30mm sway-a-way's

[greg f]

Anyone on this list use 30mm hollow Sway-away / Weltmeister rear torsion bars to fit a 944? Performance products has been out of these for weeks and seem to be reluctant to order more. Sway-a-way make these bars and requires Performance Products to order in bulk. I was hoping that a few people on this list might call them and try to order some, then voice their dissapointment that they are not available. ( just trying to grease the corporate wheels of PP a bit) Greg F

[944-Spec#94]

I have the 30mm solid sway-a-ways.

 

Does Paragon Products have 30 mm hollow's?

 

Last time I talked to Jason he said they could get me up to 32 to 33 mm in hollow. It would be semi-custom job but possible.

 

Of course I did not since 30 mm are the maxium that are legal.

 

For those that want to know the reason 30 mm are the max that are allowed is that those are largest commonly avalible size anything beyond 30 mm effective goes in to semi-custom jobs and we wanted to avoid that.

 

Edit....

Yes paragon has them for sale. I don't know if they are in stock however.

http://www.paragon-products.com/product_p/welt_tt-5200.htm

[Tim Comeau]

Are the 30 mm available now? You aren't going to save that much weight with the hollows.........

[greg f]

You must be kidding, they are quite a bit lighter in weight. I don't even care that much about the weight, it is the reduction of reaction mass in the center of the bar I am after. They have a greater range of useful motion than the solids and react 30% faster. I didn't think that anyone bought the solids anymore. Greg F

[Tim Comeau]

Maybe we have something to learn here?....................

If they react quicker, is it because they are less stiff?

Reaction time? The 30mm solids have an effective spring rate of about 330 lbs?

How can you have a faster spring that is just as stiff without being longer or progressive?

I'm all ears...........

[greg f]

If you look at the catalog you will notice that a hollow 30mm torsion bar is sold as a 30mm, but the physical measurement is something like 31.5mm. ( I am in Daytona right now and don't have one to measure) They are sold as 30mm to avoid confusion as the rate is identical to a 30mm solid. It is easy to understand the reaction speed if you account for the force required to twist the bar as it nears the center of the material. Sway-a-way bars are induction hardened ( like the O.E. parts). This is where very high voltage is passed through the material to create a hard surface. The longer it is subjected to the electricity, the deeper the hardening effect. The center of the bar more closely resembles the base material of the torsion bar than the relatively springy surface. The mild steel center resists both quick direction changes and limits the total twist of the bar. You can expect roughly 10 degrees more travel availability from the hollows. The other way torsion bars are made is to machine them from 4130 or similar material and heat treat the finished part. The rejection rate for this type is higher, but the finished product can be pretty good.

A replacement coil spring for the rear of a 944 is another example of how the spring could be lighter, smaller yet the same stiffness. A 330lb by 5" by 2.25" coil spring would weigh 25% as much as a hollow torsion bar and more like 50% lighter than a solid. The coil spring has a large mechanical advantage when placed over the shock compared to the torsion bar that acts through the radius arm ( lever arm). Mitchell has some software that allows you to calculate the effective force of a hollow or solid torsion bar, but he doesn't really address the ability of a hollow to more accurately follow the surface of the road. Ask someone that has changed from solids to hollows on a streetable car. They will tell you it both handles better and is not as harsh over bumps. Greg F

[PeanutinCA]

If you look at the catalog you will notice that a hollow 30mm torsion bar is sold as a 30mm, but the physical measurement is something like 31.5mm.

 

Sorry to be a pain in the a$$....

 

14.1.3 Springs

Any rate is permissible in the factory original location only. Coilover systems are not allowed in the rear. Any torsion bar size approved up to 30mm.

[Packfill]

You go Dilly!!

[944-Spec#94]

Guys,

I hate to burst you bubble, but the rules state Size 30 mm max. They do not state max diameter of 30 mm. Subtle I know, but that important.

 

Remember the a 30 mm solid and 30 mm hollow have the same effective spring rate. That is why they are both 30 mm "size" It is true that that the hollow bar has a real diameter of 31.5 mm. The "size" is still 30 mm.

 

 

It was a couple years ago that I asked that we limit t-bars to 30 mm. The intent was an effective rate of 30 mm max. I/we knew hollow bars existied back then. At the time they were not seed as "better" than solid bars. Even now Greg talks about them being theoretically better, but we don't care about ride comfort.

 

So hollow bars are legal and I would argue legal to a 30 mm effective rate. I for one have solid bars and have no intention of changing to hollows. It might make difference, but not one that is worth much to me.

 

If you want to get nick picky they in the next round of rule changes we change "size" to "effective rate".

[PeanutinCA]

Just posting what I see. Care factor about it zero. For everything else, there's Mastercard.

 

P.Dilly.