Tire pressures
07-24-19, 09:46 AM
#1
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Tire pressures
hi all. I have a giant defy 3 and love it. However I never know what would be good tire pressures for me. I weigh 250 lbs. I’m running 28’s. Would love to hear some thoughts. My tires are conti’s with max pressure of 115 psi.
Thanks
Last edited by pippin65; 08-16-19 at 08:45 PM.
07-24-19, 10:19 AM
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91.87 psi.
Seriously, you can either start with 115 psi, forget to air it up for a few days, and see if you notice higher rolling resistance or pinch flats, and pump it up if you do. Or start about 90 psi, ride it, next ride try 95 psi, and settle in on a good pressure.
A "good pressure" gives you speed (actual speed, not just you feel road buzz), you feel comfortable carving turns, and you don't pinch flat. It may change with road condition (pavement smoothness and potholes).
Seriously, you can either start with 115 psi, forget to air it up for a few days, and see if you notice higher rolling resistance or pinch flats, and pump it up if you do. Or start about 90 psi, ride it, next ride try 95 psi, and settle in on a good pressure.
A "good pressure" gives you speed (actual speed, not just you feel road buzz), you feel comfortable carving turns, and you don't pinch flat. It may change with road condition (pavement smoothness and potholes).
07-24-19, 10:23 AM
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1) Does your Giant Defy 3 run harshly or are you happy with the ride as is?
2) Which specific rims are you running, how wide are they (internally and externally)?
3) Have you considered or are you running latex inner tubes or are you satisfied with butyl inner tubes?
4) Do you get a lot of flats?
5) Are you willing to monitor tire presssures before each ride?
6) What are the road surfaces that you typically ride on?
7) Are you hard or easy on your gear? For example do you plow over minor potholes or swerve a bit to find the smoothest line?
I’m running 25mm Challenge Criterium tires this year on my Velocity A23 wheels. I changed out the Velox cotton rim tape with thin 3M tubeless tape (2 layers) in order to get easier tire mounting. I think the thin tape also gives more interior volume which can allow lower tire pressures.
After riding a 2nd bike that is titanium as a backup for a year, I have now come to realize just how harsh my main aluminum bike is. This got me started on this ongoing experiment where I have been lowering tire pressures on the aluminum bike for increased grip and comfort. I weigh ~ #195 and have lowered the pressure in those 25mm Challenge tires with the Vittoria latex inner tubes to about 72psi front and 84psi rear. They are still plenty firm to where I don’t seem to have much sidewall deflection. The ride over broken pavement is much more tolerable. I highly recommend exploring a similar path for yourself. I would submit that running 115 psi in 28mm tires is WAY overkill. You could put some Vittoria latex tubes in there and even @ your body weight run them much lower in PSI than you are now. You will have to experiment to find the number that gives you the magical combination of low rolling resistance, flat protection and (wet/dry) cornering grip.
I was was going to look up the specs on a Giant Defy 3 just to see how compliant or stiff a bike it is.
But it if I were going to guess, I would think right off the top without seeing you ride or knowing what kind of roads you typically ride that 85 psi front and 92 psi rear would yield a marked improvement on your Continental 28mm tires (Grand Prix 4000’s perhaps?). If that combination was fine but the ride was still firm you could most definitely go even lower than that.
I don’t mean to be too preachy here, but personally I’m pretty stoked about this game changer for me of running slightly wider rims with more supple high thread count open tubulars with latex inner tubes and thinner tubeless rim tape at lower pressures for an amazing feel/ride - very noticeable!
Let me know about questions 1 through 7 above, good luck!
Last edited by masi61; 07-24-19 at 07:52 PM.
07-24-19, 11:24 AM
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I would start with max in the rear & let the valve burp as you release the pump (I'm a Schrader guy). I figure I lose 5 lbs w/ a burp. bike tires have very little volume so be careful how much you burp but 5-10 lbs under max would be as low as I would go to start
the front, I've found, for me, can easily be 10-15 lbs lower than the rear
the front, I've found, for me, can easily be 10-15 lbs lower than the rear
07-25-19, 03:10 AM
#5
NewKidInTown
Here's an old post from way back on the very topic . . .
https://www.bikeforums.net/road-cycl...s-tip-day.html
https://www.bikeforums.net/road-cycl...s-tip-day.html
07-26-19, 12:58 PM
#6
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Nice bike.
People like to make things complicated.
At that weight, ballpark would be around the max for good pavement. Drop it a bit for rougher roads or hard dirt.
People like to make things complicated.
At that weight, ballpark would be around the max for good pavement. Drop it a bit for rougher roads or hard dirt.
07-27-19, 08:05 AM
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It depends on quite a few factors. Could you go into a bit more detail about some things? I’m just going to shoot off some questions to get the conversation started in no particular order, OK?
1) Does your Giant Defy 3 run harshly or are you happy with the ride as is? Nice
2) Which specific rims are you running, how wide are they (internally and externally)?
