Lowering the Rear of a 1989 Carrera

[tailwind22]

I am lowering my US spec 89 Carrera to Euro Spec (wheel arch 25.5" front, 25" rear). As you all know the front is a breeze. Moved to the rear. Jacked both sides up and removed the tires. Used a 30" cheater to break loose the two bolts to the immediate right of the torsion bar cover. The newer Carreras have an eccentric bolt that is second to the right. Once the nut was loosened I tried to get a wrench on the back side bolt head to make the adjustment. I do not know what size the bolt head is but I tried a crescent wrench and the space between the rear trailing arm and body is too narrow for either a crescent wrench or plumber's pliars. What have members used to get on that bolt head to adjust this eccentric bolt?

[KFC911]

Been a long time since I lowered mine (and I also did it during a total suspension refresh), but I "think" what you need is a spanner wrench ('bout 1/4" thick) like pictured here:

Pelican Parts - Product Information: PEL-TOL-P242

You can also find them in bicycle shops (as I recall).

Again going from memory, but I think I've got some "bad" news for you also. You won't be able to lower your car using the adjustment as they are shipped from the factory in the lowest position. You're going to need to tear into it and reindex the torsion bars in order to lower the rear. I'm sure an expert will chime in and correct me if I'm wrong, so take what I just posted with a grain of salt...good luck!

[tailwind22]

Thanks for the info. I was hoping to avoid the removal of the trailing arms but looks like no such luck. If anyone knows the size of the eccentric bolt head please let me know as I was having trouble getting the calipers back there for a exact measurement. That way maybe I will only need to buy one spanner.

[Dueller]

IIRC 24 and 36 mm. Like the above poster said, thin wrenches available at any good bicycle shop if you need them right away.

Keep in mind one makes minor adjustments in ride height (< 1 " total) and the other is for toe in/out. And just adjusting ride height will make a slight change in your toe settings in many cases.

And read this article and related links in the aticle before continuing:

http://www.pelicanparts.com/techarticles/101_Projects_Porsche_911/55-Lowering_the_911/55-Lowering_the_911.htm

[tailwind22]

Originally Posted by Dueller

IIRC 24 and 36 mm. Like the above poster said, thin wrenches available at any good bicycle shop if you need them right away.

Keep in mind one makes minor adjustments in ride height (< 1 " total) and the other is for toe in/out. And just adjusting ride height will make a slight change in your toe settings in many cases.

And read this article and related links in the aticle before continuing:

Pelican Technical Article: Lowering the 911 - 911 (1965-89) - 930 Turbo (1975-89)

Thanks. I did read the Pelican article (have the book) and it made it sound like the height could be adjusted down with the eccentric bolt but I cannot confirm without the spanner. Good to know it is 36mm on the backside. Now I can find one and check to see if the eccentric is adjusted all the way down from the factory.

[KFC911]

I believe that article is incorrect. Obviously, if you do reindex the t-bars, adjust them so the spring plate adjustment is in the middle of the range...at least, that's what I did. Good luck, and I hope I'm wrong...but for some reason, if I get involved with something...it AIN'T ever as easy as the books say it is

[ClickClickBoom]

Hey,
I posted a thread, Corner Balance, here some details. If you lower or mess with the tbars, you will need a corner balance. Wrenches are 24/36MM, Snap-On has them, one mortgage payment equilavent, or our host 9.3 Starbucks Lattes equilavent. I guarantee if you lower and don't corner balance you car will have funny handling at best.
eric

[tailwind22]

Originally Posted by ClickClickBoom

Hey,
I posted a thread, Corner Balance, here some details. If you lower or mess with the tbars, you will need a corner balance. Wrenches are 24/36MM, Snap-On has them, one mortgage payment equilavent, or our host 9.3 Starbucks Lattes equilavent. I guarantee if you lower and don't corner balance you car will have funny handling at best.
eric

Agreed. I am due for an alingment and corner balance so that is one of the reasons I decided to lower and do the bump steer (even though Euro spec doesn't require it).

