Torsion bar upgrades for 73 911 E

[cmcfaul]

What is the optimal trosion bar size or a 73 911 E.

I DE the car a couple times a year and drive it most days to work.

I went to 16 inch rims and raised the center of gravity the car. Now it handles like a pig. I increased the size of the sway bars a MM many years ago but still feel like I am driving a Cadi compared to the way it handles when it is just a couple inches off the ground.

I want to keep the car as low as possible and the 205 16 55,s are very close to the fender in the back (the way I like it). when I go to stiffer torsion bars how can I compensate to keep the car as low as possible (how much do I change the angle based on the extra stiffness of the torsion bars).

I have been told that I raise a front wheel considerable off the ground in tight corners at DE. Again another reason for wanting to stiffen things up a bit.

Many thanks

Chris
73 911 E

[Jim Richards]

Chris, I have 21/26 t-bars on my 73E and I think they're too soft, especially when mated to Bilstien HD/Sport shocks. I'm going to upgrade to 22/28 over the winter. FYI, I drive on the street and DE a fair amount (although I'm still a rookie).

[cmcfaul]

I also have the Bilstein Sport shocks

[IROC]

Beautiful car. I have 22/29mm torsions in a 2350lb car (probably similar weight to your's?) and I would say that they are on the stiff side unless you really plan on tracking the car quite a bit.

If you want to lean more towards a "track" set-up and less towards the street, I would recommend 22/28 and if you're looking for something more comfortable on the street, but stiffer than the factory saw fit to provide, then maybe 21/27.

Be careful of going too stiff in the front as the relatively low amount of weight at that end of the car will really make big bars noticeable.

Good luck,

Mike

[thrown_hammer]

My car has the Bilstien sports with 22/28MM torsion bars. Mostly street and some DE's with a few Auto-X's.

[racemor]

I'm running 21/27 with Bilstien Heavy Duty all around. I took the car to a DE a few weeks ago and was pretty happy with it. It is still primarily a street/mountain run car so I would not go any stiffer. Our roads are not maintained all that well where I live, something to consider. Also, I made the switch to Elephant's polybronze bearings to help with response without going any higher on the tbars. Chuck recommended the HD shocks rather than the Sports based on my torsion bar size.

[Porsche Head]

racemor, if you had a choice would you have upgraded the bars or do you think it's a good compromise as it is now?

I hear your comments on the ride quality, for me it will be a lot of runs down the Pacific Coast HWY and such more than autocross.

[jluetjen]

Is that picture before or after you raised the car? It looks pretty low to me. As far as raising the inside wheel when cornering hard, that's normal. Adding 16 inch wheels may have raised your center of gravity some (by 1/2 an inch assuming that you're using the same tire size and profile), but I suspect that by switching from a 60 series tire to a 55 that you're pretty close to back to where you started.

Starting at the top -- what is the "optimal" T-bar size? That depends on a lot of things. If the car were stock, I'd say the factory bars or else the factory options. Guys like Vic Elfort who did the test driving for the factory in this era really knew what they were doing and the factory settings are pretty good.

Now your car is lowered and has additional grip from larger tires, so the "optimal" will be different. BTW, what is the ride-height for your car front and rear measured at the wheel wells? Running your car lowered as you have also puts you in something of a box since you may have lowered the roll center (especially in the front) to such a degree that the geometry isn't working like it was supposed to. If you really want to keep the car this low and return the suspension back to the range that it was designed for, you'll need to convert the front struts to "RSR" style with the raised spindle. You should also update the rear trailing arm mounts to raise the rear roll center by a similar amount as you are raising the front spindles.

If you don't want to go to through that approach, you can prop up the suspension some by running really stiff T-bars and sway bars, but you'll have very little suspension travel. Colin Chapment once pointed out that you can make any suspension work passibly well if you just stop it from working.

[cmcfaul]

John:

Your suggestions make a lot of sence. I am not 100% sure why the handeling of the car changed so dramatically when I went to the larger Rims but it definitly has. With out spending tons of money on an RSR type setup I want to improve the handeling and still keep it relitively stock.

4 wheels on the ground has got to be faster then 3. I know this is normal but won't stiffer T bars in the back stop this? The car is prefectly ballanced as is and I want to keep this ratio as Porsche designed it. So the goal is to stiffen the front and back by the same percentage to get the car back to it's original street handeling feel and improve the track preformance when back on the 15 inch rims at the same time.

