LT tires on TT
I was telling a buddy of mine how I upgraded my TT tires from ST's to LT's (Michelin RIBS) and he would like to upgrade to LT's also. He asked if he could go to any LT tire as long as they had the cor...
Forum Discussion
CapriRacer wrote:Francesca Knowles wrote:
Still no sourced answer to my "what are the speed limit standards for LT testing" question...
I recall answering this question - as did others - and it has bothered me for a while why that wasn't picked up on.
Then I realized the question is worded a bit funny and its true meaning might be slightly different - So ......
When LT tires are tested for endurance, they are tested at 75 mph - as are Passenger Car tires, unless they are winter tires. Winter tires are tested at 68 mph.
By contrast ST tires are tested at 50 mph.
(and I hope I don't have to remind people that ST tires carry more load than a comparable LT tires)
Well...on the bright side, I guess you did answer my question per the speed LT's are tested at: 75 mph. That's exactly what I recall, and am happy you confirmed since for the life of me I can't find the applicable regulation. Thanks!
On the other hand... "fifty mph" is for during the break in period when ST testing. Actual speed/endurance testing goes all the way to 85 MPH.
This at least according to the protocols I quoted six or seven pages ago:
Francesca Knowles wrote:
ST tire high speed performance test requirements.
Link to sourceNHTSB wrote:
S2Application. This standard applies to new pneumatic radial tires for use on passenger cars manufactured before 1975, new pneumatic bias ply tires, T-type spare tires, ST, FI, and...snip...
§ 571.109Standard No. 109; New pneumatic and certain specialty tires.
CFR Title 49 571.109
S5.5High speed performance.
S5.5.1After preparing the tire in accordance with S5.4.1, mount the tire and wheel assembly in accordance with S5.4.2.1, and press it against the test wheel with a load of 88 percent of the tire's maximum load rating as marked on the tire sidewall.
S5.5.2Break in the tire by running it for 2 hours at 80 km/h (50 mph).
S5.5.3Allow to cool to 38° ±3 °C (100° ±5 °F) and readjust the inflation pressure to the applicable pressure specified in Table II.
S5.5.4Without readjusting inflation pressure, test at 121 km/h (75 mph) for 30 minutes, 129 km/h (80 mph) for 30 minutes, and 137 km/h
(85 mph) for 30 minutes.
