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brake upgrade on 931 Carrera GT

 
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stan911  



Joined: 06 Jan 2021
Posts: 5
Location: France

PostPosted: Wed Jul 19, 2023 6:22 pm    Post subject: brake upgrade on 931 Carrera GT Reply with quote

Hi guys,
first post on this forum!
I am located in France and bought this Carrera GT replica 2 years ago.
It has been a daily for a while, has travelling long distance road trips and is slowly being upgraded.
It was born 931 in 1981 and was shortly after (1983) transformed in a 937 by Mr Tegi of Rennsport autoclassica in Modena. He kept it until 2021 when I bought it. I didn't know much about these cars apart from the basic figures and public knowledge but it was love at first sight and I drove it back home 1400 km in a day. I kind of knew it was special and it drove amazing well although very (too?) rich.
My friend Mischa Blumel who knows these GT and GTS really well went trough the car last winter and we had few good surprises. All the fiber parts are Porsche original including GTS bumper, flares, rear spoiler and then the Turbo happens to be a gts one, forged pistons and cams are gts too...
The car is fast and the braking is just not up to the level on occasional track days. Yes I could get Pagid yellow and cooling material but I got a good deal on 944 turbo (1985) calipers, spindles (being machines for the speedo),hubs and discs. I was also Lucky enough to get 1985 944 T aluminium arms.
I am in no rush to do the change and have read a lot of stuff on this forum but some information is confusing. So here are few simple questions that I hope will find simple answers.

Rear calipers: do 944T 1985 calipers and discs fit the 931 rear steel arms without any modifications or do I need to mount 1985 aluminium trailing arms and I presume the spring plates?
Front: are 944 T calipers+discs+spindles+hubs a direct replacement or do I need other parts (I have Gaz shock struts at the front).
I just want to take the time and gather all parts before I do the job, the journey is fun.
Your help is very welcomed !


Until I find out how to have embedded photos, here are the links
https://www.amazon.fr/photos/share/r8NzgPB0ivHRQs4NMfLbgAjRR0NS6xMh028XJDvvDM7
https://www.amazon.fr/photos/share/Qy0jYVgBCAh1gDHYJVd0Ppf9BTz5NHq86Ck8xJ8e7Xd
https://www.amazon.fr/photos/share/ccMpnIKGPlI3awF6sB5DyJ7CV8CK283tpe40KASykLo
https://www.amazon.fr/photos/share/6CtNmaoKkvTOt6Srfo8L2wRgUexidy9GRofTtFsYXWR
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kondzi  



Joined: 02 Jul 2018
Posts: 485
Location: Poland/EU

PostPosted: Wed Jul 19, 2023 8:23 pm    Post subject: Reply with quote

Hi stan911.
It looks like a very nice car to drive

Regarding brakes, rear 944T fits nicely, P'N'P.
You need the early 951 rotor though.

What I did for my 931 is front calipers from 997 C4S (or 996T - same caliper) and rear calipers from 951.

Here is the thread where I showed what I did, however my home picture server died and I don't have the photos loading to the forum (but have lots of photos on my phone/laptop).

https://www.924board.org/viewtopic.php?p=402524&sid=750c09255b78372d13494d64c4e62cac

So if you're interested, just PM me, and I'll tell what an why.

Front rotors I took from 997 C4S as well, which means these are 34x330mm and won't fit 16" wheels.

I did fit that caliper in a 16" Fuchs though (in my 911), but with a rotor that's c.a. 310mm in diameter.

I did replace the brake master cylinder to a 25.4mm one and also replaced the X-setup braking lines to a more common sense Front-Rear one.



The interesting thing is you can fit a rear rotor from a 930 (911 turbo) that is 28mm wide, rather the one from 951 (24mm wide), but you need to split the calipers and add 4mm spacer between the halves.

Some time ago I talked to Pawel Wojtowicz, he races in Poland in his 944T Rothmans https://www.youtube.com/watch?v=Gc0y3NudKbI and he's using almost the same setup as I do (seems works well ).

The only difference is I use MC from Mercedes and he's using one from Subaru.

I can't tell if front 951 caliper fits P"N"P though (I expect not), as I did go for the more powerful setup at the beginning anyway.

