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For several years, I have searched for a cost-effective solution for correcting the front suspension geometry of the 944 when lowered to the level typical for track use. As many of you know, one of the main downsides of the MacPherson strut design is its lack of camber gain of the outside wheel with body roll while cornering. This problem is exacerbated when the suspension is lowered, as this effectively lowers the front roll center, and the control arms act as levers and actually increase body roll. The problem is illustrated below, as shown in this "before" shot of my front suspension:
Notice the severe upward angle of the right front control arm from the subframe to the ball joint. This is with the front lowered not quite 2" from stock. Over 6 years of tracking my '86 951, I never liked the way the car felt, and even with stiffer springs and bigger sway bars, there is too much body roll at almost any ride height. Once the suspension would take a "set," it would grip well and the balance was very good, however. But, I have always felt the 944 chassis should be more nimble.
Of course there are the excellent-looking geometry-correcting control arms from Racer's Edge. These are definitely proven, but they are very pricey. Furthermore, I do not feel that we need quite such a beefy control arm for our cars. In the event of an impact, they might be too strong and shift the brunt of the load to something more critical. Or even if not, now you have a very expensive bent control arm to replace! I also do not like the fact that the elongated ball joint pins rely on the factory pinch bolt for retention, but more on that later.
Because I have an '86 with early offset, I switched to early steel control arms a few years ago and have not looked back. The factory aluminum arms are scary and can fail from fatigue from track use, but the steel arms have been proven in years of Spec 944 racing. I have the same amount of front tire as a Spec car, so I do not feel that they would ever bend during "normal" track use (and they haven't in almost 3 seasons of track use and daily driving, with a big Tarett front sway bar twisting them the whole time). Besides, these arms can easily be reinforced if necessary. Furthermore, the steel arm will deform and bend in the event of an impact, which is desirable because this helps absorb the load and prevent it from transferring to something far more expensive and difficult to replace such as the body/subframe or spindle/balljoint.
I feel that this was proven a couple years ago when I stupidly dropped my right front wheel off a curb at Streets of Willow while braking and turning heavily for a chicane section. It was a hefty impact, and I could tell that I bent something, but I was able to limp back to the pits and replace the bent control arm between sessions, and even had time to instruct my student before I went out next. I discussed this in the thread linked below, and some of you laughed at me, but I remain convinced that the steel arms are a good solution: https://rennlist.com/forums/944-turb...ical-fuse.html
Anyway, over a year ago I came across ball joint extenders for MKI/MKII water cooled VWs that are slammed for that "stanced" look that seems to be all the rage these days. The main goal on those chassis is to combat the crazy bump steer that results when they are lowered (they have different tie rod to control arm geometry than the 944; I have never experienced bump steer in my car as the tie rods and control arms stay relatively parallel when lowered). Of course such a device is barely road-worthy, let alone track ready, but as the same ball joint bolts to the early 944 front control arm, I searched further and found this: http://scch-heads.com/viewpart.php?id=47
I contacted Jarod at SCCH and ordered a set. It took awhile as he is a one man band was out of stock, so I had to wait for him to make his next batch. He has a very good reputation in the VW world, and has been making this kit for MKI and MKII chassis VWs for over 8 years now, and they are on dozens of race cars with no reported failures or issues. The pins are made of 1018 steel, which surprised me at first as I was expecting some sort of uber-chromemoly, but Jarod said that they are plenty strong and will bend before they break. I ran this by a friend of mine who designs and manufactures aircraft and trophy truck parts out of many different alloys, and he agreed that I should be OK. I will be having them magna fluxed every few events to be sure they are OK.
Besides the fact that the spherical joint bolts up to my early control arms, I like the beefy tapered design of the pins, and they are TIG welded to the spindle after being torqued to spec with ARP hardware:
Here is a shot of everything installed to illustrate the change. Some form of bump steer correction is necessary, so I used a Weltmeister kit for early 911s that we had laying around the shop. I will likely use something more substantial, like the Elephant or Tarett kit for track use. It is also wise to use a shorter strut, which I have in the from of Ground Control's double adjustables:
Finally, here is the "after" shot showing that the front control arms are much closer to parallel with the ground. I have not measured bump steer yet, but I will soon with my shop's fancy ART laser bump steer gauge and will post pics and results here:
I have only driven the car a few times on street, but the improvement in turn-in and front end grip are phenomenal; this is how this chassis is supposed to handle! What's even more remarkable is this is despite the fact that I am currently running about 1.25 degrees less negative camber than usual! The GC struts do not have an elongated upper mounting hole for camber adjustment, and I figured I'd be able to get enough adjustment out of the GC top-mount camber plates that I have. Sadly, I could only get -1.4 degrees, so I will remove the struts and elongate the upper mounting holes before I hit the track.
I will post impressions/results from track events and auto-X events in the next couple months, and hopefully the pins will take the abuse!
Thanks guys, I hope it holds up to my curb-hopping antics on track!
I had the parts in hand when I saw pics of a similar setup on Disasterman's beast of a race car here: https://rennlist.com/forums/944-turb...l#post11559260
It was great validation to see a real race car using a similar setup. Those gussets look like a great idea and I may shamelessly copy them for version 2.0!
Also, I don't think I made it clear in the first post that I upgraded to the beefier '87+ spindles at the same time, as I have seen '86 spindles break at the track. This may also explain why I can't get enough negative camber with the early offset control arms. Some love with a die grinder should cure that, however.
