Many new grain and silage trailers nowadays come as standard with flotation tyres.

However, roll the clock back 10 to 20 years, and this wasn’t the case. During that period, super single tyres (385/65/22.5) were largely used.

Since then, trailers and the general machines we use have gotten bigger and bigger, which has brought about additional weightings.

During this time, we have learned a lot about soil and how to keep it healthy, with avoiding compression/compaction a big factor in this.

In recent years, more and more of these older trailers are being re-shod on larger tyres.

This week, we caught up with Kevin Burke from Kevin Burke Tyres (KBT) in Athenry, Co Galway who fitted a set of 560/45/22.5 tyres to a Kane grain/silage trailer, replacing its original set of 445/65/22.5 tyres.

Kevin Burke

Initial considerations

When making the move to larger tyres, you need to speak to a tyre specialist to establish whether or not the existing rim will be compatible with the desired wider tyre. Secondly, in this situation, the rear axle is steering.

This meant the scope to fit wider tyres had to closely analysed. After measuring the remaining room between the rear tyre and the trailer’s chassis at the full steering angle, the team soon came to the conclusion that the rear rim had to be custom built with a negative offset.

The set of 560/45/22.5 tyres (rear) replaced the trailers original set of 445/65/22.5 tyres (front).

Once deciding the width of the desired tyre, next up is its height. The original 445/65/22.5 tyres had a height of 1,120mm. The two tyres Kevin offered as being most suitable were a 560/45/22.5 and a 560/60/22.5. One was 1,076mm high and the other was 1,244mm. Accounting for the upward spring/bogie axle movement, it was decided that the latter tyre would not work in the available space, meaning the 560/45/22.5 was selected.

Selecting the rim

To carry the wider 560/45/22.5 tyre specified, it meant a move from the original 14in rim to a 16in rim was necessary. Despite the four new rims being the same width, it was decided to fit two different rim setups to the front and rear axles. Wheel offset is the distance from the middle of the rim to the to the mounting pad (the dish).

Rims can be fabricated and modified onsite.

The front two rims in this case are standard, with a ‘zero offset’, meaning the mounting pad (the dish) is positioned central on the rim. As the front axle is rigid, it means they could run relatively close to the chassis. In this case, they are running about 2in from the chassis.

As highlighted, the rear steering axle meant KBT had to fabricate two rims with a negative offset. A negative offset, as shown in the picture, means the rim’s mounting pad is positioned closer to the chassis. Kevin advised that a 1in offset would suffice.

The choice of this slightly stepped offset setup means the trailer’s weight is further distributed across more surface. Although the front and rear axles feature the same tyres, each axle is running the wheels by an inch offset to either side, thus spreading the trailer’s load over an increased area of 4in across the width of the trailer.

Kevin said: “In recent years, we have seen a lot of farmers and contractors looking to fit wider tyres on to narrow rims. The goal here is to have a square footprint on the ground, increasing the overall surface area. If the rims are too narrow, you will get an egg shape instead. This will have a negative effect and instead lead to irregular wear on the lugs, poor traction, possible sidewall cracking and bead damage.

To carry the wider 560/45/22.5 tyre specified (pictured), it also meant a move from the original 14in rim to a 16in rim was necessary.

“It will also lead to a difficulty in working at low pressures and won’t offer the same flotation effect. Such tyres won’t last as long and won’t wear evenly as they are not flat on the road. This was the reason we actually started manufacturing rims at our premises in Athenry. Typically speaking, trailer rims have a tolerance of +/ – 5mm, while larger tractor rims have a tolerance of up to +/ – 50mm”.

Readying the rims

The front axle rims were on the shelf ready to go, while the company fabricated the negative offset rims to suit the rear axle onsite. This involved welding in the inner dish at the desired offset position on the rim. Once welded, the rims were loaded into a fixed sandblasting cabinet. They were then cleaned down, and placed in an oven for 20 minutes at 200°C.

Once welded, the rims are loaded into a fixed sandblasting cabinet.

They were then powder-coated with an undercoat (like a primer), baked for another 20 minutes, powder-coated with the silver colour specified, and baked again for another 20 minutes. The company offers the rim blasting and powder coating service at a cost of €100 plus VAT per rim (typical price across small to larger rims).

Rims are then cleaned, baked, powder coated, baked again, powder coated with the colour specified, and baked again.

The right tyre for the job

Selecting the correct tyre with adequate speed and weight ratings is essential, and according to Kevin is an area where some people can be led astray with slightly cheaper flotation tyres.

The finished product

“Generally speaking, most people opt for one of two flotation tyre sizes for trailers, either a 550mm or a 560mm tyre. There are a lot of the 550mm tyres out there that feature a hockey stick thread formation. These tyres have a rating of 149A8, which means each tyre is rated to carry 3,250kg at a maximum speed of 40km/h. Such tyres do exactly as asked, but if you pull them with 50km/h rated tractors with heavy loads of wet grass or maize, they will fail. We have seen this time and time again. Heat will build up on the road, and either the sidewalls will separate and slow punctures will creep in around the rim or they will just blowout.

Rim centres can also be modified in-house.

“They may be €100 per tyre cheaper, but they will work out more expensive in the long run. My advice is to always ask an expert about such ratings. The tyre we chose for this trailer is a Maxam 560/45/22.5 with a 152D rating. Each tyre is rated to carry 4,300kg at 50km/h. It has a totally different radial construction to the tyre mentioned above.”

Costings

The Maxam 560/45/22.5 tyres fitted cost €500 plus VAT per tyre, with each complete wheel costing €599 plus VAT. Kevin Burke recommended fitting the Maxam tyre. A relatively new brand to the Irish market, he described it as being a good, reliable economy tyre which comes with an eight-year warranty package which covers failure on the manufacturer’s behalf.

Kevin Burke Tyres

Kevin Burke Tyres (KBT) was established over 25 years ago retailing tyres to the Athenry area. Since then, the business has grown to include three retail depots across Galway, a wholesale division and a wheel plant division where new rims are supplied and or fabricated.

KBT had to fabricate two rims with a one inch negative offset for the rear axle, which means the rim’s mounting pad is positioned closer to the chassis.

Covering all 32 counties, KBT carries €5m worth of tyres and rims in stock at its newly built facility in Athenry. The company is the sole Irish distributor of Maxam and Bandenmarkt, and is an OE partner for Michelin tyres and a Michelin Excel Agri Dealer.