Advanced Suspension Mods

[zoom zoom]

Alright Charlie I've got a question for you, why do my tires rub on the spring perches? There's a solid 1"+ gap between the tire and the spring perch, even though I'm in the negatives with my camber.

[Advancedynamix]

Sir, I take my hat off to you.
At first all I saw was genius... but now I clearly see PASSION...

Very inspiring. Don't ever leave our community.
If it were a sport, you'd be MVP.

Charlie, you do amazing work!

Thanks guys! I'll keep you updated on how this works.

Charlie, I will be running an automatic. So I will be able to preload things a LITTLE bit at the light.

That's right. Well, then you can get away with a stiffer spring rate in the back, but you still want a little weight transfer. I wouldn't adjust rate with the actual springs though, used the bumpstops, they are better for a fine tune.

[bhazard]

Charlie, I will be running an automatic. So I will be able to preload things a LITTLE bit at the light.

[Festevil3]

Charlie, you do amazing work!

[moz]

Sir, I take my hat off to you.
At first all I saw was genius... but now I clearly see PASSION...

Very inspiring. Don't ever leave our community.
If it were a sport, you'd be MVP.

[Advancedynamix]

Time for some teasers. Upcoming developments. 36mm Bilstein sport shocks for a mk3 VW. currently being fitted to Festiva with adjuster sleeves.

step one: get a box

step two: cut a hole in the box

Step 3: put your junk in the box

[Advancedynamix]

what if we were to incorperate the Rio front suspention (minus the anti-roll bar)? i'm thinking it would handle very much like my Justy does (i removed both roll bars and it feels much more planted, especially when i'm beyond the limits of adhesion.... i love 4WD!!)

You already know the answer to this question Arty. lol. The Rio has the answer to the ultimate festiva package. Make sure to suspend everything in oem style bushings as well, no solid mounts on those drag links. Isolating engine pulsation is a team effort between the engine mounts, the chassis bushings and the tires. Pulsation frequency and intensity are a huge factor in traction or the lack thereof. Also, you know how bad I want a Rust free JuSTI. so hard to find.

Even on the gravel twisties I cannot really put my justy and limits of adhesion in the same conversation! The VR-4 yes and the nitrous on single lane paved twisty...

The lifted festy is my go to car?? don't no why, I think its because there are so many different reasons it slaps a sheet eatn grin on my face! As a shop owner I do very little mods, it is hard to make a living wage unless they are all the same and that is not the game in a small town. But what I learned here about mods on a festy suspension has a lot to do with me preferring this little car out of the many rigs in the corral.

The Festiva is an automotive miracle. Your VR4's worst enemy is it's weight, especially on those twisties. May I suggest another 100hp in the Justy?

Charlie...what can you tell me about a suspension setup for drag racing? Hard as possible in the rear? What about up front?

Not necessarily as hard as possibe in the rear, you do want some weight shift believe it or not. On the strip you want to balance a couple of factors and suspension works together with your clutch release. This is sort of a dance to get ultimate grip while also protecting all the spinny parts. This is very critical in the case of people like yourself, JT, Greg and any of the other BPT crew (or KLZET). First, you'll want the weight in the car to be as forward as possible, remove anything you can from the back of the car because it's only hurting you. Second you want very slow rebound on your shocks in the front and very fast compression dampening (there are bumps on dragstrips and you need to soak up anything without disturbing the car). Now here is the difference between setting a FWD car up for the street and the strip, you want very little suspension travel in the front of the car. You want to set the car up with a lot of rake, but you also want a lot of caster to maintain stability. I would set it up with about -2 degrees negative camber in the front and -3 degrees in the back with the thinnest tires you can get in the back (if you shave the markings off of space savers and spray paint hoosier logo on them then you can get through tech with spare tires, I have done this on a few sub 10 second cars without issue, lol). In the back you only want about an inch of travel before you hit the bumpstops. I'd use a progressive stop with a fairly aggressive rate. Your back shocks should have slow compression dampening and fast rebound. The KYB gas adjusts for the rabbit have a much more aggressive compression, but you may even try Bilstein HD shocks for a MK1 VW. I would still only run 150lb springs in the back, but I'd run like a 180ish up front. Your TQ will hold the front up during the run, you don't need stiff springs up there, the softer the better, but again, a couple of inches of travel at most.
Even with my slipping clutch I have managed to get the jump on AWD cars on the strip on street tires. These cars are so damn light that, when care is taken on the launch, they get off the line pretty dang fast.
Get an assortment of bumpstops and use those to control your weight transfer, this is like adjusting the progression of your spring rate. You will find that some rearward transfer is a good thing, it's complicated, but with a Turbo car, your max TQ is not at launch because turbo engines build TQ with load (nature of the beast). You want your rear to rebound into the TQ curve, so it's actually pressing harder as the car is accelerating harder. Like I said, hard to explain, but you'll feel it when you get it dialed.

Another trick is to move your engine as far forward as you can get it. This not only puts more weight on the front tires, it also causes the front wheels to press downward with TQ load. If your axles angle back toward the hubs, the engine TQ will drive the suspension downward, much like on a dirtbike when you gas it while landing from a jump. They have been doing this on off road buggies since the 60's. if you look at most modern sand rails, they have a lot of backward angle on the drive axles, then watch them launch. Now take that same theory and put it in the front of your car.

[bhazard]

Charlie...what can you tell me about a suspension setup for drag racing? Hard as possible in the rear? What about up front?

[Movin]

Even on the gravel twisties I cannot really put my justy and limits of adhesion in the same conversation! The VR-4 yes and the nitrous on single lane paved twisty...

