Mazda Calipers, Blanks & other Q's

[Guido]

I think I *may* have finally found a suitable upgrade for my obscure Euro shitebox. I just wanted to ask a few questions from some of the brake gurus before getting too excited.

The car in question is a 1970 Fiat 125s. Currently I run slotted standard brembo's, rebuilt calipers with stainless pistons, EBC's, Motul RBF600 new lines etc etc. The car stops surprisingly well. However, it is soon to have nigh on double the power and I am concerned as to their future effectiveness.

After a tip off from a friend it appears that Alfa 75 discs (DBA668) are the right offset (height is 51.5mm, mine is 52mm with the factory spacer)and they are 268mm x 22mm. Are these able to be ordered as blanks?

As a caliper I am looking to run Mazda RX-7 alloy sumitomo's, they seem to be quite light and are the required 22mm thickness. Are there any differences between the FC (series IV and V) and FD (series VI onwards) calipers?

Would this caliper and disc combination fit under a 15" wheel? Are there any glaring problems that can be seen from this proposed set up?

Any help would be appreciated!!

[mondo2000]

I have a pair of FC callipers and a pair of FD callipers. Unfortunately I have not done any testing with either of them yet.

The basic specs of them are the same. All pistons are 32mm (I think?). The mounting bolt spacing is the same.

The casting looks different. To my untrained eye, the FD ones look like they could be stiffer. The FD ones have a more modern "blocky" appearance similar to Brembos etc. while the FCs look like the old volvos callipers I think? (round casting around the pistons and some small fins). I may be able to email you some pictures if you are interested.

As to wether they will fit, your discs are the correct thickness and about the same diameter. FC disks are 276mm and FD are 294 mm. Your biggest problem is going to be calliper-wheel clearance. You'll need approximately 60mm* between the outer surface of the disk and the inner face of the wheel.




* I suggest you measure this yourself.

[Guido]

Thanks for your help. I know vaguely the difference in appearance. Looks like I may end up going for FC ones cause, either way I go, they will be rebuilt so I may as well start off with something a little cheaper.

[hamish]

Guido, are the calipers on the Fiat the same as Alfa ones of that vintage (ATE)?
if so, I've recently discovered that the 4spot calipers off 2002tii BMW & possibly a few other BM's of that age & some suit vented discs, are meant to be a bolt on to 105 Alfas so it might be worth investigating, they are cast iron & on the heavy side unfortunately.

[Guido]

Thanks for the heads up but I am pretty sure they are different, I think Fiat casted their own calipers. Also trying to keep the unsprung mass down as much as possible.

[C-Murder]

How big are your rotars? I have an FC3S RX7 with 15" rims (stock). I think my rotars are 11.5 inches in diameter, but I cant remember. Stock are 10.8inches I think.

[smee]

I am currently running some series IV calipers and Brembo slotted vented discs on my Familia. They squeeze in under the 15 inch rim, but you have to watch out for the lips on the inside of the rims. Some of the rims I wanted to use are not flat all the way to the back of the face and do not fit over the calipers. I am running a machined alloy spacer on the wheels so the inside of the spokes on the rims clear the caliper.

http://www.fordlaser.com/images/usercars/2012.jpg

http://www.fordlaser.com/images/usercars/2016.jpg

These images show Race Brakes pads. I am now running DS3000's.

[mondo2000]

Smee,

How do the DS3000s compare to the RBs in terms of initial bite, pedal feel, stopping power, getting up to temp and resistance to fade? I imagine the Ferodos are better all round (except when cold), the question is how much better?

[smee]

Smee,

How do the DS3000s compare to the RBs in terms of initial bite, pedal feel, stopping power, getting up to temp and resistance to fade? I imagine the Ferodos are better all round (except when cold), the question is how much better?

