Seeking Tuning Advice for Gen 1 SVT Raptor Shocks on a Jeep XJ

[crrider826]

Certainly! Here's the updated forum post with your usage included:

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Hi everyone,​

I'm looking for tuning advice for Gen 1 SVT Raptor shocks that I've mounted on all four corners of my Jeep XJ. I know these shocks aren't popular for custom applications, but I'm committed to making them work for my setup. My goal is to fine-tune them for mixed on-road and off-road performance, with a particular focus on improving compliance and handling on moderate high-speed trails.

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Vehicle Setup:​

• Vehicle: Jeep XJ
• Shocks: Gen 1 SVT Raptor shocks (front and rear)
• Spring Rates:
  • 190 lb/in coils up front
  • 190 lb/in leaf springs in the rear
• Usage: Mixed on-road and off-road driving, including moderate high-speed trails, washboard dirt roads, rocky trails, and technical low-speed crawling

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Current Symptoms:​

On-Road:​

• Soft Feel: Suspension feels soft on pavement and dirt roads, with noticeable body roll during cornering and braking.
• Stability: The ride is generally stable at speed but could use better low-speed control to reduce roll.

Off-Road:​

• Rough on Washboard: The rear end tends to skip on extended washboard sections, making the ride harsh and unsettled.
• Rocky Terrain: At slower speeds on rocky trails, the suspension feels stiff and rough, especially over sharp impacts.
• High-Speed Control: High-speed handling feels good, with no bucking or bottoming out, but there's room to improve compliance, especially on moderate high-speed trails.

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What I've Done So Far:​

I've experimented with the shim stacks and side stacks but haven't modified the bypass tubes. Here's the current configuration:

Front and Rear Compression Stack (Piston):​

1.6 x 0.015
1.35 x 0.012
1.1 x 0.012
1.6 x 0.015
1.425 x 0.015
1.35 x 0.015
1.1 x 0.015
0.95 x 0.015
0.8 x 0.015

• This setup provides good bottom-out resistance but contributes to harshness on washboards and rocky terrain.

Side Stack:​

2.5 x 0.012
2.0 x 0.012
1.5 x 0.012

• I suspect the low-speed compression damping (LSC) is too soft, allowing too much flow at low speeds and causing body roll and a soft feel on-road.

Rebound Stack (Rear Example):​

1.4 x 0.010
1.3 x 0.010
1.1 x 0.010
0.9 x 0.010
0.8 x 0.010

• Rebound feels controlled, but the rear end skips on washboards, suggesting high-speed rebound damping may be too stiff.

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What I Think Needs Changing:​

1. Low-Speed Compression (Side Stacks):
   • The bypass ports seem to allow too much flow, leading to a soft feel on-road and excessive body roll.
   • Proposed Fix: Stiffen the larger side stack shims (e.g., 2.5 x 0.015 and 2.0 x 0.015) to improve LSC damping for better cornering and braking control.
2. Mid- to High-Speed Compression (Piston Stack):
   • The piston compression stack feels too stiff at mid- to high speeds, contributing to harshness over washboard and rocky terrain.
   • Proposed Fix: Soften the face shim (1.6 x 0.015 → 1.6 x 0.012) and possibly one mid-stack shim (1.425 x 0.015 → 1.425 x 0.012) to improve compliance, especially on moderate high-speed trails.
3. Rear Rebound Damping:
   • The rear rebound feels too stiff at high speeds, causing skipping on washboards.
   • Proposed Fix: Soften the smallest shim (0.8 x 0.010) or remove it entirely if the top-out washer controls high-speed rebound effectively.

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Questions for the Community:​

1. Low-Speed Compression:
   • Are my assumptions correct that the side stacks primarily control low-speed compression damping?
   • Would stiffening the side stack shims improve the on-road stability and reduce body roll?
2. Mid- to High-Speed Compression:
   • Am I on the right track with softening the larger shims in the piston compression stack to improve compliance over washboard and rocky terrain, especially for moderate high-speed trails?
3. Rear Rebound Adjustments:
   • Would reducing the 0.8 x 0.010 shim be enough to help the rear recover faster on washboards, or should I adjust another part of the stack?
4. Bypass Tube Modifications:
   • I haven't touched the internal bypass tube yet. Is this worth exploring, or can I achieve sufficient tuning through the shim stacks alone?

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Final Thoughts:​

I know these shocks aren't the most popular choice for custom applications, but I'm determined to make them work for my Jeep XJ. Any tuning advice or recommendations from those with experience in similar setups, especially for moderate high-speed trail usage, would be greatly appreciated!


Thanks in advance,


– Dedicated XJ Owner

 

[Evan03]

Have you looked into the shim stacker program to help with guestimateing stacks and changed?