1 Avoiding Tire CollapseThe members who crashed or fell seemed to have pressures 50% below the Berto Pressure. I chose 25% (or keeping the pressure >= 75% of the Berto Pressure) since it provides margin. I see it as a Lower Limit I do not wan to be below.2 Supple TiresExperiment with 10% or 15%
Thanks for the info and help.
This makes an interesting study to see at what percentage underinflation from
the Berto recommended pressures correlates with tire collapse. Looks like 25%
so far.
But I still wonder if Berto chart applies on supple tires with wide rims, as I
think I read a BQ blo
LungimsamI would use pressures between 100% and 75% of the calculated F/R pressures. There should be enough room to find a comfortabe pressure John HawrylakWoodstown NJ On 09/15/16, Lungimsam wrote: So then looks like 75psi front and rear would put me in the zone like the 45psi on the Bleriot woul
On 09/15/2016 06:45 PM, Lungimsam wrote:
So then looks like 75psi front and rear would put me in the zone like the 45psi
on the Bleriot would. Trouble is, last time I ran tires that high on a bike
bike it made for some harsh riding.
I have been thinking of a 650b conversion.
The bb's of the B
The 24cm is measured bottom of bb shell to ground. 24 Bleriot 24.5 Rambouillet.
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So then looks like 75psi front and rear would put me in the zone like the 45psi
on the Bleriot would. Trouble is, last time I ran tires that high on a bike
bike it made for some harsh riding.
I have been thinking of a 650b conversion.
The bb's of the Bleriot and Rambouillet are within .5cm of ea
Lungimsam28mm 203lb distributed 45%F 55%R and without and with 5lb front load and compared to a current 55psig F&RNo Front Load 68psig F / 84 psig R Front underinflated by 13psig or 19%. Rear underinflated by 19psig or 23%5lb Front Load 72psig F / 84 psig R Front underinflated by 17
Ok, so now what if I am:
175lb rider on 27.9 lbs of Rambouillet bike with -~5lb front load on 700c x
28mm Compass Chinook pass tires?
I' m currently running them at 55psi, front and rear.
Thanks for the info, guys!
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Just FYI. I increased my rear tire to 75psi, but I have left my front tire
at 60psi.
On Saturday, September 10, 2016 at 9:16:21 PM UTC-7, Don Compton wrote:
>
> I have been riding 700x28 Grand Bois Cerfs for years. Yesterday, I finally
> lowered my pressures down to 60f and 70r. Why did I wait s
The values I posted, 47/54 psig were INCORRECT for a 38mm tire. I
mistakenly used the pressures calculated for a 35mm tire. I apologize.
The pressure for the 203lb rider & bike for 38mm
are 40psig F, 48psig R,
The pressures for the 203lb with 5lb extra on the Fron
Berto Tire Pressure App says 38 front, 52 rear. So your 45 AVERAGE is spot
on! It just needs to be redistributed.
Cheers,
GAJett
On Tuesday, September 13, 2016 at 6:48:27 AM UTC-7, Lungimsam wrote:
>
> So if I am 175lbs., on 27.9 lbs. of Bleriot, with 5 lbs. of front baggage,
> on 650b x 38mm
I remember an rbw employee who said if he ain't bottoming out, he's good.
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Ron Mc wrote: "The people who were exceptionally low also reported wrecks"
Yes, generally their tires were UNDERINFLATED by 25% to 50% of the 15% Tire
Drop Calculated Pressure, from my review of the posts.
I would recommend maintain your tire pressure at between 75% to 100% of the
15% Tire Dro
LungimsamFront should be 47 psig, Rear should be 54 psig. This is for a 45%/55% distribution for Rider & Bike and the 5lb load only applied to the FRONT wheel weight.Your 45psig/45psig results in the front at correct pressure and the rear underinflated by 9 psig (17% low).John HawrylakWoodstown
Put enough air in your tires. Go for a ride. Let some out or put some in
depending on what you think of the ride. Repeat process as/if necessary.
There is no absolute.
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So if I am 175lbs., on 27.9 lbs. of Bleriot, with 5 lbs. of front baggage,
on 650b x 38mm Compass Loup Loup tires, at 45psi front and back, where does
that put me?
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on the last tire pressure thread, one of the posters plugged everybody's
replies back into the Berto graphs and found out we were all but a couple
riding within a narrow error window on those graphs - we have naturally
gravitated there. The people who were exceptionally low also reported
wreck
But werent Bertos calculations on stiff tires? Much stiffer than the sidewalls
many use today? Compass, GB, etc.
