TR2/3/3A Fan belt

Have always used NAPA 25-24379 (Gates TR24379) fan belts on my TR3 with the stock fan and generator pulleys. Purchased a new NAPA 25-24379 several weeks ago and ran out of belt tension adjustment before the new belt was tensioned. The cardboard sleeve for the new belt gives the outside circumference as 978mm (38-1/2”) and the top width as 17mm (21/32”). I still had the cardboard sleeve from the old belt (don’t ask why…) and the sizes are listed as circumference 976mm (38-3/8”) and the top width as 19mm (3/4”). So the new belt is 2 mm larger in circumference and 2 mm smaller on the top width. The combination of the two dimensional changes on the new belt made it impossible for me to tension. I did purchase a NAPA 25-28386 (20mm x 996mm) belt but have not tried that option yet.

I did have a belt from The Roadster Factory, purchased several years ago, which was part # 58924 and is an Optibelt-VB and sized as 20 x 900. Only Superman could install that belt. If you are carrying the Optibelt belt as a spare in your boot (trunk) and don’t carry a 6 foot long crowbar to pry it over the pulleys you will be crying when you try to install it on that cold, moonless night when your belt breaks.

Do you think they would work if you unbolted the generator to install them...or are they even too tight for that?

I recently went through that exercise because I changed to an alternator. What I found is the width of the belt has more of an effect on the fit than the length. Because it is a V-belt, the 'working length' has a bigger variance with width changes. And remember, the generator belt does not need to be very tight. Too tight a belt will quickly ruin a generator and/or water pump. -Still when I had a generator, I had to loosen the generator to get the (correct) belt around the pulley. -Although you can start a cog on the pulley, and use the hand crank to turn the engine over to pop it into position (sort of like putting a chain back on a bicycle).

I believe one could get the Optibelt on if the generator was unbolted but I have such a hard time accessing one of the generator mounting bolts that I would dread having to remove the generator to replace the belt. The Optibelt is not a cogged belt so it was tougher for me to work the belt into place. Both NAPA belts are cogged and seem more flexible.

The wider NAPA belt (25-28386) does ride quite a bit higher in the pulley at what I would consider the "normal" spot a belt should ride in the pulley. That being said, I never had any problem with the narrower NAPA belt (25-24379) even though it was riding pretty far down in the pulley. It was also easy to install as the generator could be pushed toward the engine enough to install the belt and still have enough travel to tension the belt.

I would agree with the belt tension observation. I run my belt pretty loose and have had good luck with both generator and water pump bearings.

I purchased Moss's "better" cogged replacement belt,(834-025) and their alternator conversion. However it was impossible to mount the alternator because the belt was too short. I am waiting to see what Moss's technician suggests. It sounds as though a generic belt might be the solution, but which one?

1960 TR3A, 60014

Dr_Mike said:

I purchased Moss's "better" cogged replacement belt,(834-025) and their alternator conversion. However it was impossible to mount the alternator because the belt was too short. I am waiting to see what Moss's technician suggests. It sounds as though a generic belt might be the solution, but which one?

1960 TR3A, 60014

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All of the belt manufacturers and distributors publish very detailed specifications. To get a perfect fit you still might need to loosen or remove the gen/alt.

Tom

Watch out for the pitch of the belt as well. It should fit to the bottom of the pulley.