jadocs

You state there are reasons for going tubeless/tubular for MTB/Cross, but say it doesn't make sense for road. Wouldn't the same benefits received on the MTB/Cross also be realized on road setups....or are you saying that the benefits on road are far less critical and therefore do not drive a need as it does offroad? In my mind there is a benefit if I can improve ride quality on the road and reduce the occurrences of having to stop to fix a flat.

Psimet2001 

Yeah the benefits for mtb and cross don't have anything to do with ride quality. They have everything to do with striking objects while riding. That's it.

Tubeless tires are not as supple as tubed tires are. Not sure where that got lost in all of this. If they were they'd be popping off the rims left and right. As for total ride quality - tubular still prevails. They even have mtb tubulars but only a small handful of racers in Europe use them.

chaadster

Really? That got lost on me because I think that suppleness is in the casing construction, but that retention is to do with bead and rim design (i.e. hooked) for road tires, and that the bead shape doesn’t really have much to do with casing, which is to say that bead material and shaping doesn’t, of necessity, preclude a supple casing. Do I have that wrong? I’m interested to hear your thoughts on that.

noodle soup

You are correct, Casing stiffness has nothing to do with tire retention.

chaadster

Well I’m not saying that. I mean, casing stiffness can help with bead retention by giving the bead rigidity, but it’s not necessary for the casing to do that with proper bead and rim design. There can be shaping to the rubber material around the bead which helps it lock in the bead hook, right, like with the Mavic UST spec.

JohnJ80

^this. Completely agree.

Tire pressure is key and it’s a fairly narrow band. Read Josh Poertner’s story about Zipp’s work to get carbon wheels used on the cobbles back when he was technical director at Zipp. Couldn’t get it figured out until they figured out that pump gauges are all over the place and testing they did exposed this as a 12psi variation which was larger than what they were trying to make work. So getting that right and being accurate is key. You won’t realize the performance gain if your tire pressure is either too high or too low. First suspect in figuring that out is the mechanical gauge on your pump.

J.

Koyote

It doesn’t matter if a gauge gives on “accurate“ reading or not… What matters is consistency. A given rider, with a given gauge, needs to figure out the psi that works best for him or her and then stick with it.

But with that said, the gauges that are built into pumps tend to not match up with the readings I get from actual separate gauges.

Branko D

Well, a larger tire at the same pressure is a stiffer spring and gives a harsher ride, so comparing 28s at 77 psi and 23s and 77 psi isn't the same; I've ridden 23s that low after patching flats and they get all magic carpet over road irregularities but it's too soft for spirited riding. I have some 42mm tires on a touring bike, if I inflate them to 77 psi, close to their max pressure, they give a rock hard ride, way overboard.

JohnJ80

well, not totally true. Instruments in general need to be accurate and repeatable.

If you don't have both you can't use either the tables a lot of wheel/tire manufacturers supply (i.e. Enve as an example) or the high quality calculators such as Silca supply. They are going to assume repeatability but they also won't work if you don't have good accuracy. And trying to find that sweet spot experimentally is going to take a very long time and a lot of work. You basically need to ride a course, get the time/power and then let out 5psi and do it again. Then once you get it to within 5psi then you need to go at it again until you have it within about 2psi. Lots of variability in the process. Needless to say that if you then borrow an uncalibrated pump, who knows what happens.

If you read the blog post, the engineers at Zipp built a manifold and put several pumps at time on it is so all the pumps all saw the same pressure at the same time. The accuracy was spread over 12psi. In their case, that contributed to breaking carbon rims and until the resolved it, they couldn't get the whole thing figured out. Separately, Lennard Zinn looked at it in a recent column and found that to be a similar problem with mechanical gauges on pumps (even supposedly quality pumps) but that digital gauges tended to be much more accurate with repeatability.

Correct pressure is a pretty narrow band but the results are worth it in ride quality and overall efficiency. Here's the Silca calculator which comes from their experience in advising and testing with World Tour teams. I've found this to work pretty well for me.



