5-10 PSI makes a WORLD of difference

[weisan]

Who would have thought that a paltry 5-10 PSI difference in tire pressure could transform a ride completely...but it did. I mean, I sort of already know this based off past experience but this morning group ride made it even clearer to me. I discovered late after we started our ride from the parking lot that my rear tire was running a bit low on air and I can feel it when we crossed the cattle guard just a few hundred yards down the road. That's when I remembered I had a flat in our last ride during the week and it was inflated using the frame pump with just enough pressure to continue and finish the ride. Normally, I would get home and finish the job with a floor pump but I didn't this time. Long story short, one of the riders was lagging behind with me from the group and had forgotten about his helmet so we both went back to our cars. In haste, I pumped both front and back tires using the Joe Blow floor pump I had in my car to about 95 PSI according to the built-in dial and even then my buddy commented, "Oh no, that's not nearly enough, you should go up to at least a 100..." I told him this is more than enough for me and we should forget about this discussion and get back on the road quickly so we can catch the rest of the group. He kept quiet and did what I requested. Now normally, I don't just rely on the dial, I would do minor adjustment using my very unscientific but highly intuitive and accurate "thumb-index finger pinch test" Again, we were short on time, so I went ahead without that extra step. We rode hard for the next 30 miles or so on our own before we caught up with our group at the rest stop. The whole time my hands were getting numb and really uncomfortable with jarring vibrations that get transmitted through the front end of the bike. As soon as we got the rest stop, I adjusted my tire pressure by letting some air out on the front tire, again, using my pinch test. My friend happened to be near by and he was like, "Oh my goodness! You are letting air out!" It was like the end of the world for him...I just smiled at him and said, "Trust me, I know what I am doing..."

After which, we continued the rest of our ride for another 30 miles...and it was like day and night...heaven and hell....fried chicken and brocolli.....dr.pepper and coca cola.....HUGE contrast...BIG difference....the imbalance in the universe was corrected....my hands were happy again...except my thighs...sore and crampy...but that's a different thread.

The moral of the story?....tire pressure can change the ride dramatically. never underestimate. It's the cheapest upgrade you can find to fine-tuning your ride.

[mwynne]

Went out on a route today that I haven't touched in a good while. The highway has recently been chip-sealed (most of the other roads I follow around here are paved smooth). A little psssssh and everything was right as rain!

[weisan]

A little psssssh and everything was right as rain!

mwynne pal, thank you for chiming in, your post is so much more poetic with less words.

[stephenmarklay]

Seriously, I do think he biggest improvement in bicycle technology lately has been this trend to lower pressure. It just makes riding so much better.

[Cicli]

Seriously, I do think he biggest improvement in bicycle technology lately has been this trend to lower pressure. It just makes riding so much better.

Agreed. I am down to 70/85 on 28mm Corsas. The ride is superb.

[jghall]

and it was like day and night...heaven and hell....fried chicken and brocolli.....dr.pepper and coca cola.....HUGE contrast...BIG difference....the imbalance in the universe was corrected....my hands were happy again...except my thighs...sore and crampy...but that's a different thread.

The moral of the story?....tire pressure can change the ride dramatically. never underestimate. It's the cheapest upgrade you can find to fine-tuning your ride.

You had me up til the dr. pepper vs. coke. They're both good in my books.

Absolutely agree though. My ride buds always get bent out of shape that I'm ridding somewhere between 80-90 tops.

Would say same thing about wheels too. Had a really nice frame, but just wasn't digging it. Something was amiss. At least until changed wheels.

[weisan]

>>You had me up til the dr. pepper vs. coke. They're both good in my books.

hall pal, I am just jestin'. When I am at Costco buying their dollar-fifty hot dog + drink, I am "forced" to drink C-C (coz they don't carry Dr.P), which I do so abundantly, with the free refill and all. :D

[berserk87]

I am a 120 psi guy on my Mavic 40C wheels. I tried running 110 for a couple of weeks and had 3 pinch flats. Since going back to 120, no flats, and none prior at the same psi.

[Cicli]

I am a 120 psi guy on my Mavic 40C wheels. I tried running 110 for a couple of weeks and had 3 pinch flats. Since going back to 120, no flats, and none prior at the same psi.

Damn. Thats alot. 18mm tire?

