Route the Belt

Most "wrong belt" mix-ups start with how the belt goes around the pulleys. Route it right and the machine runs, then you'll see the belt size that layout takes.

Furnace blower

Tap the pulleys in the order the belt goes around them. Tap the last one again to flip it so the flat back of the belt touches it. Tap a third time to take it off.

Grooved: rides the V sideSmooth: rides the flat back

Start at the drive pulley, the one marked DRIVE.

Belt routing for real machines

Traced from each manufacturer's own manual. Grooved pulleys take the V side of the belt; smooth idlers ride the flat back. Always check the routing decal on your deck first.

Land Pride FDR1660 (60") belt routing

OEM belt: Land Pride 816-308C, B103 Kevlar, 106" effective length. Our match: BK103

Start at the gearbox sheave on top of the deck. It is grooved, so the V side of the belt sits in it.
Run the belt out to the left blade pulley and around its outside.
Pass the fixed smooth idler with the flat back of the belt riding on it.
Wrap the center blade pulley, then run across to the right blade pulley and around its outside.
Bring the belt back past the spring-loaded smooth idler, again on the flat back, and onto the gearbox sheave.

Set tension with the eyebolt: 7 to 10 lb of push should move the belt 1/4 inch at the middle of the long span.

Land Pride FDR1672 (72") belt routing

OEM belt: Land Pride 816-116C, B136 Kevlar, 138.9" effective length. Our match: BK136

Same route as the FDR1660: gearbox sheave, left blade, fixed smooth idler on the back of the belt, center blade, right blade, spring idler on the back of the belt, back to the gearbox.
The 72 inch deck uses 6 inch blade sheaves and a longer belt, so a FDR1660 belt will not fit.

Same tension spec as the FDR1660: 7 to 10 lb for 1/4 inch of deflection.

Land Pride FDR2572 (72") belt routing

OEM belt: Land Pride 816-116C, B136 Kevlar, 138.9" effective length. Our match: BK136

Newer FDR2572 mowers carry the same routing decal as the FDR16 series, so the belt goes on the same way: gearbox, left blade, fixed idler on the back, center blade, right blade, spring idler on the back, gearbox.
It takes the same B136 Kevlar belt as the FDR1672.

Tension: 7 to 10 lb of push for 1/4 inch of deflection.

Land Pride FDR2584 (84") belt routing

OEM belt: Land Pride 816-064C, B158 Kevlar, 160.9" effective length. Our match: B158

Start at the 9 inch gearbox sheave.
Run to the left blade pulley and around its outside, then down to the center blade pulley.
Pass over the fixed smooth idler between the center and right blades, flat back of the belt against it.
Wrap the right blade pulley.
Come back under the spring-loaded smooth idler below the gearbox, flat back against it, and onto the gearbox sheave.

Tension: 7 to 10 lb of push for 1/4 inch of deflection.

Frontier GM1072E (72") belt routing

OEM belt: Frontier 5BP0008950, BX140. Our match: BX140

Frontier recommends starting at the right blade pulley.
From the drive pulley, the belt runs past the left tensioner with its flat back against it, then around the left blade pulley.
It crosses the top of the center blade pulley, passes the right tensioner on its flat back, and wraps the right blade pulley back to the drive pulley.

Tension: 12 to 15 lb of push should move the belt 5/16 to 3/8 inch halfway between pulleys. Move the spring to the next hole on the hitch plate as the belt stretches.