Serge944

Why is he wrong? Lowering a car changes the geometry and therefore a different static angle between the balljoint pin and control arm. With the normal range of motion of stock springs, the pins bind and damage themselves and the control arm.

God bless steel arms and all their easily-rebuildable glory!

Geo

Reread what you wrote.

First of all, lowering a car does not change the geometry. It just moves the suspension to a different place within the geometry. It will change alignment settings, bump steer, and the like, but changing the geometry requires relocating mounting points. To quote the late great Carroll Smith: "The geometry of any wheel suspensin system determines the linear and angular paths that the wheel and tire will follow when it is displaced from teh static positoin..." Lowering simply relocates the wheel/tire within the path.

If in fact the pin can bind within the normal range of motion, it has NOTHING to do with lowering the car. It has to do with a design flaw because an unlowered car can bind the pin as well. If, however, the length of the stock strut prevents this, it's STILL not a matter of lowering. If someone installs short body struts, THAT becomes the reason, not lowering. I'll bet you my next paycheck I can lower a 944 2.5" and make it NEVER bind the pin with no alteration of the suspension geometry.

I hate to say this, but Jim Pasha is wrong on this matter. No two ways about it.

Here is the link to the discussion on the racing forum:

https://rennlist.com/forums/racing-and-drivers-education-forum/208351-944-front-springs.html

Serge944

So, in a nutshell, either the springs' range of motion is too large or the balljoints' isn't large enough. Of course this can be alleviated - heavy springs.

In regards to geometry, youre right - I should have used a different term.

Geo

Mostly correct. I have to test some things on my car before I can find the correct answer. The springs could limit the travel, but only if they coilbind and that's not the mostly likely scenario. The length of the stock struts may by the tops contacting the bumpstops before the balljoints bind. If neither of those occur, then yes, the balljoints don't have enough freedom of motion.

FWIW, my plan for my race car is to run VERY stiff front springs (and 32-34mm rear t-bars). I want to limit the suspension movement anyway because of the nasty camber change that occurs with lowered McPherson strut cars.

tifosiman

I agree with Geo. A lowered car is not necessarily bad on the balljoints if it has a higher spring rate to compensate. I have 400lb springs on the front of mine, and it is lowered almost 2 inches lower than the stock height.

When I removed the a-arms two months ago, there was no indication at all of the pin smacking the outside of the alu arm socket. However, my SSI "cup" balljoint upper bushings (brass) were completely shot. They were in shards and the joints had play on both sides, the drivers side being the worst offender. The SSI's only had about a year or so (about 4K miles max) and a season of events on them.

If I wasn't one that checked over my car religiously, I could see where this could lead to a catastophic failure if the pin continued to move around in the socket loose and break out. Thankfully, that didn't happen, the arms were still good, and I rebuilt them with the Rennbay race kits. This is a temporary stop-gap, I am waiting on some charley-type arms from another vendor that use the early 944 replaceable balljoints on the ends.

Did the lowered car cause the balljoint bushings to fail? I don't think so, since there is no evidence of the outside of the socket being impacted with the pin. However, whatever the reason, I really don't care to rebuild the alu a-arms with such frequency and worry about them being damaged from pin play in the socket area. I think the custom arms with the 3-bolt balljoint set-up is the way to go, easier to replace (on the car) and no likelyhood of ruining the arm when they go kaput.

M758

Serge is right to a point. 350/30 on a stripped car is hell on the street. However it MAY not be so bad with full interior and full weight. Reason is the weight will effectively lower the spring rate some.

M758

Geo,
I think the best way to prevent ball joint binding is introduce a solid bump stop that physically prevents the suspension from moving too far. The would put a hard limit and elminate binding for any spring rate or any lowering.

The problem however will be with how much this limits suspension travel. I have steel arms and so no real way to test this, but that will be the limiting factor.

I guess you can test it easly enough by pulling out the coil spring and puting the strut back in. The use a floor jack to compress that wheel and visually watch for bind. Then take some measurements. It would be interesting to see how much up travel is required and on a lowered car like Tifo's how much travel he would had left before it hit this bump stop.

I know on my steel arm car I have it lowered at least as much as Tifo, maybe more. Anyway the result is that I have very limited travel before I close my shock especially with paragon camber plates which move the shock top down maybe 1". I have only 1" to 1.5" of travel before I start hitting the bump stop. In the rear it similar except the trailing arm will contact the frame of the car.

