dual alternator pully with two same belts (one tight one loose)
 

What do you guys think?? I just put my dual alternator pully on and I went to autozone to get new belts and made sure they where both the same manufacuterer and length however when I put the belts on and tighten my alternator one belt is longer than the other. The differance is enough that one is tight and the other one is still very loose. I changed the belt in back (loose belt) to in front and then the front was loose so I know it is that belt not the possistion in witch they are. Could this happen though the same manufacturer same numbers and everything and still they are not the same size???

I guess you just proved it can happen.

When you hold them in hand & stretch them can you see any size difference?

Mine didn't fit exactly the same because of pulley wear, but they were pretty close.
I plan to swap them front-to-rear after they break in, to try & even out the pulley wear.

I figure in about a year my fan clutch will wear out and I will be switching to an electric fan anyway.

thats the funny thing. when I stretch them out they look to be the same size. I put them on the smoke stack of my big cast iron bbq pit and stretched as hard as I could and they looked like the same size but when I put them back on the alternator one is loose. Now I could emagine something is out of spec. but if this where the case wouldn't like the rear or front belt always be loose no matter witch one I put where??

These are both brand new belts, right???

yeah brand new just got them yesterday and they are both the same manufacturer and same part number.

I think I'm just going to take the loose one back and have them get me another one because maybe someone road on it for a while and brought it back causing the belt to stretch a little.

OR the bottom pulley wear is uneven.

ok lets say for shits and giggles that it is uneven bottom pully wear. wouldn't that mean that the one that is uneven would always have the differant sized belt??? However when I change the belts around the longer belt then moves from the rear to the front so it can't be the pully right?

I think I'm going to buy another one of the same brand and don't return the two yet until I find out wich one works afterwards returning the one that doesn't work.

Oops - I missed that the loose condition moved with the belt.

(nevermind the pulley wear idea)

I bet you get the typical parts store response.
"It's not the wrong part. It's the right part in the wrong box"

Dude... get two DAYCO belts.... I got two cheapo-s and the exact same thing happened... Took 'em back and got two Dayco's and STILL one was just a bit looser than the other, but not drastically.. After 500 Miles, I re-tightend the altenator and now both are the same tension.

the tollerances for V belts are pretty wide... why??? well, because they are designed to be individually tensioned so being 0.5cm off doesnt normally make a differance... That is... 'till jackass RX-7 owners like myself start ripping shit out of thier engine bay and run two belts on the same circuit so their water pumps don't slip!!!!!

I'm waiting for more feedback on guys that have put the tweak-it "Gilmer Drive" kit on their cars cause, logically, a toothed, geared belt isn't going to slip and would need less tension to operate.

i had this happen, too. i bought two (if i remember correctly) Mazda part number belts (specifically made for? and) sold for Formula Mazdas. one belt was SO much tighter than the other. it was so rediculous that i only ran one belt. i ran like this for awhile, but months later, during rebuild, i used two different belts. i believe i ordered them from Atkins. they werent a brand i knew, but they fit well.

I used two different brands of belt in the same size and although I didn't notice a difference in tension I could watch one belt chase the other around as the engine was running.

No matter how hard you try it's unlikely you will ever get V-belts to fit the same. They ride in a V so the length might be the same but if the thickness of the belt or the pulley is slightly off, the belt path will be a different distance for each belt.

It's just the way it works. You might come close but you can't get it perfect.

ed

when the tight belt streches out it will fix your problem. Most belt maufactures tolrances are like 1-3%. Actually I'm surprise how few people have this problem.

Thanks everyone for you input. YOD that is exactly what I was thinking about them having liberal tolerances because like you said they are made for single pully in mind. Anyways would you guys just suggest me using the tighter belt until it is stretched out and then put the longer one in afterwards?

I just got a reply from 1badtii and I'm going with the Gilmer drive from www.tweakit.net when I tear the car down in the winter to do some more mods

damn that is one bad pully kit! Good lord! I don't think I need all that but I would love to see your engine after that mod daymnn!!! I didn't even know they made that for the rotary :)

i think its mazdaracing.com that also made a kit. i found it on ebay and went to their site. it was cheaper and looked decent (to my inexperienced eye).

$250
http://www.mazdaracing.com/pulleysystem.asp

Nah, this shit happens to a lot of us...I ended up running one belt like Casio. Dayco belts are good.

That ones good too... but different type.... that's a 6-ribbed belt... the Tweak it is a toothed gilmer drive belt..

And the gilmer drive is 260 in american dollars!! (shipping from australia, however, can't be cheap!!!!)

YOU BASTARD.... I had my mind made up... but now I'm thinking about the advantages of a 6-rib belt.... aarrrrgggg

you need a matched set of belts, they need to have the same run numbers which are the small numbers that usually go across the belt sideways. v- belts are available in matched sets from some companies, but most parts stores don' t carry them or realize that this is criticle in a dual belt set-up.

save your money and find an industrial belt supplier in the yellow pages they can get matched sets of belts

mine were same number mazda belts and they werent near the same. it was pathetic, really. i'm not going to point any fingers because i dont know the "history" of the belts, but they were both wrapped in a mazda sleeve for FM racecars. i bought them from my (now old) work who was the official distributor for formula mazdas and parts.

think of it like this; is mazdaracing.com as worthy or more than tweakit? i really dont know, personally. the kit is $10 less (from your price of $260), comes with a belt (not sure if the tweakit does or not) and the shipping is within the continental US. overseas parts arent cheap to ship. not to mention ordering another belt (if i were to order the tweakit kit, i'd probably order 3 belts at once just in case; then again, i dont know the life of their belts).

Are these Gates or rebadged Gates (i.e. Kragen / Schucks / Checkers is rebadged Gates) belts?

The Gates belts have at least THREE different profiles.
They are sometimes labelled A, B, or C.
You can sometimes find this on the belt itself.

Kudos goes to hIGGI for finding this out.
I've seen it myself in CZ.
I've seen some of them in Hawaii labelled like this, but not all of them are.
If you look at the "V" profile, it'll be obvious.
Due to the different "V" profiles, the belts will sit in the pulley grooves differently.
This is how you can get brand new belts of identical part numbers that look like the same diameters to sit differently in a double pulley like this.


-Ted

damn thats some good info. I bet they are just some crapy belt because it has like 3 partnumers it can fit on so I'm sure it's not a true gates belt. plus it just doesn't look quality like gates do as well.

Yea same thing happend to me when I got my alternator from silverrotor. The pulley it came with was a POS, and the grooves are different widths. So one belt would sit deeper in the pulley than the other. I'm trying to order the pulley from Higgi so I can have something decent that doesnt chew the shit out of my belts.