Xantia tyre change

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David W
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Post by David W »

I'm not trying to make an argument of this, just give my experiences.
I own a 1993 Xantia and look after several more from 1993 to 1999. They are all 1.9 turbo diesels.
In all cases I have myself fitted replacement spheres from Andyspares, the same spheres (N45332 for the front, N45366 rear for hatchback)) have been fitted regardless of age.
In each case the cars have been on Michelins with the correct pressures.
All I can say is that the earliest cars do have a better ride and the wheel size is the only difference I know of!
David
mark_sp
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Post by mark_sp »

Just a thought but could the earlier car also be lighter ?
Mark
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Post by mark_sp »

thought number 2:
With the advances in tyre technology we could probably fit narrower tyres and see no reduction in road holding (probably an improvement in the wet) over the original tyre performance when the Xantia was introduced.
Mark
dgs
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Post by dgs »

I think that if you fit bigger wheel (but with same tyre profile) on a same car the comfort will be better.
guzzidom
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Post by guzzidom »

Watched this one with mounting amusement, fitting a larger diameter wheel with the same profile and tyre pressure will have precisely no effect on comfort whatsoever, in physical terms why should it? (and the first person to say because it has a larger volume of air in it goes to the corner in a pointy hat, same BAR pressure = same resistance, as volume is subject to pressure see).
It will however have two other effects, firstly, larger diameter wheels have traditionally been utilised for greater stability due to gyroscopic effects being further centred away from the hubs and somewhat stronger the larger the diameter/weight, the downside to this being (and try this at home folks) is a 15" wheel tyre combo is normally about 3 kilos heavier than a 14" wheel tyre combo when both inflated and for wheel reaction that is BAD news (which was originally where alloys came in with the Minilite back in the 60's) which basically means that the larger wheel will still be lumbering down from the previous rut when it hits the next one, whereas a lighter smaller wheel will have finished its previous reaction and be ready for the next one.
David W
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Post by David W »

Dom,
Actually I do think that a larger diameter wheel "should" give a better ride over very short sharp bumps, like raised manhole covers, because it is easier able to roll over the obstruction. For that reason our Land Rover on 7.50x16s gives a better overall ride on our potholed drove than either Citroen. This despite the LR having near rigid leaf springs.
You are spot on about the unsprung weight though and that is the only factor I can think of to cause this Xantia ride difference.
David
dgs
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Post by dgs »

Suppose you put a 2' wheel on a car. The ride wouldn't be very comfortable. If (in imagination) you put a 100' wheel you wouldn't feel most bumps. The difference in 186/65/14 and 185/65/15 is litle but better comf for 15 wheel
dgs
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Post by dgs »

For JohnCKL who said "Also consider the weight differences. I've weighed the 185/60/14 wheels (rim+tyre) at about 15kg while the 195/60/15 at 18kg, variance of 3 kg each wheel. Changed mine from the 15s to 14s to see the difference. Not that much by feel, only that 15" wheels are more stable. By theory of course, the smaller wheels would be more economical on fuel since they have to spend less energy to spin that extra weight and suppose to be faster on acceleration too. Besides, the smaller tyres are cheaper to replace and doesn't aqua plane as easily as fatter wheels. By contrast, wider tyres should brake and stop more effectively."
I am comparing the 185/65/R14 and 185/65/R15 wheels. They have same width and profile size, but only different overall diameter.
James.UK
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Post by James.UK »

I changed my wheels from 165/70/13 to 175/65/14 it made a notable difference on roadholding, and reduced oversteer to almost zero due to reducing movement in the tyrewalls. I cant see much can be gained by simply using a slightly bigger diameter wheel though..
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Kowalski
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Post by Kowalski »

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by dgs</i>

Kowalski, look at that table again. xantia 1.9di atmo till 05/95 has 95 666 858 spheres wich are 400/70bar and xantia 1.9di atmo from 06/95 has 99 666 857 spheres wich are 400/55. Isn't that right?
If you want to see wich wheel is more comf. you must test it on the SAME car. So put those larger wheels on xantia with smaller onses. (that will work only if you have same profile tyre and same manufacture 185/65/r15 michelin VS 185/65/r14 michelin) Of course that wider rim on a same tyre is less comf.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
I wasn't talking about the "xantia 1.9di atmo" my Xantias are both "Xantia 1.9 DI Turbo" and as I said have always had the same spheres fitted.
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Kowalski
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Post by Kowalski »

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by dgs</i>

Suppose you put a 2' wheel on a car. The ride wouldn't be very comfortable. If (in imagination) you put a 100' wheel you wouldn't feel most bumps. The difference in 186/65/14 and 185/65/15 is litle but better comf for 15 wheel
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
In theory, wheels and tyres with a larger rolling raduis should give a better ride than those with a smaller rolling raduis, all things being equal, but between my two cars this is not the case, clearly the construction of the tyres is not the same.
Larger tyres are for larger cars which tend to be heavier so they tend to have more robust construction.
PeterMann
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Post by PeterMann »

I made this change to my own 1994 Xantia. The 15 inch alloy wheels are heavier than the 14 inch steel ones. On my car, fitted with the correct profile tyre (55), the speedo reads the same.
The differences that I have observed are (1) that the steering is sharper, so I needed to use more skill to maintain smooth adjustments to direction (2) using a KUMHO silicone tread tyre, I have an improvement in grip of about 10% over the 14 inch Michelin MXV3 in both wet and dry, with a reduction in tyre cost of about 40%, but the tyre wears about 20% faster.
No perceptible difference in tracking on rough road surfaces.
Overall, I'm reasonably satisfied with the change.
One could compensate for a possible change of effective wheel diameter by fitting a tyre profile to suit . . . your tyre dealer should be able to work out a tolerably accurate match to your speedo's calibration.
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