Rear Frame Tube Inner Diameter

[D0wn5h1ft]

Does anyone know what the I.D. of the frame tubing on the rear where our fenders are bolted on? Gotta go buy some tube for plug welding and I only have a limited window to use my campus's TIG

[IanDMacDonald]

Hmm. I know there are a few different sizes OD on this frame. 1" & possibly 7/8". When I did my GS850 cafe and cut the back, I believe the ID was nothing more than a 1/16". I'm willing to bet the Yammy frame is not much different.

[CaptonZap]

Drill a small hole, 1/16 inch or whatever, the smallest bit you have, through one wall. Take a piece of wire and put it in the hole , touching the inside of the opposite wall with the end of the wire. Clamp a pair of vise grips onto the outer end of the wire, with the tip of the jaws against outer surface of the tube.
Remove the wire and vise grips, measure the length of the wire, subtract that measurement from the measured diameter of the tube, and you have one wall thckness. Double that, and subtract that number from the outside diameter, and you have the inside diameter plus or minus measurement errors.
Be aware that wall thickness on bends varies, so pick a straight section, and also be aware that if the tubing not seamless, you may by chance hit the weld seam on the inside, so some judicious probing of the wire after insertion will allow you to tell if you really have the smooth wall on the opposite inside wall to measure from.
I would also get tubing a bit smaller than the calculated diameter, just in case the tubes are not round. If the inner tube is a sloppy fit, it can be hit with a hammer to square it, which in effect makes the corners a bit larger that the original diameter, and will provide support for the outer tubes until you can weld them.

CZ

[D0wn5h1ft]

Hmm. I know there are a few different sizes OD on this frame. 1" & possibly 7/8". When I did my GS850 cafe and cut the back, I believe the ID was nothing more than a 1/16". I'm willing to bet the Yammy frame is not much different.

That thick??? Wow, no wonder our bikes weigh so much. I guess this deltabox frame FZR has me spoiled

[IanDMacDonald]

I'm not very knowledgable about metal except working with sheetmetal for projects, etc. But,is 1/16" ID thick when in-relation to how heavy our bikes are? If anything, I was surprised it was so thin, but I'm not an engineer, and bought a pre-fabbed roll cage for my Mustang

[D0wn5h1ft]

I'm not very knowledgable about metal except working with sheetmetal for projects, etc. But,is 1/16" ID thick when in-relation to how heavy our bikes are? If anything, I was surprised it was so thin, but I'm not an engineer, and bought a pre-fabbed roll cage for my Mustang

The the inner diameter 1/16" or was that the wall thickness?

[IanDMacDonald]

Ahh, me dummy brain. Yes indeed. I have no idea what the actual ID of the tube is. MY BAD broski

[SFerinTEXAS]

Keep in mind the ID there is not round like the OD. There is a weld ridge longways inside. Has to be taken into consideration.

[crazy steve]

Does anyone know what the I.D. of the frame tubing on the rear where our fenders are bolted on? Gotta go buy some tube for plug welding and I only have a limited window to use my campus's TIG

The nominal wall thickness there should be .070" but may be .090". These are the two thicknesses I've found in these frames. The 'main' parts of the frame (engine cradle, uprights at the swingarm) are .090" I know for sure, most of the rest is .070". But none of it is seamless tubing, all will have a ridge in it and trying to find a 'slip fit' tube that will go into this is pretty much a waste of time; it's pretty lumpy in there. BTDT....

I've had the best luck by cutting the joints at an angle, making the joint as long as possible. As an alternative, get some tubing about 1/8" smaller than the OD, then split it lengthwise with at least a 1/8" wide cut. Drive this into the existing tube with the 'split' lined up with the ridge, tack weld it, then drive your 'new' piece over it.

[D0wn5h1ft]

The nominal wall thickness there should be .070" but may be .090". These are the two thicknesses I've found in these frames. The 'main' parts of the frame (engine cradle, uprights at the swingarm) are .090" I know for sure, most of the rest is .070". But none of it is seamless tubing, all will have a ridge in it and trying to find a 'slip fit' tube that will go into this is pretty much a waste of time; it's pretty lumpy in there. BTDT....

I've had the best luck by cutting the joints at an angle, making the joint as long as possible. As an alternative, get some tubing about 1/8" smaller than the OD, then split it lengthwise with at least a 1/8" wide cut. Drive this into the existing tube with the 'split' lined up with the ridge, tack weld it, then drive your 'new' piece over it.

I might elect for the latter. Of course this wouldn't be as easy as I thought . Seemed like a pretty simple procedure.

My backup plan was to weld a sleeve onto the part I chopped off. Then drill holes through the open part of the sleeve, tap them, and link it up to the frame with a set screw on each sleeve. Any thoughts on this? It would also all me more time to tinker because I wouldn't have to have my whole bike in the shop, just the rear end I chop. PLUS, it would make for a nice and quick removable rear fender.

[crazy steve]

I can tell you from experience that trying to 'slip fit' sleeve any joint when altering a frame with seamed tubing is an exercise in futility. I went so far as to trying to machine my own sleeves for the best possible fit and by the time I got one that didn't have to be hammered in it still ended up too loose.

If you're going to try an external sleeve, don't use set screws; those will just crush the inner tube over time. But the basic idea is good; if you bolt through both tubes and weld a sleeve in the inner tube bolt holes so it won't crush, that will hold up and give a tight joint.

[D0wn5h1ft]

I can tell you from experience that trying to 'slip fit' sleeve any joint when altering a frame with seamed tubing is an exercise in futility. I went so far as to trying to machine my own sleeves for the best possible fit and by the time I got one that didn't have to be hammered in it still ended up too loose.

If you're going to try an external sleeve, don't use set screws; those will just crush the inner tube over time. But the basic idea is good; if you bolt through both tubes and weld a sleeve in the inner tube bolt holes so it won't crush, that will hold up and give a tight joint.

Sounds like we might have come up with a good place to start. 7/8" ID isn't a standard for DOM steel tubing so I'm going to have to get something close. My options for standard sizes are either a little too small or a little too big. Which one do you think I should go for:

1 OD x .065 wall x .870 ID
1 OD x .058 wall x .884 ID
1-1/8 OD x .120 wall x .885 ID
1-1/4 OD x .188 wall x .874 ID

Any thicker wall than these and it's going to look like crap. I do have access to a lathe, technically, but it's going to cost me a 12 pack of beer to get it done for me.

[TomB]

A little too big, then saw cut along the length of your insert, it can then be sprung into the frame tube and be a perfect fit.