23/31 t-bars in dual-purpose early 911?

[Jim Richards]

For my dual-purpose 73 911E, it was suggested that I should go to 23mm front / 31 rear torsion bars, and have my Bilstein shocks revalved to match. Supposedly, I would still have a real streetable car while vastly improving it's manners on the track (DE). I'm currently running 21 / 26 t-bars, 16mm front / 15mm rear swaybars (I think), Bilstein HD shocks up front, and Sports in back. Street poly bushings in front, Neatrix in back.

Is this sane?

Thanks!

[jpnovak]

Completely INsane. have fun with Dino.

The larger torsion bars will not make the ride quality suffer as much as heavy sways. Since you have the luxo-boat as a driver I would go for it! Besides the Honda can always step in when you need to feel the need to have a little softer ride.

what happened to that nice 73E? I think you will next start stripping out the interior and adding racing stripes. How does Lu feel about this?

btw, did you get your seats? I will send you some pics of my mounts if/when you need them.

Jamie

[dickster]

jim

i have 22/31's and while i dont mind them - the ride is HARSH on the street.

[Shaun @ Tru6]

I have 22/29s and Sports front and rear with Elephant Racing bushings and 17 inch Cup IIs. The car is used as daily driver + DE and it rides beautifully, handles very well, and is even comfortable... long and short distances.

My 84 is much heavier than your 73, so I'd think about the same set, not heavier.

[chrisp]

I have 22/28 and dual use my car. It's pretty stiff though. The wife won't ride in it but there may be other contributing factors (Dansk dual out, SSI's, race buckets, no A/C, no radio, poly bushings, monoballs)

Although great for the track (excellent club racing set up) I would think 23/31 is really stiff for a dual purpose car with your motor (lighter rear end vs. mine).

If you do try it and don't like it I will work a trade for my 22/28 for your 23/31 if your interested. I am planning on upgrading to 23/31 this winter anyway because it'll be track only next year.

[89911]

IMHO, that setup, especially in your already light car, is going to be very stiff. You will quickly be making the direction of your car being a track only car with its street use only being limited to driving to and from the track and bedding in you track brake pads. I have 22/30 on my car and my brother runs 23/31 on his and just that difference is enough to not want to drive his car, especially on bad roads. His car is great on the track though. It depends on what is more important. Some minds feel that you can't get enough spring rate with torsion bars, even with 23/31's. Others feel that too stiff of a car will make the car even handle worse, hopping over road uneveness rather then absorbing them.

[Jim Richards]

Thanks guys. One key question that I still have is whether revalved Bilsteins would make this work for street use. Any thoughts on this?

chrisp, I haven't purchased them (but I have a lead on a set) and might want to look into your offer.

Jamie, LOL man!!! Dino (aka the purple car) isn't a going to be a full-on track car; however, I am putting the new seats, harnesses and rollbar in before VIR (Sept 10-12). I'll save my factory sport seats, just in case. After all, they go well with my Coco-mats. Oh yeah, the S rocker trim goes back on when the DE season ends. BTW, the 993 lux cruiser may be on the bubble...we'll see. And don't get me started on the Honduh.

[chrisp]

OK. email me at chrispetron@yahoo.com if you would like.

[Noel]

I agree with 89911. That seems a bit stiff for such a light car.

On the question of re-valving, my shocks have been revalved to match the torsion bars and it is the way to go, IMO. The ride is very firm, but not harsh. It is the excess compression in shocks will make you feel every bump. When the shocks are custom revalved, the consensus is to use less compression and more rebound. The theory is to let the torsion bars absorb the initial shock of the bumps and the excess rebound to merely control the oscillation caused by the larger torsion bars. My car with the larger torsion bars/revalved shocks rides better than when I had the stock Bilsteins with the stock bars.

If you already have Bilsteins, simply send them into the factory for rebulding/revavling ~$65 ea.

[gumba]

I have a set of Bilstien revalved shocks, F30 setting (by Smart Racing) for sale. We used these on our '73 street/track car. On the track it's a great improvement. On the street they are taught, but not alot more than the Bilstien sport shocks. I turned the car back into a street car and put the Bilstien sport shocks back on.
The 23/31 bars are (in my opinion) too stiff. I would stay around 22/28. I run 22/30 on our '73 Targa w3.2 and feel it's too stiff.

[Schrup]

Jim, I have 22/29s, Carrera sways & Bilsteins sports that I sent back to the factory for revalving. I had my shocks valved for a 2500lb car & to match my torsion bars. At this point I'm glad I didn't go any bigger, the car feels flat, but doesn't skip over bumps too bad when cornering hard.

If you have you shocks custom valved for a certain torsion bar size, then go with smaller bars later, you may not like the results. IMHO, I would make a decision & stick with it unless you are going to pony up the money to revalve again.

[Chuck Moreland]

Your car is light. 23/31 is too much for the street.

Your existing setup is actually pretty good for a dual use car. If you really want to stiffen it up, go to 21/27 or 22/28 max.

