chris walrod

There has been no change in ride height post RS upright install that I could see on the couple of cars I've installed these onto.

jackal2513

Hi bill, I remember you being confused about this in a previous thread.

The 993 RS uprights have a different and shorter geometry on the steering arm that connects to the outer tie rod. For a given rack, the subjective feel of the rack will be QUICKER. It has nothing to do with stops and total turns. A shorter distance from tie rod ball joint to the rotational axis of the wheel means the steering becomes more sensitive and turns more for a given input.

The proof is also in the pudding. My car has RS uprights but a stock C2 rack and the steering quickened up noticeably when I fitted them. Everyone who drives on it immediatlely comments on just how sharp the steering feels compared to their C2, C2S, C4S, Turbo.

Bill Verburg

On the contrary, You my friend are the one that is confused.

Yes, when you swap in a 993 steering rack into an RS it will be faster and especially so when the stiffer RS rubber linksare considered, because the rack itself has a different tooth count, the RS rack has 2.73 turns lock to lock where the 993 rack has 2.47, I did err in the last post in that the #s there are the steering ratios not turns lock to lock(it was late and I was more interested in the football game).

here are the correct turns lock to lock
Both 964 and 993 have power assisted steering, however 964RSA and RS manual racks are available
911 is ~3 turns lock to lock, non assisted
964 is ~2.81 turns lock to lock, assisted
993 & 993GT2EVO is ~2.47 turns lock to lock assisted
993RS 2.73 assisted
964 manual ~2.6


the arm geometry has nothing to do w/ that. The RS outer tie rod has a different shape which compensates for the shoprter wheel carrier arm, only the height of the arm mount has changed not the "distance from tie rod ball joint to the rotational axis of the wheel", which would require a longer or shorter tie rod

stock 993 top, 993RS bottom


RS installed, note the relationship of the tie rod mount to the A arm ball ball joint mount. It is not moved axially from stock

DanQ

As an interested observer, I think a picture might illustrate Jackal's point better. I hate to see two guys I respect on this board disagree when they both have accurate points to make.

The lever arm (red line) of the RS upright "looks to me" to be marginally shorter than the lever arm of the standard upright (Blue line). Given the same movement from the rack on the RS upright would rotate the tire more when the lever arm is shorter. Use your arm and elbow as an example. move your finger tip 4" to the right and notice the amount of rotation around your elbow. Now move the mid point of your fore arm 4" to the right. this time your finger moves ~8"...

Bill has the speed of the relative racks correct, but Jackal is talking about the lever arm length. I don't think the tie rod length is the issue here.
Hope this helps

Bill Verburg

hey don't pay a bit of attention to my opinions
the factory specs speak for themselves

here are the correct turns lock to lock(this is all documented in factory lit.)
Both 964 and 993 have power assisted steering, however 964RSA and RS manual racks are available
911 is ~3 turns lock to lock, non assisted
964 is ~2.81 turns lock to lock, assisted
993 & 993GT2EVO is ~2.47 turns lock to lock assisted
993RS 2.73 assisted
964 manual ~2.6

Actual steering ratios, again factory specs
964 18.48 slowest
993RS 18.25
993 16.48 fastest
given that these are the installed ratios, I'll concede that the delta could be from arm geometry, but that delta is only 0.23 or 1.26% when the 964 ratio as installed in a 964 is compared to the 964 ratio installed in a 993RS

ppressle

I think the question is if the wheel moves the same amount for a fixed movement of the steering wheel. That includes the racks rate and the steering arm end lengths.

For the steering arm part of the question, the point of rotation will be in the tie rod end joint rather than the tapered bore. This angle makes it further from the bore on the RS and further in on the stock. I think you would need to measure an installed set to know.

You need a measure perpendicular to the axis of steering rotation to the pivot point in the tie rod end.

If does look possible that the steering rate is quicker on the rs due to the steering arm though.

Bill Verburg

The wheel carrier steering arm height is what is shortened not it's steering leverage, look at the specs

Bill Verburg

You can debate all day, look at the installed specs

ppressle

I haven't digested what the specs mean. I too had been looking at the pictures and trying to rationalize it.

jackal2513

You've got it.

Let's magnify the proposition to help Bill understand. Imagine if the steering arm was the length of the whole car and you actually sat on the engine and the steering wheel was situated there. If you moved the steering wheel a quarter of a turn THE ACTUAL CARS WHEELS WOULD BARELY TURN. Forget racks, don't get bogged down in racks and rack speed.

This is so patently obvious that its a mystery why I am having to go over it again but when you fit RS uprights to a 993 the steering will feel a fair bit quicker. I know because I've done it rather than guessing what might happen or trying to work it out empirically. I went from standard to RS uprights with no other mods. Again, this is in real life, using my own senses and I consider myself pretty sensitive to all things CAR.

Also, ask any number of 993 owners who have driven my car and IMMEDIATELY noticed the very different steering for further proof, or give Chris Franklin a call at http://www.centergravity.co.uk/ he is the most respected porsche setup guru in the UK. He will agree with what I have just said and in fact he was the very person who warned me that it was going to happen before I installed the uprights. With respect, there aren't many people around on this planet who know more about setting up Porsches than Chris.

Bill Verburg

Bill understands what you are trying to say. Unfortunately you can't read a spec sheet.

Porsche publishes the installed steering specs, that the # of turns lock to lock. This # tells you how fast the steering is.

more turns slower less turns faster

the rack ratio has been included in the turns, it does not further affect anything
slowest to fastest, these are all factory #s
964 is ~2.81 turns lock to lock, assisted
993RS 2.73 assisted (uses the 964 rack and RS uprights & arms)
993 & 993GT2EVO is ~2.47 turns lock to lock assisted(EVO uses the 993 rack and RS uprights & arms)

when you use a 993 rack w/ RS uprights and arms you have the same steering as on '97 993GT2Evo

jackal2513

Bill, I am talking real life. You know, like going outside and actually doing stuff like driving and using the 5 senses that nature gave us ? You can throw all the armchair small print around you want but the fact is when you fit RS uprights onto a stock C2 or C4 the steering becomes quicker because of the steering arms.

Or all you calling me a liar or in some way perceptually impaired ?

trophy

No one is reading Bill's post. The 993 and the 993 gt2 have the same number of turns lock to lock ~2.47 (same quickness). The only difference between these cars is one has the RS/Evo uprights and the other (993) doesn't. Therefore if you change only one thing on the stock 993 and make it like the GT2 (the upright) you end up with exactly the same quickness in the steering.

trophy

What you are feeling is an improvement in directness that comes with the evo uprights and the GT2 tie rods. These GT2 tie rods remove the rubber from the steering system making it 'feel' more direct, not changing the quickness.

Mark in Baltimore

+1. I never felt a change in steering quickness when I put my GT2 uprights on nor when I removed them.