clunk on reverse

[markeyszoo]

When i reverse and apply full lock the car makes a clunk noise, quite loud. First time i thought i had backed into something.

Cannot see anything loose and it is no problem going forward, neither straight nor turning. 

Any ideas where to look?

[Mr Vlad]

Hi Mike. Does that clunk noise happen only on full lock and when turning both right and left?

[markeyszoo]

28 minutes ago, Mr Vlad said:

Hi Mike. Does that clunk noise happen only on full lock and when turning both right and left?

sometimes even at 3/4 lock and yes both ways

[H3XME]

This is a common thing. Funnily enough, only ever heard it on automatic cars. I think it's suspension related (at least that's what it sounds like) but I don't think I've ever seen anyone figure this out. Never caused any issues (it never got worse) but yeah, having had 3 manuals, none of them did that, but close friends with auto 250s say their do it and so did my dad's facelift 250. The clunk sounds almost like as if a spring re-seated itself in the cup, but that doesn't make sense considering it only ever happens at specific moment = reverse and steer. 

[markeyszoo]

9 hours ago, H3XME said:

This is a common thing. Funnily enough, only ever heard it on automatic cars. I think it's suspension related (at least that's what it sounds like) but I don't think I've ever seen anyone figure this out. Never caused any issues (it never got worse) but yeah, having had 3 manuals, none of them did that, but close friends with auto 250s say their do it and so did my dad's facelift 250. The clunk sounds almost like as if a spring re-seated itself in the cup, but that doesn't make sense considering it only ever happens at specific moment = reverse and steer. 

 

9 hours ago, H3XME said:

This is a common thing. Funnily enough, only ever heard it on automatic cars. I think it's suspension related (at least that's what it sounds like) but I don't think I've ever seen anyone figure this out. Never caused any issues (it never got worse) but yeah, having had 3 manuals, none of them did that, but close friends with auto 250s say their do it and so did my dad's facelift 250. The clunk sounds almost like as if a spring re-seated itself in the cup, but that doesn't make sense considering it only ever happens at specific moment = reverse and steer. 

 

[markeyszoo]

Yes it sounds mechanical like you say as though something was reseating itself. It sounds like a hammer hitting a bar.

[Mr Vlad]

I don't recall that noise in my beloved is250 therefore as a safety thing and piece of mind I'd take the car to Lexus or a Trusted garage for them to investigate. 

[markeyszoo]

Just found a topic by andynorman dated Dec 12 2009 "steering full lock clunk" which discusses same problem and describes tyres "stepping out"

[ColinBarber]

Tyre crabbing/skipping is a common issue that gets brought up here multiple times every winter (and on most other car forums too). Depending on the vehicle, tyre make/model, tyre pressure and ambient temperature you are likely to experience it when reversing (or sometimes going forward) on, or close to, steering lock.

It is related to the fact that the wheel geometry is compromised at, or near, full lock and doesn't completely follow Ackermann geometry so one of the wheels isn't turning around a shared single position that the differentials cannot compensate for.

https://en.wikipedia.org/wiki/Ackermann_steering_geometry

 

One of the more 'popular' threads on the subject: