Gravity Bike Rack

[Elfin]

My assumption is that the weight limit is pending tow mode or some other structural approval... it does seem bizarrely low.

It's only 10lbs less than the Model X (which uses the same stupid hitch manufacturer)

There is no car where the bike rack capacity is the same as the tongue weight limit. Some manufacturers just don't get involved and list the tongue weight limit and leave it at that. There is a standard for measuring the tongue weight limit and they follow that, but there is no standard for measuring rack weight limits so you rarely see them mention it.

But, there is no cheating physics. The leverage of a bike rack makes it far less likely that you can use the tongue weight limit as a guide. Lucid is making this explicit as do some other manufacturers. The physics isn't unique to Lucid, they did not skimp on design, they're just honest about something that other players in the industry don't bother with. Here's an article from a rack distributor.

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Tongue weight on real trucks and SUVs is limited by the weight on the rear axle so the derating is the relative distance from the rear axle.

Note that the Model Y has a 160lb max bike rack rating while the Model X is only 120lb. Why is that? The Model Y doesn't add a pointless weak spot it the system.

 

[jered]

It's only 10lbs less than the Model X (which uses the same stupid hitch manufacturer)

Ahh -- thanks. I thought the difference was larger from comments I had been seeing here (and didn't go back to check the spec). I have the OEM Tesla (i.e. Yakima FullTilt 4) rack; I haven't put it on the Gravity yet but I assume it will be fine. It seems to me that the tongue-weight (and then rack lever limits) all relate back to the hitch class -- while I assume you could make a hitch with a higher tongue weight class but lower tow class, nobody seems to do so...

 

[Elfin]

It seems to me that the tongue-weight (and then rack lever limits) all relate back to the hitch class -- while I assume you could make a hitch with a higher tongue weight class but lower tow class, nobody seems to do so...

If you're going to design the rear suspension of the vehicle to handle a higher tongue weight you might as well spec it to tow the standard 10x the tongue weight.
I think the rack weight limit relative to the tongue weight limit is very dependent on the design of the receiver. For example I would be very comfortable driving with a bike rack weighing close to the maximum tongue weight on an F-150. The frame bends before the hitch breaks!

 

[flarbear]

If you're going to design the rear suspension of the vehicle to handle a higher tongue weight you might as well spec it to tow the standard 10x the tongue weight.

Absolutely not. The tongue weight is not the determiner of how much you can tow. Making a stronger hitch doesn't mean you can tow more.

 

[Elfin]

Absolutely not. The tongue weight is not the determiner of how much you can tow. Making a stronger hitch doesn't mean you can tow more.

I was trying to say if you make the compromises necessary to handle the tongue weight you might as well design it to handle the corresponding tow weight.
The hitch receiver itself really should never be the limiting factor.

 

[flarbear]

I was trying to say if you make the compromises necessary to handle the tongue weight you might as well design it to handle the corresponding tow weight.
The hitch receiver itself really should never be the limiting factor.

Tow weight is determined by a number of factors of which the hitch is only one. A 1000lb car cannot tow a 10,000lb trailer no matter how beefy the hitch is designed. A big truck with skimpy little wheels and a basic suspention cannot tow much no matter how strong its frame or how beefy the tow hitch you attach directly to that frame.

The amount you can tow goes far beyond the structure of the back end. Structure is one of its limits, but not the only one.

If you can't tow more than 6000lbs then you only need a hitch that can carry 600lbs vertical weight. You can design it for more than that, but it won't increase your towing capacity if other factors are already limiting it. It's more likely that they figure out how much the entire vehicle can handle swinging from a ball joint and then aim for 10% hitch weight.

Once you know those figures, you can design a hitch that could completely out-perform the 10% figure, or you can design one that just meets it and no further.

If you design one that just meets the 10% of your towing capability then you won't be able to carry a rack of equal weight because it is not supported on the outboard end.

But, you can't just advertise more towing weight because you built a really beefy hitch. It doesn't work that way.

