Trying to figure out if I can safely go 1" per side to make the front track the same as the rear....I currently have 1.25" thick spacers, so I could eliminate those which would be nice.

I figure not that big of a deal on the camber since that is easily fixed by opening up the top of the shock tower
(salvage title car, so no worries about "ruining it" )

For those that have installed turbo-tie rods, do you think there is enough adjustment to move the ends out an inch per side???

hehehe,

some of "F troop" try and make the A-arm wider

offset ball joints etc

Here's a gotcha.. different (lower) effective spring rate!

QUOTE (TimT @ Jul 13 2005, 07:37 PM)

hehehe, some of "F troop" try and make the A-arm wider offset ball joints etc

how much extra "width" does those buy me?

QUOTE (bondo @ Jul 13 2005, 07:39 PM)

Here's a gotcha.. different (lower) effective spring rate!

i thought of that one already, just didn't post it...thanks for the reminder

What if you widened the crossmember and moved the front A-arm mounts? Oooh, just widen the whole car! Good luck finding a wider windshield though.

wider is better

could you construct suspension out of steel tubes and eliminate the torsion bar in favor of a coilover? Then you could set any width and geometry you wanted. Keep the original pickup points on the suspension and attach them to the ball joint lower half and a provision for a sway bar. Maybe use spherical bearings at the pickups also? Just a thought.

QUOTE (bondo @ Jul 13 2005, 07:44 PM)

What if you widened the crossmember and moved the front A-arm mounts? Oooh, just widen the whole car! Good luck finding a wider windshield though.

the wider a-arms would be better....in fact shortening the crossmember a few inches would be best so that the a-arms could be even wider, but I don't think there is enough room for the a-arms to travel up unless major cutting and mods are done to the tub.....

Mike,

You can certainly 19mm without any problems, maybe a little more.

When you lengthen the arms you need to make sure that the inner pivot point does not change in relation to the inner pivot point of the tie rod. THis will mess up your caster and bump steer.

I use 1 inch spacers in the front and 1 1/4 spacers in the rear and so far have had no issues. Of course the car does get a substantial amount of eye balling since it does get driven pretty hard at times!! I'd say keep the spacers.

There is a guy on the Pelican board that had this done on his car. His name is Jack Olsen and the car is BB2. He is a moderator over there and I bet he could give you some insight.

-Britain

QUOTE (Mueller @ Jul 13 2005, 06:24 PM)

(salvage title car, so no worries about "ruining it" )

I want my car back. You're disrespecting it.

QUOTE (MattR @ Jul 13 2005, 10:47 PM)

could you construct suspension out of steel tubes and eliminate the torsion bar in favor of a coilover?

of course. the factory did with the 935's more than 25 years ago, and new 935-style parts are in current production.

you do need to reinforce the upper structure some, since it was not designed to accept spring loads.

QUOTE (Britain Smith @ Jul 14 2005, 12:44 AM)

There is a guy on the Pelican board that had this done on his car. His name is Jack Olsen and the car is BB2. He is a moderator over there and I bet he could give you some insight. -Britain

Jack Olsen is the John Peterson of the 911 world.



Damn evil cars!


M

I think the offset balljoints give you about 3/4 in extra width, but they aint cheap

then you could always do this

for JP

so sitting in traffic I got to thinking again about this.....

it looks like there is room inside the shock/strut well to cut and move the mounting over 1" or more depending how far you widen the a-arms....

the second modification to the steering rack will be just as "fun" to perform

you'd need a "sacrificial" rack so that the ends can be cut off, machined and installed to a good rack....this will cure the problem of the turbo tie rods being too short....

How wide do you want to go? = How deep is your pocket?

Adjustable width 935 front end

Wider is better, as you know. I've done it (by moving the lower control arm mounts inboard and replacing them with tubes and rod ends). My overall stance is a bit wider in the front, but with the coil-overs I have to run a spacer to keep clearance between my spring and tire.

The down side of my setup (as Brett mentioned) is toe out in bump (not sure about caster???), but the upside is good roll center control (very little migration over the range of travel and roll).

You can lengthen the tie rods to accomodate... why would you mess with the rack?

And... when I made my camber plates I actually had to use them to reduce camber... like you're suggesting.

QUOTE (groot @ Mar 28 2006, 11:43 AM)

You can lengthen the tie rods to accomodate... why would you mess with the rack?

I was under the impression from another thread that the tie rods cannot be adjusted more than 1/2" or so....I personally have not looked at mine to see how far out they can go.....

I'd like to go at a minimum 1" per side to make the front and rear track equal....at a maximum 2" per side if I decide on 1" flares front and back...

You have a welder, right?

They can be lengthened more than 1"... you just need that 1" for toe adjustment.

QUOTE (groot @ Mar 28 2006, 11:49 AM)

You have a welder, right? They can be lengthened more than 1"... you just need that 1" for toe adjustment.

