My 914 goes to the shop next week for alignment: 1.5 to 2 degrees neg camber front, 2 to 2.5 neg rear with 1/16" toe-out front, 1/16" toe-in rear. Tires are Hoosier A3S03's.

I have found a few posts that seem to indicate that when the A-arms and trailing arms are parallel to the ground, you have maximized your cars height. Is this in fact, correct?

If so, why is this level preferred? If you go below this height is suspension geometry adversely effected? How much wheel travel is left at this point?

Joseph
'75 914 2.0L AX bound

I dont think yo have maximized the height when the arms are parrallel, youve minimized it, meaning it as low as you want it to go. Does that make sense, or did I misread your post? Beer in my gut...

Answers will very...but. I feel its important because of bumpsteer. Most people dont/cant correct for the bumpsteer by using anything more than the typical rack spacers. I have personally found the best bump with store bought spacers is having the control arms parrallel to the ground. Anything beyond that and you have to start experimenting with stacked washers or spend the big bucks and buy the bump kits that adjust out at the steering arm.


B

Chris,
Sorry. Poor choice of words (brainfart typo). I should have said "Optimized" (as in optimized handling). Think I'll go have a beer.
Joseph

I knew what you meant.


B

Sorry, no answer. Just extending the question a bit. I hope someone with experience and figures can jump in.

If you observe the geometry of the front suspension you will note that there is camber change throughout the range of suspension movement, with the greatest degree of negative camber when the lower conrtol arms are horizontal. As the suspension moves further from this point in either direction the camber goes further possitive.

My problem with the whole idea of arms-level-at-rest is that means you have maximum negative camber when everything is at rest. When you load up a wheel it will compress the suspension and reduce negative camber (I'm ignoring body roll - I'm just talking about the strut angle relative to the body). Does that make sense? This is why I'd really like some raised-spindle struts like the Bilstein RSR's. Using a raised spindle to lower the car and then having the static possition of the control arms below level - the amount of negative camber increases as the wheel is loaded up - at least until the travel passes horizontal - but with the right spring/shock combo you can probably keep from passing that point under most conditions. Is this making any sense?

If you start with the control arms level at rest then you are losing more negative camber with each additional pound of weight transfered to that wheel which is just the opposite of what you want. So you throw the car into a corner and you start losing negative camber as the strut compresses and the control arm moves past horizontal. Add to that the possitive camber being induced by body roll. Double wammy. You really want the suspension geometry to increase negative camber as load increases to counteract the possitive camber being induced by body roll.

Now maybe the camber you conserve due to reduced body roll from lowering the car is of greater benefit than the camber lost by having the control arms "going past the half-way point" under load. Maybe that's why people are advocating the "arms at horizontal" spec. I don't know. Ok Brad, speak up. Or anyone else for that matter.

-Ben

Raised spindle is the way to go.. but its very very difficult to do this with a 914 strut or early 911 strut. The Koni and Bilsteins are the easiest to raise. You have the idea nailed down. Now. With 23mm torsion bars and a "race shocks" there wont be much suspension travel. This is a inherit design flaw in the rear and front of 914's. You deal with it the best you can and try to limit the amount of change during travel.

B

Limiting the camber change is one of the reasons for putting the A-arms parallel to the pavement. The smallest changes in camber occur when the A-arm movement is near where the arm is horizontal. Ditto the changes in toe, I believe. The suspension seems to be in the heart of its working range at that point.

I actually prefer a little bit of droop in the at-rest position of the A-arms. The tire that is having load taken off of it will have more camber/toe change that way, but the one that is being loaded will have less. Which I think outweighs the larger change on the other side. But how much "a little bit of droop" is depends on a whoooooooole lotta things. Spring rates, driving style, the pavement you're driving on, and on and on.

I'm not nearly enough driver for that to make a real difference, so I just eyeball it...

--DD

Joseph; I'm curious about the numbers you posted because I had my car aligned yesterday by a Porsche only mechanic. He set it at: Front 0 toe and -2 camber, Rear 1/16" toe-in and -1.3 camber. He said that was all the neg. camber he could get in the rear. These settings are quite a bit different than your going for. Did my guy screw up or is each car going to be different?

Each car is going to be different. Bent arms tweaked tubs... you name it.

I just barely got 1.7 in the right rear of the last 914 I built while the left rear had NO problem getting 2.0


B

Don't forget, the more you lower the rear ride height the more negative camber you get, so if your car sits taller you'll have less negative camber you can dial in. (use adjustable spring plates to change rear ride height)

-Ben

He,he.....this is great stuff.

Prior to my mods, bout -.25 was all that was available at the front. Dropping the ride height bout an inch gave me -.9 deg.

At the rear, I had about the same as the front. Dropping the ride height .75 and pulling all the shims(6mm worth) gave me -4......oops
4mm went back in and now there is about -2.2.

The front is about ready to re-check....dunno there, yet. Shooting for -2+.

Off hand, I'd say there is a "bit" of variation from car to car (insert tounge in cheek smiley here).

Drew:
Stick your haid under the back of the car and see if there are any shims in there (above the outter suspension mount). If there are some on both sides
I'd find a new alignment guy. If there are none, I'd drop the ride height a bit, .5 inch or so.

Drew,
My settings are the initial settings I hope to be able to do to set my car up for autocrossing. 2.5 degrees negative camber should suit the tires I am using (they like a lot of camber). However these would not be great street settings if that is what you're looking for (would result in poor tire wear and car wandering over bumps in a straight line). As Brad has pointed out, each car will have possible restrictions for various chassis/component reasons.

