RS Repro Suggestions?

[Gordo]

Hello,

Firstly, as a "new guy" I would like to thank everyone on this board for being a source of amazing technical insight.

I am dusting off a 1970 911 T / RS repro that I sadly don't have time to enjoy as much as I should do to work. The Brilliant team at Black Forest went through the existing motor (2.7/Webers/webcam..) and are now doing the suspension. I was looking for anything I might have missed that I should do now to be cost effective. Intended use is 20% street 80% Autocross/DE/TT. Mods as Follows:

21/27 Tbars
Poly Street Compound bushings
SC adjustable spring plates
Koni Sport adjustables
New Front Struts (getting rid of 3" bolt spacing)
84 on front wide A calipers
Steel DOT brake lines
Turbo tie rods
OG racing cool brake kit w air deflector
bearings and ball joints
lower align and corner balance

Still debating alignment specs but leaning towards 0 deg front and 1 deg negative rear. Car is running 16 6s and 7s 205 and 225s and has a welded in Autopower cage tying to front and rear suspension. PCA class is unimportant as I am not that good and play strictly for fun.

By the way, having seen Kurtstarnes beast all I can say is


Thanks again!

[Joeaksa]

Jim,

The one thing I can see that is missing is MY NAME on the title!

Sure cant wait to see the pics when its done.

JoeA

[Jack Olsen]

If it's only going to see occasional time on public roads, I'd go with more aggressive torsion bars, and quite a bit more negative camber (at least a full degree more than the settings you're talking about). Since you're lowering it, I'd also strongly recommend the tie rod drop links to correct steering geometry. (If you're lowering the car 1 1/2 inched, a half-inch washer on a bump steer kit is not enough.)

Also, you don't mention swaybars. Adjustable bars can allow you to dial in real performance gains on the track, and back things off for street driving. Smart Racing and TRG make good swaybars. Weltmeister makes okay ones.

The steering geometry and alignment settings make a very big difference on the track -- more than horsepower mods, in my opinion. The only place you're maxing out the benefits of power is when you're going in a straight line. Sweepers and other turns are all about how you set up your suspension, and they're a much bigger part of most tracks.

[Gordo]

Jack,

Sorry did not mention the sway bars. The car already has 22mm front and rear weltmiesters. I know they are far from optimal but they were already there and work. Perhaps for next round of modifications. As for bump steer the current plan is to space the rack as you mentioned and not lower the car excessively. Do you think this will be sufficient? Again your suggestion is a good one just a matter of time and money. On the alignment you are suggesting -1 front and -2 rear which sounds pretty aggressive but if it works on yours (beautiful car btw) it is probably a good setting for mine. I am lighter in the rear having the 2.7 v the BIG motor hence the 27mm bars and not larger. Also do not want to put the car on too much of a razors edge as my driving skills are far outclassed by the cars abilities (leaning towards a "soft" track setup to make the car somewhat forgiving on track).

Best,

[Jack Olsen]

21/27 isn't a bad start. I was running 19/26 on my car for a while, which was probably a good way to learn. But I'd disagree, ultimately, about not going with more than 27 in back. I have 30mm bars in back, now, and wish that I'd gone even larger.

I also have the Weltmeisters. The difference between them and the better bars is a pretty fine point. But if I were starting over, I'd get a set with more durable hardware.

I think the rule of thumb is to run 1/2 a degree more in the rear than the front. My camber settings are more extreme than I suggested for you. We've recently managed to get about 3 degrees in the back, and about 2 1/2 in front. We had to modify the upper strut mounts to get what we wanted in front, and do a lot of trial and error to get that much out of the backs.

For the recent Open Track Challenge, we were running 2 1/4 rear 1 3/4 front, and we were still going through the outside shoulder of the tires faster than I'd like.

[Gordo]

Jack,

I am amazed with that much negative camber your guys were rolling the tires onto the outside shoulder. You must have been pulling some serious lateral G's. Iam seriously jealous of your toy (as are most on this board) As for the bigger rear bars, I will remeber your advise and go to 30 plus after I get comfortable (enough seat time) with the new setup. Sounds like -1.5 and -2.0 might be a good initial start for mine. The cars biggest weakness was brakes. At Holtville earlier this year (pre modifications) I was playing with some SCCA Spec 7 friends and doing fairly well for my feeble skills turning 1:18s with the chicane in the back straight. A winning competition time for the Spec 7 guys is mid 1:16s with no chicane and they are good drivers. Then this Heavily modified RS America shows up and teaches me what fast is.

