Help - Front Rotors rubbing on A-arm

Fergus · 11-02-2008, 04:20 AM

I have been putting together 911 with 930 engine that was previously owned by someone it would seem had a poor understanding of engineering. As such I keep coming across little problems such as this new scenario:

The vehicle is now basically completed, full engine and suspension rebuild and reassembly of brakes/hubs etc.

On my first drive I could hear a rubbing/squealing of metal on metal that was particually bad on right turns. Closer inspection has identified this as the left Ball-Joint/A-arm rubbing on the front rotor as the clearance is <1mm

From what I can tell the front brakes are 320mm rotors with huge 928 GTS brake calipers and an L-adapter bracket to mount them. If I had been responsible for this upgrade I would know exactly what was involved but as far as I can see the rotors on the left of the vehicle are far too close to the a-arm. Strangely there seems to be plenty of clearance on the right hand a-arm & rotor.

To illustrate the problem I have taken the photos below:

The Problem Left side:

Right side that seems ok:

Somehow the left hand side seems to be closer to the strut, what things would you recommend checking here?

Thanks for the help,

Fergus, UK

tonythetarga · 11-02-2008, 04:39 AM

For starters, it looks like you have two different hubs which could easily account for the difference. You have an ABS hub from a later car on the good side.

Also, are you sure the rotor is oriented correctly on the hub?

Fergus · 11-02-2008, 05:07 AM

Both sides have the same ABS style hubs, you just cant see the castelated section from the angle of the photo.

Both bearing assemblies etc appear the same. And the rotors are correctly orientated and held in place by the locating screws.

Would it be acceptable to tap the a-arm flange surrounding the balljoind in a few mm, it looks a bit deformed to me?

Thanks,

Fergus

tonythetarga · 11-02-2008, 06:52 AM

Quote:

Originally Posted by Fergus

Would it be acceptable to tap the a-arm flange surrounding the balljoind in a few mm, it looks a bit deformed to me?
Fergus

Hi Fergus,
I can't answer that and hope someone else will give you a definite answer.

Chuck Moreland · 11-02-2008, 06:57 AM

Decambered ball joints will move the rotor out about .2 inches. We've had a number of customers use the product for big brake clearance issues.

911quest · 11-02-2008, 06:58 AM

Bent spindle....

Bill Verburg · Bill Verburg's Garage

That's an interesting installation, it looks like 964t 322x32 1 piece rotors w/ 964 stub axles adapted to the 911 strut. Very strange

KTL · 11-02-2008, 08:18 AM

In lieu of offset ball joints, you can also use hub spacers. VCI makes these for their small Brembo adaptations. The spacer goes behind the spindle collar as shown in this picture.

So if you're not interested in max camber and also would like to save some $ (The hub spacers are $50 from VCI, the offset ball joints are $375), the hub spacer is the way to go.

You should also grind away a bit of the A-arm for clearance. You'll have some tight clearance when you turn the strut and the clearance will also tighten up when the rotor heats up- if you track the car. I assume you'll track the car, otherwise the monster brakes are only for show?

Fergus · 11-02-2008, 08:35 AM

Bill your diagnosis was spot on. The PO had fitted 964 hubs to 911 struts. I stripped the hubs down and found this:

The spacer the PO had fitted was a simple collar which had walked past the bearing allowing the rear bearing to slop around on the shaft in a particually dangerous manner.

KTL, those spacers look interesting, I may be able to have something similar machined up which also increases the spindle size for the 964 bearing. The shoulder would prevent the spacer walking out like the very poor and dangerous attempt by the PO who I can only assume was trying to kill himself.

Would original 911 hubs have less offset than these 964 parts any guesses why the PO has done this strange modification?

Thanks a lot for the help,

Fergus

Fergus · 11-02-2008, 08:54 AM

One more brake related question, the car has a standard 1978 brake master cylinder and booster. Should this be updated to 930 brake cylinder for this setup? The rear brakes appear to be C2 Big reds with 322mm disc.

Thanks again,

Fergus

KTL · 11-02-2008, 09:04 AM

The spindle spacers are very simple indeed. They're a press-fit onto the spindle and you can make a thickness that suits your needs. I have three sets in 3, 4, 5mm thicknesses and I am currently using the 5mm. Just make sure you don't make them too thick and end up with wheel bearings that do not ride on the spindle in an acceptable location.

Your master cylinder should absolutely be switched to a 78-89 23.81mm master. Right now you should have a pedal condition that is quite a long travel. Not a very good feel, is it?

Take some more pictures of the rear. Since the front looks to be somewhat of a makeshift assembly, the rear should have some more eyes take a look at it!

Bill Verburg · Bill Verburg's Garage

Quote:

Originally Posted by Fergus

One more brake related question, the car has a standard 1978 brake master cylinder and booster. Should this be updated to 930 brake cylinder for this setup? The rear brakes appear to be C2 Big reds with 322mm disc.

