Anyone have a setup of 15mm spacers in front and 20 rear?

antennahead

I am sure many of you have seen this site, it is also quoted by a lot of other performance sites:

http://krausracing.com/pages/info/Ov...er%20Steer.pdf

This is what I get confused on, and hopefully some of you with a lot more knowledge and track experience can help. Under "Oversteer Corrections" (reduce oversteer), it lists "Install wider rear tires" and "Install wider rear wheels" as solutions to reduce oversteer. It also lists "Reduce rear track" ........ If widening the rear tires and/or the rear wheels will reduce oversteer, why would "reducing the rear track" do the same? I would think "widening the rear track" would reduce oversteer. Doesn't a wider wheel or wider rear tires also widen the track?

John

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RCZ

Umm widening the rear track refers to pushing the wheels further away from each other. When you do that, and its hard to explain, it increases understeer because the rear track now has comparatively more resistance to weight shifting and to losing traction than the narrower front. Think of it in a more extreme case where you increased the rear track by a foot. It becomes harder to rotate the rear compared to the narrower front and that causes grip to be lost in the front first...understeer. I hope people with the technical term for this phenomenon will chime in with some real physics to explain it. I know it does and how it feels, but I could use a lesson here too. **paging ChrisSlicks**

Widening the rear tires will reduce oversteer simply because of the physical grip generated by a larger contact patch.

Widening the rear track does not equal widening the rear tires at all. Do the tires on cars with wider wheels than our stock wheels stick out the side of the fenders? Nope, they usually end flush with the fender...

Widening the rear track DOES reduce oversteer AND thereby increases understeer. (Don't yell at me track guys, I know that isn't completely true, but for the sake of keeping things simple...)

Just think about it this way... understeer is when the front tires grip less than the rears. Oversteer is when the rear tires grip less than the fronts.

For example, racecars tend to run more negative camber in the front because that increases corner grip up front and thereby reduces understeer. In theory, they could also run a narrower rear track to induce oversteer, but you wouldnt want to do that because you would be sacrificing available grip.

antennahead

"Widening the rear track DOES reduce oversteer AND thereby increases understeer. (Don't yell at me track guys, I know that isn't completely true, but for the sake of keeping things simple...)"

This is exactly what I thought, which led me to believe the article I hotlinked was wrong when it said reducing the rear track would reduce oversteer.

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RCZ

Well, I would say those guys definitely know way more than I do, so I may very well be wrong. I was driving around with only a front spacer installed for a couple days when I did my install and the car was definitely more tail happy. Like TC flickering all over the place. Now that I have everything rounded off, I only see it flicker when I do something silly on purpose.

Then again..I and all the other folks here who said wider rear track = more understeer could be wrong. They list widening front track to lower understeer... then narrowing rear for reducing oversteer sounds a little odd.

I don't mind being corrected if it isnt the case though....anyone?

JB1

OK, I tried to get the final answer, but I failed... One thing I remember is that when the Ferrari F50 was introduced, the magazines wrote that the rear track width was narrower then the front to reduce over steer! But when I looked up "trackwidth" and "over steer" now, I found this: Automotive suspension engineering - Front/rear track width effects These guys seem to know what they are talking about but still no clear conclusion. One thing I can personally confirm is: Go-karts are "tail happy" (tend to over steer) and their rear track is wider then the front track width. So that might be why I lean more to "wider rear track width = over steer"

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JB1

Oh, one more thing I thought off: the Citroen DS, SM, CX: front wheel drive cars with rear track widths way narrower then the front track width. These cars did SERIOUSLY under steer. (I drove the CX myself and can confirm from experience)

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antennahead

"They list widening front track to lower understeer... then narrowing rear for reducing oversteer sounds a little odd."

This is exactly what baffles me, "if" widening the front track reduces understeer, which most seem to agree with, then it would seem that narrowing the rear track would have the same effect, reduce understeer/increase oversteer, NOT as it states (reduce oversteer = reduce rear track)

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RCZ

I've been doing research and it seem that its a pretty hotly debated subject we've stumbled into here. It appears that some of todays supercars are using a wider front track.

Lets put it this way though, making the front wider is the same as making the rear narrower. If making the front wider reduces understeer, then by definition decreasing rear track will also reduce understeer. If you are reducing understeer, you are increasing oversteer.

Basically, A narrower rear track will increase oversteer.

Someone posted the reasoning was that a wider front track will increase the amount of rolling load that the front track manages. More load going into the front tires means more grip up front, less in the rear.

ZForce

Still waiting for the install to happen, building up a little toy box of mods and none have been installed. Half of the mods are sitting at Z Car Garage and the rest in my garage. Just getting some pre knowledge so when I buy the sways I will have made the right purchase for my already mods list.

The camber settings are exactly what I was looking for, in addition to the benefit of sways with wheel spacers. I am leaning towards the Stillen sways based on our previous discussion on another thread that Hotchkis would be better suited for coilovers and Stillen would be better suited with Eibachs.

Thanks again for your advise!




You got that right, I did not know that my confused mis-quote of a couple of members would get a hot debate going. No offense to anyone, like I said from the start that I am naïve to this stuff. Like you said it’s all about finding the right balance. I will sit back and learn from the more knowledgeable members and not stir the pot of confusion with my inexperience in this area. Thanks for the advise!

