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Tire centered in frame??

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Well guys, I've got a bent frame... I'm not happy about it, but I'm 99% sure it's the case. The problem was always a known issue, but I underestimated the scale. My rear tire, a big, square edge drag slick, is 16mm out of alignment with the centre of the tail light. I have no real datum to work from, but I know I can't sneak the chain any closer to the frame, front sprocket is aligned with the rear sprocket, and I'm still 16mm off on the rear tire (offset right when staring at the back end). Seems to me that the tail has been shifted to the left by the damage. This is consistent with the dented tube. The rim is 5.5 inches from a 93 gsxr and I plan to run a 180, not the slick.

My my question is, how wide of a tire can you run while maintaining the tire on centre? Should I be able to centre this tire up? Or is everyone running a bit offset?

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all the datum i can gather by just using the information in your pics says your back wheel is over to the right.

you'll have to do some measuring from headstock to swingarm pivot to rear shock mounts to etc etc etc. same with the swingarm to get a feel if anything is bent.

or try centering the rear wheel without the spacers to see if it is just an out of line rear hoop.

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As above but the rear subframe does look out of whack as well.  Use the headstock and s/arm pivot faces to locate true centerline then remove tyre so you can check true wheel center to frame centerline and make a judgement of what's going to be possible. A 5.5" rim is usually a squeeze but may require a 520 chain. Otherwise its possible to 'tunnel' the frame to allow chain clearance. Is the slick a Mickey Thompson? - they are usually listed as 7" wide - probably why its offset!

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180mm is pretty much maximum width that you can squeeze in while keeping the wheel centered. (We are talking about GSX1100, right?). Beyond that frame modifications are needed.

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a wee trick that can help point your direction - - - get a spirit level up against all the disc's and see if you can get them all showing the same

if they do - it does "suggest" the key point of the frame isn't bent ( likelihood of it getting knocked over whilst maintaining a true vertical relationship is unlikely) 

then place the swing arm on a flat table - supported by blocks on the swing arm pivot bolt and rear wheel axle - if you can "feel" any rocking between the 4 points = its the arm thats twisted ( and it only needs to be 1 or 2mm wobble gap to make a difference) - ok if arm is good and above spirit level test is bad = frame 

then accurately measure from swing arm pivot bolt centre to the swing arm rear axle adjuster marks - both on the arm and on the corresponding axle bolt adjusters - again a mm or two can become a good 10mm at the front wheel

 

thing is - looking at yir picture - it does show its off, it does appear the top rails are twisted which can be giving you a false idea that key frame bits are twisted - maybe not

Edited by nlovien
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Don't think a bent frame is your issue.  If you have the stock front sprocket off set,  the builder has just lined the sprockets up on the back wheel and not bothered with centreing the  wheel.

Measure the distance from the centre line of a GSX1100 wheel to the sprocket, then do the same on the gsxr wheel.  Chances are there will be a 16mm difference, or near as. 

5.5 rear wheel in a GSX1100 always needs an off set front sprocket and chain tunnels in the frame to line everything up correctly.

Edited by dupersunc
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you can widen the frame rather easily .....without channeling  or bashing it with a bfh . I've done 4 already with great results .....currently running k5 6" wheel and swinger without any modifications to the  wheel spacers or sprocket hub . give me a shout and I will be happy to pass on the info .....or go to my project thread and get an idea .

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9 hours ago, dupersunc said:

5.5 rear wheel in a GSX1100 always needs an off set front sprocket and chain tunnels in the frame to line everything up correctly.

I have to disagree with chain tunnel part. On my GSX I have 5.5" GSX-R rear wheel, GSX sprocket carrier and 13mm offset front sprocket (530 chain). I would say the wheel is pretty much centered and only modification to the frame is slight clean-up of shifter pedal shaft weld. Although all the clearances are at minimum now. The chain almost touches the frame tubes and it will rub tire if it is at wider end of 180 size (like Michelin).

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Bing. Bang. Boom. Bent.

I put a laser on it and all the construction levels I own. I screwed around with the alignment for about an hour and, granted, a mm here, a mm there makes a big difference in the outcome, but the end result is always the same, the tail is out of alignment with the pivot bolt and headstock. The good news is that the headstock, backbone, and pivot bolt seem to be in line. The line hits the front tire in the centre too.

