Traxxas Rear Shock Spring Silver Progressive 1.042 Rate GTR TRX8445X

Overview

The Traxxas Spring, shock, Rear (Silver) (GTR) (progressive, 1.042 rate) (2 pcs) TRX8445X represents premium suspension tuning for your RC short course truck. Whether you're racing competitively on a dedicated track or enjoying weekend bashing adventures across varied terrain, these custom-wound rear shock springs deliver the responsive control that separates average performance from championship results. Designed specifically for the Traxxas UDR Unlimited Desert Racer and compatible GTR shock platforms, these silver springs embody Traxxas's commitment to suspension excellence that UK RC enthusiasts have trusted for decades.

Suspension tuning is one of the most powerful tools in any RC driver's arsenal, and springs are fundamental to getting it right. A properly matched spring rate works in harmony with your shock's damping characteristics to ensure your vehicle stays planted during corners, absorbs massive jumps without bottoming out, and maintains consistent traction across all terrain types. The TRX8445X springs give you the ability to fine-tune your ride quality, handling balance, and overall performance to match your specific driving style and local track conditions.

These aren't generic springs—they're engineered components that make measurable differences in lap times and driving confidence. For RC car and truck enthusiasts in the UK seeking genuine Traxxas suspension components, the TRX8445X offers the perfect balance of progressive-rate technology with proven reliability. RC Model Shop stocks these authentic springs and can advise you on the complete suspension setup strategy.

Key Features

• Progressive-Rate Design — Progressive springs provide responsive control for small bumps with a progressively stiffer rate that absorbs harder impacts, giving you the best of both worlds: sensitivity to minor terrain features and resilience under extreme conditions. This means your suspension reacts quickly to small undulations while resisting bottoming out on big hits, delivering confidence and control in mixed terrain.
• 1.042 Spring Rate — The 1.042-rate specification is precisely engineered for GTR shocks to deliver the ideal balance between compliance and support, matching the damping characteristics of your shock absorber for optimal suspension performance. This rate has been proven through Traxxas's extensive testing to work across desert racing, track racing, and general bashing conditions.
• GTR Shock Compatibility — These springs are custom-wound specifically for 139 mm GTR shock bodies, ensuring perfect fitment and performance. GTR shocks feature threaded bodies for precise ride-height adjustment without additional parts, and these springs integrate seamlessly into that system for quick, tool-free tuning.
• Silver Colour Identification — The distinctive silver finish serves as a visual identifier for this specific rate, making it easy to track your suspension setup at the track or workshop. Colour-coded springs are an industry standard that helps prevent confusion when running multiple spring rates as part of your tuning library.
• Pair of Two Springs — The TRX8445X package includes two springs, providing matched components for your rear suspension. Both springs are wound to identical specifications, ensuring consistent performance across your vehicle's rear axle and predictable handling characteristics.
• Tuning Versatility — By selecting from Traxxas's range of spring rates, you can compensate for lighter or heavier vehicle configurations, adjust to different track surfaces, or modify your suspension to suit seasonal conditions. The higher the rate number, the firmer the spring, allowing you to dial in your exact performance requirement.
• Professional-Grade Engineering — Traxxas springs are manufactured to exacting tolerances using materials selected for consistency and longevity. Each spring is tested to ensure it meets specifications and will perform reliably through countless track sessions or bashing adventures.

Technical Performance

Understanding how shock absorbers work is essential to appreciating why these springs matter. Every shock absorber has two critical components: the spring and the damper. The spring absorbs jolts and stores energy before releasing it to return the suspension to its starting point, whilst the damper (a piston displacing oil inside a cylinder) prevents the spring from constantly bobbing up and down. Without proper damping, your vehicle would oscillate continuously, wallowing in corners and losing traction. The TRX8445X springs work in concert with your GTR shock's oil-filled damper to create a suspension system that responds quickly to terrain input without becoming unstable. When spring rate and damping force are properly matched—as they are with this Traxxas combination—your suspension will support the vehicle without being too stiff (which causes a bumpy ride and reduced traction) or too soft (which causes excessive chassis roll and bottoming out). The 1.042-rate progressive spring is engineered so that small compressions require less force, allowing the suspension to respond sensitively to minor bumps, whilst larger compressions encounter progressively stiffer resistance to handle big impacts. This creates superior performance across varied terrain compared to linear springs. For GTR shocks specifically, Traxxas has selected damping settings that pair perfectly with their spring offerings. The shock pistons in GTR shocks feature adjustable hole sizes ranging from 0.95 to 1.6 mm, allowing you to fine-tune damping independently, and the shocks typically use 30-weight silicone oil. When you combine the TRX8445X springs with your shock's damping options, you gain tremendous tuning flexibility. Ride height on GTR shocks is adjusted by threading the spring retainer up or down the shock body—a precision system that requires no additional spacers. This means you can adjust your suspension geometry to set ride height close to the middle of suspension travel, which is ideal for maximising both up-travel (for absorption of big hits) and down-travel (for maintaining traction when the wheels drop into ruts or dips). For maximum performance in smooth or high-grip conditions, lower ride-height settings lower the vehicle's centre of gravity and improve cornering performance. For rougher terrain and looser conditions, higher settings improve ground clearance and allow more up-travel for jump landings. Most UK off-road RC drivers set ride height by visual reference to suspension arm angle or driveshaft angle, then test and adjust from there.

