Hi All -

long story short, buying a car from out of state. had it taken to the local mini dealership for an inspection, and they informed me that it needed a new belt tensioner. I gave the OK on that, and figured it would be a good time to have them put on a new serpentine belt (which they charged me $54 in labor PLUS the $115 in labor to do the tensioner..sigh..)

I requested the JCW since the car has the alta 17% (v2.0) pulley. When they called me to let me know that the car was done...I saw on the invoice that the part number was the stock s belt, not the jcw. I spoke to the tech directly, and he told me that the JCW belt didn't fit, it was too small..so they put a new stock belt on.

Anyone know what gives? To the best of my knowledge, the car doesn't have another pulley (the alternator underdrive?) that would compensate, and allow for the stock belt to fit.

Any advice is appreciated..thanks!!

 

if it's a 17 and there's no overdrive crank pulley.

Get yourself a belt tensioning tool, it's a "must have" for the supercharged Mini crowd.

Matt

 

POST LEFT FOR REFERENCE, BUT BAD INFORMATION ~BOOS

I recently had the same confusion with my 2003 S. I bought the 19% pulley from MINI-Madness and did not realize the 19% referred to the weight of the pulley, not its size. I also replaced the power steering pump at the same time and both the pulley and the pump came with a new belt. I expected a smaller belt with the pulley, but as it turns out, other than the manufacturer the 2 belts are exactly the same.

I am not sure about what may be different with the JCW engine setup, but as I was told by MINI-Madness, Otto's MINI in West Chester, PA and my own garage, any aftermarket S pulley will be the exact same size to accomodate the factory belt and the rest of the components that use the serpentine belt. The weight reduction is what gains you power in its faster spin-up. I also had to purchase a belt tensioner tool off Ebay Motors as my garage didn't have one. The new pulley is in and the new belt fits snug and doesn't slip. And let me tell you, the amount of ***** my MINI gained just from that small upgrade was surprising!

~Boos

 

19% refers to the reduction in diameter of the aftermarket pulley, i.e a 19% pulley is 19% smaller than the stock pulley.
Weight has nothing to do with it.

 

POST LEFT FOR REFERENCE, BUT BAD INFORMATION ~BOOS

Yeah thats what I thought too when I bought it. But when we pulled it out they were the same dimension all around but a very noticeable difference in weight. I called Mini-Madness because I thought the previous owner might have already put one on and I was going to ask for a refund/return. They explained to me 19% referred to the weight (which I could feel holding the 2 pulleys in each hand), I verified the old pulley stamp with Otto's as being stock. The proof was set the first time I stepped on the gas after installing it. Wow did my Mini jump off the line!

Maybe this is a specific instance with the Mini-Madness pulley, but its my experience.

~Boos

 

Sure, a lighter pulley has a lighter rotational mass...

However, reduction pulleys for our superchargers are smaller in diameter, therefore spinning the supercharger faster, creating more boost.

From mini madness site:
PULLEY WEIGHT
Rotational weight is a critical factor that impacts supercharger performance. Other pullies on the market that are made of stainless steel weigh more than the stock pulley! This directly affects how fast the supercharger reaches full boost. Madness pullies weigh less than half the weight while maintaining excellent reliability.

Stock MINI Pulley = 11.0oz/311g
Stainless steel 15% pulley = 16.0oz/501g
Stainless steel 19% pulley = 13.2oz/374g

Madness lightweight 15% pulley = 5.5oz/155g
Madness lightweight 19% pulley = 5.0oz/125g




5oz to 11oz, by my math is not 19%

All I know, is that my M7 16% pulley, is 16% smaller in diameter than the stock pulley.

 

POST LEFT FOR REFERENCE, BUT BAD INFORMATION ~BOOS

Cool. Thats what I thought I was getting. I didn't see how the pulley would make much of a difference if it was lighter but not smaller, but it did. I'd rather it be lighter AND smaller. And yeah I agree the math doesn't add up in that example. That was my confusion, but I can't argue with the results. Maybe someday when I decide to do it again I'll find one that is physically smaller.

 

Thanks to raoul_duke for pointing out my error. I wish I could delete my posts but let me clear this up lest it cause even more confusion. The Mini-Madness 19% pulley is indeed lighter and smaller than the stock pulley. After thinking about what I experienced plus what was posted here, I decided to test it against another Mini. I called another person on post who has a 2004 MCS that is completely stock and asked him if I could measure his pulley. What I discovered was that his pulley was a bit larger than either of mine. Then another look revealed that what I pulled out of my Mini was actually a 19% stainless steel pulley (or something very close to it), not a stock pulley. The techs I talked to on the phone must have misunderstood what I was asking them. But even though the size was the same, the difference in weight made a noticeable improvement. I apologize to the board for the errant posts I can't delete. Thanks for your input, now I finally understand what I have

 

Glad you got it all figured out. Also, while lighter is better, saving six ounces or so on a pulley isn't going to make a huge difference, because the belt isn't just having to turn the pulley. It also has to turn the supercharger shaft & rotors, as well as the water pump and associated gearing. If you compare the weight of that entire assembly with a lighter pulley to the weight of the entire assembly with a stock pulley, I don't think that six ounces is going to make much difference.

Plus, the weight of the pulley is concentrated close to the axis of rotation, as opposed to the supercharger rotors and water pump, so the weight of the pulley doesn't have a big overall effect on the rotational inertia of the whole assembly.