This thread is getting very interesting and I was hoping someone (John) would provide a link to a resource to educate me in this area. You guys have been great and very patient with me. That is why I joined this forum!

Cheers
Curtis

BlackCherryZ

thinking about 15 front and 20 rear spacers, eibach springs and sway bar, and 255/35 front and 295/30 rear on 19 inch OEM Rays

do you think i need a camber kit as well........?

is it required to have an alignment?

also, i need to have a camber kit to have the alignment, right?

Mike

You definitely need an alignment. I was able to get alignment to factory specs with all of the above except stock tires.

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marcussoori

What if we want to maintain factory ride height and OEM 19" wheels (speed bumps where I live are crazy), but add the 15/20 spacers? Is it possible to get alignment to factory specs without a camber kit? Someone above mentioned negative camber after installing spacers being desirable, is this necessary to maintain the factory handling and longevity qualities?

I asked earlier about how this would affect wheel bearings. 15/20 would not affect wheel bearings at all?

Finally, someone mentioned having a larger spacer in the rear might increase understeer. In that case should I go 15/15?

Sorry, just very confused about all of this.

Thanks...

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RCZ

Yes, you dont need to lower the car to install spacers.

If you don't lower it, then absolutely. If you do lower it, then probably not. The more you lower it the more you have to get a camber kit.

I think you are confusing installing spacers with installing springs. You will gain a bit of negative camber when you lower the car. Negative camber is better for cornering grip, but excessive amounts of it will wear out your tires quickly.

The ratio between front and rear camber plays a big part in dictating the behavior of your car. More negative camber up front means more grip to the front tires on corners; that means that the front tires will have proportionally more grip than the rears. If you are in a corner and your front tires have more grip, then your rear tires will slide first. That is called oversteer.

If your front to rear camber ratio is the other way around; meaning that there is more negative camber in the rear, then that will cause the front to start sliding out first. When the front tires lose grip first, that's called understeer. You are trying to turn, but the front tires dont grip, that causes you to "push" or "plow". So instead of turning where you want it to and making the arc you want for the turn, it is opening up that arc and pushing the arc wider than what is optimal.

To explain camber, I always just tell people to picture it in their minds. Your traction is linked to the physical connection between the tire and the ground. The bigger the contact patch, the more grip you have. That means that if the tire is flat on the ground, aka perfectly vertical, then the contact patch is as big as possible. Vertical would look like this "||".

What happens though, is that because the car is on a suspension that needs to be soft enough to absorb bumps, when we go into a corner the tire doesnt stay straight on the ground. The suspension flexes because of the sideways load of the g-forces acting on the mass of the car. That means that the tire is no longer flat on the ground in a corner. If you start from this "||" and you take a corner, your tires will end up like this "//". In other words, due to the flex of the suspension, etc. your previously flat-on-the-ground tires are no longer flat, but one edge has lifted off. That causes your contact patch to shrink dramatically and as we know already, smaller contact patch means less grip.

So how do you get the contact patch to still be as large as possible in the middle of a corner? In other words, we want the tire to be completely vertical in the middle of the corner to maximize grip. The answer is to start from "\\" position, so that when the suspension bends and the g-forces act on the car, it will pull it from "\\" to a "||" position. You are starting from a slight angle that opposes loads of a turn; it would look like this "// \\". That guarantees that no matter which way you turn, one of your front wheels will be flat. On a left hand turn where the car leans to the right, it would look like this "// ||" that means that the right side front tire has the biggest contact patch. That tire also has the biggest amount of grip because the weight of the car shifts to that end of the car. If you remember from physics class, pressure is one of the factors that affects grip. The more pressure, the more grip you have. If you were making a right turn then the weight would shift the other way like this: "|| \\" and the same thing would occur except with the front left tire.

When you have 0 degrees of camber, that means that your tire is like this "||". When you have negative camber, the tops of your tires are closer together like this "// \\" and positive camber is the opposite "\\ //".

I am never writing all that again, wow did I get myself into that mess and then it was too late to quit. If that doesn't get one rep I'm signing off these forums forever.

I'm not sure about the bearings, but it wouldnt be too far fetched that the greater leverage caused by the wheel being further away has unwanted effects. However I think its negligible at most.

Dont go 15/15 cause of that, just get what you like. I really don't think its going to make any difference in your life. Plus if you do get understeer....you can always go a little more negative with the camber up front and that will help you correct it.

BlackCherryZ

i think minicobra had similar setup with spacer, eibach spring, and sway bar, but he did not state about the alignment.......nor camber kit...........

i think i also read that with spacer in this particular set-up, there would be less of the effective negative camber........thus, alignment is not required.........

is my understanding accurate? please enlighten me *^^*

so, camber kit is a must........with spacer, sway bar, and eibach spring with wider tires on OEM rays...

also, in terms of balancing, what is the optimal camber spec? is OEM spec the optimal?

i would think this would be more of personal preference, but for a daily driver what is the optimal camber spec......

does anyone have similar set-up as what i have listed including 255/35 and 295/30 tires in OEM Rays?

i would appreciate feedbacks based on experience......

m4a1mustang

OEM spec is optimal for daily driving.

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