Everything I've read tells me that I want to put a 22mm sway bar on my car if I'm doing track events. However, it appears that going with the H Sport springs removes some of the understeer problem. Do I still want to add a 22mm sway bar if I plan on installing the H Sport springs?

 

yes you do. the H-sports are progressive rate which softens initial bump and makes the car roll a bit more during turn-in...also the lower roll center
will augment the roll of the car.

you need to get the thicker swaybar to tighten everything down. :smile:
otherwise, just leave it stock.

 

Yes.

 

Are you sure on that? I don't quite agree. If lowering the roll center, you decrease the mechanical advantage of rolling mass and decrease the amount of roll. I thought??

 

they work great together...

 

they do work good together...

....but is that point given by Kenchan correct?......anybody?

 

don't doubt me guys... i know this stuff.

You guys should seriously play around with RC cars and setup its
suspension for racing. it will give you so much experience on
tire pressure, tire selection for different temps, damping, spring
rates, linear vs progressive rate, roll center adjustments,
ride height, corner balancing, alignment, etc. etc. at fraction
of the cost and driving at the limit of adhesion without killing
yourselves.

then you'll know why suspension mods are so much more important
than doing power up mods at first. driving skills, foot work of car,
then naturally speed will come. then you add power.

 

So what's the reason?

 

Kenchan is 110% correct! Look up Roll-couple. I've written about it several times.

I'm outta time today, so here's a quicky;

The center of gravity creates a torques about the roll center. When lowering a MacPhearson strut, 1" for example, the roll center will drop more than one inch increasing ROLL COUPLE. Think of this relationship as a pendulum. The distance is increased and the leverage is greater. More later.

 

as Meb said (he's a doctor, you can trust him).

Think of holding a piece of pie vertically with the point facing down.
imaging your car is pivoting at the tip of the pie which we shall
consider the roll center. Now let's imagine that there is an imaginary
arch in the center of the pie parallel to your crust. the imaginary
arch is how much roll your car has at factory height. Now, if you
lower your car, your tip of the pie (your roll center) will also lower
the same distance. your arch area is now closer to the outer
crust. notice how much more arch your car will travel now.

You have to compensate that larger arch with swaybars especially
when running progressive rate springs as the initial bump is soft and
will augment the initial roll.

this is another reason why most competitive drivers/racers
hate progressive rate springs. it's a lot harder to tune progressive
rate springs especially when running only rebound adjustable dampers.
this is why i don't like the koni's as I can't control the bound to
compensate the intitial bump and roll.

im no doc, this is the best I can do.

 

was'nt doubtin' U... just need to make sure cuz on here everybody has an opinion & like an a55hole they all stink! so hard facts for me is the only way.. i totally get ya' im into RC'c meself

 

one thing though- the roll center may not initially be at or below the center of the wheel. Only when the roll center falls below that point will you pick up higher oscillation. I believe the center of gravity is higher than the wheel center stock. In this case, a drop that does not go below and only approaches this roll point will reduce roll, not increase it. I believe.

 

Focus on the length of the lever arm. Kenchan's pie slice is a great way to imagine how this works.

If the pie crust - sorry to repeat Kenchan - in fact depicts the plane upon which the center of gravity moves/rotates, the point is the roll center. When lowering a Macphearson strut say 1" - just an example - the center of gravity is lowered by one inch, but the roll center is lowered more. This creates a longer lever arm between the center of gravity and the roll center. Using Kenchan's analogy, the distance between the crust and the point is now farther apart. A longer lever arm allows the center of gravity to act upon the roll center with greater force.

Adding negative camber will help to raise the roll center so that the lever arm is shortened. Stiffer springs, dampers and swaybars help to alleviate weight transfer, but the force is greater nonetheless.

This relationship is called roll couple - search the web, read some suspension books...it's good stuff. Roll couple, like all lever arms, are very proportional when it comes to moving weight around.

