Gates Belt Size Confusion with 2.4 pulle and 90mm idler on TVS2.3

[tjsparky]

Could you tell me what belt to run with a 13 GT500 tvs 2.3l supercharger. It will have a 2.4" upper pulley and a 90mm idler from VMP. It appears we still use the stock belt on the install of these 2 items. According to Gates the RPM belt that replaces stock is... K100837RPM,

https://www.gates.com/us/en/ymm/sea...2013&make=Ford&model=Mustang&engine=V-8+5.8+L

and here...

https://assets.gates.com/content/da...428-3291-rpm-belt-dimension-list-newbrand.pdf

Depending on what you look at it is different numbers in size outside circumference 84.25” or effective length of 83.66” for the stock gates belt of K100837RPM.

I see that a lot of people go with the gates K100840RPM belt with these same mods and its numbers are outside circumference 84.06” or effective length of 84.625”

So I'm a little confused on which to use.

Thanks

 

[PM-Performance]

I ran the 84 and went down to the 83.7. All else the same except on an 07
Honestly I think an 83 would probably hold better.

more feedback is that the Racing/Rpm belt is a little too hard potentially, and the green “may” be a better option.