Advanced Suspension Mods

[Advancedynamix]

There is a poly bushing for the sway bar pick up point, it's sold Tein I think. I don't have them in my car but they are most certainly a worthwhile replacement.
My camber is set at -2.3 to -2.8 depending on the coarse. With my current setup the camber gain is nearly a degree per inch tapering to .5 dpi at the bottom of the shock travel. Like I've said before, the design of this chassis is exceptional. My tyre wear isn't from a loss of camber, I'm simply exceeding the lateral load capacity of these tyres. They are folding under when pushed to the limit. More pressure helps with that, but traction is sacrificed, so that tells me that they are at their limit. My temps and treadwear are very even, I just use a lot of sidewall too. Lol.
Adjustable sway bar mounts with poly bushings would help a lot. I think more caster could provide a little more support under hard long corners where I'm currently rolling the sidewall. It would be a simple part to make that would bolt to any festiva.

I will make some chassis adjustments when I build the dedicated track car, but this car will remain stock aside from bolt ons and the removable lower rad support. I'm using this car to test the absolute limits of the stock festiva chassis dimensions. This chassis can handle more rubber than it has room for without losing it's form. The next test will be 7" wide slicks slightly more spring and 100 more hp. It keeps up with 600hp awd turbo Porsches now ( in the corners, not the straights). Not too bad for an essential stock chassis econo box!
I want this car to represent what is possible with simple bolt on modifications. It's a very well setup chassis from the start, it's not hard for me to out corner Miata track cars that have more track specific modifications and more tire. That's an awesome testimony to the capabilities of this chassis.

Thanks for the input, and suggestions. I'm going to start planning out some adjustable sway bar plates and order some poly bushings ( she can get a little squirmy under hard braking).

[Arnie]

Geometry ideas, Group N style

So you're still getting outside tire wear? How much neg camber are you running?

A common problem that most people who lower their cars (respectively over lower) are the geometry compromises such as camber curve and roll center. Judging from your pic of your car mid corner, you look fairly low so I can imagine that your control arms are past "horizontal" and that your outside wheel will be pretty much folding under in a turn. Basically, from the get go you're already in the "bad" portion of the car's camber curve. I never plotted the curve on the Festiva but I'm fairly certain you're there. Being that low you've also lowered your front roll center. Its probably subterranean, so you'll also be getting a lot of roll through that.

I was looking at some pics of a member's Festiva and thought of a couple of "Group N" type mods you might be able to make to help roll center, get you into the decent meat of the camber curve and get more caster.



You can do two things to raise roll center and help camber curve issues.

1. relocate inside pickup point. Since you're a metal smith of some talent you could see about raising the inside pick up point a bit. You'll have to see if there is actually enough room above the control arm to do so. But raising that pickup point about 5-10mm would help tremendously.

2. Bend control arm/ball joint downwards a few mm. You can see in this pic that there is potential to move the ball joint on the control arm down past the sway bar mounting point. Depending on the arm material, you can just put the arm in a press and cold bend that area downward. This is a sneakier method that no scrutineer will see!



Looking at this photo, I was thinking about how you could gain caster without having to go the adjustable top mount method.

1. In addition to bending the ball joint area downwards for roll center correction, you can also move them forward a bit. Maybe 10mm. This will increase your caster. You'll need to adjust your toe afterwards, of course.

2. Relocated the sway bar front mounts. Looking at this pic, the sway bar also functions to located the strut position. I'm thinking, if you could move the front sway bar mount forward a bit, it would pull the whole suspension assembly (control arm/strut) forward. Only question is, is there room and material for you to do this?

I can't remember, but is there a bushing replacement for the inside control arm pickup point? If you could get a poly replacement in there, it would definitely help reduce dynamic caster loss on braking too.

[Advancedynamix]

Great thread and great custom work!

Reducing rear droop is a very common suspension mod for FWD touring cars in Europe. My friend used to run a Clio race team and that's something they also did. I'm also impressed with the use of the narrow ID springs/setup you use as it solves a lot of clearance issues. Gives you a bit more room to play with available wheel offsets or spacers. I had clearance issues using the TEIN coilovers on the rear of my car using Miata wheels. I had to run a rear spacer to get the proper clearance.

