One Way to Smooth Ride a Little
08-30-2007 | 03:00 PM
#1
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From: Orion Spur, Milky Way
One Way to Smooth Ride a Little
If you are among those who would like a little less jarring ride; one solution would be to increase the tire sidewall.
The OEM Michielin MXM4 also comes in 235/60/18 (as opposed to 235/55/18).
This increases the tire sidewall by about 1/2 inch. It should help to absorb impact with a minimally noticable affect on handling. The 60 series weighs one pound more than the 55 so it will minimize adverse effect on unsrung weight.
As an added benefit it reduces revoutions per mile so your odometer will acrue miles at a slightly slower rate. (The speedometer will also be about 1 - 2 mph off.)
There are a number of all-season and highway tires available in 235/60/18.
The OEM Michielin MXM4 also comes in 235/60/18 (as opposed to 235/55/18).
This increases the tire sidewall by about 1/2 inch. It should help to absorb impact with a minimally noticable affect on handling. The 60 series weighs one pound more than the 55 so it will minimize adverse effect on unsrung weight.
As an added benefit it reduces revoutions per mile so your odometer will acrue miles at a slightly slower rate. (The speedometer will also be about 1 - 2 mph off.)
There are a number of all-season and highway tires available in 235/60/18.
08-30-2007 | 03:58 PM
#2
Instructor
Joined: Jul 2007
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From: Bay Area, Ca
I was actually planning on getting a 50 series tire, when it's the time of replacement. This was just a thought, because I think the tires on now are too beefy. I think getting a higher series tire "may" alter the actual handling of the car, since lower sidewalls, are generally stiffer, for better handling, and the beefier 60 series may fles a bit. You may get the comfort, but you may lose performance. I have no support to prove it, but it's always worth a shot at it.
08-30-2007 | 08:39 PM
#3
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From: Orion Spur, Milky Way
Yes, there should be some additional sidewall flex -- that is the point. It will result in a small ride-for-handling trade off, that may appeal to people who feel the present ride is too harsh.
Ride vs handling is always a balancing act. At one end of the spectrum you have stiffly sprung sports vehicles and at the other end you have, well....Buicks and Toyotas.
Ride vs handling is always a balancing act. At one end of the spectrum you have stiffly sprung sports vehicles and at the other end you have, well....Buicks and Toyotas.
08-30-2007 | 09:31 PM
#4
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I test drove an '08 base model today. I drove it for several miles over some of Houston's worst streets. I really don't know why people are complaining so much about the ride. Based upon comments that I've seen from posters on forums and magazine writers, I was thinking that it was going to so harsh as to be like getting hit in the kidneys. My impression of the ride is that it's quite pleasant, sporty, and not harsh. 
08-30-2007 | 10:04 PM
#6
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From: Calabasas
All new tires would be even better but note going away from the OEM tires will have a 10 percent drop in MPG, but these OEM tires are overpriced and offer OK performance, and certainly not worth what they're charging for them, stay at 55 just get a different brand altogether.
08-31-2007 | 12:28 AM
#7
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From: Toronto
Originally Posted by Nyjumpman23
improved suspension on 08 model
compared from the 07
compared from the 07
BUT my '07 was manufactured in May...so if the rumours are true and Acura started changing the suspension on later '07 models, then I might have the same setup as the '08s.
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08-31-2007 | 01:01 AM
#8
Trailingthrottleoversteer
Joined: Dec 2006
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From: Los Angeles, CA
Originally Posted by AbovePrime.
All new tires would be even better but note going away from the OEM tires will have a 10 percent drop in MPG, but these OEM tires are overpriced and offer OK performance, and certainly not worth what they're charging for them, stay at 55 just get a different brand altogether.
Heh - you'll understand: I go over Old Topanga to PCH twice a day, and I'll tell ya the stock Michelin 18's are piss poor for cornering - they are "all season".