Many of these EVs trying to get a really long range are designed to take a hitch that can stow completely out of the way because the aerodynamics of the design of the back end play a big role in efficiency and range. They either use these retractable or removable hitches or they advertise a much lower range. Granted, they could advertise a lower range only if you equip the tow package, but that would still cause issues especially because many owners want the hitch for only a small percentage of their trips and they don't want to pay the range price for every trip.

 

[Elfin]

Tow weight is determined by a number of factors of which the hitch is only one. A 1000lb car cannot tow a 10,000lb trailer no matter how beefy the hitch is designed. A big truck with skimpy little wheels and a basic suspention cannot tow much no matter how strong its frame or how beefy the tow hitch you attach directly to that frame.

The amount you can tow goes far beyond the structure of the back end. Structure is one of its limits, but not the only one.

If you can't tow more than 6000lbs then you only need a hitch that can carry 600lbs vertical weight. You can design it for more than that, but it won't increase your towing capacity if other factors are already limiting it. It's more likely that they figure out how much the entire vehicle can handle swinging from a ball joint and then aim for 10% hitch weight.

Once you know those figures, you can design a hitch that could completely out-perform the 10% figure, or you can design one that just meets it and no further.

If you design one that just meets the 10% of your towing capability then you won't be able to carry a rack of equal weight because it is not supported on the outboard end.

But, you can't just advertise more towing weight because you built a really beefy hitch. It doesn't work that way.

Many of these EVs trying to get a really long range are designed to take a hitch that can stow completely out of the way because the aerodynamics of the design of the back end play a big role in efficiency and range. They either use these retractable or removable hitches or they advertise a much lower range. Granted, they could advertise a lower range only if you equip the tow package, but that would still cause issues especially because many owners want the hitch for only a small percentage of their trips and they don't want to pay the range price for every trip.

A 1000lb car would have the front wheels in the air with a 1000lb tongue weight. I keep saying that structure is the least limiting factor in tow capability. Watch the video of the F-150 being dropped a couple feet onto the tow hitch. If someone crashes their F-150 because they exceeded the tow rating it's not going to be because the receiver failed.

I doubt that a design like this makes any difference to range. I am sure the reason Lucid chose to use a detachable hitch is aesthetics.

 

[cerb1958]

Page 114: https://lucidmotors.com/media/document/Lucid-Gravity-Owners-Manual_en-US.pdf
Weight limit is 110lbs.

Ignore all the other answers - this is the correct answer. It is a very low weight - inadequate really for racks and bikes and cargo boxes. I hope Lucid can address this in the future. My Porsche Macan has a vertical load weight of 441pounds - literally 4 times as much!!

 

[flarbear]

Ignore all the other answers - this is the correct answer. It is a very low weight - inadequate really for racks and bikes and cargo boxes. I hope Lucid can address this in the future. My Porsche Macan has a vertical load weight of 441pounds - literally 4 times as much!!

The Macan has a tongue weight of 441 lbs which is only applicable to a trailer as mentioned in the definitions in the owners manual (link). The technical data page only lists the tongue weight of 441 lbs and not the "load-carrying capacity" which is the figure they define as applying to bike racks in the owners manual page linked above.

 

[Nunya]

Makes me wonder for my 150 pound e-bike/rack. Should I just resign to get a small flatbed trailer? Or wait for a 3rd party to come up with a better hitch? I'd guess non-OEM options should come out.?.?

 

[Elfin]

The Macan has a tongue weight of 441 lbs which is only applicable to a trailer as mentioned in the definitions in the owners manual (link). The technical data page only lists the tongue weight of 441 lbs and not the "load-carrying capacity" which is the figure they define as applying to bike racks in the owners manual page linked above.

Yeah, not sure why they don't say what the load-carrying capacity actually is...
Anyway, they do sell a hitch bike rack ($1238!) that has a capacity of 65lbs x 2 and a weight of 39lbs. So I guess "load-carrying capacity" is at least 169lbs.

