Recommendations for rear torsion bars for street?

[911TT33]

Hey guys,

I’m considering upgrading my rear torsion bars to something stiffer as there’s too much rear end squat under acceleration, and I suspect with the extra weight of the twin turbo setup, it’ll be worsened! 🙄

What are you guys running?

I’m thinking light weight, hollow torsion bars that are 29mm. I think OEM torsion bars are 26 or 27mm. Thoughts/suggestions?

Car is pure street, so I don’t want any back breaking stiffness. I just want to reduce rear end squat significantly.

[RarlyL8]

Personal preference is to not go over 29mm on the street assuming the car has not been lightened.
Another option is to add coil-over helper springs. They are adjusted to kick in when the car begins to squat. The stock ride is preserved.

[Tinker]

I think you'd be surprised as to how little the ride quality diminsihes with larger bars.
I have a 72 911 that was originally a street car that I later updated the suspension and club raced. It has 23 / 31 torsion bars with custom valved Bilstein shocks. The car weighs much less than a 930 and is street licensed. I'm not a young guy, the ride is firm, but not harsh or uncomfortable.

Tinker

[spuggy]

Originally Posted by Tinker

I think you'd be surprised as to how little the ride quality diminsihes with larger bars.
I have a 72 911 that was originally a street car that I later updated the suspension and club raced. It has 23 / 31 torsion bars with custom valved Bilstein shocks. The car weighs much less than a 930 and is street licensed. I'm not a young guy, the ride is firm, but not harsh or uncomfortable.

Tinker

I agree. I run 21/30 TBs on a car that used to weigh sub-2500 lbs with no carpets or tools and barely any fuel (it's got a few heavier things fitted now) - the front is supple enough to keep up over fast, rippled concrete (eg rain-grooved exit ramps), and the rear controlled squat (mostly, sort of) with a 3DLZ, where power onset was quite abrupt, to say the least.

I also changed to late 3.2 sways from the early ones - too much body roll for my taste otherwise.

The ride is firm, little crashy over potholes - but not stupid by any means.

With a turbo setup that delivers power in a more linear fashion than a 3DLZ (that bar is pretty darned low), you probably won't get as much squat anyway - I find the K27/HF to be very progressive in boost.

There's still a fair amount of weight transfer, but the steering doesn't get finger-tip light with the cowl noticeably rising in your line of sight ... In fact, it /feels/ much less violent than the 3DLZ, even though it makes much more power.

[zakthor]

I have 22 and 30. I was really surprised how smooth the car rode when I got it done. Prior to work the car pointed at the sky on acceleration.

Fordahl said it was shocks and big sway bars that ruin the ride on the street and I think he was right. Here’s was also right that monoball shock mounts don’t harm the ride at all and removing the big rubber doughnut makes suspension much more precise in corners.

Here’s the thread from when I went though this. I eventually settled for a larger rear sway from an 88 930 (needs to be 930 sway to clear the transmission.) I couldn’t be happier.

https://forums.pelicanparts.com/911-930-turbo-super-charging-forum/563335-930-suspension-pacific-nw.html

And here’s my sway bar thread

https://forums.pelicanparts.com/911-930-turbo-super-charging-forum/867665-can-i-buy-clue-930-rear-sway-bar.html

[911TT33]

Thanks for the feedback guys.

My 911 has the M491 option, which is essentially the turbo look Carrera with the 930 turbo suspension.

All I’ve ever done to the suspension is add Koni adjustable shocks all round.

The OEM turbo torsion bars are way too soft, so I think I’ll definitely go for a stiffer setup. Now I’m thinking 21-22F/30R.

I’m also looking to change all tyres to Rear:295/30R18 and Front:245/35R18.

[RarlyL8]

18" wheels make a significant difference in ride quality. I ran 315/30-18, 315/35-17, 245/45-16 and 345/35-15 on 29mm bars and the ride when going from 17" to 18" was much worse than going 15" to 17'. This is why I don't go over 29mm in the rear and use helper springs. Squat is significant when you double the horsepower, ride degradation is significant when you go bigger than 17" wheels.

