Ultra Racing 4-point rear lower chassis brace for Mazda MX-5 MK4 / ND and RF models listed in the compatibility table.
The Ultra Racing RL4-3720 is a rear lower bar / rear member brace designed as an aftermarket chassis reinforcement upgrade for the fourth-generation Mazda MX-5.
Mounted beneath the rear of the vehicle, this four-point brace links key chassis and suspension mounting areas to help reduce unwanted movement and flex under cornering loads. Reinforcing this area can help the rear suspension operate more consistently and improve overall chassis response.
Product details:
- Brand: Ultra Racing
- Part number: RL4-3720
- Product type: Rear Lower Bar / Rear Member Brace
- Position: Rear lower chassis
- Brace specification: 4 Point
- Construction: One-piece welded steel
- Finish: Ultra Racing white
- Installation method: Bolt-on using vehicle mounting points
- Ultra Racing accessory reference: BC051
- Approximate dimensions: 62cm x 4cm x 3cm
- Approximate weight: 0.9kg
- Quantity required per vehicle: 1
- Quantity supplied: 1 rear lower brace
Common reasons for fitting:
- Reduce unwanted flex through the rear lower chassis structure
- Reinforce key rear suspension and chassis mounting areas
- Help improve suspension consistency during cornering
- Improve chassis response during fast road or track use
- Complement other front, centre and rear chassis bracing upgrades
Fitment advice:
Designed for Mazda MX-5 MK4 / ND applications. The brace mounts beneath the vehicle, so sufficient and safe underbody access is required during installation. For imported, modified or previously repaired cars, matching the mounting arrangement on the vehicle before installation is recommended.
Other items to consider purchasing:
- Ultra Racing front strut brace
- Ultra Racing front lower / member brace
- Ultra Racing middle member brace
- Ultra Racing anti-roll bars
- Replacement suspension fasteners or bushes where existing components show wear
Useful tools / consumables:
- Socket and ratchet set
- Torque wrench
- Suitable vehicle lift or axle stands
- Penetrating fluid for corroded underbody fasteners where required
Difficulty guide: Intermediate DIY / workshop installation. Safe lifting of the vehicle and access to the rear underside are required.
Why Ultra Racing?
Ultra Racing specialises in aftermarket chassis and handling upgrades. Its chassis braces use rigid one-piece welded construction designed to reinforce key areas of the vehicle structure and reduce unwanted movement between mounting points.
What's in the box:
- 1 x Ultra Racing RL4-3720 rear lower chassis brace
- Required mounting hardware where applicable
Installation notes:
Ultra Racing specifies RL4-3720 as a bolt-on installation. The vehicle will need to be safely raised to provide access to the rear lower mounting points. Position the brace correctly and check clearance around surrounding suspension, exhaust and underbody components before final tightening. Reassemble and tighten all mounting hardware to the appropriate vehicle or manufacturer specification.
| Make | Model | Sub Variant | Chassis / Code | Years | Power (PS) | Engine Codes | Fuel | Transmission | Notes |
|---|---|---|---|---|---|---|---|---|---|
| Mazda | MX-5 MK4 / ND | 1.5 Roadster | ND / ND5RC | 2015 onwards | 131 / 132 | P5-VP / P5-VPR | Petrol | Manual | 4-point rear lower / rear member brace. |
| Mazda | MX-5 MK4 / ND | 2.0 Roadster | ND | 2015 onwards | 160 / 184 | PE-VPS | Petrol | Manual / Automatic where fitted | 4-point rear lower / rear member brace. |
| Mazda | MX-5 RF | 2.0 RF | ND / RF | 2017 onwards | 160 / 184 | PE-VPS | Petrol | Manual / Automatic where fitted | Retractable Fastback; 4-point rear lower chassis brace. |
| Reference Type | Reference Number | Notes |
|---|---|---|
| Mazda OE | N/A | No direct Mazda OE reference - aftermarket chassis reinforcement part |