Matt O.

Rennlist absolutely cracks me up. Just to recap...

The Porsche 944 makes its debut, and periodically customers report timing belt failures and bent valves. I personally know somebody who had an 86 Turbo and in 87 he threw the belt the moment he turned the key in the garage. So that had nothing to do with other flawed parts on a year old Turbo, it had everything to do with the belt technology.

So many belt failures in fact, and I say that tongue-in-cheek, that it becomes THE mechanical issue in the 944. The 968 has far less timing belt issues, in no small part because of the automatic tensioner. So that would indicate that the belt was failing due to a variety of things including stretching overtime due to heat and use, and not constantly being tensioned properly.

Jump ahead 25 years. Somebody makes a Kevlar reinforced timing belt, the same material used in bulletproof gear, and Rennlist tells somebody (presumably a newbie) asking about the Kevlar belt that it is not worth it and to just go with OEM rubber belt.

WTF.

In 15 years I've seen a lot of funny things on Rennlist, but this has got to top the list.

V2Rocket

I've never done a belt change on a944 at any mileage that the rollers weren't totally fried. Even just at 3 years and maybe 20k miles the bearings are loose and noisy.

Not changing rollers at every belt change deserves a kick to the head.

A 944 needs the belts done every 3 years, beyond that the belts themselves get crusty. The tight routing path and non compensating fixed tension are what cause the short relative life versus other cars. All 944 models have fixed tensioners. The 968 has a hydraulic compensating tensioner and Porsche doubled the belt change interval to 60k miles, because it stresses the belt way less.

The OEM rubber belts don't break if you put fresh rollers on every time, and tension them right. It seems every single video I've ever seen of someone's running engine, the belt is obviously too tight based on the whining sound. Someone who over tensions the balance belt probably messes up the timing belt too.

odonnell

Fair enough. What I was getting at is - assuming the rest of the rollers and WP are not in the 'danger zone' for ruining a belt...because anyone buying a blue belt is probably/hopefully also keeping up with other maintenance... that leaves the belt as the part that is most likely to fail. And we see that all the time, be it teeth shearing or the belt simply snapping due to different reasons (age, oil deterioration, improper tension, etc).

Just saying that a belt that is more apt to stand up to the above (teeth shearing, oil deterioration, mechanical strength in tension) then it makes sense even as $60 worth of insurance if you are willing to spend it. I don't think the OEM belt is inherently flawed, it's just that like V2 pointed out, there is inherently a lot of stress being put on the belt in the 944 belt drive design. The real-world failures I've seen in person are always teeth being sheared off or the belt snapping. Rollers not seized.

The blue belt wouldn't a cop-out from replacing the belt on time, I see it as insurance against a belt drive that is hard on belts.

Severian

Matt O. said it best and I have to wonder about those that argue with that kind logic.

In order to sleep easier at night they need to have a reason not to spend the extra money.

Never argue with someone who believes their own lies...

bonus12

I think it's safe to say there is only peace of mind if you KNOW it is actually safer. Wasn't that the question of the thread? Maybe I will go with a blue one next time but I don't know of any facts or data that confirm it's actually better for sure. In other words, I guess I would also be assuming it's not somehow worse. That's all I'll say though. I guess it probably is better, but it's still a little bit of guessing.

hacker-pschorr

No kidding.. If the blue belt was $1,000 this thread would make more sense.
Also....talk to any mechanic with a lick of experience and he will tell you how rare it is for a belt to fail on its own. The majority of the time something the belt interacts with fails, and takes the belt out with it (roller, water pump, tensioner etc...)

I bet a week doesn't go by where he sees evidence of a "timing belt change" on a car where they did just that....took the old belt off and put on a new one. Nothing else was changed. This is why when shopping for a TB equipped car you must look through the repair order of the last belt change, don't just go by "belt was changed" and assume everything is OK.

3 years? Sorry, that is nonsense. There is no way I'm changing the TB on my 944S every 3 years (assuming I ever put it back together). My belt was going on year 5 when the cam chain broke.

Voith

There is no empirical proof of it being any real world better than the usual standard gates or conti belt.

There is probably one 944 per 10.000 running kevlar belt and it snapped to one lister:

https://rennlist.com/forums/924-931-...ming-belt.html




So it just may happen to even be much worse than standard belt as was proven to be the case with a certain brand of kevlar belts for Audi.

