Torque steer with smaller wheel size

[sysjl]

I'm running 19x9.5 +38 offset rims with 255/35/19 Michelin Pilot Sport Sports and haven't noticed any torque steer.

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[UFO CTR]

I'm brainstorming to digest the whole idea.

So:
On 18", tire size 245/40 gives you the same speed reading.
And "the closer you get with to the stock offset, the less TQ steering you will have", but then what about those tires such as 255, 265 size? they run with an smaller offsets: does it matter, so you will have more tire contact but with more TQ steering?

we'll prolly need some free body diagrams to understand this stuff

 

[baldheadracing]

I'm brainstorming to digest the whole idea.

So:
On 18", tire size 245/40 gives you the same speed reading.
And "the closer you get with to the stock offset, the less TQ steering you will have", but then what about those tires such as 255, 265 size? they run with an smaller offsets: does it matter, so you will have more tire contact but with more TQ steering?

First, with electronic power steering, conventional "torque steer" - the steering wheel pulling in one direction when accelerating from a low speed - becomes (essentially) a computer programming problem, and thus, solution. The power steering control program is designed assuming an ET60 offset, as no doubt are other handling/braking programs. You can watch YouTube videos demontrating the Type R's total lack of this kind of torque steer. Of course, there is some allowance made, but the algorithm seems able to handle some deviation in offset. I have wheels from ET60 to ET42, and there is essentially no difference in this behaviour.

However, I find it easier to look at "torque steer" as "wheel fight." Whether they are one and the same is semantics. Wheel fight (in the Type R) is when you pull out to pass on a two-lane road and stomp on the gas and the steering wheel pulls you toward the car that you are passing. Wheel fight is when you're driving in a thunderstorm and one side of the car hits a puddle and the car is thrown in that direction. Wheel fight is when you brake (very, ABS full on) hard in a straight line on a varied (from side-to-side) surface, and the car wiggles (yaws) - the wiggling is the braking system electronics reacting to the change in surface coefficient of friction and straightening the car.

I haven't tested every combination of wheel and tire that I have, but my experience is that the amount/nature of wheel fight is a combination of the impact offset has on steering geometry, and the stiffness of the tire/wheel combination. (Stiffness includes tire sidewall stiffness, wheel diameter, and wheel width). Less (ET) offset gives more wheel fight. Tires with stiffer sidewalls are going to give more wheel fight. Larger wheel diameters (keeping overall diameter the same) are going to give more wheel fight. Wider wheels are going to give more wheel fight - but this might be due to wider wheels resulting in stiffer sidewalls (for the same size tire).

Some background reading:
http://www.superstreetonline.com/ho...heel-offset-guide-faq-tips-biggest-lip-wheel/

 

[willimo]

I'm brainstorming to digest the whole idea.

So:
On 18", tire size 245/40 gives you the same speed reading.
And "the closer you get with to the stock offset, the less TQ steering you will have", but then what about those tires such as 255, 265 size? they run with an smaller offsets: does it matter, so you will have more tire contact but with more TQ steering?

Torque steer will almost entirely be dictated by changes in offset - it determines the center of the contact patch in relation to point on the ground made by the line the steering knuckle rotates around (the Dave Point, if I'm remember old Sport Compact Car back issues correctly). The further out this is, the more torque steer you get. This is a bit of an over simplification because if it were this easy, everyone would have fixed it. Anyway, the difference between these points is the scrub angle (I think), so if you increase the width leaving offset the same, you're just increasing the amount of tire on either side of the Dave Point equally, but changing the offset is what changes the amount of tire on either side of the Dave Point by increasing (in the case of wheels for the FK8) the scrub angle.

This is how I understand it, and I am quite likely completely wrong, so....

 

[willimo]

First, with electronic power steering, conventional "torque steer" - the steering wheel pulling in one direction when accelerating from a low speed - becomes (essentially) a computer programming problem, and thus, solution. The power steering control program is designed assuming an ET60 offset, as no doubt are other handling/braking programs. You can watch YouTube videos demontrating the Type R's total lack of this kind of torque steer. Of course, there is some allowance made, but the algorithm seems able to handle some deviation in offset. I have wheels from ET60 to ET42, and there is essentially no difference in this behaviour

Is this right? I always understood torque steer to come from a lot of variables inherent to FWD cars. Where the tie rods end up at the knuckle; the axis around which the steering knuckle rotates; the centerline of the tire; the relationship between those two; the length of the driveshafts to the hubs; caster and toe; and bushing deflection in the control arms. Can they make up for all of that with inputs by the EPS, the same way drive by wire throttle bodies plus a MAF can constantly vary throttle to maintain smooth throttle response and improve economy?

 

[baldheadracing]

Is this right? I always understood torque steer to come from a lot of variables inherent to FWD cars. Where the tie rods end up at the knuckle; the axis around which the steering knuckle rotates; the centerline of the tire; the relationship between those two; the length of the driveshafts to the hubs; caster and toe; and bushing deflection in the control arms. Can they make up for all of that with inputs by the EPS, the same way drive by wire throttle bodies plus a MAF can constantly vary throttle to maintain smooth throttle response and improve economy?

Um, we're talking about the Type R, not every car. There are a lot of variables, but all those variables are fixed when discussing one car. Of course the suspension etc., does most of the work, but there is a program running the steering. Is that program helping to keep the car straight to some extent? My wild guess is yes. After all, a similar algorithm is already there as 'Straight Driving Assist.' ("Straight Driving Assist reduces the steering effort required when driving on a sloped or crowned road. When the Straight Driving Assist system detects that steering effort is being applied to keep the car driving along a slope, the Electric Power Steering system applies motor assist. This reduces the muscle effort required to maintain the desired direction on the sloped road to the same level as is required on a flat road." http://www.hondanews.com/releases/2016-honda-civic-sedan-press-kit-chassis )

 

[willimo]

That's incredible! This totally changes my ideas about changing tings such as offset - if it's aided by computer controls, then I imagine most reasonable wheel offsets we can purchase are well within it's ability to detect and compensate. At least, as far as I'd be able to tell as a mediocre at best driver...

 

[fmoua916]

Here my setup and why I went with this setup compare to stock. Went with Volk te37 size 18x10 +41 offset and tires are federal rsrr 265/35 but they run wider than normal is more like a 275/35 tire size instead since they run one size wider. The inside of my tire and rims pretty much will sit the same as the stock setup sits and for the wider rims it also sits further outwards so I can add more beefier tires for more contact patch and traction. The +41 offset and 10 wide rims makes the whole setup for the car very ideal in my opinion. Performance wise I think it feels much better than stock and I don’t have to worry about bending my rims since my tires have more side wall. Attachment below is a pic of how my new setup sits with tires compare to the stock setup.

 

[baldheadracing]

That's incredible! This totally changes my ideas about changing tings such as offset - if it's aided by computer controls, then I imagine most reasonable wheel offsets we can purchase are well within it's ability to detect and compensate. At least, as far as I'd be able to tell as a mediocre at best driver...

Not really, as, although I could not tell a difference in straight line acceleration from a stop, I could tell a difference in the other situations that I enumerated.

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