What is the max size brakes under 13's

[pigeondave]

Will 11" rotors fit under 13" CXR compomotive wheels.
I'd be looking at using wilwood powerlite calipers.

Has anyone done this?

[Furyblade_Lee]

Dave best call Steve at FurySportsCars, he will know. Probobly whatever the front running RGB guys use will be the *best*. Biggest isn't always best, but as you yourself are f****** huge, I am not arguing......

[mikesalt]

According to this from Hi Spec Brake, you can fit 11 inch rotors under 13" wheels. Not sure about doing it with the Wilwoods though.

[pigeondave]

Seen that before, its what got me thinking.
Force racing wheels do a 287mm rotor on their facebook page that only fits their wheels.
I have the powerlites at the moment on 265rotors and fancied a bit of a change.
I was wondering if it was possible with CXR's

[AdiT]

It'd be very tight.

According to RallyDesign when fittied with an 11" rotor, the outside radius for the Powerlight caliper is 6.16" or 156.5mm.A quick measure of my CXR's (in situ' so not accurate) Has an internal diameter of 315mm... so thats 1mm clearance... and there's a bit of a step behind the spokes that wouldn't clear depending on off-set.

[pigeondave]

Thanks for the info Adi.
I didn't see that on their site will have a look tonight.
The Force racing huge conversion has a 3mm clearance with their wheels

[AdiT]

Might not be on the site. I found it in a catalogue from 2008.

You'd have to take off a wheel and have a measure. It's not just the diameter but the profile of the caliper and wheel. The Calipers are chamfered off on the edge so might miss the raised section behind the spokes. I doubt even measuring will be conclusive. You might end up having to space out your calipers to the 6.16" measurement somehow and then try the wheel up to it.

If you go the Force Racing route your current wheels are just scrap value really but I'd take them off your hands as a favour...

[pigeondave]

I currently have them fitted to wreckage I will find out whats going on this friday.
I think I might keep them with A021's fitted for touring and have the force ones for Sunday best.

[pigeondave]

Looks like it might be tight

From the compomotive site



They appear to come in at the spokes

[pigeondave]

Its one the rally design site just had to dig a little deeper

[robcollingridge]

AdiT said:

It'd be very tight.

According to RallyDesign when fittied with an 11" rotor, the outside radius for the Powerlight caliper is 6.16" or 156.5mm.A quick measure of my CXR's (in situ' so not accurate) Has an internal diameter of 315mm... so thats 1mm clearance... and there's a bit of a step behind the spokes that wouldn't clear depending on off-set.

And don't forget that stick-on balancing weights will be in the way. Mine are on the inside my CXRs.

Rob

[S47]

Plenty of single seat racing cars use 13" wheels [Inc F1], If you're after the ultimate brakes for 13" rims then this is the place to look

[pigeondave]

S47 said:

Plenty of single seat racing cars use 13" wheels [Inc F1], If you're after the ultimate brakes for 13" rims then this is the place to look

The only problem is that the single seat racers are light and don't need such massive brakes. But I have been looking at this.

I got some time this week so i might just space the calipers out as far as I can and see if they hit the wheel or not.

[S47]

Pigeon dave
Current F1 cars are I believe 620KGs,
Most 7 type kitcars are 500 something Kgs so their brakes are relevant, Alex Zanardi used Cast iron brakes on his F1 car a few years ago, though I don't know who made 'em.
Hope this helps

[AdiT]

S47 said:

Pigeon dave
Current F1 cars are I believe 620KGs,
Most 7 type kitcars are 500 something Kgs so their brakes are relevant,...

Given that F1 brakes are (a) A closly guarded secret (b) probably cost more per corner than 1/2 a dozen kit cars (c) fit to speecialist hub/wheel combo (that a+b apply to) (d) stopping from almost 200mph, I don't think they are an option... Though I don't doubt Dave has already done an e-bay search for some

[pigeondave]

AdiT said:

Given that F1 brakes are (a) A closly guarded secret (b) probably cost more per corner than 1/2 a dozen kit cars (c) fit to speecialist hub/wheel combo (that a+b apply to) (d) stopping from almost 200mph, I don't think they are an option... Though I don't doubt Dave has already done an e-bay search for some

I can only find indy car ones

S47
I know that theres a 287mm /11.25" kit out there that fit under 13" Force Racing Wheels, but I was asking whats the biggest brakes that will fit under compomotive CXR's as I don't see the point in selling the CXR's to AdiT for scrap value.

[robcollingridge]

Surely you need to chose brake components to fit your car and application? Is this a race car or road car? How much does it weigh? Have you currently got issues with the braking performance? I'm curious to know what is driving you to fit the biggest possible disks on your car. Big brakes disks have disadvantages too.

A lot of race car braking components are not much use on the road as they need to be up to working temperature to perform properly and similarly, they are designed to handle temperatures that you can't reach on the road. They can also be noisy in operation.

I've got 13" CXR wheels with 260mm diameter front disks in my 450Kg Fisher Fury R1 and they are just 7mm thick, to ensure they have minimal mass. The braking performance is amazing and they never overheat on track.

If you change the disks and calipers, then you may find you need to change the brake cylinder too and the front/rear brake balance will also be affected.

[pigeondave]

robcollingridge said:

I'm curious to know what is driving you to fit the biggest possible disks on your car. Big brakes disks have disadvantages too.

I dunno really, I just fancy doing it.
I currently have the top hung pedals so when I change to floor mounted I can spec the correct size master cylinder.

The car is a zetec engined car with a screen, so im guessing 650kg, im currently 113kg. So it all adds up.
Its a road car. The brakes are ok at the moment.
Shirley it's the pad material that makes the difference between road car and race car?

What are the disadvantages of going bigger?
I understand that there's an issue with greater rotating mass but the AP 280mm 10mm thk rotors weigh 1.8kg they don't have the weight info for the 265 or 260 discs.
Does the rotating mass make that much difference?
Wouldn't you make a bigger saving on light weight wheels?


This makes an interesting read http://www.pirate4x4.com/tech/billavista/Brakes/ and shows that all aspects can be calculated to get you in the right ball park regarding balance front/rear and pedal force.

I like to use the forum as a learning tool so if I have got anything wrong please correct me.

[robcollingridge]

OK, bigger disks will potentially give you better stopping power but your car isn't that heavy, that you need to be pushing the limits for 13" rims. If you are going to change the disks anyway, then sure fit something bigger.

Moving to bigger disks will add a bit of weight and rotational inertia (not a big deal) but, the biggest issue will be limited choice of wheels. I'd be more tempted to focus on quality calipers and brake pads in a road car and not try to push the boundaries of what might fit within the wheels.

What you should really be aiming for is good brake feel, nice controlled braking and thus confidence above outright stopping power because a relatively light car like this should stop quickly anyway and it's not like you have ABS right?

Rob

[AdiT]

I'd be cautious of going too big. Especially if it gives just a few mm clearance. Hit a pot hole/rock on tour and buckle a rim, even just slightly, could result in recovery.

Better padsand matercylinder choice (if possible) will improve braking effort. Better cooling will them help you make the most of what brakes you have. Have you got vented discs now? Can you fit brake ducts?