Duragrouch

In which direction, too low, or too high?

If my memory serves, I think my 50/34 hollowtech II style, 5 x 110 mm BCD, I think is 43.5 chainline and works perfect on my folder with generally road dimensions. HOWEVER, I have a 7 speed cassette on 130mm OLD. With more modern cassettes and 135mm, things may be a whole lot different.

cyccommute 

And never mind that the chain line is adjustable. With internal bearing bottom brackets, a shorter spindle can be used. With external bearing cranks, spacers can be moved around to change the chain line. I have a number or road bikes with mountain bike cranks that I’ve had to adjust the chainline so that the crank will work with a road derailer. In some cases, all of the spacers on the crank have to be put on the left side so that the derailer has enough reach.

For those who say I’m risking damage, I more than one bike with this arrangement that have close to a combined 20,000 miles on them without issues.

CrimsonEclipse

Many BMX cranksets are specifically designed for 1x.
So the outer surface is not flattened for the outer chainring. So that's not an option to buy yourself 5mm
So while a BMX crankset will work for a folder, which generally have BMX chainlines, it would be a stretch for a road bike and, although do-able, not ideal for an MTB

Duragrouch

I did that for my external bearing crank, and problems; My Dahon Speed has a large diameter seat tube, and combined with the thickness of the (clamped) derailleur adaptor, meant the front derailleur could not go far enough in for the inner ring. So I spaced the crank (via the right external bearing) out 4mm (IIRC), this reduced the left arm clamp length accordingly. I felt this was a reasonable amount, a small fraction of the total design clamp length. But since one of two of the clamp bolt centers laid outside of the supported area (in that empty 4mm), the crank came loose after about a week of riding. I tightened the bolts and they stayed for the next day, but when I got home, I addressed this; The derailleur cage has an inboard rolled lip to stiffen it, but this flange was larger and thicker material than on any other front derailleur I have seen, and I decided it was overkill. I didn't grind it all off, just about a cm long I think at the top/forward of the cage, where it interfered at the adaptor bracket. This allowed removal of the 4mm spacers. Worked, and, now that the chainline was as designed, I didn't drop the chain every time I shifted from the big ring to the small ring, while on the lowest cog. And the left crank arm has never again come loose while riding. Things work better when installed as designed.

I would not have had a clamp problem with a crank designed to accommodate 170mm BB shell, in my 168mm shell, but the chainline would have still caused shifting problems. Even a few mm's was enough to make things off.

grumpus

Loctite 660 retaining compound fills gaps in worn bearing seats, or go full redneck with JB Weld.

Duragrouch

Good to know! I would hope that the 660, like Locktite's thread adhesives, has a reasonably low temp that it softens under heat, to ease disassembly.

grumpus

They call it high strength, it needs 250°C to soften, so keep away from carbon frames (unless they use high temperature epoxy, I doubt they do).