Are tube tops for bike racks safe?

Places

New Member
Region
USA
Just realizing if I buy the ebike I’ve been looking at, it won’t work on my existing bike rack for my car. It has two arms that you hang the top tube of a bike on like this. However since the ebike mtb has a slanted top tube, I’d need to use a rack accessory like a top tube. It seems like this makes the bike hang by the handlebars and the seat. That doesn’t seem safe since that’s not the frame of the body. Does anyone have experience with these? Should I buy a new bike rack? I have a tiny car unfortunately but I’m buying a new car this summer so reluctant to buy new racks too.
 

WattsUpDude

Well-Known Member
Just realizing if I buy the ebike I’ve been looking at, it won’t work on my existing bike rack for my car. It has two arms that you hang the top tube of a bike on. However since the ebike mtb has a slanted top tube, I’d need to use a rack accessory like a top tube. It seems like this makes the bike hang by the handlebars and the seat. That doesn’t seem safe since that’s not the frame of the body. Does anyone have experience with these? Should I buy a new bike rack? I have a tiny car unfortunately but I’m buying a new car this summer so reluctant to buy new racks too.

You can purchase a rack with bottom trays (for the wheels and tires to rest on) instead. They're not much more expensive.
 

Dallant

Well-Known Member
Just realizing if I buy the ebike I’ve been looking at, it won’t work on my existing bike rack for my car. It has two arms that you hang the top tube of a bike on. However since the ebike mtb has a slanted top tube, I’d need to use a rack accessory like a top tube. It seems like this makes the bike hang by the handlebars and the seat. That doesn’t seem safe since that’s not the frame of the body. Does anyone have experience with these? Should I buy a new bike rack? I have a tiny car unfortunately but I’m buying a new car this summer so reluctant to buy new racks too.
Depending on the top tube accessory, it should work for that. I’d look for a heavier duty one, of course.
 

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harryS

Well-Known Member
I didn't trust top tubes for my wife/daughter's 30 pound bikes, If the seat clamp lets go, bye bye bike. I used to tie the rear hook of the top tube to the frame. I sure would not use these for a 50-70 ebike.

I bought a platform rack a week after getting ebikes. Unfortunately, I did not do my research and later found my rack was only rated for two 35 pound bikes. If I pulled the battery/saddles, I had about 85 pounds. I was using the rack with a heavy SUV and felt it was OK.

Later, I went to a smaller car. I added a class 1 hitch, but now found that the weight of my rack plus two bikes exceeded the hitch rating. I added two rooftop straps to spread the load, and using my 50 years of engineering expertise, pronounced it safe. However, I eventually started carrying lighter ebikes.

The tongue weight limit will be your issue. I think you can stay within the weight guidlines with a class 1 hitch, a platform rack, and one ebike with battery/seat removed. For safety, probably should remove most batteries anyway. Just don't leave them on top of the car.
 

Sierratim

Well-Known Member
Region
USA
City
Nevada City, CA & Paradise Valley, AZ
We switched to a tray style hitch rack for the ebikes. They were just too heavy for my wife and I to even consider lifting onto our old top tube style rack. We do remove the batteries first, but still too much for us.

In looking at new racks the load capacity was something that became a consideration. The 2 ebikes together weight ~100lbs. Not all racks can handle this.
 

smorgasbord

Well-Known Member
Region
USA
Everybody confuses Tongue Weight with actual vertical weight capacity. I'm surprised there aren't more failures, but I guess these things are over-built.

Let me try an explanation. When you're towing a trailer the vertical weight is located at the ball, which is fairly close to the vehicle, like maybe 8" from the rear bumper. Now, look at a bike rack carrying 2 bikes (4 is even worse). The vertical force is located much further away from the bumper, maybe a couple feet or more. Even with the same weight, this is putting larger torque on the hitch. And considering that many hitches today aren't a single piece but have a removable hitch receiver, then that connection is taking not just the vertical weight, but the torque being applied.

I know the OEM hitches on Tesla vehicles have a vertical weight limit that's much less than the rated tongue weight. See this reddit thread for instance, in which a 350 lb tongue weight capacity has only a 160 lb vertical carrying capacity.