Stock Rims
3) Have you considered or are you running latex inner tubes or are you satisfied with butyl inner tubes? I’m good
4) Do you get a lot of flats? Never
5) Are you willing to monitor tire presssures before each ride? You bet
6) What are the road surfaces that you typically ride on? Asphalt in Florida
7) Are you hard or easy on your gear? For example do you plow over minor potholes or swerve a bit to find the smoothest line?
Smooth smoothie
I’m running 25mm Challenge Criterium tires this year on my Velocity A23 wheels. I changed out the Velox cotton rim tape with thin 3M tubeless tape (2 layers) in order to get easier tire mounting. I think the thin tape also gives more interior volume which can allow lower tire pressures.
After riding a 2nd bike that is titanium as a backup for a year, I have now come to realize just how harsh my main aluminum bike is. This got me started on this ongoing experiment where I have been lowering tire pressures on the aluminum bike for increased grip and comfort. I weigh ~ #195 and have lowered the pressure in those 25mm Challenge tires with the Vittoria latex inner tubes to about 72psi front and 84psi rear. They are still plenty firm to where I don’t seem to have much sidewall deflection. The ride over broken pavement is much more tolerable. I highly recommend exploring a similar path for yourself. I would submit that running 115 psi in 28mm tires is WAY overkill. You could put some Vittoria latex tubes in there and even @ your body weight run them much lower in PSI than you are now. You will have to experiment to find the number that gives you the magical combination of low rolling resistance, flat protection and (wet/dry) cornering grip.
I was was going to look up the specs on a Giant Defy 3 just to see how compliant or stiff a bike it is.
But it if I were going to guess, I would think right off the top without seeing you ride or knowing what kind of roads you typically ride that 85 psi front and 92 psi rear would yield a marked improvement on your Continental 28mm tires (Grand Prix 4000’s perhaps?). If that combination was fine but the ride was still firm you could most definitely go even lower than that.
I don’t mean to be too preachy here, but personally I’m pretty stoked about this game changer for me of running slightly wider rims with more supple high thread count open tubulars with latex inner tubes and thinner tubeless rim tape at lower pressures for an amazing feel/ride - very noticeable!
Let me know about questions 1 through 7 above, good luck!
1) Does your Giant Defy 3 run harshly or are you happy with the ride as is? Nice
2) Which specific rims are you running, how wide are they (internally and externally)?
Stock Rims
3) Have you considered or are you running latex inner tubes or are you satisfied with butyl inner tubes? I’m good
4) Do you get a lot of flats? Never
5) Are you willing to monitor tire presssures before each ride? You bet
6) What are the road surfaces that you typically ride on? Asphalt in Florida
7) Are you hard or easy on your gear? For example do you plow over minor potholes or swerve a bit to find the smoothest line?
Smooth smoothie
I’m running 25mm Challenge Criterium tires this year on my Velocity A23 wheels. I changed out the Velox cotton rim tape with thin 3M tubeless tape (2 layers) in order to get easier tire mounting. I think the thin tape also gives more interior volume which can allow lower tire pressures.
After riding a 2nd bike that is titanium as a backup for a year, I have now come to realize just how harsh my main aluminum bike is. This got me started on this ongoing experiment where I have been lowering tire pressures on the aluminum bike for increased grip and comfort. I weigh ~ #195 and have lowered the pressure in those 25mm Challenge tires with the Vittoria latex inner tubes to about 72psi front and 84psi rear. They are still plenty firm to where I don’t seem to have much sidewall deflection. The ride over broken pavement is much more tolerable. I highly recommend exploring a similar path for yourself. I would submit that running 115 psi in 28mm tires is WAY overkill. You could put some Vittoria latex tubes in there and even @ your body weight run them much lower in PSI than you are now. You will have to experiment to find the number that gives you the magical combination of low rolling resistance, flat protection and (wet/dry) cornering grip.
I was was going to look up the specs on a Giant Defy 3 just to see how compliant or stiff a bike it is.
But it if I were going to guess, I would think right off the top without seeing you ride or knowing what kind of roads you typically ride that 85 psi front and 92 psi rear would yield a marked improvement on your Continental 28mm tires (Grand Prix 4000’s perhaps?). If that combination was fine but the ride was still firm you could most definitely go even lower than that.
I don’t mean to be too preachy here, but personally I’m pretty stoked about this game changer for me of running slightly wider rims with more supple high thread count open tubulars with latex inner tubes and thinner tubeless rim tape at lower pressures for an amazing feel/ride - very noticeable!
Let me know about questions 1 through 7 above, good luck!
07-27-19, 08:09 AM
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I just wanna go fast and not taco my rims. And they are so crazy expensive, rims in general.
For some reason I thought I’d ride at mid-90’s and it works. Figured I didn’t want my 250 bulk on maxed pressure tires.
Also on an unrelated front I was reading about oval chainrings and now I want one
For some reason I thought I’d ride at mid-90’s and it works. Figured I didn’t want my 250 bulk on maxed pressure tires.
