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MountainBikeReview.com's Forum Archives - General Discussion
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What's means 3Al 2,5 V in Ti tubing? And what's 60 or 120... (4 posts)
|  What's means 3Al 2,5 V in Ti tubing? And what's 60 or 120... | Mich
Jan 16, 2004 7:28 AM | | tpi in the tires.
Somebody can give a good tech talk? |
| sure | club
Jan 16, 2004 7:46 AM | | the numbers are the percent of the alloying metals in the titanium, 3 % aluminum, 2.5 % vanadium, the rest titanium.
tpi is threads per inch in tire casings. more threads mean the threads are finer and closer packed, and the resulting casing is usually more supple, lighter, and offer low rolling resistance due to its ability to deform readily to accommodate irregularities in the trail, aka hysteresis. that's a good thing, but lately with all the freeride idiocy, low tpi tires are being favored because their casings are stiffer and so less prone to pinch flat, and the sidewalls are more resistant to sidewall cuts. rolling resistance doesn't come up much with the gravity powered. |
| not quite right | PBe
Jan 18, 2004 10:33 AM | | on the tpi. Higher tpi which means the tire is more compliant also means higher rolling resistance. Rolling resistance is defined by how much the tire deforms when in contact with the ground. The more it deforms, the higher the RR, pretty much like when tire pressure is very low. Higher tpi doesn't mean lighter, weight depends more on the bead and tire rubber thickness. |
| In adding more to what club said ( which was exactly correct)... | Bikeless Rider
Jan 16, 2004 5:25 PM | | ...the 3Al/2.5V is typically used in the frame tubes, and 6Al/4V in the dropouts. Some are using fairly thick CP (commercialy pure) Ti in the dropouts now that oxygen free welding is more common. CP is also sometimes used in the toptube, to save cost on lesser expensive models, but doesn't seem to be too common. Oxygen contact during welding on this type of Ti makes it too brittle. CP is the softest of the three. 3Al/2.5V is softer and more ductile than 6Al/4V adding a better feel to the ride. There are very expensive frames now that use 6Al/4V tubing, both shaped and round. It's more typical to see the shaped 6Al/4V tubes as downtubes, with the rest being 3Al/2.5V, intended to blend stiffness with comfort. The latest incarnation of 6Al/4V tubing is smaller diameter, staight, round tubes used sometimes in the entire frame for ultimate light weight. The original 6Al/4V tubes were actually flat sheet, bent into large diameter shaped tubes, and welded (seamed tubing). Those that like Ti frames seem to have varied opinions on which design is best for all around, some leaning more towards stiffness, some towards comfort, but price certainly weighs heavy in the minds of most when making the judgement. If you're on a budget, take a look at the Airborne frames at: http://www.airborne.net/eready/janette/abhome.asp |
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