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Old 03-12-2012, 09:05 AM   #1
Scooby Newbie
Member#: 313179
Join Date: Mar 2012
Default alternator belt tension?

What's the best way to tell if you have the right tension on your alternator belt? I replaced my belt 4 months ago and made a tick mark off to the side to annotate where the old belt tension was that way I didn't have to mess with it. Well when I put on the new dayco belt and tightened it up to that mark that I made it seemed a little tight so I loosened it down. I took my car into the shop a couple of days ago to get an oil change and they said the belt was kind of squealing, so they adjusted it for me, and they brought the tension up to the sharpie mark i made. How can I tell if it has the 1/4'' of play in it? It feels a little tight. do i push up and down on the top or on the side?
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Old 03-12-2012, 11:02 AM   #2
Scooby Specialist
Member#: 78165
Join Date: Dec 2004
Chapter/Region: South East
Location: SC
05 STI 35r + e85


I have always tightened it until I can twist the belt 90 degrees at it's longest stretch.
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Old 03-12-2012, 11:06 AM   #3
Scooby Guru
Member#: 37359
Join Date: May 2003
2003 WRX


Not sure if this is the correct way, but I did the folllowing:

- Find the middle of the longest run between pulleys
- Hold a small ruler against the belt with one hand
- Push the belt in with the other hand and see if it deflects by 1/4"

The hardest part is keeping the ruler fixed while pushing on the belt. I braced my ruler-hand against something solid.
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Old 03-14-2012, 12:48 AM   #4
Scooby Newbie
Member#: 311923
Join Date: Feb 2012
Chapter/Region: VIC
04 STi


i tighten just until you can't twist the belt 90 degrees. there are also belt tension gauges available!
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