Part 2 of 5: Some bike bottom bracket frame shell openings are too small. Some by a lot. In order for your bike to be any good you must correct this condition. If you are going to use a ream to correct a hole diameter, it is important that you first ensure that the ream itself is the correct size. This is how you do it. Check out:
all right picking up on the themes from our last video we have cleaned this bottom bracket out right here and we have measured it and we have determined that it is way too small it will be it's about five thousandths of an inch too small all right so this is like that's like point 0.1mm okay that's that is so small nothing will ever work in here this bike will never be any good believe it or not so we have to fix it now this is an aluminum bike so it's going to be necessary to ream it you're not going to get this you couldn't take out that much material with sandpaper or anything like that it must be reamed precisely this can also be done on carbon bikes but there are some easier ways to do carbon bikes and we can cover that in another video but for aluminum must be reamed now we've talked on the last episode that we can never assume that this hole is going to be the right size uh so we should measure it and know for ourselves i bought this um handy dandy little ream right here if you want to take a look down here this is uh 40.98 okay and uh it's 40.98mm it says that on the package right well let's find out all right because remember we're not trusting anything here so i'm going to show you guys how to measure now this is okay to use a veneer caliper for this now what a lot of people try to do is they try to stick it like on here on these like knife edges and then they're kind of like rocking it back and forth and trying to find you know like a good place to stop now i'm going to show you guys the down and dirty easy way to measure a ream and you do it like this you let the tool do the work you just hold these flat up against it and you get on two of them you see that right there you get on two of them and what you want to do is you want to hold this one let go of the tool right here and just roll it out see that see how that works and you want to go ahead and you want to just roll it out all right so now you're seeing something here okay right there you're seeing that this ream had some variability let's say it's it's it's basically 40.98 there's two tines on here that are 40.98 i've already measured a lot but a lot of them are slightly under that whether that was intentional or not who cares the finish will be 40.98 okay now we feel secure that we can actually use this to create the proper hole diameter that anything that we put in there is going to be magnifique
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