what size sway bars for my coilover setup?

[snodevil11]

I have 6" 700 pound springs in front and 8" 450's in back on my ipt koni coilovers on a 93 mtx. I now have a 26mm rear, 24 front and two sets of whatever was on my 2 stock 93 atx's ( all four in the low 20's mm somewhere, have not yet measured them, but look small). Anyways, I am putting the car together now and have not had a chance to test anything out, but am just curious about what may work the best and what sizes I should get to play with. Thanks

 

[snodevil11]

Oh, and has anybody who has the ipt coilovers have to modify a strut tower brace to allow room for the adjustment plate?

 

[snodevil11]

bump

 

[snodevil11]

bump, bump anybody???

 

[drivinhard]

If I was running 700 lb springs I'd toss the sway bars!

I run at Summit Point towards the end of june, a track that I'm used to, so I'm planning to test mine there since it will be an easy testing ground.

I'm running the same hardware, but changed out the spring rates. Softer, but taller (8" and 10"). The 6" (depending on load/rate) will coil bind well before the strut travel ends. Maybe with a 700# you might be ok, but wow that's a lot of spring for the street. I'm at 425# on the front, and that may be too much, but we'll see.

I'm looking to put more spring in the car (reduce dive under braking and squat under power), and take out some bar. Hope the net result is similar roll stiffness, but more control under hard braking. For the track, it's nice to get roll stiffness from the springs and not from sway bars. The stiffer the bar, the more you tend to pick up the inside wheel. The softer the bar, the more the inside wheel tends to stay planted.

The coilover hardware is lighter than the stock set-up, and skinny sway bars are lighter than fat ones to

 

[snodevil11]

well, I have not had a chance to test this out yet. I just got my setups put together and ready to install on the car. I bought this from someone else and not ipt directly, so at the time I was not that ( and still really aren't ) that experienced or knowlegeable with the spring rates and sway bar combinations setup on a sho. I was just told these things are tight and will handle like ****. Now that I am aware of how high of rates I have I may have to get a second or third set to play around eventually. For now, seeing I have no experience yet, I would just like a good piece of advice as to what size bar I should put in initially to start. Do you think the 26/24 combo will work ok in conjunction with these rates or will it throw it all off? You say that I should go with smaller bars? What sizes would you estimate to be a good start? I originally just thought that I would end up going higher, like the 28/26 combo as ipt sells or 29 sho shop adjustable with a 24, 23, or even a ipt 26 front. ??? I do have all tpr strut rod bushings, tpr 26 sbb, 24 poly front sbb, alum sfb, sfc's, h-brace, adj. rear cont. arms, and stb's f&r. I do know this will be one really bumpy and stiff ride. I guess I'll just have to carry around a bottle of asprin and put in some extra cushions laughing

 

[Toolman]

snodevil, I had the 600lb f and 350 r ( if I remember) with 24/26 combo. Loved it. Best handling SHO I have ever had the opportunity to drive, ON THE TRACK. On the street, unless my Koni's were at full stiff, the front bob'd a bit, and for rougher turns, it would skip around a bit. I think setting's like Mark's will be pretty good for the track, but still civil enough for street use. I will be putting some more coilover's on the turbo soon, but I will probably not have different spring rates then before until after the convention.

As far as the strut tower brace, yes, I had to modify mine. I had the Cincy braces. I just cut the hole a little larger and they fit fine.

 

[thebigjimsho]

19mm front and 26mm rear.

Nice and neutral on the track.

 

[snodevil11]

Thanks guys! I just finished the brace modification. It is perfect now. I have the shoshop design and it was a bear to cut that thick steel out by hand with a sawzaw and no vise. I think I damaged some nerves in my right thumb from all the vibration, but I got through it ok. As far as the sway bar, I guess if I won't have too bad of a reaction with the 24/26 combo, I'll start with using that and swap around later after I get some testing in.

Hey toolman, check out my tranny post and tell me what you think: http://www.shoforum.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=2;t=003197;p=1#000006

 

[FAST4DR]

Snodeveil,

I left the front 20.6mm swaybar on my setup because people recommended it for autocrossing, which I just did this weekend. But I think I am going to change to the 24 up front. My car pushes a little through the turns. (of course your setup is different) With my current setup my car handles awesome. At the autocross I attened this weekend I was running better lap times than the vettes. The people at the autocross could not believe how well my family car handled. They would cheer and clap when I came in.

