Rear track-width changes

[ozmdd]

Another autoX question that can probably be addressed by track and drift guys/gals too.
What do rear-track-width changes do for our handling/cornering? Is there any good reason to widen the track with hub spacers if the goal is getting better turn-in and control? Don't care about cosmetics.

I have the option to run 5mm more offset on each rear wheel, switch it to 5mm more in the front, run the same offset on all 4, or get PG hub spacers and combine that with either offset option.

In my mind, it seems that a narrower rear track helps turn-in, but I'm not even pretending to be experienced on this. My knowledge is strictly theoretical engineering-school stuff.

I've seen some autox FWD cars with crazy-wide rears, so that leads me to believe that there are different schools-of-thought on this.

[YAR1S]

This may sound silly and maybe I am imagining things but I installed the PG13's on my stock suspension and my yaris takes ramps and corners much more smoothly now im guessing to the extra inch in rear tire distance. Like I said, I may be imagining it, but to me they were worth the hassle (in my case) of putting them on.

[YarisSedan]

Yeah wider track helps handling

[kngrsll]

i found it helped my stability a bit on a tight road course. i have a write up somewhere...

here is my review: http://www.yarisworld.com/forums/showthread.php?t=21197

[Blown_xa]

widening just the rear track width will cause your car to understeer more than is does already. You should keep it the same width front and rear if not wider in the front. Increasing track width over-all will make the car more stable, but also you are extending the leverage point of the suspension therefore softening your spring rate in a sense. If you understand suspension and handling characteristics and how to adjust them, then you can come up with a killer handling car.

I use 20mm spacers in the front and 10mm in the rear.
I set up my car for slight oversteer steady state.
Also in my set up to acheive that includes:
Progress Coil-overs with 200 pound springs in the rear, 450 in the front.
Progress rear sway, stock front sway (soon to be omitted)
-2.6 degree front camber, 0 toe
-1.1 degree rear camber, .40 degree toe in(per)-rear toe in helps with stability on high speed road coarses with short wheelbase, probably run less for auto cross.
Tires are everything, you can have $6000 coil-overs and a guy with stock suspension but with better tires will beat you...
I run Toyo R1R's 225 50 15's all around
28psi cold front
33psi cold rear

just suggestions but at least you have something to go by.

[Tamago]

Originally Posted by Blown_xa

widening just the rear track width will cause your car to understeer more than is does already. You should keep it the same width front and rear if not wider in the front. Increasing track width over-all will make the car more stable, but also you are extending the leverage point of the suspension therefore softening your spring rate in a sense. If you understand suspension and handling characteristics and how to adjust them, then you can come up with a killer handling car.

I use 20mm spacers in the front and 10mm in the rear.
I set up my car for slight oversteer steady state.
Also in my set up to acheive that includes:
Progress Coil-overs with 200 pound springs in the rear, 450 in the front.
Progress rear sway, stock front sway (soon to be omitted)
-2.6 degree front camber, 0 toe
-1.1 degree rear camber, .40 degree toe in(per)-rear toe in helps with stability on high speed road coarses with short wheelbase, probably run less for auto cross.
Tires are everything, you can have $6000 coil-overs and a guy with stock suspension but with better tires will beat you...
I run Toyo R1R's 225 50 15's all around
28psi cold front
33psi cold rear

just suggestions but at least you have something to go by.

lol guys, haven't we already learned that a stiffer rear spring one of the easiest modifications to combat understeer?

your toe-in settings (which i'm guessing are FACTORY, you haven't done anything at all to the rear of the car) are excessive and will be detrimental to your turn-in.

[Blown_xa]

they are close to factory but I did adjust them. I use feeler gauges in between the hub and axle. These cars are a very short wheelbase, that changes what you may think. On our tC we run toe out in the rear on small tracks but it also has a huge Kognition rear spoiler to keep it stable. My car is set up well, I posted a couple of videos you can check out and kinda get a feel foer the balance of handling. Like I said, it has slight oversteer. And If I throw it into a turn the rear end kicks out contrary to what you say.
Here is a video from more than a year ago, same alignment spec but with 200 pound springs in the front. RTA practice, camera from a Porche GT3. I ran off line and turned in to fast to correct and that's all it took. btw this was 130whp stock motor
http://www.youtube.com/watch?v=_toT_...layer_embedded

[Blown_xa]

here are some auto x results with my street tires from this year: (in case you doubt my credibility)

http://www.get-fast.net/nasacross/022209res_raw.htm

http://www.get-fast.net/nasacross/052409res_raw.htm

http://www.get-fast.net/nasacross/062809res_raw.htm

http://www.get-fast.net/nasacross/072609res_raw.htm

http://www.get-fast.net/nasacross/092709res_raw.htm

http://www.get-fast.net/nasacross/011809res_raw.htm <--all seasons (wintercross)

I have 2 auto-x's this weekend. If I get top 3 in my class I win the championship points for 2009 in my class, and 3rd overall.