5-10 PSI makes a WORLD of difference - Page 3

SpokeValley · #31 07-25-2016, 12:29 PM

Quote:

Originally Posted by 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...

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 · #32 07-25-2016, 12:52 PM

Quote:

Originally Posted by mwynne

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 · #33 07-25-2016, 12:54 PM

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"

Quote:

Originally Posted by F150

+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 · #34 07-25-2016, 01:10 PM

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 · #35 07-25-2016, 01:19 PM

Quote:

Originally Posted by 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.

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/11839...-we-got-to-now

Mark McM · #36 07-25-2016, 01:27 PM

Quote:

Originally Posted by 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?

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 · #37 07-25-2016, 01:38 PM

Quote:

Originally Posted by Mark McM

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 · #38 07-25-2016, 04:57 PM

Quote:

Originally Posted by Tihsepa

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 · #39 07-25-2016, 04:59 PM

Quote:

Originally Posted by ColonelJLloyd

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 · #40 07-25-2016, 05:00 PM

Quote:

Originally Posted by berserk87

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 · #41 07-25-2016, 05:06 PM

Quote:

Originally Posted by Tihsepa

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 · #42 07-25-2016, 05:34 PM

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 · #43 07-25-2016, 05:41 PM

Quote:

Originally Posted by Mark McM

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/11839...-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 · #44 07-25-2016, 05:42 PM

Quote:

Originally Posted by 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 · #45 07-25-2016, 05:45 PM

Quote:

Originally Posted by berserk87

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.