OK. I'm dying here... Here is my current setup:

Front:
21mm torsion bars
19mm AR bar (set full soft) - urethane bushings and steel heim joints
Turbo tie rods
Koni Yellows (1/2 turn off full hard)
Stock rubber bushings
5 degrees caster
2 degrees camber
2mm toe out
1/4" spacer
15" stock steel rims
Used Kuhmo v710 - 25psi hot

Rear:
180lb springs
Koni Yellow set full hard
No rear AR bar
Weltmeister Black urethane bushings
3mm spacer
Slight toe in
15" stock steel rims
Used Kuhmo v710 - 27psi hot

Tire temps tend to be consistent across the face of the tires, with the rears 20 degrees warmer than the fronts.

I hunting for the last bit of grip I can get for autocross. The rear end of the car feels soft to me and seems to chase the front. Turn in is pretty good, but the rear gets a bit confused in slaloms and lacks high speed grip. I also am lacking a bit of stability under braking.

I'm planning on trying to crank up the front sway bar, but that seems a bit counter productive as I've always been taught to run as little bar as possible and use it to make slight tuning adjustments. Maybe I'm there, but my gut tells me I need a lot more rear spring.

Anybody out there running a setup close to this with a ton more rear spring?

You can see videos of the car at http://www.youtube.com/yeahmag

-Aaron

Your setup is similar to a lot of "hot" setups that have been run in the past.We never ran a car with that size torsion bars, so this information could be completely flawed.We have run a lot of combinations in spring rates and various size bars and we currently run an adjustable 22mm and I know the Gullick car is currently running a 23.The front bars in a 914 are a patch for a poor roll center (testing with spring rates and no bars really show this).Your plan to crank up your 19 will help, but in our results, the 22 was better.(When the teeners were still competitive in stock scca classes) all of the top 914s were running 22's-Reitmeir,York,Regenold etc.A ton more rear spring will not be faster-slightly more may be quicker based on personal driving style.Your shocks are single adjustable, rebound only units and your full stiff on the rear seems high.Keep in mind that a half turn off of full stiff in that shock will not be the same next time when you adjust.Just a fact.Shock dynos clearly show this.We played a lot with ride heaight and rake.Hope some of this info helps. J

I have a little front rake, but I'd have to measure it to tell you what it is. I was just trying to shift a little more weight to the front... So maybe just a 200lb spring and crank up the 19mm front AR bar is a good start - along with reviewing my alignment. I may try and get the rest of the rubber out of the front of the car. All that stuff is in such good shape it pains me to do it.

Any suggestions on ride height and alignment? The rear is at the lowest clip on the Koni's and the front is set to a slight rake. What front torsion bar did you run?

We ran stock front torsion bars in our stock and street prepared cars.We used te set our front caster at 5 (like you) and then get as much camber as we could at that setting.In the rear we stayed between 1.75 and 2 degrees of negative camber.We are running less rake in our car than most -everybody has a different measuring point-but try to keep a slght amount of rake under all conditions due to the light front end.Not a fan of delrin bushings.Had failures and strange wear issues.Like elephant racings setup.Ran good rubber bushings a lot of years.Did not like the cheap replacement for bushings.Tested a lot with toe through the years -Never liked any toe of more than an eighth anywhere.

Aaron,saw your post for 300 lb springs-we have 8 inch in that spring rate.We have tested 140,175,180,200,225,300,350, and 400s in the rear of our six.In our testing 300 is too stiff.J By the Way-currently running 200s but have a new set of 175s going back on car.

What are you running for a front torsion bars on that car? An 8" might work... Again, I'm trying to balance the car with a 21mm front torsion bar. I was starting to go for the "shifter kart" approach. Where the springs just hold the car up!

I think I have enough grip in the front to support it, but I was planning on putting my stock torsion bars in to test...

Currently running 400s.Have tested in 50lb increments from 300-700.A lot of the higher numbers were when we were trying to run with no front bar.J

My 914 wasn't all that much more different from your car Aaron other than the power band and I was pretty happy with the stock front t-bar, 200lb rear with a 22mm front bar near full stiff. I had poly bronze rear bushings so if you are staying with the plastic bushings I would think 175lb rears would be about right if you are going to go back to the stock front t-bars. If I could have, I would have loved to run the 19mm front t-bars out of a 911 but there is just too many parts to change to make that worth the effort.

