"A Muzi" <
[email protected]> a écrit dans le message de news:
[email protected]...
>>>trg wrote:
>>>>I am replacing the bottom bracket on my 1990 Trek MTB (Deore LX triple
>>>>crankset). The BB measures 68mm and the spindle 133mm in length. I want
>>>>to
>>>>replace the BB with a cartridge, but I haven't found any that are
>>>>68/133.
>>>>The closest I've seen is 68/127. Does a 68/133 cartridge BB exist? If
>>>>not,
>>>>can I use the 68/127 BB?
>
>> "JeffWills" <[email protected]>
>>>122 or 122.5mm would be what I'd expect for that era bike. A 127mm
>>>might be needed to clear fat chainstays- something I wouldn't expect on
>>>your Trek.
>>>How did you measure the spindle length?
>
> trg wrote:
>> From end to end as shown in D in Sheldon's picture (measurement D)-
>> http://www.sheldonbrown.com/harris/images/spindle.jpg
>> In addition, the other measurements (A,B,C) also conform to this spindle-
>> Part Number CR4205 Size Code 3TR-B Shell Width 68
>> D Length Overall 133
>> A Length Left End 42
>> B Length Middle 52
>> C LengthRight End 39
>> http://www.sheldonbrown.com/harris/bottombrackets.html
>> Sheldon agrees with you. According to
>> http://www.sheldonbrown.com/bbsize.html#deore , the spindle should be
>> 122.5mm.
>>
>> I bought the bike used around '92. I suppose it's possible that someone
>> had replaced the BB with too long a spindle. I didn't measure the
>> chainline before taking apart the BB, but I've never had a problem
>> shifting, Although I always had the impression that the left crank looked
>> like it stuck out a bit too much.
>
> Normally the right side is longer.
> When one does not have the correct spindle it's common to flip one over.
>
> If your spindle was truly set up with the 39 on the right, your left crank
> will be outboard more than necessary, as you noted. A shorter spindle, say
> a more common 3T or 3M with a 39 right would do it, just as Jeff Wills
> suggested.
>
> Write back with your crank model and we'll advise on the recommended
> spindle - yours does not seem original. The most likley is a 3-S, 122.5mm
> with 37.5 right.
> --
> Andrew Muzi
It was 39 right and 42 left. As I indicated, the crank is a Deore LX Triple
(175mm) circa 1990, so I guess the 68/122.5 is the way to go. If as you say
that BB has 37.5 right, that will bring the chainline in 1.5 mm, which
should be ok. If the original BB was133 total with 39 on the right, that
means that there was 94 for the rest of the spindle. With the new 122.5, if
we subtract the 37.5 right, we get 85 for the rest of the spindle. Unless
I'm mistaken, that means that the left crank will be moved in 9mm. I hope
that whoever put that 133 spindle in did it because they didn't have the
right part, and not because the left crank was hitting when the proper BB
was installed? Pity I didn't take my calipers to the bike before I took
apart the BB. Maybe I should put the BB back together and measure the
clearances before ordering the 122.5mm cartridge?