I think this is a long overdue thread. I am in the market for a 19% pulley, but felt there has been a lot of disjointed conversations regarding belts for this size pulley. There also seems to be a lot of differing opinions on this topic, and now that a lot more people are using the 19%, it would be interested in hearing the opinion. I have done extensive searching and it appears that the most involved users in this discussion have been minihune, Andy, Helix13, RandyBMC, and Bisch. The following belts seem to be the most mentioned:

• Napa 060535 (Appears to be one that some people have used with the 15% and subsequently used with the 19% pulley) Appears to be used by minihune and Andy.
• Napa 060539 (Appears to be one used by Randy and Ryephile).
• Goodyear Gatorback 4060537 (6PK1365) which appears to be used by Bisch and Randy used it once at the Mini Ultimate Challenge.

I would be interested in which ones worked, which ones broke on people, and what peoples recommendations are. Thanks.

 

The Goodyear G'back has segmented ribs. This will allow a tighter flex around the pulley without as much heat build up.

Less flexing rubber = less heat.

see the segmented ribs:

 

I have 21k miles on my NAPA belt and 19% pulley and no problems - in fact it looks new. however, my brother who got the 19% and belt at the same time just broke his belt this weekend. And he's done less miles in that time than I have. I'm having mine checked at helix tomorrow.

 

What happens when the belt breaks? Does the car stop running? Is there any damage...

 

Shut the car OFF and put on a new belt.

 

one of the problems that i have found if the belt pops, is the tensioner may snap into the crank pulley, its not suppose to do this but on two occassions the stop(the little twist in the metal strap with the holes to hold the tensioner back for installing the belt) has broken, then the tensioner grinds its way into the ribs of the crank pulley, with a bunch of gobbed up aluminum in to it, a very nasty mess, i have seen it happen on both stock and 19% pulleys, i have also seen the stop work to... the key is if the belt pops stop immediatly...dont try and limp anywhere, there is also the no water pump issue as well....

as far as belts i have had problems with the gatorback 4060537 and the napa 060539 for some reason it seems to slip causing very premature wear and breakage, i have decent luck with the 060535 but i still feel it doesnt hold up as long as it should, but i do a lot of racing and hard driving, and for the less aggressive driver it would last alot longer, i have been looking for so called racing belts but yet to have success locating one that was any diffrent than the normal belt, also the problem i have run into with the 060535 vs the rest is that it delaminates vs premature wear which is a load failure vs slippage, on a 19% pulley the belt load is near a 100hp at peak rpm/boost.. the quest for a "stronger" belt is still on, i think it will be key to longivity of the belt...

 

hmmmm.

We may need a belt cooler. A Front Mount, liquid to air, air assisted, water mist, sprayed, Cryo2'ed, Peltier fan driven, dual ducted, reverse flowed belt cooler.

...actually, all joking aside, maybe a simple air duct could help on the track. You know, similar to brake ducting...

 

CADDMAN,
Just out of technical curiosity... how did you come up with the 100HP load number?
Is that with A/C on? I was at CMP when you shreaded your belt because instructor want cold air on his feet.

And a couple of comments on that number...
Shouldn't load on belt be measured in lbs for instance? HP is a measure of work.

That implies a 100 HP less to the wheels because it is being robbed by turning supercharger and other engine accessories. Granted the supercharger is helping create a lot more HP, like 175HP...
(100HP stock engine) + 175HP (from SC) - (100HP load) = 175HP (my MCS with 19%)

 

FWIW, I've had decent luck with the NAPA 535 but they have tended to stretch, both with 19% and 15%. I've gotten to replacing the belt with every oil change.

 

aaahh, there's andy. Where have you been lately? I PM'd you last week.

 

if you take notice i approximated, i said near 100hp, i have the actual data somewhere i will dig up and provide, im sure andy can as well...i think we have discussed it once or twice already....

 

and as far as CMP, thats exactly my point, the second belt that shredded in what three laps that was a 060539, i can seem to keep those on the car for long if a drive hard, if a take it easy they do "ok", the 060535 i go for quite a while driving hard, as a matter a fact i have done to other track days and such since and im still running the last belt i put on at CMP... I cant wait to get back to that track i really enjoyed that back half....:smile: I agree with andy they do seem to still stretch faster than a normal belt application....

 

I've had the same experience with the NAPA belts. Once the hole in the tensioner dissappears you can begin to worry.

You guys got me scared so I ran out an bought a Gator for a spare.

