Cory9584

What are 30 mm t bars equal to in spring rate? tia

chilibluepepper

Solid 30mm bars are roughly 340 pounds at the wheel.

ivai

Cory9584

i wonder how the ride would be with those around town with 400lb front springs? I want to upgrade my suspension but dont want to go to rear coil overs since i dont trust the mounting points for them

Lanny Curlett

Me Too. I have 400# on the way plus 31mm hollow torsion bars. What do you think it will do for me?

Cory9584

whats the difference between hollows and solids other than weight? The solids are stronger right?

chilibluepepper

Cory - can't tell you from experience. Although that is the setup I've put in my car, it is not yet operational.

Jeff - did I miss something? That popcorn munchin' smiley just makes me wonder!

samluke

I run 500lb up front, 29mm bars and 300lb helpers at the back. Delrin and spherical bushings. Straight through exhaust, spec stage 1 clutch.

My wife used to like to drive my car, now she won't go anywhere near it.

Its a track car but also a daily driver. For the street I use 16" wheels, to give it some compliance. For track I use 18's. Its harsh but I like it that way. With 18's it would harsher still.

Its not for everyone that's for sure.

Bri Bro

If you can adjust the shocks, I have read that the ride can be adjusted for street use. I have been in cars with 350 and 400 front springs and it wasn't bad. I am not sure i would have to take it on long trips every month. I am changing to 350/550 with Leda shocks, we can all get together in a month and compare notes.

Chart on spring rates vs torsion bar size from Sway-a-way.
22m = 98.03 lb/in
23mm = 117.11
24mm = 138.84
25mm = 163.47
26mm = 191.24
27mm = 222.40
28mm = 257.22
29mm = 295.98
30mm = 338.97
31mm = 386.47

Effective rate with a 29mm T-bar and 300# coilovers.
Rear coilovers have a 0.42 MR multipier so:
29mm= 296
300*0.42= 126
Rear spring rate total= 422

ivai

Alex, just munching on pop corn because this is a very interesting topic that I enjoy reading discussion on.. its also controversial sometimes.

RKD in OKC

180-400 lb front springs and 30mm bars are a good compromise for street/track. It is the combination that I put on Lindsey Racing's white 88 Turbo S when I owned it.

That combination with adj front and rear swaybars was recommended to me by Andial even though they had cup car springs and coil overs in stock and not the 180-410s or 30mm bars. They thought the cup suspension was too much for street/track. I had to get the 180-410 front springs directly from Porsche Motorsports. Yes, it is a little harsher ride than stock as it is double the spring rate. But it wasn't too harsh for me as my daily driver. To keep the ride street livable I kept the rubber bushings.

The setup was very well balanced. With a mere 270 rwhp and I was able to trade laps with a RUF at Hallett and was THE one to beat at autocross events. The Lindsey's have modified my old white car quite a bit past 270 rwhp, and still have that same suspension setup on it.

951tbro

cory,
i belive that hollows are to reduce weight, as the middle of the bar has almost no resistance to twist compared to the outside. its what would make most cense to me.

333pg333

There is not an absolute 'right' rate when doing suspension changes. In other words the combined rates of the springs and t-bars is calculable but this doesn't mean that if I run those rates in my car the same as yours that it will react the same. There are many variables. One of the things that gets left out of these discussions is the brand of shocks, but more importantly, the valving that they employ. My rates are 616 f and 708 r. Now these rates would have many saying that this would not be driveable on the street, but this is a daily driver and often on 18" wearing R-spec rubber + mostly solid suspension bushings/bearings all round! I am sure that this wouldn't work on some other brands of suspension due to the system and it's valving. In fact it is better on the street than the rebuilt and modified MO30 that was on it, and far, far superior on the track.
When I was getting the suspension custom made, I asked if I can go up in T-bar from the stock 'S' 25.5 mm. They said not to do it. So the system was built to work in concert with the stock t-bar and it does so very well. So if you go up in spring rate and t-bar rate, this may not be the best combination for you. Best to check out what the manufacturers of your system recommend.

Cory9584

thanks, that chart was exactly what i was looking for. now im just curious if the solids would be stronger than the hollows or as long as the rates are the same it makes no difference?

Bri Bro

It makes no difference in strength but the hollow are lighter by a couple of pounds. The price and size availability of the hollow might drive you towards the solid. The effective rate of the 31mm hollow is the same as the 30mm solid. It isn't that much difference in weight unless you are on a quest to take weight out of the car. I don't think it is worth the cost increase.