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Belt dry rotted or overheated?

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Belt dry rotted or overheated?

Postby Mr Mower Man » Thu Sep 13, 2018 11:28 am

I replaced an engine-to-deck belt on a Swisher ZTR 3 months ago. Customer calls me yesterday to say the belt came off, and it's dry rotted. I asked her to send me a picture, which I couldn't quite figure out how to share with you all on here. It looks kinda dry rotted, but I also wonder if it's just been burned. It has lots of cracks in it, much like an old belt would, but I'm thinking heat damage from being burned by a pulley might do the same thing. But this belt has only been in service for 3 months, after I ordered it from my distributor that carries Swisher OEM parts (Oscar Wilson in Missouri).

The reason I suspect heat damage is because I wasn't able to get the belt very tight. It squeals a lot every time the electric PTO is activated. I adjusted the spring tension as much as I could when I replaced the belt 3 months ago, but it still wasn't very tight. In my opinion, the spring is too weak, weaker than other springs that do the same thing on other brands of mowers. I'm thinking tighter belt tension would improve this situation, or else maybe Swisher belts are junk and I need to try an aftermarket belt from Oregon or Gates or something.

Any insight from you all?
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Re: Belt dry rotted or overheated?

Postby hanz63 » Thu Sep 13, 2018 9:19 pm

I kind of get what you are saying, but I've not ever looked at a belt and assumed dry rot as a characteristic of a failed belt. In the end, you will have to do an inspection of what you have as far as the condition of the deck. IE belt alignment, proper belt being used, bearings causing an extra load plus how they are using the machine. If you don't have one, an infrared thermometer is great for comparing bearing temps in a situation like this. Swisher belts I've used have been fine. I have a strong dislike for OEP spec belts. Gates greens are a tough belt. A hundred years ago I worked at a dealer who also sold Swisher. At that time, they were good enough to answer the phone and help you out. Maybe they changed a tension spring or belt spec in your situation.
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Re: Belt dry rotted or overheated?

Postby bgsengine » Thu Sep 13, 2018 9:43 pm

Mr Mower Man wrote:The reason I suspect heat damage is because I wasn't able to get the belt very tight. It squeals a lot every time the electric PTO is activated. I adjusted the spring tension as much as I could when I replaced the belt 3 months ago, but it still wasn't very tight. In my opinion, the spring is too weak, weaker than other springs that do the same thing on other brands of mowers. I'm thinking tighter belt tension would improve this situation, or else maybe Swisher belts are junk and I need to try an aftermarket belt from Oregon or Gates or something.

Any insight from you all?


The above was your first mistake.. generally if your instinct is telling you something ain't right.. then something ain't right.. I'd have dug a bit deeper - check belt mountings? Idler arm brackets (that the spring tensions) have been known to develop "detents" - wear spots that stop it from having a full range of movement (not to mention rust can do the same thing.. if you spot telltale rust oxides around pivot points, do yourself a favor and disassemble and clean, repair and/or relubricate) , springs can be weak they can also be hooked into wrong holes (sometimes the most obvious hookup is not always the right one) , pulleys can be worn enough that the belt fits too deeply into the V groove and becomes loose (Many customers call it a "stretched" belt, but most belts do NOT stretch (they can't its the kevlar cording that determines their length, if that breaks, you got a broken belt even if the belt looks whole) But belts DO wear the sides and sit deeper in grooves, making them "seem to" stretch even if they look fine) Almost never see dry rot on belts unless they have been sitting unused for many years - so your other instinct would be correct and it is heat damage.. but the cause of the damage is most likely gonna come back on you, its gotta be found and fixed , or further belts (I assume you checked the belt to verify it actually IS OEM... Believe it or not, but even factory authorized distributors are well known for substituting aftermarket in place of factory OEM (comes from the same manufacturer, same production line, same stuff, just doesnt get to go through the OEM's quality control checks)

So, I would say your first order of business is to diagnose why the belt seemed loose.. Bear in mind any mis-alignment of the deck mounting in relation to the mower frame (or even engine mounting bolts, has engine every been out, and maybe bolted in to the wrong place?.. things like that) - can cause the deck to sit in such a way that belt will be loose (all mount points checked? deck checked for level? all pulleys checked for correct sizing? service history? new PTO clutch that might have a wrong pulley, or an updated pulley needing a 5/8 belt where a 1/2 used to be? Bent spindles, bent deck (making spindles orientation change) ? many many things to check..
How poor are they who have not patience. What wound did ever heal, but by degrees? - Iago (Othello Act II, Scene 3)
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Re: Belt dry rotted or overheated?

Postby KE4AVB » Fri Sep 14, 2018 3:35 am

Have to agree with Brian on this. If something is telling you it is not right most likely it isn't.

