This one that I have is thre recommend replacement part it’s 1/2 x 90”. So is there like a 1/2 x 85” I should try?
Prime Line, Rotary, Oregon & Stens all do OEM spec ( so they say ) mower belts
All of them have a "belts by length" table on their on line catelogues.
Stens & Prime Line also do a line of strait Kevlar reinforced belts in 1" increments .
Gates do a line of mower belts and again have a belts by length feature in their catalogue
Now there is a massive difference in belt structure
Deck belts usually have bigger reinforcing cords in them to give them greater shock loading resistance
Drive belts usually have thinner reinforcing
Belts that bend backwards a lot have the cords deeper into the V than belts that are not as serpentine in their run
Belts that clutch & need to slip like your deck belt must be covered so they can slip and not be sticky when hot like your cars fan belt
The cover can be kevlar fibre on the top shelf belts , cotton on lower grade & polly propolyene on the cheaper ones .
And then we get to the actual chemistry of the rubber which varies greatly
Finally there is construction
Top shelf belts , like the Gates ones the reinforcing is one thread wrapped spirally so there is no weak point in the belt
Cheaper belts are simply cut from a long roll & joined together then wrapped
While paying a lot does not guarantee a top quality belt paying a little guarantees a low quality belt
The only belts I fit come from my wholesalers and are Gates, Rotary, Stens , Prime Line or Oregon .
In 11 years of mower repairs I have never had a premature belt failure with any of them that was not my fault due to improper mounting .