[weisan]

Berserk pal, thanks for offering up your alternative viewpoint, it's ok, it takes all kinds....

[eddief]

She rides a Lynsky with Gatorskins inflated to at least 95psi. And she complains about getting beat up on our crappy roads. I have suggested so many times she could get by with way less psi. I have even copied her on some the semi scientific proof that comes off the internet. She will not change the inflation. So be it. I am thinking if she could fit 28 mm tires, she could probably do fine at 60psi.

[weisan]

A'int that the truth, eddie pal?!

There's not a ride that i go to without someone commenting how "low" my rear tire looked....to that i always replied..."it's super comfy, you should try it sometimes."

[Duende]

I'm riding 25mm veloflex corsas with latex tubes. For the heck of it this morning I dropped tire pressure down 5psi front and rear

I weigh over 200 and that put me at 95psi front and 90 rear.

Much smoother comfortable ride. That, great weather, and some new (to me) rock n roll chain lube made today a great riding day!



Think I'm going to stick with it for a while.

[mwynne]

I'm riding 25mm veloflex corsas with latex tubes. For the heck of it this morning I dropped tire pressure down 5psi front and rear

I weigh over 200 and that put me at 95psi front and 90 rear.

Much smoother comfortable ride. That, great weather, and some new (to me) rock n roll chain lube made today a great riding day!



Think I'm going to stick with it for a while.
I'm about 220 and run similar on my 25mm GP4000s. Sometimes a tad nervous going that low, but so far so good. Knock on wood

Sent from my Nexus 5X using Tapatalk

[rzthomas]

I went for a while without checking the PSI on my 28C Vittorias on my Allez DSW. When I finally thought to put air in, they were at 65 PSI and the ride was fantastic. No problems with pinch flats or squirming, even on the rough pavement here in suburban Chicago.

[11.4]

Jeez, Weisan, you're complaining about serious pains in your thighs and you don't mention that you're running lower tire pressures? Let's get all the relevant information out on the table, ok? Now we know why you're hurting. And that Costco Coke? You should know that Dr. Pepper is the only approved remedy for Texas summer riding.

[weisan]

Jeez, Weisan, you're complaining about serious pains in your thighs and you don't mention that you're running lower tire pressures? Let's get all the relevant information out on the table, ok? Now we know why you're hurting. And that Costco Coke? You should know that Dr. Pepper is the only approved remedy for Texas summer riding.

I am crackin' up here...love you bro!

[Seramount]

hmmm, checking tire pressure with my fingers is totally inaccurate.

on 23 mm tires, I really can't differentiate between 70 psi and 100 psi...they feel the same.

I also never experience the 'gee, wish my ride was more comfortable' thing...at 147 lbs, I kinda enjoy bombing along on 90f /100r.

[weisan]

>>hmmm, checking tire pressure with my fingers is totally inaccurate.

>>on 23 mm tires, I really can't differentiate between 70 psi and 100 psi...they feel the same.

Sera pal, it takes years and years of practice and hard work before one can get to that level...since we are such pal, I will let you in on my secret training...buy a couple of boxes of Tofu from HEB, go home and practice applying finger pressure on them just enough to create an imprint without actually breaking them up into pieces...do that for 10 years, come back and we can talk again.

>>at 147 lbs...

At that weight, tire pressures becomes moot. Add Fried chicken and Costco into your training program....PRONTO!

[Gummee]

I'll pump up my tires about 1x/week (or two sometimes) and as long as they're not close to pinching when I roll it out of the garage, I'll ride it.

I know guys that are religious about pumping up tires to X psi EVERY ride. I never have gotten that, but different strokes for different folks.

I've got a pair of 30c tubulars on my Crosshairs. They get pumped up hard. ...and I mean HARD! at 60ish psi. They're normally only at 50-55psi

M

[Frankwurst]

Started this morning with the thumb test and thought mmmm maybe alright but added air. 50 rear, 45 front set out and inside of 5 miles pulled over and said to myself, self trust the thumb it's worked for alot of years psssst things got right. That's what I get for trying to over think these things.:beer:

[Black Dog]

I'm riding 25mm veloflex corsas with latex tubes. For the heck of it this morning I dropped tire pressure down 5psi front and rear

I weigh over 200 and that put me at 95psi front and 90 rear.

Much smoother comfortable ride. That, great weather, and some new (to me) rock n roll chain lube made today a great riding day!



