Drag Racing Strut Selection for Coil Overs?

[JustinOlson]

I'm doing coilovers on my 280z. I'm just unsure what struts to use.

 

I wanted to try the Bilsteins (F4-P30-0032-MO). They seem like a big PITA to do on a 280z strut tube.

 

I'm left wondering if I should do Tokico Illumina's or HTS112? Do the HTS have enough travel for drag racing? Are there any other recommendations that aren't over $175/strut?

 

Justin

[johnc]

The HTS112 has 6" of shock travel. How much travel do you need?

 

My drag race shock thinking:

 

Front Shocks/Suspension

 

Should be droop limited to balance out front end lift while still keeping the front wheels just touching the ground. Lifting the front wheels completely off the ground is counter productive because you're using energy to continue to lift the front after weight transfer has reached 100%. Having the front wheels just touching the track gives the driver some options if the car gets out of hand and also lets the front suspension control the front coming back down if the driver lifts.

 

Rebound valving should be fast enough to allow the wheels to droop fairly quickly. Compression damping should be firm enough to control the front end as the weight transfers forward. Compression damping should not be too firm because you want the front to drop all the way down by 1/2 track so the car has better aero as the speeds increase.

Rear Shocks/Suspension

 

Should be firm enough to keep the the car off the rear bump stops. Bottoming the suspension does bad things from compliance and grip. Uneven bottoming will put the car into the wall or the tree. Compression damping and spring rate are important to control the rear suspension under acceleration. Rebound damping should be firm to keep the car from hopping/popping up if the car breaks traction. It should also be firm enough to control the rear suspension as weight transfers forward.

 

Overall Balance

 

Once past 1/2 track the suspension should be settled enough that the driver has some control and options if the cars squirrelly. At speeds approaching (and past) 100 mph on a narrow track its nice to have some handling capability in the chassis.

 

That's all just my opinion.

[wingnutthehutt]

You're pretty right on, John C. A quick note: On the rear, it's far better to have your springs too soft than it is to have them too stiff. A stiff spring will blow off the tire immediately but a soft spring will compress and grab.

 

Also, the front wheels coming completely off will transfer yet more weight. Some cars need that longer duration transfer, especially low powered (read less than 700) cars that don't have the ability to continue pushing the rear tire into the ground. If the front end comes down too quickly, then all of the transfer is lost. That's commonly what is the cause of the car blowing settling and then blowing the tires off.

[johnc]

On the rear of a drag car I think a progressive spring is a good idea. The car needs to squat and be compliant for a couple inches of bump travel but then the spring needs to be stiff enough to keep the car off the bump stops and still handle a 50% of the total vehicle spring weight. You can also try a dual spring setup using two springs of different rates.

[wingnutthehutt]

You can also try a dual spring setup using two springs of different rates.

 

Are you suggesting running two short springs one on top of the other or different left and right?

[johnc]

Two springs, one on top of the other. One 4" tall and the other 8" tall.