The other thing is brand name. Good quality standard belts already use high modulus synthetic fibers in their belt constructions it is just not made by DuPont™ and doesn't sound as fancy as Kevlar® but it does the exact same job the exact same way. That is why OE companies use them and that's why they pass testings, work as supposed and hundreds of millions cars use it. That is also why DuPont™ Kevla® belts are not common but only a niche part of a market.

I would spend extra on kevlar belt in a heartbeat if it was guaranteed not to break but since it is not and it does break, that makes it no different than standard only much more expensive.

Matt O.

It's difficult to prove a negative. No belt is indestructible, but I will certainly spend a few extra dollars to put the strongest belt I can in there given the cost/benefit.

For full disclosure (so as to not negatively affect the Gates name undeserved), this is from the thread for the picture above:

Those are key points you should probably include with that picture... a lot of people might not click that thread's link to read everything, and leaving those out is important. Sure, 1 in 10 944 owners maybe running gates blue (I have no idea) but one in infinity who leave a bolt in cam towner.

So... result is expected.

Anyway, I have no stake in Gates and owe nothing to them, I just appreciate them bringing to market for the 944 a reinforced timing belt.

nihil

Since you brought it up, it's no secret that it was 034 who had a bad run of kevlar belts. After the first signs of a problem they did the right thing pulled them off the shelves and recommended replacement to folks that had purchased them. Now they offer the Gates blue instead of their previously (unknown?) sourced kevlar belts.

INA and RAI both now offer and recommend the kevlar belts in lieu of OEM, and I'm pretty sure at least one of them sources them from Gates.

In addition, I believe there was also a lawsuit brought against VAG in regards to premature timing belt failure on the 1.8T.

So yes, manufacturers can and do have bad products at times, and OEM suppliers are just as fallible as anyone else. Add to that the fact that the RL thread you referenced had hints at it being improperly installed and/or other mechanical issues that contributed to the failure, and it's not really pointing to "kevlar belts are bad". Correlation is not causation.

Voith

I beg to differ. Those two points are irrelevant since it is was miss interpretation corrected later in the thread.

Voith

But the key difference is product R&D and resources. Development of DuPont Kevlar timing belt resources and R&D can't blow a candle in comparison to good old standard belt sold in millions every day for the past 100 years.

nihil

No one rubber compound or manufacturing method has been used for belts manufactured over the last 100 years. They are constantly improved out of necessity.

Like everything else in life, it evolves and progresses, and kevlar is just the next/current step in that journey. I imagine carbon nanotube substrate with long chain polymer synthetic "rubber" encasement will be the big thing in belts around year 2025-2030 or so. Until then, I'll use the best technology has to offer in the current market.

951Dreams

Wow, people are passionate about their belts!!!

So who's going to figure out how to run the pump off the balance shaft belt or external electric, and fab up a chain timing design for these cars????

Looking at the layout, it wouldn't be impossible. Oiling would be the only issue, but a self contained plastic chain container with an external electric WP. Exposed balance shaft belts..... Hmmmm.... Who would contribute to a kickstarter campaign! LOL

bonus12

OE belts seem to have a problem with tensile strength, or the taught, lengthwise strength in other words. Whatever leads to this I don't know. Yet, I think both the OE belt and the blue belt are strengthened with the same technology, regardless of casing. The technology that is currently limiting tensile strength seems to be the longitudinal glass cords. Please correct me if I'm wrong. But we have to agree the kevlar or rubber are only casings and the internal components, and external nylon covering, remain the same, no?

Voith

Correct, they are improved constantly so amount of R&D on them is huge and as an evolution lasting from 1945 till today it has to be good. Speaking of which Kevlar was developed in 1965 and was used in racing tires since 1970s. Interesting it never found its permanent way in timing belts if it is such a natural improvement.

So you are implying that only DuPont™ Kevlar® is the aramid fibre that is next/current step, and other same products such as Akzo's Twaron which is the exact same thing or belt company's own version of fibre materials that their research brought up in decades of development is not?

The timing belt is a unit that acts and work exactly as it's supposed to and fiber material used in it is tuned and tuned again to achieve exactly what needs to be achieved and that is why multi million $ cars, boats, machinery and every possible belt driven engine on this planet is using them with close to none belt related failure rate.

Stock valvetrain definitely can and will live decent life with stock new belt. Install heavy springs etc and all bets are off, it can work with either stock or kevlar belt or it can snap regardless.

I'm all for new tech where it makes difference, but in this case I'm afraid the only real benefit is the price and its on standard belt's side.

Chains snap too, eat gears and have all sorts of problems. If you think 944 has huge problem with belts, check out BMW N47 chain problems.