The custom valved shocks will actually make the bigger difference. You'll love them on the track, but they ride harsh on the street.

[Noel]

Originally posted by Chuck Moreland
You'll love them on the track, but they ride harsh on the street.

Chuck, my experience is that they are better on the street because there is less compression and more rebound. Here are some numbers from a rear shock as an example.

Here's the Rear shock specs according to Bilstein:

Rebound / Compression

HD 194 / 150
Sport 311 / 160
My Revalve 360 / 140

The ride is firmer (Due to the bars) but less harsh due to the reduction in compression. The revalved values were recommended by Bilstein and I assume that they use the same values as Smart Racing, as I heard that Smart Racing merely sends the shocks to Bilstein and marks the price WAY up.

[Superman]

The more I learn, the more I understand that there is no such thing as a combination street/track setup. They're just not the same thing at all. Sure, I want to have maximum performance from my mostly-street SC, and yeah I've considered stiffer Tbars, but each step is a compromise somewhere. Some advice I trust suggests focusing on shock health and bushings more than Tbars. Our roads here leave something to be desired, and it would be easy to create a "street" car that leans very little in the turns on the track, but is airborne half the time on the freeway.

[skinnerd]

I have the 23/31 setup in my auto-x car, and it is really harsh around town. I still have stock Sport Bilsteins, so am looking to revalve them or even go the adj. Fox way for improving both ride and performance.

My other car has 21/27 with stock Sport Bilsteins, and it has a firm but very comfortable ride. And actually it is a much better ride than stock. Very confindence inspiring. Stock is way too mushy for me, but I drive 2 mod'd early 911's and a Powerstroke 4x4, so I like a stiffer ride.

Both are light cars. So if you go the way of 23/31, make sure you get revalved shocks at least.... otherwise your luv for the car may dwindle.

Must my 2cents....
Good luck.

[ted]

I agree with Chuck that 23/32 is too stiff for the street.
But how much street driving do you plan to do?
That combo in race car terms is still a compromise. Many 911 track cars will run much stiffer coil over springs.

I have a similar (21/30, revalved shocks, big sway bars) set up on my 2400lb street/track 911.
On some freeway sections it does get a bad chop to it. Typically if I take it for weekend trip, over a couple hundred miles there might be one 10 mile stretch on the freeway that tries to shake my brains loose.
Your wife is not gonna like, but it's not your only car?

With the firmer set up you will want to use R rated tires. If you do not plan to use R rated tires I would keep your current combo.

The stiffer combo would be better for higher speed tracks with good traction. For example if your DE events are held in a big dusty parking lot with mostly 2nd and 3rd gear turns then the softer current set up would be good enough.

I'd rather have a little chop on the freeway than a soft car at a DE in a 120 mph sweeper. If you stay with the soft settings remind yourself in the middle of the 120mph sweeper as the car dips and rolls how nice it rides on the freeway.

I prefer to compromise the street ride for improved handling and greater confidence at the track.
I say try it. It is reversible and the parts are very saleable.

[Jim Richards]

I little more background...I drive to DE events, anywhere from 1 - 7 hours. The tracks I'm on vary quite a bit (Summit Point, VIR, Watkins Glen, Mid-Ohio). I run R compound tires on the track. This winter the 2.4E is coming out and will be rebuilt into a basic 2.7RS (i.e., no extra cam, CR bump, etc.).

I also run around town and cruise out in the country with this car. I have a set of street tires/wheels for this. My wife also drives the car. She's not a track junkie, but she's not "fragile" either.

From the feedback I'm getting, it sounds like I'd be wise to limit myself to 22/28, possibly with revalved shocks. I'm hoping that's a good upgrade from my current 21/26 set-up and will keep me happy for years to come.

[ted]

If you were in the area I'd let you drive my car around town and judge for yourself. I also tow my car to the track, so I don't suffer the firmer stttings enroute.
With regards to the amount of street driving you do I'd keep it a little soft too. I like the 21/30 combo, maybe a 21/28 combo would keep the front from getting too stiff on the street too?

[Jim Richards]

Originally posted by ted
If you stay with the soft settings remind yourself in the middle of the 120mph sweeper as the car dips and rolls how nice it rides on the freeway.

This is a quote to remember!

[chrisp]

I think the 21 is right when combining with something softer than a 28. If you go stiff in therear then run the 22's.

My car with 28's in the back is not nearly stiff enough for the track. 911's suffer from a lack of rear roll stifness. That's why the factory went to coils.....so they could get higher spring rates in the rear. Also with the advent of better tires in recent years we've seen the club racers going up to 31mm. 28 or 29 used to be good but with so much stick in the back now, spring rates are going up.

With the set up you have (r tires) you'll be asking for more in back on the track. I was given this same advice and didn't heed it. I should have gone with 30 or 31 to start. I have a 3.0 so that's a bit of extra weight in the back compared to yours. Not sure how it compares to the weight of the 2.7 you are doing.

Have fun with it.