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brake upgrade
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J1NX3D  



Joined: 06 Feb 2003
Posts: 1333
Location: New Zealand

PostPosted: Mon Jun 06, 2005 11:16 am    Post subject: brake upgrade Reply with quote

just saw this on pelicanparts. Our 931 5 lug discs are basically same as a 944 n/a's right?

how do these look?
http://www.rennbay.com/product_info.php?cPath=49&products_id=83
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gohim  



Joined: 02 Nov 2002
Posts: 4459
Location: Rialto, CA

PostPosted: Mon Jun 06, 2005 1:31 pm    Post subject: Reply with quote

Looks interesting, and the brakes should bolt right up.

You might have to check into whether the brake circuits need to be changed to front and rear from diagonal, and whether the stock 924/931 brake master cylinder can provide enough fluid flow to make those puppies work.
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cleethorpes  



Joined: 26 Jan 2004
Posts: 186
Location: cleethorpes (oddly enough!)

PostPosted: Mon Jun 06, 2005 10:31 pm    Post subject: Reply with quote

Wilwood calipers, are really good and really cheap!

I've been looking at these, my only concern being getting the mounting brackets.

Seems like $750 might be a bit steep, contact a uk supplier like

rallydesign.co.uk for a comparison.
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bass gt  



Joined: 02 Dec 2004
Posts: 971
Location: Johannesburg for now!!

PostPosted: Tue Jun 07, 2005 3:12 am    Post subject: Reply with quote

Cleethorpes,

Reading the Rennbay blurb, there seems to be no need for any form of adaptor/mounting brackets. So the question is, do these bolt straight up to our 931's?? And if they do, what type of brake pad do they use. I presume it's he normal 944 T pattern, but who knows.
Do any of you guy's out there have any experiance with Wilwood?

Regards,

Steve
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944s2guy  



Joined: 20 Jan 2005
Posts: 143
Location: Banned

PostPosted: Tue Jun 07, 2005 3:52 am    Post subject: Reply with quote

Actually $650 is pretty good deal for a set if you compare that to new OEM rebuilt units (or even new!!). I have used Wilwood calipers on my motorcycles before, good stuff. They ran $375 per caliper for a bike (6-pot/piston version).

Nice to see an upgrade - now someone buy a set for thier 931 and let us know how they worked.
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bass gt  



Joined: 02 Dec 2004
Posts: 971
Location: Johannesburg for now!!

PostPosted: Tue Jun 07, 2005 4:00 am    Post subject: Reply with quote

I think at the current Dollar to Pound exchange rate, these are a bit of a steal!! I presume the 931 brakes are 2 pot?? I plan to give Rennbay a call later, to discuss the issues, and if all goes well, i will buy a set.
Someone's gotta be the first in!!
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bass gt  



Joined: 02 Dec 2004
Posts: 971
Location: Johannesburg for now!!

PostPosted: Tue Jun 07, 2005 4:07 am    Post subject: Reply with quote

Just one more point. Are the front rotors the same size on the 931 and the NA 944? diameter and thickness?
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Smoothie  



Joined: 01 Jan 2003
Posts: 8030
Location: DE (the one near MD, PA, NJ)

PostPosted: Tue Jun 07, 2005 4:54 am    Post subject: Reply with quote

OE 931 calipers are 1 pot - 1 large piston.

Part numbers for both the rotor and the steering knuckle are the same through 924 5-bolt, 931 5-bolt, 924S, 944 Series 1 and early 944 Series 2. The 944 S2 part numbers for those parts changed in '87.

The only possible issue seems to be what Gohim mentioned on the mc fluid supply.
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'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox
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ic932  



Joined: 11 Feb 2005
Posts: 1104
Location: UK

PostPosted: Tue Jun 07, 2005 5:23 am    Post subject: Reply with quote

Swap to a 951 fluid resivoir that will sort out any capacity problems they are all ate so are compatable.I used 928S4 brembos on a 944, the mc had no problems at all.Were those pics of any use bass gt?
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944s2guy  



