Hi Charlie,
Great stuff! It’s a fine balance between comfort/handling/looks so here we go:
Other Considerations Before Coilovers
- ANTI-ROLL BARS: To improve handling/feel without compromising comfort you can get a stiffer set of anti roll bars. Anti roll bars connect the left side suspension to the right side suspension. This means that the body wont roll as much for twisty b road corners and you’ll still maintain the ride height and comfort that you’re used to for motorways and potholes.
- JUST SPRINGS: Usually changing just springs is more laborious than coilovers as you have to disassemble your old coilovers (which may be in poor condition). It also means that you will probably bottom out more as the dampening hasn’t been matched to the reduced amount of travel you now have. People usually do this for looks on a budget with significant comprimise.
Coilovers
There are 5 main aspects to consider when purchasing coilovers:
- Suspension Travel (how much it lowers compared to stock)
When you reduce the travel this reduces the height of the centre of gravity of the car improving feel and reducing body roll. - Spring Stiffness
Coilovers will usually quote a spring stiffness in kg/mm or lb/in of travel, the lower the value the softer the spring. A high spring rate will mostly produce a stiffer ride (amongst other things) - Coilover Damping
An increased rate of damping will lead to a stiffer ride (amongst other things) - Top Mounts
Some companies don’t include top mounts with their coilover suspension, these wear over time and you’ll likely want to replace these if you haven’t already. So bear in mind that if the coilovers don’t come with top mounts, this will be an additional cost. - Quality, Cost, & Reliability
Usually correlates with price, brand, & maintenance/cleaning. Most aftermarket suspension retailers will only give a 1-2 year warranty but don’t let this put you off as they wont break on the 366th day
Summary
I’m assuming your MX5 is stock otherwise (stock rim & tyre profile, stock bushings & suspension fittings. So if you don’t mind a slight increase in harshness a set of HSD adjustable coilovers seems about right. They can be found here: HSD Coilover Suspension | hsdcoilovers.com
I honestly wouldn’t stress over twin tube vs mono tube if you’re not pushing your car at the track and need the perfect cornering. Just get a set of coilovers that have adjustable height and damping with a reasonable spring rate (HSD recommends 9kg/mm front & 7kg/mm rear but you can pick softer or harder). This way if you set it up on the harshest setting or too low you can always dial it back for comfort. The prices aren’t too unreasonable either.
Anecdote
I have the HSD Dualtechs on a Turbo MK1 1990 Eunos 1600cc with 9kg/7kg springs, on the lowest damping setting at the highest height on 15x7 rims with 190/50/15 tyres and I would consider this firm but not unreasonable. The car is used as a daily and has been used on the track.
Best of luck!