Soft thumping
21 posts
• Page 1 of 2 • 1, 2
I noticed a soft thumping noise on the road the other day, at wheel speed on my +2. You could hardly hear it. It seemed the same on drive or coast, so I suspected the rear drive train.
I then jacked up the offside (drivers side uk) A frame to load the suspension, and spun the rear wheel. Sure, enough, there was a soft thump once per wheel revolution.
I now suspect the cv drive shaft, which has a few thou backlash and 60000 miles wear. Is there anything else that might be the cause?
Dave Chapman.
I then jacked up the offside (drivers side uk) A frame to load the suspension, and spun the rear wheel. Sure, enough, there was a soft thump once per wheel revolution.
I now suspect the cv drive shaft, which has a few thou backlash and 60000 miles wear. Is there anything else that might be the cause?
Dave Chapman.
- david.g.chapman
- Fourth Gear
- Posts: 813
- Joined: 26 Nov 2003
Check your tires. Could be tread separation.
Kiyoshi
Kiyoshi
**************
Life is more fun behind the wheel of a Lotus!
www.gglotus.org
www.gglotus.org/blog
Life is more fun behind the wheel of a Lotus!
www.gglotus.org
www.gglotus.org/blog
-
khamai - Third Gear
- Posts: 271
- Joined: 20 Oct 2003
FWIW I had a strange - wheel speed related noise on my +2 recently . I was on a short journey of only about a mile. During that journey my mind was going through all the terrible things it could be and how I was going to deal with them. When I arrived at my destination I found I had not released the handbrake properly !
The moral of the story is check the simple things first and "Don't Panic"
Good Luck
Baggy
The moral of the story is check the simple things first and "Don't Panic"
Good Luck
Baggy
- Baggy2
- Third Gear
- Posts: 278
- Joined: 05 Feb 2010
The wheel bearings on that side do have a lot of play - which you can see and feel when the wheel is rocked. I'll be changing them soon.
I'm not sure how you get a knock from bearings though. It's at the same point every revolution. I'm happy to be enlightened though!
The tyres are 7 years old and nearly worn out. There is no tread separation evident.
I'll disconnect the drive shaft and check the bearings again. Then if the bearings aren't knocking I'll clean out the drive shaft and examine it. Watch this space if I find anything interesting!
Dave Chapman.
I'm not sure how you get a knock from bearings though. It's at the same point every revolution. I'm happy to be enlightened though!
The tyres are 7 years old and nearly worn out. There is no tread separation evident.
I'll disconnect the drive shaft and check the bearings again. Then if the bearings aren't knocking I'll clean out the drive shaft and examine it. Watch this space if I find anything interesting!
Dave Chapman.
- david.g.chapman
- Fourth Gear
- Posts: 813
- Joined: 26 Nov 2003
Good news! I removed the drive shaft and spun the bearing - to reveal the same knock once per revolution. I can only imagine that a pothole or something has shocked the bearing and marked one of the races. Lummie!
As I mentioned, this bearing had a lot of play, and was only changed a couple of thousand miles ago. The bearings on the other side are fine.
I'll see if Sue M has any tomorrow.
Cheers,
Dave Chapman.
As I mentioned, this bearing had a lot of play, and was only changed a couple of thousand miles ago. The bearings on the other side are fine.
I'll see if Sue M has any tomorrow.
Cheers,
Dave Chapman.
- david.g.chapman
- Fourth Gear
- Posts: 813
- Joined: 26 Nov 2003
Well if it “thumps” while jacked up then you can rule out tyres/internal band separation as the tyre is not in contact with anything …….
Play in rear bearing sounds ominous as there is no adjustment on the roller bearing (unlike the front taper bearings) …….the rears do have a habit of wearing the strut housing but unless the bearing is “tilting or rocking” in the housing I don’t really see how bearings would make a “thumping noise” but the play needs investigating.
Play in rear bearing sounds ominous as there is no adjustment on the roller bearing (unlike the front taper bearings) …….the rears do have a habit of wearing the strut housing but unless the bearing is “tilting or rocking” in the housing I don’t really see how bearings would make a “thumping noise” but the play needs investigating.
Brian
64 S2 Roadster
72 Sprint FHC
64 S2 Roadster
72 Sprint FHC
-
types26/36 - Coveted Fifth Gear
- Posts: 3889
- Joined: 11 Sep 2003
Yes, I've never had a knocking bearing before - I thought they whined or rumbled when worn.
When I've got the bearings out I'll post a picture of anything interesting.....
Dave.
When I've got the bearings out I'll post a picture of anything interesting.....
Dave.
- david.g.chapman
- Fourth Gear
- Posts: 813
- Joined: 26 Nov 2003
I isolated the "thumping" to the wheel bearings and hub shaft assembly, as mentioned earlier.
I have now removed the shaft leaving the inner bearing on the shaft, and I've driven out the outer bearing. Both bearings spin without knocking now the bits are out of the car, which deepens the mystery. It sounded for all the world like something was hitting something else once per revolution, but I could not see anything with the shaft, and everything else assembled on the car.
I now have the cv drive shaft out and just to be sure, have spun both ends of the drive shaft in circles with the other end clamped in a vice. No noises.