Also on narrower rims than used today?
So does his table really apply anymore?
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Thanks again for this. I'll try 55/65 or so, though because my only high
pressure (ie, > 30 psi) gauge is the doubtful one on the pump, I'll have to
get another one. The other day the pump gauge said 20-25 for the 51 mm F
Freds, but the low pressure gauge showed ~ 15 in front; and indeed it felt
so
Patrick
15% TDC pressures for a 32mm El Pass for YOUR 200# Total Weight (175+25) is
52/64 psig F/R. So YES 65/70 psig F/R would be HIGH
13 psig high in F
6 psig high in R.
The rear is reasonable. The front probably could lose 10 psig.
>From the responses in another post on Tire Prressure, 2
Fortunately or unfortunately, I have another new Grand Bois 28 Cerf,so it
will be awhile until I need to purchase new tires. When I finally wear them
out I am going to buy some Compass 700x32 extra lights. Some complain about
the price of Grand Bois and Compass tires, but I get my money's worth
Thanks, John. I read Berto's article -- was it published in Bicycling? --
years ago, but I've never bothered to be as exact as the method entails. My
thumbs and forefingers are pretty well educated by now, and I am thinking
that even 65/70 for the Elk Passes is a wee bit high for my taste, unless I
Opps , hit something & it got sent unfinished
Patrick
Here are the tire pressures for the 15% tire drop method for the weights
and widths you specified:
175 Lb + 20 lb = 195 lb total weight 45%/55% distribution
23 27 29
F 89 69 61
R 112
Patrick
Here are the tire pressures for the 15% tire drop method for the weights
and widths you specified:
175 Lb + 25 lb = 195 lb total weight
23 27
F
R
On Sunday, September 11, 2016 at 5:26:41 PM UTC-4, Patrick Moore wrote:
> 175 rider + bike at sub 20 and another sub 25.
I find that even good bike shops pump tires much too hard; there is a "too
hard" even for cheap Kendas. When I pump tires for customers or friends, I
try to leave a wee bit of cush -- the sweet spot is vanishingly small with
cheap, thick-sidewalled tires.
Odd: I used otherwise very decent 559 X 32
Ok, what is the actual width. I interpolate on the slope and intercept of the published curves to get the curve for say a 29.5mm width. tell me the actual width and I can get the 15% TDC pressure.John HawrylakWoodstown NJ On 09/11/16, Don Compton wrote: Berto's old method does not take into con
On a side note, I took my sister in law to a few shops to test ride a bunch of
bikes and found that a common complaint she had was they were too harsh. Well,
the tires were all pumped up to rock hard!! Not to mention most stock tires on
the hybrids we were looking at are not the supple ones we'v
175 rider + bike at sub 20 and another sub 25. Elk Pass tires, measuring
~27 and ~29 respectively; run at ~65-70. I don't sweat digits f/r, but I do
use the pinch test to get front a wee bit softer. In fact, were it not for
the gauge on the pump, which for all I know may be defective, I'd just go
b
Berto's old method does not take into consideration the benefits of wider
rims.
On Sunday, September 11, 2016 at 9:06:17 AM UTC-7, John Hawrylak wrote:
>
> Don
>
> 28mm tires at 60psig F & 70psig R supports a TOTAL Weight (rider & bike)
> of 175 to 180 lb for a 15% Tire Drop (Berto's method) ass
I got ~175lbs rider + ~27.5 lbs bike + ~7 lbs.bag on both my Rivbikes at
any given time riding on Compass rubber:
Bleriot with 650b x 38 Loup Loup- 45psi front and rear
Rambouillet with 700c x 28 Chinook - 55psi front and rear
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With the 700x38 Barlowe Pass on the Hilsen and the 650x42 Babyshoes on the new
MAP and the lowest pressures I can get away with, I INTENTIONALLY ride on
rumble strips because even after riding these supple Compass tires for a couple
of years I still can't get over how damn comfortable they are.
Don
28mm tires at 60psig F & 70psig R supports a TOTAL Weight (rider & bike) of
175 to 180 lb for a 15% Tire Drop (Berto's method) assuming a 45%F and 55%R
weight distribution (typical Rando)..
John Hawrylak
Woodstown NJ
On Sunday, September 11, 2016 at 12:16:21 AM UTC-4, Don Compton wrote:
>
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