Which HTD timing belt again?

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NickC
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Which HTD timing belt again?

Post by NickC »

Sorry for going over this again but I am not completely clear which timing belt to use on a 912HC.

From what I can remember/establish this is the round toothed HTD profile belt. Seems to be four alternative versions available:
  • B912E6697F - HSN rubber, 8 yrs replacement
  • JAE Blue - Gates Racing HNBR rubber, 10 yrs replacement
  • Gates T249 - HSN rubber, 25.4mm (1mm narrower)
  • Peugeot 405 Mi16 alternative
Is the Peugeot 405 alternative blue HNBR rubber or black HSN? If HNBR rubber is this preferred over the standard Gated HSN belt, what replacement period is recommended for this belt?

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Re: Which HTD timing belt again?

Post by AndyC »

The lst you gave is really just 3 choices not 4.

The 405 Mi16 one is just a standard belt from any manufacturer and is 25.4mm, although (hopefully) people would choose to use a known trusted manufacturer's one in which case it may well be the Gates one.
HNBR (Hydrogenated nitrile butadiene rubber) is another name for HSN (highly saturated nitrile), so don't get hung up on which name a firm gives (it's like some manufacturers refer to high pressure diesel engines, whilst other use equivalent technology but name it common rail).

The Gates blue one uses a very specific contact material that doesn't have as much friction an so doesn't wear as much as the older style belts.

B912E6697F - HSN rubber, 8 yrs replacement
JAE Blue - Gates Racing HNBR rubber, 10 yrs replacement
Gates T249 or other Peugeot 405 Mi16 equivalents - HSN rubber, 25.4mm (1mm narrower)

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Re: Which HTD timing belt again?

Post by NickC »

AndyC wrote:The lst you gave is really just 3 choices not 4.

The 405 Mi16 one is just a standard belt from any manufacturer and is 25.4mm, although (hopefully) people would choose to use a known trusted manufacturer's one in which case it may well be the Gates one.
HNBR (Hydrogenated nitrile butadiene rubber) is another name for HSN (highly saturated nitrile), so don't get hung up on which name a firm gives (it's like some manufacturers refer to high pressure diesel engines, whilst other use equivalent technology but name it common rail).

The Gates blue one uses a very specific contact material that doesn't have as much friction an so doesn't wear as much as the older style belts.

B912E6697F - HSN rubber, 8 yrs replacement
JAE Blue - Gates Racing HNBR rubber, 10 yrs replacement
Gates T249 or other Peugeot 405 Mi16 equivalents - HSN rubber, 25.4mm (1mm narrower)
Thanks for explaining that Andy.

It is a shame that the Gates Racing blue belt is not available for other vehicle fitments, even if it was 1mm narrower that would probably still be fine and would probably be a lot cheaper than the JAE sourced Blue ones which do seem to be exceptioonally expensive.

I know it is not a Gates one but this HSN rubber one might be ok: https://www.ebay.co.uk/itm/Lotus-Esprit ... 2540579781

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Re: Which HTD timing belt again?

Post by Alan_M »

I assume you've read through this post - viewtopic.php?f=25&t=10292 as it gives some very good information, especially from Tim Engel.

I wasn't aware there was a long life belt, other than the blue Gates belt. I thought all others were 2 year /24,000 miles replacement.

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Re: Which HTD timing belt again?

Post by NickC »

Alan_M wrote:I assume you've read through this post - viewtopic.php?f=25&t=10292 as it gives some very good information, especially from Tim Engel.

I wasn't aware there was a long life belt, other than the blue Gates belt. I thought all others were 2 year /24,000 miles replacement.
Alan,

From that earlier post you linked:
In 1995, the round-tooth HTD belt was upgraded to a B-prefix part number, and used HSN rubber. It's change interval was 75,000 miles or 8 years
So according to that the B912E6697F belt should last for 8 years which is only a couple of years less than the 10 years suggested for the Blue HTD belt.

I wonder if any other belt manufacturers (Flennor etc.) make a Blue HNBR belt in the same dimensions.

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Re: Which HTD timing belt again?

Post by AndyC »

In terms of interval, and since this is an Excel (also applies to Eclat & Elite) rather than an Esprit, I'd suggest that a long-service belt is unnecessary. Simply use a decent 25.4mm belt, but change it every couple of years. Whilst the belt may be good for 8 or 10 years, that assumes a reasonable pattern of usage and lots of our cars sit for several months of disuse so the belts get set in shape around the pulleys etc, along with having a tensioner that benefits from at least a check (spin it near the ear) every couple of years. And assumes that no debris has managed to damage the belt.
If it's home mechanics/ servicing, then the cost of a standard Gates belt every 2 years isn't much, OK different if you're having to pay a specialist to do it then perhaps a long-service belt helps negate the frequent labour costs.

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Re: Which HTD timing belt again?

