XM on C6 18" Alloys.

[casalingua]

My biggest concern with fitting modern wheels is that they don´t allow for tyres with a high enough profile. For me a thick tyre is not only more comfortable but looks better (that´s my unfashionable opinion). When I see the fat tyres on a car like the GSA it makes me think: "ooh, comfy" and I suppose this is the counterpoint to people who like rubber bands on their cars because they imagine it looks sporty. It makes me laugh to see cars in Ireland (with our terrible roads) shod with really low profile tires. Do these people not comprehend the driving conditions they are in the midst of? It´s a milder form of the lunacy of S American dictators buying Ferraris and having only dirt roads to run them on. No, Citroen means comfort first and handling second. That means fat tires and make my wheels OEM spec, please.

[CitroJim]

I quite agree with all of the above casalingua

[casalingua]

Apart from that I know nothing at all about tyres. LJK Setright was right to point out how strange it was that most of us paid next to no attention to the 20 cm sq that kept up stuck to road. He was a demon for cross-comparing tires on his Prelude. I think the problem is that tires are expensive to buy, hard to cross-compare and the car/tyre combination muddies an objective view of which parameter is working or not. So, I´d like to know more about tyres but I will never be able to assess the information. In my own car´s case I´ve never had the spare cash to afford the Michelins specified. I need to make do with a "middle-market"all-season tire. You could say that I am missing out. And that´s true but until I have the money to completely tighten the suspension elements I won´t spend any money on the tires. A pity really. Does anyone know if one can get a tyre with a higher sidewall than the recommended XM tyre size? I am idly wondering if I could add some more comfiness to the car´s ride by adding a centimetre or two to the sidewall, or one? (I don´t even if a cm much or not even noticeable). Citroenet suggests that the side wall is 60 mm high on the V6 and turbo models of 1997 and 65 on some of the others. I did a Google of this size Tyres. 195/70 R-15 and you get ads for van tyres. So, I´ve just learned that adding 5mm to the sidewall moves the tyre into van territory.

[casalingua]

Avon sell tyres with that dimension and the speed rating is R meaning you can drive at a shade over a hundred. I never drive over a hundred; ninety the odd time but mostly I´m cantering at 60 mph (I live in Denmark, speeding is utterly, utterly futile). I must look into this option the next time the tires are due. Fat tires on my car! Wow. That would be fun.

[xmexclusive]

I believe the 60 and 65 tyre numbers you mention are percentages of tyre width and not fixed dimensions in mm.
So some typical XM sidewall depth examples are:-
195/60 = 117mm.
195/65 = 127mm.
205/60 = 123mm.
206/65 = 133mm.
The tyre sidewalls form the primary vertical air spring in the XM suspension.
The sidewall stiffness of the front tyres is also a major factor in steering response.
In my opinion changing these should not be done without full understanding of likely effects.
There is one other reason I do not change tyre sizes significantly from manufacturers specification.
Fitting over wide or over narrow tyres changes the shape of the tyre footprint.
This can seriously affect stability particularly laterally.

John

[MTXM]

My 1989 V6 had 205/65 tyres fitted onto standard size three spoke alloys that have since been removed and sold (see photo). Regards, Matthew T.

[casalingua]

Hi John: immediately I am aware of the depth of my ignorance. I actually thought the figure referred to depth of sidewall in millimetres but evidently the tyre manufacturers prefer something more counter-intuitive (like mixing metric and imperial!). But would changing the sidewall depth have much of a negative effect under ordinary driving? I would tend to think not but have no data to back up this assertion.

[russ92xmsed]

I was under the impression that higher sidewalls, apart from a better ride, gives a sloppyer handling feel. As the car moves laterally around more. Sort of squirming on its tyres. But really as you point out, ...and smaller tyre walls reduce this but can give a harder ride as there is less rubber to absorb thumps. All pretty much explained by John really. I doubt the normal everyday driver wouldn't really notice much of a difference if the sizes were subtle. Extremes would be noticeable I would guess.
I would go with ride quality everytime...especially with our excuse for roads. XM are not sports cars, they are meant to waft from a to b in a relaxing manner. Not get the back out on every roundabout!! so larger tyre walls for me.

[MTXM]

XM are not sports cars, they are meant to waft from a to b in a relaxing manner.

With the possible exception of the S1 V6 24v Russ, which is very much a sports car dressed in a saloon body (that is also quite sporty I think) and not what you can really call a wafter!! Regards, Matthew T.

[russ92xmsed]

XM are not sports cars, they are meant to waft from a to b in a relaxing manner.

With the possible exception of the S1 V6 24v Russ, which is very much a sports car dressed in a saloon body (that is also quite sporty I think) and not what you can really call a wafter!! Regards, Matthew T.

Yes..I suppose you are quite right Matthew ..the V6 and the 24V are impressively fast cars and with the Hydractive they have the handling ability...but they aren't like a M5 or RS6 for example...errr not that i have driven those types of cars mind you. The Xm is still primarily a comfy cruiser that can handle when it needs to. Where as an Audi or Beemer are set up to be sports cars all the time. You could call XM's the French Jags....they have pace (in V6 24V form) Space and to us at least grace.


Anyway...treading over old ground....these are what the C6 alloys look like shrunken.. interesting what scaling them down does. I think personally they look much better.