Joined: 20 Jan 2005
Posts: 143
Location: Banned

PostPosted: Tue Jun 07, 2005 5:54 am    Post subject: Reply with quote

The MC is plenty big enough. The 944/S2/Turbo/968 all use the same MC, pretty sure the 931 is same part number as well. Brake companies are VERY good about stating all that's needed for a liabilty issues, so if it would require a larger MC they would most likely say so.
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Smoothie  



Joined: 01 Jan 2003
Posts: 8030
Location: DE (the one near MD, PA, NJ)

PostPosted: Tue Jun 07, 2005 7:10 am    Post subject: Reply with quote

The issue'd be how much fluid is sent down the lines for a given length of press on the brake pedal, not the capacity of the reservoir. Part numbers for the calipers and mc's are different comparing between 924/931 on the one hand and 924S/944/etc. on the other. I don't know how significant the difference is between the different calipers, but the mc's are notably different with the 924 being a 23mm bore all the way through while the 924S/944/etc. mc's are stepped 23mm-19mm. -And the 924/931 split is diagonal while the 924S/944/.. split is front-rear. So at best you could only be guessing to say the 924/931 mc is big enough, right? Personally, I'd say it's probably big enough, but that would also be just a guess. Point being, it would be wise to ask Wilwood or Rennbay before ordering anything.
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'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox
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cleethorpes  



Joined: 26 Jan 2004
Posts: 186
Location: cleethorpes (oddly enough!)

PostPosted: Tue Jun 07, 2005 7:26 am    Post subject: Reply with quote

Bass, let me know what you find out, as I think I may get a set to.

Not as expensive as I thought as I'd only glanced at a magazine and didn't notice the prices were 'per caliper' doh!
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john h  



Joined: 06 Nov 2002
Posts: 827
Location: Wellington New Zealand

PostPosted: Tue Jun 07, 2005 11:52 am    Post subject: Reply with quote

Smoothie wrote:
I don't know how significant the difference is between the different calipers, but the mc's are notably different with the 924 being a 23mm bore all the way through while the 924S/944/etc. mc's are stepped 23mm-19mm. -And the 924/931 split is diagonal while the 924S/944/.. split is front-rear. So at best you could only be guessing to say the 924/931 mc is big enough, right? Personally, I'd say it's probably big enough, but that would also be just a guess. Point being, it would be wise to ask Wilwood or Rennbay before ordering anything.


Changing to a stepped m/c would be benefical if you're using bigger front calipers. It's easy to fit and only a slight amount of re working of the pipework is required. If you're ever racing a 924 or 931 you should have changed to the stepped set up anyway. Especially if you're running the 4 wheel discs. using a 23 mm in a race environment can lead to one of the back wheels locking up as the wheel is getting teh same presure as a front wheel and then the back starts to un weight as the weight is transferred to the front under heavy baraking - then add in a bit of late braking as you turn in and all of a suden the back brake locks creating a flat spot that just gets worse.
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bass gt  



Joined: 02 Dec 2004
Posts: 971
Location: Johannesburg for now!!

PostPosted: Tue Jun 07, 2005 6:48 pm    Post subject: Reply with quote

John,

I've changed my car's X split to front/rear split as per the 944. I have also added a bias adjuster into the rear line, so hopefully i can avoid this issue. however, if i were to change to the stepped MC, what model does this come from? And is it a straight swap onto the 931 booster unit.

Regards,

Steve
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gohim  



Joined: 02 Nov 2002
Posts: 4459
Location: Rialto, CA

PostPosted: Tue Jun 07, 2005 7:20 pm    Post subject: Reply with quote

The stepped master cylinder was used for all 944 and 951 cars from 82-88. This corresponds with the change from the diagonal braking to front and rear braking, which makes perfect sense.

Diagonal braking would not work with a stepped master cylinder.

However, the same calipers are used by Porsche with both the diagonal braking and front and rear braking systems. The M471 924NA, 931, and early 944 all used the same front and rear calipers, yet the 924 and 931 were diagonal braking while the 944 was front and rear braking. The same master cylinder was used with both the early 924/931/944 front calipers, and with the later model front calipers. The same rear calipers were used for all 924, 931, and 944.

Someone else on the board noted that the change from diagonal to front and rear braking may have been due to the difference in weight distribution, or the difference in weight between the 924 and 944. It could also have been necessary for the increased performance would be required for later 944 and 951 models.
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