Spring Rates?

Spring Rates? Please Comment!

I spent some time last night digging around the interwebs (now you know how exciting my life is) for info on setup for my Golf for this coming track season. I have Koni Coilovers, and last year ran 550F/350R springs, no front bar, and a Shine race rear bar, which is very stiff. This is how the car looked at race height.

I was running about -2 degrees camber in front, using Ground Control Camber plates, and I didn't play with rear camber. The car would push a bit, but not a ton. And it barely lifted an inside rear wheel on corners, nothing like it did with the Shine setup.

After I wrecked the Golf I ran IBW with the same coilovers, but first with 550F/700R springs (that's right, 700), and then with 700F/550R. It also has a Shine bar, but not a race one. And I disconnected the front bar. I tried the stiffer rear springs at the recommendation of a guy who drives a NB, who told me that with stiffer rear springs you'll get more rotation. I honestly couldn't feel it. What was also interesting to me was I had inside tire wear front and rear, even with -2 camber. That's not a lot. With these springs the Jetta had zero body roll, felt very controllable, and didn't lift a wheel. But at times it was a little bouncy, like it was over-sprung. I've been told by Koni that the coilovers can accommodate spring rates up to 700 lbs. I think the problem, however, was that the springs were just too stiff to allow any compliance given the weight of the car (2780 lbs. in race trim).

This year: I'm hoping the Golf will weigh in at about 2,500 lbs, (it was 2,635 last year) and most of the 135 lb. weight reduction will come off the nose of the car. That will make the nose about 1500 lbs. instead of 1635 or so as it was last year. It means the weight distribution will be 60/40 instead of 62/38. That's a good thing.

Originally my plan was to eliminate the rear bar and run 550F/400R with no bars at all. But my research has provided lots of conflicting data. Some people say run stiffer rear springs with no rear bar, others say run a front bar because if you get the front springs stiff enough to prevent body roll you'll have too much spring for track irregularaties. And I'm probably going to get the car a bit taller front and rear for best possible geometry. And this year I'll have a Quaife so the front bar/traction issue isn't relevant.

Here are my options:

1: 550F/400R, either with or without the rear bar
2: 400F/550R, no bars at all
3: 300F/300R, 26mm front bar, Shine rear bar
3: 350F/200R, 21mm front bar, Shine rear bar

The third option is closest to (as near as I can decipher from the spec sheets on VW Motorsport) the Golf 4 tarmac setup. They used a 30mm front bar which I don't think is available, and I'm not sure what they used in the rear. Also, I'm certain that their car was lighter than mine will be, which is why I'd go for 300 lb. springs instead of the 250 they used. The Shine VR6 Front springs are supposed to be about 250 lb., and they were way too soft for the track when running w/o a front bar.

The fourth option is running the springs that came with the Konis, putting the front bar back in the car, and leaving the Shine bar in place. Aside from cost (zero), the benefit of this setup would be much better compliance for bumpy tracks, and the fact that I know the dampers are valved well to work with the springs. Ride quality would be better going to and from, but I never really minded the 700F/550R setup in the wagon, remarkably.

I want to limit body roll and lifting the rear wheel, because both result in less grip. I'm hoping the weight reductions I'm doing will improve front/rear balance. And since this year's events with my club are mainly on rougher tracks (NHMS, Tremblant, Watkins Glen) I want to be sure I'm not over-sprung. The Golf will be a good 200 lbs. lighter in the nose than IBW.

I know TDIClub isn't exactly the center of the universe when it comes to racing, but I don't seem to be finding a lot of good data elsewhere. Most people make a few suggestions, then say it's better to simply buy a Honda, because it's lighter, has a better suspension, and makes the same power. That's not really helpful.

So let me know your thoughts, especially if you've tried setups on the track that you think have worked well for you.

Thanks!

I'm not an expert on race setups, but I do watch and attend a number of races. I also do wheel alignments for a living and have had a number of guys with custom specs come in for alignments for their race cars (a couple guys who do SCCA and NASA with Miatas and some AutoXing WRXs and one Saturn Sky).

I'm not entirely sure lifting one of the rear wheels is such a bad thing. Almost every FWD SPEED World Challenge Touring Car I've seen lifts the inside rear wheel clear off the ground when cornering (and most of these guys have sophisticated independent rear suspensions). Even if the tire doesn't lift off, it's effect on handling is very minimal.

I personally think having a front bar is best. That way you won't have to run such massive spring rates. Now what size to go with is something I can't help you on. It's all trial and error. Try a stock bar with stiffer than OEM springs (just not quite to the extent you've got them now!).

