getafewliv

Hey guys,

So the other day I went on a few hour road trip and ended up hitting some gravel on a left corner, going about 120kph (75mph). I slid to the right and quickly countered, swung out on to the highway, went completely sideways, countered back again and somehow made a recovery. I was still doing 90kph (55mph) by the time I got straightened out.

Now, I think the main issue with the gravel, but after this incident, I had noticed that the car wasn't feeling as confident and glued to the road as it was before. And could have definitely been a factor in the near crash as well.

I recently switched from summer tires (rears were bald) to Continental DWS all season tires. I also switched the rears from 255/40/18 to 255/35/18 to even out the look and allow me to lower the rear more for a more balanced look.

I am guessing that by lowering the rears, I have shifted the weight of the car in a bad way and this is why the front wheels feel less confident. When I am travelling straight the car feels fine, no vibrations and it tracks straight But when I start to steer on slight corners above 120kph (75mph), the wheels feel unstable and almost like they are fighting each other. If I hit bumps, the car feels like it is losing a lot of stability. So, I am not sure if maybe the changes to the ride height in the rear also caused a need to get an alignment again.

All 4 of my fender to ground distances are about 25 1/4".

What would you suspension experts suggest to eliminate my issues and fine tune the suspension? I was going to get an alignment, but would prefer to do that last in case that isn't the only issue and costs $100 every time I get it done.

Also, I had my coilvers set pretty soft, and stiffening them up seemed to help a bit with stability on the highway.

My current suspension mods:
- Megan EZ street coilovers
- 2012 ISF steering ECU
- F sport rear sway bar
- Steering damper
- 18" TSW wheels

Keo

iTrader: (9)

Spring Rates on the Megan? Max out the dampening to full stiffness lol. I got my Megan LP set to 32 max clicks. Rides great on swirly roads. also your not low enough. go a finger or no gap at all around full stiffness the lower you are the more control and center gravity. happy camping.

604GSE21

set the front more stiff than the rear would help the rear stick a bit better... and actually lower the rear alittle would help too especially late braking but thats my opinion... are you running stagger tire setup or square? if stagger than maybe u need wider rear tires?... did you change tires all around or just rear?... it could also be your rear camber needs to be adjusted but that you hav to look at your tire wear since you should be using all the tread when you are cornering..

redspencer

iTrader: (1)

I found that by beefing up the rear subframe braces, it really helps to keep the geometry of the rear suspension stable. You'd be surprised at how flimsy the OEM braces are compared to aftermarket braces. Here's one option from Cusco:

scott1256c

A couple of things you can do yourself.
Make sure each coils is still at the correct height. If one of your springs is weakened, it would be tough to tell without a corner balance, but if the rings came loose, you can at least check to see that. Also can't hurt to check preload.

You can do a quick check on the alignment. Checking camber is pretty easy if you have a level and a tape measure. Toe can be check with some string. It would at least tell you if that was the offending cause.

How long have the coilovers been on the car? Could one or more be shot? I assume no oil leaking out of them or you'd have said so.

getafewliv

Thanks for the reply guys.

I should clarify that the issues have arisen since replacing all 4 tires and at the same time, lowering the rear coilovers a bit more.

Previous tires were stock sizes and summer tires:
F: Sumitomo HTR ZIII 225/40/18
R: Pirelli Pzero 255/40/18 (completely bald)

New tires are all season and I went with a thinner tire in the rear for an even look:
F: Continental DWS 225/40/18
R: Continental DWS 255/35/18

The rear coilovers, I dropped maybe 3/4-1" and the fronts were left untouched.

Even with my coilover settings on fairly soft, when I had my car on the highway on corners, it felt very confident and stable before. Where now, the front end feels as if something is wrong and easily goes unstable. The rear feels fine though.

Could having the rear too low cause these issues? I will try and get pics of the height later today. In the front there's about a 1 finger gap, and in the rear, maybe a half finger to no finger gap.

Coil overs are maybe a year old or less and preload should be all good as I had an issue with that before and fixed it. Also, like I said, the handling felt great up until changing the tires and rear height.

