Reworking rear suspension on AG sandcar

[moondog897]

I need some help. I've got an AG sandcar that was set up with 2.5 coilovers only in the rear and then someone added some 2 inch double bypasses in front of those. I want to set it up with 2.5 bypasses in the rear and the smaller coilovers in front(still talking about rear suspension). I have some new 2.5 triple bypasses on the way but I definitely don't have the room to clear 2.5 coilovers as well. The question is should I have new upper mounts made for the shocks so I can run 2.5 on both or would a 2 inch coilover be fine? If you zoom on this picture that's the current set up.

 

[Jtmoney714]

I would want the bypass behind the coil over. And I would think a longer 2.5 bypass with a 2.0 coil over would be just fine. 

 

[moondog897]

I would want the bypass behind the coil over. And I would think a longer 2.5 bypass with a 2.0 coil over would be just fine. 

That's the plan, I've got 2.5x14 bypasses and was going with a 12 inch coilovers either 2 or 2.5 with new upper mounts. Just wasn't sure on the coil size. I've done a lot of work on the car and rebuilt all the shocks but never got into any tuning yet.

 

[KLC]

I would want the bypass behind the coil over. And I would think a longer 2.5 bypass with a 2.0 coil over would be just fine. 

In a nutshell, this is what I am thinking also. 

Rear shock mount geometry is of paramount importance. Just swapping the position of the bypass and coilover will work wonders for the rear suspension performance tuning wise. If you use a shorter coilover you'll have to increase the spring  and valving rates though due to leverage losses. IMO in that situation a 2.5 coilover would be a benefit. 

 

[moondog897]

In a nutshell, this is what I am thinking also. 

Rear shock mount geometry is of paramount importance. Just swapping the position of the bypass and coilover will work wonders for the rear suspension performance tuning wise. If you use a shorter coilover you'll have to increase the spring  and valving rates though due to leverage losses. IMO in that situation a 2.5 coilover would be a benefit. 

The larger bypass will be in the rear on the new setup, that was my thought for being able to tune it a little easier. Once I get the bypasses I need to determine the coilover size. If I went to a 2 inch coilover I'd definitely need heavier springs. Is there a good way to determine baseline spring rates?

 

[KLC]

You will have to weigh the 4 corners, it' still an educated guess. Our old car used 350/450 and was not quite enough spring, we will be putting 500/600 on the new car but that is just a starting point. With a shorter shock you may end up with something more. 

 

[moondog897]

You will have to weigh the 4 corners, it' still an educated guess. Our old car used 350/450 and was not quite enough spring, we will be putting 500/600 on the new car but that is just a starting point. With a shorter shock you may end up with something more. 

Thanks for the input, one more question. How are you weighing your cars? Bringing to a scale or have you used a hanging scale?