Knowing when to rebuild coilovers.
- Thread starter SupraMario
- Start date
Well it really depends on some things.
I rebuild the dampers on my brother's car every season. This is the TIP Setup that I designed and for the most part it's just a fluid change and sometimes it might not even need it. It's just standard practice for me.
For off the shelf coilovers, some places offer a "rebuild" but a lot of times you're just buying a new shock and putting that in, other times they will actually rebuild them and replace seals, but I haven't really kept track of who does that.
For replacement dampers, there's really no point to rebuild them unless you want to get them revalved. But in some cases it may be cheaper just to rebuild rather than buy new ones, but it depends on what is messed up.
The reasons you would rebuild a damper, besides just doing it as a maintenance thing, is because they're blown or leaking. The seals inside the damper will wear with use, it's inevitable. Why people get frustrated when they're old dampers blow is beyond me. They would be like getting mad that you have to replace brake pads or a clutch.
There can be some external signs. Excessive fluid on the shaft would tell you that the shaft seal is worn and leaking. Fluid coming out around the top of the damper not on the shaft, would tell you that the rod guide seal is leaking. Depending on the construction of the damper, there might be other signs, but generally any fluid on the outside of the damper that should be on the inside is a bad sign.
Another sign that the damper is blown is if the shaft does not rebound. This is only true with pressurized dampers, which pretty much all monotube dampers are, but there are some twintube dampers that are not pressurized. If it's a monotube and you compress the shaft but it does not extend, this means that the shock has lost it's pressure. This means that the nitrogen inside the damper has either leaked out of it's fill hole or has leaked past the dividing piston and is now mixed with the fluid.
Sometimes there are sounds, it can sound like a lot of different things, but dampers are usually pretty quiet in operation, so if you're hearing something from it, it's probably a bad sign. Sometime you can hear something like the sound when you're using a plunger in a toilet, the piston sloshing past and into the fluid, this would be one of the bad sounds.
You can also usually feel if the dampers are blown. A blown damper will not contribute as much damping force, so the car will tend to oscillate more after inputs. Depending on how the dampers are valved, sometimes it's easy to tell if it's blown and sometimes it's not. I have driven on new setups that had such poor valving that they felt like they were blown.
It can also not exhibit any of the external signs and still be blown. The seals around the piston can wear as well and if this happens, the fluid will go around the piston rather than through it and less damping force will be generated. So you will be able to feel this when driving.
Besides that the only real way to tell what shape a damper is in is to put it on the dyno. You can compare the dyno curve for the damper against what it should be valved at. So if you have a fresh damper and a used damper, this would give you an idea of the shape of the used damper.
Tim
I rebuild the dampers on my brother's car every season. This is the TIP Setup that I designed and for the most part it's just a fluid change and sometimes it might not even need it. It's just standard practice for me.
For off the shelf coilovers, some places offer a "rebuild" but a lot of times you're just buying a new shock and putting that in, other times they will actually rebuild them and replace seals, but I haven't really kept track of who does that.
For replacement dampers, there's really no point to rebuild them unless you want to get them revalved. But in some cases it may be cheaper just to rebuild rather than buy new ones, but it depends on what is messed up.
The reasons you would rebuild a damper, besides just doing it as a maintenance thing, is because they're blown or leaking. The seals inside the damper will wear with use, it's inevitable. Why people get frustrated when they're old dampers blow is beyond me. They would be like getting mad that you have to replace brake pads or a clutch.
There can be some external signs. Excessive fluid on the shaft would tell you that the shaft seal is worn and leaking. Fluid coming out around the top of the damper not on the shaft, would tell you that the rod guide seal is leaking. Depending on the construction of the damper, there might be other signs, but generally any fluid on the outside of the damper that should be on the inside is a bad sign.
Another sign that the damper is blown is if the shaft does not rebound. This is only true with pressurized dampers, which pretty much all monotube dampers are, but there are some twintube dampers that are not pressurized. If it's a monotube and you compress the shaft but it does not extend, this means that the shock has lost it's pressure. This means that the nitrogen inside the damper has either leaked out of it's fill hole or has leaked past the dividing piston and is now mixed with the fluid.
Sometimes there are sounds, it can sound like a lot of different things, but dampers are usually pretty quiet in operation, so if you're hearing something from it, it's probably a bad sign. Sometime you can hear something like the sound when you're using a plunger in a toilet, the piston sloshing past and into the fluid, this would be one of the bad sounds.
You can also usually feel if the dampers are blown. A blown damper will not contribute as much damping force, so the car will tend to oscillate more after inputs. Depending on how the dampers are valved, sometimes it's easy to tell if it's blown and sometimes it's not. I have driven on new setups that had such poor valving that they felt like they were blown.
It can also not exhibit any of the external signs and still be blown. The seals around the piston can wear as well and if this happens, the fluid will go around the piston rather than through it and less damping force will be generated. So you will be able to feel this when driving.
Besides that the only real way to tell what shape a damper is in is to put it on the dyno. You can compare the dyno curve for the damper against what it should be valved at. So if you have a fresh damper and a used damper, this would give you an idea of the shape of the used damper.
Tim