things you should know about coilovers

Lately we have read quite a few incorrect comments online about suspension and coilovers, so we decided to write something about it.

Firstly, let’s go over a few suspension basics. There are a few popular suspension arraignments, mainly the Macphearson strut, double wishbone, multi link, and solid axle. Basically every modern car is going to be one of these designs, but that’s not what this post is about. Regardless of the layout, there will be a spring to support the weight of the car and resist roll and pitching movements, and then a damper, or shock absorber, to control the motion of the body and suspension. Without shocks, the body could oscillate freely on the springs and that would not be good.

When we talk about coilovers, we mostly mean an aftermarket suspension setup that usually has a variety of adjustments. However, as a general term, many oem suspension designs use “coilovers.” Coilover simply means a coil spring over the shock. Like this:

Here is a more adjustable version:

The second image is generally what people mean when they refer to “coilovers,” while the first image is often called a strut/shock and spring combo. They both are “coil over” suspension but we will stick to the common terms.

At a glance, we see a few differences. Firstly, the springs are different. The second set has smaller diameter springs, which are a standard size and can be interchanged easily with softer or stiffer parts. The shock bodies are also threaded, so the perches can be adjusted up and down.

What good does this do? Well, besides the obvious ability to adjust ride height, we can also change the springs, without changing the height. A helper spring (that second, smaller spring in the pictures), allows us to do both without having excessive preload or unseated springs at full droop. The other benefit of adjustable perches is the ability to corner balance the car.

Ideally, for the best handling, a car would have equal left to right weight distribution (unless you only wanted to, say, turn left). In reality, this is not the case. One side of the car is going to weigh more than the other because of things like drivetrain layout, the battery position, the driver, etc. If you are working on a race car, it is good to get this balance as close as possible as the car will be driven.

But most cars are not perfectly balanced, and even if one was, after just bolting up a set of suspension there would be some uneven preload from one corner to another. We check this by putting the car on four scales to measure the weight distribution, and then the suspension can be adjusted to fix an imbalance .This process is a key part in making a car handle well, and is a huge benefit of having an adjustable coilover suspension. With standard struts and springs, there isn’t much you can do (although moving weight around the car and shimming the top mounts are possibilities. Adjustable sleeves are also available for many standard struts).

The other side to this, is when an adjustable set of coilovers gets installed, but then is NOT corner balanced. The result will frequently be worse off balance than if just standard struts/springs were used, and potentially dangerous and inconsistent handling behavior. For anyone who buys a set of height adjustable coilover suspension, corner balancing should be considered mandatory. It is not “just for racing.” Some of the symptoms of very uneven corner balancing can include the following.

  • The car understeers turning one direction, but oversteers going the other.
  • Car prefers turning one direction only.
  • Even with a straight alignment there will be pulling to one side, especially under braking or acceleration.

That left-to right handling difference is the main reason for corner balancing, because we usually want a car to behave the same turning in either direction. Imagine that whenever you went around a right hand corner the car wanted snap around abruptly. That might be a good way to end up in the guardrail on the highway.

When it comes to height adjustment, you might notice there are some suspensions that only have adjustable spring perches, while others have a lower threaded mount, like this:

On the surface, it seems like a great idea- you can adjust the ride height without changing spring preload or changing the ratio of bump to droop travel. There are a few problems with this, though. The main issue is that the suspension can only compress so far before the tire runs into the body of the car. In reality, if you take one of those super adjustable coilover sets, and lower the height way down using the lower mount, yes, the shock will still have the original amount of bump travel, but the tire will probably end up hitting the fender, the liner, or maybe a wiring harness, The axles might contact the frame, and all sorts of other bad things can/will happen. MotoIQ has a good article about such a car here, and here is a wiring harness that was chewed up from tire contact:

So unless you are ready to cut apart the car, relocate things like wiring harnesses, and can fix the suspension geometry issues caused by over-lowering, that “independent ride height adjustable” set of coilovers might not actually offer any benefits. A well designed set of suspension will run out of shock travel just before the tire hits anything, and they also tend to have more overall travel, which is a good thing for both ride comfort and handling. The main benefit of the double adjustable “feature” is that it makes it easier for a suspension company to use the same shock for a lot of different cars, without having to put much thought into appropriate travel or damping specific for that vehicle. When installing a set of this type of coilover, it is a very good idea to remove a spring and jack up the suspension all the way to the top of the travel to insure the tire is not going to rub.

