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Light Weight Hollow Rear Torsion Bars, Tubular. Porsche 911 1987-89 G50 - RT21
RT21
Vehicle Group
- Porsche 911 1987-1989 3.2L G50
- Porsche 911 1978-1989 3.3L Turbo (930)
Information
High-performance Sway-A-Way hollow rear torsion bar set for Porsche 911 models equipped with the G50 transmission from 1987 to 1989. Available in 27 mm, 28 mm and 29 mm rates. Designed as a direct performance replacement for the original rear torsion bars, these tubular bars provide increased rear suspension control while reducing weight compared with equivalent solid torsion bars.
SET OF 2, One pair is required per vehicle
Fits:
Porsche 911 1987-1989 3.2L G50
Porsche 911 1978-1989 3.3L Turbo (930)
Always confirm that your vehicle uses the G50 transmission and corresponding rear suspension configuration before ordering.
The tubular construction is engineered so that the hollow bar provides the same effective spring rate as the equivalent solid-diameter torsion bar, while reducing the amount of material and therefore overall component weight.
Sway-A-Way torsion bars are manufactured from high-strength, heat-treated alloy steel. The bars are precision centreless ground for consistent dimensions and spring characteristics, then finished with a protective powder coating to help resist corrosion.
Available Torsion Bar Rates
27 mm - Fast-road and occasional track use
The 27 mm tubular rear torsion bar provides a useful performance increase while remaining a sensible option for cars that see regular road use. Sway-A-Way identifies the tubular 27 mm bar as having the stiffness of an equivalent solid 27 mm torsion bar while providing a useful weight reduction.
Recommended for:
• Fast-road Porsche 911s
• Uprated road suspension
• Occasional track-day us
• Cars using uprated dampers and front torsion bars
The 27 mm option provides greater rear suspension support without immediately moving to one of the highest rates in the range.
Technical Setup & Performance Notes:
• Unsprung Weight Benefits: Because the tubular bar is lighter, the suspension has less inertia. This allows your dampers to work more efficiently, resulting in better mechanical grip on rougher track surfaces or uneven canyon roads.
• Matched Balancing: A 27mm rear rate is a significant jump. To maintain the 911’s famous handling balance, it is highly recommended to pair these with 21mm or 22mm front torsion bars.
• Damping Requirements: Standard shocks may struggle with the increased "snap" of a 27mm rate. Custom-valved Bilstein or Koni dampers are recommended to properly control the rebound.
• Spline Care: During installation, apply a generous amount of waterproof anti-seize grease to the splines. Because tubular bars are more resonant than solid ones, proper lubrication is essential to prevent "creaking" or "clunking" sounds.
28 mm - Fast-road / track-day performance (not recommended for off-road use)
The 28 mm tubular rear torsion bar provides a further increase in spring rate, offering stronger control of rear suspension movement during hard acceleration and cornering.
Recommended for:
• Aggressive fast-road use
• Road and track-day cars
• Autocross
• Performance builds using modern high-grip tyres
• Cars with matched performance dampers.
This is a strong middle option for drivers wanting a more focused chassis while retaining some flexibility for road use.
29 mm Track-focused and competition-oriented applications (not recommended for off-road use)
The 29 mm tubular rear torsion bar is the firmest of these three G50 options and is aimed at more serious performance-oriented suspension setups.
Recommended for:
• Track-focused Porsche 911s
• Competition-inspired builds
• Autocross
• Lightweight cars
• High-grip tyre setups
• Cars with appropriately matched front torsion bars and performance dampers
The increased rear spring rate provides greater resistance to squat and roll but should be combined with a balanced overall suspension package.
Why Upgrade the Rear Torsion Bars?
The classic Porsche 911 suspension uses torsion bars as its primary springs. As suspension load increases, the torsion bar twists along its length. The resistance to this twisting action determines the effective spring rate.
Increasing the torsion-bar rate can provide:
• Reduced body roll
• Reduced rear-end squat during acceleration
• Improved suspension control
• More immediate chassis response
• Greater stability during fast cornering
• Better support for high-grip modern tyres
• Improved control during track use
• Improved balance when combined with complementary front suspension upgrades.
The larger the effective torsion-bar diameter, the greater the spring rate.
Tubular / Hollow Construction
Sway-A-Way tubular torsion bars are designed to reduce weight without sacrificing the desired spring rate.
The internal diameter of the hollow bar is engineered so that its torsional stiffness corresponds to the stated solid-bar rate.
This means a 27 mm tubular-rate bar is designed to provide the spring characteristics associated with a 27 mm solid torsion bar, rather than simply being a hollow 27 mm tube with a significantly softer rate.
