Brute Force for Primary Engine makes my reflections noisy. Why?

[catpower]

Trying to use Brute Force more for my primary instead of Irradiance Map, but I notice that my reflections get noticeable noisier when I do.
I'm looking at the reflection pass so it's not GI noise that I'm seeing. I won't change any other settings, just go back and forth from BF to IM, and BF gives me much noisier reflections.
Why is that?

Thanks - Chris

3dsMax 2016, Vray 3.40.03

[NicoC]

A few details about your settings would help a bit ...

[svetlozar.draganov]

Maybe the noise comes from the GI itself not from the reflection, what's the difference between the BF and IM in the GlobalIllumination render element?
Check other elements and see from which exactly the noise comes from.

[pg1]

Are you using BF primary BF secondary or BF and light cache?

There is a tick box that uses light cache for glossy reflections.

If you use BF primary and secondary then that might explain the difference

[catpower]

Svetlozar Draganov - ? That's exactly what I stated. That I'm looking at the reflection pass. The GI pass looks fine for both BF and IM.

PG1 - Using LC for secondary but I never use LC for glossy rays.

[svetlozar.draganov]

Svetlozar Draganov - ? That's exactly what I stated. That I'm looking at the reflection pass. The GI pass looks fine for both BF and IM.

Would it be possible to attach stripped down version of the scene for investigation? It might be a bug or something that we have to look closer.
What the reflections of the object actually see, is it possible that those are other objects with BF-GI which is noisier but fine with IM?
Set Affect Channels of the reflective shader to All Channels and see if the noise is now visible in the GI render element as well.