legacycentral bbs

I have had my car for 2 weeks now and the suspension was shot when I got it. So, I went out and bought some Tein coilovers from a GC8 and installed them yesterday.

The biggest pain in the butt was removing the back seat! The actual install of the coilovers was smooth and the end result is amazing.

http://bbs.legacycentral.org/viewtopic.php?t=17535

^^^Those are some pics of it. This is a direct install with NO extra work needed. Just take out the stock and bolt in the Teins.

Did you buy them new?

No, I bought them used from a Japanese parts Supplier from Toronto, Ontario. They are in very good/clean conditiona and the ride is amazing with virutally no body roll.

Do those need to be rebuilt every so often? You should hang on to the old parts if they do so you can keep driving while rebuilding or get some cheap newer parts if the old ones are too shot.

How high can they go?

Steve

My good friend has had them in his Toyota MR2 for the last two years. They are holding up quite well as he autocrosses and uses his car as a daily driver.
That is one of the reason I went for the Teins. I plan on doing some autoX aswell. But I put the old ones in the attic of the garage. The rear struts are of no good to me though, they have no fluid in them.

The Teins are rebuildable aswell.

They can go about the same height as stock which is good for winter.
I would recommend this set up to someone that has plans to autox their daily driver.

I'd keep it at stock height until you get other work done suspension wise.

Lowering the car without the proper measures, actually increases body roll, thus requiring an uber stiff spring rate to counter this.

Handle the body roll, lower it to the point you want it, and you can just use softer springs and stock sway bars and handle on rails.

Thanks for the Advice.^^^

I am going to AutoX this upcoming Sunday so I will get a true feeling for the body roll of the car.

It's unlikely you'll get much, if any body roll on a smooth auto-x course.

In fact, if you only drive smooth turns without high speed, slalom-esque sharpness, then your setup would be fine. 90% of drivers feel this way about their suspension. It'll handle AWESOME on any smooth tarmac, super stiff springrates will do that for you.

It's when the going gets rough and fast that you run into problems. The spring rate can only handle the heft of a 3000+ lb car at so much a speed. When you toss the car from apex to apex at 75 and 80 miles per hour, that stiff spring rate is going to hinder performance more than help it. Such high rebound, coupled with such a tall roll-moment is going to sling-shot the car over the roll center and momentum will get the best of you. You'll find yourself sliding sideways on a highly unpredictable scale. Because the suspension acts so erratically (in terms of conditions), what happens in one turn won't likely happen in the next. Not without those proper measures at least. When your suspension works better, the car works better. Simple formula really, and it's amazing to me how "suspension guru's" don't often know about proper dynamics when it comes to turning.

Think of it like a car doing the slalom. It gets harder and harder, the faster and faster you go. You could take a single left turn at 75mph, but link that left to a right, and another left, and that 75mph seems like a pipe dream.

Anyone can make a car corner on a flat, smooth, perfectly paved section of road. It's significantly more difficult to make it corner over the rough stuff.

There is a small enomaly in suspension technology that is a purely physical property of automobile design. This enomaly is known as Roll.

Imagine, if you will, the car's Center of Gravity. Just picture the lateral line going through the car at it's center most point. Got it? Now imagine, on the same plane, the car's roll center (the point that the body rolls around, this is based solely on suspension dynamics). The Roll Center is not the same as the center of gravity. Imagine the lateral line going through the car.

Now you've got 2 lines through the car. The bottom one is the center of gravity. The top line is the roll center.

Measure this virtual distance. That number is called your "Roll Moment". Imagine the roll-moment as a lever. It's the leverage that the mass of the car has to create roll.

Now, lower the car. The Center of Gravity drops, but the roll-center stays the same. You have increased your roll-moment, and in turn increased the body roll. THIS effect is countered by serious spring rates to help bring handling back to stock. This is perfectly fine if you never plan on hitting a bump, or tackling high speed switchback style turns (like a slalom for example). I already made mention to the increased rebound causing issues like that.

Now, how do you fix this? Roll-Center adjusters. This is an arm replacement part that allows you to drop the roll-center (and thus lower the roll moment) of the car. Now that you have brought the roll moment back to stock height, you've correctly lowered the car. Since the CG is lower, and the roll moment is stock (or better), the car will handle flatter and faster. You can get away with softer spring rates, which aid in slalom turns (because the rebound isn't as harsh, it doesn't skip the car from apex to apex, but rather rolls it smoothly over). The softer spring rate also helps in bumpy road situations. Because the bound is softer, you aren't bouncing off of imperfections in the road, but rather absorbing them. The suspension geometry changes are predictable as the wheels track the ground rather than becoming unpredictable as the wheels bounce and deflect off of every undulation in the road.

Let's do a quick, real-world simulation.

4 cars, all identical except for suspension.

1 car is stock (#1).
1 car is lowered with stock spring rate (#2)
1 car is lowered with stiffer spring rate (#3)
1 car is lowered with roll-center-adjusters and a slightly stiffer spring rate. (#4)

They all run the slalom. Car 1 is slower than #3, and #4. The increased roll-moment hinders #2 and makes it slower than #1. #3 is faster than #1, simply due to the increased spring rate keeping the roll in check. As the car passes its limits, it becomes unpredictable, but livable on smooth streets. Car #4 is the fastest of the group. The suspension behaves exactly like the stock setup does with slightly stiffer springs, the car is also lower, keeping it flatter in the turns.