I guess so....just something about mod'ing certain components makes me nervous

Do it!!!! It'll make you feel good

Seriously, put a nice chamfer on both sides and build the weld carefully and it will be plenty strong.

QUOTE (groot @ Mar 28 2006, 12:55 PM)

Do it!!!! It'll make you feel good Seriously, put a nice chamfer on both sides and build the weld carefully and it will be plenty strong.

watch out, Muellers going to be playing with power tools

QUOTE (turbo914v8 @ Mar 28 2006, 11:39 AM)

How wide do you want to go? = How deep is your pocket? Adjustable width 935 front end

true story....I sold a set of the needle bearings to a 3.8 911 owner that had that 935 setup on his car and couldn't get any of the local Porsche/Go fast track shops to make it work half-way decent, he went back to stock a-arms w/needle bearings and loves the car even more....


that is a big chunk of change...I don't see going down that path anytime soon

QUOTE (Mueller @ Mar 28 2006, 10:35 AM)

the second modification to the steering rack will be just as "fun" to perform you'd need a "sacrificial" rack so that the ends can be cut off, machined and installed to a good rack....this will cure the problem of the turbo tie rods being too short....

If you do that your changing the inner pivit point and will be causing bump steer. Just make the tie rods longer.

I've stared at this till I'm blue in the face and can't come up with any way to allow a larger backspace wheel/tire to be used......short of throwing the whole works away & starting over. I guess I gotta look at a late model Porsche's front suspenders & see how they do it & if it can be adapted to the front of a 914. I hear that increasing the front track is gud, but I ain't going for someone's say so for a nut buster like that....unless they got a room fulla trophys.

All I want is to run a wide W/T set up without gawd awful scrub radius problems. Pushing out the top mount & the ball joint gain you nothing here.....as I see it. If you move out the bottom an inch or 2 & not the top, you can (or will) 10 deg negative camber (or so) unless you change the angle of incidence twixt the strut & axle.....and even that would gain you a bit more that half your movement of the lower arm.
The strut housing would be at a greater angle(to the earth) & side load the hell out of it. I gots those problems now.

Now,.... a guy could sneak in a sub frame & double A- arm
set up.....

QUOTE (J P Stein @ Mar 28 2006, 05:56 PM)

I've stared at this till I'm blue in the face and can't come up with any way to allow a larger backspace wheel/tire to be used......short of throwing the whole works away & starting over. I guess I gotta look at a late model Porsche's front suspenders & see how they do it & if it can be adapted to the front of a 914.

now that I think of it, I'd still have to run a spacer (not as large) to make room between my wheels and the strut (I have 47mm offset 7" wide rims or almost 6" backspacing)

all this would really do is increase the track which would not be a bad thing for those running flares and spacers "just to fill up the wheel wells"

if I get motivated, I'll pop a wheel off my 911 and snap some pictures this weekend....the 964 series and newer have the "FWD" offset suspension

QUOTE (Mueller @ Mar 28 2006, 01:25 PM)

QUOTE (groot @ Mar 28 2006, 12:55 PM) Do it!!!! It'll make you feel good  :drooley: Seriously, put a nice chamfer on both sides and build the weld carefully and it will be plenty strong. watch out, Muellers going to be playing with power tools

Mueller,

If you're going to put a sleeve over the outside, then cut each end on an angle to both increase the weld area, and avoid having a circumferencial weld on a plane that intersects the axis at 90 degrees. Hot rodder have been doing this for years.

Andys

QUOTE (andys @ Mar 28 2006, 08:01 PM)

QUOTE (Mueller @ Mar 28 2006, 01:25 PM) QUOTE (groot @ Mar 28 2006, 12:55 PM) Do it!!!! It'll make you feel good  :drooley: Seriously, put a nice chamfer on both sides and build the weld carefully and it will be plenty strong. watch out, Muellers going to be playing with power tools Mueller, If you're going to put a sleeve over the outside, then cut each end on an angle to both increase the weld area, and avoid having a circumferencial weld on a plane that intersects the axis at 90 degrees. Hot rodder have been doing this for years. Andys

the angle cut crossed my mind, I was too lazy to draw it, easier to do a rotational cut

QUOTE (J P Stein @ Mar 28 2006, 04:56 PM)

If you move out the bottom an inch or 2 & not the top, you can (or will) 10 deg negative camber (or so) unless you change the angle of incidence twixt the strut & axle.....and even that would gain you a bit more that half your movement of the lower arm. The strut housing would be at a greater angle(to the earth) & side load the hell out of it. I gots those problems now.

That would be BAD. Ever drive a late model Mustang? - those cars use a strut with about 20 degrees of kingpin angle. That is the main reason those cars handle like pigs, if you "adjust" the spindle back to 10 degrees or so the car handles very well even with the horrible front weight bias.

What about extending the spindle outwards? That would move the wheel outwards, while increasing the clearance with the shock.

Notice the extra bit moving the spindle out.

QUOTE (McMark @ Mar 28 2006, 11:48 PM)

Notice the extra bit moving the spindle out.