The next thing found on many coilovers is damping adjustment. Depending on the shock, this can be really useful. How the damping should work depends on quite a few things: the weight of the car, the unspring weight, the tires, the spring rate, the road/track condition, and what the driver likes. So there is really no one perfect damping curve for any given car and suspension setup. The best we can hope for is to have something the driver and passengers like and results in better lap times. An adjustment knob or two can really help fine tune both ride and handling. Damping adjustment will also allow a wider range of spring rates to be used before re-valving is necessary. HOWEVER, the person turning the knobs needs to know what they are doing, and the knobs need to do what they are supposed to.

There are many good suspensions that do not have damping adjustment, that are well liked and perform well under a wide variety of conditions.. Those yellow struts and springs in the first picture, which are Bilsteins tuned by Racecomp Engineering with their matching springs, are a good example. No adjustments- just install and enjoy. On the other hand, there are many suspensions with a lot of knobs that do not work well. A good rule of thumb is that the cheaper a shock is, the fewer knobs it should have. Don’t get fooled by the $1000-1500 double-adjustable coilovers; when they wind up on a dyno it’s not uncommon for those knobs to not do what they are supposed to, and the shocks will often not match. So even though the are set at the same “click,” the left and right dampers are behaving differently.

Like we mentioned, the damping required depends on a variety of things, including the spring. With stock/worn out shocks, installing lower and stiffer aftermarket springs is usually not ideal. The right amount of damping for good handling is usually higher than what is best for ride comfort, so while stiffer springs are usually better for performance, the resulting under-damped condition is not. Aftermarket lowering springs are cheap on their own, but in many cases should be paired with a better shock.

I believe that covers most of the basic differences between what are called struts and springs, and coilovers. For someone looking to change their suspension, it’s important to consider how it is going to be used. For a daily driven car, a good strut and spring combo will often be more durable, more comfortable, and possibly less expensive. When handling is the priority, the additionally adjustments of some coilover systems can be worthwhile, but they come at a cost. Coilovers that ride well on the street, perform on the track, and will remain trouble free for years exist, but they cost more money. It is also important to consider that the setup and alignment for coilovers is more involved. A standard alignment shop will often not know what to do so it is important to find a place that can properly align and corner balance coilover suspension.

I suppose next time we can talk a little more about damping and some suspension brands.. But for a short list of stuff that is both good and fairly inexpensive, start with KW, Bilstein, Koni, and AST. There are also companies that specialize in certain makes and have their own version of products, like the previously mentioned Racecomp Engineering. Almost everything they offer is based on a KW or Bilstein product (and we used some of their photos for this article).


History of the Buttonwillow Track Record

The first Super Lap Time Attack event in the US was way back in 2004 at Buttonwillow raceway. I wasn’t there, but if you were to track down an old guy like John Naderi and get him liquored up I’m sure he would tell you all about it.

Since then Buttonwillow has been the benchmark for fast time attack cars in the US. Sometimes I wonder what would have happened to time attack if they had picked a different track. Something not in the middle of nowhere, with better facilities and nearby hotels and entertainment (spring mountain?). Would we have something more like WTAC by now or would RTA have imploded earlier and set things farther back. Maybe the cheap track rentals and $40 motel 6 rooms help keep things accessible. It’s not Eastern Creek or Tsukuba, but  Buttonwillow is what we have.

Ok back to that first Superlap in 2004. The Sun Auto Cyber Evo was there with Tarzan driving, and crushed the competition with a time of 1:48.906. The next fastest time was 1:54.2 (also by Tarzan, he was driving a bunch of cars that day).

