25-35 MPH - Wobble/Bounce.

I would of thought a DTI on the disc/wheel would be one of the first things to check,especially now. Replacement brake discs should always be checked as fitted true with a DTI. Can't think that anyone does but no measuring = no warranty pay out when they distort... Learnt lesson the hard way :( Anyhow,it's a pretty straight forward job and could easily prove it is a tyre as opposed to tyre,flange,bearing,knuckle,etc,etc.
 
While not checked with a micrometer, the disc showed no visual signs if movement horizontally or vertically. It looked almost stationary at both idle and 30mph wheel speeds. Movement was only seen at the tyre/possibly wheel rim vertically but couldn't be sure on the latter as reflections made it difficult.
 
I think you ought to put a dial gauge on the hub spigot! Thats the interface that will effect rotational runout!

Make sure you mount the gauge from a stable part of the assembly.
 
Thanks guys, I think once the weather improves I might have it back to Darren Wood to check with gauges as you suggest. For now, as I know its nothing serious, I'll live with the odd time I can sense it. Wouldn't surprise me if its pot hold damage at all, the roads here in Manchester are beyond bad with many stretches having 2" deep gullies and ribs of tarmac missing. Local council is a complete joke in relation to this, telling me repairs have been done when they haven't etc.. Even getting to the point where I'll be launching a proper appeal campaign as everyone is fed up with it. The road I live on, I have to drive at less than 10mph its that bad. Should have gone with an X5!

This is just the last few feet of my road.. its like this for at least 50 feet, and since I took the photos ages ago, its been patched again and again and each patch in just weeks has failed scattering debris and making more holes... joke. At least I know about these and I can go slowly, some roads just creep up on you and you just cringe waiting for the impact. Completely unacceptable. I wish I had a recent pic as its 10x worse than these pics atm.

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So I've not had time to get the car back in for this to be looked at, but what I do know is that having replaced the wheels and now the Michelin PSS tyre going on that its actually a bit more detectable. This morning, travelling to work on the roads I can just about feel it on, those roads were wet today and it was even more noticeable. Rather than a bounce, it felt like I was rapidly pumping the brake pedal ever so slightly. So this is now making me wonder if it might be an ABS or brake Disc issue with something catching or binding. Driving me nuts, the last thing to really sort on this car before I've got it just the way I want it. Time to knock on an indy's door now I think, now its a bit easier to reproduce. Its nothing major, most people can't detect it, but as I drive it every day, I can...
 
Disconnect an abs sensor wire. That will disarm the abs system in total then try it. I would imagine the abs sensors detect the signal from the hub bearing assembly. Reconnect the sensor when finished and the abs will reset itself. Least that will prove the abs is faulty or not.
 
Car is in for a 4 wheel alignment Friday. They're an mot garage too so I'm going to get it on the rollers and let them see if they can reproduce and therefore diagnose what it could be.

To my mind it's a damaged bearing, brakes or something to do with the transmission that was replaced.

I'll look into the abs thing too thanks.
 
Highly unlikely it will be found on an mot roller brake tester. They only run at 4 mph and you don't get that accurate a reading for imbalance,judder or binding. They have to have a significant fault to give an mot failure reading, something a little more than you seem to be experiencing? Making sure all is pointing the correct way is certainly a good place to start though. Good luck.
 
Highly unlikely it will be found on an mot roller brake tester. They only run at 4 mph and you don't get that accurate a reading for imbalance,judder or binding. They have to have a significant fault to give an mot failure reading, something a little more than you seem to be experiencing? Making sure all is pointing the correct way is certainly a good place to start though. Good luck.
 
4mph? I didn't know that so I guess I'll leave it to them to suggest then..

So subtle and so intermittent I'm guessing it could be something never found and something others might not even pick up on..
 
So I'm down £120 for a 4 wheel setup but I have to say its at least corrected some steering pull. The guys at Drury lane autos were really top notch and we had a good old chat about the wobble. Sadly without any immediately easy answer. Going to see over the next few days if I can feel the bounce again. Settings were out but not hugely.

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So having had this to two more specialists given I've not been able to resolve it, they can't find anything wrong with the car at all. ... One of these specialists was way out of Manchester on a quiet, flat good quality road with hardly any traffic, a perfect environment to test this. So, I took the car at various throttle positions from 0 to 40+. Again and again. Not once did it show this 30mph wobble. Totally perplexed I remembered that on a recent trip to Birmingham NEC, when leaving the event, on a very smooth road, I could feel a bump bump bump from the back wheels.. and it suddenly clicked. Given the very short suspension travel, the dynamic suspension that goes almost solid when accelerating to reduce squat and the very very thin amount of rubber between the wheel and road, this is likely the tyres after all.