[KFC911]

An "allignment" is essential, but I've never had my car corner balanced. Maybe I got "lucky", but I've never felt the need...she's a "go kart on rails"...stays as true as can be "hands off the wheel" going straight, and simply handles like a dream. I don't track her though...if I did, I'd probably do a CB too...YMMV.

Ps: I totally tore apart my suspension in addition to lowering in the process. Maybe I just got lucky...I dunno.

[Dueller]

I agree that an alignment after lowering is in order, particularly on the front where even relatively slight ride heirght changes will really mes with the toe, caster and camber.

As far as corner weighting, assuming you're within reasonable spec as to correct front to rear ride height aspects, is not so critical/discernible for all but the most talented drivers (of which I am not in that caterory) using their cars at the outer reaches of the car's peformance parameters. Its usually reasonably close/balanced for "normal" street driving.

However it becomes noticeable in track performance situations that even a hack like me can discern. But on ramp shenanigans....nah.

[zippy_gg]

Here is the tool that gas both 24mm and 36mm to be used for the ride height adjustment Pelican Parts - Product Information: PWE-2436RHW

[ChrisBennet]

Originally Posted by KC911

An "allignment" is essential, but I've never had my car corner balanced. Maybe I got "lucky", but I've never felt the need...she's a "go kart on rails"...stays as true as can be "hands off the wheel" going straight, and simply handles like a dream. I don't track her though...if I did, I'd probably do a CB too...YMMV.

Ps: I totally tore apart my suspension in addition to lowering in the process. Maybe I just got lucky...I dunno.

If it's driving fine I wouldn't sweat it. As you suspected, any imbalance would be more apparent at the track. Under braking the "light" front wheel will lockup early.

"Normal" cars don't have much in the way of height adjustment so short of accident, the corner weights can't get out of wack.

*Everything* is adjustable on a 911 suspension so corner weighting is more of a necessity. The factory manuals even has a spec listed for allowable imbalance (20Kg side to side I think for 80's Carreras).

[KFC911]

Originally Posted by zippy_gg

Here is the tool that gas both 24mm and 36mm to be used for the ride height adjustment Pelican Parts - Product Information: PWE-2436RHW

Yes, that's the tool I have...thanks as I didn't see it when I did a search.

Originally Posted by ChrisBennet

If it's driving fine I wouldn't sweat it. As you suspected, any imbalance would be more apparent at the track. Under braking the "light" front wheel will lockup early.

"Normal" cars don't have much in the way of height adjustment so short of accident, the corner weights can't get out of wack.

*Everything* is adjustable on a 911 suspension so corner weighting is more of a necessity. The factory manuals even has a spec listed for allowable imbalance (20Kg side to side I think for 80's Carreras).

I also installed 930 brakes and m/c back then along with a whole bunch of suspension stiffening/upgrades, and since I don't push her to/beyond the limits on the track, I honestly couldn't imagine it being any better. Some day I may search out some scales just to check out my corner weights. I'd be shocked if I didn't just get "lucky" and got them close totally by "not-on-purpose"...sometimes it's better to just be "lucky"

[ClickClickBoom]

The Porsche factory maintenence manual lists the corner balance as necessary after certain maintenence operations. Many don't think it's necessary, Dr P and his staff of engineers will disagree, I will also state that the difference is vast. The manual starts with ride height adjustment as the first order of business. You should know my imbalance was 150 lbs left and right with the ride height exactly 25.5. The real genius of these cars is well beyond a paint job or fast motor, it's the total combination of handling, stopping and acceleration as a sum total. If your corner balance is off by a significant amount, 20 kg (turbo 10kg), you will be outside the manufacturers maintenence standards, braking and cornering abilities will be compromised, how much, I don't know.....
eric

[Dueller]

You guys wh tout corner weight as critical (within reason)...let me give you a real world example. Say you get your car corner weighted pefectly of course sticking 200 lbs in the driver seat to make sure its spot on. Wooohooo.

