OEM calliper upgrade ?

Technical Area Wheels, Tyres & Brakes
2

Hi all,

Back in my yoof I used to hoon about in Capri’s. The first thing I would “fix” was the bloody awful brakes.

What I used to do was modify the hubs to take RS turbo disc’s mounted on the outer face, Then fit late Granada callipers on adaptor plates. Voilà ! Brilliant stopping power for very little cash plus pads available anywhere !

So what I’m asking is has anyone ever tried this sort of parts bin approach with the MX5 ?

I’m getting bored of adjusting/freeing the rear callipers and greasing the pins up front to still only end up with “Acceptable” brakes. Once I did the mod, All ton and a half of Capri used to stop quicker than my '5 does on a good day ! There may be something wrong with my standard brakes (Though all my friends who’ve drove it say there fine) or I might just be too used to the bin lid sized setup the works VW transporter uses, But I don’t think anyones ever got out of a car and said “Good, But I wish the brakes didn’t work quite so well”, And there are times when acceptable brakes don’t quite cut it.

If possible I want to use standard callipers and disc’s because I’d rather modify hubs to fit OEM disc’s than have to adapt new ones every time I need 'um, I also want to avoid anything that says Wilwood or Brembo on them due to the cost.

Due to the good old MOT the rears need to have a cable hand brake too.

And finally, The set of parts must be CHEAP (I’m thinking 2/300 quid for parts off Ebay)

So, Any suggestions ?

(Please feel free to call me a prat if this idea isn’t workable on a 5 :slight_smile: )

3

Scole Engineering (Diss I think) had a front caliper kit for the 1.6 at one time; a custom caliper bracket to allow larger VW discs to be fitted (Corrado I think). Plus, I think one of the MX5 specialists was playing about with Princess calipers at one time.  MX5 1.8 brake discs are a bit bigger; get 1.8 caliper brackets (off a Mk1 or 2),and you can fit 1.8 discs and pads, while retaining the 1.6 calipers.

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Erm ?!?! [:)]

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5

You could upgrade to the Mk2.5 Sport brakes, Bigger discs (11" front and 10.9" rears), bigger calipers and bigger pads.
A fairly simple swap and most parts (brackets and calipers) should be available from a breaker.
The only thing to bear in mind is that you will need at least a 15" (ideally 16") wheel to allow for clearance of the new setup. 

6

Jonnie Boy :- This idea did cross my mind, But it dawned on me that there aren’t any 5’s in scrap yards around me. When cars with the bigger setup come up for breaking on Ebay the owners tend to know they have something desirable and price accordingly. [:(]

As I don’t know if the administrators would violently violate me with a root vegetable if I added a link to another site here I think subtlety is the best option… I noticed on a forum for people that “Drift” to there “works” (OK, I think I got away with that. [:D]) Someone used twin pot calipers off the back of an undisclosed Volvo.

They go by the name “cptsideways”, Anyone know them or if the result was worth the work?

7

 

No you didn’t [^o)]

8

NOOOOOOOO! FOR THE LOVE OF GOD !!!

Please, Put the carrot down, I didn’t mean it !

NOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO !!!

(the horror… the horror…the horror [:|])

9

 
There are various specialist MX5 breakers about.

So, you’ve answered your own question… Ask him. He was on the old MX5OC forum, hasn’t surfaced here yet. I’m sure he can be found elsewhere, such as Driftworks. Then there are Princess calipers; a pair of brand 4-pot items can be had for under £200.
“Volvo conversion” applies only to the rear brakes, so that leaves you still trying for front brakes to match. The Scole Engineering kit will equally work well on a 1.8 as a 1.6. Replicating either would need engineering skills, so why not the Princess conversion? It has been done.
This thread will suit you:

They start off discussing effectively the Scole approach.
 You can ge used Wilwoods etc from time to time here:
http://www.rallyusedparts.co.uk/showpartsbydate2.cfm?StartRow=1
 
 

10

 
CptSideways (Declan Hicks) used to be a member on the old forum - I know the car you refer to.
It was bought by fellow Eastern Region OC member Dave Larkman aka Captain Muppet. He’s often on the Forum so it might be worth dropping him a line.

