BignTall

Hello Everybody, this is my first post.

I have just bought a new Merida Matts LX mountain bike. Full house LX components with a Manitou Splice fork. However, straight from the box I found it slightly difficult to ride no-hands.
So, yesterday I had a look at the alignment of the rear wheel. The rim is ~3mm offset to the left (non-drive side) chain stay. I took the wheel out and re-inserted it the wrong way round. Measured it again with the same result. From this I conclude that the dish of the wheel is fine, but that the frame (rear triangle or dropouts) is mis-aligned in some way.
How accurate should frame alignment be? On my road bike, it is 100% accurate and on my cheap commuter just about. I feel that 3 mm is too much. Am I being pedantic, or should I get a new frame?

AngelT

BUMP.

I was actually wondering the same....except for my road bike which is 3mm misaligned. Anyone know the acceptable limits to road/mountain bike frames? Thanks.

Grand Bois

It's a good question. I hope somebody has the answer.

AngelT

I asked Trek the question...and got the following response:

"Thanks for writing. A frame is considered to be out of alignment if it is off by more than 2mm. Aluminum due to its properties, is not a good metal cold set or bend. With each consecutive bend it becomes weaker.
Imagine bending a pop can back and forth with your hands, it eventually gets soo week it breaks. Aligning this frame is a not a good choice."

I guess my frame's busted either way.

Grand Bois

I check a frame by running a string from one dropout, around the head tube and back to the other dropout. I then use a digital caliper to measure the distance from the string to the seat tube on each side. A ruler would work just as well. Since I own nothing but real steel bikes, I can use a 2X4 to make any adjustments that are needed, making sure to end up with whatever rear spacing I want. I'm sure there are alignment fixtures that are more accurate, but I'm also sure sure that I can get the frame well within that 2mm tolerance.

BignTall

I went back to the LBS where I bought it from and the mechanic there told me that the problem was too small to bother about. Personally I think that they just don't want to go through the schlep of ordering a new frame. Here at the southern tip of Africa everything is far away and it can take some time to get a replacement.

CATZ

As I am building a bent, I've been thinking about the "alignment" issue. They have all of these "laser line" devices for construction, etc. (pretty cheap). Why wouldn't one of these be "the nuts" for doing alignment? (of course, a piece of string is cheaper)

The advantage would be that nothing would have to be anchored or measured around. ... Shoot the line and measure to or from it. ???

Nessism

The string method is the best and most accurate low budget way to check rear end alignment on a regular double diamond frame. LOTS of professional builders used this method "back in the day".

neil0502

Good info, as always, from Park Tool and his Majesty, Sheldon Brown:

https://www.parktool.com/repair_help/FAG2.shtml

https://www.sheldonbrown.com/frame-spacing.html

khackney

Make em replace it... and let you ride the bad frame till the new one comes in.