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I see the Gates T249 belt gets referenced quite a lot. Something to bear in mind is that this is not just a Gates T188 belt made using HSN rubber, the tooth profile is different too.
T104 = Trapezoidal tooth belt in HCR rubber, 24,000 miles/ 24 months

T188 = HTD round-tooth belt in HCR rubber, 36,500 miles/ 36 months
T249 = HTD round-tooth belt in HSN rubber, 50,000 miles

T188 & T249 are fit interchangeable, but the T249 is the more durable belt.

T188 doesn't work in the UK, but asking for Gates part number 5168NS does.

Regards,
Tim Engel
Lotus Owners Oftha North (LOON)
 

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(Snip)... So, in my case with a blue belt, water pump & new tensioner in 2009 and about 23K miles on them.... am I still good for at least this driving season and maybe do it next spring? Just curious - I know your answer doesnt come with a warranty :)
At the rate you're racking up the miles, you should be good for several years to come.

The original recommendation for replacing the tensioner bearing was every other timing belt... or as needed. The bearing hasn't been re-invented to something much better, but belt life has increased. So while every other belt used to work out to 48,000 miles, with an HSN belt the total is now 100,000 miles. All things considered I think you should give serious consideration to replacing the bearing at 50,000 miles. Even if it's good at 50k, it's not expensive compared to the labor of replacing it mid-term if it dies before the next belt is due.

Given the labor involved (either dollars or effort), I replace both the belt and the bearing whenever I'm into the engine that deep.

Water pumps are also pretty reliable up to around 50,000 miles, then require regular inspection.

Regards,
Tim Engel
Lotus Owners Oftha North (LOON)
 

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Discussion Starter · #43 ·
At the rate you're racking up the miles, you should be good for several years to come.

The original recommendation for replacing the tensioner bearing was every other timing belt... or as needed. The bearing hasn't been re-invented to something much better, but belt life has increased. So while every other belt used to work out to 48,000 miles, with an HSN belt the total is now 100,000 miles. All things considered I think you should give serious consideration to replacing the bearing at 50,000 miles. Even if it's good at 50k, it's not expensive compared to the labor of replacing it mid-term if it dies before the next belt is due.

Given the labor involved (either dollars or effort), I replace both the belt and the bearing whenever I'm into the engine that deep.

Water pumps are also pretty reliable up to around 50,000 miles, then require regular inspection.

Regards,
Tim Engel
Lotus Owners Oftha North (LOON)
Thanks, Tim. Well, Im sure Ill get this all done before I hit 50K miles on the current major. Im leaning towards this fall but might push it out a little longer. Now, of course, if something else that requires "getting in there" comes up then its a no brainer and it all gets done. But, until then I feel good about putting some more miles on the current parts.

Mega dittos on doing the belt and tensioner as one. No question on that.

:)
 

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Here are some illustrations to show the differences between the tooth profiles of the OE and T249 belt. The first picture shows the differences between Curvilinear and Modified Curviliner (III) tooth profiles. The Lotus B912E6697F belt has the same profile as 5305XS belt whilst the T249 has the same profile as the 5484XS belt.

The second picture shows the B912E6697F belt being wrapped around a cam pulley. It snugly fits with minimal tension on the belt.

The third picture shows the Gates T249 belt being wrapped around a cam pulley. It does not fit readily with greater tension on the belt and is riding out. It can be made to fit but with much more tension required.

The flanks of the T249 belts teeth are going to suffer damage when used with a HTD pulley. IMHO, for what the belts cost, it is not worth risking a belt failure by using one with the wrong tooth profile.
 

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Discussion Starter · #45 ·
Here are some illustrations to show the differences between the tooth profiles of the OE and T249 belt. The first picture shows the differences between Curvilinear and Modified Curviliner (III) tooth profiles. The Lotus B912E6697F belt has the same profile as 5305XS belt whilst the T249 has the same profile as the 5484XS belt.

The second picture shows the B912E6697F belt being wrapped around a cam pulley. It snugly fits with minimal tension on the belt.

The third picture shows the Gates T249 belt being wrapped around a cam pulley. It does not fit readily with greater tension on the belt and is riding out. It can be made to fit but with much more tension required.

The flanks of the T249 belts teeth are going to suffer damage when used with a HTD pulley. IMHO, for what the belts cost, it is not worth risking a belt failure by using one with the wrong tooth profile.
Excellent data. Does the gates blue belt fall into this discussion/comparison? Curious.
 

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Excellent data. Does the gates blue belt fall into this discussion/comparison? Curious.
I did try the wrap test with my new Gates blue belt since I had the pulleys off anyway, it fit perfectly like the top picture.
 

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I find it very hard to believe or convinced that the pristine extra T belt I received with my Esprit, serial number 25413303 78 03205 04845493 purchased in 2007 is now good for nothing!
 

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You would seriously consider putting a 17 yr old timing belt on your car for the sake of saving $50?

Some folks have to live and learn I suppose...
 

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I just cant agree with any decomposition in a pristine belt! Entropy perhaps? Thats another topic.
It was not exposed to U.V Radiation, only perhaps to temperature changes.
After all it still smells new and is flexible.
 

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It's your money!

I think Artie said he spent $19k on a rebuild or 2... Most people would spend ~$3K+.

I spent less than that, and got a Quaife LSD, new header tanks, fog lights, full rebuild. But I got amazing deals from Lotus (including the last set of pistons I think). And I still replace my timing belt nearly every year!
 

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Hey, go for it! But if things don't work out we will have a rebuilt engine up for sale in the near future..... Pricing will be about 50 blue belts.

:D
 

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The phrase, from Dr. John Bridge in 1587, comes to mind. He wrote Defence of the Government of the Church of England. In it, he wrote, "If they pay a penie or two pence more for the reddinesse of them..let them looke to that, a foole and his money is soone parted." Not unlike saying you would drive at a sustained 130 mph on 17 year old tires because they look and smell ok. Once you have replaced the timing belt yourself, skinned your knuckles, sworn at the engineer that designed what are laughingly called 'access' openings in the chassis, and struggled with the tension and hoses will you understand why so many above are saying buy a new belt. It just isn't worth the hassle or potential catastrophic failure to rely on the look and smell.
 

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I like my favorite old movie quote (which seems to come up alot since I bought an Esprit ;-))
"...you have to ask yourself: Do I feel lucky?..."
 

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25413303 is a Goodyear belt reference and is 25.4 mm wide so it is on a reduced life compared to the OE belt to start with. IMHO for the price of a belt it is not worth risking using an old belt.

FWIW I am currently replacing my OE B912E6697F cam belt after only 37 months and 15k miles and can see cracking the full length of the base of one of the teeth. The car has been driven in all conditions all year round.
 

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I find it very hard to believe or convinced that the pristine extra T belt I received with my Esprit, serial number 25413303 78 03205 04845493 purchased in 2007 is now good for nothing!
It's still usable...
 

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I've dealt with a lot of timing belt issues....and a lot of discussion of the topic...on more expensive and complex exotics than our simple four banger Esprits.

The fact of the matter is that it's rarely the belt that fails. In the vast majority of cases it is some other factor which is the culprit....which then causes the belt to break...such as a failing tensioner bearing, oil leaking onto the belt and degrading the belt, dirt and road debris entering into the vicinity, etc.

To think that simply putting a good quality belt on your Esprit is going to make it relatively impervious to failure is really not understanding the big picture. I would strongly encourage DIYers to look at these other factors in parallel when considering what to do to avoid a catastrophic failure.
 
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