AZ IS350

I've been thinking about lowering my 350 but really I'm ok with the fender gap in the back. It's the huge gap up front that bothers me. Is it possible to put lowering springs just on the front and keep the rear stock? What potential problems would it cause and how do you think it would look? I think it would give it a more aggressive stance and help even the gap with the back. I was thinking maybe a .8-1" drop. I know I could probably do this with adjustable coilovers but I'm low budget.

ahohnstein

I'm curious about this as well. I just noticed the other day that the gap appears to be visually larger in the front than the rear. I've never been one to mod a car but I'm seriously considering the Eibach springs.

lobuxracer

iTrader: (2)

The sport suspension uses stock height in the back and lowers the front by 10mm. Yes, you could lower just the front if you want. It will increase the caster a little, but if the factory did it, it shouldn't hurt the geometry much at all.

al503

I think it would look much better. Potential problems: the spring rate differential between the stock and the new spring. If the new spring is stiffer, you'll tend to increase understeer. If it's softer, then you'll increase oversteer. You probably won't notice this until you get closer to the limits though.

The new Tein h-tech drops the front by about 1" and should be available for less than $200.

knihc2008

iTrader: (1)

The Eibachs deliver the same drop for about the same $ right? I'm wondering which one will deliver a smoother, less jarring ride. Also am worried about scraping issues, etc. Wouldn't putting springs only on the front make the front overhang actually lower than it would be if you put springs all around?

lobuxracer

iTrader: (2)

Any spring that drops an inch better have a significantly greater rate or you'll suffer dramatically increased body roll. After working the numbers on a few Toyotas, it's pretty clear to me they don't like to be dropped from a performance perspective. Roll center drops like a rock when you lower most Toyotas, and roll couple gets really long really fast, so you need very stiff springs to counter the effect.

AZ IS350

Thanks for the info Lobux, you seem knowledgeable. How does the sport suspension get the 10mm drop? How pronouned do you think the increased body roll would be under normal driving conditions, and wouldn't progressive springs help counter that under aggressive conditions?

al503

progressive rate springs will actually make it worse. You want linear rate springs.

lobuxracer

iTrader: (2)

Agreed. Progressive springs are almost never a good compromise.

For normal everyday driving, the visual performance crowd has proved it is possible to lower cars until the suspension design is completely compromised and unable to deliver any of the performance the engineers put in it.

As soon as you ask the car to change direction with authority, you'll notice the problem. The grip will not be as good as stock, and your cornering speed will be much lower than stock. Given the IS is delivered with a decent set of tires (truly amazing for Toyota), there's not a lot of room to make up for the effects of the change.

The OEM sport suspension drops the front of the car 10mm. The rear height remains the same. That alone tells me it isn't a good idea to lower the rear of the car. Toyota do this with springs and shocks on all four corners for the IS, I checked with Lexus parts and those are the only different parts for the sport suspension.

clubfoot

lobuxracer, wouldn't a matching set of roll/sway bars make up for the lowered roll center and still maintain a decent ride?

lobuxracer

iTrader: (2)

Only to a point. If the rollbars are too stiff you lose the independence of your four wheel independent suspension. It's a tough balancing act. It's generally far easier to jack up the spring rate, but then you have wheel compliance issues and you need stiffer damping to control the more powerful springs.

The problem is the objective is to keep the tire in contact with the road and balance the weight of the car as evenly as possible across the four contact points. Stiff springs and the requisite stiff damping mean it is more difficult to keep the tire from skipping over the tops of bumps and failing to follow the contour of the valleys. Stiff sway bars mean as the car rolls, you also take weight from the inside tire in hopes of better balance. As the roll gets too stiff, the inside wheel just wants to raise off the pavement and load all the weight to the outside. So it's a big balancing act.

The most important part is to get the roll center reasonably close to the center of gravity because the distance between those two acts like a lever on the suspension. If you lower a Scion tC two inches, the roll center is actually below ground and the roll couple is absurdly long. So you have to have really stiff springs, stiff dampers, and stiff swaybars. Then you lose wheel compliance over bumps because everything is so stiff. It works great on very smooth surfaces, but that's not the world we live in.

I once almost went into an intersection because I was braking over a washboard surface and the wheels kept locking because they couldn't follow the contour of the washboard. So the ABS was fighting me, and the car stopped almost into the intersection instead of making a nice smooth controlled stop. Everything has it's bad days.

So, it's a lot better to have the suspension working right than looking good if you want the car to mechanically perform. FWIW, all my friends who track their Supras swear by the factory ride height (with big swaybars.) I'd bet the IS is pretty similar. The factory did a bunch of things on the ISx50 to prevent dive and to increase the tendency of the chassis to understeer while braking, just like they did on the Supra.

linh811

so the final answer is that it is "ok" to drop only the front by ~1"? I'm satisfied with the gap in the back and would also only like to drop the front.

lobuxracer

iTrader: (2)

It'll be fine for everyday driving. I wouldn't take the car to TWS like that though. Or even Motorsport Ranch for that matter. You might be disappointed.

linh811

thanks.

thats why i have the SV and R1

AZ IS350

Well ya kinda got me a little skeered to try it now. I don't want to compromise too much handling just for aesthetics. Maybe I'll save up for adjustable coilovers....