Looking for specs for front and rear alignment for a V8 powered 914 for DE use.
Will be running 7 x 15 front wheels, 8 x 15 rears, with Hankook R tires, 205/50 and 225/50/

Front has 84 Carrera front struts and brakes, new torsion bar bushings, stock torsion bars.
Rear has 200 lb springs...

Guess it depends itf you plan to use car much for street driving or if its dedicated for track use. I believe Hankooks like other radial DOT radials like a good amount of negative camber. I'd start with at least -2.5 front and rear as baseline. Others will have ideas on toe, etc.

Give Rich Walton a call at Smart Racing Products (Jerry Woods) and ask him the best way to proceed.

If you want an expert who makes cars work. No BS and a known winner.

For some street and some track driving I'd go with
Front 1-1.5 degrees negative camber .25 degree total toe
Rear 1.5-2 degrees negative camber .33 degrees toe
Caster almost maxed out
It all depends on how low the car is and how much negative camber you can get. Sometimes you have to grind out the insides of the strut tower holes in the front to get enough negative on one side or both. 914's are a lot easier to get even side to side than 911's are. The fronts of the 911's are all bent and mushy. Our cars have the bulkhead between the strut towers to keep them from moving around.

Click to view attachment


Hi kyracedog:

I've been running and developing my 914V8 for over 5 years now and finally feel I am getting the "handle" on the handling for the car. I run at Willow Springs in SOCAL.

I'm running a 500 HP 383, 930 trans with Quaife, 9.5" wheels front, 11" rear on Hoosier DOT slicks. For stability on-track, I also have poly-graphite bushing in all the suspension arms. So there are a bunch of differences in our cars, BUT there are some things about the design and from my experience I have learned:

First off, with your 200lb springs in the rear, you r spring rate is QUITE SOFT and yoiu will get GREAT traction meaning you will have WAY TOO MUCH understeer. I've been fighting understeer in my car for 4 of the last 5 years and FINALLY got the rear to start to work with 450 lb springs (however, I also have 22mm front torsions bars and a swaybar). BTW: The ride is still fine at 300-350lb springs.

Second: This has been a BIG surprise for me: we MUST keep the car at nearly stock settings....those Porsche guys designed it to run at the standard ride height and lowering the car SCREWS up all the suspension camber arcs.

3rd: CAMBER: I AGREE with starting out at 2.5 degrees of NEGATIVE on all 4 corners when running radial tires. BTW: be sure to pump pressures up in the 34-38 lb range for track running and check the wear. On my car I started out at -3.0 degrees and it seemed right at first. However, as I went stiffer & stiffer, I needed less and am not at -2.0 degrees.
SORRY, but I DISAGREE COMPLETELY with ALL the settings offered by sww914 and will explain why.
4th: Front toe is to your taste. 1/16" is all that you need for a stable car. I tried running TOE-OUT in the front as it is said to help "turn-in response", but it makes the car very nervous and you MUST drive it all the time....no relaxing. Currently, I'm running 0 front-toe and it's fine. If you have rubber in your front suspension, a SMALL amount of toe-in would be a good way to go.

5th: the Rear Suspension: I took bump-steer reading of the rear suspension and was AMAZED what I learned: The Loaded wheel in a corner TOES-IN .200" in 2" of upward travel from ride height!!! At the same time, Unloaded wheel is moving DOWN and TOES-OUT .200" in 2" of travel. I hope you can visualize it: when in a corner, BOTH wheels deflect and point INTO THE CENTER OF THE CORNER. This makes SURE there is no oversteer (remember Ralph Nader & the Corvair). What we end up with is UNDERSTEER!! Thus, I would recommend running NO rear toe-in on our car to start and if the understeer is still BAD, you could go toe-out. I would think 1/8" toe-out would NOT make the car unstable and might get the tail to move a little. A few weeks ago, I was at the Monterey Historics and was talking with a Porsche race shop specialist who was preparing a 914-6 for a fat old guy who couldn't drive. When I brought up what I found about the rear suspension, he just nodded "Yup, I set all 914s at 0 rear toe or toe-out." My car is set a 0 toe now, but after my next track day, if I can't get the right balance with my new rear swaybar, I'm going TOE-OUT!!!

