80s steel frame alignment, wheel alignment and dropout questions
Hi - in an earlier post on a different subject I mentioned a mid-80s Sannino frame and fork I bought. Very happy with the frame's general condition and working on getting it ready to build as soon as I get the headset and Italian bottom bracket.
Last night I spread the dropouts from 126 to 130mm. I used the bench vice method because it was just easiest for me to set it up that way. Before bending, I checked the rear spacing and frame alignment using the string method. The spacing was around 127 or so, and the alignment was a couple of mm off to the non-drive side, so I did most of the spreading from the drive side. Slowly and surely I got it out to 130 and the alignment appears to be within a mm - it's definitely aligned better than when I started, fwiw. I squared the dropouts to each other using a tool I made that works just like the commercial alignment tools. Watching the dropouts contact the axle nuts when I close the QR's, it really looks skookum. So, everything seemed good except.....
First question: is it OK to spread open the forged rear dropout that seems to have been bumped/squeezed closed a little, making it difficult to slide the axle in?
After spreading the rear spacing, when I tried to install the wheel, I couldn't get it into the right / drive side dropout. Measuring with the caliper, I could see it was about mm narrower than the other side. The non-drive dropout was just a smidge wider than 10 mm, the drive side a smidge less than 10mm. So just very carefully inserted a flat pry bar into the drop out and just very gently tweaked it open a little - and that worked - the wheel went in - still a little tight and not as easy as the non-drive side, but I could get it in and out with just a little effort.
I'd like to open it up another 1/2mm to make it like the other side, and would like to know if I should file it or try to spread it a little more. Of course I should have asked before working on it last night, but I was really gentle and it just didn't seem risky. At the pressure I was using, it would either work, or nothing would happen.
Second question: With horizontal dropouts with adjusting screws, how far back in the dropouts should I put the axle? Middle? toward the front? toward the back? As far back as possible? Right now, the way the screws were when I got it, it's approximately a little forward of the middle. I understand the purpose of the adjusting screws and used them to center the wheel in the chain stay junction. But I'm just wondering where they should set the axle within the dropout.
Third question: visually, when centered in the chain stay junction, the wheel is off center when looking at the brake bridge - leaning toward the non-drive/left side. It's hard for me to measure this, but I'm guessing around 3mm at the most. Can definitely see it. Probably just me, but I don't like it. The hole in the brake bridge is centered.
Like I said, I do believe the frame is aligned pretty well, the dropouts are aligned square to each other and the wheel sits centered at the chain stay junction.
To my mind, the bottom surface of the rear drive side dropout being too high (which relates to the fact that it's too narrow - bumped/bent closed from the bottom), could cause the wheel to tilt the opposite direction. I've been too far gone from trigonometry or geometry or whatever branch of math is needed, but I do know that a tiny change in the horizontal axle "tilt" could cause a much larger change in the wheel tilt along it's vertical radius.
Any suggestions? I have no idea if the slight misalignment of the wheel will be noticeable when riding, but I'd like to fix it if it's easy.
Last edited by Camilo; 04-18-2013 at 09:56 AM.
I'm not an expert, just a scientifically/mathematically minded guy.
As far as the wheel being 3mm off-center at the top, you only need concern yourself with the top surface of the axle slots in the dropouts.
And don't even worry about it until you build the bike and sit on the saddle because the axle will go against the tops and the stays may flex so the wheel may center itself.
If you still need to adjust it you don't need trig; you only have to figure out the ratio of the two dimensions: bottom leg is 130mm/2 versus measurement of axle to rim.
For a fast estimate; on a 700c rim the rough center of the tire sidewall is 13" from the axle, the bottom leg is about 2.5 inches so the ratio is close to 5 to 1. To move the tire 3mm to the right the left dropout top would have to be raised roughly .5mm, a tiny amount.
hope this helped
Thanks - in my mind I had figured it was a fairly large ratio being 1/2 the axle was about 2.5 inches and 1/2 the wheel (+tire) was about 13-14 inches.... so I'm glad my mind hasn't completely lost it's ability to think that way! I like your advice of getting it built up before doing any more bending, however I also like your advice that it is such a tiny amount to change the axle to get the 2-3 mm in centering on the top of the wheel.
Originally Posted by Randy99CL
It took me a minute to figure out why you were talking about the upper surface of the dropout rather than the lower .... then I remembered that that is where the axle makes weighted contact, duh!
I'm still interested in any insight to the other two questions....
I had a frame with a similarly "closed" rear dropout slot.
It stands to reason that the "free" end of the slot (the portion not secured to the seat stay or chainstay) is what is squeezed closed, so prying it open is an option. Be sure and have the adjustment screws in the dropouts as you pry the slot open otherwise the threaded hole may deform.
With horizontal dropouts, I try to vertically align the derailleur mounting bolt with the axle. I thought I once read a Shimano tech sheet that spec'd this orientation as desired for optimum shifting with Shimano derailleurs.
Regarding the wheel not being centered between the seatstays: I assume you've already confirmed the wheel is dished correctly. You can't assume the brake mounting hole is centered unless you measure from either hole edge to a reference point on the seatstay as the hole could very well be off-center itself.
Once that's confirmed, it's possible the frame was assembled with the dropouts skewed in a vertical plane. That would be tougher to prove out without a surface plate to fix the frame by the bottom bracket and run a right angled gauge up the dropout slots to see if it contacts the top edge of both slots. The only way left to fix it would be to file the top edge of the appropriate slot so the wheel starts to tilt in your desired directon.
The adjusting screws is to make sure the wheel is aligned in the dropouts with the screws in the middle position, once the wheel is aligned then you adjust the screws just enough so they stop against the hub. From then on whenever you replace the wheel you simply slide the wheel against the screws and voila the wheel is perfectly aligned each and every time.
Speaking of dishing, sometimes when you spread the dropouts you may have to redish the wheel to get the right fit. I never had to that, but all I did was go from 6 to 7 speed freewheel, so I had to have the rear wheel redished a little bit and a washer added.
I bought my first brand new bicycle when I was in my early 20s. I was in the Navy, stationed overseas, with no good english-speaking bike shop nearby.
Originally Posted by Peter P.
Had no choice but to buy the best Huffy 12-speed they had on base at the Navy Exchange. Cost me maybe 50 bucks (in the mid-'70s).
I had no problem assembling it myself but I just couldn't get the rear wheel centered between the seatstays, it was 1/2" off!
Huffy used stamped steel dropouts slid into tubes and the left side was 1/8" out from flush when it was welded. Absolutely Zero quality control.
I adjusted the axle crooked in the slots and tightened down the nuts but it still wasn't perfect. Gave the stupid bike away when I transferred back to the States, good riddance!
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