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rbent Forum
https://rbentonline.org/YaBB.pl General Category >> Technical >> Tire inflation info https://rbentonline.org/YaBB.pl?num=1305525859 Message started by power_bent on May 16th, 2011, 1:04am |
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Title: Tire inflation info Post by power_bent on May 16th, 2011, 1:04am http://www.bikequarterly.com/images/TireDrop.pdf Check it out.. |
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Title: Re: Tire inflation info Post by aikigreg on May 16th, 2011, 8:55am And apparently us fatties over 155 pounds have to inflate the tire over the rated pressure for the wheel ;D |
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Title: Re: Tire inflation info Post by power_bent on May 16th, 2011, 10:18am aikigreg wrote:
[smiley=jawdrop.gif] [smiley=laugh.gif] |
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Title: Re: Tire inflation info Post by FlyingLaZBoy on May 16th, 2011, 3:16pm aikigreg wrote:
'fraid you're reading the chart wrong, Greg... the bottom (horiz.) scale is WHEEL LOAD, not total weight... [smiley=grin.gif] Granted, it still doesn't go high enough for ME, but...... being a linear-looking relationship, it's easy to extrapolate... I'm not sure what a B-brand hiracer load distribution is, but it's probably about 60 (rear) :40 (front). The Stratus XP is ~ 67:33, and the Xstream is closer to 75:25. So if combined rider/stuff/bike weight is ~245 pounds and you're on 28mm tires on a 60:40 hiracer, the chart indicates 110 psi for the rear tire (~145 pounds), and ~75psi on the front (~100 pounds)... On the other hand, if you're Jay on the XStream on 25mm tires, tipping the total scale at MAYBE 150 pounds combined, he should be running 85 psi on the rear, and no pressure whatsoever on the front... :D ;) |
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Title: Re: Tire inflation info Post by TonyWard on May 16th, 2011, 4:37pm FlyingLaZBoy wrote:
On the other hand, if you're Jay on the XStream on 25mm tires, tipping the total scale at MAYBE 150 pounds combined, he should be running 85 psi on the rear, and no pressure whatsoever on the front... :D ;) [/quote] I'm not sure why he even carries around that front wheel - seems like dead weight to me!!! PS: he had a full water bottle in his bag Saturday but I never saw him use it - he must be training for something |
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Title: Re: Tire inflation info Post by FlyingLaZBoy on May 16th, 2011, 4:57pm Just for fun, I extrapolated the Berto chart for us heavier folks... First, find your overall combined weight along the top of this table, then figure out what approximate rear/front load ratio you have between your wheels (trike riders, I can't help you... 8-) ). Find the two loads in the weight columns that apply. http://i977.photobucket.com/albums/ae256/pbrown8js/PressRatios.jpg Now, from the chart, choose the line for the size tire you're running, and the load on it along the bottom, then find the "recommended" pressure on the left. http://i977.photobucket.com/albums/ae256/pbrown8js/TirePressVLoad.jpg Basically for heavier folks, this says stay with 1.25 (32mm) or larger tires... but regardless, this should serve as a handy starting point for tire pressure -- adjust as needed, or as they say, "YMMV"... [smiley=laugh.gif] |
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Title: Re: Tire inflation info Post by jayg on May 16th, 2011, 5:22pm FlyingLaZBoy wrote:
I don't know Paul. May be wildly nonlinear past the chart limits. Would probably be safer to trade your bike in on a trike so wheel loads will be within chart range. :D |
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Title: Re: Tire inflation info Post by power_bent on May 16th, 2011, 8:06pm Man O man ,I'm in trouble here!!!!! |
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Title: Re: Tire inflation info Post by TonyWard on May 16th, 2011, 8:49pm I don't know about anyone else but when I need to haul a$$ I just make two trips. |
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Title: Re: Tire inflation info Post by rmillay on May 16th, 2011, 10:07pm I seem to have ridden about 30,000 miles on underinflated tires. It's a wonder I survived! |
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Title: Re: Tire inflation info Post by FlyingLaZBoy on May 17th, 2011, 1:51pm It would probably reduce the vibration transfer up front, but I'm a little wary about dropping a 1.1" tire down to 50psi and then getting a pinch flat... |
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Title: Re: Tire inflation info Post by FlyingLaZBoy on May 18th, 2011, 7:53am Just for funsies, I dropped the pressure in the front 1.1" Durano from its usual 110 down to 80psi, for the Mesquite ride last night. It was subtle, and not exactly a "double-blind test" (You know how it is, you make a change, then your mind somewhat artificially magnifies any expected changes that you think you sense...), but I have the impression that it significantly reduced the road vibration transfer to the bars and pedals (especially on the chipseal of the Hwy80 service road), with negligible effect on speed, positive or negative. And I didn't pinch flat on the nasty tracks at Scyene Rd. Regardless of real effect or not, think I'll keep it there for a while... |
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Title: Re: Tire inflation info Post by Ric_Clark on May 18th, 2011, 9:58am jayg wrote:
I don't know Paul. May be wildly nonlinear past the chart limits. Would probably be safer to trade your bike in on a trike so wheel loads will be within chart range. :D [/quote] TRIKES are good ridinnnnnnnnnnnnnnnn. |