This construction provides an attractive combination of:
• High torsional strength
• Reduced component weight
• Consistent spring rate
• Durable performance
• Motorsport-oriented engineering.
For Porsche owners looking to reduce unnecessary weight while upgrading suspension performance, the tubular design provides a useful advantage over conventional solid bars.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
RT21
The product you are viewing cross references to these numbers
SET OF 2, One pair is required per vehicle
Fits:
Porsche 911 1987-1989 3.2L G50
Porsche 911 1978-1989 3.3L Turbo (930)
Always confirm that your vehicle uses the G50 transmission and corresponding rear suspension configuration before ordering.
The tubular construction is engineered so that the hollow bar provides the same effective spring rate as the equivalent solid-diameter torsion bar, while reducing the amount of material and therefore overall component weight.
Sway-A-Way torsion bars are manufactured from high-strength, heat-treated alloy steel. The bars are precision centreless ground for consistent dimensions and spring characteristics, then finished with a protective powder coating to help resist corrosion.
Available Torsion Bar Rates
27 mm - Fast-road and occasional track use
The 27 mm tubular rear torsion bar provides a useful performance increase while remaining a sensible option for cars that see regular road use. Sway-A-Way identifies the tubular 27 mm bar as having the stiffness of an equivalent solid 27 mm torsion bar while providing a useful weight reduction.
Recommended for:
• Fast-road Porsche 911s
• Uprated road suspension
• Occasional track-day us
• Cars using uprated dampers and front torsion bars
The 27 mm option provides greater rear suspension support without immediately moving to one of the highest rates in the range.
Technical Setup & Performance Notes:
• Unsprung Weight Benefits: Because the tubular bar is lighter, the suspension has less inertia. This allows your dampers to work more efficiently, resulting in better mechanical grip on rougher track surfaces or uneven canyon roads.
• Matched Balancing: A 27mm rear rate is a significant jump. To maintain the 911’s famous handling balance, it is highly recommended to pair these with 21mm or 22mm front torsion bars.
• Damping Requirements: Standard shocks may struggle with the increased "snap" of a 27mm rate. Custom-valved Bilstein or Koni dampers are recommended to properly control the rebound.
• Spline Care: During installation, apply a generous amount of waterproof anti-seize grease to the splines. Because tubular bars are more resonant than solid ones, proper lubrication is essential to prevent "creaking" or "clunking" sounds.
28 mm - Fast-road / track-day performance (not recommended for off-road use)
The 28 mm tubular rear torsion bar provides a further increase in spring rate, offering stronger control of rear suspension movement during hard acceleration and cornering.
Recommended for:
• Aggressive fast-road use
• Road and track-day cars
• Autocross
• Performance builds using modern high-grip tyres
• Cars with matched performance dampers.
This is a strong middle option for drivers wanting a more focused chassis while retaining some flexibility for road use.
29 mm Track-focused and competition-oriented applications (not recommended for off-road use)
The 29 mm tubular rear torsion bar is the firmest of these three G50 options and is aimed at more serious performance-oriented suspension setups.
Recommended for:
• Track-focused Porsche 911s
• Competition-inspired builds
• Autocross
• Lightweight cars
• High-grip tyre setups
• Cars with appropriately matched front torsion bars and performance dampers
The increased rear spring rate provides greater resistance to squat and roll but should be combined with a balanced overall suspension package.
Why Upgrade the Rear Torsion Bars?
The classic Porsche 911 suspension uses torsion bars as its primary springs. As suspension load increases, the torsion bar twists along its length. The resistance to this twisting action determines the effective spring rate.
Increasing the torsion-bar rate can provide:
• Reduced body roll
• Reduced rear-end squat during acceleration
• Improved suspension control
• More immediate chassis response
• Greater stability during fast cornering
• Better support for high-grip modern tyres
• Improved control during track use
• Improved balance when combined with complementary front suspension upgrades.
The larger the effective torsion-bar diameter, the greater the spring rate.
Tubular / Hollow Construction
Sway-A-Way tubular torsion bars are designed to reduce weight without sacrificing the desired spring rate.
The internal diameter of the hollow bar is engineered so that its torsional stiffness corresponds to the stated solid-bar rate.
This means a 27 mm tubular-rate bar is designed to provide the spring characteristics associated with a 27 mm solid torsion bar, rather than simply being a hollow 27 mm tube with a significantly softer rate.
This construction provides an attractive combination of:
• High torsional strength
• Reduced component weight
• Consistent spring rate
• Durable performance
• Motorsport-oriented engineering.
For Porsche owners looking to reduce unnecessary weight while upgrading suspension performance, the tubular design provides a useful advantage over conventional solid bars.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
RT21
91133311500
91133311502
91133311600
91133311602
The product you are viewing cross references to these numbers
Prices from: £595.00