Results 1 to 10 of 10
  1. #1
    Scalpel Fan
    Reputation:
    Join Date
    Mar 2008
    Posts
    298

    Bike tray with the most lateral rigidity?

    Background: I have a 2015 Scion FR-S. The car has symmetric dual tow hook attachment points on the rear bumper. Following the idea of a few riders on FT86club, I designed bars that would thread into these tow hook attachment points and provide a platform to mount a bike tray. Already having a Thule Big Mouth from my previous 2007 GTI's roof rack setup, I turned recesses into the bar to fit the Big Mouth mounting points.

    Bike tray with the most lateral rigidity?-imageuploadedbytapatalk1437837897.616586.jpg

    After my first test fit, it was clear that I put my recesses too far from the rear of the car and I was getting some deflection in the bars. I also left way more clearance than I needed. Easy fix, move the tray inward to reduce the moment arm. I still have clearance for the trunk to open depending on pedal position. Even at the closer position, though, the Big Mouth's design leaves a lot of side to side movement relative to the bike. Higher speeds result in a lot of movement because the bike is up in the airstream and the aerodynamic drag.

    Bike tray with the most lateral rigidity?-imageuploadedbytapatalk1437838099.519047.jpg

    Bike tray with the most lateral rigidity?-imageuploadedbytapatalk1437838116.679080.jpg

    My road bike actually does well in this setup, but the extra weight and frontal area of the Scalpel overwhelm the Big Mouth. The bars themselves are quite rigid. They don't deflect any appreciable amount at the new mounting point.

    So, what I'm looking for is a bike tray with very little side to side motion as mounted on a normal car. It would be something with a wide platform where it would normally attach to crossbars. I think fork mount would be best because it would get more of the bike out of the airstream and reduce the overall moment arm. I'd obviously have to use a Fork Up to get my lefty equipped bikes on.

    Otherwise, I'll likely just go with a SeaSucker since it really isn't that much more expensive than a quality tray. I don't like the complete and utter lack of security on the SeaSucker, though. It would be adequate for being able to toss the bike on the roof for a quick weekend trip or taking the bike with me to ride after work. I've not found a hitch mount that I like for the FR-S, either.


    Sent from Tandy 400

  2. #2
    mtbr member
    Reputation:
    Join Date
    Jan 2009
    Posts
    455
    Cool idea.

    Take a look at the 1upusa tray... one solid extrusion with lots of structure, so it should be plenty stiff.

    1UPUSA.com Roof Tray Black
    --------------

    [WTB} 1987 Cannondale SM800, 20", Pink with airbrushed graphics.

  3. #3
    Scalpel Fan
    Reputation:
    Join Date
    Mar 2008
    Posts
    298

    Bike tray with the most lateral rigidity?

    I like the 1up. I don't see that they make a fork mount, though. Any company with similar construction ethos that makes a fork mount?

    Wildcard: Ecohitch makes a completely hidden hitch for the FR-S/BRZ now. The receiver pops out of the bottom of the hitch when not in use. That would let me use the Thule 916XT rack that I already have. The only caveat is that the hitch has a 100lb tongue weight limit. The rack weighs 58lbs. The hitch surely weighs 50+ lbs. Feels sacrilege on a car that is supposed to be light weight first.


    Sent from my iPhone using Tapatalk

  4. #4
    mtbr member
    Reputation:
    Join Date
    Jan 2009
    Posts
    455
    Quote Originally Posted by Quentin View Post
    I like the 1up. I don't see that they make a fork mount, though. Any company with similar construction ethos that makes a fork mount?
    I don't know of any, but IMO, you don't get much with a fork mount except the hassle of taking off the wheel and storing it.

    Plenty of folks use 1 or 2 spot hitch racks on sporty cars without issue.

    Good luck with your quest.
    --------------

    [WTB} 1987 Cannondale SM800, 20", Pink with airbrushed graphics.

  5. #5
    skobiken
    Reputation:
    Join Date
    Jun 2009
    Posts
    133
    I've had great luck with Rockymounts Pitchforks mounted behind the car like your bigmouth. The only flex I see is from the bars.
    Those who can give up essential liberty to obtain a little temporary safety, deserve neither. - Ben Franklin

  6. #6
    Scalpel Fan
    Reputation:
    Join Date
    Mar 2008
    Posts
    298

    Bike tray with the most lateral rigidity?

    J_Westy - yea, I have to deal with the wheel, but getting it out of the airstream will help out.

    Bad Idea - The Rockymount Pitchfork is on Amazon Prime for $100. I ordered it to see how it all works out. My fear is that by fork mounting I'll have the one rear wheel way out on the passenger side. Worst case, I'll return it and look at the hitch or the 1up after that.


    Sent from Tandy 400

  7. #7
    mtbr member
    Reputation:
    Join Date
    Jan 2009
    Posts
    455
    Quote Originally Posted by Quentin View Post
    J_Westy - yea, I have to deal with the wheel, but getting it out of the airstream will help out.