Now, you pick up a buddy from the airport and he plops 30 lbs of luggage in the back seat and his 175 lb arse in the pasenger seat. That will way skew corner weights. Notice any evil handling on the way home?

I didn't think so.

Now I will say right turns at a track day with a 290 lb student riding shotgun were a hoot...wedge, baby, wedge!

[ClickClickBoom]

Originally Posted by Dueller

You guys wh tout corner weight as critical (within reason)...let me give you a real world example. Say you get your car corner weighted pefectly of course sticking 200 lbs in the driver seat to make sure its spot on. Wooohooo.

Now, you pick up a buddy from the airport and he plops 30 lbs of luggage in the back seat and his 175 lb arse in the pasenger seat. That will way skew corner weights. Notice any evil handling on the way home?

I didn't think so.

The problem lies when the the car is at the wrong ends of the limits and your 350 lb friend sits on the wrong side and an emergency stop is required, ie kid on a bicycle ect comes into play. Don't worry it's America you can do it any way you chose, if you disagree with the OEM designers argue with them, I don't have the engineering knowledge to give you specifics as to why or how it will or won't work, the manual is the manual. I can only provide anecdotal experience, my balanced car performed better.

[Dueller]

Point well taken. Click.

I'm just saying that most undamaged 911 set at normal ride heights are petty close to factoy specs with regard to corner weights. And most people can't sense differences unless waaaay outta whack. But fretting eveytime you align the car to go to the added expense of corner wighting is a waste. But you are correct that a well set up car is a joy. But for that matter, most 911 drives are a joy.

[ChrisBennet]

Originally Posted by Dueller

You guys wh tout corner weight as critical (within reason)...let me give you a real world example. Say you get your car corner weighted pefectly of course sticking 200 lbs in the driver seat to make sure its spot on. Wooohooo.

Now, you pick up a buddy from the airport and he plops 30 lbs of luggage in the back seat and his 175 lb arse in the pasenger seat. That will way skew corner weights. Notice any evil handling on the way home?

I didn't think so.

You airport passenger isn't going to change your corner weights that much.

The thing is, when you change the ride height of a 911 you can massively compromise the corner weights and not even know it. You can't tell by just looking at the car.

Here is how I usually explain corner weights to someone:

Imagine you have a 4 legged chair on a level floor. The top of chair is level as well. Now you put a brick under one of the front legs and one of the rear legs but on the opposite side so the chair is balanced on 2 bricks with 2 legs hanging it the air.

In this example, the "ride height" is higher but the chair is level only now it's supporting all the weight on only 2 legs. On a 911, the suspension will let the tires that are "in the air" droop until they touch the ground so it won't be noticable to the eye.

Not checking corner weights on a 911 that has had it's ride height changed is a bit like not checking tire pressures in stiff walled, low profile tires. "They look good" isn't really the safest practice but as we know, lots of people get away with it.

People do get lucky though. A friend had the suspension completely off the car for a winter project. After he put the car together he came by and we checked his corner weights - they were only 7 lbs off (that's like nothing).

[KFC911]

Originally Posted by ClickClickBoom

... I can only provide anecdotal experience, my balanced car performed better.

With no passenger, a 100 lb SO, or a 225 lb buddy in the passenger seat coupled with either an absolutely full tank vs 1 gallon remaining? If I'm allowed to pick the combination, I bet you're "out of spec" also . Trust me when I say my non-CB car handles like a champ. For all you (or I) know, it might be perfectly balanced also depending upon the proper combination of variables listed above...YMMV. We're nit-picking now on "real world" scenarios...and not talking about a finely setup track beast with a single purpose in mind. I'm done...

[rpenfuyf]

The manual starts with ride height adjustment as the first order of business.