Lowering Your Car with Threaded Shocks or Spring Collars

by Rob Schermerhorn on February 10, 2012

Sometimes the least expensive modification is the most rewarding. Certainly, lowering your car not only improves appearance, but also performance, especially at the racetrack. You may not know this: your Ferrari is already built for ease of ride height adjustment, that’s where the low cost comes in.

Threaded body shock absorber

Do you have threaded bodied shocks?

The procedure is straightforward. Before you start, schedule a wheel alignment for the next day or so. Lowering the car an inch or so will affect toe and camber, to the detriment of handling and tire wear.

You also need lower spring collar wrenches in the correct sizes to make this easier. Mine are Snap On, but they’re also available industrially. The wrenches will wrap partly around the spring perch and fit into the notch. Two sized, the smaller is to release and tighten the locking nut. Snap On part numbers are AHS 301 and AHS 304. Shaped like a “C” with a handle and a tooth at the end of the “C” to fit the notch in the nut (lower spring perch and lock). The inelegant way is a screwdriver used with a hammer, but this gouges the aluminum perch and locking nut. Last resort if the lock nut won’t loosen: Spray some PB Blaster on the threads first, wipe the road dirt off the threads, then index the collar with a paint marker or paint or nail polish so you don’t lose count.

Take notes. Write down ride heights before and after, note how many turns on each collar, note where / how you measured. If one just goes down the same number of turns both front and rear, you will upset the rake of the chassis, as the front and rear motion ratios are different.

Get the factory ride height data first, don’t guess. You can measure the ratios on your car relatively easily if the manual does not have the information. (Dial indicator on the shock rod measuring shock body movement, suspension assembled with no spring; dial indicator on the ground measuring vertical hub or spindle movement.) Some service manuals give the motion ratios of the suspension so you or the technician knows how many turns down on the spring collars yields how much chassis lowering. Remember, if you turn LF 12 turns and RF 15, your corner weights are off, either even up the collars or plan on adjusting corner weights with load cell weight scales. The springs are pre-loaded from the factory.

You won’t be on a level surface so when in doubt, just ensure both fronts are turned the same, and both rears are turned the same to yield the necessary ride height difference. Use the motion ratios to calculate how many turns of the spring collar yields the correct ride height change.

Lowered Ferrari 348 with Delta Vee suspension

Lowered with Delta Vee Motorsports suspension

For example, the Ferrari 348 and F355 front ratio is 0.70 and the rear is 0.85. So, lowering the spring collar 0.70 inch in the front and 0.85 inch rear lowers the chassis uniformly one inch and maintains the relative ride height front to rear (known as chassis rake).

The collars move 1.5mm for each complete turn (thread pitch), so in the above example, turn the front 12 turns and the rear 14.5 turns down. (0.70in x 25.4 mm/in)/(1.5mm per turn).

Lowering will change camber and toe settings, so an alignment is necessary. If you forget the number of turns you’ve already done on the collars and get confused, you will require a set of load scales to reset corner weights. If you pay attention and take notes, you won’t need the scales, assuming Ferrari set the car correctly from the factory, which they usually do.

Remember you must realign the wheels. There are ways of doing this at home too, but one subject at a time. As for wheel alignment specifications, stick with the factory, noted in your owners manual and factory workshop manual. If you’re going racing, send me an email for my set up recommendations.

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