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[cerb1958]

Tow weight is determined by a number of factors of which the hitch is only one. A 1000lb car cannot tow a 10,000lb trailer no matter how beefy the hitch is designed. A big truck with skimpy little wheels and a basic suspention cannot tow much no matter how strong its frame or how beefy the tow hitch you attach directly to that frame.

The amount you can tow goes far beyond the structure of the back end. Structure is one of its limits, but not the only one.

If you can't tow more than 6000lbs then you only need a hitch that can carry 600lbs vertical weight. You can design it for more than that, but it won't increase your towing capacity if other factors are already limiting it. It's more likely that they figure out how much the entire vehicle can handle swinging from a ball joint and then aim for 10% hitch weight.

Once you know those figures, you can design a hitch that could completely out-perform the 10% figure, or you can design one that just meets it and no further.

If you design one that just meets the 10% of your towing capability then you won't be able to carry a rack of equal weight because it is not supported on the outboard end.

But, you can't just advertise more towing weight because you built a really beefy hitch. It doesn't work that way.

Many of these EVs trying to get a really long range are designed to take a hitch that can stow completely out of the way because the aerodynamics of the design of the back end play a big role in efficiency and range. They either use these retractable or removable hitches or they advertise a much lower range. Granted, they could advertise a lower range only if you equip the tow package, but that would still cause issues especially because many owners want the hitch for only a small percentage of their trips and they don't want to pay the range price for every trip.

well said!

 

[Bdr100]

Ignore all the other answers - this is the correct answer. It is a very low weight - inadequate really for racks and bikes and cargo boxes. I hope Lucid can address this in the future. My Porsche Macan has a vertical load weight of 441pounds - literally 4 times as much!!

To say that hitch is inadequate is not totally correct. I have a Thule Apex 4 rack - 35lbs, Road Bike -17 lbs, My Mountain Bike - 26 lbs, Wife Mountain Bike - 29 lbs. Total - 107 lbs. No, it will not handle multiple e-bikes, A family of 4 bikes, or a big cargo carrier, but it definitely meets my needs (your experience may differ.)

Also, with regards to the picture of Porsche with through bumper hitch, I remember a year ago looking at the new Cayenne and when googling hitch info, I was directed to European model info that showed that in Europe, Cayenne’s come with a similar hitch to the Gravity one, so probably with similar limitations.

 

[flarbear]

I feel like the standard practice of the industry is to...

Figure out how much wibbly wobbly swingy swongy trailer it can pull without losing stability given the vehicle's tire loads, traction and handling characteristics. (Porsche even listed different figures for depending on whether the trailer had active brakes or not for instance.)

Attach a hitch that can carry at least 10% of that trailer weight at the position of the ball hitch.

They're done.

Untrailered weight like a bike rack or accessory shelf will put far more vertical stress on that same hitch than a trailer coupler, so...

Most hitches can actually carry far more than 10% of the trailer rating, but since they only really need to advertise the 10% that's all they list in the literature.

If they can carry so much that even the additional leverage of a bike/accessory rack would not exceed its structural integrity, they don't bother listing anything more.

But, if the hitch actually has a real world limit that doesn't exceed the necessary towing tongue weight by enough margin of error, which is likely more true for these modern fancy detachable or retracting hitches, then they will estimate how much stress a rack of a particular weight will add and list a figure to try to keep customers safe.

Caveats:

Even the confidence of "it probably won't matter" for a beefy hitch can be exceeded by a relatively light weight rack that has a long lever arm, but what's the chance of that?

If they list a rack weight, they had to make some assumptions about "how leveraged" a bike rack might get in order to compute the number they report. They could still be wrong because there is no universal bike rack geometry and multiple bikes can be loaded in different ways that vary the moment arm of the various weights. They are likely conservative in this estimate so I don't think I would worry about exceeding it, but it's probably also likely you can successfully carry over that limit if your rack is particularly tight (i.e. the moment arms are shorter than they expected) - but would you want to risk it?

