Track width and spacers

[Peter Empson]

We've been experimenting with spacers on my white car as it looked a little odd when the arches weren't being properly filled. Through a process of trial and error we've ended up with 10mm spacers at the rear, anything wider and it will rub the offside arch. The front currently has 15mm ones. I can't feel any problems with this on the road, but am trying to get my head around what is correct to ensure balance when I get it on track.

A quick google brings up an original 944's track width as being approx 148cm front and 145cm rear.

I've measured the effective track width of my current setup as 149cm front and 148cm rear, so basically more rear grip which I imagine will result in an increase in understeer (the setup without spacers has almost none). The question is, I'm really not sure how much difference will be noticeable. Any thoughts?

For reference the setup is as follows:
Fronts: 7.5" ET65 with 15mm spacers
Rear: 9" ET55 with 10mm spacers

 

[edh]

Did you put longer wheel studs in Peter? - I tried 6mm spacers on my fronts, which looked good, but didn't have enough thread left.

 

[TTM]

I would have thought that 15mm spacers at the front may have made the steering feel heavier?
I once tried 15 mm spacers all round on my S2 and the additionnal weight of the steering was unpleasant to the point of negating the benefits in oversteer. This was with 16" wheels though.

 

[Peter Empson]

Longer wheel studs will be going on the rear if we keep them, but for road testing there seemed to be enough thread, the fronts are the fancy ones with integral studs.

I can't say I've noticed the steering being heavier than before to be honest, but then I'm so unfamiliar with it now that I suppose it's hardly surprising.

 

[sawood12]

I certainly noticed a slight difference when I fitted 6mm spacers at the front. In theory to maintain the same track as standard I needed 3mm spacers but struggled to find them at the time so went for 6mm. I felt it definitely improved turn-in. I guess it is the width of the front relative to the rear as to whether it will induce understeer or oversteer rather than actuall track width.

Anyone know how the minimum number of threads you need if you fit spacers? I've got 6mm spacers on the front with standard studs but there is plenty of thread. The thickness of the hub of the wheel seems alot less than the old Teledials that were fitted before. I'm pretty sure I'm OK but would like to be sure.

 

[edh]

try it with open wheel nuts - you may be suprised. I only managed to get about half the nut wound onto the thread with my clubsport rims - not enough to be safe. One of my friends told me there is a blue book spec for this.

 

[TTM]

You can also fit spacers fitted with studs to avoid fitting longer studs?

 

[sawood12]

ORIGINAL: edh

try it with open wheel nuts - you may be suprised. I only managed to get about half the nut wound onto the thread with my clubsport rims - not enough to be safe. One of my friends told me there is a blue book spec for this.

With steel nuts then you only probably need about seven or eight full threads, but with our alloy nuts you're obviously going to need more. Anyone know if you can actually remove the studs altogether and use the bolts from a modern Porsche?

 

[Neil Haughey]

I run 15mm spacers on the back and 6mm spacers on the front. Some of the 944 and 968 racers fit very big spacers on the front, they look like 15mm to 20mm thick. I say some though because I am sure the 968 which won at Donny last week didn't have any spacers on. Increasing the rear track relative to the front tends to alter the geometry such that the car transfers weight to the rear earlier, the downside being the front of the car can lift a little on the run in to corner apex, bad. The Good side is you can get on the throttle earlier and drive the car round corners on the throttle rather then throttle on tending to cause the car to push understeer. What this meant for my own car on softish 200 lb springs was it could go as fast as anything through 60 to 80 mph corners, was a bit slow in slow speed bends and would understeer very easily on turn in to high speed corners. It also IMHO leads to a set up that as it exploits grip from the back end more doesn't work as well in the rain. Ultimately I believe the optimum approach may be to run several different setups for different tracks each running a different combination of damper rates, track widths, front camber, possibly ARB setting and possibly spring rates although I think you can juggle the other settings without changing spring rates.

I strongly suspect that going the other way and running more track on the front, say 20mm spacers will give very good corner entry, be better in the wet etc opposite to increasing rear track.

The 15mm spacers I have look like those in the picture with their own studs.

 

[Big Dave]

On my 968 + previously my S2 i run 20mm spacers on the fronts, with 8"/17" et70 cup1,s. Making an effective et50...
These are the plain spacer tye without the studs attatched...So i can remove the spacer at will....
At the rear ive fitted a pair of 6m spacers...
Ive removed ALL the wheel studs + fitted longer studs, so i can fit anything i want to... Also fitted steel wheel nuts...

