MBMB

I'm sure this has been discussed before, but I can't find it. Which is better, the Porsche or the aftermarket (as sold by, for example, 928intl) timing belt?

I'm inclined to put the Porsche belt in unless the aftermarket one is superior in some way other than price.

Garth S

Porsche doesn't manufacture belts to my knowledge - they may add a 'designer' label, and only do so to suppliers of the highest quality ( eg., Conti, Pirelli, Optibelt, etc.). As this belt configuration is unique to the 928, purchase from any of the top brands will give an oem quality product - normally at improved pricing.
My last HTD (..xxx.50) belt ,for an '88, was a newer design tooth profile by Optibelt: IMHO, this is an excellent belt, has not req'd readjustment on the PM intervals (ie., no stretch) - and is also going in the '80 this winter!
The 'Big Three' can discuss/supply a belt to meet your criteria - plus all the rollers, etc to go along with this 'rite of passage' exercise.

MBMB

Thanks, Garth. Where'd you get the Optibelt? Big 3?

T_MaX

"PORSCHE there is no substitute".

JMHO, Go with the Porsche factory belt, I bought mine from DEVEK (one of the BIG 3).

DEVEK

Garth S

Hey MBMB,
As there was no lead time on this last trick (sudden water pump death), I purchased locally thru an industrial supply house (I'm several days away from 928 civilization)- for ~$75Cdn. I know Zims (Tx) carry them - can't comment accurately on 'soup de jour' of the 'big three': however, these folks always come thru.
For ref., the pn is 928 105 157 50, or in this case, Optibelt ZR-HR 58219x1".
Satisfied as I am with this belt, I wouldn't hesitate to use a Conti, Pirelli etc.; however, have seen some 'no-name' belts wearing a "made in Germany" label: as fine as they may be, possibly from the same factories, I'd prefer my engine insurance policy to have a premium label.

Steve J.

Here's what the teeth look like on the aftermarket belt from Zims. Supposedly the grooves make the belt run quieter. Try to determine the date of manufacture and get a fresh belt. I bought a "new in the box" genuine Porsche timing belt on eBay, but the date of manufacture was 1992. I didn't feel comfortable with a "new" belt that was 12 years old.

Tommy928

I just had my timing belt replaced by the dealer and 10 days, 100 miles later the tension came on. Back to the dealer. The belt has stretched and the tension had dropped from 5.3 to 4.7 triggering the tension light. The dealer told me that this is common for the belt to stretched in such short period and they have seen it many times. I found this very strange that an OE qualified part would stretched enough to trigger the tension light in 5% of the typical allowable period before retensioning.

I am sure that this is a source inspected item and Porsche just accept the test report from their vendor as meeting the spec requirements. I think Porsche may need to have a tighter control of their supplier.

Judging by this experience I would think the Porsche belts and aftermarket belts would be similar.

By the way I have an aftermarket belt on my 944 for over three years without any issue other than retensioning at 1800 miles.

Normy

Tommy I just replaced the belt on my '85. I've driven about 1200 miles, and no belt light. I'm planning on taking it back in for a tightening at the 2000 mile point, as per the writeup that came with the belt. I bought it from 928 Specialists...

It said "Porsche". Did you change out the pulleys and tensioner? 100 miles sounds too short. Somethings amiss-

N!
'85 S2 5 Speed

Tommy928

Normy, everything were replaced with new OE parts and the front end resealed by the Porsche dealer. They told me that this is a common occurance. Even the service department head (who I have known for 10 years told me the same thing when I called for answer).

Since the belt is made in batches there must be a large batch-to-batch variation in the rubber valcunization, hence some belts stretch sooner than others.

If the tension light comes on again in a short period then I will definitely think the belt is defective.

heinrich

I've never heard of belt failure - Porsche or otherwise. Unless the pump failed, tension was wrong or some other extraneous force acted on it - even on belts well over their service life. Has anyone else?

Lizard928

Heinrich, have heard of the belt snapping on 944 but not on the 928

PorKen

The belt I installed which came from WorldPac (supplier to many resellers), was made in Great Britain!

MikeN

Very few instances of the belt actually breaking clean, but have seen many instances of belt teeth sheering off........so to me that would be "belt failure". Even more instances of the belt not being tight enough causing it to jump.

glenn faken

i saw a while back someone mentioned a gates belt so i sourced one to compare to the original belt on the donor motor i have. as i looked at the belts a could see that the cog part appeared to be just rubber with no internal webbing. i ripped a part of the cog off and confirmed there is no internal support. the support for the cogs comes from the bonded material on the inner part of the belt.

if your gears are worn. it will attack this surface and if that inner bonding goes away so do your teeth on the belt. anybody running without covers on or with oil leaks will accelerate this wear.

UKKid35

This is what you don't want to see, a belt with missing teeth:

http://www.928.org.uk/~ukkid35/proje...ture%20002.jpg

This is what may have caused it, sprockets with worn teeth:

http://www.928.org.uk/~ukkid35/proje...ture%20030.jpg

This is what teeth that are about to fail look like:

http://www.928.org.uk/~ukkid35/proje...ture%20034.jpg