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I have a Gravely ZT54XL (model 915188, serial 045147). I have had the mower for 8 years & it never broke a deck belt but in 4 days, I have broken 4 belts. When the 1st belt broke, I figured it was just age, the belt was 4YO & the grass was tall. When my mower was about 4YO, the bolt that secures the electric clutch to the engine shaft snapped, and when this happened the clutch was destroyed so I replaced it along with a new belt which was fine for 4 years and I saved the old belt because there was no visible wear. When I installed that belt, it also broke after about 30 minutes of use. The mower calls for an Ariens/Gravely 07200023 belt which is listed as a 1/2" wide by 145" long. When I searched Amazon for this # belt, it listed a "Kevlar" belt which was $45 with delivery the next day. When this belt failed, I figured something was wrong causing these belts to fail, but I ordered a 2nd belt (the same one from Amazon). This time I took a very close look at every drive pulley, idler pulley & the belt tensioner. Every one was completely tight with zero slop & spinning freely. The tensioner was fine, but I did order & install a new tensioner spring. One thing that I did learn in all of this is that when you order a Ariens 07200023 belt online, there are often what I consider to be some very significant dimensions in the belts sold from one brand to another, even if it is an American manufacturer that makes the belt (like Gates or Stens). Take the 1/2" width of the belt, if you convert 1/2" to MM it equates to 12.7mm. Most belts (not all) had an exact match in width for MM but not inches. The Amazon belt that I ordered was only 11mm wide (versus 12.7), most belts round up to 13mm, the Gates belt was listed as 14mm wide. The depths of these belts also vary as also that 145" length. In any case, what I am pretty sure is causing my problem with my belts failing is that between my idler pulleys & the engine driven electric clutch that the belt is turning on its side when I set my deck to its lowest (1.5") cutting height (which is the setting that I have always used). The clutch pulley sets rather high relative to the deck pulleys; it is the back side of the vbelt that rides the 1" wide flat face of the idler pulley. If you are sitting in the mower seat & consider the pulleys from that perspective, the belt rides on the right idler pulley (sending the belt to the clutch pulley) near the bottom, but it rides the left pulley all the way near the top. I believe that it is the edge of that left idler causing the belt to turn onto its side. I just swapped the right & left idler pulleys as 1/2 of each pulley was very shiny & worn where the belt rides & the other 1/2 was not. I was wondering if anybody ever had this problem & what they did to fix it. Does anybody think that replacing the left idler where the belt rides at the very top with a wider idler would correct this issue?

There is more to a V belt than the angle width, depth & length.
There is the size of the reinforcing strings and their position within the belt.
Some are stiffer than others and some will handlea lot more out of aligned pulleys before jumping off .
And the back of come belts are flat while others are concave and others still are convex .
But you can't tell the conspiracey agents that as far as they are concerned they are all the same and the branded belts are ripping them off.
So unless the tension pulley flange is worn excessively then you are just getting the wrong belts

bertsmobile1 said:

There is more to a V belt than the angle width, depth & length.
There is the size of the reinforcing strings and their position within the belt.
Some are stiffer than others and some will handlea lot more out of aligned pulleys before jumping off .
And the back of come belts are flat while others are concave and others still are convex .
But you can't tell the conspiracey agents that as far as they are concerned they are all the same and the branded belts are ripping them off.
So unless the tension pulley flange is worn excessively then you are just getting the wrong belts

Click to expand...