The lifted festy is my go to car?? don't no why, I think its because there are so many different reasons it slaps a sheet eatn grin on my face! As a shop owner I do very little mods, it is hard to make a living wage unless they are all the same and that is not the game in a small town. But what I learned here about mods on a festy suspension has a lot to do with me preferring this little car out of the many rigs in the corral.

[FestYboy]

what if we were to incorperate the Rio front suspention (minus the anti-roll bar)? i'm thinking it would handle very much like my Justy does (i removed both roll bars and it feels much more planted, especially when i'm beyond the limits of adhesion.... i love 4WD!!)

[Advancedynamix]

Side note: Droop in the front of a festiva is beneficial, on and off road, but body roll in the front is easy to control with shock valving and limiting the body roll in the back with less suspension sag. Typically, sway bars on the front of a FWD car are counterproductive, because to control body roll they take pressure off the inside front wheel and put more pressure on the outside front wheel. This means the car is still trying to lift the inside front wheel, it just feels less intimidating, but it's still not allowing maximum traction. Anti roll bars on the front of a FWD car will increase the cars tendency to understeer under power and while braking, so it's a lose lose. Body roll will only increase understeer while under power, it will actually help in initial turn in under breaking, so it's a lose win.

[Advancedynamix]

Okay,
I've gotten a few more questions from people, so I'll update this thread a little more.

Rear spring rate: One important thing that we need to understand is that coil springs typically have a rising rate. Wether it be linear or progressive, the rate of a spring goes up as the spring is compressed. I suggest that people who want to do the rear coilover setup with stock length shocks use 120lb springs rather than the 150lb that I run on my shortened shocks. This is because the longer shocks need to sag 3" inches more than the short shocks. The spring rate will be the same when the springs are compressed. The actual static spring pressure of a stock festiva is closer to 170-180 lbs, but if you were to run 180lb springs the car wouldn't sag much at all. This sag gives you your height adjustment as well (increasing the spring preload will raise the car, but he static spring rate will still be the same). If you run too stiff a spring, your not really making the car any stiffer (unless you go over 180lbs, and I strongly discourage this) you are just raising the ride height of the car. If you run 150lb springs on a stock length shock, you'll most likely ride at a stock height or higher, if you run 120lb springs then your car will sag, and you'll have height adjustment from lower than stock, to higher than stock. If you run even softer springs then you'll have even lower ride height. I don't recommend too much sag however, because it will encourage body roll, and your car will not be fun around corners. a lower center of gravity is not more important than proper free sag or proper shock valving.

Sway bars: I have commented on this before, but I'll briefly say it again. Sway bars are a last resort in the quest for better handling. Proper shock length, spring rates and shock valving will control body roll much more effectively than sway bars. Also, sway bars limit the independent movement of your suspension system, so the car will be less compliant and the chassis will disturb more easily. Having independent suspension (yes the trailing beam on your festiva is a very independent suspension) is a very valuable attribute in real world driving.
When are they necessary? when you can't live without lots of suspension sag or "droop". This is seldom the case on a festiva, because the rear wheels don't ever need to get driving traction, so droop in the rear does us no real benefit. If a Festiva was rear, or all wheel drive, and you were driving over very rough terrain then droop would be necessary and beneficial and you'd want some way to control the body roll at higher speeds. Does this mean a lifted festiva needs a sway bar? Nope, actually a lifted festiva probably has less sag or droop than the stock ride height festiva, because the shocks are more extended at static ride height. That means a lifted Festiva is less likely to need sway bars, which is great because sway bars really don't help much in the rough terrain that a lifted festiva enthusiast may want to explore. There are always exceptions to these rules, but this is the basic theory in lightweigh front drive chassis setup.

[Advancedynamix]

I was going to take the plunge and go mk1 coils all around, no matter how unhappy my butt might be afterwards.

MK1 front struts are a much more difficult adaptation than the MK2. The width of the strut to knuckle mount is wrong for a BF Mazda. Also, with the 2 1/2 inch coil springs on the back, you'll have far less tire clearance than the 1 7/8" setup. Basically, I've looked into that, and it wasn't worth the effort. If you could somehow get a manufacturer to send you Mk2/3 fronts, and Mk1 rears and then machine the rear spring adjusters and hats to accept 1 7/8" springs then you would have a really great setup. I have tried this, but I don't feel there is enough interest to buy this setup (I'd need an order of over 100 sets to get the price down to 4-5 hundred bucks a set). I wanted to order VW rabbit pickup coil overs instead of the Mk2/3 because they only come with the fronts (backs are leaf) so I can get them much cheaper, but the fitment is a no go.

[TominMO]

I was going to take the plunge and go mk1 coils all around, no matter how unhappy my butt might be afterwards.

If you do, pleez inform us as to what your butt thinks of the arrangement.

[defprun]

Good plan. I actually stumbled across this by total strange coincidence. I was at a salvage yard here in town and I noticed a new KYB shock box in the back seat of a BF Tracer hatch. I checked the box and wouldn't ya know it had a brandy new shock in it, but I knew it wasn't a BF shock (I was hoping it was since then it would fit my Capri). I brought it over to a festiva and eyeballed it and decided to rub some dirt on it and buy it for like 10 bucks. I at home I looked up the numbers and it turned out to be a MK1 vdub shock. Funny thing is, I have bought these new a few times in the past, I should have recognized it. I'll have more info later this week on the ride and fitment. These probably won't be as good of a choice for low HP street cars, but that's what I'm trying it on first, so we'll see.

I was going to take the plunge and go mk1 coils all around, no matter how unhappy my butt might be afterwards.