C5 X7 suspension

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Hell Razor5543
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Re: C5 X7 suspension

Post by Hell Razor5543 »

Don't you have to 'tell' the X7 if you change the wheel size?

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Stickyfinger
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Re: C5 X7 suspension

Post by Stickyfinger »

Yes

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Re: C5 X7 suspension

Post by jgra1 »

sorry all! thanks for all inputs

my final say at the moment, as its probably got lost somewhere or I haven't already said it .

I bought the car with matched tyres in 2015, and then replaced those with matched (but part worn!) tyres, and then made a further bad decision to start replacing that set with - new matched tyres, but this took a bit longer than I had hoped.

The car has always handled like a drunk dog, except possibly with the original set that were on the car, I cant remember to clearly.

I have finally got all the tyres to be matched again, as of last night. Same make, size etc etc. to be fair 2 of the tyres are brand new and two are partially worn but with plenty of tread.

However, when only 3 matched tyres and a spacesaver spare on, the car felt like a dream, now with 4 matched tyres its reverted back to a drunken dog .

the moral of the story is not to give dogs a drink :)

will do some diagnostics, and report back

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bobins
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Re: C5 X7 suspension

Post by bobins »

John - Many years ago, back when 'Fanny' was a girl's name, I offered to lend you a set of 17" wheels/tyres so you could try them out :) The offer still stands - I'm currently using my winter wheels/tyres, so the summer's are sat in the garage. They're Michelin Primacy. I'm a bit too flat out at the moment to meet you halfway between here and there, but if you fancy a trip to Midhurst, you're welcome to borrow them to prove / disprove any thoughts you might have :-D As long as I get them back some time in April 8-[

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Re: C5 X7 suspension

Post by jgra1 »

that is very kind Bobbins :)
A trip to Midhurst is a nice trip! and I am just off the A272 as well now!

I may take you up on that kind offer, like I said I am down :( that I had the 'good life' with the spare tyre and 3 others, but I am not beaten :) just curious now I know the car was perfect on Tuesday like that, and now is back to her usual pushy self.

Its as much the gearbox, why have an auto and have to change manually every other section of road!¬ :evil: :rofl2:

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white exec
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Re: C5 X7 suspension

Post by white exec »

Low profile tyres are going to be a lot less comfortable a ride than standard profile.
With hpn, the first line of comfort is tyre sidewall, while avoiding over-inflation. It was designed that way.

Silly thoughts, but
- Are all the tyres mounted correct side out?
- Have any of the tyres been used, and then transferred diagonally on the car; mention this because tyres become 'set' in a rotational direction (both rubber and ply stresses), and if switched L-R, their action can become unpredictable. OK to move F to R, but not L to R.

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Re: C5 X7 suspension

Post by jgra1 »

Sorry all I completely got the wrong end of the stick yesterday !

When I talk about a matched set I mean same make similar age and similar tread depth (with a few mm) this is based on some of the God awful combinations on cars I have bought in the past

Everyone else is talking about brand new fitted at same time ! My bad :)

Car was marginally better today. Will do some investigations over weekend

Chris yes changes have happend over last few days . Every tyre has moved . 2 are new .

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Re: C5 X7 suspension

Post by Sloppysod »

Had similar issues with my C5, it would not change up to 4th when going araound corners, very basic but I measured the circumference of the tyres with the wifes dressmaking tape..:-$ and found one to be about 12mm more than the other, the result from a simple calculation (Circumference/3.1419 = Diameter) told me that one tyre had a rolling diameter of about 4mm more than the other tyre on the same axle, I replaced this with my illegal bald spare that measured about the same and 'Voila!!' fixed what I thought was going to be an expensive gerabox fault. There seems to be a big tollerance in tyre manufacturing, but then 4mm is the difference between a new an a not so new tye.

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Re: C5 X7 suspension

Post by jgra1 »

Thanks Stu I did the similar calculations earlier today between brand new and part used tyres. Will update tomorrow with a little news and a question

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Re: C5 X7 suspension

Post by jgra1 »

findings from yesterday were mixed..

car drove quite well, changed into 6th gear most of the time.

Speed readings are only possible below 10kmh, and from what little I saw, the wheel speeds all agreed with each other.

Suspension was changing from 'poor' to 'normal' surface and back a lot, which I think is encouraging somehow.

Diagbox measured tyre pressures and temps before I left: (all over the place!)

NSF - 1.8b - 8°
OSF - 2.7b - 11°
NSR - 2.1b - 9°
OSR - 2.3b - 11°

and on return:

NSF - 1.8b - 14°
OSF - 2.8b - 19°
NSR - 2.4b - 17°
OSR - 2.2b - 15°

(the car has had two tyres in the last few days, and with no dash warnings I had assumed they were all the right pressure)

I thought I would at least get them to be correct using the diagnostics as a way of checking.. unfortunately, the car has the sensors on the nearside with wrong way around (have done about 100 miles since wheels have swapped places)

I had to pump up the rear neaside to get the value of the front nearside up! (1.8bar) - 4 tyres are now correct pressure in terms of where they are on the car, but not in terms of where the car thinks they are..

2 questions:
if there has been confusion over the pressure monitors in the past, it could really mess up the suspension?
how can I get the sensors to report they are where they should be? I tried 3 different places in Diag but stopped short (I wrote down the four sensor ID's and where they are now)

I will measure circumference I think as well, as Stu did

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Re: C5 X7 suspension

Post by GiveMeABreak »

Hi John:

1) TPMS is an entirely separate system and independent from the Suspension ECU - so no. The ESP ECU is used for the vehicle speed and wheel pulse info, and the Steering wheel angle sensor is also used with the BSI for the audible warning and wake up info.
2) The system needs to be reprogrammed if / when you rotate the wheels. Positional information cannot be displayed until there is a fault.

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Re: C5 X7 suspension

Post by jgra1 »

thanks Marc.

So that suggests that any roadholding issues caused by incorrect pressure tyres are a physical thing (i.e. not aggravated by any suspension electronics) The main / only reason to have the correct sensors in the right places is so the driver knows which tyre needs air / or is punctured.

I don't know how to reset the sensor geography in Diagbox. Is there a method written down that holds my hand through the process? There were 3 options in 'Repair' TPMS (or what it's called) and I didn't know which one to go for? I didn't take a pic of the screen at the time either.

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Re: C5 X7 suspension

Post by GiveMeABreak »

I’ve always had the dealer do it on account the warning was coming on and being in town at the time. When they reprogrammed it, 10 mins later the other side threw one.

Turns out he incorrectly tried to programme one on its own when you need to do the lot each time together. So I’m not sure if you can do it in Diagbox without the need for other kit John.

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Re: C5 X7 suspension

Post by jgra1 »

thanks Marc. As it seems not to be that important, I will leave it alone. Now I remember seeing something about special tools when I was in the menus..

will not worry too much about the car for now, one or two other tests maybe.. its changing gear often enough, feels uncomfortable as it always had. If it wasn't for the recent 'good spell' I would assume nacked spheres..
there is a big front end job looming, maybe I should use that opportunity to get the spheres tested, at least the four corners~?

I remember Citrojim being able to test at home, is that an option for this car would anyone say? or is it send away specialist only?

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Stickyfinger
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Re: C5 X7 suspension

Post by Stickyfinger »

Jim cannot now.....but I have a tester here...

We would however need to flush the LHM out and switch to LDS for your spheres if you wish to use it. Not a problem