The New And Improved Unofficial R65 Forum V2

Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: suecanada on August 09, 2009, 02:07:00 PM

Title: Tubes with & without the nut used on inside rim.
Post by: suecanada on August 09, 2009, 02:07:00 PM

It's very hot and muggy here and I have little incentive to do anything. So, having bought brand new metzler inner tubes and having a second set of rims, I decided to measure the exposed tube stem with and without that pesky nut installed on the inside of the rim. I counted exposed threads but not the very top starter thread. The nut is pesky as I blame it for making it very hard to get air properly into the tire and to check pressures. I've never determined if my installer put on that inside nut or not. We have discussed this before and Nhmaf found that his exposed valve stem is not quite 1/2 inch above the rim and the rear is the shorter of the two.

So I put the nut on my new tube with that convex washer and pushed it through the rim hole. Then I measured the number of threads exposed. Rear was 8 threads exposed; front was 9 threads exposed.
With the nut removed and convex washer remaining: rear was 13 threads and front was 12 threads exposed...perfect!

My bike has rear 8 threads making it hard to use and front has 10 threads exposed so is much better.

Science class is dismissed!
Is there any reason at all to install the second nut on the inside of the tube? I can see having the outside nut on but not screwed all the way to the rim, to prevent pushing the valve back inside.

Title: Re: Tubes with & without the nut used on inside rim.
Post by: montmil on August 09, 2009, 04:31:51 PM

I'm thinking the interior nut may be helpful in preventing the tube from slipping around the rim but only if you're perhaps riding an off-road bike running fairly low tire pressures... compared to our R65's 30-ish psi for road work.

I believe I left the nut off last time I installed a front tire on the '81.

Monte

Title: Re: Tubes with & without the nut used on inside rim.
Post by: Justin B. on August 09, 2009, 06:42:41 PM

When I put the new front tire on the "Dawg" I removed the inside nut.  We'll see how that goes if I ever get it finished and start riding it...

Title: Re: Tubes with & without the nut used on inside rim.
Post by: nhmaf on August 09, 2009, 10:01:18 PM

No inside nut for me - I agree that if riding offroad and using lower pressures, it might be handy to have a tube-lock nut on the inside, but for normal, non-motocross riding, no inside nut and just the one on the outside against/under the valve cap.