To depress you even more there are NO performance summer tires in the off size 235/55/18 - except a Yoko "sport truck" Advan. I wish I got the 19's (the stock dunlops list for over $300 each on tire rack.com). It's a paradox unless you are willing to do some half @rse tire size.
08-31-2007 | 06:58 AM
#10
Meat Popsicle
Joined: Jan 2001
Posts: 386
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From: Chicagoland, Illinois
Originally Posted by Nyjumpman23
improved suspension on 08 model
compared from the 07
compared from the 07
This is rumor, right? I have not seen anything from Acura saying this is so, and they would most likely have stated as such if it were an 08 feature, especially since the press has mentioned a harsh ride in write ups.
08-31-2007 | 07:21 AM
#11
ACURA ENTHUSIAST
Joined: May 2007
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From: NYC
everyone's opinion is different.
I've test drove both, i felt the '08 had better handling in terms of bumpier roads
(especially in NYC, where every other block there's a crack in the road).
But I'm basing it on test drive. I'd have a better feel for a BROKe-IN Version of the '07 and '08( ala 3000-5000k miles after).
I've test drove both, i felt the '08 had better handling in terms of bumpier roads
(especially in NYC, where every other block there's a crack in the road).
But I'm basing it on test drive. I'd have a better feel for a BROKe-IN Version of the '07 and '08( ala 3000-5000k miles after).
08-31-2007 | 08:26 AM
#13
Meat Popsicle
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From: Chicagoland, Illinois
Originally Posted by Nyjumpman23
everyone's opinion is different.
I've test drove both, i felt the '08 had better handling in terms of bumpier roads
.......
I've test drove both, i felt the '08 had better handling in terms of bumpier roads
.......
I am also in the frost belt and got my RDX in late may, so I suppose it is a late year copy. I have never though that this car was rougher than the 05 TL that I had before. Definatly firm, but not in any way as it has been described in this forum.
Cheers.
08-31-2007 | 12:54 PM
#15
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From: Calabasas
Originally Posted by XLR8R
What do you mean by this?
08-31-2007 | 01:25 PM
#16
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From: Northern VA
I would not change the rolling diameter of the tires. The difference in height between 235/60-18 and 235/55-18 is 23 mm, almost one inch, which is 3.3% Generally about 2% is the max acceptable difference.
A lot of things will get thrown off, because the computers (ABS, VSA, etc ) are expecting one revolution of each wheel to equal the diameter of the 235/55-18. Plus your gearing will be taller, affecting performance, and you will also be affecting your odometer (although since Honda odometers read short, maybe this is a good thing...
Anyway, the manual even specifically counsels against using a different tire size. I would think long and hard before you change tire sizes.
Installing improper tires on your
vehicle can affect handling and
stability. This can cause a crash
in which you can be seriously
hurt or killed.
Always use the size and type of
tires recommended in this
owner’s manual.
A lot of things will get thrown off, because the computers (ABS, VSA, etc ) are expecting one revolution of each wheel to equal the diameter of the 235/55-18. Plus your gearing will be taller, affecting performance, and you will also be affecting your odometer (although since Honda odometers read short, maybe this is a good thing...
Anyway, the manual even specifically counsels against using a different tire size. I would think long and hard before you change tire sizes.
Installing improper tires on your
vehicle can affect handling and
stability. This can cause a crash
in which you can be seriously
hurt or killed.
Always use the size and type of
tires recommended in this
owner’s manual.
08-31-2007 | 01:38 PM
#17
B A N N E D
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From: Calabasas
Of course the manual would, they would NOT want to be blamed for someone installing 24 inch rims and rolling over, going up from 55 to 60 should not have "serious crash" results, lots of people have changed their Wheels/Tires to bigger sizes and have not noticed anything of the sort, or any problems with VSA/ABS.
08-31-2007 | 08:26 PM
#18
Racer
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Originally Posted by AbovePrime.
