19" wheels

[Rp0thejester]

If it wasn't fun being here, I'd of been long gone which would of pleased Mick and Jim!! But tough!! I'm like a boil

[MattBLancs]

Last post before I give up and off to bed.

Seems the Google/Facebook/fate/whatever has caught up with me, and so Facebook has just suggested a bit of clarification between Speed and Velocity:

From Facebook

Night all!

[MattBLancs]

I'm like a boil

In need of "lancing" whatever that is!?!
I've no idea other than "lancing a boil" is a phrase I've heard of but am squeamish enough to be sure to do my best to keep myself oblivious to its meaning! Google image search = not a flipping chance!

[Sloppysod]

On the wheel and tyre vs speedo.
My X7 auto gearbox had problems changing up a hear while changing direction, off a roundabout, accelerating hard when overtaking. I thought the gearbox was stuffed.
then I measured the circumference of my wheels/tyres. Even though they were all the same size, one had a circumference of 15mm bigger than the others, it was a different make. New tyres fixed my gearbox problem
Now, the reason was that the ABS ECU, got a signal saying one wheel was out of sync - slipping - therefore, would not allow the gearbox to change up. So even just a small 4mm (approx) difference on diameter makes a difference on actual speed

[MattBLancs]

Wow, surprised such a small difference was sufficient. Would be enough to give the same error with three well worns and one brand new (e.g. following picking up a nail in one of the four equally worn set of four, hence a single brand new tyre!) E.g one new 8-9mm tread depth, old ones 6mm or lower would give same 4mm diameter difference.

(Sorry for pedantry, but if you were accelerating hard, would you not expect gearbox to change down rather than up?)

[Rp0thejester]

Sloppy, I'm surprised at that. I wouldn't of thought 4mm would make a difference. If you had new tyres fitted would that solve the issue? Or is the system based on 'majority rules' so 3/4 are doing that why isn't No4?

[Hell Razor5543]

I remember CitroJim had a similar issue with his XM several years ago. Somebody commented that the wheels looked to be the wrong size. When Jim checked he found they were mismatched, which explained why the gearbox was throwing hissy fits.

[Sloppysod]

Sloppy, I'm surprised at that. I wouldn't of thought 4mm would make a difference. If you had new tyres fitted would that solve the issue? Or is the system based on 'majority rules' so 3/4 are doing that why isn't No4?

I wouldn't of believed it, I went looking after do some googling, yes it seams a small amount, but possibly, was a few years ago, the tyres on the same axle could have been worn differently. All I know was before this I was looking at a gearbox rebuild, and since its been perfect.

[andy5]

On the wheel and tyre vs speedo.
My X7 auto gearbox had problems changing up a hear while changing direction, off a roundabout, accelerating hard when overtaking. I thought the gearbox was stuffed.
then I measured the circumference of my wheels/tyres. Even though they were all the same size, one had a circumference of 15mm bigger than the others, it was a different make. New tyres fixed my gearbox problem
Now, the reason was that the ABS ECU, got a signal saying one wheel was out of sync - slipping - therefore, would not allow the gearbox to change up. So even just a small 4mm (approx) difference on diameter makes a difference on actual speed

Wow, surprised such a small difference was sufficient. Would be enough to give the same error with three well worns and one brand new (e.g. following picking up a nail in one of the four equally worn set of four, hence a single brand new tyre!) E.g one new 8-9mm tread depth, old ones 6mm or lower would give same 4mm diameter difference.

(Sorry for pedantry, but if you were accelerating hard, would you not expect gearbox to change down rather than up?)

A friend used to own a 4 wheel drive version of the Volvo 850 estate

It was recommended to have no more than a certain difference in tread (I can't remember exactly, but small, maybe 1 to 2 mm) between any of the 4 wheels, otherwise one or more of the differentials would be loaded all the time, so there was occasional regular swapping of wheels, and replacement after a puncture could ultimately mean changing more than one wheel, possibly all four. He ended up with a stack of secondhand wheels in the garage, with a range of tread heights.

[MattBLancs]

Wow, what a faff!

Sounds like a design failure to me - the heat load generated by a lightly loaded drivetrain (i.e. maximum difference in speed between wheel sizes will be steady speed cruising along the motorway - not a lot of torque through the system at steady speed) wouldn't generate much heat I'd have thought.

[andy5]

Wow, what a faff!

Sounds like a design failure to me - the heat load generated by a lightly loaded drivetrain (i.e. maximum difference in speed between wheel sizes will be steady speed cruising along the motorway - not a lot of torque through the system at steady speed) wouldn't generate much heat I'd have thought.

Not much at steady state like that, perhaps, but bear in mind the standard T5R and R versions had about 240 to 250 bhp, and a different person told me that some police versions had 285 or 315 bhp

Edit: I may have to correct myself, now I've looked on Wikipedia. The AWD version was 190 bhp

[bikesteve64]

anybody know where i can get a descent set of 19" alloys for ds 5 at a reasonable price

typo i meant 18"

[bikesteve64]

would softer shocks and springs solve the harsh ride problem or would that be opening a new set of problems ??

[NotAnInterestingName]

The earlier "Citroen" DS5 was criticised for its harsh ride quality by several reviewers, regardless of the wheel size. I understand it was quite bad. It was successfully revised for the later "DS" DS5.

I don't know whether you could retrofit whatever improvements were made. Probably an expensive and complicated process, but might be worth a new thread or looking for one that already exists - I have read of someone here suggesting doing this but don't know the outcome.

All I can suggest is that the later "DS" brand version is acceptably OK. If it really bothers you then selling and buying a bit newer might be one possible option.

[bikesteve64]

anybody give me a yes/no answer if i put 18"wheels on and normal tyres (,i.e not low profile) will it affect my speedo reading