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 Post subject: seeking opinions
PostPosted: Mon Aug 14, 2017 10:58 am 
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Hi guys, i have posted this in the PCGB forum but will ask here too, just to seek views from all sources...

Morning all

I have had an issue on the car for some time now that in recent months has been getting worse and I'm stumped as to which of a number of things that it could be. The symptom is basically a very rough ride which is very dependent on the road surface. A perfectly flat new road and it's hardly noticeable if at all, add a slight worsening of the surface and the car feels like it's going over tiny cobble stones, the worse the surface the worse the effect. At times this feels too bad to drive and has me a little paranoid about the possible causes. I have ruled out any engine issues, the feeling is there just the same with the car rolling at any speed with either the clutch engaged or the transmission put in neutral. I have considered rear wheel bearings and torque tube bearings, not because I think it's these, as I said there are no related sounds but purely for the fact that these parts are still original on a chassis that's done over 200k miles. These days I'm not in a position to just say...'right let's change the lot' those days are long gone. About two years ago I had thought that there may have been a slight wheel bearing sound on the rear left but this quickly disappeared so ruled this out. Everything that I have read on the web re wheel bearings and torque tube bearings on 944's states the noises associated with failure, I haven't found anything to say these items have failed with no noise. A few months ago while my son had the car on the ramp I did ask him to check the rear bearings due to this rough feeling, a bit like a rumble but again no sound and no feeling through the steering, he could feel no play or any sound while checking said bearings. Alas, I didn't ask him to take a look at the torque tube, I'll try to address that asap. Now my paranoia is making me think that I should stop using the car until I can get this sorted, I do not need a catastrophic disaster from a wheel or tube bearing. There is another possibility, well probably more hence why I'm seeking other opinions but it could also be the tyres (this is my son's view), the front right has worn unevenly badly due to me taking so long to get the geometry sorted after the rebuild, the reason that I'm not convince it's the tyres is the ride feels far too rough, more so than anything that I've experienced before
Everything that I have read on the web re wheel bearings and torque tube bearings on 944's states the noises associated with failure, I haven't found anything to say these items have failed with no noise. A few months ago while my son had the car on the ramp I did ask him to check the rear bearings due to this rough feeling, a bit like a rumble but again no sound and no feeling through the steering, he could feel no play or any sound while checking said bearings. Alas, I didn't ask him to take a look at the torque tube, I'll try to address that asap. Now my paranoia is making me think that I should stop using the car until I can get this sorted, I do not need a catastrophic disaster from a wheel or tube bearing. There is another possibility, well probably more hence why I'm seeking other opinions but it could also be the tyres (this is my son's view), the front right has worn unevenly badly due to me taking so long to get the geometry sorted after the rebuild, the reason that I'm not convinced it's the tyres is the ride feels far too rough, more so than anything that I've experienced before and I'm getting zero feedback through the steering wheel?
Due to this if I was going to take a guess as to what part of the car it's coming from I would have to chose the rear just because I'm getting nothing through the steering but the feeling felt does not seem to be coming from any one part of the chassis, it's the whole car...if that makes sense? This could and most probably is saying 'it's the tyre's but I don't want to spend money on something that I'm not sure about...so guy's, what do you think, is it one of the parts I've suggested or something else, perhaps related to the suspension?

Look forward to reading your views

Pete

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 Post subject: Re: seeking opinions
PostPosted: Mon Aug 14, 2017 11:19 am 
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I have had my 968 for 18 months.

When I first drove it I was surprised by the tyre noise in the car and I still find it a bit irritating but I am convinced it is just that, tyre noise. The car is delightful to drive in every other way and checks out well in any inspection. Change the tyres and then try it, or borrow wheels and tyres from another car and try it. Go in other cars and compare the noise in them.

I did post on this site just afer I bought the car and was advised that what I was hearing was nothing abnormal.

