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700x25c or 700x28c Armadillo All Condition Elites?

what’s the consensus? 25 or 28?
25 in the front, 28 in the back?

25 Replies

Amanda, May 5, 2017 at 7:44 am

My tires are black and round. Sometimes I have to have someone put air in them. And if I get a flat on RAGBRAI, some wonderful guy stops and fixes it for me. But I am the Princess!! LOL

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Charlie S, May 5, 2017 at 8:38 am

KenH wrote:: With 10k-25k riders all taking the same route, on the same day, for a significant number of miles RAGBRAI would make a good place to do a real scientific study of all the issues that affect puncture rates in the real world. But how much would the study sponsor have to pay some of you to ride something other than your beloved 23s? Aye, there’s the rub, there’s not enough money in the whole wide world!!

Not much rubbing required here – I’ll do it for free if someone gives me the tires!

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Barin Beard, May 5, 2017 at 9:27 am

I’ll be riding 650b (27.5″) x 2.3″ knobbies, with Stans. Should not be any issues…just slow.

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trek2300, May 5, 2017 at 9:27 am

Ken noted the 2015 Sioux City departure that I remember quite well. If memory serves me, within five miles of the dip site we crossed a railroad track. Within 100 yards of the tracks, I saw about 5 bikes pulled over fixing pinch flats. Regardless of what width tire we run, there has to be enough pressure in the darned thing to prevent the snake bites! I’d guess the train track victims failed to complete their pre-departure pumping obligation.

Unfortunately, I realize that by even mentioning the problem, now the tire gods will get even and I’ll spend most of XLV fixing flats.

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mootsman, May 6, 2017 at 8:20 am

trek2300, the advantage of tubeless tires is the complete lack of pinch flats. There is more futzing around though when mounting them and fixing the big gash cuts flats.

I’m not a fan of reducing tire pressure too much either. I know the math about air volume and pressure but the mechanical variables are more important like rim bead strength, how strong the tire hooks to that bead, etc… That calculation depends on many more variables like the particular rim, particular tire and lets not forget about the rider weight too.

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Zeb S, May 6, 2017 at 1:29 pm

There is no consensus (I’ve ridden rock hard 23’s on my crit bike and 32’s on my CX bike on the Rag) and my opinion is of rather than width the discussion should be age of the tire. Which ever bike I decide to ride, no matter the tire width, it gets new rubber a month for Ragbrai so I can put at the very least a hundred miles on them. I’m always amazed at the amount of folks waiting at rolling bike shop on Sunday morning cause they have a flat that most likely could have been avoided if they’d just invested in new tires.

Your mileage may vary.

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Brian Wallenburg, May 6, 2017 at 5:58 pm

BizzarroZeb, couldn’t agree more! Less flats on new skins.

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mootsman, May 7, 2017 at 8:33 am

I’ve read the idea about less rolling resistance and lower tire pressure. They are also lab theories devoid of the reality of rider weight, road surface, etc.. My experience is the higher pressure does have less rolling resistance under most circumstances. But even during the duration of a single ride, circumstances vary.

I’ve read lots of the latest articles from Velonews about everything from wider tires, tire pressure, road disc brakes and electric derailleurs. Keep in mind magazines use to make their money from subscriptions. Now most money comes from advertisers whose interest is trying to get us replace our perfectly good equipment with newer stuff. They even claimed wider lightweight road tires (not wide heavy tires) flat less then 23s. Thus helping the companies that provide the financial support for Velonews. I went though a lot more tires with 25s. They tested road discs by 2 guys rolling down a hill and hitting their brakes, really? What a joke as it doesn’t allow for rider weight and hand strength.

And on RAGBRAI, we see riders with 20, 30 year old tech or older. Let’s not fall for advertisers or their paid for publications.

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rjjensenia, May 7, 2017 at 9:47 pm

Mootsman, My experience would agree with yours. Higher pressure on rough roads suck, but on NICE roads higher pressure does have less rolling resistance.

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KenH, May 8, 2017 at 7:50 am

On a smooth surface rolling resistance decreases monotonically as you increase inflation pressure. More pressure = less rolling resistance. However there is relatively little difference in rolling resistance between running at the Berto pressure (the pressure which produces 15% tire deflection under load) and the maximum inflation pressure for the tire. On rough roads other factors come into play and the rolling resistance of the tire itself is only part of the total non-aerodynamic resistance you have to overcome to move forward. Real world tests have shown that lowering your tire pressure on rough roads does give you less resistance as well as a smoother ride. It’s not just a theory or an effect that is only seen in the lab.

The vast majority of the RAGBRAI route qualifies as smooth roads. Rough pavement is rare. My inflation strategy is to pump them up to the max, stop at the beginning of the gravel loop and let some air out, pump them back up to max at the first opportunity after the end of gravel loop and leave them there for the rest of the week. Unless the pre-ride report has identified a stretch of road as rough and then I will drop pressure for that too. But I never run at less than the Berto pressure so I see very little increase in rolling resistance on smooth roads even if I can’t refill them as soon as I like, or forget to do so.

The problem with heavy riders and skinny tires is that you can be near or below the Berto pressure even when inflated to max so that is why I say that some of us might need 25s or more on the rear. For example with a 220 pound rider on a 12 pound road bike with the typical weight distribution the Berto pressures are 96 psi front and 150 psi rear. Do you have a 150 psi tire on your rear wheel? If you go to a 25 on the rear the Berto pressure is 126 which is a little more common and with a 28 on the rear it is only 105. With my 38s the Berto pressure is 60 psi and max is 85 so I can run comfortably over the Berto pressure when I want to minimize rolling resistance on a smooth road. Now, I don’t personally weigh 220 pounds but then my bike doesn’t weigh 12 pounds either so those number also apply to my situation unless I can manage to loose a few before the end of July!

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