How low without bump steer?
 

Hi,
I just completed my ER suspension upgrade and I was wondering how low I should go without a bump steer kit. I tried searching but most information is for a 911 and not a 930. Given that there is no room to fit the rack spacers on a 930, I suspect that the suspension is different.
The car will still be used on the street a bit but I want to set it up for DE events.
Here is what I did to the suspension and I will be getting an alignment and corner balance this week so any input on height, weight ratio and alignment is welcomed.
-front and rear poly bronze bushings and monoballs
-bilstein sport shocks
-sway a way torsion bars (23mm fr and 31mm rr)
-new ball-joints and sway bars bushings and links
Thanks
David

If you can't move the rack, you can always space the outer pivot point (tie rod end) to match the rack.

I was thinking about that one... I guess the tie rods have to be horizontal right?

ELEPHANT RACING Adjustable Bump Steer Kits for Porsche 911/912/930

http://www.ebay.com/itm/Rebel-RSR-Products-Race-Adj-Bump-Steer-Kit-911-930-914-/190640556324?hash=item2c63100924&item=190640556324 &pt=Motors_Car_Truck_Parts_Accessories&vxp=mtr

Thanks Merlin,
I was looking at them but I did not really want to have to remove my struts again and send them out...
Anybody has experience with those that are bolt on? I don't want to go excessively low so the max 19mm or adjustment would be enough. Do they induce flex in the spindle arm where they bolt?
Thanks of your inputs!
David

Unless you are dropping a ton, I don't think you will have an issue with BS. How low are you planning on going? Remember these cars came to the America's higher than the Euro ride height, so I would assume bringing them back down to that height would keep the BS correct once you reset toe.

Hi David,
With the Rebel Racing kit the weld on brackets are optional. I have a kit, but haven't installed yet. I wasn't going to weld brackets. Mine is not that low, about 25 1/4" to fender lip. But I do feel some bump steer. Where were you going to get your aliment done?
jack

Mine is a euro 930 1985. I went down to 25in front and 24.5 rear. I looked and the tie rods are a going a bit upward so I was worried. I didn't wnt to send it to alignment and then have to change the tie rod ends...
Thanks!

Hi,

You got me curious about my ride height. 25 1/4 rear and 25 front. PO used car for a few events each year and a little street. The records show he spent $$$$ to get car setup at professional shop. I don't know much about setting these cars up myself but should rear be lower then front?

The rear is probably not lower than the front. If you are measuring to the top of the wheel wells, the are not the same height w/respect to the body front and rear. Measure from the bottom of the rocker panels to get a more accurate measurement. Good luck.


Tom

Hey there,
My car is stupid low, I run the Rebel Racing bump steer kit, that does not have the weld on support brace, straight bolt on kit.

Yes you do need to properly adjust your toe setting.

I run with ALL the spacers for maximum tie-rod angle correction. Been running it for 3 years now, great product,

Mark

Hi Jack, the alignment and corner balance are hard ones, not much choice in Victoria, do you have suggestions? I don't mind driving out of town, it drives pretty good already but it is probably eating tires right now as I have maxed out camber and toe-in in the back.
David

Silly Question. What the idea position we are trying to move the Tie Rod in conjunction with the steering rack by installing Bump Steer? 100% in line? I just went out to measured My 85 Euro 930. The Front is 25 ins and the rear is 24 ins. Can't tell the position of the tie Rod to the steering rack..

I'm pretty sure that you want the tie rods to be parallel to the lower arm (with car on ground not on jacks).

Reading more about it, it seems like it might be more complicated than just lining up the rods with the rack or parallel to the a-arms... I don't think that parallel to the a-arms is what we want as without bump steer kit, no matter the height, I don't think that they are parallel even at normal euro height (I might be wrong here...) but if the rods point upwards and the a-arms point downward, when the car hits a bump, the bottom of the wheel will be pushed out a bit at first while the rod will pull in immediately so it will create toe out (if I understand that correctly.)
I will take a look at how the rod is when the car is at the official euro height which is measured by center of wheel difference with center of a-arm I think (I will look in the factory service manuals for the 930 for this) and see what the position of both is at that point and try to come up with an answer of what the best option will be...
For ride height, the actual car will have a rake angle of roughly 1 degree towards the front but the fender height is higher in the front due to the way the fenders are designed. So the front is still lower than the rear.
I don't feel much bump steer right now but I haven't been at the track yet... not for another 3 weeks so I have a bit of time to set it up properly.

Hey David,
I don't know of any one on the Island to do corner balance & alignment but if I hear of someone, I'll let you know.

Thanks TDIdog,
Do you guys run toe out in front?
I was proposed these alignment specs, any input?
Front
2 deg camber (or max camber if unable to go to 2)
0 toe
6 deg caster
Rear
2.5 deg camber (or 0.5 to 1 deg more than front depending on who I ask)
15' toe in
Any inputs?
Thanks
David

I run fractional toe in at front - my guy says it is better to have slight toe - I have about 3 mm total. The idea is to have a slight pre load - to stop any float. My camber is 1.7 front (I had to install ofset mono balls for that) and I have the spacers fitted under the front X member.
I am running 2.7 camber in rear with 5-6 mm toe in. this is for my track machine. It is 'quite ' low in front - but no bump steer.
Alan

I have a euro dropped to the limit of the adjuster and drive the crap out of it on twisty back road with no bump steer. Maybe I'm a bit strange, but I actually like the 'active' feel of bump steer. I'm NOT chasing 1/10ths on a track just use the car as a sunday adrenaline pump so take my comments with a pinch.

Post your question on the autocross and racing forum to get more input. These guys would chime in more since your leaning towards a track set up....just my advice.
I run 2 degrees negative camber on my fronts and still wish I could get more. It seems that the track tires want more than that to reduce the understeer. I do alot of DE and track days with my 79 930.
I know Grand Am spec racers are running 5 degrees front camber on the GT series machines.