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I have changed front brake rotors and noticed two extra holes in the hub and in the brake rotor. The holes are matching with each other. The purpose of them are unclear for me.

The car: Astra H 2012 model year.

The brake rotor: ATE 24.0125-0131.1

Then I have searched for similar (with extra holes) brake rotor and hub examples and found enough, see pictures in the bottom of the question. There are the cases with non-matching hub/brake rotor holes - 9 in the brake rotor and only 5 in the hub...

The question: what is the point of this extra holes and why in one case them matches (my Astra H) and in another case them doesn't match (Volkswagen Golf, Skoda Octavia)?

Pictures:

The Astra H's hub

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The Astra H's separate brake rotor

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The Astra H's hub and the brake rotor assembled

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EDIT start

The Astra H's brake rotor back side. It is not having drum inside, so it can't be used with brake shoes, thus, these holes can't be designed for hand brake adjustment.

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EDIT end

Non matching holes examples:

The Skoda Octavia's hub and brake rotor

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The Volkswagen Golf's brake rotor

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The Volkswagen Golf's hub

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MiniMax
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1 Answers1

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Some rotors have an M8 threaded hole to use for helping to remove the rotor from the hub (and brake drums sometimes had one or two threaded holes for the same purpose, but not M8...), but most just seem to belt 9 bells of s**t out of it with a hammer until it comes off.

The larger holes you indicate may well be for the original machining process or as a "pass through" hole to allow a screwdriver to adjust a handbrake mechanism for example. Don't forget that a rotor that you think may only fit on a golf, may well fit on 20 or 30 other makes & models... Some brake drums had holes positioned so that the brake shoe clearance could be easily adjusted (either it was the back plate or the drum depending on the design.

Solar Mike
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