equivalent to running two separate masters of the same size. (eg 50/50 spilt)
I'm running a 0.625" front and a 0.7" rear which increases brake line pressure 30% or so over stock. It also shifts the bias slightly frontwards. I'm running a 11.75" BBK front and 11.44" rear giving me another 30% advantage. So I maybe have 50-60% combined advantage minus the 500% from dropping the booster. So I probably have to apply 2-3 times the pedal force to stop over the same car with stock brakes. (not that my booster worked very well in the first place)
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Old 05-09-2018, 11:12 AM   #17  
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My RHD 94 came with a wilwood 1" master. I'm not sure who's kit it is, but I can take some pictures of specific bits if you need.
Attached Thumbnails
RHD Brake master cylinder-poomlim.png  
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Old 05-09-2018, 01:04 PM   #18  
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Madjak, I'm not seeing any master cylinders that will work with the booster other than the wilwood 1" or stock. Wilwood's site has a couple tandem duals down to 7/8" (stock) but the mounting seems wrong, and that's with pushrod, which if I'm understanding how it works with the booster, is incompatible, the smallest tandem dual available that would seem to work is the 1". I agree with your assessment of what would be best, and I really appreciate all the information you've provided, but from what I'm getting it seems like the choices are go full custom or don't do anything, any intermediate will just reduce performance.

Tran, awesome, thanks for the picture. What other brake upgrades do you have, how do your brakes feel? What do you do with the car?
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Old 05-09-2018, 09:48 PM   #19  
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Yes brakes are tricky because once you start changing things you really need to go the whole hog and just do it right. You can make small tweaks easy enough to adjust minor issues, like install a wilwood adjustable valve, or run a larger master to reduce pedal travel. BUT once you start removing the booster you really need to tweak everything to help bring that pedal ratio back to get to a good solution. Otherwise you'll end up with in a scenario where the car is uncomfortable to drive and stops worse than stock.

These booster delete kits look good, but it's not something you can just bolt up unfortunately. It would be great to get some feedback from someone who has done it.
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Old 05-10-2018, 02:00 AM   #20  
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I've been talking to omgpham who had a delete kit with a 1", but I think he ended up switching to a tilton box before he even ran the master and delete. I think I might just keep topping the fluid off while I save up for a pedal box, because why not just go full racecar. Only 1400 in parts haha
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