Symox

I have foldable Continental Gatorskins (I happen to love 'em but I'm sure there may be better options) in 700x28. Someone on this forum suggested running tires at a lower pressure to help with downhill riding. This suggestion literally changed my confidence in descents. I was running 23s at max pressure and the bike always felt glitchy and on the verge of losing control. With the 28s running at 80 psi it feels like a totally different bike - for the better!

The Continental website says 95-116 is the range for this particular tire. I weigh 155 lbs and haven't experienced pinch flat (knock on wood) with 80psi. I only ride on tarmac roads (no gravel) but there are occasional potholes that I do my best to avoid. Should I be concerned about running at this low a pressure? These are NOT the hardshell versions btw.

Thanks for your insight

Branko D

It's fine. Lots of people run 28s at 80-ish psi. At your weight I wouldn't worry about pinch flats on 28s at that pressure.

28s at 80 psi are about the equivalent to running 23s at 90-95 psi in terms of suspension, huge difference from running 23s at max pressure.

Symox

thanks so much for your help! Good to know others ride 28s at this psi

datlas 

Agree. I would suggest drop to 75F and 80-85R, but tweak to your conditions.

burnthesheep

IMO 155lbs and 80psi on a 28mm tire is still WAY too much. Depending on your rim width. Either way, I would think for that size tire and your weight a 28mm you'd be down around 60-65 psi.

I run the wide road width HED wheels and run the front 23mm at like 82 and the rear 25mm at 72 or so.

For your weight, even for a narrow width rim, you wouldn't need to run those 23's at max pressure. Maybe 85psi.

If the 28's fit fine, keep running them. But, I think you would have been fine airing down on anything if you weigh only 155 and were at "max".

Ninja edit: I weigh 160, to qualify the similarity to your size and give those pressures.

MoAlpha

I agree with the above, but if one were to be pedantic they would ask about the internal diameter of your rims, since that has a significant effect on effective tire volume. I weigh in the low 140s and currently ride 25 mm tires on 18 and 21 mm internal dia. rims at 75/70 and 70/65, respectively, with no problems.

Symox

Several have mentioned rim width. I’m using Mavic Open Pros which have an outer width of 19.6mm. Inner width is 15mm according to web search

MoAlpha

Narrow, so recommended pressure would be on the high side, but per above, you're fine.

mdarnton

I weigh 170 and was running 28s at 75 front, 65 rear all last summer, no problem. That's for big-city street. Previously I ran 90, but the new plan rides a LOT smoother!

DaveSSS 

ZIPP has a pressure calculator for tubeless tires on their website. https://axs.sram.com/guides/tire/pressure
Silca has one too. https://info.silca.cc/silca-professi...ure-calculator

Unfortunately, pump gauges can be quite inaccurate. My old silca pump was reading about 8 psi higher than a calibrated reference gauge, so my actual tire pressure was a lot lower than I thought it to be. Without an accurate gage, a pressure calculator isn't valuable.

datlas 

OP not running tubeless.

Common newbie and not-so-newbie mistake is to pump up tires high. One of my friends is riding 28mm at 110PSI. I suggested he might want to drop his pressures and he gave me a look like I was crazy. And this is a long-standing "serious" cyclist.

merlinextraligh

Our tandem team weighs more than twice the OP, and the Silca calculator only recommends 87 psi for 28mm on the tandem.

Basically, for optimal comfort and reasonable rolling resistance, you want to run pretty much the lowest pressure you can. The limits on going too low, are 1), as noted pinch flats, and 2) the tire squirming. If you’re not getting pinch flats, and the tire doesn’t squirm as you corner, then in all likelihood your pressure isn’t too low.

You can get more scientific, calculate the pressure that gives you the “ideal” amount of drop, research rolling resistance for your tire with various combinations of rider weight and pressure. But if the bike rides well, doesn’t squirm and doesn’t pinch flat, you really don’t need to sweat it further.

DaveSSS 

The silca calculator doesn't specify tubed or tubeless, but the recommended pressure is a lot higher than the zipp tubeless, so it must be for tubed tires.

Carbonfiberboy 

I'm going to go the other way and say *definitely* abide by the manufacturer's pressure recommendations. If it says 95, run 95. There was a guy over on the tandem forum who blew his tires doing exactly this, running 80 on these tires. The rims apparently wore through the sidewalls and the bead separated from the sidewall, right at the edge of the rim. Those recs are for a reason. We many not know what it is, but best to abide by it.

BTW, IME a 28mm tire on a Open Pro rim is not a good choice for superior cornering, though fine on a wide rim. On Open Pro rims, 23mm Conti 4000IIs or 5000 are the best modern tires for fast descending. At 155 lbs. on my recced tires, run 80 front, 100 rear. I checked my stock of Conti 5000 tires, and neither the 23 nor the 28 show a minimum pressure in the sidewall. That's interesting.