Think I'm going to stick with it for a while.

You should reverse the psi in your tires or drop the front more. The rear tire takes most of the load and as such you need less air in the front to match the feel of the rear.

[Duende]

Ha! You caught a typo.. I rub 95 rear and 90 front.

[Black Dog]

Ha! You caught a typo.. I rub 95 rear and 90 front.

sounds painful. :eek: :D

[smontanaro]

I ride vintage steel bikes. Aside from a couple tubular-equipped wheels which happened to come with something narrow, everything I have is 25mm or wider. I generally don't get above 80psi in the rear, even less on the wider stuff. I keep my mouth shut (but mentally roll my eyes) when I hear people in the ride group talk about pumping their tires to 115-125psi.

[soulspinner]

sounds painful. :eek: :D

:p

[thwart]

The tricky part is that everybody has become accustomed to the harder feel of higher pressure, with its vibration and firm impacts, as being what it feels like to be 'fast' on your bike.

Turns out that the only thing 'fast' about those pressures (and that feel) is how long it takes for your carpal tunnel syndrome to act up. :D

[chiasticon]

yeah on a recent group ride we were going over a rougher section of road and a club mate said "man! with an aluminum frame and tires pumped up to 120, this is a killer!" and I'm like "dude, you weigh 140ish, you need to drop at least 20 psi!" and he acted like I was speaking Chinese. oh well... :cool:

[ColonelJLloyd]

I am a 120 psi guy on my Mavic 40C wheels. I tried running 110 for a couple of weeks and had 3 pinch flats. Since going back to 120, no flats, and none prior at the same psi.

That's a crappy way to ride through life. Ignorance is bliss, I guess.

[Duende]

sounds painful. :eek: :D

My iPhone has it out for me obviously!

[SpokeValley]

yeah on a recent group ride we were going over a rougher section of road and a club mate said "man! with an aluminum frame and tires pumped up to 120, this is a killer!" and I'm like "dude, you weigh 140ish, you need to drop at least 20 psi!" and he acted like I was speaking Chinese. oh well... :cool:

This seems to be a pretty common reaction. Some of my mates are in the 120 club and won't change for anything. The local shop guys promote big pressure as well.

I run 90R, 85F , plus or minus 5 psi, subject to my whims and find the ride to be much better and performance just as good.

Dubya is right on the money.

[F150]

I'm about 220 and run similar on my 25mm GP4000s. Sometimes a tad nervous going that low, but so far so good. Knock on wood

Sent from my Nexus 5X using Tapatalk
+1. Running around 220 lbs right now due to the heat and humidity (and inability to push my chair away from the table) and never inflate my 25mm GP4000s beyond 90psi. No need, and I'm not a nimble, light in the saddle kind of rider. Often let them slide to 75psi before feeling the Pavlovian urge to jack them back up.

27 x 1 1/4" Paselas routinely ridden at 65psi w/o incident.

[mwynne]

Slightly OT, but it really does make me feel better hearing from other big riders. I definitely am trying to trim down, but will never be "light"
+1. Running around 220 lbs right now due to the heat and humidity (and inability to push my chair away from the table) and never inflate my 25mm GP4000s beyond 90psi. No need, and I'm not a nimble, light in the saddle kind of rider. Often let them slide to 75psi before feeling the Pavlovian urge to jack them back up.

27 x 1 1/4" Paselas routinely ridden at 65psi w/o incident.


Sent from my Nexus 5X using Tapatalk

[jruhlen1980]

I run road tires around 85-90; I'd like to run less but I weigh ~190 and it seems like I get more flats with lower pressure.

I ride with guys who have converted to the lower pressure gospel and I believe them, but I'm curious -- if these tests at http://www.bicyclerollingresistance.com/ are to be believed, lower pressure = higher resistance.

So as far as speed goes, why does it appear that lower tire pressure doesn't affect speed out in the real world? What's the missing factor?

[Mark McM]

I am a 120 psi guy on my Mavic 40C wheels. I tried running 110 for a couple of weeks and had 3 pinch flats. Since going back to 120, no flats, and none prior at the same psi.

If you are suffering pinch flats, than better solution would be to use wider tires.