I think what's happening is that the tyres are getting warm/hot. Then I park up, the tyres cool, with a very slight flat spot where its parked. I then set off and get this thud thud thud or slight bump bump bump. Clearly this was happening with the RFTs just as it is now with the M PSS. The reason I came to this conclusion is because if when doing my first few miles I feel this bumping vs having the tyres fully warmed up on smooth roads and I can't feel it, the only thing that could possibly have changed, given all the mechanicals seem fine, is the tyre. It would also explain the slight squirming I feel from time to time which is the tyres, possibly one having rotated slightly differently to the other due to bumps now hitting their respective flat spots slightly apart.

I could be wrong... and it sounds a bit far fetched but this is probably it and there's not much I can do about it. I'm guessing most people won't or don't notice it because its so slight, but I know my car well and am a bit of a perfectionist. Its not something I've ever felt with another car because I've never had such low profile tyres. It would probably be much less pronounced on 18" and likely hardly felt at all on 17".

So I guess its something I'll have to live with....
 
Maniac said:
So having had this to two more specialists given I've not been able to resolve it, they can't find anything wrong with the car at all. ... One of these specialists was way out of Manchester on a quiet, flat good quality road with hardly any traffic, a perfect environment to test this. So, I took the car at various throttle positions from 0 to 40+. Again and again. Not once did it show this 30mph wobble. Totally perplexed I remembered that on a recent trip to Birmingham NEC, when leaving the event, on a very smooth road, I could feel a bump bump bump from the back wheels.. and it suddenly clicked. Given the very short suspension travel, the dynamic suspension that goes almost solid when accelerating to reduce squat and the very very thin amount of rubber between the wheel and road, this is likely the tyres after all.

I think what's happening is that the tyres are getting warm/hot. Then I park up, the tyres cool, with a very slight flat spot where its parked. I then set off and get this thud thud thud or slight bump bump bump. Clearly this was happening with the RFTs just as it is now with the M PSS. The reason I came to this conclusion is because if when doing my first few miles I feel this bumping vs having the tyres fully warmed up on smooth roads and I can't feel it, the only thing that could possibly have changed, given all the mechanicals seem fine, is the tyre. It would also explain the slight squirming I feel from time to time which is the tyres, possibly one having rotated slightly differently to the other due to bumps now hitting their respective flat spots slightly apart.

I could be wrong... and it sounds a bit far fetched but this is probably it and there's not much I can do about it. I'm guessing most people won't or don't notice it because its so slight, but I know my car well and am a bit of a perfectionist. Its not something I've ever felt with another car because I've never had such low profile tyres. It would probably be much less pronounced on 18" and likely hardly felt at all on 17".

So I guess its something I'll have to live with....
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Good assumption but I find it very hard to believe thats the cause to be honest, I doub't tyres ever flat spot regardless of temperature unless the car has been sitting in storage for a long period. I would imagine alot more people would notice it otherwise :?

Tim.
 
Well given no one can find anything wrong and that after a long run then it's sat for hours then set off and there's a pronounced tyre flat spot sensation, it's the only explanation I can find.
 
Maniac said:
Well given no one can find anything wrong and that after a long run then it's sat for hours then set off and there's a pronounced tyre flat spot sensation, it's the only explanation I can find.
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Have you tried googling for tyre flatspots? or spoken to someone in the know on tyres? worth exploring. I agree its possible plausable explanation but just never heard of tyres flatspotting due to temperature to cause a noticeable sensation.

Tim.
 
Flatspot does sound possible to me, you seem to have covered everything else by now. Can you jack it up, or park on some folded up blankets or whatever in the garage after a run, and see if it still does it the following day ?
 
Could it be shock aborbers. My non adapting 23i was giving a bumping noise on undulating road surface. Fitted two new rear dampers and bumping 95% gone and would easily wheel spin on grit. The originals at 44k seemed to go soft, they hadn't failed as such, no leaks.
Seemed to be set off at around 40mph.
Also the trailing link on the rears have anti vibration mounts.
Would be interesting to know how they work.
This was suggested by someone i know that works for Jag/LandRover.
Apparently some of their vehicles suffered from resonace vibrations in the suspension, cured by added dampers and weights.
 
TitanTim said:
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=42

Tim.
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Good find Tim.

Seems to back up what Maniac was suggesting (although I haven't read the whole article :oops: )

I have this on both my Astra and Z (although I am an incredibly panicky owner), nothing wrong with either car, I'd assumed the road outside my flat was just a littl "ridgy"...whilst it looks like I was wrong, good to know there's not a fault with my cars :thumbsup:
 
Yep I think its the rotation flatspot at 30mph that then sets of a harmonic bounce with the car. Hence why I hardly feel it at other speeds. Been for a long run today, not felt it once so this is my going theory now. Clearly I'm just sensitive to it.
 
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