Will

 

[snodevil11]

Thanks!

 

[K-Dawg]

FAST4DR:

I left the front 20.6mm swaybar on my setup because people recommended it for autocrossing, which I just did this weekend. But I think I am going to change to the 24 up front. My car pushes a little through the turns. (of course your setup is different)

By no means am I an expert on the subject, but won't going to a larger front swaybar make the car push more (more understeer)? Won't going to a larger rear or smaller front swaybar decrease understeer?

 

[Lance Cheney]

FAST4DR wrote:

I left the front 20.6mm swaybar on my setup because people recommended it for autocrossing, which I just did this weekend. But I think I am going to change to the 24 up front.

(where the heck did the quote function go?)

To which I would reply:

If it's pushing, you will want a smaller front bar or a larger rear bar. Put the 24 on the front and it will plow like a John Deere 8-wheeler.

I've only change the FSB three times in the last year (I'm sure there are others with more experience!), but can definitely attest to this.

-Lance

-Lance

 

[thebigjimsho]

Thanks Lance

Lance.

That's why I feel strongly that the 5-7mm difference from front to back makes a great handler on the track -- if you think you can handle a car with a little tailhappiness. boink

 

[FAST4DR]

Now you guys are starting to confuse me. I am no expert in suspension setups, but wouldn't the larger swaybar on the front keep the front end more level and keep the camber angle from changing as much. When the body rolls the camber angle is changing with respect to the ground.

Also the larger swaybar helps in the quick left/right transistions of an autocross. I would think that the flatter I can keep the chassis the quicker the transistion and weight transfer from left to right. So maybe I should put the 24 up front and then a 28 or 29 in the rear?

I want to keep the front from rolling over as much as it does. The rear is planted but I can feel the front leaning a little.

 

[Shuey]

go 26mm/28mm or 26mm/29mm combo. now thats handling.

 

[Lance Cheney]

Here's a good link:

More info than I want to type

I won't claim to understand exactly why a stiffer front sway bar introduces more push, but I can definitely vouch for it being true.

Speaking of... I need to lower my front caster (one side is at max, other side is ~4.2 degrees).

You might try a little more toe-out just for autocrossing if you have adjustable arms in the back. I have a coworker that does that and he claims it helps to rotate the car (so does the web page above).

-Lance

 

[K-Dawg]

I understand the concept, but I'm not that good at explaining things, so I won't get into detail and make it more confusing. It's not so much the size of the swaybars, but the relationship between the front and rear swaybars that causes the car to understeer or oversteer. A car that has monster swaybars front and rear will most likely not handle as good (be as neutral) as a car that has smaller bars and rolls significantly more, but has a better size ratio front:rear. Bigger is not always better.

 

[thebigjimsho]

FAST4DR:
Now you guys are starting to confuse me. I am no expert in suspension setups, but wouldn't the larger swaybar on the front keep the front end more level and keep the camber angle from changing as much. When the body rolls the camber angle is changing with respect to the ground.

Also the larger swaybar helps in the quick left/right transistions of an autocross. I would think that the flatter I can keep the chassis the quicker the transistion and weight transfer from left to right. So maybe I should put the 24 up front and then a 28 or 29 in the rear?

I want to keep the front from rolling over as much as it does. The rear is planted but I can feel the front leaning a little.

How freakin' flat do you want your car to be? I've posted best times in 3 autocrosses before. I've had nearly identical lap times with a Porsche Boxster S with R1's. If you want the flattest ride, go get 24/26, or whatever. If you want to enter a corner, apex and exit with as little oversteer/understeer(time eating loss of traction), get the smaller(19/20.6)front bar and 26 rear. You've got the right mods to control roll anyway.

 

[drivinhard]

You can get away more with a bigger from bar with a quaife and not push as much under power. In an ideal world, you want to get your roll stiffness from springs and not sway bars. This makes for a punishing ride on the street though (but keeps the tires on the track better). Big bars tend to lift the inside wheel off the ground.

For a typical weighted MTX car w/ a quaife, 22/26 is a nice compromise for street/track work. Auto-x is a different animal, as it's slow speed tight radius slow speed corners, you want the car to rotate as much as possible. Probably not the same set-up you'd want to run doing 100+ mph off turn 12 at Road Atlanta with the wall just feet away.

If you race your SHO, you'll have every sway bar size hanging on your garage wall, something for every occasion Every car, track/tire is a bit different. There is no perfect combo for everything.