Rear lifting in hard coenering, Too much spring? Options

[retrotech]

I wasn't ready to deal with the suspension yet, but today I was told my the guy behind me. In hard cornering, instead of being flat, thew rear corner would lift. Thats not good. This was the first fairly hard drive, with some R Gruppe cars.
The PO said they were 400#, I assumed he was mistaken, that didin't seem reasonable. He said he has had a track 914, and that is the set up he was successful with. So what do I need to do. It has front sway bar, don't know what the torsion bar is.
What are the suggestions. I don't care about comfort, I just want an optimal performance for street & track.

1970 w/2.8 2000#


Thanks

[smg914]

The rear wheel lifting on hard cornering on a race track is why many people remove or disconnect the rear sway bar.

[john rogers]

Sounds like the front is too soft if the rear is lifting. Of course front wheel drive cars do it all the time and I have seen some 356's do it also. Not good for a rear wheel drive mid engine car, unless you are braking really hard. I imagine you are not braking though so that if in fact the rear springs are 400# they are probably too stiff and need to be softened up about 100# to 150# or so. I run 300# in my race car but it is using Goodyear slicks and 23mm front T-bars and really big front anti sway bar. Of course you can always go stiffer on the front but that would be for a race shop to evaluate and see what you actually have. The rear springs can be measured and the front T-bars are color coded as to size or stamped.

[retrotech]

Can you tell me the measurement of the different spring rates?

[john rogers]

The best way, if the tag is missing from the spring(s) is to have a shop measure them on a spring compressor. If you look closly there may be a small tag or stamped number that can be referenced. Good luck

[sixnotfour]

No matter how stiff the rear springs are , if you have no rear sway bar , wouldnt the shocks allow the wheel to droop and touch the pavement. (IMG:http://www.914world.com/bbs2/html/emoticons/confused24.gif)

[xitspd]

I am running a 3.6 in my 914 with 400 lb. springs. A little too much! I am in the process of moving to 300 lb. springs...... I am running a factory rear sway bar (original equipment). I like it!

[retrotech]

"A little too much", translates to what when you are driving?
I have no rear sway bar. I was told because the springs are so heavy they are over riding the rebound of the shock, causing lift?
You are going to 300#, other say #150 - 200.
Allot of diffrenet opinions. Seems like there should be "the sweet spot".

[retrotech]

I just found out it is a 21mm front Torsion bar, and stock 19mm front sway bar.
I want to get it set up right. What should I change.

[eeyore]

Yikes!

You do need rear springs down in the 150 lbs range.

[anthony]

I'd think that 150lb. rear springs would be kind of wimpy for 21mm torsion bars.

[eeyore]

QUOTE (anthony @ May 23 2005, 12:01 AM)

I'd think that 150lb. rear springs would be kind of wimpy for 21mm torsion bars.

Oops. I was thinking there was a rear swaybar too...

[Bleyseng]

21mm front T bars=
21 Front sway bars and #200 lbs rear springs plus it depends on the tires and rims/track or AX?

[slivel]

Keep in mind that with the stock trailing arm, the geometry of the trailing arm-spring-wheel yields a motion ratio of about 1.68. This means that a 200 lb/in spring will have an effective rate at the wheel of 1.68 x 200.

The front geometry is much closer to 1:1 with my coil over suspension. I don't know what the torsion bar MR is. Maybe someone else here has calculated it for the front with torsion bars.

[retrotech]

The last post is over my head, but now I am wondering which is the better way to go. Lower rear spring tension, or increase front torsion bar? I have BFG T/A R1's on now. I know they won't last long on the street. I am waiting for Azenis 215x45x17 to come in. Please keep the sdvise coming.

Thanks

[tesserra]

Get a larger front bar that is adjustable. The Tarret bar that Brad sells is really nice and I think you could get them up to 31 mm.
You already have the rear springs in the car and you have not modified the front enough for the rear, an adjustable big front car will do wonders, and it will not harm ride comfort.

George

[slivel]

QUOTE (retrotech @ May 22 2005, 03:04 PM)

I wasn't ready to deal with the suspension yet, but today I was told my the guy behind me. In hard cornering, instead of being flat, thew rear corner would lift. Thats not good. This was the first fairly hard drive, with some R Gruppe cars. The PO said they were 400#, I assumed he was mistaken, that didin't seem reasonable. He said he has had a track 914, and that is the set up he was successful with. So what do I need to do. It has front sway bar, don't know what the torsion bar is. What are the suggestions. I don't care about comfort, I just want an optimal performance for street & track. 1970 w/2.8 2000# Thanks

In your first post you said, .What are the suggestions. I don't care about comfort, I just want an optimal performance for street & track. I think many will agree that you can't have "optimal" performance in both worlds. Anything you do will be a compromise. Even between tracks you can change spring or torsion bar rates to optimize. If your track experience is minimum, I would recommend the previous posts who suggested staying on the softer side on the rear for now - something 200 or less. If you are lifting a rear wheel on cornering, you are really unbalanced in the extreme. This is a characteristic of a front driver not RWD. There was also some good advice about matching the shock valving to your spring rates - otherwise one is overpowering the other. You can "stiffen" the suspension by just repalcing the shocks with high compression/rebound shocks. Many people do this and it works to a point, but the better solution is a shock that is valved to be complimentary with your spring rates and corner weight.

My point about the motion ratio is that if you have 300 lb/in spring rate in the front and want to match it in the rear, putting 300 lb/in springs won't do it because of the leverage from the moment arm of the rear suspension. You would wind up with 504 lb/in in the rear.

[sixnotfour]

You need to figure out what the car really has , not what the PO told you, If what the guy behind you is saying , you should have been nearly spinning out from all the oversteer, from the really stiff backend.

The guy Behind always tells you you're car looked scary. (IMG:http://www.914world.com/bbs2/html/emoticons/monkeydance.gif)

[john rogers]

Jeff has a good point about what the guy behind tells you. Also the points about the PO telling you what is there being hazy is right on too. As I noted earlier, I'd say get then springs measured and see what they are. Then decide what you want to do with the car since a setup for auto-x is much different than the setup for a track such as Willow Springs or CA Speedway. I'd also say have someone video tape or take picts of the car in action, video is best and you can slow it down to watch what the car is doing and get some resuslts that way. Remember, a good rule of thumb is: if a corner comes up, either the opposite corner is too soft or the rising corner is too stiff.

[retrotech]

Thanks for all of the input, I guess there is no clear answer at this time. But just to clarify, I was not lifting a wheel. The p[oint was the car was not staying flat in hard cornering, rather the rear was tilting too much. lifting the chassis.

Thanks again