I just tried to change the belt on my M103 and found the new one was too long. It was about an inch longer than the old one. I tried to adjust for it and ran the adjuster off the end and it's still too loose. I got a new one and it's the same length as the other new one. I'm thinking my options are to try and buy a shorter one, or try getting a new tensioner. But I'm confused why this is a problem, but need to resolve it before my old one breaks.

It's for a 1991 190E 2.6 with 340,000 miles on it. I guess the belt is a 6K x 2415.

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5 speed '91 190E 2.6 320,000 mi. (new car, fast, smooth as silk six, couldn't find any more Peugeots)
5 speed '85 Peugeot 505 2.5l Turbo Diesel 266,000 mi. (old car, fast for a diesel, had 2 others)
5 speed '01 Jetta V6 (new wifes car, pretty quick)
5 speed '85 Peugeot 505 2.2l Turbo Gas 197,000 mi. (wifes car, faster, sadly gone just short of 200k )
5 speed '83 Yamaha 750 Maxim 14,000 mi. (fastest)
0 speed 4' x 8' 1800 lb Harbor Freight utility trailer (only as fast as what's pulling it)

In the belt world, a 1 inch difference is huge.

Get a shorter belt.

Jim

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14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles

What is the brand of the belt? I had the same issue with a Dayco belt but that may have been because my tensioner was shot and it stretched.

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Current: 1975 450SEL, 83 300D, 88 Yugo GVX, 90 300D OM603 swap, 91 F150 4.6 4v swap, 93 190E Sportline LE 3.0L M104 swap, 93 190E Sportline LE Megasquirt, 03 Sprinter, 06 E500 4Matic wagon.