Krikit belt tension gauge

I'm getting ready to replace the alternator belt on the Miata after I ignored its cold slipping to the point it departed the vehicle, never to be seen again.

I understand how to measure belt deflection, that's intuitive. You press on the belt with X pounds of pressure, measure how far it moves. Simple

I don't get how these supposedly-common tension testers work. The Miata factory service manual has different tables for deflection and tension values, and they're radically different.

Instructional video

It almost seems as if the clicking finger pad is set to pop at a certain force, and deflection is measured over the distance from the bottom apex of the little indicator lever to somewhere else. But this seems to pre-suppose several variables that I can't articulate.

Can anyone explain to me what this thing is actually measuring, and how?

It measures the tension in the belt, and it works great. For exactly how, you're going to have to break the physics books out and play with lots of numbers.

4 cyl Lotus Esprit owners use the Krickit gauges almost exclusively to set the tension on the timing belts. If you screw it up, it's Game Over on that motor. I've got one in my tool box. Don't have the Esprit (RIP) anymore to go with it.

Dr. Hess wrote: It measures the tension in the belt, and it works great. For exactly how, you're going to have to break the physics books out and play with lots of numbers.

Yeah, that's what I'm interested in I guess, the physics lesson. I refuse to believe that the hive-mind can't explain this!!

If I understand correctly the device measures belt deflection at a set pressure (the click) it extrapolates this to tension on that scale, determined with a predetermined belt stretch factor.

I have been curious how well (accurate) these work due to the assumptions built in on belt stiffness.

Peter- can't explain how it works, but I can say that every belt I've used it on with my many Miatas stopped squealing after I set them with it. And squealing belts have been a price reduced on more than one Miata that I have bought over the years.

Just did mine yesterday. Worked great. Didn't try to think too hard about HOW it worked so great. I'll have to pull it back out later.

hmmmmm, how would that work on a timing belt when you have a deflection amount, and then at that deflection it should take a certain amount of mass to reach it.....

for example with a 4AGE....

By the way... you have no idea how many people get this wrong......

OST, with something like that 4AG, you could use the Kricket to check it after you kinda "calibrate" it. That is, do the test on one set up properly at 4mm at 2Kg, then put the Kricket on the belt and check the tension it reads at. Going forward, that would be the measure you're looking for.

HINT: It's probably about 45-50 on the Kricket.

I used the Krikit on my alternator/water-pump belt on Sunday after biking 30 minutes to my stranded-at-work Miata on Saturday, only to realize I'd left the keys at home.

I did several tests in different locations before deciding I was within spec. The motion is subtle enough that I had very little confidence in the results. Not a peep out of the belt though and the charging/cooling systems appear to be working great, so job done.

Money well spent.

I just ordered one of these. I haven't watched the instructional video yet, but from the picture above I can't tell how to use it much how it works. I figured for $11 and free shipping I'd buy one and see how it works. Will make a good stocking stuffer.

Biggest problem I've had with various belt tension gauges is getting them in there to use. From lack of distance between pulleys to inaccessibility.

I've always checked and set belt tension by hand. It's never failed me yet. I find the longest run between pulleys and set it to have about 0.5" in either direction with my calibrated arm.