I am thinking about getting new idlers on my Cobra to replace the stock ones. It seems that it is popular to get two 100mm idlers and one 90mm idler. I was wondering why this is because it makes more sense to me to get three 90mm idlers as a direct replacement for the stock ones. Thanks!
Stock Idler Replacement
- Thread starter WireMesh
- Start date
I've never understood this either - I assume it has to do with a 100mm idler just being larger and more robust. PO of my car went with three UPR 90mm when one of the stock pullies failed after he added the 2.76/100mm billetflow. If your car is pullied, you should definitely upgrade. He gave me the stockers, including the one that failed, not pretty - they are just cheap castings.
I'm planning on upgrading when I get a pulley but I am not doing the auxiliary idler so I do not know what is the best option for me. Because if I went with 2 100s and one 90 I would have no idea what belt size to get...
EDIT: Metco says add .5in of belt for each 100mm idler. Source: http://www.metcomotorsports.com/supercharger_belt_length_recommendations.htm
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subn
Bigger idlers = less slip? In for an edumacation...
Bigger idlers = less slip? In for an edumacation...
Same here... I have no idea why... Only thing I can think of is that bigger idlers can spin slower which would put less wear on them and therefore make them last longer...
Side note: could I replace the three stock 90mm idlers with 100mm idlers and still fit the stock pulley cage on? I assume so, but I just want to make sure.
The more belt you have contacting idler/pulley the more friction thus less slip.
Even if there is just more surface on the stock idler locations? How would that help belt slip on the supercharger pulley...:shrug:
Thats what I read from searching this topic on here but I never found anything super clear... I am a little slow... From what I gathered the larger surface areas created more contact points for the belt which equaled less slip. Furthermore, you can use 3 100's and 1 92 and a 2.93 pulley but you would have to modify the stock cage by trimming a section out.
I just ordered new idlers myself and I got the 3 90mm and 1 100mm for my aux idler. im still on the stock ones with over 100k miles I don't know how they haven't exploded yet lol. I got the billet pro shop ones from lethal the price was good and they look good. Cant wait to install them
I figured it had to do with the bigger idler spins less RPM, so it would increase bearing life and lower speeds of it, which is always a good thing. I don't see how an idler being bigger can reduce belt slip. :shrug: Your whole goal is to reduce slip on the blower pulley and the lower pulley. How can an idler that spins freely reduce the slip. Now if you had a larger idler right under the blower then you would be getting more belt wrap and could reduce slip in that way.
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With the auxiliary idler you're getting more belt wrap.
I am not talking about the auxiliary idler; that makes perfect sense. Most of the kits replace the stock 90mm idlers with 100mm ones though... Why? Because that is not helping belt wrap...:shrug:
Most 4-piece kits have either 3 100mm idlers and one 92/90mm idler, or 3 92/90mm idlers with one 100mm. Metco, for example, gives you the choice of 3-100mm and 1-90mm or 3-90mm and 1-100mm. And single or double bearings. As far as why the 100mm size, I've never heard the question raised before. You stirred my curiosity so I tried to call Metco but only got a recording. I might try again later. It's a good question.
I see that you don't want an auxiliary idler. Is that because you want to use the stock cage? Because if you go with an upper than is 2.90/2.93 or smaller you want more belt wrap to minimize belt slip and that will require an auxiliary idler. There are people who have gone as small as a 2.76 with no auxiliary idler and they claim no belt slip, but it isn't recommended.
EDIT: I've read through a number of threads from the past, and all talk about increased belt wrap with the larger 100mm idlers. I have to belief that belt wrap is the reason for the larger size. There's a reason why you don't see any idlers for the '03-'04 Cobra smaller than the factory 90mm. This comes right from Metco's site. "This kit includes a black hardcoat-anodized 100mm idler pulley, which is the larger size that serves to maximize belt wrap in applications using stock size supercharger pulleys." I would have to assume that this would apply to smaller size supercharger pulleys as well. It's got to be for better belt wrap for reduced belt slippage.
I see that you don't want an auxiliary idler. Is that because you want to use the stock cage? Because if you go with an upper than is 2.90/2.93 or smaller you want more belt wrap to minimize belt slip and that will require an auxiliary idler. There are people who have gone as small as a 2.76 with no auxiliary idler and they claim no belt slip, but it isn't recommended.
EDIT: I've read through a number of threads from the past, and all talk about increased belt wrap with the larger 100mm idlers. I have to belief that belt wrap is the reason for the larger size. There's a reason why you don't see any idlers for the '03-'04 Cobra smaller than the factory 90mm. This comes right from Metco's site. "This kit includes a black hardcoat-anodized 100mm idler pulley, which is the larger size that serves to maximize belt wrap in applications using stock size supercharger pulleys." I would have to assume that this would apply to smaller size supercharger pulleys as well. It's got to be for better belt wrap for reduced belt slippage.
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Yes, I would like to keep the stock cage. I am going to go with the Billetflow 2.93 non-slip pulley to hopefully minimize belt slip. If I do end up getting some I will buy the Whipple belt tensioner. It is a tiny pulley that goes right under the supercharger pulley that fits under the stock cage. It should give me the belt wrap needed if I am having problems with belt slippage
Sounds like a good plan. You'll be happy with the Billetflow 2.93 pulley.
Now I just have to figure out if I should replace the stock idlers with 90mm or 100mm Metco dual bearing ones... And hope that I do not have to spend $275 on the Whipple belt tensioner.
I don't get the love for the stock cage - but to each their own. I think it's ugly and an exposed billet pulley and matching billet idler looks badass.
I like it to look stock and I think it looks cleaner for some reason...
Are you gonna have the cage painted or powder coated? I think that would make it look cleaner.
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