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Weight of HTD Timing Belt


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Hi Everyone

There's been a discussion on the Giugiaro Technical room, to see if it is possible to adjust the Trapezoidal Timing Belt with a Clavis gauge. It the only expected real difference between the setup for the Trapezoidal Timing Belt and the HTD Timing Belt seems to be the weight of the HTD Timing Belt. It is expected that the HTD Timing Belt is heavier than the Trapezoidal Timing Belt, and thus that a higher calibration frequency is required for the Trapezoidal Timing Belt.

If I have the weight of the HTD belt, and I can measure my own Trapezoidal Timing Belt, its an easy calculation to get the Clavis frequency for the Trapezoidal Timing Belt. So, can someone PLEASE measure and tell me the weight of an HTD belt?

Kind regards


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The Clavis gauge measures resonant frequency due to tension in the belt. The mass of the belt has very little to do with the tension and therefore very little to do with the resonant frequency of the system. It has some effect, but not as much as the shape of the teeth and stiffness of the belt, the length of the span...

THe Espirt V8 has different belts than the Esprit 4cyl, yet they use the same 110Hz specification for the Clavis measurement. Though the span of belt where the measurement may not be the same.

The tensile strength of the old trapezoidal belts may not be the same either, so you may not want it as highly tensioned.

Here is what Tim Engel had to say about the Lotus Excel belt tension with the Trapezoidal belt.

The belt tension increases as the engine temperature rises... it does get

tight when hot. Always check the tension with the engine cold before the

engine has been started for the first time that day.

Does the belt whine when the engine is up to full operating temperature.

If it does not whine, then it's not too tight in the sense that you need to

be worried about it. It may still be tighter than spec, but nothing is

about to break... at least not as a direct result of tension.

If the belt whines, then it's too tight.

If the belt whines when cold (it's loosest condition), then it's way too

tight and will only get excessively worse as the engine comes up to temp...

adjust the tension. If the belt doesn't whine when cold, but starts to

pick up a little whine as the engine reaches full operating temp, then it's

borderline over the limit. Don't panic, but make plans to adjust the


Up & down belt deflection isn't the way to check the tension. Little

changes in the tensioner adjustment make significant changes in belt

tension. The resolution is finer that you will be able to judge by

wiggling the belt up & down.

I strongly recommend you purchase either a Burroughs gauge or a Krikit.

The Burroughs is the specified gauge, but it's expensive enough that most

owners don't buy one. The economical grassroots alternative is the Krikit

KR1... in the US, they're $10 at NAPAonline, or $15 at NAPA stores. The

Krikit is sold internationally, but I have no clue where... or IF... in

New Zealand. You could try

There is a "Twist Test" to check the tension by hand. If you have worked

with the engines enought to be familiar with them... with how the belt

should feel, then it's possible to judge it's tension fairly well with the

twist test. But I don't recommend it for someone who isn't that familiar.

I'm very familiar with the engine, but I won't use the twist test if

there's a gauge available. I consider the twist test a valuable skill for

unplanned roadside repairs, but not for use in normal planned maintenance.

NOTE that all tension tests, Burroughs, Krikit or twist, must be

performed on a cold engine before it has been started for the first time

that day, and at 15


Vulcan Grey 89SE

My Lotus Photo and Projects Album

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as requested my belt is a Gates one for a Lotus Esprit Turbo SE. The following information is on the belt reading from left to right: The gates Logo, PowerGrip HTD, made in UK, B9126697F and at last some white numbers xxx 6 248DS, The numbers on the place of the xxx are 222 to 230 in increments of 1.

Hope this helps


BTW: I weighted the belt again and the outcome was 150gr.

Esprit Freak

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Thanks Freek, now we just have to wait to see what Giorgio has to see if there are any belt spec differences. I am not as familiar with the Gates numbering as I am with others but I think the other numbers you mentioned are used to denote the position of the belt in the mould, purely for tracking purposes. The moulds tend to be specially machined drums about 1 metre long. The belt material is placed around the outside and the drum then "cooked" under controlled conditions. At the end a 1 metre wide belt appears. It goes through several more processes and is then cut into the required belt widths similar to putting a loaf of bread into a bread slicer. These numbers show the position of your belt in that mould.



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