Leaf spring sliders

Guest · Post by **Guest** » Tue Aug 31, 04 7:39 am

Has anyone used a slider mechanism for locating the rear of the leaf springs. I believe they are mainly used in circle track racing, but should be useable on the street. I tracked a supplier down ? AFCO performance products

http://www.secureperformanceorder.com/a ... ductID=985

They have the advantage that they help to lower the rear of the car slightly (as the rear spring eye is placed higher on the car) as well as point the front of the axle pinion down if you need more driveshaft angle - like me. I would like to know if they are suitable and long lasting for street use or if they give any problems. Any feedback would be appreciated.

Thanks
Dave

Dave-R · Post by **Dave-R** » Tue Aug 31, 04 8:30 pm

You sure you want your pinion to point down?

If the front and rear UJs are not at the same angle they have to oscillate at different speeds. If they do that you get harmonics. That results in speed associated drivetrain vibrations.

Dave-R · Post by **Dave-R** » Tue Aug 31, 04 8:32 pm

Seem to be loosing some text there.
Anyway. You have to set the components up so their center lines are parallel and so that the angle made THROUGH the U-joints is 3-degrees or less as shown in Figure 2.

While it is possible to run at zero degrees through the U-joints, something more than one degree and less than three degrees seems to run smoothest.

Guest · Post by **Guest** » Wed Sep 01, 04 7:24 am

Ok - it's been a while since I've done any reading up on driveline angles - and obviously I've got it wrong. Thanks for putting me right Dave - What happens when you are accelerating under full power - the pinion nose rises and the driveshaft angles change - especially at the rear and obviously the more power you've got the more the pinion nose will rise. I take it you need to aim for zero degrees at full power.

P.S. Dave I haven't forgot about those photos you asked for on the Watts linkage. I had the car up on axle stands for the first time on Saturday - and did take some photos - but the light was playing against me and they came out very poor. - I will take some more this week and get them on here by next week hopefully.

Dave-R · Post by **Dave-R** » Wed Sep 01, 04 9:50 am

Now why would the pinion rise much under full power?

That's what an adjustable pinion snubber is for!

Get the angle right for driving along the motorway at a steady speed. You will be glad you did.

If you feel the pinion will rise slightly while being driven along at 70mph then by all means adjust your pinion angle slightly nose down from perfect (when stationary) to make up for that. I think this is what is meant as "slightly nose down" and it has been miss-understood over the years.

The adjusting wedges you can get will also drop the rear ride height but only by mm. If it is far out your only choice is to remove the axle and re-weld the spring perches in a better position.

Alex · Post by **Alex** » Wed Sep 01, 04 10:33 am

Something to bear in mind is if the car is mostly street driven you need to set the drivetrain up so the prop joints are seeing 1 deg at the min, this allows the bearings in the joint to rotate, if you set the joints dead straight the bearings will not move and the joints will wear very quickly.

Guest · Post by **Guest** » Thu Sep 02, 04 9:19 am

I want to lower the car anyway, so the fact that the shackle raises the position of the rear of the leaf spring is a good thing. By the way I have already raised the front spring eye by about 2? (by the way of custom made front perches with three hole positions), thus turning the nose of the pinion up ? this is why I wanted to lower the angle of the pinion.
On another note I am planning on fabricating traction bars the same as the ?slide-a-link? bars made by Competition Engineering www.competitionengineering.com (under the new products section) - has anyone used these and if so what is your take on them ? I am planning on a 493? RB pushing out around 600+ horses (and possibly a 250 horse Nitrous kit on top) ? so even the Superstock springs that are under the car at present will have severe difficulty with handling that kind of power. Dave I?m not so sure that an adjustable pinion snubber would do the business there either?

Blue · Post by **Blue** » Thu Sep 02, 04 10:00 am

I havn't seen this kind of slider before, my first thoughts are that It may well restrict your total suspension travel as the rear shackle will allow you a lot of "rise" on launch. Also I can see that it might have the effect of increasing the spring rate as the leaf would be acting directly on the chassis rather than through a lever (the rear shackle)? If you are planning on building your own traction system have a look at this set up that a guy in Denmark used on his 9 second Dart.
http://www.bigblockdart.com/3link/3link.shtml

Dave-R · Post by **Dave-R** » Thu Sep 02, 04 10:42 am

I like that system Blue.

So do these systems allow you to run the car without the spring perches welded up?

I was just thinking that this would allow you to run one pinion angle on the street and then adjust it for the track. It might also allow you to make adjustments to get rid of any vibrations.

The watts linkage will prevent the axle moving sideways on the springs anyway but without one a simple tag welded to the axle against the side of each perch would do the same thing.

Guest · Post by **Guest** » Thu Sep 02, 04 4:31 pm

Dave - What do you mean when you say, ?run the car without the spring perches welded up??

Blue - I had already seen the traction device you suggested, and have given it some thought, however I can see potential issues with this device that should not occur with the Competition Engineering device. ? In normal street use it will have the effect of increasing the spring rate as the leaf springs are no longer free to travel up and down in a vertical motion ? instead the springs will be forced to effectively twist around with the axle on a tangent, from the contact point between the slider and the body mounted support, thus as the suspension travels up and down, the pinion angle will change quite a bit. As I am building a car that handles as well, I can see the potential for suspension bind when cornering, - when the car attempts to lean in the corner, the outside bar is trying to hold the car up while the inside bar is trying to hold the car down, hence front and rear roll bars will be seeing very little load, and the rear inside tyre will have the tendency to unload ? This may cause the car to be more tail happy that would normally be the case. Again the beauty of the Competition Engineering set-up is that the traction bars only load up under acceleration, but under cornering etc they are free to change length relative to one another, hence the above problems should not manifest themselves.

Dave you stated ? ?The watts linkage will prevent the axle moving sideways on the springs anyway but without one a simple tag welded to the axle against the side of each perch would do the same thing? ? I take it you mean that the traction bars would have this tag welded to them, which would rub against the spring perches. If so you would need to support them diagonally across the axle.

Dave-R · Post by **Dave-R** » Thu Sep 02, 04 6:13 pm

GTX Dave wrote:Dave - What do you mean when you say, ?run the car without the spring perches welded up??

No idea. I was talking out of my backside.

I was in a hurry because we were going out for the day and I must have missed a gear in the brain box.

Blue · Post by **Blue** » Thu Sep 02, 04 7:00 pm

Ah, the old handling and drag racing dilemma! I agree that any kind of ladder bar is no use at all for cornering and I can see why you are looking at the comp engineering set up, this would seem to fit your criteria, it is a similar design to a cal trac set up which the guys in the states seem to have a lot of success with.

TrevD · Post by **TrevD** » Thu Sep 02, 04 9:27 pm

If you are making that much power why not go for a complete 4or 5 bar set up and coil overs , it will be far superior to the old leaf springs and fully adjustable to cope with all driving conditions , narrowed axle and massive rear tyres also helps ( except for the handleing bit

)