Belt for upper pulley
 

Quick question, I had a 2.3 upper pulley on the car and just installed the 2.175 pulley. I see a lot of people running the green belts. I am still using the stock belt. Do I need to switch?

Looks like the gates belt K080855HD is 86 inches in length that people are running with smaller upper pulleys but the stock supercharger belt is 85.2 inches so the belt some people are running with the smaller upper pulley is actually bigger. So I guess either belt is fine?

You are correct about the K080855HD being larger.

It is 8mm larger and SHOULDNT be used with any smaller pulley.
It will slip at high RPM even with a grip-tech coated pulley.

Use either the stock 85.24 inch belt or one of the following which are 4mm's shorter than the OEM K080852 belt or 12mm's shorter than the K080855HD you mentioned.

These from gates are good. K080850, or the green K080850HD, or the black K080850RPM.
Rock auto has this K080850RPM belt for an unbeatable price 23 Oct 23.

These numbers cross reference to several other belt makers part numbers. The 852 is fairly common and kept in any parts store. The 850, 850HD can be ordered in most parts stores. The 850RPM is hard to come by and is $120 when you find it.

https://www.gates.com/power-transmis...-v-belts/c/104

https://www.gatespowerpro.com/Comerg...ctID=855298855

https://www.gatespowerpro.com/Comerg...ctID=855298852

https://www.gatespowerpro.com/Comerg...ctID=855298850

Thanks for the very informative reply. I just wanted to confirm I shouldn't be running a different belt for the smaller upper pulley and that the stock belt was the correct one, especially because I'm going to an even smaller pulley now.

You are welcome.

If you want to compensate for the smaller pulley go with one of the 80850's.

The stock belt will work. And certainly will get you home if you lose a belt on a road trip.
Keep your old one in the car for emergencies or know that stock belts are readily available at most parts stores.

Does anyone know where one could find the K080850RPM? I have been looking a few weeks and can't find one. Thanks!

got mine on amazon

part # is k080850hd

I have a 2.3 FP upper pulley and the correct belt for mine was a Gates 080852. It doesn't slip and works great.

https://www.napaonline.com/en/p/NBGK080850RPM

Rock Auto has them for a great price.

Pretty good info

Gates Updated links. Not sure how long they will be valid.
Stock belt https://www.gates.com/us/en/search?text=K080852

Shorter belts below.
https://www.gates.com/us/en/search?text=080850 Black belt base quality. Apparently no longer available at Gates but still cross references to other belt makers numbers.
https://www.gates.com/us/en/search?text=K080850HD Green Heavy Duty belt .
https://www.gates.com/us/en/search?text=K080850rpm Black extreme duty belt for racing.