Road Bike, Cycling Forums banner
1 - 12 of 12 Posts

·
Banned Sock Puppet
Joined
·
14,411 Posts
Discussion Starter · #1 ·
As most of us know, TPI = threads per inch.

What I noticed recently is that Continental tires list TPI as 3/180 or 3/330. What does that first number mean?
 

·
Registered
Joined
·
9,658 Posts
Explaining tire TPI, in depth

Dear Lennard,
Can you please explain TPI on bike tires? How is it measured? And how does it affect riding road and cyclocross?
—Jim

Dear Jim,
TPI of tire casing is Threads Per Inch. However, it’s not such a simple answer, because it is measured in a particular way, and there is misinformation out there.

A casing is generally made of threads laid down adjacent each other and stuck together with latex or compounded rubber. It is cut on a 45-degree bias, flipped over, and laid over another strip cut on the same bias, so the threads in the two layers are perpendicular to each other. Mark off an inch longitudinally on this casing and measure the threads within it. The TPI is the number of threads in an inch of casing on the top plus that on the underside. In other words, one layer of casing is actually two layers of parallel threads that are laid at angles on top of each other, and the threads in both layers are counted.

When comparing tires, though, make sure you’re comparing apples to apples when it comes to TPI. The important point is that folding a casing over does not increase TPI; it’s still the same casing, just folded over. A good example is this Continental Grand Prix4000 S II tire. Notice in the diagram how the casing wraps around each bead and then the edges overlap under the tread, making three layers of casing under the tread. You can see in the chart below the illustrations that Continental calls out “3/330” for the TPI, which means that three layers are counted to come up with the 330 TPI. It should be clear from what I have said that this is a 110 TPI casing, and that overlapping it does not change the actual casing TPI.

A handmade tubular or “open tubular” clincher tire is generally made by folding the edges over and sewing them together (tubular) or folding them over a Kevlar bead (open tubular clincher). But the doubling over of the casing along the edge is not added to the thread count. When it says 290TPI or 320TPI on a high-end handmade tire of this type, that is what’s in one layer of casing (which is two layers of threads).


As for how it rides, the casing is more supple the thinner the threads are (assuming they’re not stuck too tightly together). It more easily absorbs small inconsistencies in the riding surface, and this reduces the rolling resistance and increases the grip by increasing the amount of contact between the tire and the riding surface.

The threads in a 290TPI or 320TPI tubular are very thin — 1/145 or 1/160 of an inch thick, respectively — and they are only held together with latex painted onto them; the casing is not vulcanized, which sticks the threads together more strongly and stiffens it. A 60TPI tire (even if it is called a 180TPI by counting three layers folded over under the tread) has thick threads that are 1/30 of an inch thick, and they are vulcanized together; that casing deflects less easily over road imperfections. These effects are exacerbated in cyclocross, due to larger imperfections in the riding surface.
―Lennard


Read more at Technical FAQ: Electronic for ?cross, TPI explained, and more | VeloNews.com
 

·
Banned Sock Puppet
Joined
·
14,411 Posts
Discussion Starter · #5 ·
In other words it's Conti's way of trying to fool people that they use 330 when it's actually 110.


I got that impression, but wasn't sure. Thanks Jay, for the clarification!
 

·
Registered
Joined
·
8,792 Posts
Jan Heine over at Compass doesn't give the thread count on any of their tires. His reasoning is that they looseness of the weave has as much to do with suppleness as thread count, as alluded to in Lennards response in the OP.

As for how it rides, the casing is more supple the thinner the threads are (assuming they’re not stuck too tightly together). It more easily absorbs small inconsistencies in the riding surface, and this reduces the rolling resistance and increases the grip by increasing the amount of contact between the tire and the riding surface.


This makes plenty of sense to me and I find it to be worth noting, specially considering the fact that many of the tire manufacturers give us a thread count without allowing the number of wraps used to get that count.

I've been riding the Compass tires, Baby Shoe Pass 42mm 650b, and have to say that they are easy rolling supple good handling tires, no matter the thread count. This is a large tire so it's hard for me to compare them to the 700mmx25mm tires on my other bikes.
 

·
Premium Member
Joined
·
2,714 Posts
Jan Heine over at Compass doesn't give the thread count on any of their tires. ............
90 TPI for the Extralight and 60 TPI for the Standard for whatever it's worth which is not a whole lot without knowing the weave density, the thread thickness, the thread material and the rubber coating thickness over the casing.
 

·
Registered
Joined
·
8,792 Posts
90 TPI for the Extralight and 60 TPI for the Standard for whatever it's worth which is not a whole lot without knowing the weave density, the thread thickness, the thread material and the rubber coating thickness over the casing.
Yeah, I figured it was a low count seeing he holds those numbers close to the vest. I've been riding the standard and am happy with them. I'd like to try the extralight, but the standards are already pricier than I prefer.

I retired my 1st rear at 4000 miles, moved the front to the rear and put a new one up front. The front now has almost 3000 miles and the rear almost 7000 (about 2780F and 6780R) with zero problems. I probably safely put a few hundred more miles on the original rear before retiring it.

I haven't tried the 700c yet but over the winter I may convert my wives 27" Univega Specialissima to 700c and we'll try them then. Probably the Stampede Pass(32), maybe the Bon Jon's(35), if they fit.
 

·
Premium Member
Joined
·
2,714 Posts
The 32's accurately measure to their stated size; the 35's do not. I got 36.5 mm on them with 17mm rims.
 
1 - 12 of 12 Posts
Top