Changing to larger brake rotors on Miata

I have a 90 Miata which now has 17" wheels, The stock wheels are 14"
on the 90 models. I would like to give my Miata more stopping power.
Does anyone know or have a link to refer to which would give me the
information needed to change to a larger brake rotor. I would assume
rotors from a RX7 might work, but what mods would be required.

bayman2222 wrote:
> I have a 90 Miata which now has 17" wheels, The stock wheels are 14"
> on the 90 models. I would like to give my Miata more stopping power.
> Does anyone know or have a link to refer to which would give me the
> information needed to change to a larger brake rotor. I would assume
> rotors from a RX7 might work, but what mods would be required.

I did this using the brake parts from my wrecked '96 on my current '91
model. The difference is amazing.

They look and work much better than the original smaller rotors. The
fronts are extremely easy to do, the backs are a lot more difficult, but
not too bad if you are mechanically inclined and have the tools.

Your 1990 is so lightweight that it should never need bigger brakes than
this other than possibly for racing or for looks to further fill out
those 17 inch wheels.
I know that seeing those tiny original 1991 rotors through my 16 inch
wheels was driving me nuts.

http://www.bigllama.com/miata/brake/bigbrake.htm

Pat

bayman2222 wrote:
> I would assume rotors from a RX7 might work, but what mods would be required.

The RX-7 has a 5-lug pattern, so you would need to replace the entire
hub, possibly the entire rear end and halfshafts. The same goes for the
new MX-5.

I don't even know if this is possible without major customizing, but it
would be very expensive in any case, much more than a big brake kit from
Flying Miata or Goodwin Racing.

Pat

If you were going to add some serious horsepower, a modified RX7 rear end
with the 5 lug hubs might be a useful addition.

"pws" > wrote in message
...
> bayman2222 wrote:
> > I would assume rotors from a RX7 might work, but what mods would be
required.
>
> The RX-7 has a 5-lug pattern, so you would need to replace the entire
> hub, possibly the entire rear end and halfshafts. The same goes for the
> new MX-5.
>
> I don't even know if this is possible without major customizing, but it
> would be very expensive in any case, much more than a big brake kit from
> Flying Miata or Goodwin Racing.
>
> Pat
>

Chuck wrote:
> If you were going to add some serious horsepower, a modified RX7 rear end
> with the 5 lug hubs might be a useful addition.


The stock Mazda Miata torsen will handle as much power as I would ever
want to run in the car, it is way underbuilt for 140 hp.
My car has nearly double the horsepower that it did in 1991, and the
2001 torsen handles it with no problems at all.

If you are talking truly serious horsepower, and torque, I would go with
the Thunderbird limited slip rear end setup that they use in the Monster
Miata kits.
That is going to be stronger than the rear end from an RX-7. There is
also the Mazdaspeed Racing differential to consider as a direct drop-in
for the miata.

Of course, if you want to drag race, just drop a 9 inch solid Ford diff.
in there and forget about the handling. :-)

Finally, any 5 lug conversion will require new wheels......

Pat

Chuck wrote:
> If you were going to add some serious horsepower, a modified RX7 rear end
> with the 5 lug hubs might be a useful addition.


Ok, does anyone have a generally accepted figure on horsepower/torque
numbers where switching to more than 4 lugs becomes a good idea or even
mandatory?

Pat

pws > wrote:

>Chuck wrote:
>> If you were going to add some serious horsepower, a modified RX7 rear end
>> with the 5 lug hubs might be a useful addition.
>
>
>Ok, does anyone have a generally accepted figure on horsepower/torque
>numbers where switching to more than 4 lugs becomes a good idea or even
>mandatory?

Not clear to me why you would need more than 3 except maybe to accommodate
very weak light wheels. Fewer, thicker lugs would have an advantage
in bending resistance.

Leon
--
Leon van Dommelen Bess, the Miata Bozo, the Miata
http://www.dommelen.net/miata
The only thing better than a white Miata is two white Miatas

Leon van Dommelen wrote:

> Not clear to me why you would need more than 3 except maybe to accommodate
> very weak light wheels. Fewer, thicker lugs would have an advantage
> in bending resistance.
>
> Leon

I wonder why four is the minimum you ever see on typical cars, with 5
lugs being common even on low-power cars.

Of course, Formula One cars use only one in the middle.

I have seen this setup with a single center lug on a miata before as
well, it was pretty nifty. The owner had lots of work space, a good
floor jack, and power tools.
I would think that he could swap his wheels from front to rear in about
5 minutes per side, even faster if he had a good pit crew. :-)

Pat

pws > wrote:
> Leon van Dommelen wrote:

> > Not clear to me why you would need more than 3 except maybe to accommodate
> > very weak light wheels. Fewer, thicker lugs would have an advantage
> > in bending resistance.

> I wonder why four is the minimum you ever see on typical cars,

Because if you one of them falls off the wheel will still be secure with
the other 3. Someone I knew drived for a while with one lug missing. In a
car with only 3 (small French cars, specially Citroens used to have only
3), if one falls off the wheel will not be secure with only the other 2.

> with 5 lugs being common even on low-power cars.

I suppose aesthetics reasons are part of it. Also, some manufacturers
probably use 5 lugs on the smaller models so they don't need different
parts for each model. But if there is a technical need it is probably
related to the weight of the cars (which has increased a lot in the last
2 decades) and not the power. Power is transmited by friction between
the wheel and the hub.

--
http://www.mat.uc.pt/~rps/

..pt is Portugal| `Whom the gods love die young'-Menander (342-292 BC)
Europe | Villeneuve 50-82, Toivonen 56-86, Senna 60-94

Rui Pedro Mendes Salgueiro wrote:

> Because if you one of them falls off the wheel will still be secure with
> the other 3. Someone I knew drived for a while with one lug missing. In a
> car with only 3 (small French cars, specially Citroens used to have only
> 3), if one falls off the wheel will not be secure with only the other 2.

Thank you for the clear explanantion. Those can be rare around here at
times. :-)

I looked at a couple of salvage cars that a lady was selling. One of the
cars had obviously lost a front wheel and had fallen to the street. I
asked her about it and she said that some (unwitnessed) kids had
loosened every one of her lugnuts but had not taken the wheels.
Then she mentioned that her ex-husband worked on the cars when they were
married.
Kids who vandalize like to immediately see the effects of their
vandalism, and loosening the wheels could get an attempted murder
charge. Even if they don't realize how serious it is, there just isn't
much thrill to them by loosening parts and wondering if anything will
happen later.
It sounds to me like hubby did not want to pay for a divorce lawyer.

> I suppose aesthetics reasons are part of it. Also, some manufacturers
> probably use 5 lugs on the smaller models so they don't need different
> parts for each model. But if there is a technical need it is probably
> related to the weight of the cars (which has increased a lot in the last
> 2 decades) and not the power. Power is transmited by friction between
> the wheel and the hub.

That is what I am guessing with the new MX-5. I am betting that they
either have the same hubs as the Rx-8, Mazda 6, etc., or at least share
some parts from the hub area.

Thanks!

Pat