TommyT-Bone wrote:

Why are you replacing good shocks? Is it doing (or not doing) something?

Jake_The_Cat wrote:
Quote:

TommyT-Bone wrote:

Why are you replacing good shocks? Is it doing (or not doing) something?

I am guessing they are the original shocks. Car has 59,000 miles. I have a young lady that works for me and is also taking auto repair. she just finished suspension and steering. SO, what the heck she offered and I said OK.
Good think she did not just finish Engine Rebuild

Z51L9889 wrote:
I must respectfully disagree with Bogus and BillH's statements regarding shocks losing performance/ being shot at 30K miles. These blanket statements are somewhat misleading. I feel somewhat qualified to comment on this since I am Chief Development Engineer for Bilstein of America's OE (Original Equipment) product lines.

For the C4 program, Bilstein had to demonstrate to GM that the shock absorbers had a minimum 100,000 mile life expectancy. We certify that by performing severe accelerated tests in the laboratory and on vehicles. From purely a mechanical wear perspective, the components used to build the shock will last well in excess of 100K miles. What actually determines the true, real world, life of a shock is how the vehicle is actually used.

For a typical daily driver use mode, the shocks will go a minimum of 80-90K miles before they have any measureable loss in performance. What most people perceive as loss in shock performance is actually a reduction in the overall stiffness of the suspension due to the cumulative effect of wear of chassis components (bushing degradation, etc.). For this reason, Aftermarket shocks are typically stiffer than the OE parts they replace to attempt to compensate for the wear.

However, time is the enemy of a shock absorber as much as mileage. Using the OP's example of 59000 miles on the original shocks, I would say they are more than ready for replacement. Shocks on low mile vintage cars obviously sit for long periods of time without motion of the shocks.

One thing about shocks that many people do not realize is that the piston rod seals are designed to have a very small amount of controlled leakage. This is done to lubricate the interface between the seal and piston rod. When a vehicle sits for a long period of time, two things can happen. First, the seals can begin to dry out and can actually begin to bond to the piston rod. When the vehicle is next driven, the dry seal rubs against the rod and can cause rapid wear and possibly fluid leaks. Second, over long periods of time (many years) the shock can lose oil due to evaporation. This will eventually lead to a loss in shock performance. It is very possible to have a damper with significant fluid loss due to evaporation but no sign of external leakage.

To summarize, I agree somewhat with Bogus and BillH in the case of limited use vehicles, but it's more based on time than mileage. My recommendation is that if your vehicle is more than 10-15 years old and you still have the original shocks, they are most likely ready for replacement regardless of mileage.

I apologize for this being long winded, but I hope it is useful information.

Z51L9889 wrote:
I must respectfully disagree with Bogus and BillH's statements regarding shocks losing performance/ being shot at 30K miles. These blanket statements are somewhat misleading. I feel somewhat qualified to comment on this since I am Chief Development Engineer for Bilstein of America's OE (Original Equipment) product lines.

For the C4 program, Bilstein had to demonstrate to GM that the shock absorbers had a minimum 100,000 mile life expectancy. We certify that by performing severe accelerated tests in the laboratory and on vehicles. From purely a mechanical wear perspective, the components used to build the shock will last well in excess of 100K miles. What actually determines the true, real world, life of a shock is how the vehicle is actually used.

For a typical daily driver use mode, the shocks will go a minimum of 80-90K miles before they have any measureable loss in performance. What most people perceive as loss in shock performance is actually a reduction in the overall stiffness of the suspension due to the cumulative effect of wear of chassis components (bushing degradation, etc.). For this reason, Aftermarket shocks are typically stiffer than the OE parts they replace to attempt to compensate for the wear.

However, time is the enemy of a shock absorber as much as mileage. Using the OP's example of 59000 miles on the original shocks, I would say they are more than ready for replacement. Shocks on low mile vintage cars obviously sit for long periods of time without motion of the shocks.

One thing about shocks that many people do not realize is that the piston rod seals are designed to have a very small amount of controlled leakage. This is done to lubricate the interface between the seal and piston rod. When a vehicle sits for a long period of time, two things can happen. First, the seals can begin to dry out and can actually begin to bond to the piston rod. When the vehicle is next driven, the dry seal rubs against the rod and can cause rapid wear and possibly fluid leaks. Second, over long periods of time (many years) the shock can lose oil due to evaporation. This will eventually lead to a loss in shock performance. It is very possible to have a damper with significant fluid loss due to evaporation but no sign of external leakage.

To summarize, I agree somewhat with Bogus and BillH in the case of limited use vehicles, but it's more based on time than mileage. My recommendation is that if your vehicle is more than 10-15 years old and you still have the original shocks, they are most likely ready for replacement regardless of mileage.

I apologize for this being long winded, but I hope it is useful information.

Jake_The_Cat wrote:
Taking Sharon's C4 in for shocks. Not that it really needs it but what the heck.
Suggestions on brand? Belkins (sp) or what......
Don