JIM THEO

May be stupid question but wonder what should happen if I increase slightly front track of my car in order to reduce understeer?
Basically I am thinking of different offset (but same type) wheels front, say SuperL” 18x8”/ET46 front with 18x8”/ET51 rear, a small – 10mm – total difference, but if my memory serves me right the STI type C has also wider front track and is a very good way of increasing front end stability when cornering, have a look at Peugeot 306 Maxi!
What is your opinion about, have you ever tried something similar?
JIM

BART!

What have you done sofar to reduce understeer ???
Wider track could help but it could increase wheelbearing load too much and what does it with 'straight ahead' stability (under hard braking)...??

First go the 'a bit more negative camber'-way and some added caster by fitting ALK...

JIM THEO

Well, I already have 1 degree negative camber (that also affects stability usualy on brakes and promotes traimling), thicker rear anti roll bar and 1 mm per wheel toe out rear that helps a lot, just want other opinions about the wider track!
I am not going to increase it before the new Prodrive springs arrive just ask for others experiences.
STI front/rear track: 1490-1480
WRX front/rear track: 1485-1480!!! why when the STI wheels along with the huge Brembos front are much heavier? And yes I know that STI driveshafts and bearings are stronger.
JIM

[Edited by JIM THEO - 12/6/2003 1:16:17 PM]

mutant_matt

I don't believe that the MY01 > STi has stronger bearings. IIRC, they are the same as any other model which is a shame as the car is heavier. Some of the boys in Oz have found the bearings start to flex and need changing inside 20,000kms, especially if the car is used on track, the first sign being significant pad knock off.

Just thought it worth a mention

Matt

prana

1 degree negative is tiny, whatabout go 2.5 degrees ?
Stiffen your rear shocks and anti-roll bars to compensate.

StickyMicky

try sum wheel spacers on the front, they cost pennies and will give u a wider track, and will save you money if it doesnt do what you hope it will

JIM THEO

Actually my question is if increased front track helps to reduce understeer!
JIM

Denmark

iTrader: (2)

It is surposed to make it better,but i have not tried it,

I was planing on trying som 3mm spacers to see if it make any difference


Skassa

JIM THEO

Keep me informed mate...
JIM

ex-webby

Hi Guys

JIM THEO. Excellent thought. I would be interested as to what made you think of that, as it could be a great topic for discussion all on its own.

Theoretically a wider front track will indeed reduce understeer. The reason is that there will be less load transfer across that axle.

Unfortunately, in practice, all geometry / suspension tweaks have effects (probably unwanted!!) on all other areas of the suspension. So unless you plan to set-up the rest of the car, you can never be sure that you've done what you planned, until you've conducted thorough testing.

To give you an idea of the simplest form of this I can think of is as follows...

During cornering the wider track will mean that the bars and outside springs will not be worked as hard (it will be easier for them to resist the load transfer, as there will be less of it). This means that the spring and roll rates will be (assuming they were right before) too stiff for the new set-up. This *could* cancel out the positive effects of the wider track, or even make things worse.

Of course, it isn't anywhere near as simple as that, and the above example can be destroyed by steady state physics examples, but I hope it illustrates the point.

All the best

Simon

JIM THEO

Skassa 3mm spacers actually may not help or make things worse as they trasfer wheel weight outside while increased offset - I imagine - keeps the weight balance of the rim somehow, all theoritically as Simon states.
On the other hand the spacer itself may cancel the phenomenon Simon describes above where car resists more to load transfer as now suspension "sees" more weight due to increased distance between arm and center of wheel (believe me my English don't help me here). I mean even if the wheel weight remains the same for the suspension it's heavier!
JIM

JIM THEO

Simon to answer in your first question I try to remove understeer from my car and my conclusion is that it's far better if you could cancel udersteer and inrease front end stability rather induce oversteer to help you!
I am not expert but my understanding is that if you change more parameters, say add some camber/toe, little harder ARB, little stiffer springs and other tricks it's better as each one affects with different way when cornering while you keep the overall balance.
I don't like extreme solutions, toe/camber helps when you first enter in to the corner, ARBs/suspension during and differential usualy in the exit so it's better to have a "equilibrium" between them when changing one.
I'd like to see Damian's answer on this!
JIM

Creepy

I recently fitted an AST suspension to my car (MY00 turbo), It is of course much stiffer then before, almost no roll, firmer and "crispier" to drive.
I set the cambers front on 2°, rear on 1° and understeer is almost gone, just when you floor the throttle or really do stupid with the steering it goes, but on normal driving (also on higher speeds), understeer is very much reduced (this counts also for wet roads).

Creepy

AJbaseBloke

Interestingly, while the new Legacy has a wider track front and rear, it got wider front than at the back (will have a dig for the numbers vs the old model). Jim, I defo think it can help (IMHO), along with some more caster up front to provide some more bite (and dynamic camber - is that the right/wrong term?).

Been wanting to try that tread variance trick on my car since going to ET48mm all round some time ago - been nagging me that staying with 53/55 at the rear may have been the way to go.

Good luck with your "project" aqnd very much look forward to hearing of your results

vindaloo

Hopefully this is right.... If not, no flames please

According to theory of moment arms etc. moving the wheels out creates a longer lever. Assuming the mounting points for the suspension and attachments for springs/struts remain the same, then the spring and damping rates for that axle are effectively reduced. The same vertical deflection of the wheel/tyre results in less movement at the spring/shock. In cornering, I would expect marginally more roll, slower loading up of the wheels and less ARB load transfer. Effectively this would slacken the front compared to the rear. I'd expect it to result in less understeer, more oversteer.

Rather than using spacers, wheels of less extreme offset could be used on the front to give the same effect but without necessarily increasing weight. (i.e et50 or 53 on the back, et45 or 48 on the front).


Vindaloo.

AJbaseBloke

Well, there are some gymkhana competitors running the new shape's front arms on the older, narrow track cars (drive shafts too I guess).

One very fast Legacy at a recent event had them on too - it certianly was impressive on the course and the owner swore by them.

edit to make the English somewhat understandable

[Edited by AJbaseBloke - 12/18/2003 9:57:49 AM]

JIM THEO

Ok, someone with good English and technical background let's bring back the old topic and ask Damian Hurty the above please!
JIM

911

I hill climb my STi V3, and in standard and with ALK fitted spec the car understeered to a point I would go round track bends on full lock...
Checked the MRT/Whiteline sites in Oz. I now have 2.5 neg front and 2 neg rear BUT with 4.5 deg positive caster using the MRT top mounts. Understeer, NO! Just lots of static and dynamic camber.
Just a thought.
Watch-out for those spacers as the wheel studs are not very long as they are, spacers will leave you with not enough threads...'3 wheels on my wagon' song comes to mind. Take care.
Graham.