There’s a bit of info on the car HERE

l 

11

Hello! I did indeed have volvo twin pots on the rear of my MX5 when I bought it, but they had the bosses cut off and rewelded, which is not ideal for cast iron bits which might kill you if they fail, also one of the pistons seized solid forcing my to bin them (passed on to JamieK of the old MX5 Forum, and Driftworks, who will, I’m sure, laugh at me when he fixes them). I replaced the Volvo calipers with AP racing twin pots and a custon adapter I designed - there are details in my project thread in the link above. This was all on the rear of my MX5 as I needed to have a rediculously awesome handbrake. My rear discs are the vented front 1.8 discs. My front brakes are well-maintained but absolutely stock 1.6 brakes (I have an adjustable brake bias valve, naturally). On the tracks I compete on the start lines are chosen to suit the much more powerful Nissans, so I don’t normally need to shed a lot of speed using conventional braking, plus sometimes using the footbrake results in a serious points penaulty. On the road I have never, ever wanted more braking than I can get with the stock 1.6 brakes even now it’s turboed.

12

Captain Muppet : Well, I suppose welding a calliper’s going to warp it all over the place, You’d be bloody lucky if it DIDN’T end up as a novelty paperweight. :slight_smile:

One thing thats puzzling me, You have a hydraulic only hand brake… Is this road legal/MOTable  (I don’t know if your car’s also used on the road) ? I know some people used to put fake handbrake cables on there rally Escorts and find an understanding test centre, But to keep it simple(er) I’d rather just keep it cable operated.

 

BTW, Your 5’s one hell of a nice toy, Very Lotus 7 with the “If its not totally necessary, It’s dead weight… And its off the car” single mindedness.

Hats off to ya !

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Depends on how hydraulic it is… see the bottom of this post.

14

Welding the caliper didn’t distort it - it’s a 2" thick chunk of cast iron! But welding a famously brittle material is riddled with potential for having it crack and fall off.

The AP handbrake calliper mod isn’t MOT friendly - so I swap to a normal rear calliper if I’m not going to be using it on track. It passes the MOT just fine with the combined mechanical/hydraulic set up. A similar conversion could be carried out on the front to fit bigger twin pots and bigger discs. I used Lotus Elise AP racing ones, but Volvo 240s also had twin pots all round, and some even have 4-pots. The tricky bit is finding bigger discs which suit the offset of your new callipers and still fit under your wheels. I was in the very lucky position of being able to trial fit all my stuff before any of it cost money. I did have to pay £100 for hubcentric wheel spacers so the wheel didn’t hit the calliper.

I have another pair of the AP callipers which I want to fit on the front, but that’ll have to wait until it’s warm outside again :slight_smile: Naturally I’ll post pictures and drawings of any adapters needed when I’ve done it.

Thanks for saying nice things about my car.

15

I just had a thought (and a good prod around with google)…

From what I can make out the FC RX7’s had a cable hand brake going to the rear callipers mounted on the leading edge of the disc’s,The 35mm pistons area is 21.5 % bigger ( Though the RX7’s 4 pot’s up front are a combined 1% smaller? Oddness? * ). The original MX5 has a 22.2mm internal diameter master cylinder so should be able to deal with a little under 0.1cc of extra fluid needed to use these callipers. Now I just want to compare the area of brake pad in contact with the disc.

These callipers use 273mm x 20mm vented disc’s as standard but I think all the RX7’s that used them had a 114.3 PCD so the disc won’t go on a 5’s hub,…  Does anyone know the thickness of the 270mm front 1.8 Sport disc’s?

I had a good look at my wheels the other day and I’ve got a fair amount of clearance between them and my callipers (15" TSW Alpines, A bit heavy but they were cheap), So I reckon I could get up to 280ish mm disc’s on if I can find any, Bigger’s also better because it gives me more choice on position when I make the calliper mounting plates.

 ( * I came up with these figures on the basis that the piston in a sliding single calliper has to move twice as far to clamp with the same force as a twin with the same size pistons. ie, If both pads had a theoretical 0.1mm clearance ether side of the disc, A twin pot just moves each piston 0.1mm to make contact, A sliding calliper’s piston would push the first pad it’s 0.1 then it would push further against the callipers body to pull the second it’s 0.1mm. So It doesn’t matter if you have single or twin pot, If the piston’s are of the same size it will only need the same amount of fluid to get the pads to make contact, This is a bit of an over simplification and doesn’t take into account the friction to move sliding the calliper)

Lastley…

Not wanting to sound pedantic, But long ago I had a 4" thick cast iron cylinder head that warped, This was when I blew the bottom rad hose on the motorway and it got very hot, Very quick… I don’t think it got up to the temperature needed to MELT the cast iron though.