I hope what I have learned THE HARD WAY will allow you a short-cut to a better balanced car!

Best,
Terry

Very nice report Terry. I am sure you are finding what works for your car. I agree with most 90% of what you say. But his car dose not have nearly the grip nor the stiffnig I have seen in person with your wonderful car. I feel he has allot more body flex so his setting will change evan more. But as you say testing is your friend as long as you know what to look & feel for. Are you coming out with TCRA this weekend at Willow??

I don't have stock rear suspension so my toe change is better, so maybe not totally comparable but I run 1/16" toe in in the rear. As for the front, last track day I went to toe out for the first time and can say I am much happier with toe out than toe in... I run 1/8" toe out on the front (RSR front struts but essentially stockish configuration). Car was pretty stable IMO up to 145mph in the front straight.

If your car has stock suspension bushings and so forth, those numbers would certainly change as you get dynamic changes to your settings, especially toe. I would run slight 1/16" toe out front and maybe a bit more toe in in the rear like 3/16".

The key is during bumps and so forth you don't want to have a situation where the tires pass thru zero from in to out, or out to in. So, if you have toe out on the front, you want to make sure if you go thru a dip and the front compresses that the settings don't go from toe out to toe in as this will make the car squirrelly and a bear to drive.

Hi Leamon:

Of course you are right: Grip is very relative. I was trying to say that kyracedog's issue is NOT total grip but BALANCE. With SOFT springs, one gets very good mechanical grip. Even at 350 lb springs, I still soft enough to have so much rear grip that all I got was understeer! When I stepped up to 450 lbs springs, I FINALLY got the balance I was seeking and the car was a joy to drive.
However, the negative side affect was that I could not put the power down and had BAD wheelspin coming off corners.

While chassis flex is not a good thing, I'm afraid I don't understand how flex should have any affect on static chassis settings. Again, since he is running modest size tires, he will NOT get generating the side loads high enough to DEFLECT the rear suspension mounting points. Since I'm running 315/35-17 in the rear, I have had to brace ALL the rear suspension mounting points. Again,
Porsche designed the car to run a 165 radial....ONLY!!! However, as you said, it's all a Best Guess until it is track tested.

Thanks for your invite to the TCRA events....I've been running for a good number of years with the Speed Trial USA group as they are great bunch of guys. Maybe you can help me understand TCRA: are the events open track practice days or are the group racing events? At this point, my car is just not developed to the point that I would care to enter a race. After my next outing, I hope to reach my goal.

Best,
Terry

Hey Tim,

How's your car coming? It is a truly amazing tube frame race car you built , especially the 4-link rear suspension you designed: I'm inspired by your work.

I appreciate your feedback on the front toe-out, I'm tempted to try a bit more front toe-out on my car.....but FIRST I've got to balance out the understeer the QUAIFE created!!

I'm surprised that you are advising the rear toe-in as it seems to me the car would start at 3/16" toe-in (static) and then have it INCREASE as the car rolled into a corner. From what I measured, the suspension only went toe-in from static ride height as the arm went up.

Given the limitations of the stock suspension design, I feel we will just have to live with bump-caused changes of toe-in to toe-out. Actually, I have never felt anything funny from this design issue....but you're the engineer, maybe there's something I'm missing here. Please feel free to let me know what I don't understand.

Hey, I'm waiting for your next track day report. Is your LSD fixed? I think my new rear bar will get mine where I need it to be....I'll let you know.

Best,
Terry

got the sheared off CV bolts out last weekend and got lucky in that I got them out with little trouble, no left-hand drills or other nightmare expectations I had. I designed an adapter for the Mendeola to 930 CVs that I think will work really well to cure a lot of issues in the interface, so I bought some hardware on Friday to verify some dimensions, etc and now just need to order steel. The machinist at work said if a Sat opens up for him he could sneak in and CNC them out for me... of course I will pay him cash for his time but he should give me a good deal and CNC some nice parts.

I need to order a new set of CVs so forth, so I am in no hurry.

Back on topic and addressing the rear toe out stuff, I know the rear toes in pretty aggressively and my short link suspension also has a serious toe curve should I bump more than 2"... that said it is my understanding that going from toe out to toe in or vice-versa is bad as passing thru zero will cause weird handling characteristics. NOW, that being said I have never tried it to confirm it as I figure others have proven it bad.

