newFitOwner

I suspect that the following is not too unusual, though it would be great to get the account of other Fit owners.

I find that the car starts to shudder at around 115 km/h (72mph). It becomes quite noticable at 120 km/h (75mph) through to 135 km/h (84mph). I didn't test it above that. It's not always there, and it is more often there when the engine is under load e.g. accelerating, especially up a hill. However, it is sometimes there when maintaining constant speed on level ground.

At first, I thought it was highly imperfect balance of the new snow tires, possibly due to rushedness since the demand for snow tires was quite high at the time that I had them put on. The car is new, so I didn't have a chance to try extensive highway driving with the all-seasons that came with the car. The place that put on the (new) snow tires was recommneded by a trusted mechanic, and they seemed very welcoming of a return trip to check the balance. It was a very unbusy time when I went back, so I think the double-check was done carefully. The guy who checked said that they were well balanced except for one that was a bit off. I assumed that he adjusted that one. I went for a highway drive just to see whether the problem went away, but the shudder is as I described above. Hard to tell if it was worse before.

Anyway, maybe cars like this aren't designed for much above 100 km/h? Or maybe the tires aren't? The tires are Michelin Xi 3, with good reviews. I vaguely recall running across educational material in the past showing how deformations can form on the tire at high speeds. As I said, I wouldn't be overly surprised if this was regarded as normal, but it would be nice to be sure. My 97 Tercel shook at high speeds, and I was kind of hoping that car/tire technology had moved the yard sticks further along.

manxman

Sorry, I can't say that this is a problem with my '09 Sport A/T. I cruise at 80 mph on most of the freeways around here, and have brought it up to 100+ on some long interstate road trips. Smooth (depending on road surfaces) with no shudders at all. We don't use snow tires around here, though, and I run brand-new Michelin Pilot Sport A/S 3 tires, but had no shuddering behavior with the stock tires that came on the new car.

claymore

Out of balance, bent rim, or tires out of true that it the only things that can make shudder.

newFitOwner

Thank you both, manxman & claymore. It's a brand new car that hasn't grinded up against any curbs, so the rims should be good. In fact the snow tires were bought with their own rims weeks ago. I was advised to bring them back, but since it is a reputable establishment, and since it got better with rebalancing (as described in my original post), I'll live with the shudder. It doesn't happen all the time and most of my driving is inside the city.