# Mk3 rear upgrade to Mk4 calipers....can I use Mk4 rotors/pads? Also, is replacing the bearing necessary?



## SirRipo (Mar 27, 2009)

I'm upgrading the rears on my Mk3 to the Mk4 rear calipers, and I've got pretty much everything figured out. Then I stumble across a deal from a local parts supplier, $70 for Mk4 rear rotors/pads. Will the Mk4 rotors/pads work? 

Also, it is possible to replace the rotors without redoing the wheel bearings? They were done in the last year or two and it seems like a pain in the ass to do them. Or is this a "save yourself the headache now and just do it" situation?


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## germancarnut51 (Mar 23, 2008)

No, you can't use MKIV rotors on a MKIII with MKIV rear calipers, they won't work with the MKIII stub axles. 

You don't have to replace the MKIII rear brake rotors (and wheel bearings) unless they are worn-out. But, if the MKIII brake rotors are worn-out, it's always a good idea to buy and install new wheel bearing kits in the new brake rotors you get. 

Infact, on a MKIII upgrading to MKIV rear calipers, the only MKIV parts that are used are the MKIV rear calipers themselves. 

The other MKIV rear brake parts (caliper carriers, brake pads, caliper mounting bolts, brake rotors, and stub axles) don't even fit on a MKIII. 

You use the MKIII brake pads, caliper carriers, caliper mounting bolt, splash plates, parking brake cables, stub axles, and brake rotors with wheel bearings. 

You have your choice of using the one piece MKIV hybrid flexhose/metal hardlines that run from the calipers to the front of the trailing arms, OR keeping the MKIII rear disc brake hardlines, and buying the flex hoses from a Passat to connect the MKIV rear calipers to the MKIII metal hard lines.


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## gangstafun (Mar 7, 2011)

I compared both calipers this morning at work, and I couldn't really see any advantage to swapping over. There's very few differences other than physical that I noticed.


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## germancarnut51 (Mar 23, 2008)

gangstafun said:


> I compared both calipers this morning at work, and I couldn't really see any advantage to swapping over. There's very few differences other than physical that I noticed.


 MKIV calipers are lighter, and since they are alloy, they won't rust ugly like MKIII front and rear calipers. 

MKIV rear calipers are also less prone to seizing than MKIII rear calipers.


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## SirRipo (Mar 27, 2009)

germancarnut51 said:


> MKIV calipers are lighter, and since they are alloy, they won't rust ugly like MKIII front and rear calipers.
> 
> MKIV rear calipers are also less prone to seizing than MKIII rear calipers.


 Pretty much, and the price is usually the same if you're pulling parts from a yard.


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