Post by Esprit2 »

NickC,
The Lotus A-prefix HTD belt is HCR rubber, which is late 1960s technology. The B-prefix belt is HSN rubber (Highly Saturated Nitrile), is 1995 technology, and was the last "Lotus" belt for the 9XX 4-cylinder engines.

HNBR is the current technology, and it's different from HSN... they're not the same.

I'm not aware of any mainstream manufacturer making an HNBR version of the round tooth HTD belt in a size to fit the 9XX; with the exception of Gates Racing, which is a low volume specialty division of Gates Rubber. JAE commissioned them to make the blue HNBR HTD belt for Lotus engines (4-cyl & V8), so Gates makes it exclusively for them. It doesn't appear in Gates' catalog, and isn't available from Gates retailers. JAE does sell to other Lotus specialists, including Lotus Cars, plc, so it's available from more suppliers than just JAE. It's expensive, but it's good.

Gates Racing does make a blue HNBR version of the trapezoidal tooth belt... Gates P/n T104RB. Any Gates retailer can order it for you, but it's unlikely they will have one in stock.

Besides improved reliability and durability, the Gates blue belts offer greater stability. Continue to check the belt's tension on a regular basis; however, once it's properly tensioned during installation, it's very rare that blue HNBR belt will ever need to be re-tensioned.

Blue is a Gates Racing trademark, and it's just an added cosmetic laminate. The black part is the 'working' HNBR portion, and the blue part is just marketing bling.

Not all Round Tooth timing belts are HTD, and the Gates T249 is Curvilinear I, not an HTD belt. The round tooth evolved through a series of revisions. HTD was the first, followed by Curvilinear I & II, GT, etc. Those follow-on belts will not properly fit the Lotus HTD pulleys.

The 1991 Peugeot 405 Mi, 1.9L DOHC engine uses an HTD belt with the same number of teeth as the 9XX, but slightly narrower (25.4 Vs 26.4). It will fit and work just fine, but like the Lotus belts, I'm not aware of any company making a modern HNBR version of the 405 belt. Gates does make belts to fit the 405, but they're not HNBR. Gates' belt for the 405 has it's own part number, but the difference is only timing marks that are printed on the Peugeot belt. Ignore the 'Peugeot' markings, and it's the same as the generic Gates belt of the same material.

Belts for the Nissan VG30E SOHC V6 engines also went through a series of round-tooth evolutions. Of the 3 or 4 different round tooth belts used, only the HTD belt used after August 1994 (ie, Sept-onward) fits the Lotus engine. It's available in HCR & HSN rubber, but not the current HNBR.

Regards,
Tim Engel

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Re: Which HTD timing belt again?

Post by NickC »

How about a group buy?

Apart from Gates, who seemingly will only make for JAE are there any other belt manufacturers we could approach to make a batch of HTD HNBR belts. I wonder if Gates would make a batch if asked?

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Re: Which HTD timing belt again?

Post by AndyC »

Esprit2 wrote:NickC,
........
HNBR is the current technology, and it's different from HSN... they're not the same.

.......Regards,
Tim Engel
Tim.

I have to disagree, there are countless manufacturers that will confirm they are the same.
It is possible that a manufacturer may define their own belts differently and have one variant badged as HNBR and another as HSN
, but Hydrogenated Nitrile Butadiene Rubber (HNBR) is not specifically different to Highly Saturated Nitrile (HSN), in its definition.

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Re: Which HTD timing belt again?

Post by NickC »

AndyC wrote:
Esprit2 wrote:NickC,
........
HNBR is the current technology, and it's different from HSN... they're not the same.

.......Regards,
Tim Engel
Tim.

I have to disagree, there are countless manufacturers that will confirm they are the same.
It is possible that a manufacturer may define their own belts differently and have one variant badged as HNBR and another as HSN
, but Hydrogenated Nitrile Butadiene Rubber (HNBR) is not specifically different to Highly Saturated Nitrile (HSN), in its definition.
Have just asked Gates if they will make a batch of what they describe as their Blue HNBR belts for us, when they answer I can then ask them about the difference between HNBR and HSN.

Anyone suggest which other belt manufacturers we could try?

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Re: Which HTD timing belt again?

Post by Qwertyco »

I'm reading this with interest as I've just bought a Gates T259 belt, but not fitted it yet.

This is an interesting read, and seems to infer that HTD and Curvilinea are the same thing, but Modified Curvilinea
is quite different. It's quite vague about the modified versions though:
https://ww2.gates.com/IF/facts/documents/Gf000282.pdf

EDIT: I think this answers my own question:
https://www.lotustalk.com/forums/f164/l ... ost2233666

It just so happens that I also have a brand new genuine Lotus belt as well, and a brand new cam pully, so I'll
try to replicate this test.
"Life is like a Dancing Monkey, - Pretty amusing, until it starts to lob faeces at you"

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