mohairsam44

Hello!

I have a question to ask, regarding an issue i am having trouble with..


exactly how big of a problem is a chainline that is not straight? Because i can't seem to get mine perfectly straight, as i dont think i can use any smaller of a bottom bracket, and i certainly can't use a larger hub without having to literally bend out my frame..

I am of course aware that this will wear out the chainring super quick, but what other problems will it present?

Thank you!

vbwstripes

Chain derails = fall on your face in front of a car

1fluffhead

Have you measured it? How much is it off?

mohairsam44

understood, in that case, how might i align the chain? would it be too unorthdox to somehow bend the frame? If thats okay, than how best to do it?

2new2this

ummm

queerpunk

the chainline is determined by the HUB, not by the frame or by the spacing of the hub (unless you unevenly space the hub, which is not a done thing).

chainline is the measurement from the centerline of the hub to the center of the cog. changing how the frame holds the hub is not going to make a difference, except you can get the frame out of alignment.

measure from the center of your seatpost to the center of your chainring to determine how far off your chainline is. chances are your hub's chainline is 42.5mm. if you're within 2 or 3 millimeters of that at the chainring, you are fine.

mohairsam44

i see, what i mean is that my chain ring does NOT form a straight line with the cog on my rear wheel. This is my first attempt at assembling a bicycle so i realize what an ignorant idiot i am, i'm just still not quite sure how to solve this problem

trons

get a smaller (width) bottom bracket or respace hub/redish wheel
don't bend your frame

mohairsam44

how do you respace a track hub?

TheSodaJerk

Buy spacers and put them on I believe. Someone please confirm or correct me.

Viva.Viagra

You've already been asked / told / responded to several times

-How far off is it now?

-If your within 2-3 mm (~0.1"), that's probably sufficient.

I suggest you do some research at Sheldon Brown and other relevant sites. A better understanding of what you're trying to accomplish would be useful.

mohairsam44

i've already done research on Sheldon Brown, and i thought, though perhaps i was mistaken, that i was aware of what my problem was, i'm in the process of taking queerpunks advice, and will let you know how it turns out. Thank you all for your help

native75

Hey Mo -- To follow up on Sodajerks advice. You can respace the hub's placement by adding/removing the small bolts ("spacers") that extend from either side of the hub. Two cone wrenches and a handful of spacers in different sizes should get the job done. As you subtract spacers to move wheel right, you'll have to compensate by adding spacers on the left. And vice versa. -- n75

MrCjolsen

You can usually move your cog out 1mm by using a thin bottom bracket spacer. Also, you might need different cranks.

Is your chainring mounted on the inside or outside of your crank? Most converted road bikes will need their chainrings on the inboard side of the crank. It doesn't look as clean, but it's what most of us have to do.

Also, some chainrings have the teeth just a little off center. By flipping the chainring around, you move it in a millimeter or a fraction thereof.

Are you using what was formerly a triple crankset? On a triple, the middle ring will be further out than the inner ring on a double. Usually too far out. If that's the case, get a double crank and put it on.

I've found that 95% of the time, the inner ring on a road double lines up almost perfectly with the cog on a 120mm track hub.