Different offsets and the effects on handling

[androo]

Hi guys,

I've read and studied up heaps on different offsets and the effects on handling. The only thing that I haven't really been able to grasp is the effects of having lower offset wheels from front and back on an FWD car (with wheel/tire widths remaining the same).

For example, an EG running:

F: 15x6.5 +35
R: 15x6.5 +25

This is an example only. Barring any clearance/fitment issues, how will this effect the handling of the car? I am aware that having wider wheels at the rear can increase understeer, etc. But would like more firm information about same width set ups with different offsets.

Cheers guys.

[JDM DC2R]

Personally id only worry about offset when wanting a wider wheel and wider tire. And use these webs sites to help
http://www.1010tires.com/tiresizecalculator.asp
http://www.1010tires.com/WheelOffsetCalculator.asp

I own a dc2r. but you should be looking for a wider rim then your suggestion. So you can run some nice wide tires. On my Dc2R i Have 15x7 at 42 offset. Fits Great. Will be running 225/45/15 on them soon!

[eg5civic]

I own a dc2r. but you should be looking for a wider rim then your suggestion. So you can run some nice wide tires. On my Dc2R i Have 15x7 at 42 offset. Fits Great. Will be running 225/45/15 on them soon!

and a 225 is made for bigger than a 7 inch wide rim.
I'd be running 8's at least if not 8.5's. You must have huge sidewall bulge

On topic
More offset increases track, increased track is generally seen as a good thing. Im no suspension expert but

[androo]

Sorry guys, the wheel specs and car was only an example of what I was talking about. I don't actually have an EG (used to!). This actually crossed my mind while choosing wheels for my current car (FN2).

I was thinking of getting the following. The different offsets are due to 18x8 +38/40 are just about flush, while leaving quite a bit of room at the rear. The extra poke is to better fill the rear wheel arches:

18x8 +40 F

18x8 +35 R

Now, usually people run wider wheels to fill the arches better. But we all know for an FF car this just causes more understeer. So what if the only variable is the offset of the wheel?

[eg5civic]

You run the lower offset at the front on a fwd? More track on the front, though not much more, but makes sense on a fwd

[JDM DC2R]

and a 225 is made for bigger than a 7 inch wide rim.
I'd be running 8's at least if not 8.5's. You must have huge sidewall bulge

On topic
More offset increases track, increased track is generally seen as a good thing. Im no suspension expert but

R888 is a round tire so abit of tire bulge is ok. and according to Toyo it will fit 7-8.5 at that offset! http://toyotires.com/tire/pattern/proxes-r888-DOT-competition-tires


Also id be running the same offset from front to rear!

[Rayle]

Lowering offsets will increase the track width of the car. Since the tyre contact patches are further apart, there will be less lateral weight transfer in corners and therefore less body roll. This is a similar effect to lowering the centre of gravity of the car, allowing faster cornering speeds.

However, you won't be able to turn as tightly, so it comes at a compromise.

Here's something I found here (http://www.pro-touring.com/showthread.php?210-Technical-Discussion-Track-Width-(from-old-site)):


I'll use Art's '55 Chevy as an example. It's not b/c I'm trying to advertise, but b/c I know the exact dimensions of this particular vehicle and its performance limit. The car's front tires broke loose at 0.935G on a 200-ft skidpad. The car has 57.5" front track width with sprung-mass CG height of 24.35" (22" overall, including unsprung mass). It weighed 3500 lbs w/ driver with 51.5% over the nose. With all stereo equipment, A/C and all other stuff, it's a pig now. Anyway, at the limit of adhesion, front weight transfer is 683.2 lb, with outside tire carrying 1575.7 lb and inside tire 209.3 lb.

Now let's increase the front track by 3" to 60.5" with everything else being equal. At the same lateral acceleration level, front weight transfer decreases to 649.3 lb (1541.8 lb outside, 243.2 lb inside). Since I know that the tires we used can maintain lateral acceleration until front weight transfer reaches 683.2 lb on this particular vehicle, new lateral acceleration limit can be reverse calculated, assuming the rear tires will be able to hold up. Limit increases to 0.989G. It's a significant increase.

So, in this theoretical example the track width was increased by roughly 5% for a ~5% increase in the lateral acceleration limit. Obviously, the changes will be heavily dependent on the weight of the car, centre of gravity, weight distribution, etc.

I'm not really convinced that an overall 10-20mm increase in track width will really be noticeable though, but you never know...

[rhys.l]

There also the obvious changes in how the suspension is loaded. A little about this here: http://www.hondatuningmagazine.com/tech/htup_0807_honda_wheel_offset_guide_faq_tips_bigges t_lip_wheel/viewall.html

[Rolla_Kid]

I found when I put a 20mm spacer on the front of my car it made quite a difference.
The car had less lift-off oversteer and slightly less turn-in, but gained front grip and reduced body roll. There was also more steering feedback due to the larger scrub radius.

This made it a very stable FWD car in comparison to even offsets where it was a bit twitchier.

[JDM DC2R]

I found when I put a 20mm spacer on the front of my car it made quite a difference.
The car had less lift-off oversteer and slightly less turn-in, but gained front grip and reduced body roll. There was also more steering feedback due to the larger scrub radius.

This made it a very stable FWD car in comparison to even offsets where it was a bit twitchier.

wouldnt run spacers

[Rolla_Kid]

LOL - dont tell me about spacers man, I made them myself, run with longer studs and are both hubcentric to the hub and the wheel. Nothing unsafe about them.

[curtis265]

wouldnt run spacers

That's besides the point.

anway, wider wheels = less weight transfer as the height of CG with respect to the track is now lower

which means less lateral weight transfer and i think better traction overall

but then you lose camber control, and the minimum turning circle



oh and the end with a higher stiffness will break loose first, so if you widen the front track then you'll be more likely to understeer?

Senna wanna post in here yet?