Further along that line of interesting things is that the Conti website no long shows a minimum pressure for any tire, at least not that I could find, contrary to the OP. Is no minimum pressure now a thing for bike tires? All tires used to have a range on the sidewall.

billridesbikes

I have 28mm on my road bike. I like 75psi front and 80psi rear if the roads are nice and smooth, and if I expect lots of rough chip seal or gravel maybe a little lower 70F/75R. I’m 150lbs and this seems to work for me although some charts say I should run lower. I have never gotten a pinch flat with this configuration (~10,000 miles).

burnthesheep

Don't run out and buy stuff just because BF mentions something, but going a bit more volume in the rim however you achieve that (usually wider rim) it makes a difference.

I used to run 23/25 combo on my Propel with the original narrower PSLR aero wheels. Good wheels with DT hubs, but I wanted lower psi and more comfort. I bought some HED 6+ and running the same 23/25 combo was able to go down over 10psi less. Plus the volume in general felt nicer. As soon as I stop being lazy and install my new TT tires on the disc/deep front for that bike, the GP5000 25mm that's on the back of those will replace the 23 on the front HED 6+ wheel for a little more comfort and a hair of CRR gain.

Even if you can find some cheaper wheels with more volume/width........it makes larger tires feel even better.

HTupolev

Neither do Gatorskins. But there is a minimum PSI on the box. For 23 GP5000, Continental specs a minimum PSI of 110.



They usually are not, or at least not any reason based on anything that the user has any reason to care about. For example, previous-gen Vittoria tires had very high pressure minimums that were based on meeting ETRTO drop requirements when a bicycle was as heavily-loaded as Vittoria could imagine a bicycle being. Like, the logic was literally "you need to pump 100PSI into your 27mm tires because, if you use less than that and a tall morbidly obese guy sneaks up and rides off with your bicycle, the amount that the tires are deforming underneath him might be in violation of ETRTO specifications."

From a safety standpoint, what can go wrong with low pressure is if the tire doesn't manage to seat properly (which is so rim-and-setup-dependent that a single PSI number is useless), or if the tires are being run at such extreme drop that the amount of deformation is chewing up the casing (which is totally load-dependent and, for 28mm tires under a 155lb rider like the OP, would tend to involve massively less than the 80PSI they're looking at).

datlas 

Are you sure those lower PSI numbers on the CONTI box are MINIMUM or maybe just "recommended?" I see where it says MAX for the maximum but I don't see MIN anywhere.

HTupolev

Good point. Continental has a page on their website with a nice straight answer.



They recommend choosing pressures higher than the recommended pressure.

Symox

Wow, you aren't kidding. Just tried 70 and then 60. Like a whole different set of tires!! I'll probably settle on 70 ish

Why do you run lower pressure in the rear?

Why am I only now finding out about this?

Sy Reene

AFAIK, there's no theoretical difference in optimal air pressure for a tubed vs TL tire, excluding the possibilities that:
1. With a tubed setup, if the ideal pressure gets to too low of a value, you may be more likely to experience a pinch flat, or
2. With a TL setup, typically rim makers specify a MAX pressure that is lower for TL than for tubed, so if for whatever reason you need a high pressure, you might be top-end limited with TL tire.

Otherwise, if you're somewhere in the middle, the 'ideal' pressure for your circumstances shouldn't vary between a TL and tubed setup.

surak

Gatorskins aren't what I consider a supple tire (if there's data to quantify this, I'll be happy to be corrected) so you won't necessarily gain much by dropping your tire pressure lower. I noticed it only felt more sluggish when I used them, one of the reasons I ditched mine quickly.

From https://www.renehersecycles.com/tire...ure-take-home/ :

Blues

Being an 185 pound older guy suffering from a lot of wear, a smooth ride is the only option or I would not be able to ride at all. I have folding 28mm Gaterskins with tubes on my R-300 Cannondale, probably the biggest tires I can fit on it. Without my body complaining, the highest pressures I am able to run on my local not-so-smooth roads are 40 psi front and 45 psi rear. I am not racing, just trying to keep in shape on these hills. I do ride regular, but I don't ride the mileages a lot of you guys do, and I have not noticed the bike being sluggish or squirrelly at all.

My ideal Geezer Road Ride has 40mm tires which I run at 35 psi front and 40 psi rear.

Someone is probably going to jump my case about my pressures, but hey, they work for me and might work for someone else. For me it's a matter of riding or not.

Fred

MoAlpha

Indeed and I believe those data exist. I was going to comment to that effect, but Gatorskins have been beat up on elsewhere here. GP 4 Seasons (?) are a much nicer compromise in terms of both ride and handling.

mdarnton

I miswrote....higher pressure in the rear! Sorry.
Yup, big difference.