Stiff rings/ rigid collars?

[moose4]

On new cars, don't expect any felt benefits. On older clunky ones, there might be some placebo effect on unwanted noise reduction.
Compared 2 identical cars of about same age, usage & kms clocked(around 30k+)...1 w/ those tolerance-reducing rings installed early in its ownership. Both cars ran no differently on any surface at variable speeds. Guess they're both still too young to need them?

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Thanks for your input sir.

Feedback from other users would be highly appreciated