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So the grease monkey managed to install your fancy coilover shocks without breaking something or triggering the dreaded HID-leveling error icon. The camber and toe all seem reasonable at-a-glance, but the car has yet to transform into the corner-carving beast that you hear folks gushing about. As expected, you got a lower ride height and a bumpier ride. But the car feels strange, even a bit sloppy. You begin to question whether all this effort and sacrifice to practicality was worth it.<P>

These, my IS300 brethren, are the common symptoms of bad suspension setup after a coilover shock kit install. The unfortunate fact is that badly-setup coilover-equipped suspension is more the rule than the exception. For this reason you may find that many coilover-equipped cars fail to achieve the level of performance of even mild factory performance kits (such as Sportivo kits and L-Tuned parts/cars). Frankly, this is an embarrassment. Worse yet, many people fail to appreciate their own incompetence and instead end up blaming the parts, saddling them with ill-deserved reputations.<P>

Never to leave an injustice alone, this is the first of a series of articles in which I touch on some of the issues that need to be considered in the selection, installation, and fine-tuning of coilover shock kits for the IS300.<P>

<B>Catch-22 and the Cursed Blessing: Adjustability and Kit Calibration</B><P>

Many of the available coilover-shock kits offer fundamentally better architecture and increased oil volumes over stock and stock-replacement shocks. However, the hallmark feature of most coilover shock kits is the ability to adjust it to meet your specific equipment, terrain, and driving ability/aggression/preference needs. But adjustability entails adjustments, and adjustments mean selecting a single set of optimal settings from all the permutations of sub-optimal settings. Hence it's been said (semi-facetiously) that as the adjustability of a race car is increased, the ways you can arrive at some "wrong" setup increases geometrically. For this reason the lesser-endowed but adjustment-free kits often compare quite well against the average coilover-equipped setup you’ll find on the streets, which sometimes lead people to invest an inappropriate degree of regard to package tuners. Whether out of the same misperception or actual appreciation of the true nature of their customers, some aftermarket shops will recommend non-coilover shocks and kits with fewer-to-no adjustments over coilover shocks.<P>

Despite this, the fact remains that an appropriately-chosen and well-setup coilover shock kit-equipped car will outperform most (if not all) of the no-fuss kit-equipped cars. Most no-fuss kits are essentially no more than mild recalibrations of the stock equipment. (Their mildness derives both from the limitations of the stock architecture and the wide audience for which these kits need to appeal to. It doesn’t help that the IS300 is marketed as a Lexus, which adds to a kit-tuner’s willingness to err too far to the soft-and-cushy side.)<P>

Hoping to combine the idiot-proof nature of low-fuss kits and the attraction of coilovers, Zeal, Tanabe, and Tom’s offer reduced-adjustment coilover shock kits. As you all might know, some of these have been received quite warmly throughout the general aftermarket community. So are reduced-adjustment coilover shock kits the best answer to the majority of IS300 enthusiasts?<P>

Currently, no.<P>

The IS300 is both blessed and cursed by being a Japanese-made car with a JDM automotive sibling, the Altezza RS200. The existence of the RS200 as a popular sporting car in Japan is what gives the IS300 its wide selection of aftermarket performance parts. But in converting the RS200 into an entry-level-luxury contender against the BMW 3-series, the IS300 gains ~300 pounds, which would be 10% more mass. Further complicating the situation is the fact that the additional mass isn’t evenly distributed throughout, but rather concentrated across the front to produce a notably different front-to-rear weight ratio, a 54F/46R to the RS200’s theoretically perfect 50F/50R. A quick calculation reveals that more than 250 additional pounds are carried by the IS300 front suspension.<P>

As you might have guessed, the problem is that all Japanese-made coilover shock kits are built calibrated for the lighter and better-balanced RS200. More than 250 additional pounds on a single axle is no laughing matter when it comes to spring and damping rates. Whereas significantly-adjustable coilover shock kits can be adjusted to accommodate the higher spring rates you can obtain to convert the RS200-spec kits to something more suitable for the IS300, you’re pretty much up-a-creek with reduced-adjustment coilover shock kits. Alternate spring rates are rarely available for them, nor can the limited damping adjustment accommodate the higher rates with the aplomb of the significantly-adjustable coilover shocks, if at all. It might not be obvious if you have not experienced any better, but one hard romp in a correctly-sprung and damped IS300 will instantly reveal all that you’re missing.<P>

Most kit and part manufacturers are far from truthful when quizzed about whether their products are truly calibrated for the IS300. As long as the soft-core and undiscriminating North American consumers don’t know any better to demand more, they couldn’t give a rat’s ass putting in the minimal effort to develop and stock an IS300-specific tune, or simply telling the whole truth. Being that this is the case, the way to tell if a part or kit is calibrated for the IS300 is to check for the existence of a JDM equivalent for the RS200. Use a translator site such as Babelfish if necessary. You will usually find spring and damping rates/curves specified right off-the-bat, which is telling compared to the vagueness of how the comparable products are usually sold in the North American market. Take down the appropriate part number(s) and specifications. Rarely will you find the specs for the IS300-marketed kits/parts listed, and more likely you will have to either call or E-mail the distributor. If the specifications are the same, it’s obviously the RS200-calibrated kit. If the part numbers are the same, the same thing holds.<P>

If you’re convinced that you would be better off with reduced-adjustability, the better bet is to go with the non-coilover kits specifically calibrated for the IS300, which would be the L-Tuned kit, L-Sportline kit, and even the Sportivo kit for the JDM Altezza Gita. (Although that Sportivo kit isn’t designed for the IS300 per say, the JDM Altezza Gita is actually very close to the IS300 in both weight and balance.) Even piecing together a setup from the selection of springs and shocks truly calibrated for the IS300 is better than running the wrong spring and damping rates of a RS200-calibrated kit.<P>

But as you shall see in my next column, there exist very compelling reasons for selecting even a RS200-calibration coilover shock kit, as long as there is availability to alternate spring rates and enough damping adjustment range/fineness to accommodate that.
 

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Hi - I like this article and would like to see a series continue. Any thoughts?

I have been taking some driver school with my IS and love its turn in precision and supple feel. I upgraded to the Hotchkiss sways ( it had a lot of body roll) since I didn't really want to lower the car right away. I'm getting ready to take the next step and am trying to decide what kind of springs to pick. I thought about going full adjustable, but having done the race car thing I know it takes a lot of effort to sort it out. I'm having so much fun driving - that I don't want to spend my sessions tuning.

Any advice for a decent set of springs that don't make it too low. Hotchkiss seems like they have a decent kit, but I don't understand how they could lower the car yet make the rear rate softer.

Thanks
Don
 
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