Anyone with a large chunk of grass to knock down will probably be hankering after a set of triple mowers.

But with a new outfit costing in the region of £50,000, they are only really suited to contractors and the largest grassland farmers.

However, dip into the second-hand market and you could pick up a tidy set with a few seasons under its belt for less than half that.

See also: The low-down on buying a second-hand ATV

There is plenty to look out for, though. These mowers cover massive acreages at high speeds, so wear can be greater than you would expect and there are plenty bearing battle scars from the odd high-speed collision.

With the help of Rob Booker, grass kit specialist at Southern Harvesters’ Petworth dealership, we’ll show you how to avoid buying a pup. 

Chassis Many sets of triples have been driven flat-out by contractors on ground they often don’t know that well. That means nasty crunches with the odd manhole cover, tree stump and bramble-covered water trough are not uncommon. Stand well back and eye up the chassis from a few different angles to make sure it isn’t twisted. It’s also worth looking for any crinkles in the paintwork where metal has started to bend. A good final check is to fold up the rear mowers. If they don’t lift smoothly and lock into the latches, something is bent. If anything is out of line walk away, as it will be almost impossible to get completely straight again. 

Hoods The framework on the hoods isn’t as big a deal as the main chassis frame, but if there is too much duffed-up tubing it is a sign it has had a careless driver on the seat. Look under the skirts to see if there are any serious bends or repairs. Also lift all the hinged sections – they should move smoothly and not snag. Side sections of front mowers often get bent as drivers don’t bother folding them up before going between fields. 

Bed Check for slop in the bed gears by grabbing two rotors and rocking back and forth. A small amount of play is acceptable, but if there is a long delay before the neighbouring disc moves it probably needs a refurb. Also check the timing – each disc should sit exactly 90deg to its neighbour. Look for leaks, cracks or welds, too. All of the above are signs that you should probably give it a miss. The oil should be replaced at least once a year on a busy machine, so ask how often it has been done. 

Discs Grab the disc unit and lift up and down. Play here means a new bearing or rotor module (gear, shaft and bearing) is required. Undoing six bolts gets the unit out and the bearing can be replaced in about 30min if you have a press. It is much more difficult without. Whole modules cost about £360 plus VAT. 

Cutterbar drive Drive usually comes into the cutterbar at one side. Take off the cover and check for any play where the drive goes into the first disc. As all the power comes through here, it’s likely to show signs of wear first. 

Skids Because triples cover so much ground, the cutterbar’s wearing parts get plenty of stick. This mower has covered 1,200ha/ year for the past four seasons and the skids are looking the worse for it. Claas charges £35 plus VAT for replacements.

Half-moon plates If skids are really badly worn check the half-moon plates and the cutterbar itself for signs of wear. Half-moon plates will cost you about £130 plus VAT, so it is worth getting the skids replaced before these start to go. A very worn cutterbar is bad news, but it shouldn’t happen if these parts have been replaced.

Blade covers If the mower hits a stone, the blade covers take the brunt of the impact. Bent edges will catch grass and bung up the knives, so they will need to be replaced. Genuine Claas parts cost £190 plus VAT each so it is worth checking.

Gearboxes If they have had regular oil changes, gearboxes shouldn’t give any trouble. However, it is worth removing the bungs, checking the oil levels and looking for any traces of metal. Oil around the breather is a sign that it is not happy. 

Driveline Pull back the guards, test for play in the joints and check they have been greased. Also check pto guards for damage – particularly on the front mower as it can get fouled on the front A-frame.

Blade carriers Triple mowers tend to go through several sets of blades a year so the blade carriers get some stick. Check for wear by inserting the blade tool and rattling the blades backwards and forwards. If there’s a lot of movement the blades are more likely to catch and break. New carriers are about £100 plus VAT/disc and blades are £1.40 plus VAT each.

Conditioner Run the mower up to full speed and feel for any vibration. If it judders there is a good chance one of the conditioners is out of balance. If there are snapped or badly bent tines it’s a fairly easy fix, but look carefully to see if there’s any other damage. Also get a pry-bar under the shaft at either end to see if there is any play in the bearings. Also check the condition of the drive belts or chains, particularly if it has been hooked up to an overpowered tractor.

Grease lines It is possible for grease lines to get damaged by stones or corrosion, leaving bearings dry. Take a look at the main pivot points to check they have had grease and use a pry-bar to test for wear.

Float system Most triple mowers will have a float system running off accumulators. Pressurise the system to the arrow on the gauge and check it doesn’t leak. If it won’t hold pressure the accumulators could need regassing.

Control box Plug in the electric control box and check all the functions work. Snags in the cable are also quite common.

Top tips

• Match the mower to the power of your tractor; an 8.4m set needs a minimum of 200hp on the front
• Check all the extras are there – you should get a blade tool for each mower, owner’s manual, brackets to attach the front mower float system to the tractor and the control box
• Check the front pto is long enough for your tractor and that it turns in the correct direction, otherwise you’ll need a new rattle clutch and will have to flip the gearbox 180deg
• If you’re planning to buy a front mower to go with an existing rear offset; check you have the correct overlap or there will be an embarrassing strip down the middle