It makes for a very varied + easy to "play around with" job....[][][]

 

[Hilux]

Anyone know how the minimum number of threads you need if you fit spacers? I've got 6mm spacers on the front with standard studs but there is plenty of thread. The thickness of the hub of the wheel seems alot less than the old Teledials that were fitted before. I'm pretty sure I'm OK but would like to be sure.

Take the length of the stud and add the width of the spacer, anything else is WRONG. If you`ve got closed nuts it must not be compromised as the high torque settings are designed to grip over a given number of thread lengths. Porsche dont make it up!

With steel nuts then you only probably need about seven or eight full threads, but with our alloy nuts you're obviously going to need more. Anyone know if you can actually remove the studs altogether and use the bolts from a modern Porsche?

With any open nut there should be at least two to three threads protruding.

Ive removed ALL the wheel studs + fitted longer studs, so i can fit anything i want to... Also fitted steel wheel nuts...

It makes for a very varied + easy to "play around with" job....[][][]

S`wat I`d do, its the only SAFE way to play []

I strongly suspect that going the other way and running more track on the front, say 20mm spacers will give very good corner entry, be better in the wet etc opposite to increasing rear track.

Yup, Westy/Cateringvan sprint drivers fit wide track front double wishbone suspension and I`m currently researching alternative A arms for my Mk 1 Golf project. Mk 2`s use Passat arms and extend the steering/track rods, alternative is mahoosive spacers [&:].

 

[Tam Lin]

ORIGINAL: sawood12

I I felt it definitely improved turn-in.

I would think that there could be an element of added instability at the front helping turn in, through a further reduction of negative scrub. I'm hazy which 944/968s had negative/positive scrub radii. When I experimented with less negative offset at the front on my 924s, effectively the same as a spacer, I found the car was far more twitchy, especially under braking, but it did turn in better, and slight changes in negative camber made more of a difference.

 

[Peter Empson]

Thanks for the comments, all very useful. I think I'm now happy to stay with this setup for the time being (with longer studs on the rear of course) and see how it works at Silverstone next month.

 

[sawood12]

ORIGINAL: Hilux

Anyone know how the minimum number of threads you need if you fit spacers? I've got 6mm spacers on the front with standard studs but there is plenty of thread. The thickness of the hub of the wheel seems alot less than the old Teledials that were fitted before. I'm pretty sure I'm OK but would like to be sure.

Take the length of the stud and add the width of the spacer, anything else is WRONG. If you`ve got closed nuts it must not be compromised as the high torque settings are designed to grip over a given number of thread lengths. Porsche dont make it up!

You're right of course to retain the same factor of safety, but Porsche will be acting on a significant factor of safety (5x or more which is typical in automibile design) - in fact you could probably run safely with only four out of five nuts as Porsche will have designed against maintenance error and assumed the case where one of the nuts may not have been torqued up properly (though of course i'm not recommending anyone run with only four nuts - the saving in unsprung weight is not that significant!!). So it is probably perfectly acceptable to lose a few threads per nut without compromising anything.

The rule of thumb about the number of exposed threads over an open nut is to do with stress relief in the stud threads above the nut. If you cut the stud too short then it significantly increases the stresses lower down. However this rule of thumb doesn't guarantee if you've got enough engaged threads which is determined by the depth of the nut. Also if you use closed nuts and longer studs and the top of the stud is torqued up against the top of the inside of the nut then you'll be compromising the strength of the nut significantly.

I guess the best thing to do is to measre the depth of the nut, measure the length of stud you've got and aim for a minimum of three-quarters engagement to ensure you have room at the top of the nut.

 

[944 man]

ORIGINAL: edh

Did you put longer wheel studs in Peter? - I tried 6mm spacers on my fronts, which looked good, but didn't have enough thread left.

Apologies if anyone else has already said this Ed: but you can fit the elongated studs from the rear of a series one 944, along with the original spacers.

Simon

 

[944 man]

ORIGINAL: sawood12
Anyone know how the minimum number of threads you need if you fit spacers? I've got 6mm spacers on the front with standard studs but there is plenty of thread. The thickness of the hub of the wheel seems alot less than the old Teledials that were fitted before. I'm pretty sure I'm OK but would like to be sure.

The MSA insist on 1.5 times the studs diameter, if that helps? They also allow spacers, that arent smaller in diameter than the hub, up to a maximum of 25mm. Extended studs are prohibited, but I wonder how tightly this is adhered to...