944 n/a to 944 turbo rear brake setup

[james666]

Hi all. I own a VW Beetle which I am turning into a track car. I am using the rear end from a decrepid old Porsche 944 N/A 1968 model, which fits directly in place of the beetle items. My question is this...

I have the alloy rear trailing arms from the 944, spring plate, hub, discs and calipers but want to fit bigger discs (mine are obviously just the N/A 289mm diameter discs.

a) does anyone know where I can get hold of bigger aftermarket discs that bolt on to the hub (I have 330mm discs on the front)

or b) does anyone know if the 944 turbo 298mm discs will fit straight onto my 944 N/A hubs?

I will be upgrading calipers to AP racing 4 pots, therefore will be fabricating caliper brakcets, therefore the bigger disc does not haveto be 'compatible' with porsche calipers etc... I just need a bigger disc brake setup on the rear than the N/A disc has to offer...

If anyone could help that owuld be great, there are not very many articles about changing 944 N/A discs to 944T discs...

Thanks, James

 

[Mike_Pollock]

Hi James

Sounds like an interesting project - would like to see some pictures!

I am assuming that its a 1986 944 suspension rather than 1968!

The 1986 cars can be of two types, the later ones have deeper hubs to take the ABS sensors etc, but I'm not aware of any bolt on larger discs for either type, other than the standard 944 T ones which will bolt straight on, IF you have the later deep hubs, as I don't think the Turbos came with the narrow type.

Hope that helps - if I'm wrong I'm sure someone will be along shortly!

Good luck and let us know how it turns out.

 

[james666]

awesome thanks for your reply... I cannot see any form of ABS wheel (that slotted wheel detector thing) on or near the hub, but if it is inside the hub then I probably cannot see it. I do not know how the ABS 'detector' works/looks like on Porsche 944's.

yes I did mean 1986 ;-)

Not a great photo, but that is the hub/trailing arm I am using...

 

[Mike_Pollock]

I have a late car but dont know exactly what its like in there! (I do know the early steel arm cars well!)
The deeper hubs were only to allow the fitment of ABS - it was only an option to start with.
Sorry cant be more help.

 

[944Turbo]

I thought the change over to ABS hubs was 87/88 so you will probably want early turbo discs the offset is much different on the later ones, I think they might fit straight onto the na hubs,
Tony

 

[james666]

forgive my ignorance... when was the change over between early and late? Would I be right in assuming that the only difference in disc between n/a and turbo, would be the offset/diametre and thickness of the actual rotor/disc itself? i.e. the hubs were identical, and just a larger disck was put onto the same size integral 'bell/hat'? i.e. the internal handbrake would still work, and it would only be a problem of caliper positioning on the disk?

I think I am being confusing!

do n/a and turbo discs look exactly the same (from the wheel side of the disc), except for the diamater and thickness of the disc? I have never seen two next to each other, whereas I am sure loads of you have!

Thanks so much for the advice, you are life savers! I just don't know which 'version' of the turbo disc to buy!!!

Also, what about 968 or other porsche varients? Would any of those 'integral bell/hat and disc' combo's bolt straight on to a 944 hub of my age (not minding about offsets/caliper mountings etc..)?

 

[944Turbo]

Up until (I think) late 87 the hubs on all models had a different offset to the later cars with ABS, the offset was the same across all models pre ABS and for the different offset on post ABS so probably the discs will swap between an na and turbo of the same year. I have a feeling the bearings changed when the ABS hubs were introduced, dont have a copy of pet (parts catalogue) handy to confirm.
Late wheels on an early car sit in too far and early wheels on a late car sit out further.
Don't know of anyone who has swapped the rears over though, think its tricky if you don't have freedom with the calipers. I had some late rear discs kicking around for ages but pretty sure they are binned now. You could try one of the specialists - see if they have an old one you could offer up - where are you located?
Tony

 

[james666]

thanks very much for your help on this, I am a Porsche newbie!!!

