Hi, I’m looking for opinions on the best compromise between a standard belt, 3 point, and 4 point harness. This is to use in conjunction with Lotus seats and a roll bar that has a suitable harness bar on it. My car is a daily driver, but I also want to be able to do autosolo, hillclimbs and sprints in it … having previously rolled cars in competition I won’t feel properly safe in my MX5 without having a roll bar fitted.
With the standard belt there’s the potential to slip out in a roll scenario, and an increased risk of hitting one’s head on the roll bar in a rear-end collision. With a 3 or 4 point harness there’s the potential for submarining, though I don’t know if the fixed back seats affect that at all. There may also be issues with the distance between the harness bar and the seat if fitting a 3 point harness. Because of the nicely practical Lotus seats, a 5-point harness is not on the cards.
Fit any make of FIA-approved harness; that way you can retain the standard seatbelt. If I was doing a risk assessment, I’d say using a harness while driving on the road creates a greater potential for injury (cause of accident; inability to properly observe at junctions, reach controls etc) than you injuring yourself on a properly padded rollbar. 3 point harnesses are useless. You can also submarine with the standard belt.
You can modify the seat for a 5-point. I’ve tried the whole using a race harness on the road. Its rubbish.
Avoid 3-point harnesses. As you say, there’s nowhere near enough space between the seat and the harness bars. I used one for a while, and found it unfcomfortable, so switched to a 4-point. leave 3-points to cars like saxos where they take the rear seats out and anchor the neck strap at the back of the car.
Go 4 point with approved harnesses, if competing (hillclimb & sprint) some scrutineers won’t accept aftermarket (Sabelt, Sparco, OMP etc Clubmans harnesses although they allow a standard car 3 pointer, read definitions in the Blue Book)seen this happen in MX5 & standard production car classes at Prescott, Loton Park etc, I have been using in my MX5 the standard lap & diagonal with a CG Lock, not ideal but does a job & satisfies the man who signs the ticket, rgds, Paul H.
Watch your helmet clearance if you are going to compete in it. My helmet came above the tr lane roll bar with a standard seat. I ended up with a composite seat bolted to the floor to get enough clearance.
As Paul has said the MSA will insist on 4 point minimum, 3 point is not allowed. I witnessed a car at the weekend having a scrutineering issue on the points you have raised, so bear this in mind and read the blue book carefully. And please dont use the harnesses on the public highway, your visibility will be impaired if you have belts tight enough to protect you properly. I have screwed 7/16 eye bolts into the original points and the harness just clips to these when required.
Steve.
Good comment Steve, very sensible advice, as above I have been competing in 1600 - 2000cc standard production & HSA A2.1 class using the standard lap & diagonal with the CG lock, could be a good fall back point if difficulty in positioning a 4 point harness (not easy if using Mk1 seats as that’s a fail as well as shoulder straps won’t fit comfortably over shoulders unless you are “very” broad!) also re helmet & head height over the top of cage, can call for removing seat cushion foam to lower a tall person if using standard seats, B Rgds, Paul H.
Thanks, I’ve got a pair of Lotus Exige seats that came with MR2 brackets that I’m going to adapt - the driver’s side seat will be touching the floor by the time I’m finished, lol
I am thinking 4-point for use off-road is the best compromise given my budget etc, today at work I saw some of the new anti-submarining airbags that newer cars get, but they wouldn’t be suitable to retro-fit into an MX5!
