2 GT belt calculator

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Well-Known Member
HMEM Supporting Member
Dec 8, 2020
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Thermopolis Wyoming USA
I have been looking for a simple answer of what length 2 gt belt I need. Is there a good calculator online??

I have a 20 and an 80 tooth pulley 7.062 inches apart. Pulleys are 2mm pitch, 6mm wide. Does anyone know the answer or a resource to find an answer??

Vietti, As I understand it the easy way for two pulley system is half the circumference of each pulley (probably pitch Dia) plus twice the centre distance between. Certainly works for me with T5 belts. BUT, I usually have a means of adjusting the tension.
Yeah I know the belt contact is actually slightly less than1/2 the circumference of the smaller pulley and slightly more on the larger but with tension adjustment it all works.
As you are using GT2which is metric, you are going to have to work in metric.
I make it 458.75mm which is near as to 229 tooth, an unusual size and probably not available.
Go to 230 tooth and fit an idler on the non-drive side.
Thanks for the reply's! I decided to take an old school approach and cut an unused long belt and measure the needed length. I came up with 464 which is right in there with the others numbers. Turns out precision maybe unnecessary because all sizes are not available esp in the longer belts. Finally found some from AliExpress, closest they had was 460 and 466. Will have to make em work, its driving a magneto on a hit and miss engine so I can fudge the mag mount to suit. They were cheap too but expected deliver is Feb 12!
I'd be checking the measurements as it doesn't sound correct.
Either that or you gave us incorrect data.
Here is a decent calculator for timing belts
Timing Pulley Distance Between Centres Calculator

Running the numbers through it (20T, 80T, 7.062" CtoC)

231T belt (462mm) = 7.086 CtoC
230T belt (460mm) = 7.046 CtoC

That is a fairly long belt in relation to the pulley diameters. I bet the 230T belt would pop right on. Might load the bearings a little, but shouldn't be a big deal. Better than a sloppy belt. Is an idler pulley an option?

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