MX5 Rules & Regulations

Published Regulations

2025 Bristol Motor Club MX5 Challenge PUBLISHED

Please refer to the website calendar under Bristol MX5 Challenge/2025 Calendar for the latest updates compared to the Regulations as amendments may take place due to unavailability of a venue. 

For every championship, we publish rules, or “regulations”, that are approved by Motorsport UK, these are in addition to the Motorsport UK National Competition Regulations, which replaced the “Blue Book” for 2025.

The general ethos of the championship is that it should be possible to compete with a relatively standard car, with upgraded suspension, and do well without spending too much money.  The formula works well and produces a close competition where no single model of car is faster, over all events, than any other.

In controlling costs, it is also recommended that all spares (including any spare wheels), pit equipment and personal items should fit within an MX5 (including passenger seta and footwell), or equivalent space, when travelling to and from the circuit.  

We take pride in how the championship has brought competitors together to have fun and how we’ve been able to operate the championship with very few protests to the legality of cars over the years. We hope this continues and request that all entrants to future events continue to operate with this respect for the rules.      

All Models

• Cars must use tyres from List 1A
• Forced induction is not permitted
• The standard intake manifold, plenum and throttle body must be retained and the standard ECU must be used without a “piggy-back” ECU, whether electronic or mechanical
• Dampers must not have separate adjustment for high and low speed damping. Triple-adjustable coilovers are not permitted.
• An MX5 gearbox with standard internals must be used and only standard Mazda MX5 differentials from the appropriate model (i.e. any NA for a NA, any NB for a NB etc) may be used
• Final drive must be Mazda MX5
• Non-OEM exhaust backboxes and non-OEM bushes (including polyurethane material) may be used
• A soft top must remain fitted, hard tops may be additionally fitted if desired. Cars can compete open or closed
• Engine bonnet / cover and luggage / boot cover may not be replaced with an alternative material
• Rollbars/cages, competition seats and harnesses in accordance with Motorsport UK regulations may be fitted to any car
• All cars must run in a road legal condition and must retain the configuration of having 2 x functional seats, original dash and door cards.

Model Specific Rules

NA/NB models:

• Cars may run any brake size from the standard NA/NB range. Brake friction material (this covers the pads and disks) and dampers may be changed (which may be height adjustable).
• Anti Roll bars may be upgraded. Droplinks must remain non-adjustable and bushed.

NC models:

• Other than permitted modifications listed in the above ‘All Models’ section, cars must remain standard other than wheels (cars may run any wheel diameter size from the standard NC range), brake friction material (this covers the pads and disks) and dampers may be changed (which may be height adjustable).

For the avoidance of doubt, vehicles eligible for the championship are Mazda MX5 and Eunos models complying with the Motorsport UK National Competition Rules (NCR) Chapter 14, Appendix 4 and specifically Road Cars Series Production covered by article 14 other than detailed in the regulations.

Note the Regulation text takes precedent over the text on this webpage.