The only real way to solve the issue would be to list the tongue weight and moment arm of the canonical ball position and then make the customer do the moment arm weight and balance calculations on their own with additional data from their rack manufacturer and weighing their bikes with accessories. (This is grade school math, measure then multiply some numbers and add them up.)

Technically a trailer could have more than 10% of its weight fall on the coupler, but I would guess that the trailer industry has regulations that prevent that, and the restriction they adhere to is measured at the coupler which is exactly on top of the ball hitch, so a simple "tongue weight" rating for the ball hitch is enough to satisfy the conditions. Bike rack manufacturers have likely not really been held to any standard like that AFAICT.

The Macan might be able to hold 1000lbs or more if they have a frame welded hitch so they don't bother, they only need to list 441 which is 10% of their towing rating and they leave it at that. It's odd that they specifically call out that the rack weight would be different in their glossary but then don't bother to list an actual number.

Lucid/Tesla/other luxury manufacturers with aesthetically disappearing hitches probably have hitch mechanisms geared towards their 10% trailer rating and so they report the lower rack numbers.

 

[cerb1958]

To say that hitch is inadequate is not totally correct. I have a Thule Apex 4 rack - 35lbs, Road Bike -17 lbs, My Mountain Bike - 26 lbs, Wife Mountain Bike - 29 lbs. Total - 107 lbs. No, it will not handle multiple e-bikes, A family of 4 bikes, or a big cargo carrier, but it definitely meets my needs (your experience may differ.)

Also, with regards to the picture of Porsche with through bumper hitch, I remember a year ago looking at the new Cayenne and when googling hitch info, I was directed to European model info that showed that in Europe, Cayenne’s come with a similar hitch to the Gravity one, so probably with similar limitations.

MANY e-bikes weigh more than two of your bikes combined!! The average e-bike is 50- 70 pounds. So one e-bike may be all it can take unless super light e-bike

 

[Elfin]

MANY e-bikes weigh more than two of your bikes combined!! The average e-bike is 50- 70 pounds. So one e-bike may be all it can take unless super light e-bike

If you're poor. Gravity owners should only ride S-works!
Though if you're only taking two people you might as well put the bikes inside...

 

[Bdr100]

MANY e-bikes weigh more than two of your bikes combined!! The average e-bike is 50- 70 pounds. So one e-bike may be all it can take unless super light e-bike

Agreed. My post stated that it would probably not work for multiple e-bikes. But being as all my bikes are light weight carbon fiber bikes, it works for me. I actually rarely use it as I prefer to load bikes into back of SUV. But I do remember a family trip about 20 years ago with 2 light bikes, 2 heavy kids bikes on heavy rack and a sea kayak loaded on roof of our Lincoln Navigator. But those days are behind me. If we need to do a big family trip, my son has an Expedition Max that can carry half the house if needed.

 

[Elfin]

You could take off the batteries and put them inside the car.
I would never put fancy bikes on one of those hanger bike racks where they swing around and scratch up the frame. Just looked up the weight of my 1UP rack and it's 47lbs in 2 bike configuration and 86lb with 4 bike capacity.

 

[Smorgasbord]

Just to add to some of the good information above is that the owner's manual states:

Ensure that the total load of the rear-mounted accessory does not exceed 119 lbs (54 kg), and that the total load's center of gravity does not extend beyond 24" (63 cm) from the hitch receiver's pinhole.

A little math gives a "torque equivalent" rating of 238 ft-lbs. For me, if my loaded bike rack's center of gravity is closer than 24" then I would personally feel confident with carrying more bicycle/rack weight as long as the torque equivalent isn't exceeded.

The manual says that in tow mode speed is limited to 90 MPH. I wonder if the actual safe rating can be increased for lower speeds, especially on smooth roads. For instance, people mountain biking often drive on rough roads near the destination.

 

[Smorgasbord]

Just measured my rack. On our current Model X, distance to center point between the 2 bikes is 21 inches. Given the rack itself has more than half its weight at the hitch bar, I feel confident with a 119 * 24 / 21 =136 lb capacity.

Not advice for others, though.