My feeling on the front bar is that it helps transition speed better than a stiffer spring rate and as long as you are keeping the inside wheel close to the ground, you are ok.

I'm confused... So with your -6 your currently running 400lb rears with what torsions bars?

I think he is saying that they are coil over front. The front coilovers I picked up to try with my 935 front suspension are 225lb which is pretty close to the same wheel rate as a 21mm front T-bar.

Evan,

I'm totally tempted to put the stock torsion bars back in as there is a Speed Ventures event on 1/15-16 at Cal Speedway that I could use to try the setup. *BUT* I do have an unused set of coil overs that I could sleeve for Koni's (I think they are for Bilsteins as they are too big ID for the Koni's) and then start to mess with higher spring rates.

Seeing as I'm broke as a joke the putting the stock torsion bars in might be the way to go as I have all the parts. Just feels like the car is close and I'd be taking a step backwards - on paper anyway.

We could not afford to test the torsion bar setups like we have with the coilovers.There are sites that show spring rates in comparisons to torsion bar equivilants.Keep in mind, we are running more tire and wheel also.J

Sorry, did not go back and read all posts-wrapping Christmas-definitely coil overs front and rear.Just trying to help.J

With 21 mm T-bars & a 22 effective rate AR bar, I found that 275lb rear springs
put the front AR bar half hard for the balance I want (slight oversteer)...no push under all conditions when the tires are semi-hot or better. When the tires are cold & dirty the car is all over the map.

The car has a slight tire stagger front to rear....9.5 X 10, but the cantls don't hold as well as the square sides, IMO

Aaron if you want to try the rear coil-overs and can sleeve them to work cheaply, I have a set of 8" 225lb 2.5" id springs sitting here that I won't be needing for a while pending my front suspension pan replacement and Smart Racing sway bar purchase/install.

I would think that 225 rear with plastic bushings should be in the ball park of what you want for 21mm fronts.

Not to knock JP's setup as it seems to work on that car but huge staggered slicks, needle bearing suspension and 200+hp in a 1700lb car is not really the same as a 120hp 914-4 on heat cycled out used 205s like Aaron runs.

That would at the very least let me know if I'm headed in the right direction! Evan, I don't care what anybody says about you - I think your a good guy! How long before I can buy you that beer?

I do have to consider balancing suspension to tire... I have a "fresher" set of of used BFG R1's to put on once I start getting this thing tamed...

Merry Christmas everyone! It's after 11pm here on the East Coast!

I forgot to say I appreciate the help. I'm always looking, talking, testing others stuff for months before I make a move with my car.

Thanks again.

Haha 8 months, 3 days, 12 hours, and 4 minutes until is government sanctioned. I think you are ok too Aaron, Merry Christmas

So, if you use the adjustable coil over set up on the rear, what length springs will you use? 8" or 10"? I have a set of collars that need to be installed after I buy springs but I don't know what length to get.

For what it's worth this is the set up I am planning to run:

914-6
Front:
- 21mm t-bars
- 22mm adjustable sway bar

Rear:
- 200# springs
- 15mm(?) stock rear sway bar

The key here is the 21mm T bars......those are pretty damn stiff. Bounce your butt on the front fender and note the compression. My 175 lb ass moves it about 1/4 inch.

Another thing that comes up is inside rear wheel lifting. When it lifts, you go nowhere unless you have a clutch type LSD. A rear sway bar will exacerbate this condition.

As I said above, the 275lb springs (no rear bar) keeps both rears planted and balances the front springs. I found this balance before I went to slicks and a major weight loss.....it stayed the same in the "after" condition.

Here's a pic from when I was setting up the suspenders. IIRC this was with 225 lb rear springs. Note the tire smoke & the faint black line on the asphalt to the rear of the car. 250s did the same, 300s didn't......275 were as soft as I could go.

Now days, the car does the same thing every time (once the tires start working).
That is attributable to chassis stiffness and decent shock valving. The cantis up front (on 8s) are necessary to keep wheel width managable.....I tried 10 inch wide wheels there and the "scrub radius push" was incurable.