What might this cause? Maybe something you determine to be totally manageable such as tendency to oversteer on turn in, then as the suspension compresses it goes to toe in and understeer at the apex and out. That situation may be one where the car turns well then helps compensate for it, who knows?

That is what is meant by weird handling in that the car can go from one tendency (oversteer) to the opposite (understeer) which might even turn into a "snap" situation. At minimum you never know exactly when the car will go from over to under tendency in a given turn, so you go into the turn and wonder when the change might happen, try to anticipate it (pretty much wasted energy), etc. So you go in slight oversteer, start to compensate turning into it, then the car toes in the rear causing understeer you just turned into and you drive it right off the track anyway...

NOW, if you are toed out so much that during compression you never toe in on the track (not talking toe curve at 3" of bump but what you really get on the track) then the car will always act the same thru the turn - desire to oversteer. I have no specific issue with that, but I suspect with soft suspension like this guy has if you go with slight toe out, you will transfer thru zero to toe in and have a hard to manage car in the turns. If you can toe the rear out enough to not do that and also not wear the inside edge off the tire, then I say it is worth a try.

For the front, go toe out, I promise it is mo' betta. I had resisted the urge to try it based on a myth of stability in straights, and given how fast my car is speed wise in the straights I was scared to try it but can assure you I was really underwhelmed in the straights, which is a good thing I went to this with the addition of the LSD and the crazy understeer I have fought. For reference I have 350 lb/in front springs with a Tarrett bar and 550 lb/in rears no bar and had slight understeer still but was tuning it out and had more room to go soft on the bar before shearing the CV off, so I think I am getting there. With the open diff 930 at WSIR back in the day I ran 350lb/in fronts with the Tarret and 450 lb/in rears for perfect balance, so it appears I needed to go up 100lb/in to fight the LSD.

edit - oh yeah, the rear is 5-link, not four. Each side has five links to constraint 5 of 6 degrees of freedom. The sixth degree is constrained by the coil-over. So to be clear, my rear has 10 links in it total, 5 per side

Hey Tim,

Glad to hear you are moving forward with the shearing of your CV bolts...you should be back on track soon! I was thinking, with all the problems ALL that HP is causing you, it would be way cheaper to just pull a spark plug lead -kidding-

I know what you mean about NOT being in a hurry to dump MORE $$ into the car: I just had to buy a new set of Koni Sport shocks for my front end. I surprised they DIED with so few miles, albeit, most were on-track. I test drove the car around my town today and in an S-turn at 80, the car was VERY tail happy....as in it could have happily swapped ends if I weren't being very smooth with it. So the good news: it appears my homemade rear bar CAN correct the understeer, now comes the fine tuning: bar and rear shocks (2-ways). I aiming at an early October Saturday at Buttonwillow and believe Andy will be coming along (my ACE RACE Engineer!).

Sorry, for UNDERstating your links! No disrespect intended: I just look at any double A-arm suspension and assume it's only 4-link. I know how much engineering you put into the design in creating a 914 with a superior and STABLE rear suspension!! Would that I could do the same!!

Now our discussion: I see your point about the handling changing as the car rolls into the corner. My personal "seat of the pants" feeling is that any of the transition stuff happens quickly DURING the transition phase and as a driver, I only feel what the car is doing once it SETS into the corner. But as you said WHO KNOWS. I'm sure the guys who designed the car and could explain it ALL, have LONG since retired from Porsche.
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FYI: I wanted be sure that you all know my car is a STREET CAR that I drive to the track and back home (hopefully)......so I am thinking in terms of how most 914 guys drive their cars. My 0-toe steering was very nervous today on bumpy, patch-repaired pavement while racetracks are mostly VERY SMOOTH and one can get away with "racing" adjustments. They are clearly 2 different worlds.

Best,
Terry

I didn't see any disrespect to stating 4 links, I just wanted things to be clear for you and everyone as there is such a thing as 4-link rear suspension - it is 4 total links attached to a straight axle, then technically there is one additional link (Watts link is two acting as one or Panhard bar) to stabilize location left to right of the axle, but still referred to as a 4-link.

