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Ring Choice: Mahle/BMW NOS, Deves, ???

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I found a NOS set of Tii 10-1 and they came with rings in little BMW boxes. I never liked stock rings in the day - the one-piece oil rings in particular - and always had best luck with Deves, even though they can be a little rough on the bores.

 

What are 21st century ring choices looking like? Block is yet to be honed so I can pick pattern.

 

Thanks,

 

a

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I purchased a set of NOS Mahle Pistons for my 69 and proceeded to break one ring during installation so I bought a set of Deves to replace all (4) piston rings.  So far, so good. 

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I tend to use Deves rings as replacements for most pistons. With new Mahle pistons, I just use the stock Mahle rings that come with the pistons. Make sure you measure each ring gap and file as necessary.


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26 minutes ago, Schnellvintage said:

I tend to use Deves rings as replacements for most pistons. With new Mahle pistons, I just use the stock Mahle rings that come with the pistons. 

 

I have always used Deves as replacement rings. They seal up great and don't burn oil.

 

However, I rarely buy pistons that come with OEM rings and I feel sort of stupid throwing a set of factory rings out...but something...I don't know...

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(edited)

Here's what I found when exhaustively researching piston rings a couple years ago for my own build. Most of this is based on "internet opinion" but seemed consistent enough that I made my decision based upon what I read and several builders that I spoke with or worked with.

 

Deves rings are pretty good and reportedly very forgiving. If you're not feeling 100% about the quality of the bore / honing, they might seal where other rings won't. They're on my list of rings worth considering.

 

I decided I wanted OEM rings for my own car no matter what (back when I was considering used but very nice 10:1 90mm Mahles) . The rings on Mahle / BMW pistons are manufactured by Goetze. It took some doing, but I found a set in a correct 89.97 / 90mm bore to fit the Mahles I had in my stash. Shoot me a message if that's the size you need. There's a trick to getting them.  The Goetze rings might take longer to seat, but I feel good about the longevity of them.

 

If you're using brand new Mahle pistons, I'd definitely keep those rings on them. They work beautifully, as long as the hone work is correct and good. Want them to seat faster? Don't put ANY oil on the piston, except a tiny bit on the skirt portion. They'll be seated before you're finished setting the ignition timing. 

 

In the end, I ended up using brand new 90mm 10:1 Mahle pistons and the Goetze installed rings that came with them. ZERO regrets. They work great and don't burn oil.

 

I also looked in to TotalSeal rings and read enough things about their dynamic properties (potential flutter) at speed, even though they provide outstanding static leakdown numbers. 

 

I figure the factory stuff lasts for many many miles and I'm glad I used OEM stuff. If I was on more of a budget and just re-ringing some good but used pistons, I'd be satisfied with Deves rings. 

 

YMMV. Like oil, everyone will have different opinions. These are just my feelings on the matter. I like the OEM stuff when I can get it.

 

More importantly - If you're installing used pistons, check the ring land clearances and ring gaps TO EACH CYLINDER. THAT'S the crucial stuff you don't want to take for granted!

 

Last week I posted permissible tolerances per BMW. If need be, I can find that info again and repost it. 

 

Edited by wegweiser

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Hi Paul,

All new parts here, pistons, rings and bores. Clearly the new Mahle pistons are older but not from the 70's and the rings are in BMW boxes marked "made in Turkey."

 

Is this what's making me nervous?

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(edited)

That Turkey thing could be the cause of your trepidation. If they're Genuine BMW rings, I think you'll be fine. Even China and Taiwan can make superb quality parts if the client (the corporation, whether it's BMW or Apple or whoever) gives them the money and instructions / specifications to do so. Poor quality boils down to the corporation dictating the production and profit margin more times than not.  I trust BMW / Goetze / Mahle on this one. I'm very surprised that the rings weren't already installed on the pistons from Mahle. That seems odd. I have NEVER seen new Mahle pistons without rings already installed, - and I've probably seen hundreds of them over the years. Hrmmmm.... weird. 

 

To be clear, I never refer to myself as "an engine builder" but rather an engine "assembler". There are folks out there that have built and tweaked hundreds of M10s... I am not one of them. I think I'm competent, but by no means a master. Those guys have forgotten more than will ever know. I've been taught a few select tricks and techniques by a few of them...but that's it. 

Edited by wegweiser

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The innertubes indicate Mahle is a big deal in Turkey, having several factories going, making pistons for MBZ and BMW, superchargers, piston liners, pins, etc. One plant has 820 workers.

 

Therefore.....what? Use the rings or replace with???

 

I totally agree about using Deves if the bores are less than perfect. No discussion.

 

But for new?

 

 

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The short answer:  If it were MY engine? I'd use the BMW/Mahle supplied ones you have, but check all clearances and ring gaps before final assembly. I'd do that with ANY piston and ANY ring combination, no matter where they were made or even if I paid $4000 for them from the collection of a  BMW Motorsport engineer. :)

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Turkish rings would make me skeptikal, too-

 

the only few sets of Mahle pistons I've purchased

have come rings pre- installed, too.

At this point I'd measure hell out of everything, being

especially critical of the pistons- are they really Mahle?

 

Then, huh.  Like everyone else, I use the factory rings

on fresh bores, and Deves on everything I don't rebore.

But that's not to say that Deves won't seal wonderfully on 

a fresh bore, either....

 

Personally, being of Greek extrafication, I'd have

to pass on the Turks.  But that's personal.

 

heh

 

t

keeping ancient feuds fresh

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Greek eh? That explains the intentional extra "k" in skeptical. Sneaky! :D

 

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Until 2015 I used Perfect Circle which was then bought by Mahle. Ever since I get Mahle aftermarket (which is Perfect Circle). KS (Kolbenschmidt) also has a very good choice of Piston Rings

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1 hour ago, wegweiser said:

The short answer:  If it were MY engine? I'd use the BMW/Mahle supplied ones you have, but check all clearances and ring gaps before final assembly. I'd do that with ANY piston and ANY ring combination, no matter where they were made or even if I paid $4000 for them from the collection of a  BMW Motorsport engineer.

To clarify my answer, the Mahle Pistons I purchased were in unopened boxes with Mahle stamped rings on them. I accidentally broke one ring during installation then tried (unsuccessfully) to find replacements using the Mahle part numbers listed on  the rings.  The Deves replacements were recommended to me, so I called them and they made a set for me without any problems (turnaround was fast).  They fit well on the Mahle piston ring lands and had the proper cylinder bore fit.  The only tricky part was the multiple piece bottom ring set.

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Now that you mention it, there was that bad thing that happened to me at the Hagia Sophia once....

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