aozora
24-01-2012, 02:15 PM
S2000 Vibrations from rear/”Do I need driveshaft spacers?”/”Do I need to replace my drive shafts/half shafts?”
Note: I may be off with the correct technical terms/names of certain drivetrain components and would have simplified it all slightly to avoid confusion. So please bear in mind when reading! And please try to ignore the crappy diagrams…
The S2000 rear drivetrain works off a number of components.
- The hubs (Connected to the wheel, brakes and control arms)
- Half shafts/drive shafts (Connecting the hubs to the differential output shafts – to avoid confusion with the driveshaft from the gearbox to differential, the term half shaft will be used)
- Differential and its output shafts (Transferring/Converting torque from the gearbox to the driveshafts and the rear wheels)
The half shafts are the center of all these problems. From the diagram below, the half shafts are made up of a shaft sitting inside a cup of grease basically. It is designed this way so that when the suspension compresses, it has some compliance to avoid destroying the half shafts/differential (Imagine gluing a twig to a single point, then at the other end pushing in/down on the twig… something will break!). This is essential for any Independent Rear Suspension setup.
20954
As the suspension compresses, the half shaft will move out of the cup at an angle. This drags the tip of the half shaft (a spider also known as) along the walls of the cup and over time will create a pit in the cup as shown in the 2nd diagram (the grease helps to avoid excessive friction). This is fine if you stay at the stock height but eventually, even at stock height (although this would take a while), the pit will grow large enough for the half shaft to “pop in” and “out” of which creates the vibration along the half shaft and into the rest of the drivetrain which then connects to the body (For example, grab a toy car – put the front wheels off the edge of a table then back onto the table, then off and on. Do this quickly enough and the car will somewhat “vibrate” like the half shaft moving in and out of the pit of the cup).
20955
When the car is lowered or even if the rear wheels are cambered heavily (due to the angle of hub to the LCAs and half shaft), this will only accentuate the problem. The half shaft sits even further out of the cup "presetting" the half shafts to vibrate... if that makes sense.
__________________________________________________ ____________________
“How can I tell if I need to fix this?”
While driving at below roughly 50km/hr, usually there usually won’t be any vibration (depending on how much you have lowered your car). Drive at 60km/hr+ and the suspension will compress under weight transfer and “pull” the half shafts out of the cup and back in rapidly as the suspension compresses and releases. This will make the whole rear drivetrain vibrate and it will be felt quite noticeably in the car body as the pit inside the cup grows larger with further driving.
“I’ve just lowered my car – do I need this now?”
No. A brand new AP1/AP2 could be lowered without any issues at all. Over thousands of KM’s however, a pit will grow in size and the vibrations will begin. Until then – enjoy driving without throwing money away :) Ultimately, it really depends on ride height/camber settings you have been running previously and how many KM’s the car has done. If the car has been dumped with -5 degrees of rear camber for some time, I’d prepare for one of the below fixes…
“How do I fix this?”
- Raise your car (This is the obvious one but I’m sure everybody would have lowered their car for a purpose – but this is a good option to use temporarily until one of the below fixes can be used)
- Driveshaft spacers (This lets the half shaft sit back INTO the cup as per standard height to wear away at the original spot. But as mentioned before, even at stock height with the half shaft seated in the cup properly – the pit will eventually grow large enough to create a vibration again.)
- Swapping the half shaft cups (This is the cheapest but more labour intensive alongside 1 piece spacers. Basically by swapping the cups from the left to the right side and vice versa, the pit that the half shaft would have created before, is now in a different position. So the half shaft will start wearing at a different spot in the cup….)
Note: You cannot swap the whole half shafts over as they are apparently different lengths, but swapping the whole half shaft over would be more labour intensive as you would need to re-torque the axle nuts to 220 ft/lb which is not a range most torque wrenches have unfortunately.
- Buy custom half shafts (This is the most expensive and labour intensive of all of the solutions. By making custom half shafts – you can extend the length of them for a lowered car to seat the half shaft inside the cup properly. BUT if you decide to raise the car, I would imagine this would cause strain on the suspension. For mechanics, this would easily be the #1 way to make money off unsuspecting clients…)
- Buy second half half shafts (This MIGHT be ok as long as they are not from a car with high KMs and I would highly recommend inspecting inside the cups otherwise you could end up at square 1 again. And like the last option, would be highly labour intensive)
“Is there a permanent fix?”
No, unless you re-design the whole rear drive train. The half shafts were designed to allow for suspension travel. If you don’t like this, I would suggest buying a car with a solid rear axle. FWD cars also work off the same principle so it’s nothing new, just normal wear and tear made worse by lowering.
Let me know if there are any questions and I’ll try to add to/fix the above to include anything else :)
Apologies if it's a bit wordy. I wrote this in a hurry...