Here is a set of blog postings from Josh Poertner at Silca, showing the relationships between tire pressure, ride comfort, rolling resistance, aerodynamics, and pinch flat resistance:

https://silca.cc/blogs/journal/118397252-tire-size-pressure-aero-comfort-rolling-resistance-and-more-part-1-how-we-got-to-now

[Mark McM]

I run road tires around 85-90; I'd like to run less but I weigh ~190 and it seems like I get more flats with lower pressure.

I ride with guys who have converted to the lower pressure gospel and I believe them, but I'm curious -- if these tests at http://www.bicyclerollingresistance.com/ are to be believed, lower pressure = higher resistance.

So as far as speed goes, why does it appear that lower tire pressure doesn't affect speed out in the real world? What's the missing factor?

The missing factor is the affect of tire pressure on shock absorption and suspension losses.

Higher tire pressures do result in lower rolling resistance losses in the tires themselves; but higher pressure also results in more transmission of vibration, which increases energy losses in the rest of the system. These energy losses due to vibration are often referred to as suspension losses. This is explained in the Josh Poertner blog posts referenced above.

[jruhlen1980]

The missing factor is the affect of tire pressure on shock absorption and suspension losses.

Higher tire pressures do result in lower rolling resistance losses in the tires themselves; but higher pressure also results in more transmission of vibration, which increases energy losses in the rest of the system. These energy losses due to vibration are often referred to as suspension losses. This is explained in the Josh Poertner blog posts referenced above.

Thanks, I haven't come across that yet, that's some great info. Makes sense.

[berserk87]

Damn. Thats alot. 18mm tire?

No - 23 mm tire. I weigh 195lbs.

I go with between 110 and 100 lbs on my other wheels.

The Mavics that I noted have a narrow rim. Seems that the threshold is 120 - below that and pinch flats galore.

[berserk87]

That's a crappy way to ride through life. Ignorance is bliss, I guess.

That is a very rude thing to say. I've ridden a lot of tires over the years, from 21mm on up. I've been riding and racing for over 25 years. I am amused that some folks think that 120 psi is ruining my life.

[Cicli]

No - 23 mm tire. I weigh 195lbs.

I go with between 110 and 100 lbs on my other wheels.

The Mavics that I noted have a narrow rim. Seems that the threshold is 120 - below that and pinch flats galore.

I am 190. Run 70f 85r on 28mm corsas. Same crappy roads as you. Fast rides with no issues. Couldnt immagine running over 100. Try some fatter tires. You will be suprised.

[berserk87]

I am 190. Run 70f 85r on 28mm corsas. Same crappy roads as you. Fast rides with no issues. Couldnt immagine running over 100. Try some fatter tires. You will be suprised.

I have no need. I never said that I had any issues riding with 120 on that wheelset.

Rode 4 hours yesterday at that pressure and lived to tell about it.

I ride 25's on 2 other sets that I have and run 100. It's no big deal either. Run what pressures suit you. I'm not trying to tell anyone else that they are wrong for running lower pressures. Just noting that lower pressures do not suit all situations.

[ripvanrando]

Went out today on 25 mm Continental GP4000 clinchers at 110 psi rear and 90 PSI front. After 4600+ miles in June riding 35 mm tires at 50-60 psi, I thought my filings would going to come out today. I really wish my racing bikes could take a 28 mm Vittoria Corsa G+ width tire. I have to get off these Contis

[oldpotatoe]

If you are suffering pinch flats, than better solution would be to use wider tires.

Here is a set of blog postings from Josh Poertner at Silca, showing the relationships between tire pressure, ride comfort, rolling resistance, aerodynamics, and pinch flat resistance:

https://silca.cc/blogs/journal/118397252-tire-size-pressure-aero-comfort-rolling-resistance-and-more-part-1-how-we-got-to-now

or tubulars...I'm .1 offa ton plus and I rarely go above 90 psi..25c tires. More often about 85..

[oldpotatoe]

or tubulars...I'm .1 offa ton plus and I rarely go above 90 psi..25c tires. More often about 85..

For right above, RIPVANRANDO..NO need to use anything more than 90 psi or so with those tires..even at your weight.

[Cicli]

I have no need. I never said that I had any issues riding with 120 on that wheelset.

Rode 4 hours yesterday at that pressure and lived to tell about it.