Also on an unrelated front I was reading about oval chainrings and now I want one
07-28-19, 08:59 AM
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I have a Defy 2 with 28mm (act 30) Schwalbe pro one tubeless and run 75-80 psi in the back and 65-70 in the front. At this point in time I am at 240 lbs. Running the lower front pressure helps with cracks in the road and such and I don't feel I am beating up the front fork. The factory tubeless were 85 psi. Mine is a 2018, no sure when they changed to tubeless. Factory 25mm ran surprisingly smooth (@85) but I wanted a tire wider than the rim for rock protection.
I ride 3/4 mile on dirt (and rocks) before I hit pavement. I typically see a band of "clean" that is 5/8 inch wide on the front and 3/4 on the back when I get on the pavement. I feel that I am no where near too little tire pressure and the bike has a comfortable ride and no 'dragging' or sluggishness.
I ride 3/4 mile on dirt (and rocks) before I hit pavement. I typically see a band of "clean" that is 5/8 inch wide on the front and 3/4 on the back when I get on the pavement. I feel that I am no where near too little tire pressure and the bike has a comfortable ride and no 'dragging' or sluggishness.
Last edited by bgdoyle; 07-28-19 at 09:07 AM.
07-28-19, 01:45 PM
#10
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Here is one article on oval rings not from a manuf of them.
https://bikefitadviser.com/oval-chainrings/
07-29-19, 09:58 AM
#11
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They were called Biopace. I still seem them sometimes on old bikes locked at the transit station.
I just assume because they were a thing for a little while and then totally disappeared until recently that they didn't perform as billed or had some other problem.
So I just wouldn't, especially if my existing rings aren't worn and don't need replacing.
I just assume because they were a thing for a little while and then totally disappeared until recently that they didn't perform as billed or had some other problem.
So I just wouldn't, especially if my existing rings aren't worn and don't need replacing.
08-15-19, 09:14 PM
#12
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I usually like run 5 to 7 lb less on the front tire. I feel it gives a little better road grip and more comfortable on the hands when riding chip seal roads.
08-16-19, 07:27 AM
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Can't say what works for you, but for me, keeping my 700x28's pumped up to about 90 PSI works better for me. Less rolling resistance and I can clock in a slightly faster time than I can if they're down to, say, 60 PSI. So, in short, for me it's closer to the max. PSI, the better.
08-16-19, 08:41 AM
#14
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I am 240 and have 28's on my roadie at 100 psi.
My daily rider is a Specialized Sirrus (32's I think) and I run those about 90. I used to run them about 80 but performance seemd better at 90.
My daily rider is a Specialized Sirrus (32's I think) and I run those about 90. I used to run them about 80 but performance seemd better at 90.
09-12-19, 10:27 AM
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I'm 275 right now, I usually go for 105psi back, 95psi front (700x28c Gatorskins) Seems to be my sweet spot
09-12-19, 11:09 AM
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I am @225 mostly. I run 110. I get flats when running lower pressures.
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09-12-19, 01:07 PM
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FYI, there is this online Road Bike Tyre Pressure Calculator.
For the OP's 250 lb weight and 28 mm tires, it recommends a pressure of 104 psi (7.0 bar).
For the OP's 250 lb weight and 28 mm tires, it recommends a pressure of 104 psi (7.0 bar).
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09-12-19, 03:31 PM
#18
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I am 365 pounds and run 25s at 105psi.
09-13-19, 01:02 PM
#20
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I'm a pretty firm believer in the Berto tire pressure method, but since that is also the max pressure for my rear tire, it works out kinda easy. If it's tubeless, you can get away with lower pressure. Tire with more volume = lower pressure, lower pressure = more compliant ride.
On that unrelated note, I kept the Biopace chainrings on my vintage Miyata just to piss off bike snobs. Shimano screwed up when they said Biopace was designed for cadence of under 90RPM and people decided they weren't meant for going fast and the idea died out (again, for a while). I'm not sure whether it's the chainrings, the trainer riding that I am doing, or what, but my cadence is way better than it used to be, 60RPM feels slow now and I am a reforming masher.
You may not notice any difference with the oval ring. They were popular in the 80s and seem to be making a come back. I would spend my money on something else.
Here is one article on oval rings not from a manuf of them.
https://bikefitadviser.com/oval-chainrings/
Here is one article on oval rings not from a manuf of them.
https://bikefitadviser.com/oval-chainrings/
They were called Biopace. I still seem them sometimes on old bikes locked at the transit station.
I just assume because they were a thing for a little while and then totally disappeared until recently that they didn't perform as billed or had some other problem.
So I just wouldn't, especially if my existing rings aren't worn and don't need replacing.
I just assume because they were a thing for a little while and then totally disappeared until recently that they didn't perform as billed or had some other problem.
So I just wouldn't, especially if my existing rings aren't worn and don't need replacing.
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