Have you played with increasing caster a bit? I never got a chance to play with that on my Festiva but was on the to do list.

I haven't played with Caster much on this setup. The car could use a little more caster to gain some camber under hard turning. I chew up the outsides of my tires pretty good. As far as stability goes though, this car is rock solid at speed. It would be nice to be able to add caster when I increase rake, I have found that the car gets nervous with too much rake and i think that it's due to the reduced caster angle. Being able to add more rake without sacrificing stability would allow me to put more power to the ground and carry more corner speed. It also would be an aero improvement. Now to just make adjustable caster plates that still look completely stock.

[nitrofarm]

Thanks for the clarification !

[Arnie]

Great thread and great custom work!

Reducing rear droop is a very common suspension mod for FWD touring cars in Europe. My friend used to run a Clio race team and that's something they also did. I'm also impressed with the use of the narrow ID springs/setup you use as it solves a lot of clearance issues. Gives you a bit more room to play with available wheel offsets or spacers. I had clearance issues using the TEIN coilovers on the rear of my car using Miata wheels. I had to run a rear spacer to get the proper clearance.

Have you played with increasing caster a bit? I never got a chance to play with that on my Festiva but was on the to do list.

[Advancedynamix]

do you have the ebay link for the bushings?

All bushings on this setup were are home made.

So with a fast Damp slow Rebound in the valving.Does it roll more in a very high speed gradual curve?

Yeah, there is more roll on long sweepers, but not nearly as much as with most suspension setups. The rear shock length regulates the amount of body roll, instead of using a sway bar. This allows the car to easily soak up imperfections in the track (i.e. rumble curbs or when I hang a wheel off into the dirt) without upsetting the car. Body roll isn't always a bad thing either.

[QUOTE the raceland coilovers come apart fairly easily so they don't need to worry about overheating the strut insert when they weld in the bushings. You'll need a loose knuckle to have them match the pattern.

Am I the Dunce of the class?Or the only student paying attention? Where is this step? Did you seperate that steel clamp that surrounds the strut? All I see is the elongated upper hole.Or is that a HAT BUSHING in the lower hole? drool[/quote]

I made 1.250" o.d. bushings for the lower holes out of steel round stock. I did this because I set the strut body up in a mill and indicated off the top hole, I then used a 1.250 end mill to plunge holes in the proper spacing to fit a festiva/aspire/capri/rio/323 ect ect spindle. I then elongated the upper hole to allow for camber adjustment. Then I bolted the strut body to a knuckle, and bolted the bushings to the knuckle as well and welded the bushings to the strut body. This makes the VW strut fit the Mazda/ford bolt center properly and allows for lots of camber adjustment. I'll try to find more pictures of the process, sorry if it's confusing. It was just my way to make those lower strut mount holes line up the properly. I tend to overbuild things, but I'm not easy on equipment so it pays off in the long run.


Here you can see how there is a bushing welded in to fill in the 1.250 holes that were plunged through the bracket. I did this to drill out the stock hole entirely since the hole was in the wrong location for a festiva. I think other people have just opened up the holes a bit to accomplish the same thing. I am extremely hard on my suspension, so I wanted to add strength to this area. I check the welds regularly and haven't noticed any indications of fatigue.

[nitrofarm]

[QUOTE the raceland coilovers come apart fairly easily so they don't need to worry about overheating the strut insert when they weld in the bushings. You'll need a loose knuckle to have them match the pattern. [/QUOTE]
Am I the Dunce of the class?Or the only student paying attention? Where is this step? Did you seperate that steel clamp that surrounds the strut? All I see is the elongated upper hole.Or is that a HAT BUSHING in the lower hole? drool

[nitrofarm]

