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Author Topic:   swing arm car rear end travel
mike simpson
Member
posted June 19, 2001 08:39 PM
I HAVE A SWING ARM CAR AND HAVE NO IDEAL
WHAT THE TRAVEL SHOULD BE ON THE REAREND
HOW MUCH TRAVEL CAN YOU HAVE AND NOT RIP
OUT U-JOINTS ?
RIGHT NOW IT HAS ABOUT 21/2 INCHES WITH
A 1200LB SPRING. SHOULD I HAVE MORE TRAVEL
OR SHOULD THERE BE LESS?

------------------
the bartman


wfoondirt
Member
posted June 20, 2001 09:12 AM
I assume by the fact you have a 1200lbs spring that you are reffering to a watts-link (z-link) style, with the springs on the lower links. Its not uncommon to see 2-3 inches of travel on these type suspensions because the torque-link is the only thing resisting the torque of the rearend. Personally i like to see around an 1" but not because of u-joint problems. I also assume the 2 1/2" that you are talking about is movement under accel, do you know how much travel you are getting on decel? Its important on this type of suspension to have the rear-end properly dampened to keep the rear-end from rotating to far down under decel. Another note on losing u-joints, be sure to check your yoke very close to make sure i hasn't spread from losing the previous problems.


mike simpson
Member
posted June 20, 2001 10:08 PM
The yoke was bent and i have replaced it.
The 21/2 inches of travel is under accel, but i am not sure how much travel there is on decel. you said you prefer 1'travel so to get less travel i need to get a stiffer spring ? but how many lbs should i increase the spring. Also on decel,the last time i slung the shaft out was when i let off going into the corner so it is possible that the rearend is coming back too far.
the pinion angle is set at 5 degrees and with the 2 1/2' travel the angle under accel. is 0 degrees.
the way the car is setup it hooks good drives through the corners good it just wont stay together long enough to finish a race.

thanks for the info any thing else would be greatly app.

thanks for you comments any other help would be app.

------------------
the bartman


CUSTOMPERFORMANCE
Member
posted June 20, 2001 10:18 PM
IF YOU ARE LOOSING YOUR DRIVE SHAFT IS IT POSSIBLE THAT ITS TOO SHORT?


racermay
Member
posted June 20, 2001 11:19 PM
You should invest in a longer yoke. I have the in stock. It is 3/4" longer than standard GM yoke. It eliminates problems like you are having. It is possible that your shaft is too short, but it is easy to check. At ride height place 3 fingers between yoke and tailhousing. if you can get another finger in there, it is too short. If you can't get all 3 in there it is too long. www.mmraceequipment.com


irace74
Member
posted June 21, 2001 03:16 PM
according to spring theory, the travel on the spring aimrs the rating equals the load. in your case a 1200# spring at 2.5" of trave would equate to 3000# of force. If you want to limit this travel to 1" the required spring would be closer to 3000#. In my opinion this appears to be excessive. I might try a 2000# spring and chect the travel it soould be limited to 1.5" if the track slicks off badly the heavy spring sould result in no wrap-upof the rear end and this would be a bad thing.


wfoondirt
Member
posted June 21, 2001 04:16 PM
Like i said its really personal preferance on the torque-link travel. The only purpose for the spring on the top link is to cushion the torque shock to the tires. And really even on a slick track, if the car is hooked up well enuff you can run a solid third link.
As far as the amount of travel goes, it also depends upon mounting height and angle.
Personally i like the travel to be as minimal as possible without the driver having problems keeping the tires under the car.


HEAVY DUTY
Member
posted June 23, 2001 11:04 AM
Good point heavy. What type of bisquit bar do would you reccomend on a z-link? And what kind of rates are available for them?


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