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Is bigger rotors with same calipers worth it?

PranK

By PranK,
in Suspension, braking and tyres

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PranK Grand Master

PranK

Posted
Posted

Our Mazda CX7 needs new front disks soon. We're driving to Jindy in January so I'd like to have new ones by then.

Because I absolutely just can't replace part for part and NEED to upgrade I started looking at whether I could improve the brakes at all with some OEM items from another Mazda. And I can! 

The CX9 and CX7 Diesel both have 320mm disks compared to my CX7's 296mm. The only difference for the bigger disks are that the caliper brackets are larger. This means that with the larger brackets, I can run 320's. 

The problem is that the brackets are $270ea from a dealer and the 3 or 4 wreckers I've asked don't have them. 

So while I really want to do this upgrade I'm wondering whether its actually worth it. Will 24mm greater diameter with the same calipers actually make much difference?

Thanks guys,

Christian

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WantGTR Mentor

WantGTR

Posted
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Well 32 33 gtrs are 280mm and vspec brembos are 320mm arent they?

Personally i havent done the upgrade so i cant say first hand but to me i dont think its much of an upgrade.

Considering the car its going on i doubt you would even notice the difference city/traffic driving.

Decent disc/pad change with new fluid. Cheap. Cheerful.

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admS15 Grand Master

admS15

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It would make sfa difference on the street on a runabout car such as your cx7. If you where racing it or doing hill runs, the bigger disc would help dissipate heat better and retain ultimate braking for longer. If the brackets where cheap, i would say do it but at 270 each, not worth it unless you get some from a pick a part type wrecker for cheap cheap.

 

As said above, decent pads and fluid will make the biggest difference and is where I would spend my money.

 

 

 

 

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GTofuS-T Grand Master

GTofuS-T

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3 hours ago, Dose Pipe Sutututu said:

Get better pads and you'll be sweet :)

Also shameless plug, can get you decent deals on DBA stuff

lol offering trader services to THE Admin without paying for SAU trader status :4_joy: bold move.

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ERO54N Community Regular

ERO54N

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Interesting scenario, can we perhaps negate car model and discuss the extremes to highlight attributes associated with big vs small rotors? 

Theoretically, as mentioned above disc size would increase the potential limit of heat absorbtion and dissipation through increased thermal mass. Would material also affect the rate and limit of which the disc could convert force into heat? 

If discs were thicker they would also be able to accommodate larger vanes increasing cooling surface area.

I think also being more further away from the axis the braking moment (as in force over distance) would be increased, increasing stopping power but also may promote locking up? 

I forget, is unsprung weight a good thing or bad thing for handling? Larger brake disks would weigh more, statically lowering the centre of gravity but because not a rigid connection to the chassis may also be a disadvantage in a dynamic situation?  Would rotational mass of rotor be negligible due to being so close to the axis? 

Heavy front rotors would take the trajectional force better under extreme application than lighter rotors, right? This would provide more stability on hard braking when the nose dives onto the front axis?

I don't know, just curious. Any experts in this field? 

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