Checking for a bent frame. Is there a way?

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  • So my NS Analog got stolen but by an amazing chance I managed to find it. Totally trashed...missing front wheel, smashed in back and generally battered. Bars bent and you can guess the rest. Kids had been chucking it around the pavement.

    Anyway the frame and forks seemed to have managed to survive with only minor scratching which is a surprise due to the severe damage to the components...components what where left. Quite a bit had been stripped off. It appears that the remaining parts somehow managed to protect the frame.

    Anyway I would like to rebuild the bike as I love the frame and I can't seem to pick one up cheap enough or near by so its the only way.

    My question there any way I can check to see if the frame and forks are bent. Obviously I'm going to strip the paint so I will be able to see if the welds, etc., are okay but I can't really check if its bent. Doesn't look bent to the naked eye but it did take a beating and I want to be sure before I set to work rebuilding it.

    Its a tough old beast but I guess there's a chance its bent.

    Any advice would be dually welcome.

    Thanks in advance.

  • Put wheels in, check even spacing?

  • Most shops will have a frame alignment tool

  • I use a pretty crude but perfectly effective method of checking alignment when building which is to hold a broomstick (anything long and straight will work really) against the seat and headtubes such that it extends down to the rea dropouts and measure the distance to the dropout, switch to the other side and repeat.

    Also can use a digital angle finder to check head and seat tubes are in alignment. There's a not very accurate one on the iphone or you can get slightly better ones from ebay for buttons.

  • You can also use a piece of string.

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  • As suggested above most shops will have the right kit to be able to tell you. However like the picture above shows you can do it with string too.

    Loop string around the headtube through both of the rear dropouts and back to the headtube, and tie it nice and tight. You want to look at the distance between the ST outer edge and the string on both sides, use a ruler/vernier to be sure. You want them to be the same on both sides to know everything is still straight.

    If it isn't then it's either the front or rear triangle that will be out (or both possibly). LBS will have rear dropout realignment tools that allow you to see how parallel the drops are and can be used to bend them back into place and in conjunction with a frame alignment tool to get everything where it should be.

    Also look at how the wheels are sitting in the drops and if the brakes and rims/discs are still lined up. Check the forks for any damage to the steerer too incase it has been crashed head on.

    Good luck, and i hope my explanation isn't too shabby.

  • No no its good advice and I will give it a go.

    Many thanks guys for all your advice...basic checks so far seem to be pretty positive.

  • This is excellent advice, or take it to a frame builder if you're really worried. Or if rides weirdly once you build it. Yank the fork out and have a very good look at the crown and above... see if the foot/front wheel clearance looks about as you remember it.

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Checking for a bent frame. Is there a way?

Posted by Avatar for dragonflyblu @dragonflyblu