benifits of a zero offset wheel...

[Vanilla Sky]

i know it would take some bodywork to get a zero offset wheel to fit under our cars, but would it be a plus for perfromance in any way? i figure a wider track would help when cornering hard... i don't mind chopping up a car to do it if it's worth it... i'm thinking about running a 3gee in the grassroots motorsports $2005 challenge, and i need as much cheap stability i can get, and this might be a way to get it... would like a really wide, say 45mm offest be better? i'm only paying $125 for the car, so i do have some money to spend IF i decide to actually run...

and yes, i know that i'll be up against better cars, but the way they scoring system is this year, a great 1/4 mile time won't offest a bad autocross time too much... in the future, i'll be making more threads about the challeng if i decide to go with it...

for now, i might decide to go with the zero offset wheels on my car "just because"...

[buds302]

dont you have to worry about the upper ball joint if you go wider? i looked at mine and it looks pretty close.

[Vanilla Sky]

no, the upper balljoint isn't a problem... anyways, with a zero offset, the wheel sits more towards the outside, so the wheel can be wider still... the big problem is bodywork... if i'm doing this with a race car, then i can just cut the arches out and make them bigger... even with a street car, it could be done, simply by extending the bodywork out...

i'm looking for any advantage a zero offset would have, barring any fitment issues

[AZmike]

A zero offset wheel will buy you about 90 mm additional track on our accords which will improve the car's maximum corning ability somewhat. You'll also increase the scrub radius so you'll have much more steering feedback (probably including a lot more torque steer as well) and increased steering effort. You'll also be changing how your wheel bearings are loaded, which is likely to shorten their life.

[Neuspeed87lx]

wouldnt a zero offset wheel throw the sai angle off ? inturn wear tires quickly ?

[Justin86]

might be better to just try a more normall offset with wider tires. You will still have to chop the fenders depending on how low you go to stop rubing, but it wouldn't be as hard on the bearings.

[AZmike]

SAI (steering axis inclination) is a function of suspension alignment, not wheel measurements. It's determined by the position of the upper and lower ball joint in A-arm suspension. More of the contact patch will drag when the steering is moved with the car stationary with the reduced offset, but once the weels are rolling I doubt they'd be much of a difference considering the other abuse a race tire is going to see. What is (are?) the course(s) like? The more tight slaloms the less the increased track would help.

[smufguy]

zero offset to run what size tires? i would say 225 or 235s should give you enough traction. I have seen 255s on some DSMs and they haul ass around the track. But Derick, get a LSD before u get too much money spent on suspension. LIke mike said, WE have one awful torque steer, even the previous TL experienced massive torque steer.

[AccordEpicenter]

yea it might help somewhat in a track setting, but for daily driving itd be a nightmare and a handful, being darty and full of torque steer... im curious to see how itd react turning corners though...

[1987HondaAccord]

ok... what is torque steer exactly?

[AZmike]

Here's the first decent article I found on google:
http://www.sportcompactcarweb.com/editors/technobabble/9909scc_technobabble/

There's probably something a little better if you're willing to spend some time looking.

[smufguy]

Source: http://www.mcasco.com/qa_ts.html

Question:

Is there a mathematical explanation for the phenomenon called "torque steer" affecting front wheel drive vehicles having unequal length half shafts? Although this was first recognized at least 20 or so years ago, the SAE has no mention of it in the 1999 edition of SAE Standard J67e Vehicle Dynamics Terminology. My research has only been able to unearth several very superficial explanations of this well documented phenomenon, some of which are obviously absurd. Any help you can lend in steering ( ? ) me in the right direction is greatly appreciated.


Answer:

Yours is the second question on torque steer so I thought I would look into it. In researching the term on the web via AltaVista I even found contradictory definitions of the problem.

My first instinct was to go eliminate the angular displacement inherent in long shafts under torque. The twist of the shaft, if you will. In any reasonable length, reasonably stiff shaft this transient effect would almost certainly go un-noticed by a driver. Also on the web at http://idt.net/~gdonovan/trans.html I found the following:

transmission In 1984 Chrysler came out with its first turbo 4 cylinder; and it was good. There was one small problem though, the car under boost would tend to torque steer. This is a tendency of a car to "pull" in one direction while under power. Its caused in part by one axle being longer then the other and when the engine is under power the longer axle becomes a lever which pulls the car in that direction. Ma Mopars fix was to make the drive axles the same length by adding a intermediate shaft the was perfectly straight (in effect becoming part of the transmission) till the axle on the right side was the same length as the left. Axles are even interchangeable left to right. Most cars that do not have this system can be retro fitted to it as most 2.2-2.5 engines have the bosses cast into the block.

The notion of one the half shafts becoming a lever an physically pulling the car in one direction strikes me as iffy. I include a picture from the above referenced web site an attachment to this email. In that you can see that the introduction of an intermediate shaft would aggravate the twist issue, further substantiating my idea that time delay between engine and wheel is not the culprit.

I get the impression that torque steer is a catch-all term for anything that might transmit force back to the driver through the steering mechanism during acceleration. Suppose for example that the steering axis, that axis about which the wheel is turned in steering, did not pass through the center of the contact patch between the tire and the road. Then there would be a moment arm in the horizontal plane through which the reaction force of the of the road against the tire would act to tend to steer the vehicle during acceleration. This seems to me to be a likely candidate for the torque steer phenomena.

What is not clear to me is how the steering axis depends on the length of the half shafts. Possibly the steering axis shifts a bit during acceleration and that shift is mitigated by the added stiffness of a short shaft. Perhaps these ramblings will trigger something in your mind. If you have any question about what I have said, or would like to enlighten me further please respond.


http://www.mcasco.com/images/trans_7.jpg

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Source: http://www.ime.org.uk/ime/t/torque_steer.html

Article: Torque Steer, theories for causes of

(1) It's because the longer one is less stiff torsionally. Torque applied at the engine end is resisted by the torque at the wheel end, but sudden application of more engine torque winds the shaft up slightly (like a rubber band), driving the car sideways.

Or...

(2) Basically, it is to do with the different angles that the driveshafts make with the horizontal. When they accelerate, they gain rotational momentum, and if they are at different angles, then there is a net force... it is very strange.

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source: http://www.vwot.org/list-archives/msg11268.html

Article : Torque steer

The distance between the point where the steering axis contacts the ground
and the centre of your contact patch, normally referred to as the scrub
radius is to blame. This distance is very difficult to minimize on Mac
strut cars, so then it becomes a matter of minimizing the effects of torque
steer, caused by the tractive forces acting across the scrub radius, causing
a turning moment on each of the front wheels, one clockwise, the other
counterclockwise. As the real world conditions are rarely equal from on
side to the other (hence canceling each other out), the wheels will tend to
turn one way or the other. Equal length driveshafts can minimize torque
steer, as can suspension geometry, damping characteristics etc can minimize
torque steer effects. Wheel offset is critical, hence playing with ET
values on driven front wheels is not just a matter of bearing loads, but a
matter of driveability and ultimately safety.

Hence and therefore....equal length driveshafts or not, you have to start at
the root of the problem to minimize the scrub radius. Once that is done,
fine tune with the other factors. For many of us, the easiest place to
start is looking at the ET values on our aftermarket wheels.