    Sent from Tandy 400
    Maybe you could make some small angle brackets and mount something like this to one end of the 1up tray... you could probably use the same hole where the moving arm mounts:

    DriveShaft HM- bike racks, truck racks, car racks, thru-axle bike racks, thru-axle bike carriers, thru-axle bike mounts, thru-axle adapters

    Name:  rm1084-5.jpg
Views: 158
Size:  12.9 KB

    Bike tray with the most lateral rigidity?-1082-2.jpg


    This would give you the rigid 1up tray with the nice T-slot underneath for mounting to your tubes and also give some flexibility to try fork mount versus both wheels on. Not sure if you've used the Fork Up adapter before... but while it does what it's supposed to do... it's time consuming to swing your caliper, remove the wheel, bolt on the Fork-up and the reverse when you get to the trail... so I'll bet you a Coke, you like both wheels on better.
    --------------

    [WTB} 1987 Cannondale SM800, 20", Pink with airbrushed graphics.

  8. #8
    Scalpel Fan
    Reputation:
    Join Date
    Mar 2008
    Posts
    298

    Bike tray with the most lateral rigidity?

    Quote Originally Posted by J_Westy View Post
    Maybe you could make some small angle brackets and mount something like this to one end of the 1up tray... you could probably use the same hole where the moving arm mounts:

    DriveShaft HM- bike racks, truck racks, car racks, thru-axle bike racks, thru-axle bike carriers, thru-axle bike mounts, thru-axle adapters

    Name:  rm1084-5.jpg
Views: 158
Size:  12.9 KB

    Click image for larger version. 

Name:	1082-2.jpg 
Views:	39 
Size:	54.8 KB 
ID:	1004725


    This would give you the rigid 1up tray with the nice T-slot underneath for mounting to your tubes and also give some flexibility to try fork mount versus both wheels on. Not sure if you've used the Fork Up adapter before... but while it does what it's supposed to do... it's time consuming to swing your caliper, remove the wheel, bolt on the Fork-up and the reverse when you get to the trail... so I'll bet you a Coke, you like both wheels on better.
    Bike tray with the most lateral rigidity?-imageuploadedbytapatalk1439253307.926080.jpg

    Bike tray with the most lateral rigidity?-imageuploadedbytapatalk1439253431.071719.jpg

    Used it for 8 hrs this weekend. Did great. Fork up works but I'm not crazy about it because it just isn't very secure. It seems to add another element of flex to the system. I did go ahead and order the larger diameter bars to use the standard Rocky Mount hardware rather than my temp solution shown in the 2nd pic. I might yet get a 1up tray. I really should have just bought the EcoHitch in the first place. Haha


    Sent from Tandy 400

  9. #9
    mtbr member
    Reputation: bigflamingtaco's Avatar
    Join Date
    Oct 2013
    Posts
    235
    I think a problem that you will not see go away is the fact that tow eye hooks are not designed for significant vertical loading. I think I'd be ok with putting a 16lb road bike on that type of setup if I could set it within 3-4 inches of the mount, but anything beyond that I would have to presume to be a significant stress on the mounting point. All of the tow-eye mounts I've seen on cars have been light duty, not at all like the big ones that come on Jeeps and Hummers.

    I'd also run a strap from the seatpost to the trunk lid to reduce cyclical overloading as I hit bumps and dips in the road.

    I'd have to nope out with the mtb.
    I will suffer no butt-hurt fools!

  10. #10
    Scalpel Fan
    Reputation:
    Join Date
    Mar 2008
    Posts
    298
    I disagree that tow hooks are designed to be directional. You rarely get to choose where the towed vehicle is relative to the rescue vehicle, so a straight pull is often impossible. They have to be strong enough to pull the weight of the vehicle with some coefficient of friction (for high centering) and then some factor of safety on top of that. Fact is that these are cars that will find themselves in ditches with higher frequency than others, so I'd figure they accounted for that.

    I'd thought about fatigue but I don't think it will be an issue based on what I've seen in my rear view mirror. All of the motion appears to be in the bike to tray connection rather than the bar to car. The suspension compresses when I load the bars manually; the bars/mount aren't flexing.


    Sent from Tandy 400

Similar Threads

  1. DIY: Thule bike tray 2 to 4 extension for $30
    By dmar123 in forum Passion
    Replies: 3
    Last Post: 01-29-2014, 10:27 AM
  2. Replies: 1
    Last Post: 01-27-2014, 02:12 PM
  3. Lateral Rigidity
    By djap in forum General Discussion
    Replies: 12
    Last Post: 10-01-2013, 04:14 PM
  4. lateral rigidity on Nickel
    By AZinSC in forum Santa Cruz
    Replies: 15
    Last Post: 06-27-2013, 11:27 AM
  5. Bike tray for Yakima.
    By 1Troutbum in forum Car & Biker
    Replies: 8
    Last Post: 12-16-2011, 01:47 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

Can't find it? Just search our site!