Front brake caliper piston question.

I have starter rebuilding my calipers and noticed that the pistons in front are of different design the ones in the rear. The Pistons on the front calipers do gave a smooth surface, half of it has a raised ring to it. My question is when putting back the piston where should the raised part be in orientation to the caliper?
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This piscture shows the position of the ridge. Easier to show than describe.

 

John,
Not convinced that the orientation on the image is accurate, maybe someone that has the front wheels out can confirm please?

 

Hard to see in this picture so I drew the red line. The reason is to apply greater pressure to the front, outter part of the pad to help even pad wear.

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First post in this old thread may be helpful: https://www.ferrarichat.com/forum/threads/308-front-brake-caliper-and-brake-line-question.85703/

 

Here is a good explanation for multi-pistoon calipers. The same applies to the single caliper with regard to pad loading and wear. See 1st post by
Vk Gopalakrishnan. (Click more to see the entire explanation.)

https://www.quora.com/Why-do-BMW-brake-calipers-have-multiple-pistons-that-are-different-sizes-in-the-same-caliper

 

Thank you both so much.

 

There should be a template alignment tool for this, at least there is for Alfas. The one in the drawing looks pretty much identical.

 

Another old thread which discussed this: https://www.ferrarichat.com/forum/threads/308-front-brake-piston-cut-outs.14164/#post-207895

 

Google Derek’s 308– second last page has description and photos