Alternate explanation/pics here:
http://www.s2ki.com/s2000/topic/693173-driveshaft-spacer-necessary-for-lowered-car/
Note: I may be off with the correct technical terms/names of certain drivetrain components and would have simplified it all slightly to avoid confusion. So please bear in mind when reading! And please try to ignore the crappy diagrams…
The S2000 rear drivetrain works off a number of components.
- The hubs (Connected to the wheel, brakes and control arms)
- Half shafts/drive shafts (Connecting the hubs to the differential output shafts – to avoid confusion with the driveshaft from the gearbox to differential, the term half shaft will be used)
- Differential and its output shafts (Transferring/Converting torque from the gearbox to the driveshafts and the rear wheels)
The half shafts are the center of all these problems. From the diagram below, the half shafts are made up of a shaft sitting inside a cup of grease basically. It is designed this way so that when the suspension compresses, it has some compliance to avoid destroying the half shafts/differential (Imagine gluing a twig to a single point, then at the other end pushing in/down on the twig… something will break!). This is essential for any Independent Rear Suspension setup.
20954
As the suspension compresses, the half shaft will move out of the cup at an angle. This drags the tip of the half shaft (a spider also known as) along the walls of the cup and over time will create a pit in the cup as shown in the 2nd diagram (the grease helps to avoid excessive friction). This is fine if you stay at the stock height but eventually, even at stock height (although this would take a while), the pit will grow large enough for the half shaft to “pop in” and “out” of which creates the vibration along the half shaft and into the rest of the drivetrain which then connects to the body (For example, grab a toy car – put the front wheels off the edge of a table then back onto the table, then off and on. Do this quickly enough and the car will somewhat “vibrate” like the half shaft moving in and out of the pit of the cup).
20955
When the car is lowered or even if the rear wheels are cambered heavily (due to the angle of hub to the LCAs and half shaft), this will only accentuate the problem. The half shaft sits even further out of the cup "presetting" the half shafts to vibrate... if that makes sense.
__________________________________________________ ____________________
“How can I tell if I need to fix this?”
While driving at below roughly 50km/hr, usually there usually won’t be any vibration (depending on how much you have lowered your car). Drive at 60km/hr+ and the suspension will compress under weight transfer and “pull” the half shafts out of the cup and back in rapidly as the suspension compresses and releases. This will make the whole rear drivetrain vibrate and it will be felt quite noticeably in the car body as the pit inside the cup grows larger with further driving.
“I’ve just lowered my car – do I need this now?”
No. A brand new AP1/AP2 could be lowered without any issues at all. Over thousands of KM’s however, a pit will grow in size and the vibrations will begin. Until then – enjoy driving without throwing money away :) Ultimately, it really depends on ride height/camber settings you have been running previously and how many KM’s the car has done. If the car has been dumped with -5 degrees of rear camber for some time, I’d prepare for one of the below fixes…
“How do I fix this?”
- Raise your car (This is the obvious one but I’m sure everybody would have lowered their car for a purpose – but this is a good option to use temporarily until one of the below fixes can be used)
- Driveshaft spacers (This lets the half shaft sit back INTO the cup as per standard height to wear away at the original spot. But as mentioned before, even at stock height with the half shaft seated in the cup properly – the pit will eventually grow large enough to create a vibration again.)
- Swapping the half shaft cups (This is the cheapest but more labour intensive alongside 1 piece spacers. Basically by swapping the cups from the left to the right side and vice versa, the pit that the half shaft would have created before, is now in a different position. So the half shaft will start wearing at a different spot in the cup….)
Note: You cannot swap the whole half shafts over as they are apparently different lengths, but swapping the whole half shaft over would be more labour intensive as you would need to re-torque the axle nuts to 220 ft/lb which is not a range most torque wrenches have unfortunately.
- Buy custom half shafts (This is the most expensive and labour intensive of all of the solutions. By making custom half shafts – you can extend the length of them for a lowered car to seat the half shaft inside the cup properly. BUT if you decide to raise the car, I would imagine this would cause strain on the suspension. For mechanics, this would easily be the #1 way to make money off unsuspecting clients…)
- Buy second half half shafts (This MIGHT be ok as long as they are not from a car with high KMs and I would highly recommend inspecting inside the cups otherwise you could end up at square 1 again. And like the last option, would be highly labour intensive)
“Is there a permanent fix?”
No, unless you re-design the whole rear drive train. The half shafts were designed to allow for suspension travel. If you don’t like this, I would suggest buying a car with a solid rear axle. FWD cars also work off the same principle so it’s nothing new, just normal wear and tear made worse by lowering.
Let me know if there are any questions and I’ll try to add to/fix the above to include anything else :)
Apologies if it's a bit wordy. I wrote this in a hurry...
Alternate explanation/pics here:
http://www.s2ki.com/s2000/topic/693173-driveshaft-spacer-necessary-for-lowered-car/