I was concerned about this limited travel, but it seems that with my car's weight and spring rates that this is ok. I have not noticed any non linear spring rates when cornering. I do feel I have bottomed the car a few times, but this was in off track excursions so they don't really count.

Mongo

Hey Joe, I'm gonna keep the interior, but would such a stiff suspension be unforgiving on itself for street driving to? By that I'm meaning destroy itself and the ball joints? Again, i'm not lowering the car more than 1"

Geo

Joe, I agree on all points, although I don't think I'd want just a hard bumpstop. Probably the Koni bumpstops backed up by a hard one at whatever length necessary.

I plan to do exactly what you said with my car. In fact, once the engine is out I plan to drill and drain the strut so I can have free suspension movement to do so.

Normally when you lower a car you want shortened dampers and or to raise the strut mounting (differnet types of CC plates) to get back suspension travel. It may very well be with the 944 that attempts to gain back suspension travel is not recommended (don't know yet, so this is nothing but speculation at this time). In your specific case, it may turn out that the Paragon CC plates are absolutely find because they prevent balljoint bind (again don't know the real answer, just speculating). It would be funny if everyone is buying expensive CC plates to gain suspension travel that only promote balljoint bind, eh?

I may have a solution for the steel arm cars that would have other advantages, but I'll keep it under my hat since I may want to turn it into a product.

Now you've got me thinking.... I've been designing my own CC plates to gain back suspension travel (I have other requirements that current offerings don't meet), but now my curiosity is really piqued. I may want to try all this out before spending any more time and money designing plates when the Paragon plates may be all that is necessary due to the balljoint binding issue.

The only thing holding me back is I want to get the engine out of the car before I start ripping out the suspension and we don't have the shop air conditioned yet. Given it's nearly 100* here with humidity in the 90s, I'm not in a big hurry to spend a LOT of time in the shop if you know what I mean.

M758

I don't know.... my car is track only and light weight so I have no basis for comparison. Most spec cars a light so they are not good comparison.

Chipster

I recently made the jump into a full coil-over set-up. I can tell you the t-bars will have to be re-indexed - unless you like the hot-rod look. I went with the rear coil-overs simply due to the ease of adjustability. It makes corner-balancing the car much easier and changing-out the rear springs is a breeze. Although, I do like the "set-it and go" option, I just know that I will at some point (sooner rather than later later) want to change the set-up and swapping/indexing t-bars to go stiffer or softer is a big operation.

Since I don't have a vast experience with set-ups on these cars, I did some research and took a stab at what I think will work for me and what I intend to use the car for. I can't say I have it right yet and after I ran my first club race with the new set-up I immediately ordered stiffer springs for the rear. But, if these don't feel right, I know I can easily change them. I believe that going this route will actually save money (and time) in the long run.

Just my 2 cents.

Chip

Geo

From experience with the SE-R and the G20, I would say the ciritical factor in comfort with stiff suspension is going to lay with the dampers. If the dampers are too soft the car will be bouncy and jiggly. If the dampers are too hard the car will feel like it has no suspension. Unfortunately I don't have a recommendation for the 944, but I know a lot of SE-R guys with 300+ lb springs on the street that ride quite well because the dampers work well with them.

M758

Cool Geo...

Let me know what you find out.

I got the pargon plates since they were cheaper, but later noticed the reduced travel. Figured it was a bad idea, but given that seem to be workign fine... They may be ok after all. The interesting thing is noticed the rear of the car as limits suspension travel.


Solution for the steel arm cars? What is the problem? I know they are supposed to be bit flexible, but I don't see other problems.

PS any advice you are willing to give out is apperciated by us 944-spec guys. We had a number of Aluminum arm cars as well as steel arm cars and any low cost solution or information to improve reliablility is apperciated.

Mongo

I dont' really care about the ride since it's already stiff and jittery already with just 220 lbs springs and M030 sways. Also the KYBs don't do it any justice since they are fairly stiff shocks.

Serge944

Stiffer spring rate than you already have will only make your car handles worse on the street but a marginal improvement on the track. You think its worth having a worthless car on the street, one that you daily drive at that, to get a little benefit on the 2 hours a month you spend on the track?

That's the problem with a macpherson set-up, there is no middle ground.

Get R-compound tires and play around with the alignment. Once you have an even tire temperature through the turns, your car will be near the peak of ultimate grip.