snowdrift

My car is a 1990 S5 T2 on 24k miles. completely factory stock (read below)

since i bought it a few months back I've been trying to tighten up the handling. Initially it felt very unstable at high speeds like the car was floating, this was particularly bad changing lanes on the motorway where it literally felt like the car was moving around underneath me. I put it on the ramps to start checking it over, didn't seem to be any play in any of the bushings apart from the rear shocks so i changed these with a set of HSD Monopro coilovers (not the greatest but also not eBay crap) because that's what where available immediately and it was quite scary to drive. This fixed the floating but i'm still getting a load of body roll and the steering is far from sharp.

Firstly the body roll. I'm running 7kg/5kg spring rates on the coilovers which i initially thought seemed real low, my (DC5 type R was running 12kg/11kg) but researching seems to suggest that's about normal for street FC. The car isn't exactly slammed, just a bit lower than stock so i don't think its a roll centre issue but i could be wrong, still learning a lot about suspension setups. Next step is changing the sway bars for racing beat ones front and back but i'm skeptical how much that can fix. I still feel like the car rotates around me slightly, even on slow corners just driving around town, I thought maybe the DTSS bushings were shot but that would be odd for the mileage. I will be changing these for the racing beat eliminators anyway though soon.

Next the steering issue. Now this could just be because its an older car and that i'm not used to but the steering seems very vague when cruising straight or small turns, however when pushing it harder on a corner it seems to tighten up. There also seems to be a larger than "normal" dead zone in the steering before the wheels start to turn. had a mechanic look at the rack as i rocked the steering and he says he cant see anything wrong and that it might just be because its an 80's car. I've heard a lot of people say how tight and responsive the FC is so i'm not inclined to believe that. Would surprise me if the rack is worn on a 24k mile car .

Anyway i thought i'd post up here in case anyone can shed some insight or think if something that I've missed. It's quite hard to put into words how it feels to drive but the car doesn't fill me with confidence when pushing it.

Thanks for taking the time to read, any suggestions are appreciated.

ColinShark

Yeah, FC's have pretty tight steering. It should not feel "floaty".

My guess is that your bushings are in poor shape. There are a lot of bushings.

The sway bar has bushings in the links and has mount bushings. The steering rack has mount bushings.

Control arm bushings. All the weird rear suspension bushings.

Just start replacing things. Personally, I like the Mazdaspeed / Mazda Competition rubber parts because they are stiffer without the drawbacks of sliding race-style bushings or bearings.

In regards to the DTSS, it's calibrated for 80's tires. With better tires and higher cornering forces, it doesn't behave in the way Mazda intended.

j9fd3s

iTrader: (3)

before you go changing stuff, you should just get the car aligned.

the toe in has a HUGE effect on how the car feels, and the factory setting is pretty numb. for a street car i like these settings:

Front; Camber -0.5 Degrees, if you really drive it hard, it will want more.
Castor, usually this isn't adjustable.
Toe in: Zero toe feels best. it really sharpens things up.

Rear: Camber unless you have camber adjusters it kind of is what it is, but the factory setting around -1.5 is kind of the target
Toe, this makes a HUGE difference. the alignment bolts are marked, so if you can start at zero, and then try 1 tick mark toe in, and then 2 tick marks in, you just use the one you like best.

zero toe turns in best, but it really wants you to be on the gas before the apex, which is not always possible on the street. adding more toe adds more stability, and the stock setting is enough that you can be spinning backwards into the bushes and it feels fine.

your bushings are fine, there are only 6 of them and they are intentionally small, so they don't deteriorate and cause weird issues.

Rotary Alkymist

I would argue that you should change stuff before an alignment. You can't set alignment unless everything is tight. If you start doing suspension work you will inevitably need another alignment. That seems like a waste of money at this point.

TonyD89

iTrader: (10)

I would agree, an alignment is $90 around here. If you think you might want to change bushings, ball joints, anything that effects alignment, do as much as you can all at once so you don't pay for multiple alignments.

eage8

iTrader: (9)

there are really only 4 bushings in the back of the FC that will affect anything, 2 of which are the DTSS bushings. I wouldn't be surprised if they're causing your issues. (the other two are the front rear control arm bushings on the outside) everything else is ball joints or spherical bearings for the most part.

I would replace the DTSS bushings and then go get an alignment at a shop that actually knows that they're doing, and ask them to give the suspension a once over to check everything.

Rotary Alkymist

I would argue that as well. There are plenty more than 4 things in the rear that will cause handling issues. Check ALL of these things:

Control links
Rear stabilizer bar links
front stabilizer bar links
DTSS-if replaced with aftermarket elimination bushings then you effectively eliminate the DTSS which isn't a big deal. I personally like the squirrelliness of the DTSS.
Rear pillow *****
rear subframe mounts
control arm bushings
tie rod ends
ball joints
lateral links


Let's not kid ourselves. The rear suspension on our cars is a very complex system. Any of these things being out of spec will cause handling issues of some type. Easiest ones are rear and front stab. links. and control links.... I can almost bet money that all six are toast. Changing those six alone will dramatically improve body roll.

mr_vaughn

iTrader: (1)

Everyone is forgetting the tires...
Check you air pressures and what size are you running? stock or aftermarket?

RB sway bars will help for sure.
I have with KYB shocks and RB springs.. and love the feel.
I also feel the floating feel after 224K and got the polyurethane bushing kit waiting to go in...
Mazdatrix will have all the mazda comp. rubbers if you want.