Which coilover sets don't reduce suspension travel when lowering ride height?
 

I have seen some discussion on this forum regarding loss of suspension travel when reducing ride height on certain coilover sets. I believe some coilover sets are designed to prevent this by threading the whole damper body allowing ride height to be adjusted via the position of the damper in the mounting bracket (similar to the Ohlins Road & Track system).

1. Which coilover sets don't reduce suspension travel when lowering ride height?

2. How much does this matter?

1. A lot of them.

2. Not as much as most think.

Separate ride height and preload adjustment can be a nice feature, but it needs to be implemented correctly. In general, these coilovers will have less total stroke than a conventional single height adjustable coilover. You may end up with more bump travel at very low ride heights, but not necessarily more bump travel at medium to mild drops. A single height adjustable coilover trades bump travel for droop travel when you lower the car, but unless you are lowering by a large amount, you may end up with a lot of both. Droop travel is still important, and depending on spring rates and if you're running helper/tender springs (and you usually should), you'll almost always have more with a single height adjustable coilover.

My recommendation has been that if you're slamming the car or want to go real low, separate ride height and preload can be very useful (with exceptions like the Ohlins for this car that don't like to go low). At a 1 inch drop though, you may actually have more bump travel with a conventional single height adjustable coilover. It does depend on the coilover. And you can run lowering top mounts (perhaps from Raceseng) to make up for some of the difference if you do want to go real low.

One thing to keep in mind is that MOST of the time (but not always), separate ride height and preload adjustment is a cost saving measure marketed as a must-have feature. This is why you see it on the lookalike low-end coilovers from China pretty consistently. They use one damper cartridge for multiple vehicles/applications, and slap on different upper and lower mounts. Done, easy. On the other hand, coilovers on the higher end of the spectrum (JRZ, MCS, AST, Bilstein motorsport, and so on) do not use separate ride height and preload adjustment.

You certainly could have a dual height adjustable coilover with helper springs and loads of both bump and droop travel, but I have not seen that in person.

- Andrew

The other thing with a threaded lower mount is that yes, you can go lower without losing bump travel, but if you do, the car can be too low, with too much bump travel. This means the tire can rub on stuff in the fender like wiring harnesses, axles can rub the frame, suspension links and ball joints can run out of travel...

If you do have a set of coilovers with an adjustable lower mount, you should be jacking the suspension through it's travel with the spring removed and making sure none of that happens.

This is a common discussion I have.
A "Dual Perch" coilovers does not provide better performance, but it provide more ride height adjustment flexibility.

The main advantage is the compression and rebound travel ratio are set (base on the springs pre-load).
Raising or lowering the ride height does not change this ratio, and that mean the suspension will function at either extreme (the highest or the lowest ride height) setting.

The disadvantage depending on how the suspension was designed is that it can lack total damper travel.
Another point brought up is while the damper will function, it is possible for other parts to get in the way at extreme setting.

I personally prefer the dual perch design as it mean you can design a system that will work within it's available ride height adjustment.
You won't get complain of harsh ride quality from bottoming out the damper at the lowest setting.
The long as the suspension are optimised reasonably, then you will get a good performance as well as flexible ride height adjustment.

As far as using longer travel damper and incorporate helper springs to optimise rebound travel, it is something we have done.
But it isn't applicable in the GT86 / FRS / BRZ chassis as there simply isn't the room available without severely limiting ride height adjustment range.

Jerrick

You should also consider the case when the car is yawing as the sway bar rates will come into play.