1:48.906 – Tarzan Yamada – Cyber Evo – 2004-2007

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Top Times at Buttonwillow CW13

Yeah, I know I have the top 40 already, but that leaves out many of slower categories and class records. So here are the top 5 in each class. Some of them go way back

Unlimited AWD

1 – 1:38.967 – Jeff Westphal – GST Impreza – 11/14/14 SLB
2 – 1:40.417 – Cole Powelson – Lyfe Motorsports GTR – 11/14/14 SLB
3 – 1:41.046 – David Empringham – Sierra Sierra EVO – 11/9/10 SLB
4 – 1:41.309 – Mark Jager – Jager Racing/ Yimisport STI – 11/11/16 SLB
5 – 1:42.594 – Ken Dobson – Professional Awesome EVO – 11/11/16 SLB

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New records at GTA Superlap Battle 2016

SLB was another good one this year and there are some new track records, here they are

Street AWD
new record: 1:49.864 – Cody Miles – Airlift STI
old record: 1:50.206 – Jager Racing sti

Limited FWD
new: 1:49.834 – Chris Boersma – Boersma Racing Civic
old: 1:51.789 – Will Au-Young – PZ Tuning RSX

Unlimited FWD
new: 1:43.365 – Will Au-Yeung – PZ Tuning RSX
old: 1:45.585 – Dai Yoshihara – Spoon Sports Civic

Full results can be found here on the GTA website

All track records have been updated here

GTA Superlap Battle 2015 unofficial results

Been watching facebook and the live feeds and here’s what I’ve come up with. New records in bold.

Unlimited RWD:

01 – 1:41.925 – Cody Kishel – Corvette Z06
02 – 1:45.541 – Graham Downey – Blacktrax Honda S2000
03 – 1:49.958 – Tom Tang – Honda S2000
04 – 1:57.468 – Danny George – Mazda Miata
EX – 1:56.700 – Ryan Novak – Ferrari 360

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Buttonwillow time attack track records

Unl RWD: 1:37.520* – Billy Johnson – FXMD NSX – 12/8/13 ETA
Unl AWD: 1:38.967 – Jeff Westphal – GST Impreza – 11/14/14 SLB
Unl FWD: 1:43.365 – Will Au-Yeung – PZ Tuning Civic – 11/11/16 SLB

Ltd RWD: 1:44.456 – Cody Kishel – Excelsior Corvette – 11/14/14 SLB
Ltd AWD: 1:42.694 – Jeff Westphal – Pro Awesome EVO – 11/12/15 SLB
Ltd FWD: 1:49.834 – Chris Boersma – Boersma Racing Civic – 11/11/16 SLB

Str RWD: 1:48.802 – Tony Fuentes – Honda S2000 – 11/12/15 SLB
Str AWD: 1:49.864 – Cody Miles – Airlift STI – 11/11/16 SLB
Str FWD: 1:52.122 – Chris Boersma – Boersma Racing Civic – 11/14/14 SLB

Ent RWD: 1:55.518 – Dom Bautista – Honda S2000 – 11/12/15 – SLB
Ent AWD: 1:56.325 – Craig Peyron – Outlaw STI – 11/14/13 SLB
Ent FWD: 2:01.314 – Pradana Wilianto – Godspeed CSX – 11/14/13 SLB

*some people don’t like that FX did it at an extreme speed time attack event instead of SLB/GTA or RTA. Their next fastest time is 1:40.379 at SLB 2012, which would also be a URWD record.

Unlimited Class at Superlap Battle

Unlimited Class is where the shops, race teams, and manufacturers go to see who can set the fastest overall lap time, with very few rules- basically, it has to be a car with a vin number (no track day specials like a radical), and depending on the event you may have to use a DOT approved tire. Way back in 2007 Nob Taniguchi took the HKS EVO out for a 1:43.523, which really kicked off the unlimited class arms race. Sierra Sierra Enterprises built their EVO and Factor X upgraded the NSX with the goal of re-taking the record. SSE finally beat that time in 2010 (1:41.046), only to have it taken away by Factor X the next year. FXMD is the current overall record holder, with a time of 1:37.520 they set last year. Right now I’d say there are very few cars capable of beating that time, and most of them are overseas. Well, that’s enough history for now, here’s what happened this year: Continue reading