Technically a dual A is also 5 links per side as you have 4 mount points for the two As and then a link of some sort that controls toe, like your steering arms.

Tim:

Gotcha': In a technical forum, I was being sloppy with my terminology.

Best,
Terry

Hey guys!!

One addditional aspect to the 914 trailing arm rear that kyracedog ought to consider, is ride height. Changing the ride height (most tend to lower the rear) will have an affect on when, through the trailing arm's travel (mostly on droop), he will have toe gain, transition, and how much.

Terry, I think Tim's rear suspension is quite a departure from the 914 trailing arm design such that his static toe settings may require something quite different. The dynamics are of course different too.

Tim, so you tried some toe out in the front? Good! Did it help only durring turn-in, or elsewhere as well? Just keep and eye on wear on the insides of the front tires. Oh, you may find that toe out helps make the car a little easier to save when opposite lock is required....of course you never go there :-)

Andys

I didn't get a lot of track time before trashing the CV so can't say I noticed anything amazingly different with the toe out other than turning in better... 'course I didn't do my normal scientific method change one thing to know overall effect and changed the rear spring rate significantly as well, so hard to say how much effect the toe out had, but overall car was much better in terms of understeer.

One thing that I did notice that would be specific to the toe v. spring rate is in the front stretch it was paved in 3 strips and you can actually see the strips, meaning there is a slight ridge from one to the next - the car wanted to follow those lines, which are far from straight, so I had to be certain to get the car off of the seams so it wasn't wandering at 140mph. I didn't have that issue with the toe-in before, so that is a potential issue but since I DE the car v. W2W I am not worried. If I needed to be able to put the car anywhere at anytime to get a pass, then I wouldn't like that characteristic, but for open track days and such it isn't an issue so much.

Tim,

My description of toe out is that it makes the car feel like it wants to turn. Should you decide toe out helps your set up, you won't even notice it after a bit of time behind the wheel. Did you ever add a rear sway bar? Wouldn't take much bar to make a difference and give you a bit more adjustability. Might also give you an opportunity to explore softer rear springs.

Let's see, wide tires, stiff springs and it wants to follow the road seams.......gee, what a surprise ;-) JK!

Andys

Andy & Tim,

YES! I was looking at a true 5-link suspenion on the net and it would take an engineer with CAD to figure out the camber & toe changes as it move through its full travel arc. I would LOVE to see any graphing Tim has on his design.

I agree with Andy's "big picture" view on front toe-out. If a certain amount is comfortable, fine. But if the car just become a constant battle to keep straight, time to move the toe in a bit. I originally tried about 1/8" toe-out, but since I have to DRIVE the car to the track and back, it was just too much work on bumpy roads. At 0 toe, its fine.

Tim: I'd enjoy seeing your your rear bar design! The only place I could "reasonably" mount mine was on the back side of my engine support tube.
The good news: after yesterday's successful test, I'm really pumped with the cars handling! Thanks Andy....with out your nudging, I never would have done it.

Terry

no rear bar yet, only a front bar.

Hey Tim:

The only question I have is Do you NEED a rear bar to correct your LSD understeer?

To over come the Quaife-induced understeer, I knew I needed MORE rear spring rate. I went with the rear bar due to a push from ANDY and when I realized I needed an easy adjustment to the rear wheel rate, in small increments, at the track!

I really had to scratch my head to find a place to mount the rear bar, but at this point feel I've got my solution. I won'd know for sure until my next track day.

In your case, you could increase the rear springs rate or use the tube frame to create a nice swaybar attachment and easy adjustment.....

Whaddya' think? Andy reminded me of the extra bonus that a swaybar adds its stifness in ROLL mode.

Terry

yeah, need to add a rear roll bar now due to the LSD. Without it you obviously wouldn't want it as it will lift the drive wheel when it is the inside wheel and why I didn't have one before, but certainly necessary going forward. Project for the winter maybe, or sometime next year... just got the steel yesterday for my adapters and found out today the machinist at work can no longer do stuff on the weekends! So he is checking with his other job if they will let him there, or else I will have to pay a machine shop to do the work, so for now that is the primary project.