V-Belt Questions (images and video)

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JHZR2

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So from my other thread on the busted V-belt, I had gotten an OE Continental belt from BMW of Annapolis, and put it on today. I have been going off the 1/2 inch of deflection rule of thumb, so anyone want to watch my video and confirm I got it right?
I think it may actually be a bit tighter, as the belt in question goes around the fan, the main crank pulley and the alternator, and the alternator turns a little when I press it, no matter how hard I try to contain its motion. Anyway, I had only gotten one belt, thinking the others were fine. I put them on, they should last a while more. What is interesting is that the BMW OE Contitech belt has a different tooth pattern than the regular yellow Continental belts do. I did notice some slight cracking in the other two old belts. It didnt concern me that much, as for one thing, one is only for AC and the other only for PS... Not nearly as dire a failure as the fan, waterpump and alternator. On another note, the belt sits a bit high in the pulley. Is this OK considering that it is a new belt? Thanks!
 
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I would replace those other 2 belts as soon as possible. Both are worn out IMO. Your new belt looks OK, But I would run it for a day and then tighten to final spec.FWIW--Oldtommy
 
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I'm going to vote your old belts are fine for a while longer. Is your alternator pulley slightly out of alignment or is it a camera lens optical illusion? If the alt rides on rubber bushings that belt could indeed be too tight.
 

JHZR2

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Originally Posted By: 2oldtommy
I would replace those other 2 belts as soon as possible. Both are worn out IMO. Your new belt looks OK, But I would run it for a day and then tighten to final spec.FWIW--Oldtommy
id hope the new one looks OK smile What is the basis for saying the others are worn out? THe depth of the cracks in the teeth, or just the fact that there are some in view?
 

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Originally Posted By: eljefino
I'm going to vote your old belts are fine for a while longer. Is your alternator pulley slightly out of alignment or is it a camera lens optical illusion? If the alt rides on rubber bushings that belt could indeed be too tight.
YES!!! The alternator is on rubber bushings and the alternator always moves to be a bit crooked. I changed the bushings this spring because of the crookedness, and no luck. I could lighten the belt tension, but then it would move with greater deflection. This is my ages-old concern with my alternator!
 
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Are the bolts for the alternator and it's pulley tight? That looks way out of alignment! As far as tension, yea, that is the age old question! I've bought gauges, tried the deflection method etc. and it just never seemed right, so I go by feel. I tighten it until all the loose slack is gone and the tension feels just snug enough without being way too tight. Sometimes I'll close my eyes and grab the belt move it up and down to gauge the tension! If it feels too tight, loosen it a tad. Feels to sloppy, I'll tighten it a tad. I could never accomplish that with a gauge or measuring deflection.
 
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The Alternators on those older Beemers were always crooked! The other belts are worn out and need to be replaced asap. So what if they just run the AC or PS. When one breakes and knocks the other belts off your going to be stuck somewhere and have to replace all 3 anyway.
 

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Originally Posted By: Drew99GT
Are the bolts for the alternator and it's pulley tight? That looks way out of alignment! As far as tension, yea, that is the age old question! I've bought gauges, tried the deflection method etc. and it just never seemed right, so I go by feel. I tighten it until all the loose slack is gone and the tension feels just snug enough without being way too tight. Sometimes I'll close my eyes and grab the belt move it up and down to gauge the tension! If it feels too tight, loosen it a tad. Feels to sloppy, I'll tighten it a tad. I could never accomplish that with a gauge or measuring deflection.
But what am I feeling for? Sorry for being dense with this! Is it safe to say that a belt is tight enough when if you grab it on its longest length and pull it forward and back, it doesnt slip on its pulleys???
 

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Well I just tightened it enough so that I couldnt yank the belt and turn the alternator. Tried turning on loads and didnt hear a belt slip, so I guess that's good. 1/2" seems pretty tight...
 
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Usually the rule that I use, is I will push down in the center of the longest straight section and if I push with all my force and only get 1/3" of deflection, then it is tight enough. Remember that the belts will stretch after some use. And yes, the other two should be replaced immediately. The cracking mean they are getting tired.
 

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Originally Posted By: The Critic
I push with all my force and only get 1/3" of deflection, then it is tight enough.
1/3"??!? That's a tight belt... My alternator would be turned sideways!
 
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I like my belts just tight enough it doesn't slip. Without the awkward tension gauge, the measurement really is subjective. Take Critic for example... He says he uses all his force to achieve 1/3" deflection. Well, what he's built like Lou Ferrigno? That would be an insanely tight belt. What if he was a 90lb weakling that could barely pick up a wrench? What I'm getting at is trying to set/measure force by hand is tricky and changes with the person doing it. I would suggest that if that belt only ran the alternator, then loosen it up a touch, run for a day and re-check the tension. Probably by the end of the day it'll be squealing. If it is, then snug it until it doesn't anymore.
 
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Originally Posted By: JHZR2
Originally Posted By: Drew99GT
Are the bolts for the alternator and it's pulley tight? That looks way out of alignment! As far as tension, yea, that is the age old question! I've bought gauges, tried the deflection method etc. and it just never seemed right, so I go by feel. I tighten it until all the loose slack is gone and the tension feels just snug enough without being way too tight. Sometimes I'll close my eyes and grab the belt move it up and down to gauge the tension! If it feels too tight, loosen it a tad. Feels to sloppy, I'll tighten it a tad. I could never accomplish that with a gauge or measuring deflection.
But what am I feeling for? Sorry for being dense with this! Is it safe to say that a belt is tight enough when if you grab it on its longest length and pull it forward and back, it doesnt slip on its pulleys???
Don't go for forward and backward to see if it's slipping; it'll likely be too loose. Go for up and down like you're measuring deflection, but move it up and down to feel for slack with your thumb and your index finger in the center of the belt on the longest distance between pullies. It's easiest to completely loosen the belt, and then tighten it a small bit at a time and keep checking the tension like it's a guitar string. Once all the loose slack is out and it starts feeling like it's tensioned snugly but not like a banjo string, that's usually where I stop. You might need to recheck it, especially with a new belt, but this way, you can be more certain it's not over tightened. I'd rather it be a bit loose (but not slipping) and have to re tighten it later, than have it too tight and wear out accessory bearings. Or, maybe I'm more anal about belt tension than anyone else!
 
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Originally Posted By: doitmyself
Has anyone ever tried using a Gates Kriket v belt tensioner? Do they work?
They're useless IMO. I even went as far as to buy a Nippendenso gauge, and it also was junk. I couldn't get the belt to feel correct; it would always feel way too tight.
 
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When I've done belts on my old e28's and e30's I try to avoid tightening them too much. Of course I don't want them to slip or make noise or fall off but the more tension you put on the belt the more stress you put on those pulleys which are usually connected to some expensive (and old) parts. Loose > Tight
 
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Yes- the new belt will sit a little higher since there is more material than the old belt. As the belt wears, it will settle further into the pulley grove.
 
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