Low Profile Tires

Nah you just heat 'em up and bend them back true.....

http://www.bentrimrepairorlando.com/

I've done that to a few front rims on tractors over the years.

Fortunately they can be heated up and pounded back into shape again. (And again. and again.)

I had an aluminum alloy mag that got dented. The tire would not seat any longer. I took it to a tire dealer and he said the wheel could not be fixed.

If you for style, stay away from curbs or use these

or like this

I hear that if the suspension is setup wrong that design handles like a fat man sitting on a beach ball when going around corners!

LT285/75-16s on my ride. What are these curb things you speak of?

Same on my truck but I have AT tread.

Steel rims not aluminium alloy.

You can still ding the rims even with lots of fat, depends on the size of rock and how fast you are going. Nothing a hammer can't make fit for purpose again.

Sidewall compression is part of your suspension. Wheel damage occurs when out of spec conditions occur (ie. impact with the Armco), or the suspension is incorrectly designed for anticipated track conditions.

What I mean to say is, use it for what is is designed for. Otherwise, change the design.

-A-

For those of us in the "older" catagory this is quite a change from the old balloon bias wheel and tire set up we got used to. Hell in my time "radials" were a radical departure.

Those ultra lows are not really good for anything. The idea was a lower sidewall profile would give better handling by reducing sidewall flex. This is true up to a point. It "sort of" compensates for an improperly tuned suspension and will give some semblance of better handling. However, If you look at racing tires, F1, indy, NASCAR, you will not see those low-pros anywhere. The ultra lows are simply status items to show off how much money you can waste. And one incidental curb contact will allow you to "show off" plenty!

Racing specifications determine wheel size. F1 is limited to a maximum wheel diameter (I think it's 14 or 15 inches). This is to limit the size of the breaks. Euro tuner car series limit the overall tire height, allowing them to run the lowest sidewall dimension possible allowing the largest breaks possible. Every form of racing is a series of compromises for maximum performance.

-A-

Low profile tyres and wheels look great, but at best there are only small gains in road holding.

On the negative side are higher cost, easily damaged when driving fairly normally, no climbing kerbs or other sharp edged things that may be found on or near roads.....also, reduced "warning" before "break away". Good for a professional race driver, but not for your average Joe, or normal roads....

Often a car is also lowered and this brings further problems with kerbs and speed bumps.

Driving with the maximum allowed air pressure helps a little to reduce possible damage, but makes a hard ride even harder. It does in my experience usually increase usable tyre life and often can make hard braking even better.

In my experience, the car tends to be more stable and easier to "point" with the steering with the correct max tyre pressure. But although that has been my experience with normal tyres/wheels and some low profiles...

Though when delivering cars with low profile tyres, I do pump them up to the max allowed as I prefer it, especially when driving at 150MPH on German Autobahns really is not a complete test, by me not having driven the car with normal tyre pressures further than the next filling station.

It would be good to hear from others using the same/similar techniques with tyre pressures.....good or bad......

Here's my personal experience with aluminum alloy after market rims. I did not have the extreme low profile tire you seem to be referring to, only 1 size larger, going from 15" to 16" on a Honda that could take 17" or 18" with lower profile tires. The track handling really improved without too much sacrifice of comfort because I stayed within the manufacturer's tire size offering. I did not hit a curb, just the usual crappy country roads in my area.

From normal driving on these roads my rear rims got slightly bent, just so the noise and vibration at highway speeds was not safe. I had them straightened by a shop in town enough so the vibration went away up to 80mph, but the noise never did. Maybe a heavier car would have been quieter. I ended up selling the aluminum for scrap, and since i got the wheels on ebay, I almost broke even!

So, it doesn't take extremely low profile tires or a curb to bend an aluminum rim and minor damage can be repaired.

You may be mistaken with regard to low profile tyres and lightweight rims. Apologies if not!

The actual "rolling radius" (I believe its called) does not change no matter what the tyres/rims are. As the tyres get lower/smaller, the rims get bigger!!!!

The end result is that the radius does not change.

If the radius changed either way, you would have to get the speedometer adjusted to read correctly (easily done by a specialist) and the number of miles shown on the Odometer would always be wrong unless new gears or similar are available for it!!

Andy,

I'm not sure how things work over there, but here in the 'States the "rolling radius" DOES change.

It is possible to stay close to the stock tire diameter when choosing a larger wheel diameter, but there will almost always be some change. And yes, the speedo will read incorrectly if you change tire diameter.

Profile Height (in inches)=(Aspect Ratio/100)*(Width/25.4)*2+Rim Diameter

I made a chart for my son a number of years ago helping to explain the different heights of different tires.

-A-

Which is why the law here makes it very difficult to change the radius here.....

eg. you are OUTSIDE the law if you do it to a car that is "on the road" so to say. It has to be taken legally off the road, changes and corrections made, then it must go through an approval process by the German TÜV, which may or may not allow it back on the roads again.....

Mechanically, its easy to do......the effects are welknown.

Which is why the aftermarket tyres and wheels are also carefully made here, so as NOT to change the rolling radius! Or the manufacturer would end up in prison or similar!!!

Here ya go guys......

Have Fun!

http://www.miata.net/garage/tirecalc.html

Nice, but not needed here as Speedos are not allowed BY LAW, to indicate a slower speed than actual.

BUT! They are allowed to show a higher speed than actually achieved, years ago, up to 20%, but I do believe that has changed to a max of 10%......

On this website:-

http://en.wikipedia.org/wiki/Speedometer#Error

I found this:-

European Union member states must also grant type approval to vehicles meeting similar EU standards. The ones covering speedometers ^{[4] [5][6]} are similar to the UNECE regulation in that they specify that:

• The indicated speed must never be less than the actual speed, i.e. it should not be possible to inadvertently speed because of an incorrect speedometer reading.
• The indicated speed must not be more than 110 percent of the true speed plus 4 km/h at specified test speeds. For example, at 80 km/h, the indicated speed must be no more than 92 km/h.

The USA is a bit lax:-

United States

Federal standards in the United States allow a maximum 5 mph error at a speed of 50 mph on speedometer readings for commercial vehicles.^[13] Aftermarket modifications, such as different tire and wheel sizes or different differential gearing, can cause speedometer inaccuracy.

I hope this helps.

Other 'wonderful' auto advances are plastic bumpers and keyless entry. If you keep the 'clicker' next to your cell phone the memory on the clicker can be erased. This is a big deal if you are far from home on a Saturday afternoon. The all time best is - controlling the accelerator through the car's computer. I guess Toyota learned that lesson the hard way. There are more but those are the worst offenders in my opinion.

Are you sure Toyota learned the lesson? AFAIK, any modern car comes with at least a few computers and networks. What new car has old-fashioned electro-mechanical ignition, or mechanical throttle linkage?

It's great job security for us computer geeks, but then we are the ones most aware of how buggy things can get. Still, as long as they're working, the computers & software provide zillions of benefits.

I buy the 'stupidest' car I can find. The computer in my car only controls the engine. I control everything else. It even has a manual transmission.