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#1
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Belt Tension
So I got one of those "KriKit" belt tension gauges, which seem to be fairly well thought of by most as far as accuracy goes. Tried it out on a my belts ... and it appears they need to be WAY tighter .... and WAY tighter than I would have ever thought, or have ever tightened them in the past.
I was getting some squeal when I revved the engine ... so I know they were too loose ... but I didn't think they were that loose. Basically I'd have to use a small pry bar to get the alternator belt tight enough according to this gauge. I've seen them tested in videos ... they do perform pretty well and are even recommended by Gates. Any thoughts ... other than buying a $150 Borroughs type gauge?
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#2
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I picked one up recently and had the same observations. For me it became a tool to numerically indicate how much tension I had and I ramped up tension until my squeal went away not necessarily making it all the way up to the factory identified value. Everything else I torque to spec, this is the first time I've ever looked at belt tension values and need a little time to get used to that level of tightness feeling "right," I figure if the belt doesn't slip it's good enough for my needs.
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#3
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That's my reasoning too ... why tighter than it needs to be.
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#4
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I teach Drives as part of my job. A good rule of thumb for v-belts is 1/64" of deflection per inch of span. This is subjective because of how hard you pull on the belt. Use a long straight edge (on edge) and a machinist scale, or tape measure, to check the deflection. Just pull with moderate force until you feel all of the slack come out of the belt. Like you guys said, sneak up on it. Belts are a lot cheaper than components. Just enough tension to prevent slippage. Power steering pumps have bushings. They don't tolerate loads as well as bearings. Be especially cautious here. Alternators have small bearings. They can get smoked easily too. I had a lot better results after I bought CVF pullies.
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#5
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The deflection measurement is also affected by how much force is applied to the spot that you are measuring. Did the deflection have a specified force.
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If you built it, drive it. red 62 Tempest total stock restoration. white 62 Tempest modified, 61 389 Tri-Power, and a conventional drive train. |
#6
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Quote:
While there are methods to measure EVRYTHING you must have EVERY measurement to do it. I stick with the old Greman way.....gootntight. Actually, I made a serpentine system for mine and let the GM tensioner do it's job. |
#7
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The tool I was using has a built in pressure indicator .... much like a clicker torque wrench, you press down on it till it clicks, then read the indicator. Very simple little tool. I get very consistent readings with it ... just indicates I should be WAY tighter than I'm comfortable with ( using the service manual specs).
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#8
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Overtight is a good way to take out the Alternator bearing or the Water Pumps bearings.
Tom V.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#9
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We used the v belt "twist" on a span over 1 ft. Only twists 90 degrees. All these adjustments, no matter how scientific you get, are just Static. Obviously the pulley providing torque will have less tension on the output side once it goes Dynamic. Equalize it best you can so it works, and its quiet.
Belts wear, pulleys are not perfect, and there are different specs for worn belts, vs new. Belt twist works... but , of course anything can be discussed , and discussed again.. Ps. Some repop pulleys are NOT round....
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#10
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Bottom line is there's no perfect way to tension a belt. There are different profiles, spans, rubber composition, cording, notched/tight radius, etc. The deflection method gives you a good point of reference and gets it close for most applications. You could use a spring scale to be more accurate and consistent. If you're experienced, you probably know by feel.
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#11
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I've always just gone by feel and have never had a problem. Tighten them up to a reasonable, moderate tension and call it good. Doing it by feel is of course subjective, but if you think it feels too tight, it probably is.
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1966 Pontiac GTO (restoration thread) 1998 BMW 328is (track rat) 2023 Subaru Crosstrek Limited (daily) View my photos: Caught in the Wild |
#12
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That's the method that's worked for me my whole life ... but wanted to give the service manual specs a try, they specifically call out a Burroughs gauge .. so maybe that would read different than what I'm getting.
So, back to the calibrated wrist method that I normally use
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#13
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Tried & true!
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1966 Pontiac GTO (restoration thread) 1998 BMW 328is (track rat) 2023 Subaru Crosstrek Limited (daily) View my photos: Caught in the Wild |
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#14
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I bought my first Krikit in about 1992. Wore it out, bought another. And one for Serpentine belts, too.
If they're used properly, they're a fantastic tool. Too many folks roll their finger on the pressure button, biasing the tool to show higher deflection than it should. V-belt tool https://www.amazon.com/Gates-91107-B...d=E04SLXHWT9QG Serpentine tool https://www.amazon.com/Gates-91132-B...d=E04SLXHWT9QG Although, I got mine at NAPA. |
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#15
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On the Alternator belt, just try to turn the alternator pulley, if you can turn it, its not tight enough. I think pulleys get worn and Too Smooth. I bead blast them to give them a little surface to grip the belt. Rusty pulleys will eat a belt! so they need to be clean!
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#16
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Quote:
There is no way a belt will hold on a worn pulley. |
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#17
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I've got a theory folks .... the KriKit tool specified "V" belts .. I have the notched V belts, notched on the point of the V .... I have a feeling these belts deflect far easier with a point load than would a non-notched V belt .... kind of like notching the bottom of an I-beam .. it's going to deflect WAY easier under a load.
So I think the KriKit is reading a much lower tension than it would if used on a conventional solid V belt. I can tell the tool is working the way it should, very consistent repeatable results, I just don't think it's designed for use on the type of belt I have installed. The sell various models for different types of belts. Just did some reading and the notched belts are designed for additional flexibility ... so of course they would deflect easier and read looser on a gauge.
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I'm World's Best Hyperbolist !! Last edited by dataway; 05-01-2022 at 11:59 PM. |
#18
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Maybe.
The main thing affecting deflection is going to be the tension on the belt cords, not the notches on the underside or the top of the belt. |
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#19
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Quote:
I've heard of people sanding, 'roughing', blasting, pulleys etc, but I rarely have seen that to work. As previously stated, if the groove is worn, the pulley is toast. Also true ALTs have small bearings, and overtightened belts can wipe any or all accessory bearings. I've always used the 'feel' method, but sadly, that can be a longer learning experience for some. If the ALT belt slips, it super-heats the pulley, hence the shaft and bearing = Toast. Once a belt slips, it's toast. Hopefully I don't need to type that twice. If it slips, change it. And that means even if it doesn't squeal. If you're putting a new ALT on, no matter what the condition of the belt is, change it. Or any accessory for that matter. I've seen timing covers that have been 'surfaced' on the mating sides, which can cause minor belt misalignment, that too is a potential problem. If you have an old cover, don't even think about putting it on your new build, just buy a new one. .
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#20
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When I was researching info I was surprised to read that belt manufacturers say more bearings are destroyed by loose belts than tight .... yes, due to overheating the pulley/bearing.
Noticed also that deflection specs, all things being equal, is higher for "cogged" V belts than non-cogged V belts ... so my guess that my gauge reads light. I don't think I've ever had a belt or bearing failure ... but I sure was curious to see how my calibrated wrist compared to an actual tension gauge.
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