Due to rust on my steel frame, the threading which holds the BB is shot. My LBS is considering using a reaming tool which creates new threading but will require me to use an Italian BB from now on.
Does anyone have an opinion as to:
1. Is it worth attempting the reaming? and
2. If the reaming fails, is there anything else I can do or is my frame shot?
Thanks,
Paul
Bottom Bracket Question
Thu, 04/28/2005 - 2:50am
Thu, 04/28/2005 - 5:49am
#1
Reaming
Reaming the bottom bracket interface of frames is quite commomly done when installing bottom brackets on an old and in some cases poorly (pre)prepped new bike frame. It's a good way to clear out the sediment accumulating in the threads.
I'd be inquisitive why the bike shop recommends changing the thread orientation. That seems a bit severe. Frames and bottom brackets can tolerate a little rust. It also helps to regrease the bottom bracket threads (i.e. 1, 2/per year) if you ride in alot in wet or even in very humid weather.
Sun, 05/01/2005 - 5:47am
#2
BB prepping
Reaming is not 'a good way to clean out the threads'- it actually ruins the old threads by making the hole bigger. You mean 'facing', which is done to evenly square off the outer edge of the BB shell, and 'chasing', which (as mentioned earlier) cleans out the threads.
Thu, 04/28/2005 - 6:08am
#3
chamfering
If the reaming fails, the frame can be chamfered to accept a BB that threads in on itself, like this:
http://www.bikepro.com/products/bottom_brackets/mavic.html
Thu, 04/28/2005 - 9:39am
#4
Available ???
Evan, I thought you'd know that Mavic bottom bracket isn't available (or certainly readily available) anymore.
The BikePro site appears before our eyes, but is a ghost-site.
If needed, Italian threading is better, since far more choices in bottom brackets, such as a Phil Wood with appropriate mounting rings.
Thu, 04/28/2005 - 12:31pm
#5
Available!
Got one in my parts collection, and they show up *very* frequently on eBay - maybe because they're so damn heavy nobody really wants to use one. Maybe also because of the leap of faith required to chamfer the BB shell?
Got a Bike Pro catalog too, LOL.
Thu, 04/28/2005 - 6:27am
#6
Italian threads
>>> Due to rust on my steel frame, the threading which holds the BB is shot. My LBS is considering using a reaming tool which creates new threading but will require me to use an Italian BB from now on.
<<<
Technically, it's not reaming, in which a cutting (but not threading) tool is used to expand an existing hole to close tolerances. Instead the LBS will use a tap to cut new threads.
The Italian tap has a larger diameter than the English threads, so it can cut new, clean threads if the existing threads are completely shot, for whatever reason.
This is a fairly common procedure - search rec.bicycles.tech. I did it myself on one of my frames.
>>> Does anyone have an opinion as to:
1. Is it worth attempting the reaming?
<<<
It depends on what the LBS is charging and how much you like (love) your frame. You'll need to buy a new Italian-threaded bottom bracket too. It's worth it if you really like the bike and the labor charge and bottom bracket aren't too expensive.
>>> 2. If the reaming fails, is there anything else I can do or is my frame shot?
<<<
Cutting new Italian threads shouldn't be a problem if the LBS has good mechanics experienced at this (and it doesn't take a huge amount of experience). However, if they do goof it up for any reason, your frame will need a new bottom bracket shell - a job for a frame builder, not a bike shop mechanic.
If you REALLY love your frame, you could have a frame builder braze or weld in a new bottom bracket shell, but, in my opinion, the frame would have to be really special to choose that course. Sheldon Brown had it done to an old bike:
http://sheldonbrown.org/raleigh-baylis/index.html
Thu, 04/28/2005 - 8:57am
#7
Threadless
"If all else fails, you can use a threadless BB.
http://tinyurl.com/9uvll
But I'd try chasing the existing threads first.
""Chainwheel"""
Sat, 04/30/2005 - 7:38pm
#8
thread repair
"Hello Paul:
As a long time industrial mechanic and machinist, I have taken many chips to bed w/ me ( no ,not a kinky obsession) .But more as a result of failure to properly clean one's work clothes and person of metal cuttings and chips flying off production machines.I would concur W/ ""chainwheel"" I would ""chase"" the tread first. ""Chasing"" in both male and female threads, is the process of ""cleaning an already existing thread. there is very little cutting involved. From your post it's difficult to detemine the severity of the problem.Most likely"" rusted "" threads can be repaired to the same size by chasing. If the thread is too far gone then one of the ways to repair a dameged thread is to cut the thread out to the root diamer, or more, to where it can accept the next larger size thread.to be done correctly all of the existing thread should be removed. I would not try to tap a new thread over an already existing thread. so when you say ""reaming"" you mean to say reaming and tapping.As I suspected and learned from the other posts, the Italian thread is larger in Diam. then the one you presently have.The reamer is a tool intended to remove small amounts of material and to make a hole very close to perfect round and accurate size (diameter)Something not possible w/ a drill. in this case ,I suspect that the reamer and tap are in tandem as one unit( I have manufactured many specialty tools for use on my bike,as well as many custom made brackets and attachments). The only drawback to this process is that the BB will lose some wall thickness, Hope this helps ...Ciao Tony"