When you think about it, the sway bar is limiting body roll not only by sort of lifting up on the inside wheel, but is also using that inside wheel's spring tension to sort of increase the spring rate of the outside wheel. So in some sense, using softer springs with a bigger bar is somewhat like using a stock bar with stiffer springs when the car is fully loaded in the corners. There's a LOT to play with in that respect.

Stiffer springs will yield quicker response, but if it's too stiff it'll make it too easy for the tires to break traction over uneven surfaces and ultimate grip may suffer depending on the surface.

Then of course there's also the fact that camber angles change as the steering wheel turns (camber roll due to caster) plus the extra changes due to how the suspension is loading or unloading.

I would personally use the OEM sway bar or a slightly stiffer one and play with spring rates from there.

As for the tire wear; you can offset it somewhat by running a little extra toe-in. OE Spec calls for 0.00 degrees, but they also typically have less than 1 degree of negative camber. Toe-in can hurt steering responsiveness to an extent, but with a limited slip on the way, I don't think I'd worry too much. Just try maybe 0.10 degree of total toe in front.

Adding a little toe out (negative toe) may increase responsiveness and possibly make your ultimate grip a tad better, but it will rape the inside edges of those tires due to both the toe and camber.

Nothing here is an exact science when you don't have the telemetry equipment necessary to guide you! It's all old school trial-and-error. Gets expensive, doesn't it?

Matt, thanks for the comments. I'm leaning towards what you suggest, putting the stock front bar back in, keeping softer springs (if you can call 350 soft) and keeping the back bar. The thing I don't like about tons of roll stiffness in the rear is that basically you're reducing rear grip to help the car become more neutral. What I'd prefer is more front grip. I read one post where someone was running larger front tires, but I don't want to go there. Being able to swap front-to-rear helps a lot in prolonging tire life. When you're running tires with a 60 tread wear rating every bit helps.

I have to look at the alignment specs from last year, but I think I was running .3 degrees toe out. Perhaps that's where the inside wear was coming from. I like your suggestion about the toe in, and I'm probably going to slot the ball joint bolts a bit to get more negative camber. Ideally I'd like to run 3 degrees.

Trial and error is right. And you know it's getting expensive when the alignment shop knows my voice when I call for an appointment.

Peter,

Over the years, I've considered tinkering with the swaybars. Many say using a large FSB requires a larger RSB. I've wondered about leaving my Shine RSB in place and then still adding a set of "regular" swaybars such as those from H&R or Neuspeed. That may keep the car fairly comfortable on the street, but allow extra spring rate to come into play during hard cornering. I dunno. It could be really CRAZY, too.

Good Luck,

Scott

Scott: I also think people have different opinions about what works in autocrossing compared to a road course. Several posts I read said that a bigger front bar is a benefit when autocrossing, except for how it compromises traction if you don't have some kind of limited slip.

Besides, everything works better on an A3. They are set up better from the factory.

IndigoBlueWagon said:

Scott: I also think people have different opinions about what works in autocrossing compared to a road course. Several posts I read said that a bigger front bar is a benefit when autocrossing, except for how it compromises traction if you don't have some kind of limited slip.

Besides, everything works better on an A3. They are set up better from the factory.

Click to expand...

Plus you can adjust camber from the factory! No need for cam bolts or cam plates

Whole lot easier to change front struts, too!

Now if only we Mk3 guys got some better turbo and manifold upgrades like the ALHs can

BTW Peter, loving the new downpipe

Does Shine still offer articulating rear perches?

Not really. I wish they did.

I still have a set of mk4 rear camber plates (vw motorsport ones) if you want to try them Peter. They are no longer available. Let me know.

Hey Peter, since I'll be seeing you in a couple of days and I'm short on time to type a big response right now, I've got 2 books that might be of help to you. They're geared towards oval racing, but you just ignore all of the left specific stuff. Tons of good info.

Once you get your chassis set up, don't over look two extra rims with wider or race specific tires for track only days. You definitely want to rotate tire front to back while commuting, but nothing beats quaility front tire grip. That is if you're racing to win.

it is OK to three wheel. definitely means you are getting good grip.

if you want to three wheel less, then you need to ditch the rear swaybar and upp the rear springs to 500-600+

with a set of good shocks the rear will remain planted over bumps and surface irregularities. see www.hotbits.ca and ask for Peter.

there are some other ways to improve if you are feeling adventurous...