Gville350

iTrader: (10)

Having been in a couple of dicey situations myself in the 2IS with the rearend reacting badly to road debris, I've gathered that :

*the ABS system is no help in an emergency situation where you're NOT going in a straight line.
*the VSC is little help.
*your best bet is to not touch the brakes.
*having very stiff suspension in an emergency situation will not help you out any.
*having good tires under you can be a God-send.
*having summer tires in lower than 32 degree temps are just asking for trouble.

In your case, just ensure your suspension is completely in good working order. Make sure you're even around all four corners. Ensure all nuts/bolts are torqued appropriately.

I've read that Continentals seem to have softer sidewalls, which wouldn't help with QUICK steering inputs.

Sounds like you made it out in one piece. Did you have the T/C systems engaged during this ordeal? I always have mine on unless at a track.

getafewliv

Traction control was on and brakes were not touched, it was all steering and instinct from years of fooling around on the road. I definitely would not have made it out of the situation had I not had the experience.

However, regardless of the near crash, the incident just made me realize that the steering is not what it was a month ago before I made the changes. Let's say I am on the highway, a nice flat smooth highway and I am travelling at 120kph (75mph) and it is nice and smooth. The second I start turning the wheels, it feels like the car is losing stability and almost like the front two tires are fighting each other (hence why I am thinking maybe alignment). Where before the car would stay glued to the road like it was on rails. I didn't make any changes to the front end suspension, only lowering the rears. Do you think having the weight shifted by lowering the rear would be enough to cause this? I don't really see how the front end toe could have been changed, but maybe an alignment is all I need. I just want to make sure everything else is correct so I don't need to do more than one alignment.

I don't think this is an issue of just the all season tires not having the performance of the summer tires. When driving something feels off compared to before, and it's causing serious stability issues. I was driving beside a semi truck with a trailer and we were going the same speed on a slight corner and I felt like I was at my limit before instability would occur. Where as before this wasn't even remotely the case.

WylieKylie

iTrader: (2)

Don't rule out the tires. There can be a huge grip difference going from summer to all-season tires. At any rate that will have way more affect than the (likely indescernable) difference in weight distribution caused by the different size of tire.

getafewliv

I honestly don't think it is the tires, or at least not the grippyness of the tires. When I am at higher speeds and taking corners, the second I am not straight, the steering feels less connected and like it isn't tracking properly or that the wheels are fighting each other. I have had much worse tires on before but never had this issue.

And I don't think it's the fact that I went to a 35 series tire from the stock 40 in the rear. Since the newer ones come with the 35 series anyways and I haven't heard of others having this issue.

VTsuckah

iTrader: (1)

By lowering you rear an inch, you changed your suspension geometry. You need to get an alignment.

getafewliv

You think that is the only issue? Or could it be a mix of the weight shift AND an alignment?

When I went from H&R springs to Megan EZ street coil overs, I never got an alignment because I never noticed any issues. Then I had adjusted the height before and once again, didn't notice any difference. This was the first time I have noticed an issue like this. But perhaps because this time I didn't change the whole ride height, I only changed the rear....

If I were to approximate a 50/50 weight distribution, does anyone know roughly how high the rear should be, relative to the front? ie front and rear even when measure from the ground... or perhaps the rear a bit higher/lower?

VTsuckah

iTrader: (1)

The shift in your center of gravity and weight distribution is neglible by lowering your rear an inch. You should always get an alignment when you lower your car a substantial amount from oem, which you have done. That's suspension 101.

There can be a number of reasons why your rear is squirly. Your wheels/tires can also be out of balance. You could have bad bushings, an endlink may have come loose, the list goes on. Take it to a shop and have them diagnose the issue. You should not be driving it if you believe it is unsafe.

VTsuckah

iTrader: (1)

Here is a great read about suspension dynamics and tuning.

http://www.rapid-racer.com/suspension-tuning.php

minato

iTrader: (1)

the closer you are to the ground the more stable your car should be around corners .
look into getting a 4 wheel alignment done , but most likely , I think its your tyres.
you should also check your rears for any play in the wheels , theres alot of things that can cause what you are experiencing, you should also take it to a shop to check it out..