Clunk from the rear on takeoff
#1
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Clunk from the rear on takeoff
Like the title says, a dull clunk as I let off the clutch.
I noticed it about a week or so ago.
I had time to get under the car and check it out today.
Turns out the pass side upper control arm slipped forward on both bushings, and it was contacting the brackets.
Here:
Close up of the bushings:
and
The driver's side looks normal:
Has this sort of thing ever happened to you guys?
Pretty interesting.
Anyway... I will just make/install delrin bushings for the upper control arm inboard mounts. Turns out the lathe is available on Wednesday.
I noticed it about a week or so ago.
I had time to get under the car and check it out today.
Turns out the pass side upper control arm slipped forward on both bushings, and it was contacting the brackets.
Here:
Close up of the bushings:
and
The driver's side looks normal:
Has this sort of thing ever happened to you guys?
Pretty interesting.
Anyway... I will just make/install delrin bushings for the upper control arm inboard mounts. Turns out the lathe is available on Wednesday.
#6
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Join Date: Jun 2009
Location: Istanbul, Turkey
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Problem solved.
I just went ahead and converted those bushings to Delrin, as well.
But, with one slight modification:
In a conventional bushing, the steel sleeve is trapped inside the bracket by the bolt, and it is stationary. The bonded rubber then flexes about that sleeve to facilitate control arm movement.
When you use poly or Delrin bushings, the sleeve is again held stationary by the bolt, and the bushing material then rotates around the sleeve.
Now, if you look at this pic, you'll see that there is a small gap on either side of the bushing. The steel sleeve protrudes from both sides by about 1.75 mm. That ensures the control arm does not rub on the bracket as it rotates.
If I were to follow that recipe, the control arm would move laterally and contact the bracket, making the whole job a moot effort.
On the other hand, cutting the Delrin exactly as wide as the bracket opening would mean binding.
I made the bushings so that there was a 1.75 mm gap on either end.
Then, we carefully made Delrin spacers that were 1.60 mm thick.
The idea was to create a "bearing" with the spacer, so the bushing would not bind.
I just went ahead and converted those bushings to Delrin, as well.
But, with one slight modification:
In a conventional bushing, the steel sleeve is trapped inside the bracket by the bolt, and it is stationary. The bonded rubber then flexes about that sleeve to facilitate control arm movement.
When you use poly or Delrin bushings, the sleeve is again held stationary by the bolt, and the bushing material then rotates around the sleeve.
Now, if you look at this pic, you'll see that there is a small gap on either side of the bushing. The steel sleeve protrudes from both sides by about 1.75 mm. That ensures the control arm does not rub on the bracket as it rotates.
If I were to follow that recipe, the control arm would move laterally and contact the bracket, making the whole job a moot effort.
On the other hand, cutting the Delrin exactly as wide as the bracket opening would mean binding.
I made the bushings so that there was a 1.75 mm gap on either end.
Then, we carefully made Delrin spacers that were 1.60 mm thick.
The idea was to create a "bearing" with the spacer, so the bushing would not bind.
#10
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The whole thing.
All three bolts are torqued to 50 pounds.
Control arm movement is smooth as butter.
I test drove the car, and it actually feels very good.
Next time I have a couple free days, I will tackle the front.
Oh, we made the bushings in two pieces, just like the rest of the bushings in the rear.
Details are here:
https://www.miataturbo.net/suspensio...rection-74732/
All three bolts are torqued to 50 pounds.
Control arm movement is smooth as butter.
I test drove the car, and it actually feels very good.
Next time I have a couple free days, I will tackle the front.
Oh, we made the bushings in two pieces, just like the rest of the bushings in the rear.
Details are here:
https://www.miataturbo.net/suspensio...rection-74732/
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