J.

noodle soup

Correct. A properly shaped bead doesn't need a stiff casing/sidewall to stay tight on the rim.

Koyote

“Repeatable“ is what I meant by “consistent.“ I found Silca’s table doesn’t work for me. This is why I think that each person needs to find their optimum psi and then stick to it… And as long as your gauge gives consistent readings, you can do that. It’s sort of like the old saying about how a man who owns one watch knows the time… A man with two watches never knows.

Branko D

Yeah, given the margin of error on pump manometers, a part of people shouting past each other could be that one pump could very well show 10 psi more or less than another pump, which is a big difference in feel.

JohnJ80

The Silca calculator was a touch high for me but very effective because I started out in the vicinity. For someone who rode 23c tires at 100 psi (as did many of us), it's a LOT of work to go from there down to 58/62psi (F/R) going 5 psi at a time. To be fair, would have been starting at 80psi for the tires I was using at the time but still. The reason it was a touch high was that our "old asphalt" is somewhat better than what they describe - but still, it's pretty close. It was about 5psi high.

It's still a giant PITA to start off and try it all by yourself.

And, using your method instead of calibrating your pump and having an accurate gauge, is you cannot use any other pump. That's the problem with not knowing the accuracy of your gauge and presuming it's accurate is a fools errand. Repeatable but not accurate is only slightly better but still in the PITA category.

So in large part, we disagree.

J.

Koyote

This is my gauge -- how does it prevent me from using any other pump?



I tried the Silca calculator. It recommended pressures a bit lower than I had already settled on. I'm glad you like the calculators and find them useful, but a little online research combined with a little bit of experimentation easily got my psi where it works best for me...And I had gotten there before these calculators were on the 'net.

Psimet2001 

Apologies on the bead retention. Early on with tubeless sidewall stiffness was a factor as bead and rim designs were so poor and inconsistent. In general tubeless tires have a much heavier casing and lower TPI. It's across the board. They are not as supple as tubed tires and aren't even in the same class as high end tubulars (300+TPI vs 60 or 120TPI for most tubeless).

Tubeless is really about flats. If you're not having them then there's no real point in switching on the road.

Sy Reene

On a quasi-related topic, what are your thoughts on the industry apparently starting to abandon rims that are not also tubeless compatible?

noodle soup

Why does it matter? Non-tubeless tires work fine on hooked tubeless rims.

Sy Reene

Let the man answer...

noodle soup

His response is irrelevant to my question to you.

Sy Reene

No, sorry and of course not. I just will refrain from answering until after Psimet does.

Branko D

It might be just me with a small sample size, but I find it more difficult to get tires on and off tubeless ready rims than non-TL rims.

WhyFi

Do you make proper use the relief channel in the middle of the rim bed? Any of my early challenges with un/mounting tires on tubeless rims, tubeless tire or not, were solved by being more deliberate in that regard (also ending at the valve when mounting). No tire has been particularly difficult since and I've never needed a lever or other tool to mount.

robbyville

whyfi, I can’t remember but have you mounted the gp5000’s yet? Those continue to be the most irksome for me and I keep buying them lol!

it could be the combo of my wheels and tires, I haven’t put them
on my alloy I9 wheels yet since I threw some old specialized turbo tubeless that I had on them but will need to replace those soon.

The Conti’s are the bane of my existence when it comes to mounting for the first time

WhyFi

No, and I won't be any time soon - my current wheels are not compatible.

One guy in my club, upon his first tubeless foray, was so frustrated with trying to mount the Conti to his Ardennes that he gave up and went back to tubes. I never did get a crack at helping him, but they may still be around... Another club member, a short time after, had no issue mounting his new GP5Ks and razzed the first guy when he heard about the troubles.

noodle soup

Yesterday I helped a friend install her new GP5000 tires on a Light Bicycle AR46 wheelset. I managed to get the tire on without tools, but she needed to use a Pedro's lever to get the last 5 inches over the bead hook. They are harder to install than most tires, but with proper technique and a little hand strength, they aren't impossible.

@WhyFi Please continue to shame your friend that gave up.