Quick verdict
A spring gauge from OTC, the professional automotive tool maker, that hooks over a V-belt and reads its tension in pounds, so a mower deck belt, a drive belt or a riding mower PTO belt can be set to the figure in the manual instead of by feel. A loose belt slips, squeals and glazes; a tight one wrecks spindle and pulley bearings. The gauge reads both and suits any belt with a span to measure. It is a specialist tool that most owners of riding mowers never knew they needed.
Strengths
- Reads belt tension in pounds against the manual figure
- Prevents the slip of a loose belt and the bearing wear of a tight one
- Works on any V-belt with a free span
- Professional OTC quality
- Also for car and tractor accessory belts
Weaknesses
- Many mower manuals give deflection, not tension; conversion needed
- Needs a free span of belt to hook onto
- A specialist tool used a few times a year
The overall YardToolLab Score is out of 100. Section scores are out of 10.
Tight Enough, Not Too Tight
A riding mower has a deck belt, a drive belt and often a PTO belt, and every one of them has a tension the manual specifies and the owner sets by thumb. Too loose and the belt slips, squeals and glazes; too tight and the spindle bearings take a load they were not built for. OTC’s 6673 is a spring gauge that hooks over the belt and reads its tension in pounds, from a maker whose tools fill professional workshops.
This review is based on the maker’s specifications and on how belt tension gauges are used on outdoor power equipment generally. We have not used this gauge ourselves.
Using It
Find the longest free span of the belt between pulleys. Hook the gauge over the belt at the middle of that span and press until the gauge indicates, then read the pounds. Compare with the manual and adjust the idler or the tensioner. Re-check after the first hour of running, since new belts stretch.
Deflection Versus Tension
Many mower manuals give a deflection, so much movement under a thumb at the middle of the span, rather than a tension in pounds. The gauge still helps: set the belt to the deflection, read the pounds, write it down and from then on the gauge repeats that setting exactly without the guesswork of a thumb.
What It Prevents
Belts that burn through in a season from slipping. Spindle bearings that growl and seize from overtension. Pulleys worn by a belt riding wrong. For a riding mower with several belts, the gauge pays for itself in one avoided spindle.
Build
OTC makes gauges for automotive accessory belts, and this is the same quality. It is a small steel instrument that lasts a lifetime in a drawer.
Who Should Buy It
- Riding mower and zero-turn owners who change their own belts.
- Anyone who has burned through deck belts faster than they should.
- Home mechanics with tractors, cars and compressors on V-belts.
Common Owner Complaints
Manuals that give deflection and belts with no free span. Convert once; measure where you can.
Technique Tips
Measure a new belt and again after the first few hours of running, since new belts seat and stretch and the second reading is the one that matters. Write the pounds figure for each belt on a label inside the engine cover so next time there is no manual to find. Check the belt is seated in the pulley grooves before reading; a belt riding up a groove wall reads tight when it is loose.
Alternatives to Consider
A Krikit gauge for a simpler deflection reading. A sonic tension meter for professionals. A thumb and experience, which is what this replaces.
Verdict
For belts set to the number rather than a guess, this OTC gauge is the professional tool at a home price. Read the free span, set to spec and the belts and bearings last.
Full specifications
OTC 6673 Universal Belt Tension Gauge FAQs
A deck belt too loose slips under load, squeals and burns; too tight it loads the spindle bearings and the engine pulley until they fail. The manual gives a figure and the gauge hits it.
Hook the gauge over the belt at the middle of its longest free span, press until it clicks or reads, and compare the pounds with the specification. Adjust the idler and re-check.
Many do. A rule of thumb converts, or use the gauge to set a known-good tension and note the figure for next time.
It is designed for V-belts. Flat serpentine belts use a different gauge.