I ride 25's on 2 other sets that I have and run 100. It's no big deal either. Run what pressures suit you. I'm not trying to tell anyone else that they are wrong for running lower pressures. Just noting that lower pressures do not suit all situations.

Agreed. Its your ride.

[ColonelJLloyd]

That is a very rude thing to say. I've ridden a lot of tires over the years, from 21mm on up. I've been riding and racing for over 25 years. I am amused that some folks think that 120 psi is ruining my life.

It's obviously not ruining your life and I think that's great. You didn't initially say that you have used 28-32mm tires at 70-90 psi and preferred a tire at 120 psi so apologize for my presumption. I weigh more than you and have had maybe two pinch flats ever.

[ripvanrando]

For right above, RIPVANRANDO..NO need to use anything more than 90 psi or so with those tires..even at your weight.

True. Whats a handful of watts. The comfort still sucks relatively in comparison to tires with lots of volume. I was going to do some testing today but had to take a dump during the ride and postponed my evaluation. I was planning on some personal best times. I like to test myself every 5-6 weeks. 110 psi is a bit on the high side.....95 psi is more normal for me on 25 mm tires that measure more like 28 mm ones. I'm a coupe kph faster on the 25 mm compared to say 32 mm Compass tires......but what value do we place on comfort. My biggest decision these days is do I take the blue magnesium bike on 35 mm tires or do I take the black plastic bike on 25 mm tires or get really crazy and go red Cervelo.

[Llewellyn]

I switched to 75R/65F a couple of years ago and couldn't believe the difference it made to the comfort of a ride with no effect on my speed.

[Cicli]

I switched to 75R/65F a couple of years ago and couldn't believe the difference it made to the comfort of a ride with no effect on my speed.

What size tire?

[F150]

Slightly OT, but it really does make me feel better hearing from other big riders. I definitely am trying to trim down, but will never be "light"



Sent from my Nexus 5X using Tapatalk

Just checked rim widths on two 700c bikes I ride most, both less than 20mm outside width (18.6, 19.3mm). Rims on son's 2015 Roubaix about the same, 20ish. He's 6-6, 220 (or so he says), I'm 6-5. Both of us capable of bunny-hopping a No. 2 pencil. No pinch flats that I can recall.

[bikingshearer]

Low pressures don't work for everyone, just as high pressures don't work for everyone.

I weigh 275 lbs (and climb like it). I don't like the feel of a "squishy" tire on a descent - it feels like the rear tire is sliding. I also don't like feeling like I'm bottoming out on a bump, although for my size I'm pretty easy on tires and wheel parts generally.

I ride 700x25 GS4000s. I pump them up to 120 psi. They may slide to 110 psi or so if I am not religious about pumping them up, but below that I start getting that "slide" and "bottoming out" feel I dislike.

It works for me. YMMV.

[Llewellyn]

What size tire?

Conti GP4000II's, both 23 and 25mm.

[stephenmarklay]

Low pressures don't work for everyone, just as high pressures don't work for everyone.

I weigh 275 lbs (and climb like it). I don't like the feel of a "squishy" tire on a descent - it feels like the rear tire is sliding. I also don't like feeling like I'm bottoming out on a bump, although for my size I'm pretty easy on tires and wheel parts generally.

I ride 700x25 GS4000s. I pump them up to 120 psi. They may slide to 110 psi or so if I am not religious about pumping them up, but below that I start getting that "slide" and "bottoming out" feel I dislike.

It works for me. YMMV.

At your weight a slightly bigger tire would be a tad better for you. If you can do a 32 your riding experience would likely be a bit smoother.

[Joxster]

On the flip side by running your tyres soft you're reducing the life of the tyre

[Cicli]

On the flip side by running your tyres soft you're reducing the life of the tyre

????????

[shovelhd]

On the Felt I run 25mm GP4000SII with latex tubes on 27mm wide CC rims. The sweet spot pressure for me is 90/95. I can drop another 5 pounds but our roads aren't always great and that 5 pounds makes a difference if I hit a big hole. Pinch flats. It makes for a fast ride with good comfort. 150 pound rider.

On the Redline which could easily fit 35mm tires I run either 28mm Schwalbe Pro 1 or 32mm off road tires on Shimano tubeless wheels. I run the road set at 55/60. Decent speed and a couch potato ride. Great for mixed roads. With the off-road it depends on the terrain.