David

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 Post subject: Re: seeking opinions
PostPosted: Mon Aug 14, 2017 11:25 am 
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Hi David

thank's for your reply, I should have said here (I'm better known in PCGB circles) that I know the car very well having owned it for over 18 years. During that time I have experienced just about everything possible on a 944, this is new, as stated there is no associated noise with this issue, it's purely what can be felt through the chassis, which at times is extreme, no abnormal feeling through the steering wheel either. I had thought about the possibility of trying another set of wheels, I used to have a spare set but alas, no longer.

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Pete

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 Post subject: Re: seeking opinions
PostPosted: Mon Aug 14, 2017 11:48 am 
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Hi

I would book it in at Centre Gravity, they will fathom out what is going on.

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 Post subject: Re: seeking opinions
PostPosted: Mon Aug 14, 2017 12:01 pm 
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Thanks, Sean..alas they are a bit far from me, plus I'd like to remove any possible suspension, bearing, tyre issues before spending money on alignment...

Many thanks

Pete

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 Post subject: Re: seeking opinions
PostPosted: Mon Aug 14, 2017 12:11 pm 
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They will identify suspension and other issues, they have a test for everything.

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 Post subject: Re: seeking opinions
PostPosted: Mon Aug 14, 2017 12:18 pm 
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Very possible Sean but they are a long way from me and I have got to the stage where I don't want to drive the car too far in case I have a catastrophic failure of a bearing...I need to rule certain things out first...The car had a full alignment about 6 months ago due to uneven tyre wear but I know why that occured..

Pete

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 Post subject: Re: seeking opinions
PostPosted: Mon Aug 14, 2017 12:29 pm 
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Understood

Let's start at the beginning.

Torque Tubes chatter, the bearings get dry over time. Very rare for these to actually fail and when mine started to chatter there was no issue with regards to road noise.

What size wheels are you running? If you are on 18" do you have the 968 Castor Mounts?

Sounds obvious but have you played with the tyre pressures.

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 Post subject: Re: seeking opinions
PostPosted: Mon Aug 14, 2017 1:11 pm 
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Torque chatter is pretty common on these cars, mine has been doing that since, well I can't remember when it hasn't?, so that's 18 years....I'm not a big wheel fan, she has the standard 16" Deep dish teledials fitted from new, I do have the 968 suspension mounts already fitted, along with koni adjustables all round, these have been on the car for some time....
Yes I have played with tyre pressures, now back where they belong and where I have kept them since ownership at 36psi all round..

As I said there is no noise, well not that I can detect just this very rough feeling when driving, I have been trying to track this for a while.. the engine had a few small issues which I think masked some of this and naturally focused my mind more than any possible chassis issues. I can't get it on the ramp for a while or I'd do a full check for anything loose but I don't think it's that as the handling is fine, just this very rough ride which at times is like driving over a very old cobbled stone road, that's the only way that I can describe it although there's no bumping motion that you would get on such a road?

Pete

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 Post subject: Re: seeking opinions
PostPosted: Mon Aug 14, 2017 6:27 pm 
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Sounds to me like something is broken, loose or worn out in the suspension or even the gearbox mount (mine fell apart after a Knockhill trackday) If you are getting a cyclic vibration after going over a road imperfection and it feels like the rear, first choice is the shocks and shock mounts. The oscillations are not being damped, so if the shocks are ok the mounts may have a fracture. A similar problem on the front of the 993 was a loose nut on the front struts. Tricky to detect as I have RS monoballs with a screw on dust cap (torqued to 180lbs /ft.) and lock-tight. I cut the top of the dust cap of to get at the nut a la works cars.

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 Post subject: Re: seeking opinions
PostPosted: Mon Aug 14, 2017 8:21 pm 
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don't think your to far from me, you are welcome to swap to my genuine 17 cup 1 for a test, as I know you don't like big wheels,

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 Post subject: Re: seeking opinions
PostPosted: Mon Aug 14, 2017 9:09 pm 
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Its probably not the torque tube bearings - they sound like a coffee grinder when tired. I changed mine. When I took them out I couldn't feel any play in them at all. Also it will not affect the ride. Its bolted to the engine and gearbox - it dose not really move much whilst driving and isn't involved in the ride/handling.

