Tyre Sizes and Pressures - Which list do you believe?

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Tyre Sizes and Pressures - Which list do you believe?

Post by Robsey »

Tyre Pressures – Who Do You Believe?

I thought I would do a little thread on tyre pressures for your Cavalier.

I found it very surprising how different publications post different amounts of information, and how accurate these actually are.

Firstly the units conversion table.

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The available publications are: -
1 - Vauxhall Owners Manual – that comes with the car when it is bought new.
2 - Vauxhall Technical Info System – Vauxhalls electronic information bible.
3 - Hayne’s Manual – Mine is the later updated version with the maroon Cavalier on the cover.
4 – Porter’s Owner’s manuals for Mk2 and Mk3 Cavaliers
5 – Halfords Owners manual. – Yes they did their own in-house manual in a ring binder with a pale blue Cavalier on the cover !!
6 – Auto Data. (I use the computer-based version 3.45).

The usual answer is to look at your owner’s manual, but I am sure that after the 20-odd years since the car was first sold, chances are that many people will simply have lost the manual, or previous owners failed to pass them onto prospective buyers.

So in the absence of the owner’s manual, I am sure most would turn to trusty Mr Haynes.
The most readily available manual to the man or woman in the street.

HAYNES MANUALS.
This is where the shock happens.
Haynes gives very limited and sometimes inaccurate or contradictory information.

In simple terms, my Haynes manual says…

165 R13, 175/70 R14 or 195/60 R14 tyres =
Front 27 psi or 1.9 bar (190 KPa)
Rear 24 psi or 1.7 bar (170 KPa)

But then it says -
195/60 R14 tyres =
Front 32 psi or 2.2 bar (220 KPa)
Rear 29 psi or 2.0 bar (200 KPa)

and finally -
195/60 R15 and 205/55 R15 tyres =
Front 33 psi or 2.3 bar (230 KPa)
Rear 30 psi or 2.1 bar (210 KPa)

Here is the screen shot of my old manual.

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PORTER MANUAL
The Porter manual gives information based upon engine size.
It acts as a better guide than the Haynes, but there are omissions or inaccuracies.

For example – My 1994 1.8 LSi (C18NZ) came from the factory with 175/70 R14 Michelin Energy tyres.
According to the Porter manual, this size was only fitted to the 1.7 naturally aspirated diesel (17D).
Still it is not as vague as the Haynes list. (all 3 lines of it).

The tyre pressures guide according to Porter’s

1.3 (Mk2 only) – 155 R13 – 29 psi front / 26 psi rear
1.4 and 1.6 – 163 SR13 – 28psi front / 25 psi rear or
1.4 and 1.6 – 185/70 HR13 – 29 psi front / 26 psi rear
1.8 and 2.0 – 185/70 R13 – 29 psi front / 26 psi rear or
1.8 and 2.0 – 195/60 HR14 – 32 psi front / 29 psi rear.
2.0 Sri - 195/60 HR14 – 32 psi front / 29 psi rear
2.0 16v – 195/60 R15 – 35 psi front / 32 rear or
2.0 16v – 205/55 SR15 – 33 psi front / 30 psi rear.
2.0 Turbo 4x4 – 205/50 ZR16 – 33 psi front / 30 psi rear

1.6 Diesel (Mk2 only) – 165 TR13 – 28psi front / 25 psi rear
1.7 Diesel – 175/70 R14 – 29 psi front / 26 psi rear
1.7 Turbo Diesel – 174/70 R14– 28psi front / 25 psi rear or
1.7 Turbo Diesel – 196/60 R14 - 32 psi front / 29 psi rear

Apparently wheel-bolt torques for all models is 66 ft/lb or 90 Nm.

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Halfords Manual.
At the time of writing, I could not find my copy, so cannot post up what nuggets of info it has to offer.

Auto Data v3.45

Here is the very brief listing from the electronic version.
(Ignore the engine specs - this is just to allow navigation to the table).

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Vauxhall Cavalier Owners Manual.

Due to the complex table in the manual, it is easier just to post up the images.

Oddly, the typical pressures in the owner's manual and TIS are a fair bit higher than those in all the other publications.

The big surprise is the difference to tyre pressure that is needed when changing between some engines.
An example being - if you change your engine from a C18NZ to C20NE.
Tyre pressures need to be increased by about 3 psi all round.
Maybe to cope with the difference in engine torque rather than engine weight.

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Robsey
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Re: Tyre Sizes and Pressures - Which list do you believe?

Post by Robsey »

Vauxhall / Opel / GM Technical Info System (TIS2000).

As with the owner’s manual, it is easier to post up screen shots of the tables as there are many variations, dependent upon engine size, tyre size and even sport (GT) or non-sport (GL) models.
With TIS, there are tables for each model year.
To prevent just a huge mass of tables (7 model years’ worth), I have put up the years where changes to car specs were made, so only 1989, 1990, 1992 and 1995 model years are listed.

1989 Vehicles.

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Re: Tyre Sizes and Pressures - Which list do you believe?

Post by Robsey »

1990 Vehicles.

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1992 Vehicles

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Re: Tyre Sizes and Pressures - Which list do you believe?

Post by Robsey »

1995 Vehicles

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