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Tire Pressure Recommendations?

Old 10-23-20, 10:02 AM
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stubert58
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Tire Pressure Recommendations?

I'm riding a Trek 520 Disc with stock Bontrager H1 Hard-case Ultimate, 700x38c tires. The inscription on the tires recommends inflating to 60-90 PSI. I'm 6' ~220 pounds, and riding with no load. So my questions are:
  1. What are the variables that determine what pressure you should inflate tires to?
  2. I've read in a few places that the front tire should be ~10 PSI less than back, what is the reasoning for that, and do you recommend doing it?
  3. Pressure recommendations for my situation?
Thanks!
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Old 10-23-20, 10:04 AM
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How smooth are the roads?

Your Choice for your Comfort.
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Old 10-23-20, 10:06 AM
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Normal US vehicle roads, averaging ~13-14MPH.
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Old 10-23-20, 10:30 AM
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Originally Posted by stubert58
  1. I've read in a few places that the front tire should be ~10 PSI less than back, what is the reasoning for that, and do you recommend doing it?
The reasoning is that majority of your weight is on the rear tire during most riding. The rear tire has something like 60% of the load, so having the front tire lower means that tire is more compliant and doesn't beat you up as much. In principle, you would want the front at about 2/3rd the pressure of the rear (for static riding).
During aggressive braking, your weight shifts significantly forward, so if the front tire pressure is too low, it will wallow and handling suffers. So there's a trade-off between static riding comfort and aggressive handling.
Personally, I run my front about 15% lower than the rear, but I tend to ride fairly aggressively on most bikes. You can experiment by lowering the front pressure in 5 psi increments.
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Old 10-23-20, 10:47 AM
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Several years ago someone suggested a 15 percent tire drop theory:
https://www.adventurecycling.org/def...SIRX_Heine.pdf

That theory fails on really wide tires like 2 inches or wider, but in general terms for touring I have used pressures in that range for 35 or 37mm wide tires for the rear tire.

Note that it is weight on each tire, not total weight. I do not follow that theory for the front tire, I think that gives too low a pressure. Instead I usually run a front tire at about 70 to 75 percent of the pressure that I have in back.

That said, on a really rough pavement if I have a lot of vibration on my hands and handlebars, I will run lower pressure on the front to smooth that out.

If I have a tire that has a very stiff sidewall or tread, I might increase the pressure a bit to make the tire deform less, because deforming a very stiff tire is lost energy, some tires are slower than others.

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Old 10-23-20, 10:48 AM
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Here is a page with some calculators. Remember, these use the weight on each wheel individually, not the total weight of the bike and rider. It is the weight on the wheel which generally isn't equal distributed between the front and back. The results are a good guideline, and you can adjust to your preferences from there.

Bicycle tire pressure calculator
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Old 10-23-20, 11:16 AM
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I run Panaracer 700x38 GraveKing slicks on a couple bikes(try them..I think they'll roll better than the Hardcases) that are rated at 75psi max (tubed). I ride them at 65 in front and about 70 in the back..no issues..been doing it for a few years. Nice, fast, comfy tires. I weigh about what you do.

My GF rides the same tires at around 55-60 pounds and loves them.
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Old 10-23-20, 11:20 AM
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Originally Posted by stubert58
I'm riding a Trek 520 Disc with stock Bontrager H1 Hard-case Ultimate, 700x38c tires. The inscription on the tires recommends inflating to 60-90 PSI. I'm 6' ~220 pounds, and riding with no load. So my questions are:
  1. What are the variables that determine what pressure you should inflate tires to?
  2. I've read in a few places that the front tire should be ~10 PSI less than back, what is the reasoning for that, and do you recommend doing it?
  3. Pressure recommendations for my situation?
Thanks!
Stubert, I have exact same bike and tires. I've been riding 50 psi front, 55 psi rear recently. I am lighter though at 170lbs.

That's apparently below the recommendation on the tire label but it has worked well for me. Comfortable but still fast.
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Old 10-23-20, 11:58 AM
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Originally Posted by stubert58
Normal US vehicle roads
No such thing.
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Old 10-23-20, 01:26 PM
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imi
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This is going to sound a bit primitive after reading the above posts, but I pump my tires to the max recommended on the sidewall ’cos I like to feel every bump and grain (and it feels like I’m going faster, haha)
I let out 1 bar on chipseal, towpaths etc, and sometimes just leave it at that for asphalt too, so my go to is:

Gator Hardshells 32mm, 7 bar.


... back to the techy discussion!
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Old 10-23-20, 11:23 PM
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I say pump it till it pops and then back off a few PSI...LOL

I usually keep front and rear pretty close, I just do it that way and probably won't really stop unless riding a fat bike or something. The reason for doing that is you are putting more weight on the rear tire so you want more pressure there where as the front tire is a lot less loaded and can handle less pressure.

I would experiment by going closer to the higher end of the range and backing off a couple PSI till you hit pay dirt. There aren't really any hard fast rules to this some people like 'em hard and some like 'em soft. I don't mind a tire at higher pressure as a heavier rider.
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Old 10-24-20, 05:18 AM
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I weigh 220, on 35mm tires I've been running 70 PSI on my road bike - that is what I ran on my old Trek 520, too, when that was my road bike. So, I might run a bit lower on 38mm.

For crushed stone/rail trail kind of riding, I've left on the 40MM tires that came with that bike (Jamis) and run them at 55 psi.

