333pg333

Has anyone done any real research into B/steer on our cars? There are kits out there to buy but I've not read of anyone whose fitted one nor about the downsides of B/steer in our cars. I have heard that not all B/steer is necessarily bad, but I believe that our cars do suffer the bad type.

Anyone with any real evidence? Failing that, opinion and conjecture is also welcome.

JohnKoaWood

Lowering DOES induce bad bumpsteer... I have experienced this on both my cars, to teh extent that I raised the ride height on my NA to eliminate / minimize it.

I have a bumpsteer "kit" from one of the V8 swap vendors that while I am underwhelmed with teh kit, will likely be fitting to my 951, as I like her LOW... just dont like the hunt and peck of the front end whenever there is variation in the road surface!

Dubai944

You do need to get the tie rods parallel with the control arms to minimise toe changes with bump. Particularly with longer control arm pins on a very lowered car, it does make a difference.

I have the elephant racing bump steer "kit". Fancy name for a couple of spacers to drop the tie rods. After fitting them I did notice an immediate improvement. The car tracked straighter under brakes and the steering didn't move around over bumps and undulations as much.

I then had a chance to discuss bump steer with Robi from Robispec Race Suspensions, the US Evo suspension guy, when he was out in Dubai a few years ago. He borrowed my scales to setup a group of Dubai race cars and I had the chance for him take a look at my setup. One thing he showed me how to do was a bumpsteer trace using laser string against the rims to scribe a vertical line on the wall in front of the car with it on a hoist. By marking some tape on the wall then bumping the car up and down through the suspension travel range you could see how much toe change was taking place simply by watching the line move left and right of the static ride height position. With the ER kit already on it wasn't too bad, but based on the trace we added an additional couple of washers under the ER spacers to move the tie rods even further and improved it to the point where the line basically doesn't move at all until you get to the ends of the travel range, which isn't where the suspension operates on the track much anyway with my spring rates. So now it has nearly 0 toe change in bump.

It definately made a further subtle difference to how the car feels. It really stays exactly where it's pointed most of the time regardless of front to rear pitching, roll rate or bumpy track sections.

Bumpsteer is one of those fine tuning things that can make the difference between a good and a great setup. Definately worth spending time on.

333pg333

Pretty sure I have the same kit as John has. Based on Steve's experience I think I need to try this. Good replies. Keep 'em coming. Pics are welcome.

JohnKoaWood

If it looks like a heim joint tack welded to a sleeve with bubble gum, and didnt come with the spacers shown with the really nice looking ones on his website then I would say yes you do...

ausgeflippt951

We're saying the same thing, but to offer a bit more clarification for peoples' benefit, it's specifically making sure the tie rods effectively have the exact same dynamic trajectory of the lower control arm throughout the suspension's range of motion. This just means making sure the tie rods are at the same angle as the control arm at all times throughout the travel.

LUCKY DAVE

As others have said, reducing/eliminating bump steer really does improve the chassis composure, it's especially noticeable in a fast lumpy sweeper.
I have done all my setup work with Jae Lee (Mirage International) in San Diego, he is a well known and respected Porsche chassis guy.
Jae is a firm believer in eliminating bump steer on any car he touches. Like Dubai944, I don't have much travel with my spring rates so I have effectively zero bump steer. The car goes exactly where pointed, even with 725 lb springs, 4 degrees negative, zero toe, and 275's on the front.

xschop

I've seen a few aftermarket bump-steer drop-pins shear off from the MFR. using
cheap steel. The only way to do an adjustable bump-steer on the 944/951/968 is to drill and REAM the spindle knuckle for a 5/8" Chromoly pin.

ausgeflippt951

Anyone got a picture of this bumpsteer kit?

JohnKoaWood

I have other part pictures to take this evening, so I can snap one of the bits I have...

I really LIKE the elephant racing setup, and will likely scrap what I have and buy this:


As seen on another forum:


will post pics of what I have later...

xschop

That double-over design will flex in the taper.

zeusrotty

X don't you have a bump steer kit? I thought I remembered you doing one. If not, maybe you should come up with something and put me on that list... Just need it before May 1st...

xschop

I designed the one above (adjustable) and one that I use for my modded X-member for the V-8 swap (Non-adjustable) 0.75" drop.

zeusrotty

I would probably need an adjustable one. I don't see pics of your anywhere.

xschop

The 2nd pic that JKW posted. You have to drill and REAM your spindle knucke 5/8" and machine the pin from Chromoly.... 4340