First thing don't rely on an MOT inspection to verify condition of any suspension parts - there is a lot of lattitude in what is or isn't acceptable.

The wheel bearings will potentially give a rumbling noise when cornering if bad and /or a vibration in the steering wheel at high speed that will go away if you go faster. If you find the braking point at the pedal is varying that would also indicate worn bearings. If really bad a whining noise as you go along but they would have to be really knackered to do that.

I would start with the front suspension and look for play in all the bushes on the wishbones and anti roll bar. Check the suspension and steering balljoints very carefully. There should be no play at all - preferably quite stiff to move by hand. Separate the joints from the chassis parts to check them. Then investigate the suspension top mounts at the top of the shock absorber/spring assembly. These wear and will create movement as you drive along. You will need to disassemble to check them out - need a spring compressor.

If no luck there start at the back end, shock absorbers - take them off and checkbushes etc, then start pulling and tugging all the swing arms etc. Then check the various suspension mounting points. They are rubber bonded and can break up so you can get metal to metal contact.


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 Post subject: Re: seeking opinions
PostPosted: Mon Aug 14, 2017 10:47 pm 
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Thanks for the input guys....

I don't think that anything is broken..I won't rule it out completely but I have no handling issues and as stated no unusual noises coming from anywhere, I just have the rumbling feeling (only way I can describe it) that changes according to road surface....a new flat road and the ride is relatively smooth, on a bad surface the ride gets harsher, the worse the surface, the worse the ride gets to nearly an undrivable condition. Putting aside this issue the car is performing very well, the engine is smooth and very powerful, built by yours truly and doesn't miss a beat, even when I accidentally hit over 7100 rpm yesterday...lol
Having listened to views both here and on PCGB I am now leaning towards bad tyres/wheels scenario, I hope so as this will involve zero money to check as I can get my son to rebalance the wheels and check if I have a damaged wheel due to pot hole incursions.
My current plan is to get the car up on the ramp at my son's work, while he does the wheel balancing I can check bearings on wheels and torque tube, I will also take a close look for signs of any broken components, I'm not expecting to find any due to what I said about handling but you never know...best to be sure...

Thanks for the offer of wheels to try Waylander, I had considered trying a good set but if so would probably be best to try 'like for like' although granted that different tyres can make a difference it would be best to try wheels the same as on the car.

Thanks, guys, all very helpful..

Pete

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 Post subject: Re: seeking opinions
PostPosted: Tue Aug 15, 2017 7:47 pm 
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Pete thinking about blocked tyres, I had an old car when I lived in Cyprus that had a dodgy tyre. I went to the garage and even though the guy spoke no English he deduced what the problem was, basically he got a straight edge and put it across the tyre treads until he found the problem, one tyre had raised tread across the centre that with the visual aid it become very obvious. tyre changed problem went away.


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 Post subject: Re: seeking opinions
PostPosted: Tue Aug 15, 2017 7:53 pm 
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944-Scott wrote:
Pete thinking about blocked tyres, I had an old car when I lived in Cyprus that had a dodgy tyre. I went to the garage and even though the guy spoke no English he deduced what the problem was, basically he got a straight edge and put it across the tyre treads until he found the problem, one tyre had raised tread across the centre that with the visual aid it become very obvious. tyre changed problem went away.



Thank's Scott...the tyres are my prime suspect just now, your and others information is supporting this possibility, the tyre's aren't old but they are worn unevenly, well certainly on the front right due to the tracking issue noted before. What throws me a little is that I've had badly worn tyres before, I've had broken suspension components before but I've not had this particular feeling through the chassis, it may turn out to be a mixture of things? let's hope nothing expensive..:)

cheers

Pete

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