Monday, March 28, 2016

Tech Tip: Coilovers

One of the single biggest improvements you can make to your car is proper suspension setup. Light weight cars are very responsive to suspension setup changes and that applies to a good setup as well as a poor one. The stock Lotus suspension is very good, however, anyone who has done suspension design and setup will tell you that the entire thing is an art in compromise. The Lotus engineers had to consider the cost of each component as well as the fact that they were building a road car, not a race car. For those seeking better performance from their cars, especially on the track, you can not make a much better upgrade than a coil over suspension system. Coilovers allow you to make spring rate changes relatively easily in order to suit specific road or track conditions, rebound and damping adjustments allow the ability to fine tune not only the ride quality of the car but its handling characteristics, they allow you to lower the car (thus lowering the center of gravity), and they just look awesome! We carry the full range of Nitron suspension from street to track.

The best you can get, Nitron 46mm triple adjustable shocks
A few years ago we posted a blog showing where to measure the ride height on the Lotus Elise and Exige. That post can be found HERE. To add to that, here are a few tips when setting ride height.

1) Know the goal and the limits. When setting ride height, you are not really just setting ground clearance, you are setting where the suspension sits in its travel. Ride height is just a more simple way to do this than measuring an exposed shock shaft or the angle of the a-arm. The Lotus engineers spec'd the stock ride height not only to provide adequate ground clearance, but also to put the suspension in the ideal spot in the travel. If you want to set ride height much below about 120mm, it is best to do this with raceUPRIGHTS these allow a low ride height (and CG) but leave the suspension geometry closer to stock. We do not recommend these for the street. 

2) Settle the suspension. When you jack up the car and the suspension droops, the tires actually move inward toward the center of the car. When you lower the car back down, the tires stick to the ground and do not push outwards, this causes the car to sit artificially high. We use hubstands with built in rollers to stop this but you can settle the car back down by bouncing and rolling it back and forth a few feet. It is important that you do this the same way each time, I prefer to push the car down and allow it to rebound on its own (we also set the rebound and compression damping to full soft). 

3) Care for the threads. It is critical that the threads on the shocks are clean before you make any adjustments, dirt and grit not only make adjustment difficult, it can damage the the threads. If your suspension setup demands that you preload the spring to achieve the desired ride height, it can become very difficult to turn the spring collar. Resist the urge to grease the threads as this will attract dirt and nastyness. We have been experimenting (with good results) with using a dry graphite lube. This provides plenty of lubrication to the threads without making a mess.
We use a lube like this, it also comes in smaller bottles and spray cans. 

4) Tender springs. Certain spring rates and lengths make the use of tender springs necessary. Sometimes when trying to achieve a low ride height, the spring collar is backed off so far that when the suspension is in full droop, the spring becomes loose. Adding a tender spring to the mix will keep the main spring in place and prevent it from making noise or damaging the shock. If you need some tender springs, just give us a call and we can get you setup.

Set of 4 tender springs and spacers.
I could probably write a book about suspension setup and adjustments (there are already several on the subject written by folks much smarter than I). I believe this entry has gotten long enough as it is. If you would like more information you can give us a call, email us at, or you can do some research on your own (Carroll Smith's Tune To Win is an excellent resource).

1 comment:

mays effect said...

Late and rather unaccessary comment.. But > Tender springs serve a much greater purpose than just helping the main spring at full droop as described. That is what a helper spring is for. Often confused but not the same. Tender springs generally add to the overall compression force, where as a helper spring is so low of a rate it will add an insignificant amount of pressure only high enough to keep the primary springs afloat when completely unbound.