# Deda Newton 31.7 bar work with 31.8 stem?



## cincytri (Sep 21, 2007)

I am considering the Deda Newton Deep (Belgian) bar and wanted to be sure that it will work with standard 31.8 clamp stems. Can anyone verify that the 31.7 Deda Newton will work with 31.8 clamp stems made by other brands? Thanks in advance for your replies.


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## bdaghisallo1 (Sep 25, 2007)

Yes. The O/S standard is actually 1 1/4 inch which works out to 31.75mm. Deda, the first in the O/S market, chose to round down to 31.7mm and the others chose to round up to 31.8mm.


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## frdfandc (Nov 27, 2007)

Yes. The .1mm is not much of a variation to affect clamping ability. You shouldn't have any issues using that setup.


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## Kerry Irons (Feb 25, 2002)

*No variation*



frdfandc said:


> Yes. The .1mm is not much of a variation to affect clamping ability. You shouldn't have any issues using that setup.


There is no variation. As bdaghisallo1 noted, these are just two different references to the same size.


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## frdfandc (Nov 27, 2007)

There is a variation. Its in how the manufacturer measures/labels its product. If there was no variation, then all measurements would be exact from manufacturer to manufacturer. 

Just went through this in my Park Tool Instructors manual.


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## backinthesaddle (Nov 22, 2006)

frdfandc said:


> There is a variation. Its in how the manufacturer measures/labels its product. If there was no variation, then all measurements would be exact from manufacturer to manufacturer.
> 
> Just went through this in my Park Tool Instructors manual.



There is NO variation. It's the 1-1/4" standard, just like what what stated above. Just because you read it in a book doesn't mean that it's correct.

To the OP, you can mix and match OS stuff as you please. I'm riding Deda Newton Deep OS bars with a Thomson X4 stem on both of my bikes now, and have done it this way for 5 years on every bike I've owned. Never had an issue!


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## zriggle (Apr 16, 2008)

frdfandc said:


> There is a variation. Its in how the manufacturer measures/labels its product. If there was no variation, then all measurements would be exact from manufacturer to manufacturer.
> 
> Just went through this in my Park Tool Instructors manual.


Google Knows All


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## acid_rider (Nov 23, 2004)

variation or not, I use Deda Newton (shallow) bars with a non-Deda stem, no issues. Likewise on my second bike I have Deda Newton stem with non-Deda O/S bars - no issues. Deda is just trying to make you buy their bars and their stem as a package. Nice try Deda. No need for that.


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## Pancho's Balls (Aug 15, 2009)

I will be the 8th person to say "yes." Yes.


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## frdfandc (Nov 27, 2007)

double.


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## frdfandc (Nov 27, 2007)

backinthesaddle said:


> Just because you read it in a book doesn't mean that it's correct.



And just because it was posted on the web doesn't mean that its correct either. 



If there is no variation, then why is one labeled 31.7 and the other is labeled 31.8.

http://velonews.com/article/8015 - read the 2nd paragraph. Yes its due to manufacturers wanting you to run their entire product lineup, but that isn't always the case.



Not trying to get into an internet dick measuring contest, just making a point.


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## dave2pvd (Oct 15, 2007)

frdfandc said:


> And just because it was posted on the web doesn't mean that its correct either.
> 
> 
> 
> ...


The Zinn article points out that dimensional variation in mm labeling (31.7 --> 31.8) is a non-issue. Like the other poster said, it is derived from the inch standard.

Perhaps manufacturers ought to state their component dimensions to 3 decimal places? Now that's what I would call Euro


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## DIRT BOY (Aug 22, 2002)

frdfandc said:


> And just because it was posted on the web doesn't mean that its correct either.
> 
> 
> 
> ...


OP, Like others said, Deda runs down and all others round up.

*NOW*, I as others have seen very very minimal cases where the bars or stem are not 31.75.

But this has never effected the ability to use the given part with another part. Its usually so minute, you would never know without precise tools.

So, back to your original question. Yes, they are interchangeable, no if and or buts!

Deda came up with the sizing and rounded down. All others rounded up and use this not as the standard we know as 31.8 for 31.75!


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## Pancho's Balls (Aug 15, 2009)

The fact that this thread is alive, with someone offering a dissenting opinion, is awesome. Jesus-fcuking-christ, it'll fit. There are manufacturing tolerances and for all intents and purposes, a 31.7 and 31.8 bar and/or stem are the same diameter.

"Deda would prefer people use Deda stems with their bars, but the warranty isn't contingent on the bars and stem being from Deda. They also say that even though Deda measures clamp area of the center section of their bars as 31.7mm, it is essentially identical to other manufacturers' 31.8mm (save manufacturing tolerances). Both are 1.25", just Deda takes the metric fraction 31.75mm and rounds down, while everyone else takes the same fraction and rounds up."

That's from Competitive Cyclist, so if they're throwing out misinformation, then there is actually a 31.7/31.8 conspiracy out there. Chances are it's not.


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## Fogdweller (Mar 26, 2004)

NO!! DON'T DO IT!!! 

Just kidding. I'm running Newton bars on a Thomson stem on my commuter, both of bulge variety, and have had no problems. Just do it.


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