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)