Tell me about foam-core carbon rims

[teleguy57]

Been looking at new/used/build myself carbon tubular wheels, and I see that some rims are foam cored. What are the pros/cons of foam vs non-foam tubular rims?

[Tristan]

I wouldn't make your buying decision based on whether the rim is foam cored or not. It's a very similar comparison to eyelets - some eyeletted rims are good, others are crap. The simple fact that a rim has eyelets is neither positive nor negative - you need to look at the whole picture.

Having said all that I can't think of any modern high quality rim which uses a foam core?

[teleguy57]

Thanks, Tristan. Not looking to make that a buying criteria; just wondering about the technology itself. Good to know that it may be an older technology.

[Tristan]

I'm not a carbon manufacture expert but my understanding is that you need to support the carbon from inside the rim cavity while it gets cooked under high pressure. Most rims do this by using an inflated plastic bag inside the rim - anyone who has built a Zipp can tell you all about how much fun it is when the bag is left inside. On an Enve rim you can see the hole where they pulled the bag out from and patched up. The foam core does the same job during manufacturing. As far as I know it's older tech.

[-Dustin]

Corima, I think? Mavic, too?

[progetto]

Lightweight as well. Foam can add strength as far as local buckling of the rim goes. Cores can add extra weight but can also allow a thinner outer wall laminate. Don't know about old school, just a different tact.

[tylerBICK]

The older Zipp 330, and 440 rims were foam core, and I rode both depths on the road and track and they were super durable and easy to true. Yes, a little added weight compared to the newer 303 and 404 designs, and not quite as aero, but made up for it in the abuse they took. I also couldn't name one modern foam core rim...

[Lionel]

My Corima winium have a foam core, so do my aerozenith. Both very good rims.

[Bssc]

foam core adds the benefit of being quieter , and a bit stronger with out being fragile

[Mike Mcdermid]

back in the old days folks built boats out of foam and fibreglassed em
we built arecraft out of foam and wrapped them and that was pretty much the norm
if you asked a boat or plane builder how to build a rim you wrapped a foam core

its been one of the foundations of composite construction for a long time as you transfer loads between both sides of the laminate someone already mentioned local buckling which makes them dog friendly at least

some used expanding foam to pressurize the carbon into a tool (mould) long before folks figured out
how to use bladders, some used the foam core and wrapped it like a surf board befor bonding an alloy rim on it and vaccing the lot ,the headache was getting the bladder out ,now we can use foam cores under latex, melt the foam out as it cures then pull the very very shrunken bladder out of the valve hole the foam and bladder is a mandrel to wrap the fibres over ,some rims have 3 plys in the wall which is just under 0.5 they survive testing ....even this modern method is now the old method,
theres some exciting new thingamy bobbies on the way

I havent seen a foam cored rim for a long time but would use foam in a heartbeat if it wasn't so old schools not cool especially in mtb frames

The newer rims which are being prepped for paris roubaix are the only rim that hasn't failed testing when every other rim did .... it doesnt have a foam core and its not very fragile so maybe foam cores will be relegated to the past

however tow braided rear discs????

[Human Epic Jolt]

Did silicon happen already?

[Mike Mcdermid]

Did silicon happen already?

dunno do you mean the tetravalent metalloid

[Human Epic Jolt]

dunno do you mean the tetravalent metalloid

Nah don't think so (sp.). I was talking with someone from deflt a few years back who was researching a bladder / forming process that could be extracted post. or spoke of it. Prob already in use.

Maybe there's some crossover there? reaction on contact? what are you working on?

[Mike Mcdermid]

Ah sorry i thought you meant in the brake track as per the basalt or Sic spray on coatings (zircotec)

"delft" as in university in europe??

silicone bladders are being used but Latex shrinks down when cooled i have some pics on my photostream somewhere

you should patent that "reaction on contact" for use in composite rims!!! i will have to send you a mail regards the other things though

[Human Epic Jolt]

Hmm. Flattery will only get you so far. delft as uni in europe.
was talking of what seemed in my mind to be not an air filled bladder. no idea really from my end.

er. how do i get my email to you without SteveP reading it?