byrd48

Hi,
I have a set of 21mm internal width rims, have ridden them for about a year with Conti 5000 25mm clinchers. I measured the tire width with calipers at 29mm installed. I replaced those tires with Conti 5000 28 TR tubeless ready tires, but with tubes. I measured those at 29mm installed. Would that make sense that both tires are measuring at the same width?
Thanks!
Jon

shelbyfv

If you know how to use a caliper (joke- some here don't) and you measure both tires at appropriate PSI, then it is what it is.

byrd48

I trust the caliper, just trying to understand why no increase in width, if it's something between clinchers and tubeless. In other words, how did I gain anything if the tires have the same width and height? Maybe the rubber is just thicker.

Trakhak

I understood that reference.

shelbyfv

Your pre-tubeless 5000 measured larger than nominal. That was my experience as well. The TLR is a different tire and apparently measures closer to nominal. Maybe others can report their experience but I think you are correct to attribute it to different construction.

Wileyrat

If you’re not going tubeless, you gained weight, since the 5000 tubeless weigh around 50 grams more than the tubed version. I’ve read the tubeless versions have thicker stronger sidewalls, which makes sense to me, give there’s no tube to help provide sidewall support.

Iride01 

How much tire pressure did you have each filled to when you measured? You also might ride the current ones for a year and measure again.

Probably a bunch of little things all adding up to make the results you see.

PeteHski

When Conti introduced the 5000S TR they also shrunk them to measure close to their nominal size when mounted on modern wider rims. The older 5000 was sized for narrower rims, so they would measure over-size on wider rims like yours. The older 25 mm tyres would measure true to size on narrow rims.

Steve B.

I mounted Conti GP 5000 S TR sized 28MM to my Bontrager Aeolus Pro 37 rims. When installed with tubes, they were exactly 28mm. When installed tubeless they are 30 mm, both times at 70-80 psi

byrd48

that’s interesting! I noticed when I took the 25s off, there was quite a bit of abrasion on the sidewalls. I’ve wondered if the wider rims exposed the sidewalls on tires because a 25 was really expanding to 29. I presume the changes you mention will alleviate that.

Steve B.

This is exactly correct with my experience. I have an older set of Conti GP4S tires 28mm, non-tubeless, on my gravel bike road wheels. The wheels are WTB i23, so 23 mm wide. The tires measure at 31 mm at 70-80 psi. On older 19mm wide Mavic CXP-33 rims, they ran 28.

Iride01 

Abrasion on the sidewalls might be you run them with insufficient tire pressure.

However for a 21mm internal width rim, a 25mm tire is about as narrow a tire you should put on that rim. A tire that is too narrow for the rim it's on is probably more of a issue than a tire that is too wide for a rim.

byrd48

It's certainly been a journey with these new wider rims. The rims are hooked and they state max pressure 75psi for my weight. At that pressure, with 25mm tires, I immediately got pinch flats, like 6 in three months. So I started upping the pressure eventually landing on 85 front, 90 rear, which seemed to stop the pinch flats, but now I'm going more than what the rim says I should, and closer to what I was running on narrow rims.
So moving up to 28 should also in theory have alleviated the problem, larger tire and lower pressure. However now that I install the tire, it's the same width and height as what the 25 was, so either I need to run these at the same pressure, or maybe hopefully they are just more durable since they are not expanding beyond their intended width. At any rate, the silca calculator says I should be able to run them in the 60s, but I just can't see that happening, even tubeless. If tubeless will let me get that low, then I'll switch!

Camilo

byrd48 What's the difference between "clincher" and "tubeless"? Aren't they both clincher - one being used with a tube, one without? It's not like one is a clincher and the other a tubular aka sewup. Or am I missing something?

PeteHski

Well you won’t get any pinch flats if you run tubeless at the Silca recommended pressures. I’m currently running 30 mm 5000S TR tyres at around 65 psi on 22mm internal rims. No issues and I weigh 80 kg and our roads are full of potholes.

squirtdad

Both are clincher but many tires come in two different builds, one for tube and one designed for tubeless (aka Tubeless Ready)

tires designed for tubeless have stiffer sidewalls in general and the tires designed for tubes are generally lighter

If you plan on only using tubes there is no need to go to the tubeless ready (but you can use those with tubes)

https://www.continental-tires.com/pr...tem-ccb0832fbc

https://www.continental-tires.com/pr...pingDTacs=Road

squirtdad

use a tire pressure calculator I like the rene herse....super simple https://www.renehersecycles.com/tire...re-calculator/

Iride01 

I use to say the same thing. However most old definitions before tubeless was ever popularized described a clincher tire as having a tube.

So I've quit making that assertion. Even though to me the tire is physically pretty much the same. And many bicycle tire brands seem to use clincher to only refer to tires with tubes.

Iride01 

What rims do you have?

The rims say they have a max pressure of 75psi? Or are you getting this from some calculator that is only recommending what your PSI should be?


EDIT.... Not really necessary for me to know. I later found this other post that shows me some rims now put a max PSI on them for various tires. I hadn't ever seen that myself till now.

https://www.bikeforums.net/23237853-post5.html

slow rollin

A tubeless tire should let you go lower since the sidewall and carcass is more robust while not having issues with pinch flats or other things. You could also do the opposite of "supple" tires and get gatorskins/marathons or whatever thick casing/durable tire+tube you can find and run it at lower psi.
All I can say is either the hoop stress is too high with bigger tires at certain PSI, or companies are protecting themselves excessively and thus recommending low pressures. BITD my parents knew people running 150+psi on 21's. Or our rims magically turned into ****** aluminum, but I doubt that.