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  1. #1

    Join Date
    Jul 2011
    Posts
    14

    Default Bolt on hardtail rear wheel offset and tire size

    I'm helping out a friend with a 1969 T120/1971 frame with a bolt on hardtail.

    Triumphs are not my area of expertise. I'm welding on tabs and other general fab work for them. Lots of work to do, but my question is about the rear wheel and offset. At some point, somebody laced a 16x4" rim to the OEM hub and installed a 5" wide tire. In the current setup, the tire sits offset to the right about 1/2" with about a 1/4" inch chain clearance.

    Anyone have suggestions on a 16" rim and tire setup that would work better? I'm looking at 16x4, even 16x3.5 wide tires and not finding much. I'm thinking the rim would have to be a 2.15" if I were to go with something narrower, with a laced offset to center the tire?

    Tire makes and rim suggestions would be greatly appreciated.

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  2. #2

    Join Date
    Dec 2017
    Posts
    2,726

    Default

    still lots of room there. a 5.00 x 16" tire on a 3" wide rim can fit with spacer work and offset of the rim. to gain a bit more clearance, the rear sprocket can be offset from the hub, then offset rim from the hub. some said the engine can be offset up to 1/4" to the left - I never had to do that.
    For a narrower tire, go to 18" - you can get a 4.50 x 18 tire.

  3. #3

    Join Date
    Jul 2011
    Posts
    14

    Default

    Quote Originally Posted by TriNortchopz View Post
    still lots of room there. a 5.00 x 16" tire on a 3" wide rim can fit with spacer work and offset of the rim. to gain a bit more clearance, the rear sprocket can be offset from the hub, then offset rim from the hub. some said the engine can be offset up to 1/4" to the left - I never had to do that.
    For a narrower tire, go to 18" - you can get a 4.50 x 18 tire.
    That adds a lot of clarity, thank you! I think the preference will be to stick with a 16" wheel. My one concern is the brake cover to frame clearance. It's about a 1/4" at the moment. Also if I move my hub over won't the chain be out of alignment? The picture might show this better. I suppose one option is to kick out the left side frame legs and shift the motor over a tad.

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  4. #4

    Join Date
    Dec 2017
    Posts
    2,726

    Default

    My one concern is the brake cover to frame clearance. It's about a 1/4" at the moment.

    https://www.triumphrat.net/threads/1...l-t120.211166/

  5. #5

    Join Date
    Dec 2017
    Posts
    2,726

    Default

    2013 Thread: Trying to put a 5.5 rearwheel on a triumph

    http://www.chopcult.com/forum/showthread.php?t=28638


    Triumph Bobber hardtail alighnment problem

    "...Here is my problem, when I run a center line down the backbone and over the tire my wheel is off center a 1/4" to the right. However the chain is perfectly lined up with the drive sprocket (checked with straight edge and fancy smancy laser guide)..."

    "You may be as close to center-line as your are going to be assuming the straight-edge & laser were dead on. Sounds like your wheel offset is good, as well. You don't want to run your chain too close to the tire as you will have some side to side movement in the chain when decelarating, etc. and obvious tire slapping negates alot of cool on a bike. You may have already done this forty times by now, but I would have to recheck the sprocket alignment. Its difficult, depending on the stage of your engine build, to get a straight edge on the front sprocket but I, personally, trust it more than the laser as it leaves something for interpretation. With a straight edge, either it is or it isn't. Any you can squeek out of this area will help.

    This is just one of the problems associated with running a wider tire with a power-plant with limited final drive off-set...you run out of real estate to work with. A Triumph engine does not look right off-set in a frame (undesirable real estate). The sprocket center-line (3.125" from frame centerline) is your starting reference, so building left to right, mathematically, there is only so much you can do with the variables that you have and apparently, yours does not add up to be a centered tire. Some run a 520 chain and machine the sprocket to offset the chain away from the tire, allowing the rim to be shifted back toward the sprockets (.100") but having to machine sprockets (harder than the hubs of he11) is a PITA every time you change your chain and sprockets (expensive real estate). Therefore, after you have milked everything you can to move the wheel left (without compromising anything), then you have to rely on "optical illusions" through fender selection and placement, etc. If the fender is offset in the frame .125" and the wheel offset .125" in the fender, its less noticable than having the fender perfectly centered with the wheel and the fender & wheel offset .250 in the frame..."

    "the end all of alignment how-to posts:"
    TECH: Triumph Hardtail Alignment
    http://www.jockeyjournal.com/forum/s...ead.php?t=3984

    https://www.britbike.com/forums/ubbt...t&Number=88067

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