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Rear Hub Spacing and Flip Flop Hub Questions? (kind of long)(5 posts)

Rear Hub Spacing and Flip Flop Hub Questions? (kind of long)James_M
Apr 11, 2003 10:09 PM
My old Trek fixed/single speed project is basically done and actually came out pretty well but I have a couple of questions?

I am curious about the frame spacing as according to everything I have read it should have 126mm spacing (1985 6spd)but it measures 132.5. The frame does not appear to be bent, rides fine, and I inspected it for damage/cracks when I stripped the paint and everything looked good. Is this something that happens to steel frames over time? Is this something to worry about from a safety standpoint? Does the fact that I am using a 135mm (which fits almost effortlessly) affect the answer to either of the questions above?

The hub I am using is a 135mm free/fixed Surly with a Shimano freewheel and a soon to be installed Surly track cog (when it gets here). With these hubs do you get the same chainline no matter which way the wheel is installed? It appears that the freewheel sits closer to the frame than the cog will but without the cog I cannot verify that.
re: Rear Hub Spacing and Flip Flop Hub Questions? (kind of long)eddie m
Apr 12, 2003 5:07 AM
That frame has probably been re-spaced for an 8 or 9 sp wheel at sometime in the past. If it's a steel frame and is properly aligned, it's not a problem at all.
With a fixed/free hub, you should get the same chainline on both sides. If you don't, you can use spacers behind the freewheel or cog, or respace the hub with axel spacers and re-dish the wheel. The hard part is that you may need a new bottom bracket axel or BB spacers to get the right chainline. Another choice is to adjust the hub to get equal (and opposite)chainline error on both ides. I try to get the chainline correct to 1mm, but I've heard others refer to chainlines that are off by 3mm as "good." I'm not sure what the maximum acceptable error is, but spacers are available in increments of 0.5 mm, so I try to get that close.
Apr 13, 2003 7:41 AM
Is it the 1X1 mtb hub? I thought that was only free/free, or does one side have the stepped threads for a lockring now? The 1x1 hub itself is symmetrical, but there might be a slight difference in chainline between the Surly cog and Shimano freewheel. The fixed guru's reference is below:

Chainline for the Surly cog is about 5mm, 8mm for the Shimano freewheel. You can probably slip a few spacers under the cog do match up chainline a bit better.

I have several 80's Trek frames, spacing is all over the place, 120, 123, 126, 128. Doesn't seem to be a problem as long as hub OLD is within a few mm. The earlier ones are especially nice for fixed as they don't have the shifter brazeons.
Thanks To All, See Reply For Hub Details.James_M
Apr 13, 2003 1:50 PM
The hub is their new fixed/free model which has the lockring threads on one side. I managed to get the chainline to where it is about 1 mm off one way for the track cog, and 2 mm off the other way for the freewheel. The bike rides nice and the drivetrain is silent so I think I will live with the current setup. Thanks for the replies.
Suntour Ultra/NWN Freewheel?hdnoise
Apr 18, 2003 12:24 PM
How does one remove and replace cogs on these. Unwind like the old regina's? I see what looks like tabs in the two prong removal slots. I also see a larger two slotted threaded ring around the inner ring. I wonder if these two internal rings are applicable to the inner mechanism and independent of the cogs? Any help is appreciated. I know there were diagrams on the old boxes so a fax or email of same might answer all for me. Thx.