I didn’t bring up the safety aspect of welding a calliper, I just mentioned why I thought it would have ended up seized.

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My point was that a 2" thick bit of cast iron wasn’t going to distort from welding a little tab on it (cylinder heads are long floppy things compared to a brake calliper). Also the reason for mine seizing was that it was the only one of the 4 pistons with no seal on it :slight_smile:

Your assumptions on piston sizing seem fine to me, certainly more forethought than I put in to slapping my new brakes on.

17

Today I had an easy day at work, So I went into every Mazda dealers garage I saw (3 in total) to try and find out if the FC RX7 calipers had any known issues (And to find out if they knew of anyone else having tried this conversion).

Dealer one’s answer was “I’ve only been here 2 years and haven’t seen an FC in that time, Sounds a good idea though”.

Dealer two said “As you want to use the calipers on a car that Mazda never intended them to go on we can’t say if this may affect there reliability”.

Dealer three said “I can’t comment due to your non standard application” about 15 times in the conversation (I think he must have just finished reading a corporate liability guidelines maual)… I said “forget about the application, I just want to know about the calipers”, His constant “I can’t comment” reply didn’t help. I then said, “Alright then… I want to go and buy a FC RX7, Can you tell me if there are any known issues with the brakes that I should look out for” [:D]. He said “We have a vehicle checking service, If you want you can bring a Mazda here for our technicians to inspect before you buy it…!”, This threw me a little as I tried to get my head around why he was being so evasive. So that was the point where I asked for him to price up 4x 270mm disc’s and a car set of calipers (It came to a little under two arms, a leg and possibly a kidney !). I then said “What a coincidences, Due to your total lack of customer service, Thats exactly the amount I’m NOT going to spend here, Bye bye, Oh and merry Christmas [:D]” . To be honest I never intended to get new calipers, But as MX5parts still don’t have the OEM big disc’s in stock I might have got them there.

 I’m wondering if theres a reason for the “No comment” response? Is there a problem they don’t want to acknowledge to the public?

I’m also wondering that as this seems to be a very simple modification with only a single one off part to fabricate, Why isn’t the Internet littered with “How to’s” about it? Can anyone see something I’ve missed?

I keep thinking I should join the RX7oc forum, Just to see if anyone there can see any problems with the idea…

…Its just that I’ve always found long term Wankel owners to be a little… Erm… unusual. They unnerve me, They seem a bit twitchy, Like a soldier just back from a war zone. I’ve come to the conclusion that it could be because both of them are almost expecting something to explode in front of them at any moment…Also, How much of a serious uberpetrolhead do you have to be to accept that at the mileage an MX5 owners doing a cam belt swap “Just to be on the safe side”, Your doing a engine rebuild for the same reason?

No offense intended to all you RX7 owners out there, (Just don’t make any sudden movements around me, OK?) [;)]

18

Why haven’t you tried miataforum.com? Loads of threads about custom RX7 brake setups, none of it any easier than putting on calipers from another make. Go back far enough, and you’ll find Mazda nearly put on RX7 brakes for their 5-lug M2-1006, plus the same parts were used in the MX5 MPS (see the latest issue of STHT).
Japanese page descibing a FC fitment; note the use of grinder on calipers. You buy new FC calipers from Mazda; say goodbye to any warranty…
http://speed.garage-tsr.com/braken.htm
Use Google translate or similar to translate
Stock:

FC converted:

TSR sell custom caliper brackets:
http://speed.garage-tsr.com/shop.htm


The brackets will cost £494 plus shipping and taxes. so maybe £600 ish. On top of this, you will need a suitable set of discs, calipers, pads. Even if you could get scrapyard calipers (£100) in working condition (and will trust them without a rebuild), you might be in for £850-900. And MX5 Sports are a lot easier to find than a handful of rare 20 year old JDM FC RX7s.
What modifications have you made to the present brakes to decide they were inadequate for your car? I’ve always used just decent quality Brembo discs, Axiss Ultimate pads, and found the brakes perfectly adequate for this weight/power of car (unless you;ve spent loads upgrading the engine, in which case, it seems a bit tight not to just buy an off the shelf brake conversion). Many people confuse poorly maintained brakes for a poorly designed braking system.
Plus there are two different FC brake setups; choose the small brake version, and its a complete waste of time. Plus 4-lug RX7s are 4x110 not 4x100.
If you’re after cheap scrapyard upgrades, fit a 929 M/C.