[smontanaro]

On the flip side by running your tyres soft you're reducing the life of the tyre

In the grand scheme of things, I'd prefer to suffer with slightly shorter tire life than numb hands. There is some evidence (https://janheine.wordpress.com/2016/06/14/suspension-losses-confirmed/) that suspension losses (all that extra vibration takes energy) are higher at higher pressures as well.

[sparky33]

On the flip side by running your tyres soft you're reducing the life of the tyre

Higher pressure focuses wear on the center-line of the tire (since the tire cannot drop to a larger contact patch) which could wear the tire more quickly, no?

[Dead Man]

I'll pump up my tires about 1x/week (or two sometimes) and as long as they're not close to pinching when I roll it out of the garage, I'll ride it.

I know guys that are religious about pumping up tires to X psi EVERY ride. I never have gotten that, but different strokes for different folks.

M

Maybe they're riding latex? If I don't fill up my 25mm Paves every ride, I'd riding at 40-60psi. Latex seems to lose 20-30psi over night.

[Duende]

Maybe they're riding latex? If I don't fill up my 25mm Paves every ride, I'd riding at 40-60psi. Latex seems to lose 20-30psi over night.

Yep, have to pump my tires pretty much every other day with latex. But I honestly can't remember the last time I got a pinch flat. So it's a trade off.

[LeadoutTrain5]

Yep, have to pump my tires pretty much every other day with latex. But I honestly can't remember the last time I got a pinch flat. So it's a trade off.

True!

[Mark McM]

On the flip side by running your tyres soft you're reducing the life of the tyre

That may be true for automobile tires, but I don't see why it would be true for bicycle tires.

Automobile tires ridden soft at high speeds develop high internal temperatures, which can break down the tire. But bicycle tires don't have enough energy to have any significant heating.

Due to large contact area and relatively deep tread, riding automobile tires soft creates a lot of tire scrub, which can speed tread wear. Bicycle tires have relatively small contact and are nearly treadles, so they have much less scrub.

I see no evidence that riding bicycle tires at low end of useful pressures will shorten tire life significantly.

[ripvanrando]

On the flip side by running your tyres soft you're reducing the life of the tyre


My front tire just went 4,600 miles at 40-50 psi and it looks like it has another 5,000 to go.

I think you have it backwards

Lower pressure increases the width of the contact patch spreading the wear out and away from the center of the tire.

[Joxster]

My front tire just went 4,600 miles at 40-50 psi and it looks like it has another 5,000 to go.

I think you have it backwards

Lower pressure increases the width of the contact patch spreading the wear out and away from the center of the tire.


The area of wear and stress is on the sidewalls, the profile of bike tyres are round, where car tyres are square. Lower pressures will start to cause cracking just off the shoulders of the tyre.

[ColonelJLloyd]

The area of wear and stress is on the sidewalls, the profile of bike tyres are round, where car tyres are square. Lower pressures will start to cause cracking just off the shoulders of the tyre.

Whether this is true or not, it is not a compelling reason for me, personally, to ride at suboptimal (for compfort, rolling resistance, etc) pressure.

[54ny77]

I hit a hole so hard while riding yesterday early morning, having completely missed it due to my sunglasses' tint and some tricky shade/sunlight/shadows on a narrow road, that both h20 bottles flew out of my king cages (which has NEVER happened), my Arundel saddle bag ripped off (which also has NEVER happened), and lo & behold I got a pinch flat. PSI was at 95lbs, which is about where I'm usually at +/- a few psi.

Sometimes, you're just S.O.L. no matter what the pressure.

Biggest bummer was a car rolled over my nice Camelback insulated bottle, and then murphy's law was that regarding my 2nd spare tube, of all things it was a 650c diameter. How that happened I'll never know, maybe a packaging error. Note to self: always check the tube size when pulling it out of box and before putting in saddlebag.

(Luckily, I managed to stay upright, was only going somewhere in the mid-high teens mph and the pinch flat was in the rear. Although it did feel like my handlebars were going to snap right off when the front end hit.)

[Dead Man]

Holy **** dude.. What tank wheel survived that?

[54ny77]

32 spoke 3x aluminum DT rims, dunno the model. Both front & rear held true, no issues knock on wood. I'm no anorexic featherweight rapha model either. Got lucky all around, basically.

Holy **** dude.. What tank wheel survived that?

[beeatnik]

Biggest bummer was a car rolled over my nice Camelback insulated bottle

Some would see that as a good thing.

[Joxster]

Whether this is true or not, it is not a compelling reason for me, personally, to ride at suboptimal (for compfort, rolling resistance, etc) pressure.

That's why tyre companies give a 90-120psi on tyres and not just 110. Body weight, carrying etc will alter the weight on the tyre and life expectancy. With the profile of a bike tyre they're designed to go with the curvature when you corner, if you're running a tyre at 65psi when the recommendation is 90psi the stress is on the outer wall where the inner wall compresses but it's not designed to do that. Tubeless is designed that way as they have two skins on the sidewall.

Does any of this make sense?? It's been a stressful day

[ColonelJLloyd]

Does any of this make sense?? It's been a stressful day

Sure. I'm just saying I don't put much stock in psi ratings for tires I ride myself. I assume those ratings are required by their lawyers as much as anything. What I'm saying is that in my priority matrix, tire wear/longevity is not as high as comfort.

And, yeah, I went for a ride last night on road tubeless 40f/45r. Granted, the tires measure out at 44.5mm, which would leave a lot of people on this forum scratching their head for road use, but damn. Damn. It was awesome. Looking forward to more of that.

[DrSpoke]

Personally, I just laugh at all of these threads on tire pressures. The threads pop up frequently and are all about the same and just go round and round and round with little useful information. Some say "this is what I use" even if the weights, tires sizes or riding styles, road condition, etc. are completely different. Or "just go by feel" which is rather subjective at best and may not work for many especially newer cyclists. Or go by what's recommended pressures on the sidewall which I find to be particular useless as it's sort of a "one size fits all" solution.

As for me, I prefer something a bit more objective. For the sake of conversation (ok, debate or argument) let's say there is one optimal (correct or best) pressure for each of us riders on any given bike for any given tire size on any given day. This would take into account weather, road or trail conditions, tire type (tubed, tubeless, tubular), suspension or no suspension, rim width, rim material, tire diameter variations as compared to stated width, personal preferences, etc. The question then is how to arrive at the correct pressure.

For the past year or so I've been using the 15% drop method as originally developed by Frank Berto and promoted by Jan Heine at Bicycle Quarterly: http://www.bikequarterly.com/images/TireDrop.pdf As I understand it, the recommended pressures are at the psi where there is some sidewall flex resulting in both ride comfort and increased traction but not so low as to increase rolling resistance.

This chart utilizes 2 factors to set tire pressure which are weight (over each tire) and tire size. I have more than a few bikes including 2 road bikes, carbon and steel, a full suspension 29er mountain bike and 2 adventure bikes, carbon and steel. Tire sizes include 23, 25, 28, 30, 35, 38, 40, 57 & 60. Accordingly, I found the graph to be somewhat limiting. With a little internet surfing, I was able to find a formula which I believe is what was used in the graph. I used it to set up a spreadsheet in which I utilize columns for the various bikes and tire sizes and can change some of the variables - my weight mostly but also tire sizes as necessary. Also, I have, for now, used an estimate for weight distribution which is 45% front / 55% rear. I found the results to be eye opening. I discovered that relatively small changes in weight can have a large effect on recommended psi. And that the front to rear pressure differential was much larger than I had been using. I had been using a 5 psi differential and the chart recommended up to 20 psi difference for the smaller tires on road bikes and 10 psi on my mountain bike. I discovered I had been running much too high pressures on my mountain bike and maybe a little low on my road bikes especially in the rear. I'll admit though that I developed the spreadsheet for my adventure bikes as I had no idea at what pressures to run the various size tires that I planned to use - between 28 & 42. And being able to print the spreadsheet sure saves me from trying to remember everything too. That said, the pressures are still a starting point, albeit a great one, that I adjust slightly up or down based on my expectations for that day's ride.

So here it is - the formula: (153.6*w)/(d^1.5785)-7.1685 where w = weight in lbs (over each tire) and d = diameter in mm of each tire.

Try it - you might find it quite useful as a starting point if not eye opening. If anyone would like a copy of the spreadsheet please send me a request via PM including your email address as I don't think I can attach it to this post.

