Comparison of Tyre selection for 19" and 20" rim

Brake specifications are included in ADR approvals. For earlier D4s the ADR approvals noted the 2 brake sizes and that they were applicable to both engine specifications, although also noted a comment that all 3.0's would be supplied with the larger brakes. Hence technically the 2.7's were able to be fitted to 3.0-engined D4s even though LR did not supply that configuration. I haven't seen the ADR approvals for current D4s but suspect the 2.7 size brakes are not listed as they are no longer fitted to any D4 entering Australia.

I have a my10 D4 guessing the same you did this on so technically I could?

Ah, I assumed a late model D4.

There are other threads regarding fitting LR 18" rims including replacing the rear calipers with 2.7 / later 3.0 versions that might be of interest to you.

I'll go hunting thanks for that. Did you find they performed just as well as the bigger brakes?

The first braking tried to throw me through the windscreen, being excessively aggressive on new discs. I borrowed the local mechanic's rego brake test meter to do brake tests and kept the print-out showing the braking effort easily passed. I only use brakes hard in unexpected circumstances and never found the 2.7's lacking. I haven't heard many complaints that 2.7 brakes are inadequate but V8 D3 front discs are slightly larger than 2.7 D3/D4 (they use the 2.7 calipers but a different bracket) and still allow LR 18" rims but not 17".

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Originally Posted by g5k

I wonder if it was just a choice Land Rover made to beef them up for the 3L not so much that the other wouldn't be legal.

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Clearly they decided the 2.7 brakes were inadequate for the 3.0L. It might have been marketing but I doubt that. Given that the vehicle is complied with the larger brakes for the 3L it would be illegal to fit the smaller to a 3L and will void your insurance. Saying that, it's extremely unlikely that anyone would notice, unless the accident was caused by you running out of brakes and they inspected that aspect of your car post accident.
Bear in mind brakes are balanced between front, rear and master cylinder and it might not be a direct swap of simply the front between them. The manual would shine a light on that as would part numbers. If the master cylinder and rear brakes are the same between 2.7L and 3.0L then that would indicate a direct swap is feasible, bit illegal.

I thought TR improvement was a big reason for the bigger brakes.

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Originally Posted by DiscoJeffster

Clearly they decided the 2.7 brakes were inadequate for the 3.0L. It might have been marketing but I doubt that. Given that the vehicle is complied with the larger brakes for the 3L it would be illegal to fit the smaller to a 3L and will void your insurance. Saying that, it's extremely unlikely that anyone would notice, unless the accident was caused by you running out of brakes and they inspected that aspect of your car post accident.
Bear in mind brakes are balanced between front, rear and master cylinder and it might not be a direct swap of simply the front between them. The manual would shine a light on that as would part numbers. If the master cylinder and rear brakes are the same between 2.7L and 3.0L then that would indicate a direct swap is feasible, bit illegal.

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I don't think anyone is suggesting retro fitting the alternate brakes without going through an engineering certification process, which would ensure legality etc.

My plan is to ask one of the local Land Rover workshops to see if they've done it before and thoughts on it as a start. I'm told changing to the brake setup on the D3 V8 would achieve the 18" fitment and you'd think that if they work on that with similar weight and more power they should be fine for the D4 3L.

By the time you:
Buy the required Calipers
Required brackets
Rebuild them if second hand
New pads
Suitable discs
Engineer for approval

You could buy Compomotives [emoji6]