520/85R38 Tractor Tires

Buying 520/85R38 tractor tires

520/85R38 is a radial rear tire for high-horsepower row-crop and utility tractors, and a common size for duals. It is the metric name for 20.8R38: 520 mm (about 20.5 inches) wide, with a sidewall 85% of the width, on a 38-inch rim. If your tractor came on 20.8-38 bias tires, this is the radial upgrade that fits the same wheel, as long as the rim width is approved for it.

Most 520/85R38 tires are made with R-1W tread, about 20% deeper than standard R-1. That gives more grip in wet soil and more rubber to wear, which suits tractors that log a lot of hours.

Why radial in this size

• A longer, flatter footprint pulls with less wheel slip.
• Lower ground pressure means less soil compaction, if the tire runs at the pressure in the maker’s load table for your load.
• A smoother ride on the road between fields.

What to check

• Load index and speed symbol: for example 155A8. Match or exceed your current tires, and use a higher index for duals carrying heavy implements.
• Front-wheel-assist ratio: changing the rear brand or size can change the rolling circumference. Check it against your fronts.
• Used tires: ask for the tread depth as a percent, the date code and photos of both sidewalls.

Tell us the quantity, new or used, and where to ship for prices.

What else is 520/85R38 called?

The metric size 520/85R38 is the radial equivalent of 20.8R38 and the bias 20.8-38. It means a radial 520 mm (20.5 in) wide, with an aspect ratio of 85%, for a 38 in (965 mm) rim. Listings often show both names together.

How big is a 520/85R38?

The formula height of 1,849 mm matches a real tire. A BKT Agrimax RT 855 520/85R38 listing gives an overall diameter of 1,849 mm, a section width of 516 mm, load index 170 A8 and a weight of about 201 kg (444 lb) on a recommended DW16L rim. Other makes will differ slightly, so check the data sheet for your tire.

Should you choose 520/85R38 or a 650/65R38?

They have nearly the same height, but the 650 is 130 mm (5.1 in) wider, so it puts more footprint on the ground and needs more room and a wider rim. For most 520 fitments, stay with 520/85R38 unless your tractor maker approves the wider tire. See our big tractor tires guide for singles and duals.

What do 520/85R38 tires cost on our site?

We list 14 models in 520/85R38. 14 have a listed price, from $520 (Cultor RD-01) to $2,917 (CEAT Farmax R85) per tire, with a median of $1,808. Prices are per tire in US dollars and change with stock and season.

How tall is the 520/85R38 tire?

The nominal overall diameter is about 72.8 in (1,849 mm), which gives a rolling circumference near 229 in (5,809 mm). That figure is worked out from the size formula (rim plus two sidewalls). Real tires vary by make and load, so treat it as a guide and use the tire diameter calculator or the lead-lag calculator before you change size on a front-wheel-assist tractor.

Is 520/85R38 a radial or a bias tire?

It is a radial. The R in the size marks radial construction, and radials need careful pressure setting. See the radial vs bias guide.