rydabent

Sorry it has been proven that a wider tire up to a point is faster. A wider tire absorbs bumps and does not lift the bike and rider. When a bike is forced to rise, there is a drop in speed. It uses up forward motion energy to to lift the bike and rider. Simple as that.

cxwrench

I don't think you read his post thoroughly. The article is 'myth...wider tires are slower'.

ofajen

Hilarious! Not as pretty a scene but here is my ride:




I’m guessing yours was slightly later. Mine is 88 and has the U-brake.

Otto

wilson_smyth

Op here, reporting back with some rock solid, incontrovertible, highly subjective results!

Cycled to and from work today with the tires at a shade under 50psi, down from 70.

It was much more comfortable, particularly on the rough canal path, but even on the rough bits of road that have been repeatedly dug up and patched.

Can't say if I'm faster with the lower pressure as I was cycling with a 12kg pack so not my usual spin, but I did notice that where i used to think the front wheel drifted a little, but then though it must be my imagination, it was much more stable and precise now.

The only model I can think of that would cause this is that at 70psi, there was far too little tire on the road so it was not as stable.

May let a few more psi out of the wheels but need a more precise pressure Guage first.
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FiftySix

Not that I have anything really worthwhile to contribute, but for my bike with 700x42 tires, I run starting pressures of 50 to 55 psi and let that be for a week or two as the pressure naturally lowers itself over that time frame. When the rear tire squats too much for my preferences (maybe 35 to 40 psi), I bump the pressure back up to 50-55 psi.

Comparing that 700x42 tire bike with my 700x38 tire bike, the 38mm tire bike coasts with ease compared to the 42mm tire bike, but it's due to better wheels and bearings IMO. The 38 mm tire bike has always coasted better no matter the tire selection.

Branko D

This has nothing to do with tire width but rather everything to do with tire pressure. Overinflated tires become inefficient due to suspension losses, particularly on rougher surfaces, underinflated tires are inefficient due to hysteresis losses. Overweight cyclists or those riding on very rough surfaces (eg. cobbles, offroad) are faster on wider tires because running sufficiently low pressures on narrow tires would risk pinch flats.

​​​​The same consideration of balancing suspension vs hysteresis losses exists for any tire width, the balance point just happens at different pressures in tires of different width as a wider tire is effectively harder at the same psi. For 26x1.6" touring slicks, I tend to go with 50-ish psi; for 23s I prefer around 110 psi.






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subgrade

Another vote vor Conti Speed Rides. Recently replaced my worn out Schwalbe CX Comps 38c with Speed Rides. The SR actually measure 38mm wide on 19mm rims, but it's still a bit wider than the CX Comps sat; I reckon those were actually about 35-36mm wide. Can't say I'm much faster - rolling resistance seems to be exactly the same as (worn) CX Comps, but the ride is a bit more comfy; the tires themselves seem to be of better quality (the Schwalbes weren't perfectly round). No punctures thus far (1K miles).

As I ride streets of varying pavement quality (smooth to pothole-ridden to cobbles), also some gravel and fire roads quite often, I don't consider going below 35mm, this 38mm width being the sweet spot which lets me go pretty much anywhere, save for deep sand, and still cruise at 20mph on pavement.

cyccommute 

Well put. Hysteresis is a very large part of rolling resistance. Much...far too much...to do is made about tires bouncing and losing forward momentum. Narrow tires run at very low pressures may feel comfortable but the rider is losing more energy to the tire bounce (hysteresis) than they would if they were running very hard tires that might bounce off the occasional rough spot. While overinflation is a problem on very rough surfaces, it is much less of an issue on smooth pavement. It might make the difference between 1st and 2nd place in a race but for everyday riding, it’s far less of an issue. On rough roads, it becomes something of an issue but there is a balance to be made between comfort and rim protection. A pinch flat is a symptom of the tire being underinflated and allowing the rim to contact the pavement. It’s telling you to put more air in the tire. Tubeless tires may not pinch flat (tires can still suffer cuts) but that doesn’t mean that the rim isn’t hitting the ground on big impacts. It’s kind of the bicycle equivalent of turning up the radio. This wheel, for example, was heavily damaged by someone running it at extremely low pressures

Untitled by Stuart Black, on Flickr

That’s a $300 to $500 wheel that was essentially turned into junk because the rider failed to understand that tires need enough air to keep from being beat to pieces on the rocks.

​​​​Those are in the range that I use. I might go a little higher on the wider tires and just a little lower on the narrow tires but I haven’t had a pinch flat or bent rim on a bike in more than 30 years of rigid mountain biking, suspended mountain biking, pothole riding, curb hopping and curb dropping...even on 23mm tires (for the last 2).

