donhaller 

I have an older style reciever mount 4-bike carrier for my vehicle. It uses a clamshell design clamping system to hold the bikes in place with a larrge plate that is secured on top of the top tubes with a threaded knob. For my mountain bikes and other steel bikes I have never worried about clamping pressure on the tubes, and just cranked it down tight. How fragile are CF top tubes, and how much clamping can they take from a bike carrier?

Pico

Shouldn't a problem. I have had my CF Roubaix in rack many times.

But, if you leave the bike out in the sun it will melt.

biker7

Agree it likely won't crush a top tube provided you don't over tighten the clamp but personally, I would never use that kind of rack for a high end CF bike. Instead, I would look into a receiver type fork mount style rack. They are out there. This does require removing the front wheel and the rear wheel is restrained with a clamp to a channel, but for me, no clamping force will ever get applied to my carbon fiber frame for transporting or working on my bikes in a repair stand. I don't like scratches on my frames either.
Good Luck,
George

DesFlurane

biker7,
Front fork clamping is not recommended for CF, as per Thule website.

donhaller 

OK - Great I'm glad I posted this question. What types of carriers are best with a CF frame?

DrPete 

This doesn't make sense. Does that mean I shouldn't ride with a front wheel? I mean, the clamping force on the dropouts is the same... unless "front fork clamping" means something different to Thule...

I carry my CF bike on a Yakima Viper fork mount carrier all the time, and it hasn't caused any problems...

derath

+1

I carry my OCR comp with my Thule fork mount all of the time. It actually seems to have slightly less clamping pressure than the front wheel


Sounds fishy to me


-D

DrPete 

I dropped an e-mail to Yakima asking them the question, just in case...

If they say I shouldn't use a fork mount, I'll have to buy a new car for my bike.

biker7

Say what? Applying a fork clamp at the axle wheel interface to a CF fork is precisely how a CF fork is loaded when a bicycle is ridden. Fork clamping on the roof of vehicles with CF forks is done universally replete with much more wind buffeting including my thousands of trips with my CF forks at highway speeds.
As an engineer, unless there is a misunderstanding, putting a compressive load to a carbon fiber top tube is much more structurally taxing then applying retention to a CF fork where the wheel interface is as designed. I could prove it mathmatically but is obvious to anybody with a design background.
George

biker7

+1
In that order and no hurry either...lol.
George

CDP

This is a good question, I just picked up my GF's new Synapse (alum but CF fork) and clamped it to Thule w a fork mounted bracket. Lucky I have a sunroof, because within two minutes she says stop the car! She looked up and the bike was wallowing side to side, seems one side of the fork got loose! I had it super tight too so I'm kinda worried about this system.

Then I thought about how much force it took to shake it loose if I had it so tight(?)

FYI it was a Mini (car) and it's dealing with the horrendous potholes of NYC so the ride is NOT a smooth one.

biker7

Doesn't matter what the ride is or how many potholes you hit. If the fork mount is a good one and you connected it properly to the car and the bike, the roof will rip off the car before the fork mount will come loose. Also, it doesn't matter whether you have steel, Ti, CF, Al fork etc.
You guys that own fork racks out there...which is a lot of us....is it becoming now more clear how mythology came into being?...lol.
George

vpiuva

Go to your LBS and ask them for a CF seat-tube cutoff (Look, etc). Try to bend that little short piece, crush it, do anything to it with your hands. You won't worry so much about holding down your CF frame

Rutnick

a friend of mine has that exact type of rack and has been using it for his CF Trek MTB for YEARS. No problems. If you want another type of rack, Saris receiver rack:

https://www.saris.com/p-234-cycle-on-pro.aspx

That's the benchmark in my opinion. It's what I use. It's on the expensive side but well worth it in my opinion. Takes any bike with basically any type of tire. It takes about 15 seconds (if that) to get the bike on the rack and have it ready to go.

Rutnick

I like graphs. I believe you but how about some graph or something?

ALPhillips

isnt the seat tube much more robust than the frame?

aicabsolut

I've got a top tube clamp rack. The straps are rubbery, so it can hold tight and not be a stiff clamp. My car is not very aerodynamic. Having the bikes off the back hitch helps keep me from being blown all over the road as much. And I don't have to climb up to the roof. Did a couple 10 hour road trips with this rack. No problems with my frame. I do strap it down so the bike doesn't sway.

jonathanb715

Back in 1989 I had an original MR2 (very small 2 seater), and used a Thule fork mount rack that was one piece. One thing I hadn't thought of is that with a short roof line on the car, the back of the bike mount (where the rear wheel goes) would bounce up and down each time I hit a bump, winding up like a spring and creating tremendous force on the fork. The front cross bar was less than 18 inches from the back, which was way under Thule's recommendations for this type of bike rack (I found out later - stupid dealer gave me a bum steer). One night on the Hutchinson River Parkway, the strap holding the back wheel down became the only thing holding my bike to the rack - the fork had bent due to the bouncing of the back of the bike.

I don't know if the new MINI has a long enough roofline to avoid this (the rear wheel of the bike should be mounted as close to the back cross bar as possible to minimize this effect), but it could be what caused your problem.

JB

clutchy

would you post the answer when they reply?

DrPete 

Sure... The e-mail refers to the "Viper," which is the bike mount I use, pictured below. I can assure you it's not the car.



And the response, which came within 2 hours of sending it, BTW...

JayC

I have the Thule version of that rack and that style rack is awesome. I looked at the Yakima and the Saris but ended up getting the Thule because it was all I could find in stock.