Stretch Belts vs Traditional Serp Belt w/ Tensioner

[TXCarGeek]

Anyone have insight in to the pros and cons of stretch belts? I have an '08 E60 550i with the N62 engine and early iterations of this engine used a traditional serpentine belt with an automatic tensioner for the a/c compressor. Later, BMW switched to a stretch belt. Some folks over on the E60 forums eventually convert to the tensioner since the threaded boss for the tensioner and bolt remains on the timing cover even on vehicles that originally came with the stretch belt?

Aside from the ease of replacement that comes with an automatic tensioner, are there other reasons to replace the stretch belt with a tensioner if it's a simple plug and play type swap?

 

[slacktide_bitog]

With the stretch belt, if you take it off for any reason, you must replace it.

A regular non-stretch belt can be reinstalled

 

[TXCarGeek]

Ahh yeah, forgot about that!

Any idea why OEMs started using stretch belts to begin with? I'd imagine there's slightly less resistance with one less pulley and possibly lower NVH from the accessory drive, but are there other reasons?

 

[ctechbob]

Sure, cost. That tensioner isn't free and I'd be willing to bet that the stretch belt doesn't cost any/much more than a serpentine.

 

[KrisZ]

I have it on my Mazda 3 driving the AC compressor. No issues at all with performance or difficulty of replacement.

It may case, this appilication actually makes for a less convoluted overall system, as I only have one tensioner and no other idle pulleys to deal with. Also the compressor and the alternator seem to be located in more accessible spots when compared to Ford focus with the identical engine, but Ford used one long belt to drive everything, so the accessories are positioned differently.

 

[zzyzzx]

There are no advantage to having a stretch belt, except to the bean counters at the auto company. Nice to know that you can sometimes convert it to a regular serpentine belt with tensioner.

 

[TXCarGeek]

Originally Posted by zzyzzx
There are no advantage to having a stretch belt, except to the bean counters at the auto company. Nice to know that you can sometimes convert it to a regular serpentine belt with tensioner.


Compressors on N62 equipped E60s are known to develop pulley bearing noise over time. Mine is doing it right now and I've been curious if the belt could possibly be exerting too much pressure on the pulley and bearings which eventually wears things out. Doubt it would fix the crickets chirping noise that I get from the compressor on cold starts, but I'm going to the change to a tensioner and serp belt soon just for [censored] and giggles.

 

[Tomioka]

GM trucks went to a stretch fit belt for the A/C compressor on the last years of the LS engine. The tensioner pulley hanging low and exposed to the elements caused premature failure. Went to a stretch fit belt on my 02 just to have one less point of failure and it was cheaper (stretch belt and lisle belt installer/remover tool).

 

[NYEngineer]

The stretch belt on my 09 Suburban has been completely issue free. I bought the tool to install a new one and when I swapped it out at 100,000 miles, I was amazed what good condition the original belt was in.

 

[KrisZ]

BITOG can be a funny place sometimes regarding automotive advice.

People have no problem recommending a tensioner and all idler pulley replacement while changing the accessory belt. Which I agree with in some applicatiins.

But you present them with an extra stretch belt, which is quite cheap and easy to replace in most cases, most see it is bad because it cannot be reused. And it's bean counters fault.

Another positive to me is that problems with AC compressors or clutches are very common. Having the compressor driven by a separate stretch belt, one can simply cut it off and keep on driving until the problem is sorted out.

 

[bdcardinal]

Not a fan of stretch belts personally. I have the kit from Ford to eliminate the one on my Mustang.

 

[TXCarGeek]

Originally Posted by KrisZ
BITOG can be a funny place sometimes regarding automotive advice.

People have no problem recommending a tensioner and all idler pulley replacement while changing the accessory belt. Which I agree with in some applicatiins.

But you present them with an extra stretch belt, which is quite cheap and easy to replace in most cases, most see it is bad because it cannot be reused. And it's bean counters fault.

Another positive to me is that problems with AC compressors or clutches are very common. Having the compressor driven by a separate stretch belt, one can simply cut it off and keep on driving until the problem is sorted out.


The compressor is driven by a separate belt on my engine regardless if it's a stretch belt or regular serp belt w/tensioner so that positive is moot in my case.

Also, taking up the slack on the tensioner and slapping the belt in is much easier than having to use a special tool and cranking the engine over by hand to ride the stretch belt on.