Bring back ride quality!!

Bring back ride quality!!

Author
Discussion

kambites

67,461 posts

220 months

Saturday 18th February 2012
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Dr Jekyll said:
kambites said:
Bear in mind that you'll have a fair bit less grip because firstly you have less tyre width
Surely (all other things being equal) grip is a function of contact patch size. Why would a narrow tyre give less grip than a wide one with the same tyre pressures?
You usually run narrower tyres at higher pressure to keep the contact patch length (and hence the sidewall distortion) the same, do you not?

MC Bodge

21,552 posts

174 months

Saturday 18th February 2012
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Bonefish Blues said:
By the same token, my old 996 was much better on 17s than 18s - but the latter were absolutely necessary when it came to sell the car on.
Ffffffffaaaaaaashion!!!!!

davepoth

29,395 posts

198 months

Saturday 18th February 2012
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kambites said:
You usually run narrower tyres at higher pressure to keep the contact patch length (and hence the sidewall distortion) the same, do you not?
No. The contact patch isn't really a function of length, but of width.

davepoth

29,395 posts

198 months

Saturday 18th February 2012
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Dave Hedgehog said:
wow you old boys and your dodgy hips are nothing if not persistent
So what are you saying? Apart from an insult, I mean.

Trommel

18,988 posts

258 months

Saturday 18th February 2012
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davepoth said:
No. The contact patch isn't really a function of length, but of width
Only because a tyre isn't a perfectly flexible balloon.

kambites

67,461 posts

220 months

Saturday 18th February 2012
quotequote all
davepoth said:
Dave Hedgehog said:
wow you old boys and your dodgy hips are nothing if not persistent
So what are you saying? Apart from an insult, I mean.
He's saying that he's completely ruined the handling of his car by fitting stupidly stiff suspension and is in denial about it. hehe

kambites

67,461 posts

220 months

Saturday 18th February 2012
quotequote all
davepoth said:
kambites said:
You usually run narrower tyres at higher pressure to keep the contact patch length (and hence the sidewall distortion) the same, do you not?
No. The contact patch isn't really a function of length, but of width.
Isn't that what I said? confused

PumpkinSteve

4,098 posts

155 months

Saturday 18th February 2012
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kambites said:
Isn't that what I said? confused
Well I thought the higher pressure was to do with there being more weight concentrated over a smaller area of tyre, for example: 300kg over 195mm x 70mm vs 300kg over 175mm x 70mm, wouldn't you need a higher pressure to support the weight? As long as the outer diameter of the tyre is the same the contact area length wouldn't change, only the width would be different, correct?


Edited by PumpkinSteve on Saturday 18th February 14:07

kambites

67,461 posts

220 months

Saturday 18th February 2012
quotequote all
PumpkinSteve said:
Well I thought the higher pressure was to do with there being more weight concentrated over a smaller area of tyre, for example: 300kg over 195mm x 70mm vs 300kg over 175mm x 70mm, wouldn't you need a higher pressure to support the weight?
Yes. If you have the same tyre pressure, the contact patch will be the same size by definition (except for that part of the car's weight help up by the side wall rigidity, but that's generally quite small) so a narrower tyre with the same pressure will distort more under the load; thus you usually run higher pressures to keep the tyre distortion the same and that makes the contact patch smaller.

PumpkinSteve

4,098 posts

155 months

Saturday 18th February 2012
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kambites said:
Yes. If you have the same tyre pressure, the contact patch will be the same size by definition (except for that part of the car's weight help up by the side wall rigidity, but that's generally quite small) so a narrower tyre with the same pressure will distort more under the load; thus you usually run higher pressures to keep the tyre distortion the same and that makes the contact patch smaller.
Oh right: As a by-product of the extra weight, the contact area grows and therefore a higher pressure is required to compensate? I didn't realise that they took the contact area into great consideration, I just assumed it was more about the narrower tyre looking flat so they pumped it up a bit to compensate hehe

dan98

728 posts

112 months

Sunday 25th January 2015
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Sorry to revive an old thread, very interesting read though.