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Title: Re: Tire inflation info Post by bob wand on May 19th, 2011, 10:50pm Much to do about nothing |
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Title: Re: Tire inflation info Post by aikigreg on May 20th, 2011, 8:44am bob wand wrote:
I wouldn't say that. While I've not calculated it scientifically as above, reducing tire pressure over rough roads has made a noticeable increase in comfort. |
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Title: Re: Tire inflation info Post by richardr on May 20th, 2011, 9:24pm Paul, Thanks! I printed out your table and graph. It will help me determine the correct pressure for our trike and bike tire pressures. Richard |
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Title: Re: Tire inflation info Post by Ric_Clark on Jun 8th, 2011, 9:36am richardr wrote:
OK, I am about around 230 lbs., the ICE trike is around 45 lbs = 275 lbs.....how much tire pressure should I have for my 20" wheels????? |
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Title: Re: Tire inflation info Post by FlyingLaZBoy on Jun 8th, 2011, 3:39pm Ric_Clark wrote:
Ric, it's not the diameter of your wheels that matters, it's the width of your tires... I'm going to assume that you're running 1.25" (32mm) tires. If your weight was evenly distributed between all three wheels, that would be ~90 pounds of load, so you find where the 32mm line intersects with the 90 pound column, and look to the left for pressure -- in this case, around 52psi. If you're running 1.1" tires, it's 65-70 psi. HOWEVER, your weight isn't evenly distributed among all three wheels - but with a trike, it's easy to put a bathroom scale under each wheel and have someone else read it as you sit in the trike... Your rear wheels should have equal weights, but may be different than your front. Let us know what you find out! Remember, this is just a recommendation of starting pressure -- modify it as your mileage varies... but I am still running my front 1.1" tire on the Xstream at 80psi instead of 110... |
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Title: Re: Tire inflation info Post by jayg on Jun 8th, 2011, 7:48pm FlyingLaZBoy wrote:
Ric, it's not the diameter of your wheels that matters, it's the width of your tires... I'm going to assume that you're running 1.25" (32mm) tires. If your weight was evenly distributed between all three wheels, that would be ~90 pounds of load, so you find where the 32mm line intersects with the 90 pound column, and look to the left for pressure -- in this case, around 52psi. If you're running 1.1" tires, it's 65-70 psi. HOWEVER, your weight isn't evenly distributed among all three wheels - but with a trike, it's easy to put a bathroom scale under each wheel and have someone else read it as you sit in the trike... Your rear wheels should have equal weights, but may be different than your front. Let us know what you find out! Remember, this is just a recommendation of starting pressure -- modify it as your mileage varies... but I am still running my front 1.1" tire on the Xstream at 80psi instead of 110... [/quote] A suggestion, Paul - The two wheels that are not resting on the scale should be shimmed to the same height as the scale platform for the wheel load readings to be absolutely accurate. The readings will be slightly lower, if shims are not used. |
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Title: Re: Tire inflation info Post by FlyingLaZBoy on Jun 10th, 2011, 8:51am jayg wrote:
True, but that amount of difference is no doubt irrelevant for what we're talking about, here... especially since my "heavier weights" chart is just my own extrapolation of the original data anyway!!! If my "engineering statics" math is correct, having one wheel on a scale would create about a 3-4 degree angle, tops, changing the effective weight by only a percent or so... or as Bob W said, "much ado about...." [smiley=duel.gif] |
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Title: Re: Tire inflation info Post by jayg on Jun 10th, 2011, 5:17pm FlyingLaZBoy wrote:
True, but that amount of difference is no doubt irrelevant for what we're talking about, here... especially since my "heavier weights" chart is just my own extrapolation of the original data anyway!!! If my "engineering statics" math is correct, having one wheel on a scale would create about a 3-4 degree angle, tops, changing the effective weight by only a percent or so... or as Bob W said, "much ado about...." [smiley=duel.gif] [/quote] Since I have a lot of time on my hands (I love retirement [smiley=thumbup.gif]), I have plenty of time to make "much ado about..." :) Continuing in that vein, I decided to determine my Catrike Speed's wheel loads, using a digital bathroom scale. Only a 2 pound difference shimmed vs. unshimmed. According to the Berto graph, the trike's front tires should be pressured to 48 psi and the rear tire to 34 psi. The Berto graph recommendations conflict with the 85 psi minimum pressure recommended by Schwalbe for the trike's Stelvio tires. Maybe the 85 psi minimum applies to a tire at the maximum recommended load. Who knows. Right or wrong, I personally like to run high tire pressures on the smooth pavement at WRL. |
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Title: Re: Tire inflation info Post by FlyingLaZBoy on Jun 10th, 2011, 10:05pm FlyingLaZBoy wrote:
jayg wrote:
Nice to know I've still "got it".... [smiley=vrolijk_26.gif] [smiley=pepper.gif] |
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Title: Re: Tire inflation info Post by power_bent on Jun 12th, 2011, 4:18pm I can't believe this thread is still going.................. [smiley=whistling.gif] |
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