The latest belt that turned onto its side was a Stens True Blue 248-146 belt (with these belts, 238 is a 3/8" width belt, 248 is 1/2" & 258 is 5/8"; the 2nd # is the belt length in inches). I thought that was a very well constructed belt. I used it for about 45 minutes with the mowing deck at a height of 2" and the belt was running just fine, after a very short time after lowering the deck to a height of 1.5", it flipped. I understand your point about how the physical construction of the different belts varies. Another thing with the belts that I purchased from amazon that was very different was the fabric wrap used on the exterior of the belt. On that belt, if you ran your finger over that fabric, it was like no friction at all; after the belt was on, I was able to turn blades by moving them with my hand (with very little force) with the belt on & tensioned. With the Stens True Blue belt, all 3 blades move & it takes allot more effort to move them. I have a Stens 266-152 belt which is listed as a Ariens 07200023 belt on the packaging & a Gates 6793BR (Bladerunner) belt which is also listed as a Ariens 07200023 belt that I have not tried yet.

If OEM Parts are used you'll be a happy camper.
Bearings at center of 3 idler pulleys are probably worn out after 8 years, use OEM parts & let us know how it goes, thanks, Mark

You still bought a STANDARD A section belt, not an OEM spec belt .
The 265 series are the OEM spec belts and if you go to the Stens Refference Tables on their web page and download the "belts by lenght" pdf you will see that there are a lot of OEM belts that are exactly the same length & section , yet very different prices.
This is because internally they are constructed differently .
A mower that old will probably have some wear in the idlers and in the tension arm pivot.
Quality mowers have a bearing or replaceable bush on the pivot because it wears rapidly as it only swings over a very short arc and rarely gets lubricated by owners .
IT is always worthwhile to actually watch the belt and try to identify where the belt is actually running off the pulley and which pully is the culprit.

Final note is 1.5" is way too low unless you have cooch grass on a sand based putting green.
I have been doing my best to eduucate m customers that they should keep their lawns at 3"
Those who eventually listened have lovely soft green grass right now
Those who think the grass should be a "carpet" have sunburned dry brown grass that is full of weeds

I've found that once a belt rolls over like this , it will continue to do so, Make sure your idler pully is " floating " and not static

Bertrrr said:

I've found that once a belt rolls over like this , it will continue to do so, Make sure your idler pully is " floating " and not static

Click to expand...

Thanks. Do you think that the belt continues to keep rolling over because once it does this the belt gets burnished from running in the wrong position making it more prone to keep flipping? I'm pretty sure that it is the idler pully that the tensioner arm keeps the belt tensioned with. The bottom half of this flat faced pulley still has the galvanized coating & looks as if it had no wear at all. The upper half of this pulley & the shoulder are completely shiny which shows this is the wear from how this belt was running. All of the pulleys spin freely & there isn't any movement in any of them. All 3 idler pulleys are identical so I swapped the right & left pulley being as that the back side of the v-drive belt runs at the bottom of one (but not onto that shoulder) but at the top of the other (so the wear patterns on the 2 are opposite). I was going to replace the 3 blade pulley spindles which are an Ariens 07330267 part #. I ordered a set from Amazon that had this OEM part # but they were a smaller diameter, then I ordered a set from an lawnmower shop that sells OEM parts online & they were a smaller diameter, so I am wondering if I will go through that process with trying to order idler pulleys. I did buy a set of plastic v-belt pulley gauges which also includes a "A" belt V gauge. The V spindle pulleys really didn't look like this bottom picture, so I don't think that they were an issue. One of the articles on V-belts said that the angle on the "A" belts was supposed to be 40 degrees, the gauge set that I bought only had a 34 degree & a 38 degree gauge.

The STANDARD angle for a STANDARD section belt is 40 degrees
However deck belts are not STANDARD section belts
Now if you really want to know go to the gates Lawn & garden catelogue, look up your belt by ariens / gravely numbers and hopefully it will be there
Navigation paths > Vehicle Parts Search > Interchange then use the part number
Very rarely the angle will be 40 deg
Most deck belts are 4L or 5L sections , not A or B
Most belt retailers simply convert the actual size the the nearest standard size that they stock
The actual belt size is called the effective length which is the circumference around 1/3 of the way in from the back .

And Bertrr is correct.
Once a belt has rolled it is damaged internally so will continue to roll at the same spot