Roof bars that mount with only one bolt- Mtbr.com
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  1. #1
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    Roof bars that mount with only one bolt

    My wife has a BMW 328 sedan that is a few years old. It has rack fittings on top, under some flip up covers. Each cross bar has just one bolt on the end, to fasten it to the car. We have carried road bikes, minus the front wheels, on there. The total bike weight was about 30 pounds for two bikes, and with fork mount carriers they sit low in front. I was thinking of getting two upright mountain bike carriers, to hold two 30 pound trail bikes with front wheels left on. Not only will be the bikes be heavier, but the carriers themselves are somewhat heavier than the fork mount carriers we used with road bikes. Plus they will be sitting higher with the frontwheels on.

    i am a little concerned about the possibility of one of those smallish bolts failing, with probably close to 100 pounds of bikes and bike carriers up there. Both the Yakima and Thule websites say everything’s a go, they make no mention of the single bolt per end situation. They mention no weight restriction. My wife’s previous car, a Subaru Impreza, had a similar one bolt per corner setup.

    Anyone have a similar one bolt per bar end setup? If so, any issues? I don’t want to get these carriers if anyone can relate any type of rack failure with a one bolt setup.

  2. #2
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    got any pics of said setup? I'm not entirely sure what you're describing, so I'm having a hard time visualizing it.

    I've never had a car with that sort of roof rack. Currently, I have a Honda Fit and have Thule rack with feet and clips that grab the car inside the door jams. Also have a Subaru XV Crosstrek with factory rails, and "lowrider" towers that just have rubber coated metal straps that wrap around the rails.

    All of my towers have a single bolt that tightens them up. The bolts on the towers for my Honda pull the clips up, and press the feet of the towers down into the roof and the channels up there. The bolts on the towers for my wife's Crosstrek tighten the straps that wrap around the factory rails. In both types of towers, that single bolt also compresses a metal wedge into the underside of the crossbar to hold it in place.

    Then there's the roof rack setup on my teardrop camper that's more basic. The "towers" are just powder coated steel plates that bolt to the sides of the camper. They have a hole for round bars, and a single screw holds the round bars in place. It's not "structural" inasmuch as it just keeps the round bars from sliding sideways. The rack itself is plenty sturdy to hold a rooftop tent if I so desired. I've done a 3200mi trip with 2 mtb's (wheels on with 1upUSA carriers) and an awning bolted to the rack.

    Is this similar to the sort of setup you're describing? Or is your rack yet another beast? Either way, both Thule racks have been solid for quite some time. I did have to replace the towers on my wife's car recently, after somewhere around 17 years of service. The teardrop is still pretty new (and stored in a garage when not being used), so not as much of a long term durability assessment there.

  3. #3
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    There is one bolt on the end of each bar “foot” or “tower”. This one bolt, attaches the foot/tower directly into the fitting that is integrated into the roof of the car. These 4 bolts are the only thing holding the foot/tower to the roof of the car. No clips that hook around the door jamb, no roof rails, it is a sedan.

  4. #4
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    The one bolt per foot racks are no problem. Cars in the family with racks that mount like this include a couple BMW 3 series (E90 and an F30) and a Mazda3. I have put thousands of miles on the Mazda3 with a roof box or 2 wheels on bike trays.

    Strictly follow torque specifications and check torque periodically. BMW's torque for their own racks is something like 9Nm. They even supply a flex beam style T handle wrench with their roof rack kits. Overtorquing can damage threaded inserts.

  5. #5
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    You won't have a problem. My factory Mitsubishi rack has the same one-bolt-per-foot kind of system. I routinely put two, 32lb. bikes up there and drive 6 hours across the state.

    If you were to drive, at speed, into a solid barrier with your bikes attached, I'd seriously think the roof would peel open like a tin can before the bolts on the rack actually sheared.
    The cake is a lie.

  6. #6
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    Any of you guys' 1 bolt cross bar bolts rust?
    The factory ones on my Impreza are pretty rusted =(

  7. #7
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    There are a few factory Honda cross bars that are held on with one bolt, two bolts for the towers and one for the cross bars. I've never seen a roof rack fail except when taken through a car wash and even then its typically the roof that gets damaged. The only thing I worry about when transporting my bike on my roof is that I didn't properly secure my bike and that it'll fall off and damage another car.

  8. #8
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    Thanks for the replies, looks like I am good to go on a BMW E90. I’ll make sure I grease the fittings though, and use the BMW torque wrench.

  9. #9
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    Quote Originally Posted by JimmyAsheville View Post
    BMW torque wrench.
    Just remember the only German torque spec you need to know, goodntight

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