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-   -   Vitus 992 Crankset question and BB sizing. Dura ace 7410? (https://www.bikeforums.net/classic-vintage/939336-vitus-992-crankset-question-bb-sizing-dura-ace-7410-a.html)

PapaGanoosh 03-21-14 11:07 AM

Vitus 992 Crankset question. Dura ace 7410?
 
I am looking to replace the BB on my vitus 992. It currently has a bb with a 111mm spindle length on it (was used as a single speed by previous owner), however I wanted to replace it with a Dura ace crank and BB along witha full DA group. The chainstay seems to already have a bit of chainring rub on it with a 111mm spindle length, and I have been speaking with Chombi for advice (he's been fantastic btw) and he has told me that 113mm is shortest for double cranks and suggested I reference sheldon's BB sizing chart.

Now, I came across a 7410 crankset "low profile" (what does that mean....) at a decent price and with some research noticed that the spindle length for the crank is 103mm, I am not too sure that this will work on my frame given the chainstay rub from the previous 111mm spindle. I checked Sheldon's chart and it does say that 103 is indeed the correct spindle length and it gives a 43.5mm chainline. Given the infamous flexibility of the 992 BB flex, should I be worried about chainring rub if I run the shorter 103mm spindle? I am just a bit confused as to how this all works out, do the 7410 cranks jut out more at the square taper area to help push the crankset further away?

Chombi 03-21-14 11:50 AM

I noted to "Papaganoosh" already that as far as I know, DA7400 doubles usually work with 113mm spindles (JIS tapers) as they had on my own Vitus Carbone, This mentioned "low profile" 7410 crank must be something different that does not require the same spindle legnth...but that short 103mm spec sure sounds more like "track" single speed to me..... So it would really help the OP if anyone here can shine any light on this "low profile" crankset from Shimano.

jiangshi 03-21-14 11:55 AM

103 for 7410

GrayJay 03-21-14 11:56 AM

More modern cranks (such as your 7410) moved the tapered portion of the crank further inboard relative to the arms and rings so that a shorter lighter, stiffer) spindle can be used without changing the position of the rings and arms. You need to use the spindle length that is appropriate for the crank, spindle length doesnt really correlate to the frame unless it has some unusual clearance problem.

Chombi 03-21-14 12:21 PM

Didn't know the 7410 was that new......I guess that kinda explains why its so different from the 7400....

miamijim 03-21-14 12:59 PM

The 7410 doesn't work well with anything other than the 7410 specific 103mm BB. Unfortunately Shimano didn't make any other crankset that uses a 103mm spindle so your stuck with sourcing the BB-7410....and they get pricey for low mileage units.

PapaGanoosh 03-21-14 01:48 PM

Alright. That answers my question. This forum never fails, with the wealth of knowledge. Thanks guys

jiangshi 03-21-14 05:06 PM

There are lots of 103 BB's available, just Google it.

Chombi 03-21-14 06:34 PM


Originally Posted by jiangshi (Post 16599586)
There are lots of 103 BB's available, just Google it.

I presume it also needs to be JIS tapered......

Gonzo Bob 03-22-14 02:20 AM

I currently have a 7410 crankset with 103mm BB in my Vitus 979. I would think that combo should work fine with your 992 unless you are running a 45 or 48 inner ring. The chainring rub is from running the single ring too far inboard. I bet it was 48 or bigger.


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