Tires Size Conversions?

[davelar]

I am restoring my 1976 Penton 175 Jackpiner.  I need to replace the tires and want to get the proper sizes.  The Instruction Manual for the bike specifies 3.00x21 for the front tire and 4.00x18 for the rear.  What are the current tire sizes that correspond to these specifications?  I am planning to use Metzler MC5 tires.  Comments would be welcome.
Thanks,
Dave

[Steve Minor]

Front Tires
Metric Alpha Inch
80 / 90 MH90 2.50 / 2.75
90 / 90 MJ90 2.75 / 3.00
100 / 90 MM90 3.25 / 3.50
120 / 80 4.25 / 4.50
120 / 90 MR90 4.25 / 4.50
130 / 90 MT90 5.00 / 5.10

Rear Tires
Metric Alpha Inch
110 / 90 MP85 4.00 / 4.25
120 / 90 MR90 4.50 / 4.75
130 / 80 5.00 / 5.10
140 / 80 5.50 / 6.00
140 / 90 MU90 5.50 / 6.00
150 / 80 MV85 6.00 / 6.25
150 / 90 MV85 6.00 / 6.25

Steve Minor
Wilmington, NC

[davelar]

Thanks, Steve.
Dave

[t20sl]

Dave:  Steve is correct on conversions.  But...., tire company's don't always adhere to it. One company's 100/90-18 may be another company's 110 or even 120.  Even the same tire manufacturer's tires vary from one model to another.  If you want to see this sometime check out Goodyear's actual sizes listed on their web site for automotive from model to model. They vary as much as 3/4" in width on identical sizes.  Always try and measure actual tire for your application if width is critical.