What's in the Box

• Traxxas Spring, shock, rear (silver) GTR progressive 1.042 rate — two pieces

What You Need to Complete

• Compatible GTR shock absorber assembly (front and rear shocks must be present on your vehicle)
• Traxxas UDR or compatible vehicle with GTR shock platform
• Allen wrench or small screwdriver for shock collar adjustment (if adjusting ride height)

Frequently Asked Questions

• What does progressive-rate mean and why is it better than a standard spring? — A progressive-rate spring has a variable stiffness that increases as the spring compresses. Unlike a linear spring with constant stiffness throughout its travel, a progressive spring feels soft and responsive for small bumps but becomes progressively stiffer as it compresses further, protecting against bottoming out on large impacts. This means you get a smoother ride over minor terrain features whilst maintaining support for extreme hits—the best compromise between comfort and durability for diverse terrain.
• Are these springs suitable for beginners? — Yes, absolutely. The TRX8445X springs come factory-matched to the Traxxas UDR and are part of Traxxas's carefully optimised suspension package. If you own a compatible vehicle and simply want genuine replacement springs or wish to experiment with suspension tuning, these are an excellent choice. However, suspension tuning involves understanding how spring rate, damping force, and ride height interact. Beginners are advised to start with factory settings and make only one change at a time, testing between adjustments. The Traxxas Suspension Tuning Guide (available on their website) provides detailed guidance for understanding and adjusting springs.
• How do I know if I need stiffer or softer springs? — If your vehicle is bottoming out excessively on big jumps or feels unstable, you may need stiffer springs. If your vehicle feels harsh and bouncy even on smooth surfaces, or if the suspension doesn't react quickly enough to small bumps, you may benefit from softer springs. However, before changing springs, Traxxas recommends first adjusting damping force by changing piston hole sizes or oil viscosity—smaller changes that are easier to reverse. If you've already maximised damping adjustment and still need improvement, then spring rate changes become the next step. Spring rate and damping must be properly matched; if you increase spring rate significantly, you may also need to increase damping to prevent oscillation.
• What is the 1.042 rate specification and what does it mean? — Spring rate is a measure of stiffness, specifically how many pounds of force are required to compress a spring one inch. A 1.042-rate spring is considered relatively soft, making it suitable for vehicles that need responsive handling across varied terrain. Traxxas offers springs in various rates, colour-coded for easy identification. The higher the rate number, the stiffer the spring. The 1.042-rate TRX8445X is optimised for the UDR's desert-racing mission, balancing sensitivity to terrain input with sufficient stiffness to handle the vehicle's weight and performance demands.
• Will these springs fit my existing shocks? — These springs are specifically designed for 139 mm GTR shock bodies. They are compatible with the Traxxas UDR Unlimited Desert Racer Pro-Scale 4WD RTR Short Course Truck (both Rigid Industries and Fox Racing variants), and any other vehicle using standard GTR shocks. Do not attempt to fit them to Ultra Shocks or other non-GTR shock platforms—they are engineered for GTR geometry and will not perform correctly in other systems.
• Can I use these springs for racing and bashing, or should I have different setups? — Traxxas carefully optimises springs specifically for each model to deliver versatile performance in all types of terrain. The TRX8445X springs are suitable for both competitive track racing and recreational bashing. However, experienced racers often maintain multiple spring rates and damping settings for different conditions. For maximum performance, you may want to experiment with stiffer springs (higher rate numbers) for smooth, high-grip tracks where lower ride height improves cornering, and softer springs for rough terrain where higher ride height improves ground clearance. This is why a selection of springs is an essential part of any serious racer's pit box.
• How do I adjust ride height with GTR shocks? — GTR shocks have threaded bodies for precise ride-height adjustment. To adjust ride height, simply turn the spring retainer collar up or down the shock body. Traxxas recommends marking one ridge on the collar with paint so you can easily count each turn as you adjust. Ride height should be set close to the middle of suspension travel to balance up-travel and down-travel. A typical starting point is with the driveshaft level, or with suspension arms level, then test and adjust by 1-3 mm as needed.
• What's the difference between these silver springs and other Traxxas spring colours? — Traxxas colour-codes its springs for easy identification and tracking of different rates. Silver is the colour identifier for the 1.042-rate springs included in this package. Other rates have different colours (blue, green, red, etc.). Colour-coding is purely a visual identification system; the actual performance difference is in the rate number itself. By maintaining a selection of colour-coded springs in your workshop, you can quickly grab the correct rate for your desired setup without confusion.

Why Buy from RC Model Shop?

RC Model Shop is a trusted UK RC retailer and authorised dealer for all the brands we stock, including Traxxas, ARRMA, Losi, FTX, Hobbywing, Spektrum and more. Based in Walsall, we have a physical store where customers are welcome to come in, view products and purchase in store. Whether you are a seasoned competitor, a weekend basher, or just discovering the world of RC for the first time, our team of experienced RC enthusiasts is here to help you find the perfect setup and provide ongoing support. Order the Traxxas Spring, shock, Rear (Silver) (GTR) (progressive, 1.042 rate) (2 pcs) TRX8445X today with confidence, knowing you are buying from an authorised retailer with genuine products, expert knowledge and a commitment to customer satisfaction. Shop online or visit us in Walsall — we look forward to helping you get the most out of your RC experience.