Lots of good science that shows higher PSI not faster - you can play around and see if you notice any difference going lower, I did not. None of these pressures on wider rims are low enough to increase likelihood of pinch flats and seem to reduce normal puncture flats for me.

For no particularly good reason, I run the same PSI front and rear. I think years ago I convinced myself that the only flats I seemed to get on the front are slow leak kind of deals and I rather have a few PSI margin.
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Old 10-24-20, 06:04 AM
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Originally Posted by 10 Wheels
How smooth are the roads?

Your Choice for your Comfort.
chuckle, Mr 10 wheels, I counter and raise your chipseal with this sucker.

​​​​​​​
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Old 10-24-20, 06:08 AM
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You need to Move.
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Old 10-24-20, 06:20 AM
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Originally Posted by gsa103
The reasoning is that majority of your weight is on the rear tire during most riding. The rear tire has something like 60% of the load, so having the front tire lower means that tire is more compliant and doesn't beat you up as much. In principle, you would want the front at about 2/3rd the pressure of the rear (for static riding).
During aggressive braking, your weight shifts significantly forward, so if the front tire pressure is too low, it will wallow and handling suffers. So there's a trade-off between static riding comfort and aggressive handling.
Personally, I run my front about 15% lower than the rear, but I tend to ride fairly aggressively on most bikes. You can experiment by lowering the front pressure in 5 psi increments.
to the fellow asking the question"--- this pretty much sums it up. I weigh a good 80lbs less than you so my pressures have no connection to yours and I haven't a clue, but lower front pressures are standard procedure.
if you don't have one, but yourself a floor pump with gauge, and start trying different pressures.
Proper pressures , not too high, will be more comfortable and faster for a wide variety of road surfaces.

I commute all the time and for years have done pressure tests over a repeating route, and it's proven to me that proper lower pressures are as fast or faster, and way more comfortable than max pressures, while putting out the same power.
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Old 10-24-20, 06:25 AM
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Originally Posted by 10 Wheels
You need to Move.
that made me smile.
around where I live in Canada, it's pretty rare to have chipseal.
this was in Mexico , where I was really glad of my 2in tires and their cushy goodness on days like that. Seriously glad.
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Old 10-24-20, 06:28 AM
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Never rode in Mexico. Thanks for your pic.. Think I will copy it.
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Old 10-24-20, 06:44 AM
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I am 220lbs and I am running Schwalbe Marathon Plus Tires 700c x 38 @ 70psi front and 80psi rear for some 5000+ miles this summer they are showing excellent wear and providing great handling.
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Old 10-24-20, 04:20 PM
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Originally Posted by 10 Wheels
Never rode in Mexico. Thanks for your pic.. Think I will copy it.
copy it but get in touch if you want to use it anywhere officialesque.
it was middle of nowhere Mexico, and went on for a surprisingly long period. You sure as heck wouldnt want to fall on it. Gave me the shivers just thinking about that the whole time riding along that road. Must have been rough on my tires.
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Old 10-25-20, 09:09 AM
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Originally Posted by djb
chuckle, Mr 10 wheels, I counter and raise your chipseal with this sucker.
That looks rougher than the chip seal I rode on in West Texas, but not by much.

I was on a week long van supported tour, all we had to carry on our bikes each day was our water and lunch, van hauled the camping gear.

I had my folding bike with 40mm wide Marathon tires. First day between 75 and 80 psi in rear, between 55 and 60 in front. My hands really took a beating from that rough chip seal, my GPS was not happy either and my GPS still has occasional problems from that day of vibration. Day two, kept my rear tire at the same pressure but dropped my front tire to between 40 and 45 psi, my hands and GPS were much happier. And that was enough pressure in a 40mm wide tire to prevent pinch flats. If it slowed me down any, I did not notice as the other riders that were slower than me were still slower than me.

Pavement like that is one reason that the narrowest tires I tour on are 37mm if on a 700c bike and 40mm if on a 26 inch bike.

Photo is some of the chip seal on the road into the Florida Everglades, and one of the road hazards.


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Old 10-25-20, 12:56 PM
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man o man, this one was handed out on a silver platter---------------------------------------
Tmsn, come on dude, to avoid any problems riding in that part of Florida is easy, all one has to do is use Conti Gatorskins.

badump bump, and yes, I'll keep my day job.
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Old 10-25-20, 04:14 PM
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tire pressure

Michelin had some data that that stated tire pressure should be increased toward the upper end of the rating as the weight of the rider increases. The front tire will have more traction with a slightly lower pressure and the rear tire carrys most of the weight of the rider.
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Old 10-25-20, 04:53 PM
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Originally Posted by vjbknife
Michelin had some data that that stated tire pressure should be increased toward the upper end of the rating as the weight of the rider increases. The front tire will have more traction with a slightly lower pressure and the rear tire carrys most of the weight of the rider.
LOL, well if it wasn't coming from a huge tyre company, I'd never have guessed that more weight would need more pressure for a given tyre. They must be Jedis. Or at least rocket scientists.
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Old 10-25-20, 05:55 PM
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Originally Posted by djb
...Conti Gatorskins.
...
Got it.
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Old 10-25-20, 09:50 PM
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surprisingly enough

Originally Posted by CargoDane
LOL, well if it wasn't coming from a huge tyre company, I'd never have guessed that more weight would need more pressure for a given tyre. They must be Jedis. Or at least rocket scientists.
You would be surprised how many people do not have any idea about this. And not that many other tire companies put out charts with this info that I have seen. They could be Jedi Rocket surgeons.
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