To me, there is more of an issue with underinflation than with overinflation. If the tires are overinflated, I can adjust with riding style by keeping my arms and legs loose and flexible and by hovering over the saddle. That’s just my riding style anyway. Underinflated tires feel squishy, bouncy, and corner poorly in my opinion and experience...just like the flat tires they are.

cxwrench

I'm talking about 'properly' inflated tires, not 'under' inflated. I don't like squishy tires either but I'm not going sacrifice ride quality and traction to avoid a maybe once a year pinch flat. Nor will I use higher pressure than what I would like to avoid rim damage. AFAIC that means the rider needs bigger tires/more air volume. Same as you I've been doing this for decades and not had a problem. Like you I can't remember the last time I had a pinch flat.

HTupolev

Overinflation is a problem even on very smooth roads. For example, on new rolled asphalt, the study described in this article measured a 190lb bike+rider on 25mm GP4000 tires as having an optimal point of 110PSI, but being faster at 60PSI than at 120PSI.

cyccommute 

The point of that article seems to be that there is an optimal point. Not too many people are really going to 120 psi on a 25 mm tire. Far more people are currently running 60 psi in that narrow a tire.

cyccommute 

A 33 mm tire inflated to “barely half of [40 psi]” is seriously under inflated. I don’t use “high pressure” on wide tires. I use the proper pressure. If you use 20psi on 33 mm tires, what pressure am I supposed to use for 2.1” tires (55mm)? Half of what you use for a 33mm? 10 psi?! Really? That’s a flat tire

gorillimo

I used a gauge when I first mounted the tires Since then, go by feel. Running Conti Speed Rides. 42cm.

Had no problems, other than putting too much air in here wanting to soften them mid ride. No going back, they ride really well, good traction, no flats. What else could I ask for?

cxwrench

I guess you're not familiar w/ cyclocross? At 165lbs I used 22-23 rear and 19-21 front all the time. Katie F'n Compton is around 140lbs and is always in the teens...17-19psi. Do some research. I run 18-20 front and 20-22 rear on 2.6" mtb tires. No dents in my rims. If I inflated to over 30psi I'd be sliding all over the place.

cyccommute 

I have done research in addition to having decades of practical experience with regards to tire pressure...I couldn’t care less about cyclocross or any competition, for that matter. All the research I’ve done on mountain bike pressures and road bike pressures fall in the range of what I use for mountain bike riding and for road bike riding...and have used for decades without having the benefit of the calculators...with a 2.1” tire. I don’t have any bikes that can take a 2.6” tire nor would I even use one that wide if the frames could take them.

For my weight and my riding style, around 40 psi is just right for the pressure I use for mountain biking. 80 to 110 psi is right for road tires, depending on the width of tire.

Assuming that you are talking about mountain bike tires, I’m not sure what you are doing but higher pressure doesn’t result in “sliding all of the place” in my experience. Higher pressure makes mountain bike tires bounce a whole lot but it doesn’t cause them to slide out.

cxwrench

I'm really beginning to wonder about all of your experience if you don't understand that lower pressure gives better traction off road...as well as on road. It's not a difficult concept to grasp for most people. I'll leave it at that.

cyccommute 

I run lower pressure off-road. 40 psi is lower than 80 to 100 psi that I use on road tires. I just don’t run stupidly low pressures. 20 psi for my weight would result in either pinch flats, bent rims or both. 20 psi with tubes would result in tire creep as well.

In my experience, “traction” doesn’t necessarily mean that the tires slide out from underneath me. They may spin out but, honestly, that’s never be much of a problem and is more related to the tread for off-road use than the pressure.

To mirror your wonder, I wonder about your experience if you can’t grasp the idea that very low pressure risk damage to rims and tires. Two can play at that game.

Cacti

Since this is a tire thread I was wondering if someone can answer a newbie question for me

I ordered a Gravity basecamp LTD27 MTB and it should be here soon and I want to buy a couple of spare innertubes. However, I'm not sure whether the stand pump I have is a Schrader or Presta valves. I also can't find from the website tire description what type of valve the bike comes with

The Schrader looks bigger and I can't tell from pictures just how wide it is, but it looks like it might be too big for my foot pump. Whereas, the Presta valve images that I've seen look more like what I had as a kid. Narrow and skinny

Is there any way I can find out what type of valves the tires on the MTB I ordered come with? If not, what is the most standard valve for a MTB with 27.5" tires?

Sorry to hijcak the thread, but would really appreciate any help

cyccommute 

From the picture on Bikes Direct, they are Schrader. That may not guarantee that the bike comes with are Schrader but I suspect that is the likely configuration.

frogman

Exactly !!!!!

Cacti

Thanks you. From what I understand Schrader is more common than Presta, so guess I think Schrader is more likely

I guess what I really want to know is if anyone can tell me if this pump is a Schrader or Presta valve

ofajen

Oh this would be a hoot. I should get some new 23s or 25s for my old tubular wheels and run them on my cheap, old Schwinn with the touring bars. That’s gotta violate just about every C & V law ever. And it would rock!

Otto

frogman

Yes it would !! Just don't post it on BF unless you wear your asbestos fire suit, you would be flamed for sure !

cxwrench

Schrader.

cyccommute 

Agree. It’s easy enough to get an adapter for Presta from SKS if the bike happens to come with Presta, however.