And sometimes the belt are simply the wrong length which something I have been fighting over the last year and half now. Even Stens are sending out OEM Spec'd belts that are the wrong lengths now. Two weeks ago I ordered 1/2" x 103" deck belts and got 104". Even the 103" that I have is too long and I ended up using a 102" Kevlar belt. Now the belt that came off the deck did measure 103" but was a 9/16" instead of 1/2" and definitely wasn't a 5/8". Thursday I got in an OEM Spec'd 5/8" x 64.5" from them that that is 5/8" x 63.75". The worst of it is our belt suppliers are trying to send out 1/2 for 9/16 belts. As Brian said they fit deeper in the pulleys and actually bottom out causing slipping. I even a few years where one Cub Cadet belt that was 7/16 that everyone was subbing a 1/2 belt and there was simply no clearance at the engine for it to have its air cushion when disengaged. I finally ended buying the OEM belt. Also make sure someone hasn't sub a poly belt for Kevlar or Aramid belt. I had an after market vendor that that sending out Poly in place Kevlar belts last year. Also be aware that those import belts only have about a 1/10 of the life of the US made belts.

Now as Brian also said check all the pivots, pulleys, and bearings. Also verify that the correct spring is installed. Yes customers and other techs simply replace a broken spring with what ever was handy or installed incorrect pulleys. In general decks can be a real pain sometimes. Heat can occur several ways too; two of which are too loose and too tight. You actually burn the belt if it is too loose from slippage. When too tight they over heat and with Poly corded belts actually melt the cords. Overheated belts also have a tendency to roll over as they soften.

With the problems caused by these manufactures is enough to make me to want to quit this business. No wonder I buy aspirin 200 tablets at a time now. I still trying to make it to 2025 before I give up. Sometimes I would just love to hang up the salesmen by their toes.

I just had a go around with Stens Thursday afternoon about sending me 3 point spindle shafts when they told me that they were 6 pointers. I called Stens before ordering them. I have problems the 3 point ones and these that I got yesterday will not even fit the 6 point MTD blades; unless, I press them on. Now I got to order the MTD ones and throw out the junk Stens shafts. They simply lied to me when I called about them. If they had told me the truth I would have never ordered them. They just lost most of their sales to me.

It all comes down to trusting yourself and not the vendors lately. They are just selling parts and don't care if you get the wrong parts.
The truest measure of society is the how it treats its elderly, its pets, and its prisoners.
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Re: Belt dry rotted or overheated?

Postby Mr Mower Man » Fri Sep 14, 2018 10:01 am

I did a lot of this checking last time I had it. I'd like to look it over again, but I'm pretty sure everything's OK as far as pivots, pulleys, etc. The only pivot problem was the v-idler/flat idler belt tension arm, which was a little bit sloppy at the pivot, and I replaced those pulleys. But with my experience, I say it wasn't bad enough to cause this problem. The spring is my biggest concern. The tighter I made the adjustment and stretched the spring more, the tighter the belt got, but I still didn't think it was tight enough. I feel like spring tension is causing the issue. Too loose, and it burnt the belt. Perhaps someone changed it in the past and thought "a spring is a spring." And yes, the belt I got was a Swisher OEM belt. At least that's what the sleeve and numbers on the belt led me to believe.
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Re: Belt dry rotted or overheated?

Postby bgsengine » Fri Sep 14, 2018 10:15 am

Mr Mower Man wrote:The only pivot problem was the v-idler/flat idler belt tension arm, which was a little bit sloppy at the pivot,


2 things - You'd be amazed how much difference even 1/16 inch of wear in the pivot can make in belt tension, and also make sure you check for pivot slop at the point where it would be if the idler arm was in its normal operating position . a little slop with no tension would set off warning bells to me,I'd remove the idler arm and pivot and check it physically for out of round and pivot bushing wear. just a 1/8 inch difference in some can translate to a half inch or more of belt slack, which can be a huge amount.
How poor are they who have not patience. What wound did ever heal, but by degrees? - Iago (Othello Act II, Scene 3)
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Re: Belt dry rotted or overheated?

Postby Mr Mower Man » Fri Sep 14, 2018 10:28 am

I wanted to replace the arm because of the slop, but nobody had one, and the customer needed the mower back. But the customer has a backup mower now. So I'm gonna order one of those, a new belt, and also a new spring in case the original got weak.

I'm not thrilled with this weak-looking spring. https://www.swisherinc.com/pub/media/documents/12935_REV_09_026.pdf Scroll down to page 26, and you'll see the breakdown of the tensioner assembly on the bottom left corner of the page. See that spring (ref. 20)? That's exactly how it really looks.
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Re: Belt dry rotted or overheated?

Postby 38racing » Fri Sep 14, 2018 10:35 am

I sold a rider to a friend and I had replaced the drive belt . after 3 months it broke. He did say he had gone into long grass. When I was getting a new belt I concluded that MTD had an error in the ipl and the belt I put on was 79 ". The correct one is 78. He got the 78 on fine and is cutting with it. I'm guessing the looseness was cause of early failure.
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