Tire question
 

Do you think specialized armadillos 700/28's would be okay for riding on unpaved fire roads in a local state park? Or should I put my Kendra 32's back on for riding on those trails? I am thinking of doing some over night trip to the Myakka River state park, to explore parts of it I have not seen yet. I'd be riding from my home to the park which is about 30 miles away, up the trail and camping overnight then riding home the next day.

How far are you going on the fire roads?

Depends on which campsite I use, anywhere from 2 to 10 miles.

Probably fine, especially if the roads are hardpack and not loose gravel. 32s would probably be a little more comfy particularly if loaded for camping.

Kendra 32's back on

28s would likely be ok
32s would almost definitely be better

fatter tires can give more traction
absorb road irregularities better
and better protect from pinch flats and rim damage

there is no advantage to runing narrow tires like 28s on gravel or dirt
although it can be done

I haven't found fire roads or trails to be particularly tough on tires. You can get pinch flats, but that's not the tire's problem. Wider tires offer better traction and flotation on soft surfaces and can be run at lower pressures without increasing the propensity to pinch flat over a narrow tire at higher pressure.

I'd go with the 32's to smooth out the ride.

You don't need more advice here, but nobody's mentioned weight. If you're a 130-pounder, you're good with the skinny tires. I weight 240, and I ride at least 35mm on pavement.

Unpaved fire roads can be gravel, gravel with ruts, hard packed dirt, loose dirt with ruts from water runoff, combo of dirt and mud. But having said that I ridden on hard packed dirt and gravel roads with 23's and I weighed 160 at the time. But the wider tire is more stable and more comfortable and least likely to get a damaged rim out of the ride.

What?! I'm at 224lb now, but last season I was 240lb, and I rode 23s on one bike, 25s on another, and 28s on the commuter!

So, while 35 min isn't required for pavement, your point that weight should be considered is worthwhile.

At your weight using 23's was not idea, if you add 240 plus another 20 for bike and kit and accessories you should have been running at least 150 psi in the rear and no tire is rated for that pressure! Even at your now 224 plus the 20 you would still have to use at least 140 psi in the rear, very few tires are rated that high. The very smallest tire you should be using is a 25 and that's marginal!

It won't be the most pleasant ride and will be less pleasant the further you ride but the tires should do fine. The difference between a 28mm tire and a 32mm tire isn't much (a bit over 1/8") and probably isn't going to make that much difference in the ride. If you were to go to a 2" tire like a mountain bike tire, you'd really notice the difference which is why mountain bikes use such wide tires but you'll not notice much between the narrower tires.

To me it would depend on the surface of the trail and your attitude. Big, loose gravel demands wider tires. If you're willing to walk the worst sections, you can ride almost anywhere with 28 mm tires.

Holy cow! I've been 210+ consistently since, oh, the turn of the millennium, and never ridden anything on a road bike bigger than 25, and often on a 22/24 F/R combo. That's thousands of miles at no more than 120psi, and with very few flats and no ruined or even out-of-true wheels. And I'm not noodling and putzing around town, either.

It must be we have different definitions of 'marginal'! :lol:

Hmm, what F/R weight bearing split are you using? I've never measured any of my bikes for that, but usually run 90-100psi F and 110-120psi R. Seems to work fine, though I'm not particularly enamored with the feel of my Michelin Pro Optimum 25s; a little too squishy.

The real horror of horrors is that I've done 1700miles this season on 23s mounted to 20 spoke F+R Mavic wheels!! Maybe I should change my user name to DancesWithDeath!

On a related note, I am considering giving a wider set of rims a try, in particular, the Flo 30s with 24mm bead seat. I've got a set of 28s of 25mm wide Velocity Blunt rims for my commuter, and I really like the characteristics of the handling and feel. they look super lo-pro too, which is sweet; all rim, baby.

Oh, I forgot, I do have 32s on my winter wheels for the commuter, but I hardly use 'em.

You can laugh all you want but your riding on marginal safety. Here, take a look at this calculator and use the middle one, and let me know using a 23 tire if you can put enough pressure in one, especially the rear, for your weight PLUS the bike's PLUS all the clothes you wear PLUS accessories on the bike, and still maintain the optimum 15% drop. Obviously you can do whatever you want, I'm just saying I wouldn't do it nor would I ever recommend someone to do it.

