Sway bar question, need some help!
 

Hello everyone,
Just purchased a set of sway bars for an early car. I was told the front bar was a 19mm (through body) and the rear an 18mm. When I opened the box the rear appeared much larger in diameter than the front. The front is stamped 15 on the end, the rear is stamped 18. So just out of curriousity I placed my calipers on the bars and the front measures 19mm but the rear 23mm. The rear is stamped 911 701 07 and appears to be a 18mm based off what I can find from the part number, but the front I am guessing is a 15 based on what is stamped. The person I purchased them from thinks the front is a 19 based on the caliper measurement. Any help would be great. Thanks

If they're Porsche bars, I don't believe they made a 19. They made a fairly rare 18 that came in the first year 930's

The stampings are usually correct on a factory bar. Maybe they've been powdercoated.

Edit: where did you put the caliper? Don't measure the ends, measure the body.

I think you are talking about torsion bars, not swaybars.

Factory fronts are 18.8mm. Rears were 23.x in some years.

Through body torsion bars? :D

911-333-701-07 is an 18mm rear anti-roll bar for a 911SC.

Scott

Yes they are sway bars not torsion bars. The measurement I took was from the body of each bar not the ends. The front and rear are factory. The front is stamped on the end 15. There is one on eBay for sale as a 15mm with the same stamp. I have a feeling the diameter measurement has non relation to the actual size.

The diameter is the size. That is the measure of their spring rate. Are your calipers calibrated? Are you holding them perpendicular to the bar?

The only other thing I could think of would be if they are hollow, then they would have a larger diameter than their equivalent spring rate in a solid bar.

Yup, that is how the early cars were and how most of the later aftermarket bars work. There is a triangular boss on either side of the front inner fender behind the strut on all cars up to 1989 for this, just no hole for the bar. It runs through the body behind the fuel tank. There are lever arms that mount to the end of the bars and attach to drop links that connect to the lower control arms (read A-Arms).

The pictures in this tech article provide more details...

http://www.pelicanparts.com/techarticles/914_front_swaybar/914_front_swaybar.htm

Hey guys, I am not sure if I am being clear. Yes the front is a through body sway bay, factory bar, not hollow. I am fully aware of how they mount and what they look like. I am only trying to clarify if the stamp on the end of the bar has any relation to its size. The front bar has a 15 stamped on the end, but when you measure the "body" with a caliper, it is 19mm. I am just trying to confirm if the bar is a 19mm or a 15mm. My understanding is that they never made a "factory" front through body sway bar in a 19mm. The reason I think it is a 15mm is because the rear bar I have has a part number on it that decodes as a 18mm bar but when you measure the body of it, it measures 23mm, which leads me to believe the diameter has no relation to the bar size. I hope I am being clear now. Please note this is regarding factory sway bars not torsion bars or hollow sway bars. Thanks guys

If the bar ODs are 19 and 23mm respectively, that is what they are. As for the numbers stamped differently, how about "stamped incorrectly"?

Sherwood

ok, lets say the bars are stamped incorrectly, the rear has been confirmed 18mm carrera bar even though the measured diameter is 23mm. Next question would be, did porsche ever make a 19mm through body front sway bar?

unclebilly,

You missed the point. There are no such things as through the body torsion bars.....

Scott

I think you are confusing some folks with your terminology.

Concerning the front through the body sway bar... this is what Porsche offered:

Factory stamped 13mm. This measures 13mm diameter.
Factory stamped 15mm. This measures 15mm diameter.
Factory stamped 16mm. This measures 16mm diameter.
Factory stamped 18mm. This measures 18mm diameter.

The factory stampings on the bar ends identify the diameter of the bar.
Just because it looks like a factory bar does not necessarily mean it is a factory bar.

Other aftermarket companies have produced a solid through the body sway bar that is a 19mm. It measures 19mm diameter. I actually have one.

A picture of the stamping would help. The number font used is distinctive.

To be most clear and accurate, a sway bar (anti-sway bar) is technically a torsion bar (a bar in torsion - by design). For the purposes of Porsche-discussion, the term "torsion bar" is generally used to describe the type of spring in the suspension system.

S

Thanks for the response, that make a little more sense. I will post some pics tonight for clarification. Maybe the bar is an aftermarket and stamped 15 for what ever reason.
Do the rear bars measure the same, I know the rear bar I have is factory, it is stamped 911-333-701-07 and just above that is 18. When I decoded the rear bar, it comes back as a 1979 SC 18mm rear sway bar. When I put my calipers on the body it measures 23mm. This is why I am getting so confused! I will post some pics when I get home from work tonight so you guys know what I am talking about.

As Flieger stated "are your calipers calibrated?" Are you using electronic or mechanical non electronic? If so maybe try another set for A/B comparison. By your measurements it appears the readings are getting more inaccurate the larger diameter you measure, 4mm larger front and 5mm rear. Just a thought.

David

Let's get technical and very clear. No one calls an anti-roll bar a torsion bar because it is not one. Yes, the anti-roll bar is a torsion spring, but that does not make it a torsion bar.

Calling an anti-roll bar a torsion bar because both are torsion springs is like calling a Doberman a German Shepard Dog because both are dogs.

Scott

OP, if I may suggest, post a pics of your parts so some of us less enlightened can get over the terminology and actually try to assist your concerns.

A ruler next to the part would help immensely.

Maybe this will help:
http://img.photobucket.com/albums/v5...OA5OG/PAG4.jpg
http://img.photobucket.com/albums/v5...OA5OG/PAG3.jpg
http://img.photobucket.com/albums/v5...OA5OG/PAG2.jpg
http://img.photobucket.com/albums/v5...OA5OG/PAG1.jpg
http://img.photobucket.com/albums/v5...OA5OG/PAG5.jpg
So OP, which is it?

http://img.photobucket.com/albums/v5...026-WA0002.jpg

You guys are killing me. I am going to squash the "torsion bar" argument now. I am not talking about torsion bars, I am talking about sway bars or anti-roll bars, not torsion bars.
I will post pics tonight. I have both digital and mechanical calipers and both read the same.
Please keep in mind that I am only trying to rule out if the diameter of the bar is in fact the size of the bar, then why does the rear "factory" bar decode as an 18mm but measures 23mm?