RSRs had this done... I even have a picture somewhere. But the shocks had to be custom welded if you changed them out.

As I understand scrub radius, it increases the moment about the knuckle during braking. I agree that's a bad thing if you have compliant bushings (because you get serious toe changes), but what if you have spherical bearings... or needle bearings?

Scrub radius is bad. This is one of the major problems with the strut suspension. When you increase the tire width you have to increase the scrub radius. The more scrub radius you have the harder the car will be to drive and the more effort the driver willl have to put in. Many race cars are going to a zero scrub radius design, but that has its draw backs as well.

Cutting the spindles and extending them is not a good idea. One thing you could do is change the angle of the strut in relation to the spindle. Right now there is 10deg of KPI in the stock strut. You could lay the strut back to 15deg and lessen you scrub radius with wide tires, but then you would run into other issues.

The rules in many classes say you have to keep the strut inside the spring, but you could do something like the sliding strut on jim blakewell's car.

This is what a 964/993 front looks like: the strut is more inclined towards the middle of the car, plus the strut center at hub level is way inward from where the balljoint is. Both of these features allow you to run higher offset rims and larger tires, plus this reduces scrub radius. I think a 993 actually has a slightly negative scrub rad. If you look at a front hub, you may be surprised to see where the strut is connected to the hub, it's behind the hub center. It looks like Porsche did that to allow passage for the front axles on a Carrera 4. The steering arm is also at a different elevation. Anyways, the geometry is very different.

Positive scrub radius doesn't seem to be a huge problem with a track....other than the steering effort.....at least from my experience with wider corners.
On an AX car where you're cranking in a lot of steering lock, it will make the car push like a bitch. At 5 mph in the pits and a lot of lock, I can feel the front tires skipping sideways over shittage laying there. I *think* this translates into push in tight corners....bad push. In larger radius corners
and slaloms, we gots oversteer....a bunch of that also. I'm looking for more balance twixt the 2......it's tough for an old guy to keep track of what to expect.

QUOTE (Bigbohr @ Mar 29 2006, 06:08 AM)

This is what a 964/993 front looks like: the strut is more inclined towards the middle of the car, plus the strut center at hub level is way inward from where the balljoint is. Both of these features allow you to run higher offset rims and larger tires, plus this reduces scrub radius. I think a 993 actually has a slightly negative scrub rad. If you look at a front hub, you may be surprised to see where the strut is connected to the hub, it's behind the hub center. It looks like Porsche did that to allow passage for the front axles on a Carrera 4. The steering arm is also at a different elevation. Anyways, the geometry is very different.

I need pics, damnit.

Ummmm, drugs are bad, umkay.

QUOTE (Brett W @ Mar 29 2006, 05:50 AM)

Scrub radius is bad.  This is one of the major problems with the strut suspension.  When you increase the tire width you have to increase the scrub radius.  The more scrub radius you have the harder the car will be to drive and the more effort the driver willl have to put in.  Many race cars are going to a zero scrub radius design, but that has its draw backs as well.

Brett,

Hook me up with some facts, bro. Steering effort... okay, increased loads into the knuckle... okay. I'll buy that, those things are bad. What else makes it bad?

JP,
I'm not sure I buy "skidding through the pits" due to scrub radius (maybe ackerman), but I'm willing to hear arguments.

This technical stuff is really hard to picture. We need Miles to do a drawing of this stuff. He just has a way of being able to clear things up.

Ok go easy on me guys. This is my first try at understanding this. As I see it and as JP explained it to me, a line drawn through the centerline of the damper in a strut meets the ground under the tire. A line through the center line of the wheel meets the ground and the distance between them is the scrub radius. Oh shit, I'm all screwed up already. Maybe the line goes through the king pin. Help Miles!!

Dave

Picture this.... as the tire patch creates grip, that force acts through the suspension and since your suspension does not directly control that point, a moment is created (offset force creating twist).

The scrub radius is the difference between the center of the tire force and the point at which the force acts in the suspension. Viewed from head on you can imagine a line projected on the ground from the strut.

This isn't as good as a drawing from Miles but, it helped me. Read about Steering axis inclanation, Included angle and Scrub radius

Dave

That's where I stole the drawing... sweet.

BTW... in real life it's rarely the center of the tire due to static camber. The center of pressure of the tire with any camber will be inboard of the center of the tire.

Dave you need this upgrade

Hey Joe

Remember Mile's drawing of a cam. That's some funny shit. I miss him.

Dave

at the risk of going "off topic" yup I remember. I was just looking for that pic. I think it is on my home PC.

I'm a lill bored at work ... so I made this illustration of what a 993 strut looks like. The strut and hub are in black, the A-arm red. The green line connects the top of the strut and the balljoint center. That's the (virtual) pivot when you turn the wheel. This green line shows what the scrub radius is. Looks like I exaggerated that part a bit. The green line shouldn't touch the ground that far outboard.