The braking with my setup i really really good

EDIT: Oh and if you want your car to handle even better, I can supply you with these (link to a thread with photos)


https://rennlist.com/forums/924-931-944-951-968-forum/1307233-billet-torsion-carrier-mounts.html?ispreloading=1





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Konrad
'89 951 US
'88 Mustang 5.0 LX Convertible (factory specs)
'84 911 Carrera 3.2 RoW (factory specs)
'81 931 RoW (TBD)
'81 Ford Capri 2.8i (factory specs)
'79 Ford Capri 2.9 (heavily modded)
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peterld  



Joined: 10 Dec 2006
Posts: 946
Location: Noosa Heads QLD Australia

PostPosted: Wed Jul 19, 2023 8:38 pm    Post subject: Reply with quote

Lovely car Stan.

At the rear, the 944T caliper will bolt straight up to existing arm, even using 924T disc though the slightly fatter 944T disc is preferable.

At the front, I see no reason for what you have, to be able to be bolted up to Gaz struts. I only have experience with the whole strut approach, or cobbled up versions of 944 n/a hubs. I believe the hole size and spacing of strut to spindle is common across the range.
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80/81 932/8 ROW


Last edited by peterld on Mon Aug 21, 2023 10:58 pm; edited 1 time in total
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morghen  



Joined: 21 Jan 2005
Posts: 8883
Location: Romania

PostPosted: Wed Jul 19, 2023 8:43 pm    Post subject: Reply with quote

Very beautiful and interesting car!
Cool story as well.
Take good care of it.
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Cedric  



Joined: 27 Aug 2004
Posts: 2609
Location: Sweden

PostPosted: Thu Jul 20, 2023 2:31 am    Post subject: Reply with quote

I would do race pads and brake ducting first before doing all the mods, especially if its only an occasional track car. With a GTS turbo you wont have gobs of power anyway.
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1980 924 Turbo
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kondzi  



Joined: 02 Jul 2018
Posts: 485
Location: Poland/EU

PostPosted: Thu Jul 20, 2023 9:33 pm    Post subject: Reply with quote

Cedric don't be that pragmatic, give a little fun to us
_________________
---
Konrad
'89 951 US
'88 Mustang 5.0 LX Convertible (factory specs)
'84 911 Carrera 3.2 RoW (factory specs)
'81 931 RoW (TBD)
'81 Ford Capri 2.8i (factory specs)
'79 Ford Capri 2.9 (heavily modded)
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stan911  



Joined: 06 Jan 2021
Posts: 5
Location: France

PostPosted: Thu Jul 20, 2023 9:58 pm    Post subject: Reply with quote

Thank you all guys for your responses. I am going to carry on this fun journey, the back is a straight shot and I will start the front once I have machined the front spindle for this speedo cable.
will kept you posted
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Beartooth  



Joined: 05 Apr 2022
Posts: 206
Location: Roberts, MT

PostPosted: Fri Jul 21, 2023 3:14 am    Post subject: Reply with quote

Just personally, I'd go with Cedric's approach first and see if that produces acceptable results. You might be happy with the stock brakes (done up right), and I think that's what Cedric is getting at. Nothing wrong with going bigger though! I'm already breaking my rule of answering the question you didn't ask; different budgets and priorities, obviously. Either way, it's a great car; glad to see it's being used and enjoyed!
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morghen  



Joined: 21 Jan 2005
Posts: 8883
Location: Romania

PostPosted: Fri Jul 21, 2023 7:19 am    Post subject: Reply with quote

I had the 951 M030 brakes on my gts wannabe and they were fantastic if you had grip, and horrible if you didnt have grip.
The 931/44 brakes are a pretty good balance and with good pads its a very good braking system, not to be thrown away.
But if you do upgrade and want to throw the old parts out, throw them my way, i have good use foe them to upgrade a friend’s supercharged 924 to 5 lug.
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turbobob9242  



Joined: 08 Feb 2003
Posts: 138
Location: Hinckely Ohio

PostPosted: Sun Aug 20, 2023 6:25 am    Post subject: Reply with quote

very cool
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80 9214 turbo, w 5.3 LS V8
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 2309
Location: Somerset, UK

PostPosted: Wed Sep 20, 2023 8:14 am    Post subject: Reply with quote

I'm running stock callipers, discs, Mintex 1155 pads and Racing Blue fluid and 270bhp. Can stop on track without issue cold or hot. Can lock up all 4 wheels on command. For sure some 944t Brembos would do the job more efficiently, but don't disregard the stock set up before making all the easy upgrades first.
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1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
Now www.924board.org/viewtopic.php?t=34690
Then www.924board.org/viewtopic.php?t=31252
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