twat

I have a Weltmeister 28mm front swaybar and I cannot get the thing to quit making noises. The linkage pops and clicks anytime the body rolls. Part of the problem is that I have 250 lb springs up front and stock torsion bars in the back…so I have the front swaybar set on max soft.
When the adjusters are in the max soft position, the linkage geometry is unfavorable and I think it's binding, hence the horrible crunching sounds. I could set the adjusters to a stiffer position (which would reduce the relative angle of the linkage) …but then the car would push like Buick.
As I see it, I either tolerate the noises or I get the right torsion bars.
Any suggestions?

Skip

I'm not sure what relationship you are thinking about with the T-bars and the front stabilizer. However, the Welt bar is a known noise-maker - both from the bushings if not lubricated regularly, and from the binding. If it's binding, you certainly need to work on the geometry in the static position to prevent this (loaded suspension... can be done on ramps or a wheel-lift). The 250# spring and the Welt bar should work just fine together, certainly if you have it set soft. Be sure to lube the bushings with a moly... some folks have even fitted Zerk grease ports into the clamps, and modified the poly bushing to have grease channels.

Good Luck!

twat

Thanks Skip.

[quote]I'm not sure what relationship you are thinking about with the T-bars and the front stabilizer.<hr></blockquote>

I thought my explanation would be ambiguous.
The relationship is that the stock T-bars are really soft compared to the 250 lb front springs. So in order to keep the car from pushing, the front swaybar has to be set to max soft, which results in the problematic linkage geometry

Skip

Ahh, now me gets yur drift. What sway bar do yu have on the back? The 22mm Welt is the companion.. anything much smaller and you're dramatically increasing the the natural tendency for the car to push.

Skip

Danno

On my Weltmeister set-up, I usually have the front set to max full-stiff and the rear around the middle. I actually went and cut off about 1.25" off the end of the front sway bar since I never use the full-soft setting anway (saves 2.5lbs total). I find that the rotation of the bottom heim-joint makes a big difference. As you side the clamp up and down the swaybar, you also need to loosen and rotate the lower heim-joint on the A-arm as well.

I've got 350lb/in front springs with 25.5mm rear torsion bars.

twat

Yeah, I have the 22mm in the rear, set to MAX STIFF.
Just for future referance, what size T-bars should I shop for? I'm gonna buy the ground control setup and get 300 or 350 lb springs. Jason said 29mm T-bars would be good...
What says Skip?

Skip

He's so full of it!

29mm it is then... [like I would bite the hand that feeds me ]

Seriously, For more info on spring rates when talking T-bars, check out this Tech-Session article:

<a href="http://www.tech-session.com/Paragon/Info/944_tbar_rate_comparison.htm" target="_blank">Rear Wheel Rates</a>

Generally, 250-300 front - 28mm rear, 300-350 front - 29mm rear, 350-400 - 30mm rear. [oops, was that secret?] There are other factors, but this is a fair guide. The front spring rate is ~90% effective, so taking into consideration that the car is neutrally balanced (50/50), you want the front and rear rates to be close... to a point... once you exceed ~400 on the front, the rears should not try to keep up.... and most agree the rear should never exceed the front.

Skip

*Rothmans*

Danno, with your set up, how is ride quality on the street and the track? I just picked up some Weltmeisters myself and would appreciate some set up help.
Have you ever considered going with heavier torsion bars or a helper spring arrangement?

Matt

Danno, I'm amazed by the difference in stiffness front to rear on your setup, and I just have to ask how it handles.

I've changed everything around since then, but a few years ago on my 924S I had 250# front springs with a factory 24.5mm front bar, and stock torsion bars with a Weltmeister rear swaybar set stiff. Much less of a differential than you're running, but even with that setup the understeer was severe at speed. It wasn't too noticeable on the street, but was awful on the track. I ate up front tires (225/16 front, 245/16 rear) at a terrific rate.

Matt
Lifetime Member

Manning

Yah know Skip, I was just going to post a topic regarding what the actually wheel rates are for various front springs, and for the most part you just answered it.

So a 250lb spring in the front will have roughly a 225lb wheel rate, is that about right (I am kind of a math moron so bear with me here)? And that would pretty much match a 27mm bar which has about a 220lb wheel rate.

As an additional question, is a 25.5 or a 26 t-bar a better match for a 200lb front spring? Based on your post, you don't want the rate in the rear to exceed the front. In that case a 25.5 would be perfect (175lb wheel rate rear to a 180lb wheel rate front) but are hard to come by, right? A 26mm bar is easy to find, but has a 189lb wheel rate, which would be a few lbs more than the front wheel rate, is this going to be a problem? I ask because I may not want to go too stiff right now and 200lbs may be right for me.

Wow, math is fun

Danno

Just to be clear, spring-rate and wheel-rate are not equivalent (on is an integral of the other). Wheel-rates is a function of the square of the wheel travel (^2). What you are really referring to is 'motion ratio'.

"with your set up, how is ride quality on the street and the track?"

Going with the Weltmeisters at their full-stiff settings yielded a tremendous improvement in roll-stiffness (I would say close to double the 968 M030 set-up I had earlier). And they definitely don't hurt the ride quality as much as stiffer springs of equivalent roll stiffness. Combined with my front 350lb springs, it's on the verge of becoming a dedicated track car. Even with the Welts dialed back to full-soft after I get off the track, the ride is quite firm, but not unbearable. I would say 400lb front springs is about as much as you'd want to use on the street.

Some people seem strangely surprized at my suspension set-up, but it's a racetrack configuration whereas most people are familiar with a street car suspension settings. That's partly because on the street and street-type driving and autocrosses, most people tend to drive over the limit of the car. This is where understeer vs. oversteer balance rears its ugly head. But if you are driving a car consistently up to its limit, and not over, there's no difference between understeer vs. oversteer since the car hasn't overcome the traction limits of the tires and isn't sliding.

