C5 X7 suspension

[jgra1]

hi all.
Anyone that has met me will know how I have bemoaned the ride/handling of my C5 exclusive for a few years now.

it made my old C5 110 saloon seem good!

2 things,
Once when a passenger, I connected the Diagbox on a perfectly flat part of the A303 - at 70mph the suspension ECU was reporting 'poor road surface'.

For the last 2 years, the car almost never changes into 6th gear by itself.

After attempting to get to Somerset last week (Pothole, Puncture, NSF, put space saver on - abandon that journey)
Made it the next day, and had the low-tread nearside rear tyre replaced.

The car now feels 10 times better! no more diagonal pitching, likes corners, and changes into 6th gear every time as it should.!

The rear tyre that was changed was in poor shape. It was once an Eagle F something, possibly a run flat.. the other good tyres are Rottella, I am trying to get all four tyres to match.

the tracking was out before the pothole, (steering wheel was straight) now the steering wheel has moved off centre.

so, to sum up, smashing into a pothole that could not be seen, putting spare steel with good Michelin on the front, replacing the worn Eagle on the rear, knocking the steering off centre, and now the autobox gearchanges are fixed, the car feels nice to drive..

thoughts?

John (very happy)

[bobins]

There have been a number of issues reported before where mismatched sets or sets of unevenly worn tyres have caused problems. The car gets confused as they all report differing speeds related to their differing circumferences.

[white exec]

And maybe Michelins bring something worthwhile to the party? They always have done for previous hpn suspension.

[jgra1]

Thanks both. I can't really afford the michelins I like the rotellas at 80 each . The eagle wasn't cheap new ! Glad that has flown off..

The car is great , just curious about what happened. Based on bobbins post I have several factors that all may have played a part just curious really

The gearbox is without a doubt the biggest shock !

I had written the car off because of it

[jgra1]

my thinking is a combination of :
rear nearside - Eagle assymetric now gone, worn out, maybe stiffer sidewall, possibly a runflat - changed for a brand new Rotella - larger circumference and probably softer.
Softwalled Michelin spare on front nearside in place of quite worn Rotella (over inflated and outer 25% worn away die to tracking) small circumference

tracking was out, will have it checked tomorrow, but maybe its been knocked back into shape.

Gearbox receives incorrect speed across all four wheels, often fails to change into fifth, almost never into 6th (over last two years) gearbox speed sensor error also has been a constant error code
2 unsuitable condition tyres on nearside have upset the transverse balance, making travel very side-to-side and opposite corner bouncy.

As for the last 300 miles since Friday eve, car has not missed one gearchange into 6, handles like I always thought it should have done, finally.

Things I have tried to do in the past to help :
Travelled in Stickyfingers car, Rick's car, had a citrojim bounce test - all to try and pinpoint anything.
Changed gearbox oil partially
thought about replacing the gearbox
thought about selling as a spares or repair
thought about finding and replacing the speed sensor
tried measuring rear wheel camber angles
tried measuring body height

never has anything helped much until now! hence my excitement the car now seems to absorb bumps across the front end, not just a corner.. and changes like an auto should, like it used to.

the above is my best guess ATM

[jgra1]

will i'll be damned

New tyre last night, spare back in the boot.. tracking checked and ok. 2 brand new tyres on the front, 2 slightly used on the rear. All same size and make, all 245/40/19 Y98

and the car has regressed back to its sick inducing horrible state, the 6th gear has gone missing mostly. what a difference a day makes.. for a while, about 5 days, I had a nice car to drive! in fours years and 60K miles

some interesting points made by Mandrake on a thread from 2014. Apparently I can gauge wheel speed individually and that's where I will start.. I cant replace 4 tyres, I could sell the 19s and buy a set of 17's but I now know the 19's in themselves will work..

will update,

disappointed, Tunbridge Wells

[Stickyfinger]

I take it all electro valves are working and the correct spheres are fitted (without reading the whole thread)

[jgra1]

yes SF, like I say it all worked perfectly for 5 days, the car is very tyre sensitive as Bobbins and V6 point out. I had no idea!

[Stickyfinger]

Just a thought, have you tried swapping the spheres between those stations that match each other....it is a time but no-cost test ? and maybe disconnect the HA3 part of the system (if that is even possible ?)

[white exec]

Before going down the spheres route, I think you must get the tyre circumference issue put to bed. From what you say, there is still a potential issue at the rear, across the axle, and in comparison with the front pair.

Rotational condition is (I assume) detected by the ABS sensors, so worth checking these out. Magnetic debris? Poor connection? Fault showing up on Lexia? If a serious fault, presumably the ABS warning light would show, but maybe not.

You've suffered a lot of aggro over a lengthy period with this, in order to save on the cost of a matched set of tyres. Maybe not worth the 'saving'.

Sphere and EV checking worth doing, yes, but get the tyres/wheels completely out of question first.

[Stickyfinger]

Offer, if you are coming over my way you can switch wheels/tyres with mine then take it out for the day....they are a fully matching set. No problem putting mine on 4 axle stands for the day.

[white exec]

That's a kind and worthwhile offer!
Run a Lexia check before and after?

[jgra1]

thanks for that, Chris

to be honest, I always thought that the 'aggro' was just the way these cars drove with 19's, and have been told that before. Ages ago I did try other hydraulic X7's gratefully from people on here (as a test, and other experiments besides mentioned above) and thought they drove better, but were on smaller wheels.. I have put up with it and just assumed it was the way things are with the X7 and Adriatic wheels, until last Friday after a fated trip to Somerset for a funeral.

My excitement at this car performing properly for the first time in years may not be obvious from my post at the top.

I cant afford £160 or £180 per tyre for the daily hack*, ironically because I has assumed the autobox was kaput the cars value to me had plummeted, and for my sins I have at least 24 tyres I need to keep on top of right now - which may mean I cant afford to run this car! but it's not worth much now and continues to be a decent quiet motor, I figured £400 of matched tyres would be ok, and have been in the normal sense (noise, mpg and road-holding, for what is really a Primary road mile muncher)

*Chris, if I had known a long time ago, that buying OE tyres and my car will change gear properly, handle better, and the tyres will probably last longer too, I can promise I would have, I have learnt a lesson here I guess

I am where I am now though, and that the car runs properly with the space saver tyre on, and not with a matched set is just mildly intriguing really.

I will look into the speed sensor readings and report back. Car is perfect otherwise, no warnings, I keep on top of the servicing and have done a fair bit already including an engine, all discs, belts etc

The X7 is a lovely car, this one is too, but I have tasted how it should be now, finally, by accident! and I will get back to that place

John

TL DR
I didn't realise until last Friday that these cars would behave so badly with mid range rubber, or anything but OE tyres, I didn't put up with agro to save £ - I just had no idea that may have been the case

[jgra1]

thanks SF

I will take some live readings over the weekend first though! and see what the speed sensors now report with the matched set, and also the 'poor road' message, I am sure they are connected and the root of the issue, and have been for a while

darn it, I may even take readings now and with the spacesaver back on! just for fun

[Stickyfinger]

No problems, I know it is just a small chance but worth it maybe. There are a good few X7's being scrapped now so you may even be able to source a full set of 17's relatively cheaply if it is the wheel size that the car does not like. Switching them may also give a good guide as to any increased comfort on 17's over 19's....


I also would not like a mismatched set on mine, ECU controlled stuff (electro-vales for example) tends to have no leeway for such matters.