My own vehicle (Tesla Model X) has a 500 lb tongue weight spec but only a 120 lb vertical load capacity. The manual says:
The hitch receiver is designed to support vertical loads of up to 120 lbs (54 kg). When carrying bicycles or other items on the Model X hitch, always check to ensure that the maximum weight is not exceeded. When calculating weight, remember to include the weight of the accessory carrier. For example, assuming the carrier weighs 40 lbs, the weight threshold is sufficient for carrying two bicycles weighing approximately 40 lbs each, or four bicycles weighing approximately 20 lbs each.

That said, I've been carrying our two 60lb bikes on a 45 lb rack about a dozen times, including freeway driving up to 80MPH. While wind resistance is an issue, I suspect that a bumpy road at too high a speed is also a problem, maybe more serious. Our rack is a platform rack and the bikes are pretty close to the vehicle as well. I still worry about it every time I hit a bump though.
 

harryS

Well-Known Member
Everybody confuses Tongue Weight with actual vertical weight capacity. I'm surprised there aren't more failures, but I guess these things are over-built..
I didn't want to get into that, but thanks for doing so. Class 1 is 200 pounds where the trailer ball would hang, , but with a platform rack, that means around 100 pounds at the end.
 

Court

Administrator
Staff member
Hi @Places, I think @smorgasbord and @harryS really covered this well, but I wanted to ask if you have considered transporting the bike in your trunk? I would often remove my wheels (which had quick release) and stuff the frame into the trunk of my car in order to go mountain biking. I've had the trunk racks that hang off the rear of the car (just like you said you had) and they do tend to have lower weight limits, the bike can swing into the bumper if you stop fast, and the tires can hang down and get burned by the exhaust. I recently installed an 1-1/4" hitch on my 2005 Toyota Prius and use the lightweight aluminum Küat Sherpa rack. I always remove the battery pack and mount the bike on the slot closest to the car to reduce the leverage force. Since I'm frequently moving ebikes around (fat, folding, mountain, city with fenders etc.) I found the hitch rack to be safest and most versatile. With just one bike, I have never had a problem with this rack, but it is more expensive... The thing is, you will still have the rack once you get a new car, just might have to install another hitch receiver which can be ~$150 plus your time.

electric-mountain-bike-on-kuat-sherpa-2.jpg
 
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Dallant

Well-Known Member
I didn't trust top tubes for my wife/daughter's 30 pound bikes, If the seat clamp lets go, bye bye bike. I used to tie the rear hook of the top tube to the frame. I sure would not use these for a 50-70 ebike.

I bought a platform rack a week after getting ebikes. Unfortunately, I did not do my research and later found my rack was only rated for two 35 pound bikes. If I pulled the battery/saddles, I had about 85 pounds. I was using the rack with a heavy SUV and felt it was OK.
Have you ever seen a seat clamp let go?
While I’m not a fan of using this cross bar for hanging an ebike from, I have used one for use with a top-down hook-style rack but that isn’t supporting any of the ebike’s weight.
CA8E1F78-0312-4047-813B-41AECB526C45.jpeg
 

Court

Administrator
Staff member
@Dallant, I've used those crossbar adapters to haul ebikes before and never had an issue... I am extra careful about tightening the seat clamp, but if you look at the angle of the seat tube and how the crossbar adapter pulls on it, there is lateral force that creates friction and a wedge if the seat post did begin to slip. Since the length of the crossbar is fixed, I think it would actually be very difficult for the seat post to slide up and out because that would take the crossbar up, and the fixed length would create a lock and it would stop. Does this make sense to you? The more the seatpost slides up, the further the crossbar would extend out, which has a limit. One could argue that the crossbar would stay low while the seatpost slides up, but I feel that is unlikely because nothing would be pulling it up besides the crossbar adapter, which cannot go up do to its fixed length, nice picture by the way :)
 

harryS

Well-Known Member
Sure, some of my seat clamps let go all the time, and my seat slides to the bottom.

I definitely take a more pessimistic view of things than a lot of people. Many years ago, I was responsible for signing off on product safety issues for my company. My engineers did the real work, telling me what was good/bad, but the rule was to always assume the worst would happen.
 