Thanks again,

Fergus

You definetly need a rear setup to match the front, one of the best is 965 rear calipers modified for the 3" 911 trailing arms w/ 930 309x28 rear rotor, use 993 rear calipers if 965 rear isn't available(they are a bit more trouble to mount)

and Yes, you definitely want a '79-89 930 m/c, it's a direct bolt on to the 911 brake booster.

The 964s never used 322 rear disks, it could be a 993tt/RS rear which was 322x28. For that to work(retaining the parking brake) both the caliper and rotor need modification

The usual way to use those brakes is to use 993tt 2 piece fornt rotors w/ a flat hat.
looks like this

In back the 993tt or RS rear caliper on a 322 looks like this

the 930 309x32 w/ 965 or 993 rear looks like this

Chuck Moreland · 11-02-2008, 10:00 AM

Looks like your axial to radial caliper adapters were home-fabbed from some lightweight angle stock. AL?

That is going to flex and is not nearly strong enough. This is some scary "backyard engineering" by the PO.

Between that and the slipping spacers he created, I would be looking the whole car over. You may find more creative and usafe designs.

Fergus · 11-02-2008, 10:16 AM

Bill,

I seem to have the same caliper setup as in your second photo, I don't have another jack free but I think you can see the caliper and rotor through the wheel spokes well enough.

I will try and get a 23.81mm master cylinder asap.

Chuck,

That Ali is 12mm thick AL angle, its heavier than it looks in the photos but I agree it doesn't give me much confidence either. Would the VCI adapters fit this setup or have the 964 hubs mixed things up too much?

Believe me everything else on the car has been appart and thoroughly checked over I found many such bodges but have put them all right as I bare shelled the car. The Front hubs and brakes are the last unknown.

Thanks a lot for the help with this guys.

Fergus

MotoSook · 11-02-2008, 11:53 AM

Wow...that arangement can't even be called backyard engineering. It's backyard dangerous. The caliper adaptors are scary. I do find it interesting that the PO used 964 hubs. I'd like to see more pictures of that installation showing how the outboard bearings sit. Maybe post a series of pictures showing the wheel off and sequential parts removed.

Additional data points. I too have the VCI front caliper and 951 setup as Kevin. I seem to recall having 5 mm or 6 mm stainless (304SS) spacers that could be machined easily. I had to grind away a bit of the flange on my A-arms. If one decides to do this, be careful not to take too much off the flange and to make sure one can still take the ball joint off - don't roll the flange over onto.

Bill Verburg · Bill Verburg's Garage

It's not even 964 hubs
this is a 964 hub, the top 2

What you have looks like the 964 stub axle, some how bolted to a 911 strut

here is a 993 hub which uses the same sort of stub axle, you can see inner end of the axle w/ the abs wheel

The rear is definitely a 964/993 or 965 rear caliper. the 964 would be 28/30 the other 2 30/34. You want one version or the other of 30/34. The rotor appears to be a 930 but it also appears to be mounted on the wrong side of the car. 930 rotors are chiral, they have a left and right.

Fergus · 11-02-2008, 02:54 PM

Bill,

Cheers for the heads up on the rotors being on the wrong side, the PO had some kind of death wish, if it could be done wrong it was done wrong! The rear calipers were on the wrong sides when I got the car and could not be bled, I hadn't noticed the drill pattern in the right rear calipers though, bizaarly the left hand rear caliper rotates the correct way so the PO has managed to obtaine two left side rear rotors (no doubt at a bargain price) this sort of thing can only happen in Northern England ! I will never head North to buy a car again, they think the local blacksmith is at the forefront of technology!

If anyone had bought the car without the view to strip and check everything they would undoubtedly be dead by now.

Thanks again,

Fergus

KTL · 11-02-2008, 04:09 PM

I can't visualize how the 964 setup Bill pictured could possibly be adapted to fit upon the 911 strut spindle. Are we sure those hubs pictured behind Fergus' rotors is not a later 944 hub with ABS rings upon it? I'm not familiar with 944 front ends, so i'm completely guessing here. But I do know the 944 front hubs are seemingly similar in shape & design.

I agree with Souk- show us some more pictures of the front rotor and hub assembly so we can further criticize it!

MotoSook · 11-02-2008, 04:55 PM

Good call on the 968 and later 944 hubs, Kevin. I'm not familiar with them either, but I'm very interested to see what the heck that thing is!

Fergus · 11-03-2008, 12:23 AM

KTL,

They may be 944 or 968 hubs, maybe even 928 hubs? I cannot find any part number on the casting but the outer diameter of the bearings themselves are much larger than 911 bearings. The outer bearing is the correct internal dia for the 911 spindle and the inner bearing is approx 4mm greater dia than the 911 shaft.

I now believe these cannot be 964 items as they have the same oil seal as used on the 911 pressed into the back of the spindle assembly. As you can see from Bill's pictures the seal is on the hub carrier itself on the 964.

I am now back at work for the week so whont be able to investigate further until next weekend. I should have written down the Timken number I saw on the bearing as this may shed some light but I wont be back home during the week.

What other Porsche models use the 911 oil seal?

Thanks again for all the help,

Fergus