2.0 D4D Front Disc Size

[Ian Kasher]

Hi Everyone, this has probably been answered many times, I have a 2.0D AWD Invincible and looking to change the front discs, I’ve been on the Mtec website and there are two disc diameters which are both compatible with my vehicle 296 & 328mm, will either size fit?

[philip42h]

If I were to guess - because I certainly don't know - I'd note that the RAV4.4 came with either 17" or 18" wheels, and suspect that the smaller of the discs was appropriate to the 17" wheel while the larger was appropriate to the 18" wheel ... possibly?

Edit: The technical specs state: Front (diameter x thickness, mm) Ventilated discs 296 x 28

Alternatively, you could, perhaps, just measure the diameter of the existing discs ... 😉

[Ian Kasher]

Thanks for reply, I’m towing a caravan later on in the year just thought that if the larger discs fit it may give a little bit more stopping power.

[Stivino]

53 minutes ago, Ian Kasher said:

Thanks for reply, I’m towing a caravan later on in the year just thought that if the larger discs fit it may give a little bit more stopping power.

There won't be any more stopping power even if you were to fit jumbo sized discs.  Stopping power will be determined by the contact area between the disc and the pad, amongst other things.

What are the different diameters of the discs you are looking at and, why can't you narrow it down to only one disc?  Try more websites until you are certain.

[RAV4-D4D]

Presumably to get better braking capability you'd also need to change the calliper (a) accommodate the larger disc (perhaps?) and more importantly (b) because if you don't the surface area/point of contact of the pad with respect to the disc won't change (ie the pad is still gripping the disc at the same radius from the axle and the extra diameter will never get used.

Happy to learn otherwise if I am mistaken.

 

 

[flash22]

https://www.brakebook.com/bb/public/applicationSearch.xhtml

It depends on the engine, is it the bmw 2WW if so what size wheels

[Ian Kasher]

Thanks for reply, I’m towing a caravan later on in the year just thought that if the larger discs fit it may give a little bit more stopping power.            
                                                                                                                                                                                                 For the same force between the disc and pads, a bigger rotor generates moretorque on the wheel - i.e. more stopping force. ... So, for the same caliper and brakepad, a bigger rotor generates more braking for the same pressure or the same amount of braking for less pressure.

[Stivino]

55 minutes ago, Ian Kasher said:

Thanks for reply, I’m towing a caravan later on in the year just thought that if the larger discs fit it may give a little bit more stopping power.            
                                                                                                                                                                                                 For the same force between the disc and pads, a bigger rotor generates moretorque on the wheel - i.e. more stopping force. ... So, for the same caliper and brakepad, a bigger rotor generates more braking for the same pressure or the same amount of braking for less pressure.

Where did you see that?

[Ian Kasher]

I just googled do larger disc diameters improve braking efficiency, the principle is correct, I met ring Mtec and ask why they offer two different disc sizes for my model, I’m sure there will be logical answer. 

[Stivino]

3 minutes ago, Ian Kasher said:

I just googled do larger disc diameters improve braking efficiency, the principle is correct, I met ring Mtec and ask why they offer two different disc sizes for my model, I’m sure there will be logical answer. 

Would you like to share a link to where you saw it?

[RAV4-D4D]

I think that quote is slightly misleading as I believe when they say the same calliper they are referring to whether is it's single pot or 4 pot etc. In reality you would need to have longer calipers to move the pads further towards the outer edge of the disc in order to benefit from the extra braking capability.

In fact, if you were able to squeeze bigger discs into the existing callipers then you'd actually reduce the braking (very marginally mind) as the the extra disc weight would have greater inertia but without any extra braking capability for the reason I first gave.

[_dct_]

4 hours ago, Ian Kasher said:

Hi Everyone, this has probably been answered many times, I have a 2.0D AWD Invincible and looking to change the front discs, I’ve been on the Mtec website and there are two disc diameters which are both compatible with my vehicle 296 & 328mm, will either size fit?

328mm rotor is matched with a dual-piston caliper which as far as I know is only available on the hybrid version (UK only - not sure about elsewhere).