My hope is that stiffer t bars all the way around will accomplish both. Replacing the t bars is a major pain as getting the hight right is trial and error so I want to make a good decision as to the stiffness.

Chris
73 911 E

[Zeke]

What rear sway bar do you have? I don't have much 911 suspension setup experience, but general knowledge might suggest a bigger bar on the rear to level the car and give the front end an opportunity to be more square to the ground when in a turn. Also, not too stiff a sway bar in the front will allow the inside front wheel to stay on or near the ground.

Furthermore, the car looks very low to me suggesting the car is on the bump stops in the corner. If you have lost some sidewall, you have lost some suspension provided by the tire itself.

Disclaimer: These are merely suggestions and not based on any data point I have. You can always bounce these ideas around in your mind while taking other suggestions in.

[cmcfaul]

Milt:

The front and rear sway bars are 1 MM thicker then stock. I also replaced all the rear bushings with the Weltmeister bushings (not the solid ones) almost a year ago.

I was told that bigger sway bars are a band-aid and that bigger t bars is the correct way to go.

Chris

73 911 E

[jluetjen]

4 wheels on the ground has got to be faster then 3. ... The car is prefectly ballanced as is

What are you concerned with? Looks or handling? The reality is that ultimate level of traction for the 911 is limited by the rear end, not the front. So the fact that you have the inside front wheel off the ground doesn't mean anything because at that point the front of the car still has more traction relative to the load it's carrying then the back. I'm not going to rehash the hows and whys since I already covered in the link that I posted above.

I know this (lifting a front wheel) is normal but won't stiffer T bars in the back stop this?

Sure they might, but they will also increase oversteer and make the ride harder. You can offset this by running a stiffer front sway bar, but then that will tend to pick up the inside front wheel even more. Ironically, by lowering the car you moved the suspension geometry out of it's designed range which results in the car squatting more then if you were to raise the car back up to "european" ride hight.

[Zeke]

Originally posted by cmcfaul


I was told that bigger sway bars are a band-aid and that bigger t bars is the correct way to go.



73 911 E

The jury is out on that one, AFAIC. There seems to be two schools of thought, if not more. One says use heavy and matched sway bars (matching doesn't necessarily mean the same size) and keep the car from leaning in the corner whille allowing the suspension to work.

The other school says to tighten up the car with heavy T-bars. Where you intend to drive the car will help you decide which way to go if not both.

In my case, I moved up the t-bar rate, installed a heavier shock and moved up the sway bars. I am looking for a relationship between all 3 where each compliments the the other in a ratio that keeps the original engineering in mind.

We'll see fairly soon if this is a good combo. Knowing that the rate increases may not be be linear, I could get it out of whack. That's one reason I have been conservative in choosing the amount of rate increase at each application.

I won't leave you guessing, I have 21/26 with 19mm sways and Koni Sports on a narrow body and 7 inch wheels wearing 50 series tires. The car has had maybe 100 lbs. removed.

[911pcars]

IMHO, larger torsion bars and sway bars are not mutually exclusive. In fact neither are better shocks. They all should eventually end up on everyone's 911; those that prefer improved handling that is.

My recommendations for an early body 911 for street:
21/26 or 21/27 torsion bars
16/19mm adj. sway bars
Koni or Bilstein shocks
Lowered
Corner balanced and aligned.

For more agressive driving, keep the above torsion bars and increase the front sway bar to 22, but not necessarily at the stiffest setting.

I would consider 22/28 torsion bars if my oft-traveled roads were glass smooth. Your shocks should be commensurate with these TBs.

But that's just me,
Sherwood

[Porsche Head]

Sherwood, thanks, I went with new 21/27 sway-away should get em shortly...

I also ordered the sway-away adjustable spring plates to make the job easier, so I'll have my old plates for sale soon

[cmcfaul]

The trick is to stiffing the suspensinon either through T bars and / or sway bars, keep the car as low as possible with out rubbing the wheels into the fenders (205 55 16's) and most importantly keeping the car balanced.

On the track as a basically stock early 911 that has been lowered and slightly stiffer sway bars (front and back) on 4 205 50 15 Kumo's the car is perfectly ballanced. I can cause over steer by lifting slightly and understeer by keeping the pedal on the floor.

My desire is to bring this charastic to the street on bigger rims and higher profile tires. I think I have the combinations needed.

Thanks for everyones help.

Chris
73 911 E