Hit a bumpy road slalomn. Cars 2, and 3, both flail wildly and perform hideously slowly. The bumps simply overcome what the car is capable of. #3 becomes the slowest car in the group, #2's somewhat forgiving spring rate help, but the suspension quickly bottoms out and the car bounces off of the bump stops. #1 is faster than it's other 2 modified brethren thanks to suspension travel optimized for the stock springs. #4, however, takes the cake. It's stock geometries and effective rise rates help keep the car in check while the body doesn't excessively roll thanks to the softer spring rate than #3. The spring rate keeps the car off the bump stops, but takes full advantage of the available travel.

Suspension technology is a fascinating area of vehicle dynamics. That and braking are the two things about cars that amaze me the most.

Sorry for the long winded post, but I figure it would be helpful for everyone.

Phil

wow. i read half of that and got hungry for bread.

Sorry

Very long post but I enjoyed reading it.

I understand it, however I still need to save up money in order to buy the rest of the suspension components. lol

Heh, started to read, then i had to poop, and went to bed.

MK

Shane wrote:Very long post but I enjoyed reading it.

I understand it, however I still need to save up money in order to buy the rest of the suspension components. lol

Glad someone enjoyed it

I definately agree in doing it all right. When I get new struts/springs, I'm also going to go with some roll center adjusters and an ALK. Gonna cost me a good bit, but it'll be worth it.

I do suggest that those interested in suspension workings read my post. I tried my best to make it interesting and easy to understand.

is it worth the read?

Yes, THAWA. It is. Read it.

BAC5.2 wrote:...When I get new struts/springs, I'm also going to go with some roll center adjusters and an ALK. Gonna cost me a good bit, but it'll be worth it.

...

OK. In all the suspension research I've done, I have not seen any product called "roll center adjusters." Who makes them, where do you buy them, what do they cost, and how are they installed?

[time out for google search]

A quick google search [keywords: subaru "roll center adjusters"] shows only a few hits, and only a Whiteline product for AE86 Corolla.

You should add images to your post, there are plenty available. The roll center location will change when you lower the car.

MK

What are they?

Basically spacers that push the lower control arm to drop the roll center, and thus decrease the roll moment.

The Roll center remains constant through the suspension travel, since it is a byproduct of suspension geometries. The suspension is arcing around a point, and the roll center is based off of that point. It's the point that the car will rotate around based on suspension layout and geometries. Reguardless of the position in travel, the roll center is constant. The Center of Gravity is what changes through the suspension cycle.

When you conventionally drop a car, you make the car sit in it's travel more. Put 500 pounts of sand at each end of your car, and it puts you in the same place (not really, but you know what I'm saying). The roll center remains where it was at stock height, but the center of gravity is lower.

The roll center adjusters drop the lower control arm, effectively changing geometries which lowers the roll center.

The first picture I found was this one (for an AE86), they look the same for most applications. I'm sure they also make control arms that are already have relocated bolts mounts to effectively be roll-center-adjusted. That'd be the ideal way to do it, as more bolts often causes more problems.

cool info, but how would a car with the stock center of gravity and lowered roll center fair against the other 4 (I assume better than the completely stock one)

Good question. I'd imagine it would be a completely circumstantial situation. Some cars are designed differently than others, so it might yield GREAT benefits in one car, and might SNAFU another.

hmm, so like you're saying if the car already had the roll center fairly close to the center of grav, and you installed roll center adjusters that made it lower than the center of grav it would mess it up. Right? But otherwise anytime you can get the roll center as close to, but not lower than the center of grav you're good right?

I'd really like to keep the stork ride hieght, or maybe a little taller, but really dont want to roll as much as it does.

You got it Hardy!

A REALLY good example is the Koenigsegg 8C. The roll moment is almost zero under no-load. The car will scrub sideways indefinately before the body will roll.

Like I said, ideally, you want the LCA's lower to change geometry to reposition the roll moment closer to stock distance on a lowered car. On a stock height car, lowering the Roll Center would reduce the roll moment, and as long as the roll center isn't below the CG, you'll be fine .

However, it's difficult to work out the amount you'd need to drop the roll center without a LOT of time and effort. If you want stock ride height or taller, get some beef sway bars and use that to bandaid the problem. It'd be cheaper than getting some RCA's custom made.

I'm not a HUGE fan of sway bars when it can be done properly by re-designing the suspension geometry, but sometimes a sway bar is the easiest and, pretty much only viable option.

BAC5.2 wrote:I'm not a HUGE fan of sway bars when it can be done properly by re-designing the suspension geometry, but sometimes a sway bar is the easiest and, pretty much only viable option.

Yeah, considering I have yet to see any roll center adjusters for a Subaru.

You'd think that Whiteline would have one, considering how long the Australian market has had high performance Subarus.

The Whiteline ALK is, basically, the roll center adjuster. It drops the lower control arm a bit and brings it back slightly which increases caster and at the same time lowers the roll moment. An ALK on stock suspension would probably be a really good thing to have, and would make everything a bit better.

BAC- that essay was awesome. I'm wondering though, about all those alphabet performance cars; 2.5rs, prot mp3, civic si, and the like that are factory lowered. Does the factory accomodate for the changed suspension geometry? Do they just increase swaybar stiffness and strut stiffness and call good enough?