 

I'm currently running the Napa 060535, I have approximately 120 miles on that belt, and I can only see half of the last hole on the tensioner. So you mean as soon as that hole goes under the tensioner I should change my belt? For how many miles does the Napa 060535 usually last before I need to change it?

I almost blew stock belt with the 19%, good thing I was able to change it before it completely blew off, since I dont have the stop for the tensioner anymore, somehow it broke off when my shop installed my pulley. So I have to watch out for that one, thanks caddam!!:smile:

 

When you can no longer see the hole I would be looking for signs of slippage or wear. That would include noise, loss of power under high supercharger load conditions, visible wear on the belt, burning rubber odor, etc. I had my 535 on my 15% for a year of hard driving and had no signs of wear, just stretch. The 19% may not stretch it as fast. I've had mine on for about 8 months and 4k miles with no signs of stretching or wear.

Since there are signs of others having problems I would just monitor it and carry a spare. You don't know enough about the age of the belts, driving habits, pulley alignment, maintenance practices, etc. of all those with reported problems to know the true cause of the problem. I change my oil after every track day, every few autocrosses or 2k miles whichever comes first, so a belt swap with every oil change is out of the question and IMHO unnecessary.

Just how often do you change your oil Andy? Show me the numbers!

 

Every 5k with Mobil1 5W30 and an OEM filter. :smile:

 

Thanks for the info Blue.

I have another question:
Is it bad to preload the spring of the tensioner? I have a 1/4" thick spacer in between the spring and the tensioner. My mechaninc put it in there when I was still using the stock belt with the 15% and when he installed the 19% with stock belt he retained it, but now I'm running the NAPA 060535 after I blew the stock belt. Is it a good idea to have the spring preloaded. I'm just worried that preloading the tensioner may cause the 060535 to stretch faster.

 

I just went down and measured it. 1/4" is about the size of one hole. Yea, I think that that's too much but I can't say whether it would be detrimental to the belt or to bearings in the system. Probably not. Given the tendency of the NAPA belts to stretch it will probably just accelerate the initial stretch. 1/8" stretch and you should be well within the safe range. It actually might lengthen the life of the belt as they probably fail after they have stretched far enough that the tensioner can't take up the slack and they slip. It doesn't take much slippage to trash a belt.

Just watch it.

 

I wanted to add that the belt life maybe compromised by the area of contact made by the tensioner wheel. I had a look at mine yesterday afternoon after reading this thread. It appears that the wheel is made-up of two stampings joined in the center. What I observed is that the wheel surface is not absolutely flat. On mine it is shiny in the center of each stamping indicating a high spot there. This would apply an uneven load on the belt with more tension on the center than the sides. Although I can still read the part numbers on the belt it appears there is some wear on them corresponding with the shiny area on the tensioner wheel.
I'm sure I've read somewhere (MIN2) where a tuner in Europe replaces the tensioner with a modified Cosworth tensioner due to reliability issues but don't think they mentioned what issues.


Please have a look at yours, lets see if this is common to all.

 

Thanks for all the good information. I have gotten a lot of PM's on this as well. Based on all the information here and what I have received, it appears that none of the belts really hold up good when tracking and pushing the car. My gut feeling is that no one is keeping the revs down, so it is really exceeding the limits of everything. This most likely doesn't have as much to do with the belts as the driving. Seems some people are pushing almost 1,000 rpm past the limit of the supercharger on a 19%.

The only one that seems to show promise, with no mention of a break was the Gatorback. It seems that only caddman, who admits to tracking the car and running it hard has had a problem of what appears to be premature wear, but at least no breakage. The other belts all have comments about from people experiencing breakage.

Does this summary sound right.

 

Thanks for the info Blue :smile: , any other opinions regarding preloading the tensioner spring? Andy? Caddam? Bisch?

 

Guess I'm the only BONEHEAD here because I don't care for bandaid's to fix problems. As I said someone has already addressed the tensioner issue

"3. Installation of BBR / Cosworth drive belt idler

The Original idler is removed (we found it to be a little unreliable) and our BBR modified high quality Cosworth idler installed."
As far as credibilty goes as to who knows what these are the people who get my vote 100%. http://www.bbrgti.com/history.php oh don't forget to read The Brodie Report.

 

The Brodie Report
Good reading. Thanks for the info.
It looks like the idler is part of their Phase 1 package.
We need to find out if it's for sale by it's self.

 

Guess what? they replaced the stupid tensioner! My previous post alluded to part of the problem causing belts to separate because of belt flexing across it's width generating heat within the belt. The dynamics are simple any engineer that deals with this stuff can confirm it.

 

My belts wear evenly, but they seem to stretch and lose contact: