hitsofmiss

On second thought, I've always thought bigger wheels are more tolerant to rocks & rough roads because of the angle at which it collides an object. Remember the old 19" bikes were more comfortable to ride then the one with smaller wheels (16"-17").

Whereas, a lot of people in this forum thinks smaller wheels are better. It beats my logic. What do you think?

Coleroad

As long as you have the same outside diameter tire. the smaller the wheel, the greater the sidewall height. The more sidewall you have the more flex it will have. This flex acts as a spring giving you a softer ride. Bicycle tires when talking multi speed bikes, no matter the wheel size the tire profile is still made the same. The gain in comfort comes from the overall gain in tire diameter. The greater the diameter of the tire the more tire contact fore and aft on the road. The gain in fore and aft tire contact allows the tire to glide over the smaller imperfections in the road. This gives you more comfort. So between the two we are talking different things. The car tire we are not changing the outside diameter. The bike tire you are changing the outside diameter. Comfort gained in two different ways. The car you don't want to change the tire diameter. This affects overall gearing. It changes the speedometer. The rule is to stay within 1% of the original tire diameter, not that everyone does. For some it's form over function.

Coleroad

I'm assuming you ordered the stock size of 245-40-18, Not 245-45-18. The 45 profile would be if you were going with the 17 inch wheel.

Mazor1

Since we're talking tires in this thread I would like to get opinions on a new tire that I am considering. After much research reading actual customer reviews on TireRack I have the Continental Extreme Contact DWS at the top of my list, in the OEM size 245/40/18's.

I like the overall consumer ratings for this tire based on something like 45 million miles driven, no, not all on an SC430. Still, the ratings for overall ride quality, noise level, and dry/wet traction seems to be the best for a tire that won't cost me an arm and a leg.

However, in comparison to just about every other tire I looked at in the SAME size, this tire is listed as having an inch wider tread, which personally I like the thought of having more rubber on the road so long as it doesn't slow the car down in everyday driving.

So, my question is two fold. Can anyone else who has had this specific tire chime in with their experience, and also, what are the" expert" opinions on whether or not putting a tire that is about 14% wide with the exact same diameter would negatively or positively effect the overall ride. To me, a Quiet riding tire is up there on the importance scale since how a tire eventually wears is based much more on how a person drives and how well you keep your tires properly inflated and rotated at the correct interval.

Coleroad

Really it you are not going to notice the difference during normal daily driving. There are threes cons to wider tires. You get a little more rolling resistance. You are not even going to notice it. A reduction in how quickly the tire can shed water. Wider tires reduce traction on snow and ice. The minute amount that tire will be wider you are not going to see it. The difference you notice will be from the tires compound, sidewall stiffness, and tread design. Tires are subjective as to what is best. All five of my cars have different tires on them. This is because I want different things for each car. My bmw I have Bridgestone re-11's on. I drive it harder than my other cars. My jaguar has bfgoodrich sport comp 2's. It's also a summer tire. I want more grip than a all season tire, but I want some comfort too. The sc430 has Michelin pilot sport as/3's . I want a smooth quiet ride. I don't want road noise when cruising around. Land Rover gets an off-road tire. The daily driver (Ford Fusion) for work has Goodyear assurance tires. Long life all season. It fits my needs for that car. So it's about your needs for that car. I haven't had the dws before so I can't give an opinion on them.

hitsofmiss

I read this & other forums & ended up ordering 245-45-18. Did I misinterpret? ........I hope it will fit & there won't be any major issue with speedometer or performance.

Or should I better return it?

hitsofmiss

Coleroad,

Thanks for clarifying.

Bgw70

The sidewall height is 5% different of the 245mm footprint... 12.25mm sidewall height difference.
Total tire height change, one inch.

I think I calculated correctly. ;-)

Anyway, this is very minimal and I personally would not worry about it...
If you want what to check your speedometer, turn on a GPS on your phone, like Waze, and compare the speed on your speedometer to the GPS.

New speedometer reading change
Indicating 30mph
Actual 31.13mph

Indicating 70mph
Actual 72.63mph

Coleroad

It affects on transmission shifts, putting more load on it. The biggest deal is with the DSC. During an event when the DSC is needed its calculations are off slightly too. In a situation where an inches can be the difference between an accident or not. Tire diameter change before DSC not as big a deal in my opinion. Even on tire rack their recommendations are less than 1% diameter change. I'm not saying you can't have more than that and not have a problem. I am saying under certain circumstances it could be a problem. I would not take that chance. I would never suggest someone else to either.

Bgw70

Wow, hard to argue all of that, please continue to expand your explanation by including his driving habits, road and weather conditions and of course when and if he performs the periodic maintenance on his vehicle.
In particular, should he increase the frequency of the transmission fluid change interval?

The bottom line is, all of what you wrote sounds very glamorous and Gucci, but how are you going to prove if slightly larger tires are going to change anything...

Coleroad

Well, we can continue talking about the effect of tire diameter. It affects suspension geometry. All of the wheel alignment specifications are affected. The scrub radius is changed which affects handling. As we said the speed sensor is thrown off. All of these changes throws off the algorithms the computers are using. Abs, DSC, transmission shift points, ignition timing retard or advance. The list can continue. There is cause and affects. I'm just stating the facts. I know there are lots of people who go with larger diameter tire setups. That's fine if you want to. Just want people to know what else it affects on the car. I'm not trying to argue with anyone. It's about information.

Bgw70

That's fine and I am not here to argue either, the OP asked questions and I answered them...

You then quote me and all was good except your choice of words in the last couple of sentences.

When you quote someone, you are conversing with the quoted person, not the OP who asked some questions...

Maybe it was just protocol issue and you were really conversing with the OP.

BTW, what is DCS?

Coleroad

Bgw70, I'm sorry . Not the way I ment for it to be taken.

Coleroad

DSC, dynamic stability control

Bgw70

Got it! all is good!