Me to my passenger - "lets see if we can hold him off for a while"

RSA - Zigging between my mirrors

ME - "guess not" and wave him by on back straight.

I stay with him somewhat till front straight where he starts to get small. He then goes real deep into turn 1 before braking.

ME - I can match his line and brake point I'm alot lighter.

ME - @#%$# @$% AS I can't get slowed down pedal fades and fortunately am able to bail out the runoff under some control but very humbled.

Needless to say I was very impressed with the RSA whose owner was kind enough to give me a ride later. All I have to say is Big Reds are awesome.

Best,

[Jack Olsen]

Hmm. Brake fade shouldn't start until you've run the brakes through a long series of hard laps. If yours are showing fade in situations where there's not repeated hard braking (and by that I mean like after eight or ten hard laps), then there might be an actual problem with your brakes. Even stock M brakes on a 73 should be fine for a handful of hard laps. You might have glazed your pads or rotors, or even have bad master cylinder or a leak somewhere in the system.

But if you're two seconds off the fast guys, then you're doing pretty well. I'm thrilled to run a 1:35 at Willow Springs, out here, but the 911's in the Tribute to Le Mans can run 1:19's for six hours in a row.

[Gordo]

I had in fact been out for several laps before I tried to chase the RSA and this was second session of the morning with about 15min in between. Dave Turner Motorsports allows guys to come on and off track at will during his "Fun Runs" (with flagman for safety of course). I was not using the brakes real hard playing with the "slower" cars but trying to keep up with a superior car and driver I definately cooked mine due to poor technique and just being outbraked equipment wise. Some glazing and lost about an inch of pedal (Ferodos and Valvoline synthetic fluid). I am told Holtville is notoriously hard on brakes. Master cylinder checks good but I am having black forest go through the system to be sure. Figure the Late Carrera brakes/slotted rotors will be a good solution for mine and not cost prohibitive, Gents at BF agree and were a bit scared of the Boxter brake/bias issues. Gaining some thermal mass and pad area without upsetting bias. BTW which pads do you run, Oranges? The plan for mine is Oranges and ATE blue but I am open to better sugestions. I haven't run Willow in years, hope to fix that problem soon. Can't remember my times but I am sure they were not that quick. Do you ever get down to this neck of the woods? Bet your beast would be pretty d--- quick at Holtville.

Best,

[Jack Olsen]

Black Forest is a real good shop, and should be able to sort out any brake issues. I agree that Carrera fronts are a very sensible upgrade.

I run Porterfields on both street and track, but with a more aggressive compound on the track.

[Randy W]

I agree with all of Jack's comments. 2 degrees front and 2.5 degrees rear (or more) negative camber is what you will end up wanting for an 80% track car. 21/27 is a great combo for your chassis/motor combo, but more of a 50% street/50% track compromise. 22/28 or 22/29 would be better for your purposes IMO. Otherwise, I think you will end up wanting stiffer than 21/27 before too long. Agressive pads like Pagid orange or black and a higher boiling point fluid will help your brake fade problem as well. Sounds like you're on the right track - have fun!

[Gordo]

Randy,

Thanks for the input. Obviously, your opinion and Jack's are quite valuable to me given similar chasis (though mine is not nearly as developped ) and your level of on track experience. I am trying to follow the advise of develloping the car to work together as one big system but at the same time not building something that is "over my head" in terms of being to much car to learn on. Most of the really good drivers I know learned in 914's (A stock) before moving on to more serious hardware. In my case I learned with a fair amount of power and tire and am affraid this "crutch" hurt my learning curve. All the same it has been a FUN car to learn in.

Best,

[aseem]

Have you ever considered a coil over rebuild instead of uprated tbars? AJ has this kit:

I'm planning an '73 RSR replica project and I'm curious about the coil over upgrade....

[Gordo]

Have seen the AJR kits and some other very good ones. My understanding from talking with some fairly smart folks and reading some good info on this site is that unless you are going to seriously reinforce the chassis (my cage is welded to front and rear shock mounts, but they are not reinforced enough) and the car is TRACK ONLY the coil over kits are not all that great an option. Forces generated can tear up unibody!?! Also with an earlier/lighter car T bars should be able to get enough spring rate for all but the most aggressive set ups. Most of the fast early cars I have seen are still running Tbars. Would be nice on a true RSR repro if you did all the required additional mods but a bit overkill IMO. Just my amatuer .02.

Best,

[Gordo]

Good post on RSR coil over use

RSR coil overs for street driving

[aseem]

Thanks for the tip on the coil over thread Gordo