Do foam inserts for tires work?
 

Four day bikepacking trip coming up and I’m considering trying foam inserts in my wheels. What experience do you all have with these and what are the pros/cons? I’ve bikepacked several trips before and ridden 1000s of miles tubeless.

Yes they work. they generally are a huge PITA to install. Unless you are going to run stupid low pressure or are bombing rock gardens on a bike packing trip I dont feel like they are needed.

are there specific issues you've had in the past that would have you consider foam inserts?

I do not use them, but have friends that do.

They do what they are supposed to do: protect the rims while running pressures low enough for rim strikes.

If you are not currently getting rim strikes, and you are not looking to drop your pressure, they don’t serve a lot of purpose IMO.

I'm thinking prevention rather than curing a problem I've experienced. My BP trip will be remote and has no resupply stops so i'll have extra pounds on the bike.

Tubeless is supposed to be the “cure” for pinch flats. But pinch flats are physics’ way of telling you that your tire pressure is too low. Rim strikes are just a far more expensive version of physics talking you that you don’t have enough air in the tires. Would the ride qualities really suffer from putting just a few more psi of air in the tires?

In some cases and applications.... yes.

Also what you are saying about pinch flats and rims strikes is not the whole story. There is a window between what will give you a pinch flat and what will actually dent a rim. With tubeless I can run my pressure a few pound lower than gives me pinch flats without denting my rims. Been doing so for many years. With tubes, and a ~2.3" rear tire, 28 is as low as I could go in the rear before getting pinch flats. With tubeless I was down around 25 and never dented the rim. Front was not relevant for me, as pinch flats were never really the limiting factor for how low I could go (stability was).

Inserts let you go a lot lower without denting a rim. Whether that is worth the extra weight depends on what the application is. Bikepacking is probably not an application that warrants inserts.

EDIT: I guess I should have differentiated between rim strikes and rim damage. The point of foam inserts is to allow pressures that would otherwise risk damaging the rims.

I struggled for quite some time to get my wife's tire to mount with a Vittoria gravel tire insert. I failed. Two bike shops failed. I pulled out the insert and the tire set up nearly instantly.

I also found (on my own bike) that my traction in dirt/gravel actually improved a bit when I inflated the tires more. The irony with supple tires is that they require a greater air pressure.

I’ve been mountain biking since 1984. I’ve never found a situation where I need my tires to be flat to ride.

If there is a window it is a very, very, very narrow one. I never pinch flat. I also never dent rims except for a single incidence where I missed hopping a curb correctly. I have seen a whole lot of tubeless rims that look like someone took a hammer to them.

https://cimg8.ibsrv.net/gimg/bikefor...13d35d51c.jpeg
https://cimg6.ibsrv.net/gimg/bikefor...76e3b2bb4.jpeg
https://cimg9.ibsrv.net/gimg/bikefor...eacd176f9.jpeg

I don’t recall what the rim was but that’s a Hadley hub…$400+…, probably a $90 rim, spokes, and labor for build. It’s close to a $600 mistake. (And the owner was an idiot since that wheel is worth a relatively cheap rim replacement.) A bit more air in the tire would have saved a whole lot of money.

Really?! 3 whole psi! That’s astounding!

Sarcasm aside, that’s the very narrow “window” I’m talking about.

Air also allows you to avoid damaging a rim. It’s cheaper and lighter. Bikepacking puts extra weight on the bike which kind of negates any benefit you might get from running lower tire pressure anyway.

Stewart I'm failing to see how destroying a $90.00 rim is a $600.00 mistake?

I am failing to understand the point of almost anything he writes.

EDIT: removed some unnecessary snark that I repeat in another post.

What potential problem are you trying to solve for? As I understand it, these inserts are to get you an extra dozen or so miles. If you have a problem on day 1, I wouldn't count on living with just the insert for the next 3 days.

Your question is a good one: what problem is trying to be solved here that warrants the extra hassle and weight?

While inserts can give you some extra pedal time if you flat, that is not the main reason for them. The main reason for them is to allow you to run lower pressures without damaging the rim. They also give some extra sidewall support at the lower pressures.

Who said anything about riding around on flat tires? Straw man argument there.

If that was just you being dramatic, then remember that not all situations in mountain biking involve you. There are tens of thousands of other MTBers with their own situations, some very different from yours.

The point of this is what exactly? People have been trashing rims since long before tubeless. Run the pressure too low for your tire/wheel setup, your terrain, and your riding style and you can trash a rim. Tubeless just lowers that pressure threshold.

an 11-12% drop in pressure is a noticeable difference in performance. Most MTBers would notice it back to back.. And that is just how far I dropped it to get it where I wanted it. Lower than that and I was giving up too much stability for my tastes. Other people drop it even more when going tubeless.