Check out the suspension settings of the high-end stock-based racecars like TransAM, SpeedvisionGT, ALMS and you'll see a pattern; a lot of them run front spring rates that are close to double the rear rates on a close-to 50/50% car. This has several benefits. First it keeps body roll to a minimum so that the outside tires don't experience detrimental positive camber-changes. Another is rear wheel drive traction. You won't be picking up the inside rear tire and spinning coming out of corners (even without an LSD). This allows you to get on the gas earlier in a corner and get 5-10mph more down the straightwaway. This makes a significantly higher contribution to fast laptimes than any kind of a understeer or oversteer comparison. If you are driving over the cornering limits of the tires where understeer vs. oversteer makes a difference, then you're not getting fast laptimes anyway.

*Rothmans*

Danno,
I am fascinated by this set up for racing.
My car has the stock 24.5 mm bars from it's
racing days. I was going to go for a cup helper type set up but I think I might go for 25.5 mm bars as well.
In your opinion would the progressive rate turbo cup front springs I have work well with the 25.5 mm torsion bars?
I am not a big fan of real stiff springs, and I have all spherical bearings to let things move as they should and avoid geometry changes.
I think your title should be "racing sensei"
by the way..... <img src="graemlins/burnout.gif" border="0" alt="[burnout]" />

Danno

Hmmm, I'm not terribly fond of rising-rate springs. But the Turbo Cup springs aren't as dramatic as some of the other rising rate 175-450lb/in springs out there.

What typically happens under cornering is that the inertial weight-transfer is fairly evenly split between the front and rear wheels (depending upon spring & swaybar rates). As you approach the cornering limit of the front tires, the feel in the steering wheel goes from stiff with resistance to a light vague wandering one.

With rising-rate springs however, the inertial weight transfer is only evenly split under light cornering loads. As you increase speeds and come closer to the cornering limits of the tires, more and more of the weight transfer goes to the front wheels. This makes the steering feel vague sooner due to the extra load the front wheels. One way around this problem is to use rising-rate springs in the back as well.

But even then, it doesn't address the issue of rising-rate shocks to match the rising rate springs. Shocks that dampen the body's movement fine in straightaways become too soft when the springs are compressed enough to get into the higher spring-rate ranges. That means you'll have more body movements from the front-end if you hit those same-sized bumps in a corner under full cornering. But since only the front end will have this problem, the result will be a porpoising & wallowing body; not conducive to great cornering.

So a quick answer will be that the 25.5mm torsion bars should be fine on your car. We have to remember that the TurboCup cars are about 500lbs lighter than the normal Turbos, so those 25.5mm torsion bars may be equivalent to 29-30mm bars on the street Turbos.

*Rothmans*

I think I have been enlightened.
What I will do is leave the factory M030 type springs in for now as they will be a better match until I go to a helper spring arrangement.
That is unless I find a pair of turbo cup rears in the meantime...

Thanks for the advice, and I will let you know how the Weltmeister tuning goes. I have been told that they are junk, get rid of them, go for the 968 M030.

I think I will make up my own mind!

Skip

[quote]Originally posted by Manning:
<strong>Yah know Skip, I was just going to post a topic regarding what the actually wheel rates are for various front springs, and for the most part you just answered it.</strong><hr></blockquote>

Some might say I'm psychotic that way

[quote]<strong>So a 250lb spring in the front will have roughly a 225lb wheel rate</strong><hr></blockquote>

yup

[quote]<strong>And that would pretty much match a 27mm bar which has about a 220lb wheel rate.</strong><hr></blockquote>

yup


[quote]<strong>... is a 25.5 or a 26 t-bar a better match for a 200lb front spring?</strong><hr></blockquote>

25.5mm... because they're take-offs and would be much cheaper than aftermarket with no real difference in rate.

[quote]<strong>Based on your post, you don't want the rate in the rear to exceed the front. In that case a 25.5 would be perfect (175lb wheel rate rear to a 180lb wheel rate front) but are hard to come by, right?</strong><hr></blockquote>

Not at all hard to come by... anyone who's upgraded a late turbo, S2, or 968 has these leftover... and owners should hand them over for $50-100.

[quote]<strong>A 26mm bar is easy to find, but has a 189lb wheel rate, which would be a few lbs more than the front wheel rate, is this going to be a problem?</strong><hr></blockquote>

Not really, but here's the flip-side. It's generally accepted that if you are going to the trouble of replacing the T-bars (long, tedious, expensive job), then 28mm should be the minimum you upgrade to (254# wheel rate, and *acceptable* to use with the widely available 250# front springs... usually with the addition of a stiffer front stabilizer). Obviously not everyone does this, as Danno has gone from 23.5mm to 25.5mm... probably because it's really inexpensive to do. So that's the key... he's increased the rear spring rate just far enough to allow a substantial increase in front rate... then used the adjustability and substantial increase of the Welt sway bars (front and rear) to counteract any mismatch of rates (if you subscribe to the near-matched rate philosophy being ideal).

[quote]<strong>I ask because I may not want to go too stiff right now and 200lbs may be right for me.</strong><hr></blockquote>

200# with your stock rear T-bars is fine... or even to 250# is acceptable for mild-mannered street cars... anything above that and you might start considering the ride a bit harsh for street-only... AND, you really should be stiffening up the rear somehow (T-bars, helper-springs). Ride quality is such a subjective thing... the reason some people drive Cadillacs , and some drive Porsches I'm quite used to the 400# rates on my car for street driving... but the viaduct seams in Seattle, and the Interstate to Tacoma usually knocks a few fillings loose!

Good Luck!