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Call me a Fred
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Threads per inch.

It refers to the number of cord threads in under the rubber. The smaller the threads, the more TPI the tire has and the more the tire is pneumatic and is more 'round' and has better riding characteristics.
 

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TPI measurement

MikeBiker said:
Threads per inch.

It refers to the number of cord threads in under the rubber. The smaller the threads, the more TPI the tire has and the more the tire is pneumatic and is more 'round' and has better riding characteristics.
Be careful with how manufacturers define TPI. Some refer to the number of threads in each ply (fabric layer), while others count all the threads in all the plys. For example, one manufacturers "180 TPI" tire might have two plies of with 180 thin threads per inch in each ply, while another manufacturer's "180 TPI" might have 3 plies with 60 thick threads per inch in each ply. The tire with two thin plies will be more pliant than the tire with 3 thick plies.

There are many factors in tire performance. TPI alone does not tell the whole story. Also, contrary to what MikeBiker claims, tires with higher TPI are not 'rounder', although tires with thinner casings do tend to roll better (i.e. lower rolling resistance and conform to surface irregularities more easily)
 

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TMA = too many acronyms

General terms
AFAICS - as far as I can see
AFAIK - as far as I know
AKA - also known as
AMFYOYO - adios my friend, you're on your own (AKA Dear John letter)
BEG - big evil grin
BHAG - big hairy a$$ goal
BOHICA - bend over, here it comes again
BTW - by the way
BWTHDIK - but what the heck do I know
CUL - see you later (poor abbreviation)
DIY - do it yourself
DQMOT - don't quote me on this
FMTYEWTK - far more than you ever wanted to know
FUBAR, SNAFU, FUJIMO, BAMF - all contain the F word
FWIW - for what it's worth
FYI - for your information
IIRC - if I recall correctly
IMHO - in my HUMBLE opinion (never is humble)
IMO - in my opinion
IOW - in other words
KISS - keep it simple, stupid
KITA - kick in the a$$
LOL - laugh out loud
MYOB - mind your own business
NM - no message
OTOH - on the other hand
OTTOMH - off the top of my head
OOB - out of business
PMP - peed my pants
PITA - pain in the a$$
POS - piece of shiite
ROTFLMAO - rolling on the floor laughing my a$$ off
ROT - rule of thumb
RTFM - read the freakin' manual
SO - significant other (spouse, companion, favorite bike)
TMI - too much information
TTFN - ta ta for now (bye)
WDALYIC - who died and left you in charge?
WTF - what the heck
YMMV - your mileage may vary (along with everything else)

Bike Terms
TT - top tube or time trial
TTT - team time trial
BCD - bolt circle diameter
CR - chain ring HS - head set
STA - seat tube angle
HTA - head tube angle
RR - road race
BB - bottom bracket
TDF - Tour de France
CTC - center to center
ST - seat tube
JRA - just riding along
OOTS - out of the saddle
TDC - top dead center (in the crank revolution)
MUT - multi use trail
OTB - off the back
TPI - threads per inch
DFL - dead frickin' last
DNF - did not finish
DNS - did not start

Fitness terms
HR - heart rate
HRM - heart rate monitor
AT - anaerobic threshold
PR - personal record
LT - lactate threshold
BPM - beats per minute
RHR - resting heart rate
MSS - maximum steady state
 

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The higher the better...

John Nelson said:
So is higher TPI always better than lower TPI? Or are there any advantages to lower TPI?
and usually the more expensive.

The word supple is usually used to describe the ride of a high TPI count tire. Better performance, better cornering, traction and all sorts of magic.

9 times out of 10 I can rarely tell the difference between riding a 60 TPI and a 140 TPI. You can tell the difference in your hands as they do feel more supple.

Air pressure and general tire casings come into play as well. I prefer to by a higher count as I think (I said think, no science to back this up) they last longer with fewer flats.
 

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TPI advantages

John Nelson said:
So is higher TPI always better than lower TPI? Or are there any advantages to lower TPI?
Well, the tire manufacturers certainly want you to think high TPI is better! Hence the way some of them fudge the numbers for TPI (see message above).

The purpose of high TPI casing plies is to make the casing lighter and more pliant. There are many factors which affect tire performace, but in general a more pliant casing conforms to the road surface more easily, and rolls with less resistance. On the down side, however, is that thinner and lighter casings are less durable, and more prone to being damaged. Like with many other components, tire casing construction must always be a balance between performance and durability.

While a pliant casing is generally a benefit for narrow, high pressure road tires, it can sometimes be a liability on fat, low pressure MTB tires. A thicker, stiffer (low TPI) casing can be better at supporting protruding side knobs on MTB tires, so may be more desireable for tough rugged off-road conditions.
 

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John Nelson said:
So is higher TPI always better than lower TPI? Or are there any advantages to lower TPI?
TPI is THE #1 characteristic in ride quality. Get a pair of 290tpi Vittoria's Open Corsas for about $125 and you'll see what I mean.
 
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