I have also rotated the diff output shaft. Again, just a normal whirr from the diff. The output bearing there is locked in place and not spinning.
I'm not happy with the condition of the shaft (some evidence of spinning in the past), so I've ordered a new one from TTR, long with a bearing set. I'll post again when I've finished.
Dave Chapman.
I have now removed the shaft leaving the inner bearing on the shaft, and I've driven out the outer bearing. Both bearings spin without knocking now the bits are out of the car, which deepens the mystery. It sounded for all the world like something was hitting something else once per revolution, but I could not see anything with the shaft, and everything else assembled on the car.
I now have the cv drive shaft out and just to be sure, have spun both ends of the drive shaft in circles with the other end clamped in a vice. No noises.
I have also rotated the diff output shaft. Again, just a normal whirr from the diff. The output bearing there is locked in place and not spinning.
I'm not happy with the condition of the shaft (some evidence of spinning in the past), so I've ordered a new one from TTR, long with a bearing set. I'll post again when I've finished.
Dave Chapman.
- david.g.chapman
- Fourth Gear
- Posts: 813
- Joined: 26 Nov 2003
Some suggestions, based on both my industrial and personal Elan and formula car experience.
Good on you to take this seriously. I suggest the following to take this a little deeper:
Mic the diameters of the bearings and the diameters of the bearing bores in the housings. Measure in 8 places in the bores.
Cut the bearings open with a cutoff wheel. Cut the ball cage. Look at the bearing balls, the inner race and outer race. I have found deep chunks out of the inner and outer race surfaces. Other times some weird noises due to ball skid. Once with multiple circumferential lines on the balls called "ball skid".
Remove your CVs and inspect the bearing surfaces. On my FF I found metal loss in the races of the outer shell.
Lastly, to those of you who detect this soft thumping noise on a car that has donuts, carefully inspect your donuts for fractures in the donut or loose donut bolts. My first experience with the Lotus West Tech Manual after I bought my Elan in 1979, was finding the brief article called "Donut Rumble". That article saved me from a huge failure. Either the donut has already failed or a loose bolt is about to suffer a fatigue failure.
Good on you to take this seriously. I suggest the following to take this a little deeper:
Mic the diameters of the bearings and the diameters of the bearing bores in the housings. Measure in 8 places in the bores.
Cut the bearings open with a cutoff wheel. Cut the ball cage. Look at the bearing balls, the inner race and outer race. I have found deep chunks out of the inner and outer race surfaces. Other times some weird noises due to ball skid. Once with multiple circumferential lines on the balls called "ball skid".
Remove your CVs and inspect the bearing surfaces. On my FF I found metal loss in the races of the outer shell.
Lastly, to those of you who detect this soft thumping noise on a car that has donuts, carefully inspect your donuts for fractures in the donut or loose donut bolts. My first experience with the Lotus West Tech Manual after I bought my Elan in 1979, was finding the brief article called "Donut Rumble". That article saved me from a huge failure. Either the donut has already failed or a loose bolt is about to suffer a fatigue failure.
There is no cure for Lotus, only treatment.
-
StressCraxx - Coveted Fifth Gear
- Posts: 1451
- Joined: 26 Sep 2003
Dave,
If you don’t feel confident to follow the advice from StressCraxx about doing you own bearing failure analysis all the reputable bearing companies offer a failure analysis service (I should say they did before I retired). However this service is expensive.
Hope this helps,
Richard Hawkins
If you don’t feel confident to follow the advice from StressCraxx about doing you own bearing failure analysis all the reputable bearing companies offer a failure analysis service (I should say they did before I retired). However this service is expensive.
Hope this helps,
Richard Hawkins
- RichardHawkins
- Coveted Fifth Gear
- Posts: 1265
- Joined: 05 Jul 2008
Most bearing companies provide on line information on bearing failures.. I like others here have done bearing failure analysis for 50 years in my mechanical engineering career and it is not that hard. At times I have used various metallurgical and bearing companies to assist in specialist testing but that is rare and unusual cases.
Post potos of the bearing internal balls and races if you supect them of the thumping and I am sure you can get a good analysis from the group here. Thumping typicall relates more to the mounting of components rather than the bearings internals.
cheers
Rohan
Post potos of the bearing internal balls and races if you supect them of the thumping and I am sure you can get a good analysis from the group here. Thumping typicall relates more to the mounting of components rather than the bearings internals.
cheers
Rohan
-
rgh0 - Coveted Fifth Gear
- Posts: 8962
- Joined: 22 Sep 2003
hi Dave,
it seems strange the bearings only lasted 2,000 miles.
when you assemble with new bearings be care of what assembly procedure that is used.
Alan
it seems strange the bearings only lasted 2,000 miles.
when you assemble with new bearings be care of what assembly procedure that is used.
Alan
Alan.b Brittany 1972 elan sprint fhc Lagoon Blue 0460E
- alan.barker
- Coveted Fifth Gear
- Posts: 3821
- Joined: 06 Dec 2008
21 posts
• Page 1 of 2 • 1, 2
Total Online:
Users browsing this forum: No registered users and 5 guests