Mike R

I did a posting on the belts, the 114.5 and 115.3 are the same belt, the dimensions are the inner and outer measurments. THis is according to gates and their catalog. I got interested and tried to get a looser one and found this out. Sorry bout that, the next micro v belt larger and smaller are about 2" different in length.

Woody

 

This thread wasn't about the water pump pulley failing... it's the idler pulley.

 

The ASP idler pictured isn't on my car. It was the replacement part sent to me by LET (only correctly sized idler Jerry could get his hands on at the time). He told me it was used, with about 2k miles on it; when it showed up at my mechanic's shop, he wasn't keen on putting it on the car - called me and said "um, it looks like they pulled a part out of a junk yard..."

 

correct - my LET idler is not rusty looking either, although it is steel. The ASP idler sent is rusty as hell.

 

It sounds like to me, we need to be using the stock idler pulley and source a new belt. Use a gauge to check the deflection is the correct tolerence after the install.

 

ASP idler is a hair under 60mm; call it 59 or 60.

 

I have called the idler pulley manufacturer and they have confirmed the 15,000 RPM speed limit. He is looking to find a 20k+ rpm bearing that is a direct replacement that we can use. There are a number of options for us, so give him a little time to find the replacement.

One of the NSK 6301's is showing a grease RPM limit of 20,000.

 

Except for the Code3 pulley.

155 / 65 = (2.38) * 6K = 14,280 SC RPM

 

I can see where your mind's at, and your answer is correct, but the corresponding math is not. You quoted the S/C rpm; this thread is talking about the idler pulley rpm.

The answer is correct because the Code3 pulley approach is independent of this issue, as it maintains the stock crank pulley, stock idler pullies, etc. So, if you have the C3P S/C pulley and have your stock idler fail, presumably it would've failed anyway.

From BrianBrave's math and Jerry's post, sounds like this is a bearing issue - the bearing spec'd by LET and others isn't rated to handle the rpms; a higher-rpm compliant bearing needs to be spec'd.

 

OP - LET will replace the failed pulley and the damaged crank pulley (when we spoke you didn't mention the crank pulley was damaged).

I'm still not 100% sure that the bearing was at fault due to over spinning.

Over torqued idlers have been seizing for many, many years.

I have personally put 30,000 miles on my C32 with the same bearing that you had fail with no issues at all. Others have done the same...

Now, take a simple Google search for "Seized idler pulley" and you get tons (7,090) of listings where idlers have seized.

Google Search

There is even MBWorld listings for C32's without our product installed that have had a seized idler.

Link to listing on MBWorld

I understand your frustration and I did everything I could to help get the car on the road. I have taken proper measures and offered to replace the LET parts on the car.

 

Parts were installed Memorial Day weekend 2008, with LET-supplied instructions, proper tools, and the MB DVD shop manual.

If a bearing is rated to 15K max rpm, and is intermittently subjected to 18K+ rpm over the span of several months and thousands of miles (8+), isn't the logical conclusion for premature failure that the bearing couldn't handle the application? If 20K bearings are available in this application, why were those not initially spec'd for the LET Motorsports idler pulley?

 

Woody,
I am going to disagree with you on the belt lengths. According to the chart from your earlier post the 4081150 is 114.5/115.3 and the 4081153 is 115.3/116.1. (I am doing this from memory so dont flame me too bad if I got a number wrong)
I took everything apart last night to install the 115.3 Gatorback and then couldnt find the sucker. I hate it when I try to get organized. I put everything back to gether and then while cleaning up and putting things away, I literally bumped into the belt hanging on a rack(that I looked a 4 time for the belt). I wasnt in the mood to tear it all down again so I will do it today. I will get the measurements of both the factory and the 1153 belt and pics of the position of the tensioner pulley.
It sounds like we may have found the culprit with the rating of the bearing though. Both NSK and Timkin are very good bearings. But if we are operating them outside of the rated spec, we are going to have failures. It's just a matter of when.

Jerry,
When you find a higher rated bearing, could/will you be offering the ideler pulley as a 'high speed' option pulley? I would like to swap mine out for a higher rated bearing pulley before I have issues.

MikeR

Edit: data from Woody's Goodyear link.

PART NUMBER METRIC PART NO. NO RIBS EFFECTIVE LENGTH OUTSIDE LENGTH
4081145 8PK2910 8 114.5 115.25
4081153 8PK2930 8 115.35 116.05

 

It was an LET design issue and will be replaced free of charge.

 

I would be content with just replacing the bearing in the idler pulley - but with a replacement rated at 25,000 RPM.

 

Brian, I agree. I thought about that right after I hit the submit button. The pulley is good, just press in a new bearing.


Thanks for your continued support Jerry.


MikeR

 

Just the last couple of mornings I have had a "sqeek" under the hood while warming up. I have not been able to find the source but I am now quite concerned the source has been identified. I may be able to come up with the correct bearing but if I have to replace it I expect a refund from LET. As my forum history shows LETs' 185mm pulley set up has all ready cost me $600.00 out of pocket, for tow and belt replacement costs. I don't think I should have to invest anymore in their product.

 

We might have to increase the idler pulley OD to 70mm (vs. 60mm). We are having issues finding the right bearing. If we go with a 70mm idler and use a 17k bearing, then we will be good.

We should also use 6250 as the RPM, not 6000. The 70mm idler will be good with a 17k bearing at 6250 rpm on a 185mm setup.

 

If you go and purchase the bearing on your own, you will not get refunded.

Please wait until we find the bearing and we will ship it to you.

 

Sorry about the misfortune Brett! That caused a crazy amout of damage! This is scary scary stuff guys!! I have to be honest, I am now afraid to drive my car the way it stands now. It all makes sense to me about the bearing not being able to handle the increased RPM's and it seems like this is happening to a lot of you guys.......I really hope someone comes up with a quick solution!

 

Thanks Chris - yeah, the damage caused by the LET pinball (formerly LET idler pulley) sucked big time. I realize that's a freak thing... it just as easily could've missed anything vital, and it simply would've been a "replace the seized bearing, and replace the chewed up water pump" job. As it was, it was around $2,200ish for the tow and repair... $2,200 that could've gone towards more mods instead! (sigh)