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Belt Tension

R

rcnerd

NAXJA Forum User
Location
Calgary, Alberta, Great White North
Just wondering what people's thoughts are around belt tension.

Of course the "right" way to set it is with a tension measuring tool, to the proper spec, however I think that the proper spec is on the tighter side of things so that it WILL... NEVER... SLIP even though bearing (idlers, alternator) and water pump and belt life may be sacrificed.

I've found that the belt works really well at way too loose of a setting, and that if it ever does slip due to stretching or water or whatever that is such a quick and easy adjustment to make that it being on the looser side of things seems fine.

I'm theorizing that the decreased tension will reduce loads on bearings and bushings and reduce the heating of the belt from friction, as long as it is tight enough not to slip.

What does NAXJA think?
 
So it NEVER slips is the correct tension. Anthing less causes slipping and heat which will cause the belt to fail FAR sooner than any heating the belt may have from friction. I've never felt any heat from a correctly tensioned belt. The only time I've felt heat is when a belt has slipped.

You will only see increased wear on the water pump/idler/alt bearings if the belt is VASTLY over tightened. Other wise from a correctly tesnioned belt you should get many many miles of service from the bearings, like 3 or 4 belts worth. I've changed many alt from worn out brushes but only one from failed bearings.
 
rcnerd said:
Just wondering what people's thoughts are around belt tension.

Of course the "right" way to set it is with a tension measuring tool, to the proper spec.
Click to expand...

You should have stopped there.
 
Hi cLAYH, fancy meetin you so far from home!

So as long as it never slips it's tight enough?

Or only if it's set to spec with a tension checker?

I've never worn out an alternator in the normal sense in my jeeps, it's always shot bearings, usually the rear one oddly enough.


Oh and to clarify...when I said WILL...NEVER...SLIP...I meant like, tight enough not to slip for years of use...as opposed to a setting where it never slips or squeals but where it wouldn't be too suprising if it needed to be adjusted a few months down the road.
 
Last edited:
New belt 180~200 ft lbs, with a gauge.

Used belt (any belt after 15 minutes of operation) 140~160 ft lbs, with a gauge.

How close can you get to that with your "engineering eye"? (That was my Dad's description for not doing something right.)
 
joe_peters said:
How close can you get to that with your "engineering eye"? (That was my Dad's description for not doing something right.)
Click to expand...

haha well put! :laugh3:

I recently tightened my belt... I was getting some squealing at cold start... I just turned the adjustment bolt a few times (maybe 4-5 turns??) and hasn't made any noise since.

JW- how do you know if its tooooo tight?? If its too loose, it slips/squeals. Whats the indication for tight, if any?
 
4WDlifeform said:
haha well put! :laugh3:

I recently tightened my belt... I was getting some squealing at cold start... I just turned the adjustment bolt a few times (maybe 4-5 turns??) and hasn't made any noise since.

JW- how do you know if its tooooo tight?? If its too loose, it slips/squeals. Whats the indication for tight, if any?
Click to expand...

Find the longest run in the belt (area where the distance between 2 pulleys is the greatest) and twist the belt. By just using two fingers, if the belt twists more than 90* its too loose, if you fight to get it to 90* then its too tight. Thats the way i've always done it and have never had problems.
 
xjchris98 said:
Find the longest run in the belt (area where the distance between 2 pulleys is the greatest) and twist the belt. By just using two fingers, if the belt twists more than 90* its too loose, if you fight to get it to 90* then its too tight. Thats the way i've always done it and have never had problems.
Click to expand...
x2
This is twisting the belt forward or backward, not trying to tighten the belt with your fingers.. lol .
 
Seriously, it would be fun to line up 5 or more XJs and have a two guys do the 90 degree adjustment on all of them, and then to check them with the appropriate gauge and see how close they were.

Put this on the agenda for your next "meet and greet".
 
That s a great point! They all will be different cause some people are stronger or bigger than others. I would put money on the fact that there would be some major difference between the 5 rigs. Thanks for talking me in to buying the proper tool.
 
winterbeater said:
Why hasn't somebody come up with a spring loaded idler pully like most vehicles have?
Click to expand...


Ya for shore. And if exact tension is so important why do those spriong loaded tensioners even work....they must get looser and looser over time, no?

I've always thought that the spring loaded tensioners I've played with (chev trucks mostly) seemed a lot looser than spec by a tension tool, but I've never checked it.

I'm definately going to pick up one of those krickit II's though!
 
My previous rig had one of them spring loaded tensioner... they are no good. Im much happier with the XJ's system, especially for wheeling. The slightest bit of mud destroyed my tensioner every time. Sometimes all I had to do with the thing was unload it, then put it back on, and it would hush up for a bit. Never really seemed to keep the belt tight enough even with brand new ones. Nothing more embarrassing on a rig than a squealing belt IMO.
 
winterbeater said:
Why hasn't somebody come up with a spring loaded idler pully like most vehicles have?
Click to expand...
I like those for street driving, and pure simplicity of changing the belt, but they wear out. We used to make a pretty good chunk of change installing those at the quicklube I worked at. The coil spring and bushing in them tend to wear out, so the tensioner sags sideways and chews up the belt just like a bagged-out harmonic balancer.

Also, can I just say that I really hate that stupid knuckle the tensioner bolt on the XJ goes into? I've never worked on an XJ that didn't have a frozen tensioner bolt, and the only reason I didn't end up walking to the junkyard on my first one is because I felt the bolt starting to give, chickened out, and bought a spare at the junkyard before screwing with it more. Sure enough, the old one broke.

Why didn't they use a material that wouldn't freeze solid after a few years? Would have cost about the same...
 
At least with a spring loaded tensioner, it keeps the same tension on the belt as it wears and lengthens a little. Never had any wear out on my Fords with over 100k miles on them. Never did any serious mud dipping with them though.
 
winterbeater said:
At least with a spring loaded tensioner, it keeps the same tension on the belt as it wears and lengthens a little. Never had any wear out on my Fords with over 100k miles on them. Never did any serious mud dipping with them though.
Click to expand...

Replaced a bunch over the years, I just consider them another maintenance item.
 
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