Frame is good from what I can tell, just need to repair the bent tube between the shock mount and the pivot. 

Seems the tube is 32mm od and measured 70 thou wall? Any special kind of material used on these frames?

In the meantime, any ideas on how to shove this frame back into square before making the repair? Heat? Hydraulics? Hammer? Pry bar? Right now I don't own a torch or portapower, but I'm always looking for an excuse to buy tools.

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That is exactly the way I am measuring up my frame modifications :tu ( albeit it i have a smaller laser spirit level )

Time consuming but it is nice to directly see the result.

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Brute force and ignorance usually works! A few mates, steel bars and scaffold tubes with beer rewards after, saves  buying / hiring tools for one off jobs.

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For closure, some pictures of the fixed frame. Thanks to no class for the info on how to replace the bent tube. Couldn't get the internal sleeves perfectly centered due to some slight misalignment causing binding, but overall happy with the result. I'll give the tube one last sanding and cleaning, then weld it out and fill the plugs.

 

 

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NotStock your frame repair is heading the right way but you need counter bracing welded in to stop it from pulling back over when being welded up, or you'll end up almost back where you started.

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It's gonna get a lot more crooked before it gets straight again. No class sent some instructions on making the frame wider at the pivot. Looked good and seemed straight forward so I'm doing it. 

I attached some pics of the tool? Fixture? I put together to cope the tube. Maybe someone else will want to give it a go. Fair warning, it's sketchy.

When all is in place I will square it up one last time and get to tacking. It will be straight when it's all burned in. I need to cut out the shock mounts and tail bracing to perfectly square the ass end up... so this thing is snowballing. Badly.

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Hahaha,  welcome to the OSS.... Where projects get out of hands.. Waaay to easy.;)

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Motor out. Built a motor lifting frame to practice tube notching. I've built one before to lift from the carb flange bolts on zed motors. No easy places to pick up the EFE motor so I had to build a two part cradle type thing. 

There is going to be a lot of motor installing and uninstalling to build the new motor mounts. This is the only way I know to make that a painless process. Besides, I like fabricating more than I like suffering and manhandling motors. This seemed like a good place to work smarter.

 

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I love that thing! I find myself using it a ton now that I have it. The air over hydraulic upgrade was completely unnecessary. It does look cool...

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Loving the engine cradle. That is a rely nice idea.

I may just have to steal that idea for myself.

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I cut out the bracing today. So much grinding. I chose to keep the front motor mounts, but it's a real pain in the arse. Hindsight, probably easier to cut them out and build new ones. Live and learn - fabrication is more fun than intricate grinding inside corners.

More cutting to go yet. Every time I look at the bike I feel like I'm just cutting it into pieces that fit nicely in the garbage.

At the end of the day, like the title says, the tire WILL be in the centre of the frame with tons of room for the chain. 

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3 hours ago, SiBag said:

Loving the engine cradle. That is a rely nice idea.

I may just have to steal that idea for myself.

If you want to build one, don't make the same mistake as me, move the lifting point back further. My next modification for this one will be a piece of tube running parallel to the back bone on top. That way I can use an engine leveler to tilt the motor. If I had placed the lifting point further back it would have been better. I took a guess and missed by a little bit.

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Well that was absolutely terrifying. Stress level is at 11 when twisting your frame up like a pretzel. I tried some really questionable setups with ratchet straps before resulting to the mess shown below. End of the day, it all worked out, just had to jam a floor jack in there...

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3/4" doesn't sound like much, but it was well worth the effort. 

 

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Big thanks, yet again, to No Class for the instructions. 

 

Edited by NotStock
Screwed up.
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That waa'nt so bad now was it ? You broke your cherry !  There's no stopping you now ! Muahahahaha

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You are going to need a new pivot shaft...., source one from a kwak zrx1200.... it will fit real nice

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That pivot bolt leads me to my next problem... I still have not 110% selected a swinger. I have a shortened early gsxr one that came with the bike. I decided I didn't like it. Then I got a teapot swinger that I decided was too heavy. I now have a cheap bandit swinger, but I'm not entirely sure if it is the one for me. I'm practicing aluminum welds daily to get to a point where I'm comfortable modifying an aluminum swinger.

All I know for sure is that I want to run dual shocks. Open to suggestions.

 

 

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