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EMGX

Well-Known Member
I've used one of these top tube adapters for many years on my wife's bikes including a heavy steel frame cruiser and ebikes without ever having a problem. YMMV.
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Dallant

Well-Known Member
@Dallant, I've used those crossbar adapters to haul ebikes before and never had an issue... I am extra careful about tightening the seat clamp, but if you look at the angle of the seat tube and how the crossbar adapter pulls on it, there is lateral force that creates friction and a wedge if the seat post did begin to slip. Since the length of the crossbar is fixed, I think it would actually be very difficult for the seat post to slide up and out because that would take the crossbar up, and the fixed length would create a lock and it would stop. Does this make sense to you? The more the seatpost slides up, the further the crossbar would extend out, which has a limit. One could argue that the crossbar would stay low while the seatpost slides up, but I feel that is unlikely because nothing would be pulling it up besides the crossbar adapter, which cannot go up do to its fixed length, nice picture by the way :)
Well, SOME of these adapters are spring-loaded, of course, so the idea that the lateral force creates friction/wedge is dependent on the design. The one I showed in the photo above is just such a design which is why I added a small purple bungee cord to it. That adapter has a two-piece design actually only held together with a thin elastic string which is fine for what I use it for. I wouldn’t count on it to create much lateral force.
 

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StevenC56

Member
Region
USA
Hi @Places, I think @smorgasbord and @harryS really covered this well, but I wanted to ask if you have considered transporting the bike in your trunk? I would often remove my wheels (which had quick release) and stuff the frame into the trunk of my car in order to go mountain biking. I've had the trunk racks that hang off the rear of the car (just like you said you had) and they do tend to have lower weight limits, the bike can swing into the bumper if you stop fast, and the tires can hang down and get burned by the exhaust. I recently installed an 1-1/4" hitch on my 2005 Toyota Prius and use the lightweight aluminum Küat Sherpa rack. I always remove the battery pack and mount the bike on the slot closest to the car to reduce the leverage force. Since I'm frequently moving ebikes around (fat, folding, mountain, city with fenders etc.) I found the hitch rack to be safest and most versatile. With just one bike, I have never had a problem with this rack, but it is more expensive... The thing is, you will still have the rack once you get a new car, just might have to install another hitch receiver which can be ~$150 plus your time.

View attachment 78662
This is the exact same rack I have. If your bikes have carbon frames, you definitely don't want to use a rack that the bikes hang on the top tube, or one that has anything that hooks to the frame at all.
 

bob armani

Well-Known Member
Hi @Places, I think @smorgasbord and @harryS really covered this well, but I wanted to ask if you have considered transporting the bike in your trunk? I would often remove my wheels (which had quick release) and stuff the frame into the trunk of my car in order to go mountain biking. I've had the trunk racks that hang off the rear of the car (just like you said you had) and they do tend to have lower weight limits, the bike can swing into the bumper if you stop fast, and the tires can hang down and get burned by the exhaust. I recently installed an 1-1/4" hitch on my 2005 Toyota Prius and use the lightweight aluminum Küat Sherpa rack. I always remove the battery pack and mount the bike on the slot closest to the car to reduce the leverage force. Since I'm frequently moving ebikes around (fat, folding, mountain, city with fenders etc.) I found the hitch rack to be safest and most versatile. With just one bike, I have never had a problem with this rack, but it is more expensive... The thing is, you will still have the rack once you get a new car, just might have to install another hitch receiver which can be ~$150 plus your time.

View attachment 78662
Nice rig you've got there Court. I thought you had a Specialized Turbo Expert. Looks like BH EMTB if I am correct, Sweet!
The 1-1/4 hitch mount comes in handy for just about any of the great racks out there that fit that setup. I went ahead and took the challenge of mounting my own receiver to my Toyota Matrix. A bit of work with the pre-drilled (threaded) holes on the under-body, but it all went in tight and secure. I am still using my older SportRack that did not have tire hoops that fit plus sized tires, so I had to expand them a bit and now the 2.8mm wide tires fit like a glove.
1612837610456.png