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BIG (ish) Brakes.

 
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19marty73  



Joined: 28 Aug 2012
Posts: 25
Location: Wirral. UK

PostPosted: Sun Sep 09, 2012 2:51 pm    Post subject: BIG (ish) Brakes. Reply with quote

I love messing with old cars and I love scrap yards so I set about a brake conversion for my 924. Everybody does the 5-lug swap so I fancied going about it a different way.
Only two hurdles to jump on this one:
1.....keep the front stub axle/knuckle because it's connected to my steering!
2.....keep my 4x108 wheels, cos I like em!
I got to the scrap yard and ripped the front and rear brakes,including hubs, off a 1993 Audi 80. Now think logically and you'll realise that the Audi drives with the wrong wheels, front instead of rear. This means the rear hubs are attached via a stub axle, very similiar to our front axle. After stripping it all down I tried it for size. Very, very close! Also the front brake brake caliper carriers bolts directly to the 924 mounts! Amazing I hear you cry!. I had to machine all the anti lock brake teeth off the hub and 5mm off the rear bearing face on the stub axle to get the hub/disc assembley to be central in the brake caliper. I'll explain better with pictures.

Machined stub axle.

Standard stub axle.


Audi 80 REAR hubs. Even has the rubber dust shield you have on the back of your 924 disc assy.

I fitted some new brake disc shields. Not the unobtainable and expensive 924 ones but 1302 Beetle ones. Re-drilled to fit. I had to open up the caliper hole too.
Now the rear bearing of the Audi hub is the same size as the 924 one! the front one is slightly bigger and I could not find an aftermarket bearing so I had a little sleeve made up to make the bearig journal bigger and I stuck it in place with some Very strong Loctite.


Next, slide that hub on. Use the larger, Audi, bearing retaining washer.


Then brake disc on.


Audi vented disc is 280mm and 24mm wide, a lot bigger than the solid 924.

Onto the brake components. As previouly stated the caliper carrier bolts straight on and the hefty Lucas caliper has a much bigger 56mm piston.

Carrier on!

Pads in, caliper on.


Bolt it all up and replace crappy rubber with a braided hose.

LOVELY!

This set up changes the front track width so I'll prob get away without using a spacer on the front. Remember though, if you try this with your stock 15" wheels they we stick out another 20mm. Obviously the Audi is pcd 4x108 and has the 57.1 centre bore of the 924!
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Rasta Monsta  



Joined: 12 Jul 2006
Posts: 11723
Location: PacNW

PostPosted: Sun Sep 09, 2012 5:08 pm    Post subject: Reply with quote

Great job cleaning up those calipers. . .really makes the wheels "pop."
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Toofah King Bad
  • WeiBe (1987 924S 2.5t) - 931 S3
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!tom  



Joined: 28 Aug 2006
Posts: 1930
Location: Victoria, BC Canada

PostPosted: Sun Sep 09, 2012 5:11 pm    Post subject: Reply with quote

Brake bias?
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78 924 NA
5-lug
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morghen  



Joined: 21 Jan 2005
Posts: 8868
Location: Romania

PostPosted: Sun Sep 09, 2012 5:23 pm    Post subject: Reply with quote

Thats a nice and very cheap way to upgrade your front brakes while keeping the 4x108 bolt pattern...however i'm concerned about strength of the spindle/stup axle knuckle since you machined 5mm off the bearing face you have a 5mm bigger lever to shear the axle off its base.

oh, and clean up all that rust
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MikesCoupeGT  



Joined: 18 Oct 2006
Posts: 470
Location: Ontario Canada

PostPosted: Mon Sep 10, 2012 12:11 am    Post subject: Question answered Reply with quote

That is a great upgrade. I was going to look into this setup myself. With the bigger/vented rotors up front and even solids at the rear, it should improve the braking capability of the 924. When you add in that the two cars share the same bolt pattern it makes sense.

Question regarding the rear. How does the Hand/Parking brake connect? Were there any modifications needed there?

Great job.

MikesCoupeGT
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19marty73  



Joined: 28 Aug 2012
Posts: 25
Location: Wirral. UK

PostPosted: Mon Sep 10, 2012 7:45 am    Post subject: Reply with quote

Hi !Tom. I did some reading on brake bias before I did this conversion. An increase in piston size, increase in disc diameter couple with stiffer suspension, lower C of G and different tyre size and compound will all change the brke bias. I have no idea how though!!!!!! It's one of these science things that goes way above my head. I'm yet to use the brakes in anger but I'll let you know. As long as it passes a Uk MOT brake check, I'll be happy.

Hi Morghen. I too thought of any possible weakness brought on by machining the axle. The company that did it put a radius on the rear face to maintain strength. By moving the bearing inwards I have surely reduced the lever effect because I am now closer to the virtual pivot point?

Hi MikesCoupeGT. I am yet to tackle the rears but will tackle it in the same way. I'll post it when I do. I'vw got my old 924 to practice on.
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