Timing belt: why such a short change interval?

[Clive59]

I saw this doc from Gates, and was wondering if we are being a bit paranoid about timing belts.

The same equivalent belt(ok, slightly narrower than Lotus original, but essentially the same) is a Gates T104, which is also used in many Nissan's (300ZX, Maxima, Pathfinder...(many V6 cars), and Mercury in USA, and all the specs say 72months/60Kmiles. This is for the trapezoidal belt. The T249 is for the round sprockets, and is the same interval.

Is the Lotus really that much different in wear? Can't see why it should be. Comments?

Here is the doc URL: https://assets.gates.com/content/dam/gates/home/resources/resource-library/catalogs/timingbeltreplacementguide.pdf

 

[Barrykearley]

Tensioner bearings will fail before the blue belts need replacement.....

lots of horror stories when belts break - and it’s expensive as well. Hence why folks change them 👍

[andydclements]

Degradation of the belt is partially from heat cycles so perhaps ours gets hotter than those other applications so each cycle (colt to hot and back) has more effect, perhaps our cars are assumed to do less miles per cycle, perhaps the route of our belt is more extreme in it's flexing, etc. I really suspect it's because the engines are not tested to destruction as much as the others, where perhaps 50 engines (speculation) are routinely destroyed in order to prove the longevity of those other brands where they need to as there will be 10-100s of thousands of the engine out there in use, and a few failures could destroy the reputation.

[Clive59]

1 hour ago, Barrykearley said:

Tensioner bearings will fail before the blue belts need replacement.....

lots of horror stories when belts break - and it’s expensive as well. Hence why folks change them

Not talking of the blue belts Barry, just the bog standard black ones, yes, no doubt expensive if they break, but are there any evidence based reasons why they break any earlier than the other manufacturers ones, if in fact they do? As Andy said, potentially lots of reasons, or none at all.

[Barrykearley]

Black ones cost pennies - considering the balance of cost - just replace as a routine maintenance program. 

Should be remembered like mentioned above - it does get very damn hot in that engine bay. Definitely more so that a “normal” car

[Guest]

The other killer is long intervals of none use. Having all the tension on the belt in a condensed area can be equally as damaging to the rubber as heat cycles. If your car sits a lot and your using normal grade belts I would not go beyond 3 years. If you want more life then fit the TR104 (blue belt) it’s only $60 USD and IMO worth the extra pennies. My Esprit S1 sits for extended periods due to work commitments. I fitted the blue belt feeling it was the safer option.

i reaquired my S1 in August 18 and the belt at that time was 7 years old. The chap I purchased it back from only did 600 miles in 4 years. He was a  total hands off owner and had no interest in getting dirty. First thing I did when I got it home was do a belt service. The rubber on the 7 year old belt appeared in good condition with no visible signs of wear. Just looking at it you would say it’s good and doesn’t need changing. The belt was a higher grade one than standard and was supplied by JAE. But prevention is better than cure and no way was I going to risk it. 

[910Esprit]

I wonder if the manufacturers original calculations could also take into account the diameter of pulley wheels, cam profiles, CR etc?   NB The semi automatic tensioner is not maintenance free, so I would want to inspect that every few years, regardless of belt life/colour.