Symox

I know there is no definitive answer to this but I'd like your input nonetheless...

I weigh 155lbs, bike is around 17lbs (probably less but haven't checked). I ride on tarmac only (dry or wet) and use 28mm Continental Gatorskins (yeah I know some hate 'em - I think they are fine for my needs) with Mavic Open Pro rims.

I used to ride at max pressure until reading on this very forum how lower pressures can help ride quality. Well the lower pressures certainly have. I have found that if I run 60psi on the front and 70psi on the rear I get excellent traction, comfort and no pinch flats (knock on wood). (most importantly, the bike isn't twitchy on fast downhills like it usually is at 110psi).

So, am I asking for trouble at these lowish pressures? I don't think its possible for the tire to dislodge from the rim as it is friggin' hard to remove the tires from the rim in the first place but that is one of my concerns

Thanks for your insight and/or recommendations

Badger6

You are potentially risking pinch flats, Gatorskins have a tough casing which is not very supple (but is the reason they are generally so durable), but it is unlikely you will get a roll off.

I assume they measure 28mm (outside dimension) when inflated. According to the Silca calculator (entering total weight as 170#), the starting pressures are rear at 77.5psi, and the front at 75.5. Those are starting points. I bet you could safely take 10% off those pressures, and bring them down into he low 70s, but 60 seems awful low.

HTupolev

You're probably fine in terms of tire security. Low pressures generally aren't where blow-offs occur, and rolling a loose tire is largely a phenomenon that happens after a flat.

I also don't think you're really pushing the limits in terms of sidewall damage from excessive deformation.

If you aren't suffering pinch flats, then you're probably fine.

diphthong

do people still ride '28's? asking for a friend.

Ghazmh

Wait, are we going back to 23’s?

diphthong

^hopefully not. may ye all continue to pay more for '28's since it's the cool kid and ride "faster." knock thyselves out.

eduskator

Is your setup tubeless or are you using inner tubes? If tubeless, you should be good IMO.

I am 180lbs, running 28mm TL tires on 19.4mm internal width hookless rims and I run 68PSI front & 70PSI rear (ish).

rm -rf

Pinch flats
It's a combination of speed and the shape of the rock or pothole. I've gotten a few pinch flats on downhills, hitting a large chunk of sharp edged gravel that had been kicked out onto an otherwise smooth road.
At moderate speeds, the tire would have bounced over those rocks with no problems.
Moderately deep, rounded edge potholes are way less of a problem than very deep or sharp edged potholes.

Pressures
I've since raised the tire pressure 5 or 8 psi. But I do wonder if that small change makes much difference in getting the pinch flat!
At 170 pounds, I'm running GP5000 at 65-68 front and 78-80 rear psi on 28mm tires with wider rims, 20.5 mm internal width.

More air volume in the tire allows lower pressures. So I have quite a bit more air volume than your narrow Open Pros. You could try a little more pressure on each wheel and see how it feels on rough roads, and go from there. When I raised my tire pressures to my current setup, it still had similar rough road comfort.

(It must be an amazing change if you were running 110 psi on 28s! Rock hard.)

datlas 

I think you are ok but slight risk of pinch flats. It really depends on your roads, if it were me I would go to 65-70F and 75R. But go with what works best for your situation.

WhyFi

If these pressures have worked well in practice, why worry about what others think might in theory? If they're not squirming when you corner and you're not getting that "wait... do I have a flat?" bounce when you pedal, you're probably fine.

FWIW, I run a little over 60psi on the rear and a little under 60psi up front... but I'm 30lbs heavier, have 23mm int width rims, run tubeless, have more supple tires, etc, etc. Regardless, I don't think that your 60F/70R is out of the range of sensibility.

DaveSSS 

Most tire pressure calculators only recommend 2-5 psi more for the rear. Rim internal width also matters. Last year I ran what I thought was 80 psi with 25mm tires on 17mm internal width rims and got two pinch flats from not very large rocks. I only weigh 135-140. It also turns out that my pump gauge was off and I really only had 72 psi in the tires. Gauges are often inaccurate. I now have a new 0-100 psi liquid filled gauge with a much larger face so it's easier to read.

msu2001la

I have never heard of a clincher tire coming off the rim because someone was running too low PSI. I suppose it's possible, but unless you're trying to ride a completely flat tire I don't see how this would be a common problem.

I think the only risk here is potentially more chance of pinch flatting.

eduskator

+1 on that. I tried a few combination (65F/70R, 69F/70R and 70F&R) and I'm good at 68/70. Even 70/70 is OK. My hands don't mind extra stiffness, but my arse likes it as soft as possible.

Iride01 

If you get pinch flats, then put more air in or avoid the places that make you pinch flat.

Is that the right pressure for you? Trust what your legs and data show you for the same ride, multiple times at differing PSI for six to a dozen times each.

Symox

No it is tubed foldable clincher. I'm finding 65psi front 75psi rear to be my sweet spot

cxwrench

If it works for you it works for me. I've always felt that I will run the pressure that feels good and not worry at all about pinch flats. If I get one once or twice a year so be it, but I will like my tire pressure the other 99.9% of the time.

Joearch

I am 170lbs and find that my 28’s w tubes feel good at 78r and 72f.

phrantic09

I don’t know if I’d do it in a tubed tire, but I run 60/65 on 28mm tubeless tires with 19 internal width at 170# just fine

Symox

I am finding 65psi Front and 85psi rear is working great.

Parkyy16

At your weight, and choice of tire, 65psi front and rear should be fine. I used to run 32mm gatorskins on a commuter, usually ran 65psi front and back, never had a pinch flat.

I'm running 80psi both front and rear on my 28mm on 21mm ID rims; they're about 30mm when pumped up. I've tried all variations from 60 - 90 psi front and back, found 65 front and 75 rear to be the most comfortable in most conditions, but my city is doing a lot more road work recently, so I upped the pressure a bit to prevent pinch flats and/or bottoming out my carbon rims on some pretty bad potholes caused by the construction traffic.

Currently at 165lbs, 5'9". I'm running Hutchinson Fusion 5 28mm tires with regular butyl tubes.

Kabuki12

I like 28’s and run them on a few of my bikes. I am about 155lbs and ride vintage steel bikes so some have 27” x 1” wide tires. Our roads are really bad in some places and I run 80 in the front and 95 on the back tire. I ride two to three times a week and only get a couple of flats a year from thorns. I have one bike that I run 27” x 1 1/4” Michelin ProTek but I still put 80/ 90lbs in those.

xroadcharlie

According to an online calculator you should run 60 psi front and 75 rear. But I question the logic behind lower front tire pressure with 28 mm tires that have very little room for error. The problem is when you hit a pothole or big shift on cement the full weight of the bike drives the soft front tire into the sharp edge, resulting in a pinch flat.I might run 68 psi front and 75 rear for a little extra insurance.

These are a good place to start IMO. Tires with a stiffer side wall, Like the cheap Kenda's on my comfort bike require less pressure, the more supple sidewalls on a good tire the same size may require slightly more.

With the 50mm tires on my comfort bike, I run 30 - 35 front and 40 - 47 rear. But those 50mm tires have a lot more room before a pinch flat then 28mm do.

ZHVelo

On my GP5000s I am in the low 60s (28mm). Doesn't seem to be an issue. But generally roads are good here.