Subscribed and paying attention. I'm still on the AL arms and early spindles. 87+ spindles with camber plates are something I plan to do IF I don't go full late offset.
OK, I finally made it to the track to try out my setup, and it works as predicted. I ran a few sessions at Streets of Willow Springs, which is a tight, technical course (my stock hp/weight 951 on just cracks 100 MPH on the front and back straights) that track is a great test of a car's front end.
I am running 450# springs (versus 400 before), and the same alignment settings as before (~-3 degrees camber in front, zero toe, 3.5 degrees caster). The front end is now rock solid and sucks in towards the apex with authority; previously, I had to wait for it to take a set. It was very fun to reel in faster cars in the tight slalom-like sections of the track.
Unfortunately, the rear end is a half-step behind, also as predicted. The rear simply rolls too much, and I have to wait for it to take a set. It is still relatively stable and predictable, but it isn't optimal. Ultimately I will go to a Kokeln-like rear end to correct the geometry, but until then I will band-aid it with stiffer springs. I currently have 650# springs in the in the rear with the inverted Ground Control coilovers. I will likely go to 750# rear, and 500 in front to keep things balanced.
A couple of weeks ago I punished the car on a 1,000 mile road rally (the Targa California) which featured a wonderful variety of fun and twisty roads, and the car took it in stride. A visual inspection shows that the drop pins and welds are perfectly intact, and I plan to pull the spindles after the next track event and have them magnafluxed just to be on the safe side.
I did similar thing, though with a bit different method. Made the control arm as low as wheel diameter allows and then modelled the necessary position of the steering ball joint for least amount of bump-steer in SusProg.
Nice! Thanks for the details about spring rates and other specifics.
How low is your car?
The front is just over 1.5" lower than stock in front, and close to 1.25" lower in the rear. Which does not sound like much, but it is. My advice to those who run coilovers but are not prepared to do such a modification is to not lower the car too much, no more than 3/4" or so, or you will run into geometry problems and negate much of the gain from lowering the center of gravity.
Originally Posted by Raceboy
I did similar thing, though with a bit different method. Made the control arm as low as wheel diameter allows and then modelled the necessary position of the steering ball joint for least amount of bump-steer in SusProg.
As mentioned in the first post of this thread, I found similar ball joint spacers for MKI/MKII Golfs, etc online. These are more meant for show cars, and I would not consider them the least bit track-worthy, let alone roadworthy. You are increasing the amount of leverage on the stock ball joint pin, and adding another questionable pinch-bolt connection to the existing one.
However, your bump steer tie rod ends look great. I have the off-the-shelf Weltmeister kit for the 911 installed, and it is not the best one out there. That will change soon.
Bumping this thread to add a cool pic. There was a 991 GT3 at the shop this week and the thing I was most impressed with was the location of the front balljoint assembly. Naturally I thought of this thread since you're moving the balljoint into nearly the same location. Enjoy the pic!
That's a nice setup. When I showed my set up I had people telling me that the 944 doesn't have steering issues when it was lowered. I was wondering if they have ever lowered their own car. Anyways good stuff. Here is a photo of mine.
That's a nice setup. When I showed my set up I had people telling me that the 944 doesn't have steering issues when it was lowered. I was wondering if they have ever lowered their own car. Anyways good stuff. Here is a photo of mine.
Once again, if the front end of a 944 is simply lowered WITHOUT altering the control arm geometry, they do NOT exhibit much bump steer. Look at the first pic of the first post, the control arms stay relatively parallel with the tie rods when lowered. I never had bump steer issues with this configuration, even on very bumpy roads/tracks.
Other chassis have bump steer issues; the early 911 ('65-89) will bump steer like crazy if the front end is lowered more than an inch or so. This is because the 911's steering rack to control arm placement is different than that of the 944.
The impetus for the subject of this thread was to correctly the front suspension geometry by lowering the front roll center with the ball joint pins. This reduces front roll and increases camber gain. It now handles properly.
The bump steer tie rods are necessary to bring the tie rods back to parallel with the control arms. If one were to alter the front control arm geometry WITHOUT the extended tie rods, there would be massive bump steer.
Just got back from Rennsport Reunion V a couple of days ago (if you weren't there, you missed out!), and had a great trip in the 951.
I drove up to Buttonwillow Raceway on Wednesday morning before the event to meet up with R Gruppe (the early Porsche 911 hot rod group) for a fun track day. Spent the day hopping curbs and running circles around early 911 hot rods, and the handling was great.
On the way up to Monterey, I decided to drive the full length of Carmel Valley Rd, which is a gnarly little road that is very bumpy and has a number of hidden cattle guards/grates. I accidentally hit a few WAY too hard, but the drop pins held up perfectly. In fact, I inspected the car last night and I didn't bend or break anything after lots of track and twisty road driving.
To be safe, I will soon pull the spindles and have them magnafluxed, but after the abuse they have been through so far between the Targa California and multiple track events and an autoX, I'd say they are good to go.
Hey Humboldtgrin (or anyone else that may know...)
What are you using in the above pic for bump steer correction? Is that a kit or??? I'm looking for something exactly like that.
Thanks
Jay
12-21-2014, 04:12 PM
My front roll center/bump steer solution