[911TT33]

Originally Posted by RarlyL8

18" wheels make a significant difference in ride quality. I ran 315/30-18, 315/35-17, 245/45-16 and 345/35-15 on 29mm bars and the ride when going from 17" to 18" was much worse than going 15" to 17'. This is why I don't go over 29mm in the rear and use helper springs. Squat is significant when you double the horsepower, ride degradation is significant when you go bigger than 17" wheels.

Thanks for the advice. Do you have any links to these helper springs you refer to?

[Pat RUFBTR]

Originally Posted by RarlyL8

18" wheels make a significant difference in ride quality. I ran 315/30-18, 315/35-17, 245/45-16 and 345/35-15 on 29mm bars and the ride when going from 17" to 18" was much worse than going 15" to 17'. This is why I don't go over 29mm in the rear and use helper springs. Squat is significant when you double the horsepower, ride degradation is significant when you go bigger than 17" wheels.

Hello !
The 255/40/17 has practically the same diameter as the 295/30/18, can we still feel a difference in road behaviour by changing from 17" to 18"? :confus:

[greglepore]

Originally Posted by RarlyL8

18" wheels make a significant difference in ride quality. I ran 315/30-18, 315/35-17, 245/45-16 and 345/35-15 on 29mm bars and the ride when going from 17" to 18" was much worse than going 15" to 17'. This is why I don't go over 29mm in the rear and use helper springs. Squat is significant when you double the horsepower, ride degradation is significant when you go bigger than 17" wheels.

This. I run 22/29 on 17's, Bilstein rear Koni front, Elephant Polybronze everywhere, late Carrera sways. Plenty enough for the street. I wouldn't want those bars in a "car" that I drove everywhere everyday, but fine in something where you're focused on the actual experience all of the time.

[RarlyL8]

The 255/40/17 has practically the same diameter as the 295/30/18, can we still feel a difference in road behaviour by changing from 17" to 18"?

The difference in ride quality is related to the sidewall height. If a tire on a 17" rim is the same height as a tire on an 18" rim the sidewall height of the tire on the 17" rim is 1/2" more than that of the tire on the 18" rim. The same tire height using a 15" rim results in a sidewall height difference of 1.5". More sidewall height gives more cushion when you hit a bump.

Do you have any links to these helper springs you refer to?

Yes I can get you the same setup I use, shoot me an email or call. As pointed out this option is specific to those with modified engines wanting to keep a softer ride quality but reduce the squat. A side effect is it makes fine adjustment of the ride heigh as simple as turning a (very large) screw.

[patina]

I’m going to agree with others that you’ll be perfectly fine running bigger bars on the street. I am running 22mm front bars and 33mm rear bars with custom valved Von shocks. The car is much more compliant that it was on stock bars with Bilsteins and is absolutely planted in corners. The 930s are way too soft in the rear from the factory.

[Rodsrsr]

I cant imagine running 33 mm rear bars on the street. That thing must ride like a cement truck. Even with revalved shocks 33 is a very thick bar. I was running 23/28 which was just too stiff for my liking, so just reduced the front to 21 which is 100% better. I'll be switching out the rear 28's for 27s.

Shocks were Bilstein HD's up front now changed out to Koni Sport Adjustable. Rears are Bilstein yellow sports, and I'll see how it feels with the 27's but may swap to Konis if its still too stiff.

[patina]

Originally Posted by Rodsrsr

I cant imagine running 33 mm rear bars on the street. That thing must ride like a cement truck. Even with revalved shocks 33 is a very thick bar. I was running 23/28 which was just too stiff for my liking, so just reduced the front to 21 which is 100% better. I'll be switching out the rear 28's for 27s.

Shocks were Bilstein HD's up front now changed out to Koni Sport Adjustable. Rears are Bilstein yellow sports, and I'll see how it feels with the 27's but may swap to Konis if its still too stiff.

I regularly drive the car on ~3 day ~1500 mile rallyes. Highway driving up to the mountains then ripping for a long weekend then driving home. Car is great.

[911TT33]

So in terms of torsion bar brands, which do you guys recommend? Elephant Racing? Other?

Is it worth going with hollow lightweight ones?

Advice appreciated 🙏🏼