19

Try this guy on eBay. He’s a breakers  in Bristol and specialises in MX5’s

Andy

http://stores.ebay.co.uk/MAZDA-MX5-SPARE-PARTS-CHRIS-MX5_W0QQsspagenameZL2QQtZkm

20


SAZ9961, Its not that my original brakes are inadequate, I’m just annoyed with having to mess about with the rear callipers every couple of months just to keep them “adequate”.

A lot of owners on here just seem to accept that the rears are going to seize every few years and need replacing. Personally I think if I need to replace an item like a calliper this often then theres a design problem. (Que people saying “I’m still on my originals !”, Stage left :) ).

Also, If I’m going to the trouble of adapting something I might as well use an item that’s going to offer more performance AS WELL as more reliability.

The problem with reworking a component to fit a new home is that it has to be semi compatible in the first place, With the MX5’s rear brakes the problem is that they’re leading edge callipers. For some reason most car’s are now using a trailing edge setup, This means that if you mount these on the leading edge of the disc the hand brake cable needs to come into the calliper from behind (Ooh err misses :)), Or you have to mount the cables outer on the actuator lever and fix the cable’s nipple to the calliper body.

After a long tinternet search I found the FC RX7 rears ticked the most boxes by being leading edge mounted, Having only 21.5% more piston area (So I should be able to avoid messing about with the master cylinder), Pads that are cheap unlike Brembo or Wilwood pads and I can fit bigger disc’s, The benefits of this are two fold, (1) More leverage on the hub when trying to stop and (2) More space to get the callipers mounted where I want them rather than where I can get the lugs to clear each other.

The reason I was thinking of upgrading the front to the RX7 callipers as well was originally due to trying to keep the front to rear brake balance, But as I’ve since realised that the combined piston size is 1% smaller than the OEM ones the only reason I might use some of these is if I use 270mm disc’s I would need to make up some mounting plates anyway and I think the RX7 design would be more adaptable… And nothing to do with 4 pot bragging rights [*-)].

The TSR front brackets you found are interesting, But I can't understand why they cut off the original mounts to then bolt on some more? If there's any people out there who can read Japanese I'd be interested if you could check if they mention anything about this on this page Saz9961 found, And if you can't read it then this link should take you to it through goggles translator, (Worth a look just to see if you can guess what its MEANT to say, LOL).
 
Out of the two pictures of the brackets It looks like the top ones are for the big disc's and the bottom ones are for 1.6/1.8 disc's. But why would I pay £600 for something I can fabricate myself?
 
I haven't made any power related changes yet, That'll be a whole different thread (Everyone prepare for another Turbo v Supercharger v nitrous forum boxing match. LOL).  I'm a firm believer in making it stop before making it go,
 
So, To clear up any confusion, Here's the concept in a nut shell.
 
THE IDEA, I want to use MK2 sport front disc's (270mm) on all four hubs. Use front and rear FC RX7 callipers and making spacer brackets to attach them to the original MX5 calliper mounts.
THE REASONING, More reliable rear callipers. Bigger disc's = More leverage so it should be better than a original stock setup even if I use standard RX7 pads. The callipers are from a car thats 20% heaver so they shouldn't have any issues with stopping an MX5, And of coarse, Bragging rights :),
POSSIBLE PROBLEMS, I might need to shave 2mm's off the inside of the sliding callipers pad "hook" as the disc's are 22mm thick (With 20mm as there "worn out" thickness) and the callipers take a 20mm thick disc. The possibility that the reason its not a common upgrade is because its a total pig of a job. The extra unsprung weight causing my car to bounce around like Tigger on "E". Clearance problems that prevent the front disks going on the back. Me being a lazy git and not getting around to this upgrade then having another box of bits in the "to do" pile.
 
So, Can anyone see a huge balls-up about to be made?