SWB rear trailing arms: NEW SWB vented calipers

[Alan.uk]

Hi,

Are there any SWB rear trailing arm experts out there?

Basically are all pre 69 rear trailing arms the same? I am not worried about if they have the socket for the Anti Roll Bar, but is there a difference between ones used on cars which had vented discs or solid discs?

Checking the PET there are two different part numbers, one for the standard 911 and another for the 911S (for the 67 and 68 model). Now this may be just a part number thing, but does anyone know if there are any real differences?

I am building a simple upgrade to enable vented discs to be used on the rear of any SWB car using a new (ATE made) bolt on caliper with no mods, over a new (off the shelf) vented disc. Hence the previous question.

Anyone?

Alan

[John912]

Alan:

I have a very late 67 Normal with vented discs, which I believe were installed at the factory when they were starting to switch over for 68 production where (I believe) all had vented discs. I've been told by some that a PO most likely installed the vented rotors, but told by others that the rear trailing arms are different and the swap is not as easy as changing the rotors/calipers. So let's hear what the experts have to say. I'd also like to know if anyone has a late (308000 and later) original 67 normal car with vented rotors.

Thanks in advance for the info

[BBausser]

My Normal # 308017 has vented discs. I always figured someone had swapped them in the past.

[911quest]

The trailing arms are different the vented calipers have a different bolt spacing then there solid counterparts.

[Alan.uk]

Thanks.

Here is what I already know. Vented brakes came on 67S, 68S, 68L and 67- 911 sportos. The rear calipers and discs are specific to this application. New rear discs are very expensive but 944 rear discs can be used (81-86). I know they may need machining, but on our upgrade they will not need machining.

The bolt spacing is the same for rear SWB calipers but the vented calipers are obviously wider and have larger pistons.

I think there could be a difference between SWB trailing arms in the thickness of the lugs which the caliper bolts to. This thickness governs where the calipers sits over the disc. I don’t have any to measure here, but need to know as when we sell the kit there may have to be 2 styles.

Can anyone confirm?

This is the bit to measure



And a mock up of the new calipers. The disc here is an original vented but we will be using 944 rears



Any help much appreciated

Alan

[preS]

Alan

Before you make multiple sets and possibly shooting yourself in your foot you might consider to check w/ Neunelfer / Eric Scott Shea. He recently provided me w/ an Ate rear Caliper set that takes the same piston (38mm) as the Wide L (S caliper) and has the 2.25" spacing as well. I took the non vented variant at $350 for the pair, to have them converted to vented (adding spacers) was like $100 or so extra.

All the best

Richard

[Alan.uk]

I have answered my previous question by looking at a 68 Sporto we have in storage. The trailing arms are the same, Porsche used a spacer between the caliper and trailing arm when using the wider L caliper.

Thanks for the heads up Richard. I am sure there are other approaches to this but I needed to do this for some cars we have in for resto, hence going down this route. The other big difference with the calipers we are working on is, no spacers are required and also they will fit over a 944 disc with no machining. For anyone upgrading to rear vented discs or replacing their original SWB vented discs the main option mentioned is fitting 944 rear discs but they need machining down slightly (in terms of diameter) thus every time you need to replace your brake discs you also need to visit a machine shop. The ones I am working on fit straight over the 944 disc no machining required, thus keeping replacement parts as being direct off the shelf parts.

Thanks again

Alan

[911quest]

Some please advise on the standard caliper spacing....I just went and measured a set of 67-68 S/L trailing arms and came up with roughly 2 1/2inchs I thought there was a spacing difference....

[2.5MFI]

I went to vented rotors and correct calipers on 66 a few years ago and there was no problem with the swap. Nothing different about the SWB arms except the ball for the sway bar. Others may know more.

[Neunelfer]

The trailing arms are different the vented calipers have a different bolt spacing then there solid counterparts.

Utt uhh...

All the early trailing arms have the 2.25" spacing. They are the same.

You can bolt a "Wide L-Caliper" to any of the early arms and, by using the dogbone spacers and 944 discs you can have a vented rotor.

The Wide L-Caliper has a larger 38mm piston, 10mm spacers and it went up to M7 fasteners vs. M6 on the L-Caliper. The Wide L-Caliper uses the #30 pad vs. the #31 pad for the later 911 rear M-Calipers.

ATE makes a caliper for the Alfa 105 and 110 models than will bolt on in this application. It still uses the #30 pad but there are spacer kits available for this caliper. Bolt on.

What we are looking for and, hopefully you can supply, is an spaced out ATE bolt on that uses the #31 pad with the 2.25" spacing. I believe there is an Alfa caliper out there and this could be the ideal solution. We're getting close to finding it. If you have one, I have a customer for you.

This would basically allow any SWB car to have the equivelant of say... RS brakes. A set of struts and a-arms up front loaded with S-Calipers and 38mm rear pistons and a #31 pad in the rear = Rear M-Caliper.

Keep us posted and please don't make it too expensive, especially if it's an off the shelf ATE because I'm currently sourcing the same thing. If you can do it economically then I'll get them from you vs. finding the caliper myself.