Tuning is an ongoing backward and forward relationship. Race teams have a different set-up for each track and for different weather conditions. They, like us, have to take many of these things, like roll couple, into consideration every time they change something. You will invariably affect other parts of your car's suspension while tuning it. But, knowing what is affected and why, is where you begin to employ choice. You can either choose to ignore these affects or try to correct these. Otherwise, without knowledge of these affects, you are tuning blindly.

 

Hey, I'm a doctor, too, but I still know doodly about suspension setup.:smile:

First, from experience, I think the swaybar is a good compliment for the springs.

Second, the more I do to my suspension, the more I realize how complicated this all is. For example, I changed from 205 r-comp tires to 225's and had immediate problems. The car was less controllable because the increased grip totally overcame my toasted stock dampeners. Now I have Koni yellows and am having a b1tch of a time trying to get swaybar/shock settings right. Currently I have too much oversteer and I spend 75% of my attention on the autocross course trying to drive the car and 25% driving the course.

Back to the drawing board.:impatient

 

is it posible to feel this w/215 40 17's ?? ( anyone ) cuz i swear that my ride now feels a bit like its draggin' around due to the wider then stock foot print ( but very crisp in handlin' )so was thinkin' on going into a 205 40 wheel but my wheels are in that 7.5 width......??...which will result in a bit more stretch of my tyres these tyres im using are designed for that so dont see a problem w/it..

 

god dang, these doctors over rank me.

 

I know we're getting off topic a bit...

You may find that a narrower tire 'works' better than a wider one under some circumstances for a given rim size. If the tire is too wide for the wheel, despite a more agressive footprint and a lower profile, the side wall will actually flex more. There is more stability - predictability - to be had by stretching the sidewalls out a little. An easy target, BMW's M3. Notice how the thesidewalls are stretched.

I tire that is too wide, for the above reasons, may be very difficult to control. You may be able to produce a higher G load within the context of this example for a nano second, but you may give up controllability/predictability.

 

I don't like using wide tires on the MCS either cause it looses the nimble ness.
but imho low profile tires on this car makes it too nimble for street.

I chose the 50-profile and the softer GS-D3 sidewalls for this reason.
there's a lot of things involved on why i chose this current setup.

 

Actually, you can attain a better feel for what is happening witha taller profile.

 

Really? cause my 35 profile tells me that I crunched an ant where as the 50 profile won't...

 

My problem with the wider tires was too much grip for the other componants to handle. On rapid, hard turns (we're talking aurocross here) I was actually pogo'ing off the bump stops. Now, with my current settings (stock front bar, Hsport rear at middle setting, full soft front koni's and 1/2 soft rears, -2.0 degrees with 1/8 out toe front, -1.5 and no toe rear,Kosei K-1 15's with 225/50 Victoracers), the front grip is awesome but the rear is flying back and forth in the breeze.

 

Poor Gobble

Can't get a straight answer

 

I think I decided to skip the springs for now and think about it over the winter.

 

see my first post, first line. "YES YOU DO!"

 

Feel in my above response refers to loss of grip. Pneumatic trail is defined more, no, mostly if not entirely by tires (mechanical trail and caster have 'something' to do with how pneumatic trail is generated) . Low profile tires do not necessarily send those tingly little messages as quickly as taller tires; as a tire builds cornering forces, the steering should (if the steering isn't overly damped or aided) get heavier. However, as one approaches the limits of adhesion, the steering should begin to lighten up, telling you, the driver, that you are indeed not far from loss of grip. This all happens sooner and typically with more room for error with taller profile tires.

That said, and all else equal, lower profile tires will help one to generate more cornering force...and feel ants as you drive over them. But the information telegraphed to the steering wheel with regard to loss of traction occurs later - at higer g-loads- and within a much narrower window. In other words, the stupid factor is narrowed.

What kind of ant was that? for that info, you might want a 20 series profile