Jump to content
HybridZ

Front end travel


Recommended Posts

Whats the best way to limit the front end travel on a 1970 240 ? This car is back halfed but has stock front suspension it has about 18" of travel in the front end. It leaves on the wheelie bars and stays on them till you lift. I need to limit the front end to about 2-1/2" to help bring the front back down. It looks like the best way will be to run a cable from one of the bolts that bolt the front suspension to the body down to one of the bolts that bolt the strut rod to the lower control arm. Is there a better way?

The only picture I have so far is on my web site.

Thanks

Link to comment
Share on other sites

Unless you've done something to the front suspension of your Z, normally they don't have 18" of total travel. Its usually better to build droop limiters into the shocks, but until you can do that I would use the anti-roll bar to control droop. On each side, run a cable from where the crossmember bolts to the frame out to the the anti-roll bar end or link.

Link to comment
Share on other sites

All that will do is pick the front wheels up sooner. You have to either lower the CG of the car, move the CG forward, extend the wheelie bars back and down (which will have the side effect of removing vertical load from the rear tires, unfortunately), or increase the wheelbase. A short, high car like a 240Z will always want to flip over backwards. It ain't about the suspension, it's about F=MA and where the F is reacted. How much hp you talkin'?

Link to comment
Share on other sites

Katman

I understand about center of gravity and how a drag car works this is not my first trip down the strip. The problem is not with going to high. With the front end limited the front end will come back down sooner. With as much travel as this car has the front end stays up the entire length of the track with the help of the front springs pushing it up. I have been real successful with doing this in all my other cars over the years. They all have Upper control arms and are easy to limit on the upper control arm. This is the first time I have had a strut car to limit. I got it down to 4" tonight and we are going to Albany tomorrow and I will find out how it works. I would like to get it down to 2".

Thanks for all your advise

Link to comment
Share on other sites

Can you not adjust the wheelie bars so that they make contact at a lower angle instead of later when the front gets too high? It would seem to me that no matter what you do with the front end, until something else limits the travel (less torque, less traction, lowered bars), nothing will change.

Link to comment
Share on other sites

I don't know much about drag racing, but if the problem concerns the front springs pushing the front of the car up, using shorter extended length springs should help.

 

If you reduce the front suspension droop, don't you run the risk of having the front wheels off the ground more and so lose steering?

Link to comment
Share on other sites

John,

 

congrats on the new time. Do you have any pics of the limiters you used? Is it permanent or can you hook it up when going to the track? I am nowhere as quick as you but I know what you were going through with the front-end lifting as you accelerate. Do not know if I will need the limiters but just in case, let me know. Send me private email ifyou like.

 

Seeing the odd camber/toe of the Z front-end at launch on your site is scary to know the car could be doing that at speed.

 

I could only dream of my car weighing 2200lbs but if it could.......

Link to comment
Share on other sites

Okay, if we had stock springs at like 83 lbs/in for a 240, and there's about 635 lbs per corner on the wheels for a stock engine, that's about 7.6 inches of squish on the springs before they are completely unloaded. Seems like theres about 5 inches of droop from stock ride height to when the shock limits the spring extension anyway, so I'm confused about the 18 number.

 

Regardless, I can see theoretically how you fixed it. Say acceleration raises the front end 4 inches. Well the spring is still compressed 3.65 (7.65-4) in our example, which means it is still helping acceleration push up on the front of the car by 3.65*83=303lbs per side. If the CG and acceleration are such that 606lbs will continue to rotate the car then we have a problem. If the springs were travel limited to 4 inches, then the full weight of the front end would resist the overturning moment due to acceleration, not weight minus 606lbs. So the front might stay down. Cool. At 18 inches I assumed the wheels were entirely off the ground and therefore nothing could help with regard to travel limits. Interesting.

Link to comment
Share on other sites

Katman

The 18" I spoke of in the first post is total suspension travel from a rest to the point that the tires come off the ground. If you where to mesure from the front bumper to the ground on a leval surface. Then Start to jack up the car the bumper would raise up 18" before the tires would come off the ground. That is Alot. It is possible that someone has put the wrong struts in this car I have not had it that long. But with it limited to 4" it works like a dream.

On a car with limited traction front end rise helps move more waight to the rear and helps traction but with enough traction it can be a pain. Limiting the front also helps get the tires out of the beams and improves reaction times & ET, the car is spending less time going up and more time going forward.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...