UNDER PRESSURE

When you're travelling in your motorhome, your not always next to a petrol station or airline. We're testing pressuage kits, and showing you our top picks!

We assembled several of the most widely available units and put them through their paces. Unlike car tests of these units, the air compressors have a much tougher challenge when it comes to inflating tyres to motorhome pressures. Typically a motorhome tyre will run at almost double the pressure of a car tyre – often 50-75psi.

ACCURACY

Some of the compressor gauges were more accurate than others, but you’re best to use them as rough guides and always set the pressures with a decent separate pressure gauge. For example, one model’s gauge was marked in 5psi increments. It is useful if the gauge on the compressor is reasonably accurate, though.

AUTO SHUT-OFF

If you’re easily sidetracked you need to look for a compressor with an automatic shut-off function. You preset the desired pressure, switch the unit on and it will automatically shut off when the correct pressure is reached. This is quite useful (especially when the gauge is accurate too).

OTHER FUNCTIONS

Two types of connector are commonly used: screw-on fixings and lever-type clamp on units. Screw-on types are easier to use and need less clearance around the valve to fit. They often come with built-in bleed valves that allow you to deflate the tyres more easily to set the correct pressure.

You can buy a basic 12V air compressor for a fiver. But having tested two versions of these units in the past, frankly don’t bother (one overheated and failed during testing and I took it apart to see if it could be fixed. It was appalling quality). Spend anything less than about £20 and you’re just wasting your money on a poorly made unit that will rapidly overheat and fail when tasked with inflating to the high pressures demanded by motorhome tyres.

These are our top picks

RING RAC630 

Cost: £32.99  Pressures: start 50psi; end 58psi

Time to inflate: 2mins 8secs  Lead length: 3.15m

Weight: 1.24kg  Size: 20cm wide x 18cm long x 10cm deep 

Case: Yes  Valve fixing: Screw on  Bleed valve: Yes 

Auto shut off: Yes From: Ring

One of the more compact units tested and supplied in a decent padded case, gets the Ring RAC630 off to a good start. The auto shut-off setting was intuitive to use. It inflated the tyre rapidly and has a decent screw-type connector with a bleed valve built in for easy pressure reduction. The gauge proved accurate, but it slightly underinflated the tyre on the auto setting (we checked it twice, but the results were the same). Set at 60psi it shut off at 58psi (but proved spot on with the Draper pressure gauge). Set to 62psi, it would probably have been perfect. Despite this, it’s an excellent model as it has lots of thoughtful design features – convenient cable storage with a Velcro-style strap, light and compact case. It’s intuitive to use and good value.

AIR COMPRESSOR WITH LIGHT A259  

Cost: £21.50  Pressures: start 50psi; end 65psi

Time to inflate: 5mins 8secs  Lead length: 2.85m

Weight: 1.30kg  Size: 25cm long x 11cm wide x 16cm deep 

Case: No  Valve fixing: Lever-style clamp on

Bleed valve: No  Auto shut off: No  From: Towsure

 The cheapest 12V compressor on test has cheery yellow and black styling and packs plenty of features into its rubberised case. The LED light angles upwards and there are several adaptors housed on the opening flap. The casing scarily warns that it’s a ‘Class 1 Laser product’ but I couldn’t find any lasers on it. It claims to be impact resistant and despite not having a case, it does have thick rubber edges so would be fine stored loose. Although it looks the part, the compressor part was slow and the gauge tricky to use accurately as the scale is only in 5psi increments. If you have a limited budget and need an all-in-one light and inflator, it’s a cheap and cheerful unit to have around.

RING RAC900 HEAVY DUTY AIR COMPRESSOR

Cost: £74.99  Pressures: start 48psi; end 60psi

Time to inflate: 42secs  Lead length: 2.4m (plus 7m of coiled air hose)  Weight: 3.42kg  Size: 33cm long x 21cm wide x 17cm deep  Case: Yes Valve fixing: Screw on  Bleed valve: Yes Auto shut off: No From: Ring

The RAC900 is an industrial looking bit of kit and has a durable metal body with cooling fins. It comes with a separate seven-metre coil of air hose. This is incredibly useful for motorhomes as it means all wheels are easily accessible out of the box.

Unlike all the other units on test it comes supplied with battery clamps as it draws too much current to be used via a cigar lighter (It draws 23A, most cigar sockets can’t cope with this). On the Transit test motorhome there was an easy-to-get-to positive terminal under the bonnet, while the unit’s negative lead was simply clamped to a handy stud on the engine block - any earth point can be used. The air hose is connected to the compressor body via a metal quick-release connector, while the gauge is built into the hose rather than the compressor itself. Care must be taken on vehicles with dished wheels (like this twin-wheel Transit) to avoid scratching the paint with the beefy brass knurled screw-on valve adaptor but, like the unit itself, it looks built to last. In use it was easily the best on test and incredibly fast, taking just 42 seconds to inflate the tyre. The pressure gauge was pretty accurate too. As an added cherry on the cake it was one of the quietest units we tested.

For long motorhomes or RVs, or if you just want the ultimate unit, this was the best unit on test by miles and is well worth the extra cost. If you have any other regular inflation tasks then this is the unit for you. Apparently it’s the one used by all the breakdown companies, too.

VERDICT

All of these compressors are capable of inflating a motorhome tyre and they all do what they say on the tin. The manual pumps can immediately be ruled out – unless you’re a fitness fanatic or a masochist they’re just not worth the inevitable cardiac arrest. Most of these connect to cigarette lighter in your motorhome. You may have to buy a budget extention cable too.

The Ring RAC900 side-steps all the limitations of having to use the cigar lighter for power by hooking up straight to the battery. At first I thought this would be a drawback, but in practice it makes a lot of sense. It not only gives you more 12V cable, but also keeps all the grubby mechanical bits away from your easily-marked fabric trim. As most modern motorhomes have easy to get at terminals under the bonnet for jump starting (with the black negative earth lead able to clamped to almost any handy unpainted earthed metal point) this is only takes a few seconds longer than plugging into the cigar socket. But you will need to pop the bonnet and this may not be convenient for some.

Perhaps it’s unfair to compare a professional model like this to the cheaper models, but for motorhome use, this was easily the best unit on test. It was significantly quieter than most of the other units on test and built like a tank. If you have any other inflation tasks (blow-up furniture, boats etc) them this unit would also be ideal. The only thing to bear in mind is it weighs 2kg more than most units and is slightly bulkier (but comes with a good case).
 

Finally, it’s well worth shopping around online for the best price. For example, we found the Ring RAC630 for as little as £20.40 plus carriage on some web sites, while the cheapest price we found for the RAC900 was £69.99. When buying online make sure to check if VAT is included and the cost of post and packing.
 

USEFUL CONTACTS
 

Halfords, Branches across UK
Tel: 08450 579000
www.halfords.com
 

Terra-S (Germany)
Tel: 0049 7551 92000
www.terra-s.com

Towsure, Stores in Sheffield, Halesowen and Southampton
Tel: 0114 250 3000
www.towsure.com
 

Ring Automotive (widely available, to find your nearest stockist contact below)
Tel: 0113 213 7389
www.ringautomotive.co.uk