You didn't provide a link. I think this is the one you are talking about, however. I find it totally wrong. I have bikes that have tires across nearly his entire spectrum. For my weight, the suggestion for a 23mm tire is to run the front tire at 104 psi on the front and 160 psi on the rear. The 104psi for the front I can agree with but I would...and have... run a similar pressure on the rear without issue.

On the other hand, it suggest that I use a pressure of 58psi on the front and 88psi on the rear for a 32mm tire. If I were to run that kind of pressure on even a unloaded road bike, I'd suffer pinch flats constantly if not rim damage and the front tire would be mushy. If I add a touring load, it suggest that I use 70 psi in the front and 106psi in the rear. With that wide of a tire, the rear one is dancing on the edge of constant blowout and the front one would still be mushy.

Putting in my wife's weight gives a 27psi front/41psi rear for a 32mm tire. I consider that kind of pressure to be a flat tire. I think most people would look at the pressure recommendations...and they are really only recommendations...as completely inappropriate.

I have not found anything you said to be the case. HOWEVER, you can run whatever tire pressure you want because it works for you because like you said they are recommendations. But to maintain a close 15% recommended drop, which is idea for street use in regards to tire wear and handling, then that calculator is close to correct within 5 psi plus or minus. Some tires do recommend other PSI's so you have to refer to their package to find out what their preference is. I do know that a set of Vittorias I bought came with a chart on the package, and what did I see on that chart? The same guidelines that the calculator would produce! I also do some touring, so far only weekend stuff, and I haven't once felt the tires were dancing on the edge of a blowout or the front feeling mushy. Also most tires have a min and a max psi, never go below the min or above the max no matter what the calculator says. But I suggest that maybe your tire pressure gauge is inaccurate?

Professionals use to use the same chart that the calculator is based on for years, but then someone came around and said higher psi was better for racing, so they all did that, but now they are realizing that all that higher psi was false and their starting to run closer now to what the chart/calculator indicates.

read this for more info: http://semiprocycling.com/six-steps-...-tire-pressure

I'm not sure what you mean by this statement. Does the calculator...you haven't confirmed if the link is the one you used...not suggest 27 psi/41 psi for a 125 lb load? Does it not suggest a 106 psi load for a near 300 lb touring bike on a 32mm tire? The former is way too low to protect the wheels and the later pressure is way over the pressure limits I've seen for a 32mm tire. Vittoria has an app that suggest 110 psi front/ 115 psi rear for a 23mm tire for the load that I put on a bike. That's more in keeping with the kinds of pressures I've run for decades on that width of tire.

The problem is that I don't agree with the 15% drop idea for a couple of reasons. First, in order to get to that kind of drop, I'd have to run stupidly high pressures on a narrow tire. 160 psi is just dumb for every day pressure on a bike. It's hard to achieve and I haven't seen many tires that have that kind of pressure limit.

Secondly, it's too low for many applications. A tire that is running less than 30 psi and is 23mm wide is flat even if are only running a 125 lb load on it. It's going to wallow around corners and most people wouldn't like it.

I've blown plenty of wide tires off the rim at what I would consider to be low pressure. I blew 4 tires in one day (first day out) on a 37mm tire that was inflated below the maximum pressure. And that wasn't the first time that I'd blown tires off the rim at less than the maximum pressure rating. Almost all of the blow off problems have been with one brand, which I don't use anymore,

Um...I don't know where you got this idea but it is wrong. Racers have used high pressures for as long as I've been riding a bike (30+ years) and I've never seen any kind of chart for tire pressures prior to the 2004 chart that Heine uses. If there were a chart out there, it would have been published in the bicycle magazines. They publish everything else, many times.

The main problem I have with Berto and Heine's ideas is that the pressure seems to be linear. I don't think that the "optimum" pressure for a tire is a linear function. Their model is too simplistic and doesn't account for real world conditions and limitations. Heine needs to take into account other variables that he hasn't considered.

Pros have been using higher pressures for a long time and I stated that, however lately they have been reducing their psi.

Cyccommute I don't want a running argument with you, I don't know why your tires would have blown off unless they were below the tire manufacturer's minimum psi requirement which a person does have to look at before they put 25 psi in a tire. Or maybe your air pressure gauge is incorrect. Whatever the reason it doesn't matter, like I said before you use whatever psi you want and lets leave it at that.

