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 tyres 
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Firing on two.

Joined: February 10th, 2009, 10:12 pm
Posts: 155
Location: viseu - PT
Post Re: tyres
I've read a lot about tyre pressions here and on other (british, belgian, portuguese) forums and the opinions seem to vary widely.
I usually use 22 psi front and 25 rear.
The questions I always have and saw no reference anywhere:
a) Why the hell do we have to use a lower pression in front when it is there that the constant weight of the engine, transmission and gear box is?
If we are supposed to take in account the weight of the rear passengers, even when they aren't there, why don't we have to consider the constant weight on the front, and put more pressure on front tyres?
I know that if we put more pressure on the front, the steering wheel will make us feel the lack of softness, and if we diminish the pressure we will lose the famous 2cv power-steering :D, specially while parking...


December 22nd, 2018, 1:51 pm
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Firing on two.

Joined: February 10th, 2009, 10:12 pm
Posts: 155
Location: viseu - PT
Post Re: tyres
I've read a lot about tyre pressions here and on other (british, belgian, portuguese) forums and the opinions seem to vary widely.

I usually use 22 psi front and 25 rear.

The questions I always have and saw no reference anywhere:
a) Why the hell do we have to use a lower pression in front when it is there that the constant weight of the engine, transmission and gear box is?
b) If we are supposed to take in account the weight of the rear passengers, even when they aren't there, why don't we have to consider the constant weight on the front, and put more pressure on front tyres?

I know that if we put more pressure on the front, the steering wheel will make us feel the lack of softness, and if we diminish the pressure we will lose the famous 2cv power-steering :D, specially while parking...


December 22nd, 2018, 1:54 pm
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Firing on two.
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Joined: October 22nd, 2014, 10:59 pm
Posts: 1091
Location: South-Limburg
Post Re: tyres
I think a bit softer tyres are better in cornering / road holding. Higher pressure better for load carrying. A friend did put 2.5 atm in front and back and the car lost all its suspension softness. It bounced over the road at every bump or manhole.


December 22nd, 2018, 6:34 pm
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2CV Fan

Joined: April 20th, 2017, 10:55 pm
Posts: 90
Post Re: tyres
I'll stick my neck out and suggest that the lower pressures in the front allow for a larger 'footprint' of rubber on the road. For a car with most of its weight on the front, this would increase grip for both steering and braking. 22 + 25 (or 27) are good.

So why does my front wheel drive Nissan require 30psi all round? It's an altogether heavier car all round, and the tyres are much wider in section. Deflating the front would cause distortion, increase wear, and do me no favours.


December 23rd, 2018, 12:36 pm
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Firing on two.

Joined: February 10th, 2009, 10:12 pm
Posts: 155
Location: viseu - PT
Post Re: tyres
Agree


December 23rd, 2018, 2:08 pm
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Firing on two.
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Joined: February 11th, 2009, 12:32 am
Posts: 3279
Location: Chichester, West Sussex
Post Re: tyres
So I did some testing:

With 20psi all round I averaged 38mpg

With 26 at the front and 30 at the back I average 47.6 mpg

That was on the same road, doing the same journey (my commute of 50 miles). With the pressure that high the ride is a little firmer admittedly. Braking appears unaffected. I'm currently running Michelin 135s.

Tope speed is also better with higher pressure, with the lower pressures it was a real struggle to hit 70. With the higher pressure I'm back cruising at 74ish.


December 23rd, 2018, 3:21 pm
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Firing on two.

Joined: February 10th, 2009, 10:12 pm
Posts: 155
Location: viseu - PT
Post Re: tyres
But 135 tyres require more pressure, right?


December 23rd, 2018, 3:53 pm
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Firing on two.
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Joined: February 11th, 2009, 12:32 am
Posts: 3279
Location: Chichester, West Sussex
Post Re: tyres
Well yes, but there's nothing 'official' for them. Apart from maybe Mehari because I think they had them from the factory?


December 23rd, 2018, 4:22 pm
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Agony Aunt - You have a car problem? Speak to Ken

Joined: March 6th, 2009, 1:40 am
Posts: 3625
Post Re: tyres
Au contraire, chaps, since 'Revue Technique Automobile' recommends lower pressures for 135 tyres than for 125. ;)
Down from 1.4 bar to 1.2 for the front axle and from 1.8 to 1.65 for the rear on a 2CV 6 & Dyane6...


samfieldhouse wrote:
Well yes, but there's nothing 'official' for them. Apart from maybe Mehari because I think they had them from the factory?

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December 23rd, 2018, 11:22 pm
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Firing on two.

Joined: February 10th, 2009, 10:12 pm
Posts: 155
Location: viseu - PT
Post Re: tyres
Driving at such low pressure will increase fuel consumption and probably damage the tyres. I never understood why this Revue suggests these numbers... ;)


December 23rd, 2018, 11:43 pm
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