Isn't another reason to use these inserts to make the tires more resistant to flats? A centimeter of foam between the inside of the tire and the inner tube could be significant.
The Schwalbe "Marathon Plus" has a sort of foam insert under the tread, not as thick, but in my experience has been almost 100% effective in preventing flats on my commuter bike.
https://cimg0.ibsrv.net/gimg/bikefor...2fd6595495.jpg
Cross-section of a Marathon Plus at "autopsy" after a significant failure. This tire had about 3,000 flat-free miles on it.

I’m pretty sure the inserts the OP is referring to are the ones that install against the rim.

From the Cush Core site:


https://cimg2.ibsrv.net/gimg/bikefor...07939c1cf7.png
https://cimg4.ibsrv.net/gimg/bikefor...c74dd65037.png

Thanks for that. I had not seen that type of liner. I was thinking of this one, which seems to me more designed to prevent flats, though they are claimed to prevent rim damage and allow a certain amount of "running while flat".
https://cimg8.ibsrv.net/gimg/bikefor...90ddf0d259.png
Tannus tire liner.

Huh. Maybe he was talking about that.

In that case, to me tire choice is more important, ie not a tire with a thin sidewall if you know you could be in sharp rock stuffAlong with prudent tire pressures for the weight of you and your bike vs terrainAlong with prudent riding over stuff, a few seconds more or a minute or whatever walking a bike over bad stuff worth it depending on remoteness etc etc
in other words, using proper judgement and tire choice

It’s a $600 mistake because the guy donated…i.e. “gave away”, aka “got rid of”…the wheel. That’s $600 out of his pocket because he was an idiot.

If you can compress the tire to the point where the rim hits the ground and damages the rim, the tire is flat.


While people have damaged rims in the past, tubeless and running low pressures have increased the number of rims that are damaged. And my point is exactly what you said. Ruining a wheel isn’t a cheap mistake. Adding a bit more air is cheap insurance. Tubeless doesn’t lower the pressure threshold, it just masks the clue that you might have a problem. Pinch flats tell the rider to increase the pressure a bit. With tubeless, the indicator is a dented rim. Very large difference in cost.

+1 and I'll ask again. rbrides, what are you trying to achieve? Fewer puncture flats or protection from pinch flats or both? We're all just guessing at this point and could answer your question better knowing what you're looking for. Also, check reviews on Amazon, web bike sellers, etc., of some of the inserts available. After reading many of these I decided none were for me as they all seemed to have some drawbacks that would have been made them worse than just getting a stiffer sidewalled and more puncture resistant tread tire even if it was on the heavier, slower rolling side but still rode better than any tire with inserts.

No argument there :)

In the spirit of "flat prevention", which I think may have been the OP's motivation for asking about tire inserts, I have a possibly interesting case report.
In Post #15 I mentioned a "significant failure" of a Schwalbe "Marathon Plus" tire. About 2 weeks prior, I had the first flat ever on one of these tires, which had been in service on Chicago streets for at least 3,000 miles. I found a solitary puncture that breached the blue gel layer and the kevlar carcass. I placed a new tube and a Mr. Tuffy tire liner, which I thought was a bit of over-kill, but not unreasonable since this is my commuter bike. About 2 weeks later, I noticed a "thumping" feeling while riding or walking the bike. I traced this to a swelling on the tread of the rear wheel. I reduced the tire pressure somewhat to get home, and changed the tire.
The bulge seemed to be in the same area as the prior penetration, which was still apparent (see image). However, on the inside of the tire there was much more extensive damage (see images). I am not sure how an object that made a simple puncture, albeit good sized, could rip the inside of the tire this way. At any rate, I think I was lucky to have the tire liner in place. I transferred it to the replacement Marathon Plus... again, probably over-kill.
Submitted for consideration!

https://cimg5.ibsrv.net/gimg/bikefor...ccdea6cf16.jpg
This is a view of the bulge, seen on the way home after I lowered the pressure. The old puncture is visible.


https://cimg8.ibsrv.net/gimg/bikefor...9168fdcde7.jpg
Here's a side view of the tire bulge and the original perforation. It's interesting that the bulge is on the side, not in the center where the defect is.


https://cimg7.ibsrv.net/gimg/bikefor...bb5fdd1ff1.jpg
Here is the hole left by the object, which I never found. It's a pretty good size, but otherwise nothing too extreme.


https://cimg1.ibsrv.net/gimg/bikefor...b4f55c3326.jpg
This is the inside of the tire. The damage extends a centimeter or so. See the next image...


https://cimg3.ibsrv.net/gimg/bikefor...3da7d5d12c.jpg
Here's the damaged area everted slightly. If the tire liner had not been present, I think the tube might have herniated through this large of a hole.

The point of inserts is that they help PREVENT that damage so you are not riding on a flat tire.