Your math looks to be correct, which points to an rotating assembly at the same rpm as the wheels. This could be tires, wheels or drive shafts. It is not likely to be the prop shaft as it would be spinning 2.8 times faster than the wheels, so will have a correspondingly higher frequency if it is the cause of the vibration.
Vibration diagnosis via sensor data
- Thread starter JHZR2
- Start date
- Status
It doesn't matter if its spinning 2.8 or 28 times more if it vibrates at a consistent speed and rpm. Where do you get the 2.8 number from? That depends on the gear ratio and tire size.
When the transmission shifts the drive shaft and cv axles rpm remains constant if the same speed is maintained only the engine and transmission internal rpm changes.
When the transmission shifts the drive shaft and cv axles rpm remains constant if the same speed is maintained only the engine and transmission internal rpm changes.
Originally Posted by Trav
It doesn't matter if its spinning 2.8 or 28 times more if it vibrates at a consistent speed and rpm. Where do you get the 2.8 number from? That depends on the gear ratio and tire size.
When the transmission shifts the drive shaft and cv axles rpm remains constant if the same speed is maintained only the engine and transmission internal rpm changes.
The 2.8 is from the JHZR2's final drive ratio, 2.82:1 to be exact. The frequency with the highest vibration amplitude at 60 mph is 13.6Hz captured by his phone accelerometer, which corresponds closely to the rotational speed of his particular wheel size (also given in his post) at 60 mph. This points to an imbalance that occurs at 13.6 times per second, assuming it is a single imbalance in the rotating system. If the prop shaft has an imbalance, it would be at a different frequency as the prop shaft rotates 2.82 times faster than the wheels.
The key is the 13.6Hz frequency, as it corresponds to an imbalance at wheel rpm at 60 mph.
It doesn't matter if its spinning 2.8 or 28 times more if it vibrates at a consistent speed and rpm. Where do you get the 2.8 number from? That depends on the gear ratio and tire size.
When the transmission shifts the drive shaft and cv axles rpm remains constant if the same speed is maintained only the engine and transmission internal rpm changes.
The 2.8 is from the JHZR2's final drive ratio, 2.82:1 to be exact. The frequency with the highest vibration amplitude at 60 mph is 13.6Hz captured by his phone accelerometer, which corresponds closely to the rotational speed of his particular wheel size (also given in his post) at 60 mph. This points to an imbalance that occurs at 13.6 times per second, assuming it is a single imbalance in the rotating system. If the prop shaft has an imbalance, it would be at a different frequency as the prop shaft rotates 2.82 times faster than the wheels.
The key is the 13.6Hz frequency, as it corresponds to an imbalance at wheel rpm at 60 mph.
I'll take your word for it but I cant see how the phone app is accurate, I need to look into it.
Originally Posted by chrome
The key is the 13.6Hz frequency, as it corresponds to an imbalance at wheel rpm at 60 mph.
Yep, which is why I mentioned the wheel run-out and tire uniformity.
Not directed at you 'chrome', but rather just reinforcing what you said.
The key is the 13.6Hz frequency, as it corresponds to an imbalance at wheel rpm at 60 mph.
Yep, which is why I mentioned the wheel run-out and tire uniformity.
Not directed at you 'chrome', but rather just reinforcing what you said.
JHZR2
Staff member
Well it was a wheel and tire thing. All wheels and tires to be more specific. Took it to a Goodyear tire shop and they roadforce balanced it. They took a relatively large amount of weight, 8, 13, 14 and 20lb as I recall, on a Hunter machine.
Driving at 70 mph is now just wonderful.
All in the tires. Roadforce reduced the amount of weight substantially too.
Driving at 70 mph is now just wonderful.
All in the tires. Roadforce reduced the amount of weight substantially too.
Its unbelievable they cant even balance a set of tires. Glad that worked out for you.
I'm glad you found someone competent to get it sorted.
- Status