The bump stops don't actually stop the shock travel, they are simply there to raise the spring rate. They can be used to limit travel, but that's not what I use them for. The car will lean about an inch and then the stops progressively raise the spring rate on that corner. This isn't to induce overseer or to rotate the car at all. What this does is it allows the front inside tire to get traction when the throttle is rolled on using the outside rear bump stop (the extra spring rate works in conjunction with engine torque to keep from losing traction) To rotate the car I use the brakes and the front bumpstops do the exact opposite of the back, they take weight of the rear tires. Bump stops can be used to fine tune the spring rate of each corner. They can also be used to correct shock valving issues. On a front drive car I like to use fast compression dampening and slow rebound, this will stick the front end to the track when you brake before a turn and limit the amount if weight transfer to the rear under acceleration. The bump stops can be used to fine tune this.
Hope that helps.

So with a fast Damp slow Rebound in the valving.Does it roll more in a very high speed gradual curve?

[alpaccino]

Here is a little parts list for some of the components I used, where to find them and the cost.

KYB shocks for the Aspire/Festiva 116.00 for the pair. Ebay http://www.ebay.com/itm/2-Rear-KYB-G...ecb796&vxp=mtr

Small body shock sleeve kit-54.00 a piece, 2 required. Here http://www.ebay.com/itm/New-Bilstein...ab4dbc&vxp=mtr

1 7/8" 10" I.D. springs- 35.00 a piece (when shipping is split between 2 springs) here http://www.ebay.com/itm/NEW-MIDGET-R...bbb547&vxp=mtr

Raceland VW mk2/mk3 coilover kit- 400.00 est. go to raceland.com or here is a set on ebay. http://www.ebay.com/itm/1989-1992-vw...c6e16a&vxp=mtr

2 1/2" x 10" front springs- 35.00 a piece (with combined shipping of 2) on ebay. http://www.ebay.com/itm/NEW-RACING-C...304e4d&vxp=mtr

do you have the ebay link for the bushings?

[alpaccino]

you re a creative genius. could u put a kit together,and sell it to the club? ill buy one

x2

[windy1]

genius

you re a creative genius. could u put a kit together,and sell it to the club? ill buy one

[Advancedynamix]

Here is an example of how much pressure is being applied to the inside front tire even without a rear sway bar. This corner was being taken at around 85mph, under power with 40psi hot in the front tires. You can see that there is enough weight on the inside front wheel to distort the sidewall of the r888. The bump stop on the left rear is doing it's job at keeping the weight where I need it.

[Advancedynamix]

Rear roll control is a very important aspect of tuning an FWD chassis, but it's not the most important. The most important factor in the dynamics of any chassis is weight and its distribution. The trick is to keep as much weight over the driving wheels as possible. This is especially challenging and important in a front drive chassis since the driving wheels are also directing the car and handling roughly 80 percent of the braking. There is no right or wrong here, and a roll bar is an easy way to tune the anti roll, but it's not the only way. I prefer to fine tune the ride height, tire size and compound spring rates, shock travel/valving and alignment settings without using sway bars. Then, when everything is working together in balance I'll ad a sway bar as necessary.
with my festiva, I've found that a rear bar isn't necessary on an average road coarse. With my current setup the car will pivot controllably with moderately quick throttle lift yet it isn't a handful under trail braking. This is with the stickiest commonly available street legal tire that will fit inside a stock festiva wheel well. Wider tires or slicks could most likely make use of some rear bar. This is also with a heavier than stock engine/ trans that is moved 2" forward of axle centerline in comparison to a stock drivetrain. This is also a fairly stripped out car with no roll cage, so the weight of the cage and/ or interior could warrant the need for more bar. As far as this car goes though, more rear bar would slow me down. Things would be different on a really tight coarse or autocross, but I'd probably opt for higher rear ride height and stiffer/ taller bump stops. That changes my caster and puts more weight over the front wheels. The easily removable sway bar is a great idea though and I'd like to see pictures.

[jemartin144]

The festiva racecar. There is almost 0 droop and maybe and inch of actual travel. I havent had a chance to get all the real numbers yet. I'm hoping to get the whole suspension modelled up sometime this summer and do some real analysis on it.

[Advancedynamix]

An inch of travel on your festiva or the formula car?