The DS's are really the Bees Knees.
I had been speaking with Rick Bates about brake pads and he advised that for my style of driving (Intermediate, not quite a front runner yet) that these would be the pad for me. They take a little while to warm up, but in a rally car you have the luxury of getting at least some temperature into them whilst driving to a stage. Wear seems to be good also. I have not had any noticable fade and feel is good. I am still running the booster until I get a little more confident with the car.

The RB's cost me an event class win. Pads went off totally towards the end of the second last stage I did in Bega. They just would not stop the car. I did not tell my navigator (wife) until half way through the last stage. She could tell there was a problem and that I was not being as aggressive and my driving style into corners changed. They were on fire literally at the end of the 3rd last stage.
On speaking with Race Brakes, they advised me that I had outdriven them. Given the fact that when they had advised on their use originally I was a total novice in a 4wd turbo rally car and they thought they would last longer than they did. Obviously I picked up the Brake late an Turn aspects of 4wd quicker than we expected.
In the Batemans Bay NSW State rally round (with DS's) we were running as high as 12th until we broke a gearbox. May have got top 10 with some luck. The brakes were excellent and worked better than expected when called apon. I run the old DS 2500's in the rear, but most of the braking is done by the fronts.

[Guido]

How big are your rotars? I have an FC3S RX7 with 15" rims (stock). I think my rotars are 11.5 inches in diameter, but I cant remember. Stock are 10.8inches I think.
The discs in question are 268mm so 10.8" sounds about right.

Thanks for that smee. The wheels will be the deciding factor, I have two sets of Superlights and getting 15" wheels in my stud pattern is neither cheap nor easy...:(

[mondo2000]

Thanks for that Smee.

I already have some brand new RB pads so I'll see how they go. If they are not up to the task (circuit use) I know what I'll get.

[Spac]

Mondo, can you answer two questions for me, please:

1. Are the mounting bolts spacings definitely the same between S4 and S6 calipers?

2. Are the mounting lugs in the same spot, relative to the centre of the bearings, or are they in the same spot relative to the centre of the outside edge of the disc?

I've got a S4, and want to upgrade the brakes by using the S4 calipers on the rear, and figure that I can use S6 bits on the front to keep the brake bias vaguely right. But nobody wants to let me get up close and personal with some S6 bits...

[dynomatt]

Spac...I've got the setup you are talkign about on the celica...get dressed and come on over.

Everything is apart too :rolleyes: so may help in your measurements.

Matt

[mondo2000]

Spac,

1. Yes

2. Same relative to the outside edge of the disk. If I understood the question correctly.


I don't see how that would keep the brake balance vaguely right. Unless you want to have the same piston area front and rear. Which would be a bit unusual?

[Nafe]

The discs in question are 268mm so 10.8" sounds about right.

Thanks for that smee. The wheels will be the deciding factor, I have two sets of Superlights and getting 15" wheels in my stud pattern is neither cheap nor easy...:(

You could PM Datman - who is bringing in the Panasport rims. But they aren't what you would call cheap (compared to the locally made wheels). I think the price was $425/rim for the 15x7s

I think the local supply of 4x98mm is really drying up now. We have two sets of Performance Austars (think Momo Star copies), but they don't make them anymore. The bummer is that they clear GTV6 calipers with only a little machining of the hub of the rim! Should've bought another spare set :(

One of the guys bought some new 15x7s in 4x98mm which have plenty of caliper clearance. And are allegedly a magnesium alloy rim (I don't believe it myself, it's probably marketing hype). But the rims themselves look crap IMHO. I can find out the brand and style if you're keen.

[Spac]

Mondo - thank you. :) I suspect that it won't do exactly what I want, but anything is possible... You've supplied me with a good starting point.
The car is a dirt rally car, so more rear bias is a good thing. I'm mostly chasing the pad area in the rear (I have been glazing rear pads about half-way through a rally). What I am hoping to acheive, it to upgrade the rear brakes using S4 fronts, and then use S6 fronts on the front as they are a bigger diameter, and will stop the bias being 50:50.

L_RS_RA, coolie. :) See you soon, big boy. :P