I agree that pros (and most other cyclists) have been using high pressures for a very long time but it's not because of any charts they were consulting. The pressures that are run in tires are largely a matter of guess work. Even now, I don't think there is anything definitive about tire pressure. Even the manufacturer's recommendations are largely based on guess work. Heine and Berto's work is an attempt at a definitive method but the model doesn't fit real world experience for the reasons that I detailed above. If their model worked, then people who weigh next to nothing could ride with the kinds of pressures that they recommend. A lightweight person could ride with 25 psi in their tires and not have any problems. On the other hand, I should suffer some detriment to not running 165psi in my rear tire on my road bike. I've never notice that 110 to 115 psi was causing my any issues and I wouldn't want to ride with a tire at a higher pressure. I see no benefit.

The problem with Heine's model is that it is wrong. That's not necessarily a bad thing because, as George E. P. Box said, "All models are wrong. Some are useful." Heine's model is wrong (as are all models), his just happens to be wrong enough to not be useful.


As for the blow offs I experienced, it wasn't the pressure gauge since the tires had been pumped to pressure with 2 different pumps and the tires blew off 2 wheels twice. It wasn't really the load since the load wouldn't have made that much of a difference in the tire pressure. It's a systemic problem I've had with Continentals. I've had them blow off on Lolo Pass in Idaho just after inflating to the recommended pressure. I've had them blow off while sitting on a car rack. And I've had them blow off that 4 times in Texas. I eventually found a pressure that I could ride them without blowing off the rim...it was around 60 psi...but the pressure was so low that I had to be extremely careful with bumps and pot holes to avoid pinch flats. I don't run that brand anymore because of the many, many issues I've had with their tires.

So the problem was the tires not the PSI.

the strange thing about cyccos story
is that continental tires have
or had
a reputation for being able to withstand double the pressure printed on the sidewall

years ago
i had a 700 x 28 conti tire
that i inflated up to 160 psi
for a couple rides

it wasnt very comfortable
or efficient
but it didnt blow off the rim

although
continental is also responsible for the second most defective tires
that i saw during my decades long career in bike shops
i recall 26x2.0 or so
town and country tires
made by conti
that probably half were virtually impossible to get mounted straight on a rim

i heard there is a vast difference between cheaper asian made contis
and the fancy german ones
the town and countrys were made in thailand i think
but i do not recall the provenance of the 160 psi road tires i had

and for the record
the manufacturer from whom i saw the most defects
was specialized

Six of one, half dozen of the other. If the tires won't hold the recommended pressure, then they are either overrated or poorly designed or both.

The first set of Continentals I owned were the Top Touring on a 2003 Cannondale. That one blew off on the top of Lolo Pass in Idaho. Another Top Touring blew off on the back of a car a year later. I had the 2 Touring Contacts that blew off the rim 4 times in one day and I've had a Touring Contact that split wide open when I hit a small rock on a downhill in Kentucky. I've had hundreds of tires in my years of cycling and haven't anywhere near the problems with any single brand nor even a single tire as I've had with Continentals. Continentals may have had a good reputation in the past but after having been left flat...literally...5 times, I'm done with them.

ALL tires can handle, or should handle, double the psi that's on the sidewall, that is their safety margin, that doesn't mean you should ride it that high though, however I have known clydesdales to put 5 to 10 psi over the recommended sidewall max psi and never had an issue, but any tire manufacture will tell you not to go over the max psi due to obvious legal concerns. Once for an experiment I put 240 psi in a (ca't recall the tire brand but it wasn't Conti) tire just to see if a glueless patch would hold (I put the rim in a trash can with an extension hose to my air compressor trigger), I left that psi in that tire for 2 weeks; and in case anyone is wondering, the patch held fine and I used that tube for couple of years after that as a main tube.

I have had major issues with Conti tires myself, mostly short life expectancy, the sidewalls are paper thin and anything can either go through it or rub against it and ruin the sidewall, I nicked a small rock about 2 inches in diameter once and blew the tire. I've tried various models of Contis over the years and the only one that lasted the longest was a Gatorskin and I got about 1200 miles on one and 1800 miles or so out of the other before something happened to them. And just like Cyccomute I too have had plenty of brands over the years and none have had the issues that I've had with Conti. Maybe it's just us, maybe Conti tires just don't like our bikes so they want to be taken off as quickly as they can! I know Conti has come out with a couple of new tires that look promising but after 5 or 6 different models failing I don't want to risk getting them ever again, so I'm also done with Conti's. You know the old saying: "Fool me once, shame on you. Fool me twice, shame on me", except I took it to the extreme and got fooled 3 or 4 times after that!!!