Expanding foam inside a carbon frame

dieselgeezer

I've got 2 carbon frame road bikes. The old one is sublimely quiet. The newer one is very noisy, transmitting gear train noise like a tractor. To check, I transferred all of the gear train (mechs, cassette, chain, chainset) from the old to the new bike & the new bike was still as noisy. I can only think that the new frame is acting as an echo chamber & the old one doesn't.
I'm thinking of injecting expanding foam into the new frame to dampen it down. Has anyone done this? Also, the new frame has internal cable routing; I was thinking of leaving the outer cable (inside the frame) in place & then injecting. This way I reckon I could pull the old cable through when the time comes to do a cable change.
Any thoughts?

philclubman

Sounds like a strange thought to me to add extra weight to your carbon bike?!

I'd say there's something wrong or your very sensitive if the drivetrain noise is too much.

Was the chain okay - I'd start by replacing.

daniel_b

Ummmmm.......

My only thought would be:

No.

buckmulligan

This sounds like a spectacularly bad idea. Let us know how it goes...

fenix

Ear plugs might be easier.

perfectmark

Out of interest, have you got a recording so we can hear what you are talking about? I would suspect that it is just a side effect of the differences in carbon construction between the bikes and how they transmit noise down the frame.

smudgerii

Well that OP brightened a very dull night shift...

One of the funniest things I've ever read.

dodgy

Maybe the noise you're hearing is the the internally routed cables rattling around the inside of the frame? Difficult to sort. And a definite no on the expanding foam idea!

dieselgeezer

I've already stuffed the frame with (removable) foam to stop the cables rattling, which has worked. The noise I'm getting is the chain meshing with the chainset, cassette, jockey wheels. Lubing helps a little for a short while. No problems at all with the "quiet" frame using the same components hence why I think it's the frame acting as an echo chamber.

cougie

What frame is it?

dieselgeezer

The noisy one is a Merida.

father_jack

I would recommend filling your carbon fibre frame with Osmium.

dodgy

How many miles so far on the Merida? I find transmission noise fades about 200 miles in on a new bike. Same after fitting a new chain.

fat daddy

I have an S-works Roubaix SL1 - its deathly quiet ... took out a mates SL4 the other day, its surprisingly loud ...... the difference is thinner lighter carbon and bigger tubing that has more air inside

I wonder if its a thing of the newer fatter, yet thinner and stiffer walled bikes .... I personally quite like the noise, for some reason it makes the bike feel lighter as you can hear all the parts moving its like there is nothing holding it all together

homers_double

My mates Forme squeeks and rattle like a beast and ny carbon Trek is stealthily quiet. I look after mine and him... Not so much.

Just a thought???

mugensi

Father Jack wrote:

I would recommend filling your carbon fibre frame with Osmium.

Expandium is a better option.

Monty Dog

Expanding PU structural foam is commonly used in composite construction but getting the amount needed is tricky - I have some direct experience of this having got the dosage wrong once! Make sure you mask the inside and outside of the frame well as any overflow is very sticky and will probably damage the exterior frame finish. Spraying water inside the frame improves foaming and adhesion but once started it's a process you'll have no way of going back!

The Rookie

Correct amount is critical or the expansion can split the frame, I've seen a car steel box section ripped open by expanding foam.

ayjaycee

MugenSi wrote:

Father Jack wrote:

I would recommend filling your carbon fibre frame with Osmium.

Expandium is a better option.

Unobtainium might be an even better option.

StillGoing

dieselgeezer wrote:

The noisy one is a Merida.

Merida what? My Reacto is fine. That has soft foam tubing as standard around the cable outers inside the downtube.

fenix

Did the OP ever go ahead with this ?

buckmulligan

I hope so...