I've seen mention of different drive belts for 15% and 17% pulleys. What are people using with the M7 16% pulley? Stock drive belt or other?

 

 

Thanks. Yeah I want to change my belt ASAP--got 60,000 miles on it--though I bought this MCS used with 37K on it--not exactly sure when the drive belt was last replaced or with what. But just trying to plan ahead.

The only belt tensioner tool I see is the Ultrik from MINI Mania. I read a few threads here about just removing the belt tensioner instead of getting the "proper" tool to loosen it.

 

Richard, I have the M7 16% and the stock(lighter) crank pulley. I use the NAPA 060535 as it puts the tensioner right where it should be.

Buy the tensioner tool, I think Outmotoring sells it too. It's definitely worth it.

 

using the JCW belt as M7 suggested

 

The JCW belt is too large for a 15%. JCW is closer to 12.7% than the 14.7% often mentioned. It definitely would be too large for the m7.

NAPA 060535 is right for the 15%, so it should only be just slightly too large for the 16%, probably OK.

 

hmm...what's the length of the NAPA belt in millimeters?

 

The factory JCW belt works perfectly with the m7 16% pulley. That's what I run on mine, tension is perfectly acceptable.

The JCW belt is also what m7 recommends. I e-mailed them and requested input following less desirable performance from other belts.

If you mount a JCW belt with a m7 pulley and the belt is too loose, I'd be suspect of the tensioner not working properly.

 

This is what I found as well.
With the 060535 I am able to see the entire index hole on the tensioner.

NAPA lists their belt being 1375mm, and the JCW belt says 1374mm. They are obviously using two different methods of measure because I tried both, one right after the other and I could only see the entire index hole with the NAPA belt.

If you reference my response above to mini_macky, that was with a brand new tensioner.

Are you able to see the entire index hole on your tensioner?

image courtesy of CmdrVimes

 

Great info guys! Thanks! I actually PMd Randy at M7 last night and he was going to confirm the length with Steve at Steves Auto Clinic over the next few days. Seems as long as the 16% pulley has been out, there would have been some consensus already on the best belt to use or even on their website? Not knocking them, just trying to get useful info to anyone in the same position as myself.

Richard

 

factory JCW belt has been working fine thus far

 

I'm sure it works.

But are you getting the performance that you could with a belt that doesn't slip?

Probably not.

Been there and done that, with the JCW.

Actually saw the difference on the Lucky Dog Garage dyno. And that was with the 15%.

 

Can you PM me where you get yours? I tried entering the NAPA number over at http://www.napaonline.com/MasterPages/NOLWelcome.aspx and it couldn't be found.

I will be ordering the belt tensioner tool from Outmotoring.

Richard

 

 

Your local NAPA store should have it in stock...
...this works too.

 

All belts will vary - even the same make and model. That's a fact, we pissed and moaned about it countless times at the track when we ran enduros. If we unexpectedly broke a belt and didn't have a spare, running to the local parts store to buy a X model of Y brand typically yielded different results each time. Sucked - having to go to the parts store and manually measure belts to find a match - Ugh... So any belt is capable of slipping depending on the normal variables (car component condition, temps, belt construction variances, etc.).

Anyway, yes, the index hole was (and is) entirely visible.

I was running a Dinan belt (spec'd for a 17% pulley) and it provided less than stellar results. First shredded in ~3K miles of use. Second was irregular and caused freakish tensioner chatter until the belt warmed and expanded. So, that's when I poked around and found that with the ~15% sized pulleys, the JCW seemed least questionable in terms of longevity and performance.

To argue over how much slippage?

Meh, that's a limitless conversation. For me it came down to reducing the odds of losing a belt and needing roadside repair or tow, acceptable performance, and a "civil" car that doesn't sound like the tensioner is going to self destruct from too much belt tension.

Other folks will inevitably have different results and preferences.

Flame on!

 

Gatorback 4060537 here w/M7 16. No problems & no slippage.

 

ok expert, let me retract my previous post and state that I actually use a NAPA 060535, cause the JCW was my previous belt 15K miles ago. So it sounds like everything is under control w/o any slip

 

Last question---I hope. When you say" This works too" does that mean this is a different part or the same part?? I'm going to order a couple of them.

http://www.napaonline.com/MasterPage...t+-+Serpentine

 

Sorry Richard, I meant that you could just stop by your local NAPA or use the link from SayGoodbye.

 

Okie dokie--understood now. Thanks!!

Richard

 

For anyone wanting to search for this item online at the NAPAonline store finder, this is the actual part number

25060535

http://www.napaonline.com/MasterPages/NOLWelcome.aspx

I found that my nearest NAPA store has 2 in stock, so heading over there right now.

Thanks everyone!

Richard

p.s. (For those finding this thread from the search engine)
This is the belt you need for 1st gen (2002-2006) Cooper S running the M7 16% pulley.

 

Yep, I called my nearest NAPA store yesterday.

They had it and I had mine in 30 minutes.

This is just a back-up, but you never know...

And that number is what I got, with the 25 prefix.

25060535

 

here's a pic of my M7 pulley with the JCW belt

what's with the gap?

 

Umm, the JCW belt is loose because it's simply too large?