It seems that usually you will want more neg. camber in the rear than the front. You have just the opposite. If you can only obtain 1.3 in the back, maybe you should consider setting the front at 1.3 also. You would certainly have better street tire wear. It could also lessen a tendancy for your car to oversteer. But others may have other opinions.

Joseph
'75 914 2.0L AX bound

I have NEVER set a car up with more negative in the rear than the front.


Tidbit of info for people reading this thread:

Newbies in first time AutoX or Time Trial scenerio's do NOT need a ton of negative camber for your first alignment. You will not use the tires to their full potential no matter how Ricky Racer you think you are. I see this all the time, where an alignment shop sets your car on FULL KILL and you THINK your driving it 9/10ths and the first tire temps you do show inside (210) middle (180) outside (140) Your not using the whole tire and wont until you learn to drive.

My point. Start conservative and save your tires. It wont be until AutoX or Time Trial number 4-5 before aggressive alignments will help you out and you will only know when its time by doing the tire temps. When you start seeing outside temps higher than inside (add more negative camber)

B

J.P.; No shims were used in the rear. He corner balanced the car so I assume he balanced the need for good corner balance and more negative camber.

Joseph; I'm setting the car up for track only. It really only gets driven on the street to and from the shop.

Brad; Thanks for the info, I'm not Ricky Racer yet but I'm turning respectable times and think I get the tires up to temp.

Speaking of tire temps...
We've talked about cheap flares, cheap corner weights, cheap other stuff. How about a cheap pyrometer? I for one am tired of wondering about tire temps. Anybody got a killer cheap & effective trick? (please don't say shoe pollish)

-Ben

do some searching on Pelican
there's an article on how to make your own, using a regular voltage/auto meter, a big nail a bic pen and a cheap part from radio shack...

cheers,

Jeroen

C'mon Jeroen!

a bic pen?

It's getting deep here guys!

Didn't you ever watch McGeyver? I think he'd use some bubblegum too.

hey, he's asking for cheap and if it works... who cares
I guess you could always upgrade to a fountain pen later

cheers,

jeroen

DID SOMEONE SAY CHEAP????


''You will need a thermistor (Radio Shack part number 271-110 $3.39), a digital multimeter (any electronics store, $30.00 and up), an old ballpoint pen, some electrical tape, a couple of nails or pieces of coat hanger and a 24 inch (or so) length of insulated two conductor wire. ''

Full article at:
http://www.rennsport.ca/articles/technical.../Rsr%20pyro.htm

Marc-André

rub it in a-hole!

Jeroen & Marc-André,
Thanks for the info! You guys rock. I had no idea it would be so simple to build a pyrometer. I just assumed that since they were so expensive that they must be complex. I'm sure this isn't as advanced as an off-the-shelf unit but I'm sure it'll work better than my hand.

While I'm at it I'll tell you both that I appreciate your do-it-yourself personalities and have been admiring your projects for some time. Keep it up. One of the reasons I've been hanging out here is to be around that sort of attitude more.

-Ben

Drew,

I hope you didnt think the "Ricky Racer" was aimed at you. It was a general term that I used. A lot of the SoCal shops are well known for sending their customers out on what I consider unsafe alignments. What works good for the fastest guy at the track doesnt work for the guy just starting out. I have seen cars with a ton of negative camber go faster with less because they where not using all of the tire. They where basing their alignments on "what everybody else is running" instead of doing their own data gathering on the owner/driver of given car. This happened last year with some friends of mine at the PCA club race at Fontana. They took a driver there in a GT3 Carrera cup car with 4deg of negative camber. I walked up and the driver felt uncomfortable in the car. It pushed.. it was loose. He wast happy. I walked up to say hello to them and after saying hello... I looked at the car they had there and said "too much negative camber". They said "that is what so and so is running" I said your driver isnt PRO, pull 2 degrees out of the left front and pull 1 degree out of the right front (all left hand track) and pull 1.5 out of each rear wheel. Very next session after 2 laps he was 4 seconds quicker and screaming into his headset about how well the car felt. The car didnt go faster... he felt more comfortable in the car going fast.

My 02

B

Ben:

Caster.

When the car is going straight ahead the camber would decrease as the suspension compressed....under the conditions you describe....who cares? No harm, no foul.

As the tire is turned at an angle....during cornering, caster comes into play. Camber loss is negated by caster. I agree that ideally the A arm should never go above horizontal, but all is not lost should that happen.

Our little shitboxes have loads of caster built in......unlike other shitboxes.The stock
caster spec is 6 deg.....the axles lead the top strut mount by that much. Were one able to turn the tire 90 deg....thank God we can't....you would get 6 deg negative camber on the outside tire and 6 deg positive on the inside tire.

At max turn, my eyeball says 20 deg deflection from straight on the outside tire. That would be about -2 deg camber...if my in the head math serves. + 2 on the inside tire.....but it's not going to be compressed....ta da. This works regardless of body roll, but we Ricky Racers are controlling the shit outta that, nohow.

Brad,
"I have NEVER set a car up with more negative in the rear than the front."

Are you referring to track/race cars only, are does this include AX for you?

I have no experience with higher speeds of track/race, but do have some experience in AX (and still learning). It's my understanding that what can work for an AX can be way too loose for track speeds. That being said, I know many autocrossers that run more negative camber in back than front.

Would like to hear your views.

Joseph

Brad; You can call me Ricky Racer anytime! Just keep the good info coming for us "less experienced types." We need a smiley with a leather helmet strap flapping in the wind.