I am located in Ashford, Kent.

i have loads of freedom with calipers and offsets etc.. my only real concern is the 'turbo' disc having a different sized bell/hat (that sits over the hub and acts as the outer surface for the drum handbrake mechanism).

if it would be a completely fine straight swap, then it makes me wonder whether 968 discs would bolt on etc.. as a number of places sell a 968 turbo /944 big brake upgrade disc, but none give dimensions, fitments etc.. which is annoying...

 

[944 man]

1987 model year cars (built from September 1986) have the later wider track. 1986 model year Turbos have the earlier narrow track (to suit ET23 / 23mm wheels). The offset change, required to accomodate ABS sensors when the option was introduced, came one full model year after the introduction of the series 2 944 (not to be confused with the S2!). 1986MY Turbo brakes can be used.

 

[james666]

great stuff! thanks very much! I shall try obtaining a set of those! thanks

 

[Mike_Pollock]

On the early and late cars the actual discs are in the same position relative to the centre of the car, the later cars have the hub face (what the wheel attaches to) further out than the early cars.

So the "bell" is longer ie the distance from disc hub face is greater. Approx 2" early and 4" ish later.

If its dry tomorrow I should be able to measure both - the 2.5 is early and the 2.7 is late!

So I would measure the distance from the brake carrier holes to the hub face and that should give you the answer as to which type you have.

I am pretty sure that N/A and Turbo discs of the same year will fit the appropriate hub.

edit - Just as a note of caution, remember some @87 model year cars will have been registered in '86!

 

[james666]

as a guestimate I would say the distance from the 'disc' to the front of the hub is closer to the 4" one. I remember wondering why the bell was so deep. I am pretty sure the car it came off had a 2.5 N/A engine in it though, which contradicts the above info?

I shall measure tomorrow when it is light. If you could measure too that would be awesome!

 

[james666]

oh i undeerstand.. you meant YOUR 2.5 is early and YOUR 2.7 is late.. gotcha ;-)

 

[Mike_Pollock]

Sorry - yes you're right, my cars!
Raining here at the mo and the cars live outside!

 

[Mike_Pollock]

Had a quick measure - caliper mounting holes to hub face early (to 1987 model year) approx 3 1/2 " later (1987 model year on) approx 5 1/2" - difficult to be exact without taking the wheels off, but that should give you some idea.

Keep us informed!

 

[JamesO]

Just measured a spare set of late rear discs, 80mm from the face of the disk to the face of the bell 298mm diameter

 

[james666]

Hi all, long time since the weather has permitted me to continue with the car (at least the brakes)... I believe the size of my discs/offset are the later ones (the offset from disc to hub face) is 100mm so am guessin the 'larger' size version of disc, but I am confused as to what to order on the various websites that sell the cross drilled versions of these discs etc...

I want to fit turbo sized discs to my N/A hub, which as you guys and a few others have told me will be possible as it is just the 'discs' that are bigger in size, not the hub etc... The only problem is, which porsche model do i need to state to the parts suppliers so that i do not get the N/A versions of the disc, and get the turbo versions that will fit?

i.e. on http://www.porscheshop.co.uk/acatalog/porsche_944_performance_brake_components.html I get the following options for their 'performance crosse drilled discs':

Cross Drilled Disc Rear 924Tbo/924S/944-87 (each)
Cross Drilled Disc Rear 944 87- Not Tbo & S2 (each)
Cross Drilled Disc Rear 944 Turbo 86 Only / 928 86-
Cross Drilled Disc Rear 944 Turbo / 944S2 (each)
Which one of these options would be the 'turbo' sized disc, with the same offset as my N/A hub? It is all way too confusing for me!!!

Thanks so much in advance (why do porsche have to make it so confusing! lol)... P.S. Are there any other simple big rear brake swaps that you know people have done on their 944's, i.e. from a 911 etc.... that offer a 'semi bolt-on' soluition to bigger discs on the rear?

 

[Mike_Pollock]

The last one - Turbo / S2 - these are the same, the S2 is a N/A 3 litre 210bhp the turbos are 2.5 litre with 220/250 depending on year

Still wanting the pics[]