All

The responses provided a wealth of tire pressures for 32mm and 38mm tires.  
12 list members responded with reported rider weights, and actual 32mm and 
38mm front & rear tire pressures.  I put the information into an Excel file 
and compared the actual tire pressures to the tire pressures calculated 
using F Berto's 15% Tire Drop method assuming the following:
1.  The 12 members reported the RIDER weight, not the total bike weight.  I 
used a 26 lb BIKE weight (typical road lightweight steel tubing) to get th 
TOTAl weight for the calculation
2.  I used  45%/55% front/rear distribution for all members except 1 who 
reported an Upright use on 38mm tire (used a 40/60 split for this)
3.  I used the 32mm curve Berto published for the 32mm tire and used an 
extrapolation for the 38mm tire.  I caluated the front and rear pressures 
based n the front and rear weights (using the distribution) and a slope and 
intercept for each tire size, i.e.,   
pressure = slope * weight + intercept

The executive summary is:
The majority of the riders tire pressures are with 6 to 8 psig of the 
pressures calculated by Berto's method.  There were 5 outliers out of 24 
pressures reported (12 reports x 2 pressures per report), see below.  This 
indicates the majority of the responders are using tire pressures based on 
the 15% tire drop method.

The 32mm uses tend to OVER Inflate the Front tire and UNDER Inflate the 
REAR tire wrt to Berto's method.  The 32mm users may want to verify their 
Rear pressures wrt to Berto's method.

The 38mm tire users tend to inflate both Front and Rear closer to Berto's 
method than the 32mm users.

The 4 outliers were:
1 32mm user over inflated the Front by 11 psi
2 32 mm users under inflated the Rear by 9 psi and 11 psi
1 38mm user under inflated the Front and Rear by 14 and 24 psig 
respectively.

If any one reported Total Weight or has a weight distribution other the 
45%/55% F/R (except for the 1 38mm case of an upright), let me know and I 
will adjust the file.

I purposely did NOT include the Excel file since the list members 
responding did not know their information would be used.

PM me for individual data.  If all agree, I can include the Excel file, 
somehow.

John Hawrylak
Woodstown NJ


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