Mk5 Golf GT TDI, replaced 17 inch 225/45 with 15 inch steels and 195/65.

Fantastic improvement to ride quality, no noticeable difference in handling. Somehow feels 'quicker' too.
Looks crap, but not bothered about that.

Only problem now is steering - far too light, and needs constant tiny corrections at higher speeds (but past 95mph seems to settle down...don't worry i'm in Germany half the time)

On another note, anyone who previously mentioned the dodgy ride in A3/A4s tried the new A3 ? Does it still feel a bit 'wrong' on UK roads in SE spec? All my local dealers only stock the Sport versions.


HertsBiker

6,300 posts

270 months

Sunday 25th January 2015
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Worth reviving.

chrispj

264 posts

142 months

Sunday 25th January 2015
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dan98 said:
Sorry to revive an old thread, very interesting read though.

Mk5 Golf GT TDI, replaced 17 inch 225/45 with 15 inch steels and 195/65.

Fantastic improvement to ride quality, no noticeable difference in handling. Somehow feels 'quicker' too.
http://www.caranddriver.com/features/effects-of-upsized-wheels-and-tires-tested

Probably the link was quoted somewhere in the previous 15 pages already but lighter wheels & tyres = faster car... (& better economy). Marginally lower grip & fractionally worse emergency stop though.

OldGermanHeaps

3,801 posts

177 months

Monday 26th January 2015
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When the 19s on our m sport 5 series were in to have the cracks welded up and powder coated we got a loan of a set of e39 16s with 60 or 65 profile tyres and the difference was night and day, the car was actually pleasent to drive and comfy and you werent constantly swerving to avoid imperfections in the road. We would have deffo bought a set of 16s for it had we been keeping it by by that point we were totally fed up with it so sold it and bought an older x trail, which was better in almost every respect apart from the interior.
It pisses me off that in order to get the nice seats and a 3 spoke steering wheel on the germans you need to ruin the car with stupid low profile tyres and ridiculous suspension. Seat have the right idea on the altea stylance, 16 inch wheels, comfy ride but still corners really well and you still get supportive seats and a chunky small 3 spoke steering wheel.

andysgriff

913 posts

259 months

Monday 26th January 2015
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Pure wafting in the Merc


MC Bodge

21,552 posts

174 months

Monday 26th January 2015
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OldGermanHeaps said:
When the 19s on our m sport 5 series were in to have the cracks welded up...
Fit for purpose?

IceBoy

2,443 posts

220 months

Monday 26th January 2015
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Hi All,

Yes.....I agree, they need to bring back ride quality.

That is why both Mrs Ice and I drive the following, which work very well indeed on the UK roads:

Mercedes W204 C200cdi Elegance (205/55-16)
Mercedes W211 E320cdi Avantgarde (245/45-16)

Almost magic carpet but enough cornering ability without wanting to be a racing driver!

IceBoy

Bonefish Blues

26,448 posts

222 months

Monday 26th January 2015
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45 sections? Bit racy there old chap hehe

Roger Irrelevant

2,899 posts

112 months

Monday 26th January 2015
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The thing that gets me about the typical 'sport' suspension set up is that if you were designing suspension to actually use in a motorsport event on typical British B-roads then you'd come up with something quite different to what's on your typical modern repmobile. There's a really good twisty road near me that I used to love thrashing my old K11 Micra along, at times reaching the heady heights of 65mph. When my brother was last visiting we took a detour to drive it in his 3-series which has roughly 3 times the power and a 'sports' set up. Anything more than 60 was intolerable, and sometimes a bit scary, thanks to the bloody awful crashy ride - I'd never thought of it as a badly surfaced road before but it seemed like we were driving down a cart track. I now suspect that this is why so many people moan about the state of Britain's roads when on the whole they don't seem to bad to me - they're driving cars with wholly unsuitable suspension.

OldGermanHeaps

3,801 posts

177 months

Monday 26th January 2015
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MC Bodge said:
Fit for purpose?
Nope, but all too common on m sport e60s on run flats. Place that fixed them had a good rep.