Mechanics Quick Question Thread [Ask Questions Here]

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Mechanics Quick Question Thread [Ask Questions Here]
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Posted: May 21, 2019 at 18:31 Quote
Why don’t fork manufacturers only produce 29 inch lowers? It would make things easier it seems for everyone. Is there much of a stiffness difference or something with a shorter clearance lower for 27.5?
Thanks for entertaining my thoughts haha

Posted: May 21, 2019 at 18:53 Quote
cyberoptixs wrote:
Anyone know the torque specs for a RT86 rotor?
4nm with the locking washers, 6nm with raw bolts

Posted: May 21, 2019 at 18:54 Quote
bike2850 wrote:
Why don’t fork manufacturers only produce 29 inch lowers? It would make things easier it seems for everyone. Is there much of a stiffness difference or something with a shorter clearance lower for 27.5?
Thanks for entertaining my thoughts haha
you can get a longer stroke fork for a given axle to crown measurement with shorter lowers

Posted: May 21, 2019 at 18:55 Quote
seraph wrote:
R-M-R wrote:
seraph wrote:


Yes but they probably won't have the internal width you're looking for.

That's the crux of it. It's the difference between "can" and "should". Cyclocross tires are half the width of mountain tires, so it shouldn't be a surprise that mountain rims should be twice as wide.

Now, I'm sure someone is going to point out that 'cross rims might have an internal width of 19 mm and plenty of people are using 21 mm rims with 2.4" tires. Again, it's "can" vs. "should".

I mean yeah, we used to run 19mm inner rims with tires up to 2.35" back in the day, but that was also largely before tubeless was a thing. I wouldn't run a tire bigger than 2.1" tubeless on a 19mm rim.

I appreciate all of your inputs. I guess I'll pass on the wheels. I don't want to run that narrow a tire. 2.25 is about as narrow as I will go.

Posted: May 21, 2019 at 19:52 Quote
bikeman191 wrote:
I dented my back rim and want to replace just the rim and rebuild the wheel. I want to make sure I get the right replacement rim. My current wheel is a Stans Flow S1 29-142-12xd and want to replace it with a Stans flow mk3 rim. The reason is I found a good deal on the rim, https://www.amazon.com/gp/huc/view.html?ie=UTF8&newItems=C66754510-5349-40e2-a7e3-96b35bbcc70b%2C1, and my friend rides these wheels and really likes em.

So my question is can I use the hub from my flow S1 wheel and this rim? what are some downsides of using a different rim and hub? What measurements do I need from the rim to ensure I get a rim which fits my hub? As you can tell I am far from a bike mkechanic but love to ride my bike down hills and appreciate any help yall can offer me.

There is really no downside to whatever hub and rim combo you want. That is not the problem, are you trying to reuse the spokes? (Not recommended) they are going to be damaged where you bent the rim. Wheel building requires quite a bit of knowledge. Buy whatever rim you want and get the specs to buy the spokes you need. You will need all the dimensions of the hub, erd of the new rim. Spokes need to be accurate to the mm in length. Too short and the nipple will break at the shoulder, too long and you may bottom out on the thread. Please read some wheel building books, to learn about tension, dishing and truing.

Posted: May 21, 2019 at 22:44 Quote
demo7jumper wrote:
riish wrote:
The BCD doesn’t affect how it fits in the frame, only what chainring you can mount to the cranks.
So do you have any idea why it hits the frame?

Got a photo of how you've installed it all?

Posted: May 22, 2019 at 2:36 Quote
demo7jumper wrote:
riish wrote:
The BCD doesn’t affect how it fits in the frame, only what chainring you can mount to the cranks.
So do you have any idea why it hits the frame?

94bcd is the chainring circle, 104mm is your bb shell width, they are unrelated.
The problem is that you don't have a descendant dh crankset.
It is too short because you have 68/73 crankset which have chain lines for 49mm or somewhere close to that.
The dh crankset will have a 57mm chainline which is much further out and wont hit the frame.

Posted: May 22, 2019 at 2:38 Quote
104 BB?
104 is a BCD

Posted: May 22, 2019 at 2:40 Quote
Yep, it is a PF bb.
104.5x41

Posted: May 22, 2019 at 2:42 Quote
Still uses an 83 width measurement

Posted: May 22, 2019 at 3:33 Quote
nojzilla wrote:
Still uses an 83 width measurement

BB’s are far from logically standardised...

Posted: May 22, 2019 at 5:58 Quote
potato wrote:
demo7jumper wrote:
riish wrote:
The BCD doesn’t affect how it fits in the frame, only what chainring you can mount to the cranks.
So do you have any idea why it hits the frame?

94bcd is the chainring circle, 104mm is your bb shell width, they are unrelated.
The problem is that you don't have a descendant dh crankset.
It is too short because you have 68/73 crankset which have chain lines for 49mm or somewhere close to that.
The dh crankset will have a 57mm chainline which is much further out and wont hit the frame.
But the problem is that the crankset is 83mm
It is the truvativ descendant dh crankset
Brought it over to the lbs and they don't know why it doesn't fit

Posted: May 22, 2019 at 8:13 Quote
demo7jumper wrote:
potato wrote:
demo7jumper wrote:

So do you have any idea why it hits the frame?

94bcd is the chainring circle, 104mm is your bb shell width, they are unrelated.
The problem is that you don't have a descendant dh crankset.
It is too short because you have 68/73 crankset which have chain lines for 49mm or somewhere close to that.
The dh crankset will have a 57mm chainline which is much further out and wont hit the frame.
But the problem is that the crankset is 83mm
It is the truvativ descendant dh crankset
Brought it over to the lbs and they don't know why it doesn't fit

How much does it come up short by? Is it so much that its not possible that you have an extra spacer in the BB.

Edit: nevermind I just read that the chainring also hits the frame. Idk what it could be.

Posted: May 22, 2019 at 9:44 Quote
riish wrote:
nojzilla wrote:
Still uses an 83 width measurement

BB’s are far from logically standardised...

Someone please tell this to Cannondale. "We invented BB30, but now we're making it even more complicated by introducing BB30A. None of your BB30 cranks will fit our frames anymore."

Posted: May 22, 2019 at 9:45 Quote
so I have a Hope 30mm thread in BB

I currently run A raceface turbine crank and would really like to get A carbon Sram Xo crank ( the red and white will look sick on my bike ) but I remember reading somewhere A BB30 crank won't fit , is this true and if yes why ? The spindle too short ?


GXP is uncommon here and I'd like to keep this BB


 
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