[Mark McM]

That's why tyre companies give a 90-120psi on tyres and not just 110. Body weight, carrying etc will alter the weight on the tyre and life expectancy. With the profile of a bike tyre they're designed to go with the curvature when you corner, if you're running a tyre at 65psi when the recommendation is 90psi the stress is on the outer wall where the inner wall compresses but it's not designed to do that. Tubeless is designed that way as they have two skins on the sidewall.

Does any of this make sense?? It's been a stressful day

Do you think that tire companies really put that kind of testing and analysis into psi range numbers? I doubt it. It is more likely that they just grab some numbers that seemed like they kinda-sorta worked in the past. Just like they do with things like spoke tensions, torque specs., maximum extensions, etc.

Automobiles tire pressure recommendations are never printed on the tires themselves. There are too many variables for each application for the tire manufacturers to know what the correct pressure should be. Instead, the tires pressure specs. are printed in the manual for that specific vehicle (and often on a placard on the vehicle itself).

[KidWok]

As for me, I prefer something a bit more objective. For the sake of conversation (ok, debate or argument) let's say there is one optimal (correct or best) pressure for each of us riders on any given bike for any given tire size on any given day. This would take into account weather, road or trail conditions, tire type (tubed, tubeless, tubular), suspension or no suspension, rim width, rim material, tire diameter variations as compared to stated width, personal preferences, etc. The question then is how to arrive at the correct pressure.

For the past year or so I've been using the 15% drop method as originally developed by Frank Berto and promoted by Jan Heine at Bicycle Quarterly: http://www.bikequarterly.com/images/TireDrop.pdf As I understand it, the recommended pressures are at the psi where there is some sidewall flex resulting in both ride comfort and increased traction but not so low as to increase rolling resistance.



My unscientific approach has me arriving at the same conclusion independent of BQ. I was riding 25-28's well before it was socially acceptable to do so. For road bikes, I would look for an observable 10-20% spread of the tire width (depending on road conditions and specific to road tires 23-25mm wide), which would be similar to BQ's "drop". Larger tires allow for higher percentage spread. I've been a cycling mentor and ride leader since 2007 and get the question of how much PSI needs to be in the tires from people of all shapes and sizes. The consistent answer I give is to look for spread and not focus on what is recommended on the sidewall. At 6'2" and just under 200lbs, most people are surprised to learn that I'm often using tire pressures at or below the minimum recommended pressures.

I also recommend that the front tire should be ~20% less PSI than the rear tire, assuming the bike is not loaded with anything more than the rider. In my experience, that results in a consistent spread front and rear, with both tires also having similar road feel.

Tai

[DrSpoke]

It sounds like you have used some thoughtful analysis. And it seems we've ended up in about the same place. I think your 20% differential is about right too at least for road bikes. My mtn bike pressures are at 16f & 24r so that's a bit larger % though some (most?) is due to a slightly larger tire in front.

I like the chart to help other riders who often come to me for advice. I find it much more accurate than to guess, tell them what I use or to figure it out for themselves. As an example a female friend at about 120 lbs was running her road tires at about 120 psi which is about 40 psi too high in the rear and about 55 psi in the front. And then she put on some Open Paves @ 27c and was wondering what pressure to run. So I just drop in the weights and tire sizes and can come pretty close if not exact for just about anyone.

[Joxster]

Do you think that tire companies really put that kind of testing and analysis into psi range numbers? I doubt it. It is more likely that they just grab some numbers that seemed like they kinda-sorta worked in the past. Just like they do with things like spoke tensions, torque specs., maximum extensions etc.

I think you'd be surprised how in depth they do go, I had the pleasure (misfortune because it was bloody hard work) of product development/testing with Continental on a new range of tyres and it went down to psi/temp variations/watts/distortions and the usual rolling resistance which is a variable depending on how often you brake and is it raining or not. After 12wks I drank more and my brain dribbled out my ears

[ripvanrando]

The area of wear and stress is on the sidewalls, the profile of bike tyres are round, where car tyres are square. Lower pressures will start to cause cracking just off the shoulders of the tyre.

I have never observed cracking off the shoulders of my bike tires.

The front tire mentioned is only spec'd for a maximum pressure of 90 psi. I ran it 40-50 psi on the front

From my observation and it could be wrong, high tire pressure (say 120 pis) vs low tire pressure (say 80-90 psi) on 25mm tires results in increase wear of the tread. I ride on chip sealed roads.