Jon Panayi Posted October 21, 2020 Share Posted October 21, 2020 (edited) - Knock knock - Who's there? - My front nearside suspension when manoeuvring at low speed... So I have pretty much had the front end of my 06 Cayman S rebuilt. Spec is: Eibach LCAs New subframe (I had a crack in mine... fun times!) New stock Porsche suspension top mounts New PASM shocks New drop links The only thing I've not changed are the springs. The car is on 115k miles, so I guess I might have an issue with these. Basically, at slow speed, on almost full right lock, there is a knocking noise from my front nearside. Any ideas what may be the issue, before I give a garage more of my money 😊 Edited October 21, 2020 by Jon Panayi Link to comment Share on other sites More sharing options...
Founder Beanoir™ Posted October 21, 2020 Founder Share Posted October 21, 2020 What about your coffin arms? The knocking at low speed is normally the sign of a worn bush in the arm. ARB bushes is another possible suspect Link to comment Share on other sites More sharing options...
briggy Posted October 23, 2020 Share Posted October 23, 2020 It's definitely a knocking noise? It could be the Ackerman effect on your tyres - on full lock, the inner edge of your tyre is rotating at a different speed to the outer edge as they have different distances to travel. The inner tread blocks have to "skip" in order to keep up, which you'll feel as feedback through the steering and also hear. More noticeable on tyres with worn treads as blocks on new tyres with deeper treads are able to stretch instead of skipping. Also only noticeable at low speeds. Cheers, Bryan Link to comment Share on other sites More sharing options...
TritonII Posted October 23, 2020 Share Posted October 23, 2020 3 hours ago, briggy said: It's definitely a knocking noise? It could be the Ackerman effect on your tyres - on full lock, the inner edge of your tyre is rotating at a different speed to the outer edge as they have different distances to travel. The inner tread blocks have to "skip" in order to keep up, which you'll feel as feedback through the steering and also hear. More noticeable on tyres with worn treads as blocks on new tyres with deeper treads are able to stretch instead of skipping. Also only noticeable at low speeds. Cheers, Bryan That's interesting, never heard of that. My girlfriend's 911 and previously her Cayman, both 19 plates direct from OPC on new tyres, 'knock' and appear to be catching something at low speed on full lock, is this the effect that you describe? I found it hard to comprehend how a new designed premium car could be in production with such a fault and also couldn't see any evidence of marking on the tyres. Link to comment Share on other sites More sharing options...
Founder Beanoir™ Posted October 23, 2020 Founder Share Posted October 23, 2020 1 hour ago, TritonII said: That's interesting, never heard of that. My girlfriend's 911 and previously her Cayman, both 19 plates direct from OPC on new tyres, 'knock' and appear to be catching something at low speed on full lock, is this the effect that you describe? I found it hard to comprehend how a new designed premium car could be in production with such a fault and also couldn't see any evidence of marking on the tyres. if it is as described above, yes the ‘akerman’ effect can be a thing and it’s generally only noticeable at very slow speed, manoeuvring and reversing. It’s generally a thing that affects Porsches more often because there is no weight over the front wheels so they will skip. If it’s a one of ‘click’ or ‘clunk’ then that’s probably not akerman related. Link to comment Share on other sites More sharing options...
TritonII Posted October 23, 2020 Share Posted October 23, 2020 28 minutes ago, Beanoir™ said: if it is as described above, yes the ‘akerman’ effect can be a thing and it’s generally only noticeable at very slow speed, manoeuvring and reversing. It’s generally a thing that affects Porsches more often because there is no weight over the front wheels so they will skip. If it’s a one of ‘click’ or ‘clunk’ then that’s probably not akerman related. Thanks Nick @Beanoir™, it's definitely not a one off click and most pronounced on full lock when reversing. I used to trial off road land rovers and those fitted with over-wide knobbly off road tyres would catch the treads on the radius arms when on full lock, it sounds like that, hence why I was bemused how it could be on a modern Porsche. The effect you describes would explain the noise and judder felt through the car without there being a design fault. Link to comment Share on other sites More sharing options...
briggy Posted October 23, 2020 Share Posted October 23, 2020 It's not really in the design of the car itself. The wider the tyres, the more pronounced it is. I've had it on other non-Porsche cars too. Cheers, Bryan Link to comment Share on other sites More sharing options...
Jon Panayi Posted October 26, 2020 Author Share Posted October 26, 2020 Sorry, I forgot to say that the coffin arms are new Eibach adjustable jobbies. I also have new suspension top mounts. My gut feeling is, either something needs a little tighten or else the ARB bushes need looking at? Link to comment Share on other sites More sharing options...
Founder Beanoir™ Posted October 26, 2020 Founder Share Posted October 26, 2020 Try spraying some grease in and around the ARB bushes. If it stops the noise you'll know the bushes need seeing to. That said, they're cheap and very easy to replace anyway. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now