 | Home > Wheels & Tyres > Tyre pressures |
 
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| MatLandy Member Since: 11 Sep 2020 Location: Paris Posts: 184   
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I believe the wheel diameter, 16s or 18s, does not have much influence here. Your tyres are 265/65r18 and are of the same diameter as original 235/85r16 tyres fitted by LR. However the width is different (you have wider tyres).
The way I always understood it, is that it is the contact surface between the tyre and the road that is important - to keep vehicle handling, braking, as well as tyre wear within manufacturer's specs. This is why we put more air in our tyres (increase pressure) when laden, avoiding the tyres to flatten out on the road, and counter the effect of the additional weight. So to keep the contact surface the same, I would say the wider the tyres, the lower the pressure required. I do have a Puma CSW 110 with 265/65r18 (Pirelli Scorpion AT Plus) and run 2.1bar (front) / 2.5bar (rear) when unladen and commuting in the suburbs where I live. This gives me a reasonably comfortable ride for everyday use. I have always found, at least for the rear of a 110, that the recommended tyre pressure from LR gives a very harsh and bouncy ride, and that cannot be good in the long run both for my back and the landy. When going for long distance trips on motorway, loaded with 4 persons + luggage + gears, I increase the rear pressure accordingly at least to 2.8bar and ideally to 3.0bar until I reach my destination point and then re-adjust to the intended use (usually lowering a bit). /Mat |
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17th Jan 2022 12:41pm |
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| steveww Member Since: 05 Jan 2022 Location: Uppingham Posts: 567  
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Thanks for the info. You run the rear a bit higher that what I use at the moment. I'll try you setting and see how it goes.
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17th Jan 2022 12:49pm |
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| jpboost Member Since: 13 Apr 2021 Location: Gatwick Posts: 377 
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I certainly agree with Mat that the LR spec for 110 rears is rather uncomfortable when unladen.
I run mine around 35-40 psi depending on load, so a similar ballpark to those shared above. |
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17th Jan 2022 1:21pm |
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| Bluest Member Since: 23 Apr 2016 Location: Lancashire Posts: 4209 
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I've often wondered why the 110 rear unladen pressure is so high. It must have been chosen for a reason and I would imagine car makers spend quite a bit of time arriving at tyre pressures. The only thing I can come up with is that it may be a way to help prevent a rollover in an emergency swerve. The tyre being more likely to slide rather than grip and tuck under. Just a guess though. I was thinking back to the problems Ford had with Explorer which, if I recall, was at least partly due to running light truck tyres at too low a pressure for ride comfort reasons. 2007 110 TDCi Station Wagon XS
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17th Jan 2022 2:05pm |
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| htb2 Member Since: 02 Nov 2018 Location: Carmarthenshire Posts: 529 
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Also higher at rear to allow for towing, quite a considerable weight transfer on trailer over-run brakes when running at 3.5t+ trailer weight, when you hit the brake pedal before trailer brakes come on.
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17th Jan 2022 4:57pm |
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| Bluest Member Since: 23 Apr 2016 Location: Lancashire Posts: 4209
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It could be that, but there is a separate, higher setting for towing and fully laden. Maybe they just assume folk will be too lazy to do that so have a very high standard pressure. 2007 110 TDCi Station Wagon XS
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17th Jan 2022 5:25pm |
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| htb2 Member Since: 02 Nov 2018 Location: Carmarthenshire Posts: 529
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Covers both bases I suppose, I run at 40-45 psi rear, can be a bit harsh when unladen, tried it at lower pressures with the trailer but I got a lot of rear tyre cracking, Trailer unloaded is probably 900-950 kg, Laden anyones guess, stop loading when down to 1" clearance between bump stops and chassis. Difficult to know weight when chipping into it heavier when raining and then how much does timber weigh.
Trailer pressures are at 80-85psi, recommended 90psi, if run at the higher pressure appear to get more tyre damage and blow outs. |
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17th Jan 2022 5:46pm |
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| Race.it Member Since: 27 Aug 2019 Location: Algeciras Posts: 817  
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If this helps.
 Click image to enlarge Searching for my first Defender...and started just as Covid hit, so talk about timing. 5 months after starting the search I found it, and here is the details |
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18th Jan 2022 10:04am |
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| MatLandy Member Since: 11 Sep 2020 Location: Paris Posts: 184
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Interesting chart, although I would be interested to know where it comes from?
I find the figures stated for a 90 a bit unusual ... rear tyres with lower pressure than the front ? That would be the first time I see that. But then again I haven't seen everything yet 
/Mat |
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18th Jan 2022 12:59pm |
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| Race.it Member Since: 27 Aug 2019 Location: Algeciras Posts: 817
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I got told it was from the works cars that had the 18” rims and the v8 engine. That could also change the weight distribution so these maybe not valid for a diesel. Searching for my first Defender...and started just as Covid hit, so talk about timing.
5 months after starting the search I found it, and here is the details |
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18th Jan 2022 1:16pm |
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| Leamreject Member Since: 19 Dec 2020 Location: Middle Earth - Leamington Spa Posts: 970  
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I always run unladen road use so only inflate to 30psi max. Even at 30 it’s a firm ride.. Ride like you stole it!!
If I’m not on a bike it’s because only a 4x4 will do… 2011 2.4 Puma 90 HT |
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18th Jan 2022 1:58pm |
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