What does bias ply (Billboards) flat spotting feel like?

[767Jockey]

I drove the car today. It's been sitting for a very long time (about a year). I've hardly driven the car at all prior to that. I have a set of one year old Billboards on the car. I have really no time experience driving this car, and none at all with the Billboards.

Up to about 15 or so miles per hour, there is no noise, vibration, etc from the car. Once I hit about 20mph, there's a very strong vibration. In the past in the few times I drove the car, this vibration wasn't there. Now it's there. How severe is flat spot vibration? What does it feel/sound like? Could this be the cause of the vibration, or do I need to start looking elsewhere?

[DanEC]

If it is flat spotting, usually it will go away, or at least decrease, once the tires warm up.

[mrmustang]

You may not actually hear the flat-spotting, but the vibration will be speed sensitive, felt in the steering wheel, and the seat of your pants.


Bill S.

PS: Have you checked your tire pressure (cold) and adjusted upwards yet?

[eschaider]

The Billboards' rubber supposedly deteriorates fairly quickly, Doug. Not that it has anything to do with the flat spotting induced vibration but it reportedly affects tire adhesion so be cautious when you first flex your car's muscles after sitting so long.

The flat spotting I have experienced, not with billboards, is not initially noticeable because the tire rotates slowly enough it's circumference can pretty well conform to the road surface. As vehicle speed increases and the time interval available to conform decreases the flat spot becomes more apparent. After driving for a while the flat spot seems to go away and the ride goes back to normal until it sits for a few days again.

If that sounds like what you are experiencing then it is probably flat spotting. Next time you go tire shopping check out the Avons. They are about the same price wise but are not bias ply, do not flat spot and provide comparable traction, maybe better, than the Billboard alternative.

If you like the Billboard style lettering, there are a number of third party suppliers now that offer very high quality Billboard lettering you can apply on a Saturday .

[fordracing65]

Avons cost at least $600 more than Goodyears. Not even in same ballpark price wise.

[Mongoose930]

The difference is actually closer to $800 according to the Roger Kraus website. Having had both, the Avon's are absolutely worth the extra money. I have never had flat spots with the Avons and I can actually drive the car with one hand on the wheel if I need to. With the Goodyears, they would follow every road irregularity and I had to hang on to the steering wheel with a death grip every time I took the car out. I loved the look of the Goodyears, but I would never put them on my Cobra again. Buy once, cry once...

[fordracing65]

Actually when you price 4 avons from Roger K and 4 Goodyears from Jegs it’s an $1100 difference. Plus jegs ships for free so add another $200 for shipping the Avons. Like I said not even in the same ballpark price wise.

[CompClassics]

Both tire are manufactured as race tires, there is where the similarities end. The GOODYEARs are meant as a track tire to be used on paved tracks, the AVONs were designed for rally racing on combinations of both paved and unpaved roads. The GOODYEARs are a track only bias-ply tire and NOT DOT approved, whereas the AVONs are a radial DOT APPROVED tire. The AVONs are the only tire I recommend for Cobras, original or otherwise.

[incoming]

When my car is to be parked for a while, I air up the tires over 35psi. when I hit the road, I drop the pressure to 22psi front and 20 rear and have had no issues.

[CompClassics]

One other thing the difference between the drive of the GOODYEARs and the AVONs is night and day, the AVONs win in every respect.

[eschaider]

For the curious, these are the prices as of today for Billboards, Avons and Nittos.

Billboards first:

Size ................ Price........Source........Load/Spd Rating.........Dia..........UTQG

26.5-8.0 x 15.....$347........R. Krause...............n/a.....................26.5”............n/a
26.5–10.0 x 15...$350........R. Krause...............n/a.....................27.0”............n/a

AVONs:

245 x 60 x 15.....$521........R. Krause...............99 / V.................26.7”............80
295 x 50 x 15.....$595........R. Krause.............108 / V.................26.9”............80

Nitto NT555RII:

275 x 60 x 15.....$231........Summit/Jegs.........107 / V................27.99”..........100
325 x 50 x 15.....$231/271.Summit/Jegs.........111/112V.............27.83”..........100

Nitto is not a bad looking alternative even if they are street drag radials (DOT approved)

[fordracing65]

$2500 for Avon tires after shipping mount balance is just a joke price wise. One of the unfortunate aspects of owning a cobra. Said for years to bad Goodyear won’t make a DOT tire for our cars that matches the billboards in looks and sizes.

[1985 CCX]

Thud thud thud ..... after tires heat your good.

[saki302]

How are the Nittos on the street or track? Are they mushy being a drag tire?

[eschaider]

I haven't mounted a set yet but the side walls are not like wrinkle wall Goodyear slicks, they feel fairly stiff and substantial. Best advice is go to a dealer and take a look for yourself to see what you think. I suspect you'll like them

With a 100 UTOQ rating these are not 30/40 thousand mile tires. They are pretty close to the Avon 80 UTOQ rating so I expect them to be pretty sticky with good road adhesion. Best of all they are a Major Brand, readily available at a reasonable price point.

[DanEC]

The Nittos are pretty tall if those specs are correct. That might be an issue on some models, ERA being one.

[eschaider]

The specs come from the tire manufacturers so they are whatever they are however, I suspect pretty close to the mark. That said, there is no substitute for taking the time to assess the fit, suitability and and utility for your own car.

[KarlzEE Bebout]

767..."I drove the car today. It's been sitting for a very long time (about a year). I've hardly driven the car at all prior to that."

Might be a silly question or at least impertinent, but why on earth did you buy the car if you're not going to drive it?

Doesn't driving the car produce a much greater smile, bordering on rictus, than dusting and waxing?

[1795]

Just be aware that any tire that is really sticky, biased or radial, will hunt on an uneven road. They are great on race tracks or highways that are well paved, get on a lumpy country road and a sticky tire is going to grip every wave in the road; it's what they do. If you drive a lot of country roads that are poorly paved you may not want a really sticky tire. It's a cost benefit decision. Nothing is free in life, everything has its good points and bad; there are no perfect tires.

[CompClassics]

Originally Posted by 1795

Just be aware that any tire that is really sticky, biased or radial, will hunt on an uneven road. They are great on race tracks or highways that are well paved, get on a lumpy country road and a sticky tire is going to grip every wave in the road; it's what they do. If you drive a lot of country roads that are poorly paved you may not want a really sticky tire. It's a cost benefit decision. Nothing is free in life, everything has its good points and bad; there are no perfect tires.

I have yet to experience this issue with the AVONs, the driving manners of the AVONs are absolutely the best. They are sticky though.