The OEM Tires are designed to get better gas mileage, either they have a high or low rolling resistance(I forget) but whatever it is, it optimizes for better gas mileage, All the Volvo owners have reported after getting new tires (they have the same tires OEM) they notice a drop in MPG.
09-01-2007 | 09:21 AM
#21
9th Gear
Joined: Aug 2007
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From: Suburban NYC area
Changing from OEM's
Three thoughts:
1. If you lease would Acura accept 235/60 18's at lease end?
2. TireRack has an upgrade function that tells you what upgrade sizes work on your car - I didn't check the RDX but it might help.
3. It is true that the higher sidewalls will give a smoother ride, they will also probably give you a buffer against curb rash (nice) - but, maybe need to go down to a 225/60 to keep the overall diameter the same - then you've got a skinny tire!! Hmmmph!!
1. If you lease would Acura accept 235/60 18's at lease end?
2. TireRack has an upgrade function that tells you what upgrade sizes work on your car - I didn't check the RDX but it might help.
3. It is true that the higher sidewalls will give a smoother ride, they will also probably give you a buffer against curb rash (nice) - but, maybe need to go down to a 225/60 to keep the overall diameter the same - then you've got a skinny tire!! Hmmmph!!
09-06-2007 | 02:23 PM
#22
Thread Starter
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From: Orion Spur, Milky Way
Originally Posted by Chas2
I would not change the rolling diameter of the tires. The difference in height between 235/60-18 and 235/55-18 is 23 mm, almost one inch...
http://www.tirerack.com/tires/Spec.jsp?make=Michelin&model=Pilot+HX+MXM4&partnum =36VR8MXM4HX&vehicleSearch=false&fromCompare1=yes& place=0
But the overall tire height is not as useful a measure as the sidewall height, which affects the radius (or measure from the hub center to the ground). Using the overall height difference (6/10")divided by 2 we get the increase in radius: 3/10". This means the 60 series Michelin will increase the car's ride height by 3/10" and that increase is in the sidewall.
Convert that 3/10" to about 10/32" (rounding) and you can see that the increased sidewall of the larger Michelin is equal to the tread depth when new (both are 10/32"). So the increased ride height of the 60 is no greater than the expected loss of ride height as the tread wears away.
Originally Posted by Chas2
A lot of things will get thrown off, because the computers (ABS, VSA, etc ) are expecting one revolution of each wheel to equal the diameter of the 235/55-18. Plus your gearing will be taller, affecting performance, and you will also be affecting your odometer (although since Honda odometers read short, maybe this is a good thing...
.
.
Basically, you'd just be getting 10/32" additional sidewall to absorb impact, and a little more flex in hard cornering. But if ride is a concern, it may be worth considering.
09-06-2007 | 02:44 PM
#23
Intermediate
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Originally Posted by AbovePrime.
The OEM Tires are designed to get better gas mileage, either they have a high or low rolling resistance(I forget) but whatever it is, it optimizes for better gas mileage, All the Volvo owners have reported after getting new tires (they have the same tires OEM) they notice a drop in MPG.
09-06-2007 | 03:33 PM
#24
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From: Calabasas
They get great MPG, I don't care to look into it anymore than I have, if you did not notice lethargicness in my post, but TRUST, the OEM tires are designed to get more MPG, and when you change them notice a 2-3 MPG DROP.
09-06-2007 | 04:38 PM
#25
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Originally Posted by AbovePrime.
They get great MPG, I don't care to look into it anymore than I have, if you did not notice lethargicness in my post, but TRUST, the OEM tires are designed to get more MPG, and when you change them notice a 2-3 MPG DROP.
Micheline, Bridgestone, Pirelli, to name a few, have made high quality tires for an awfully long time. If one of them came up with a tire that magically got 3mpg better than the competing tire type from another top brand, it would be an absolute miracle of invention.
Something that you'd hear from a top source, not some guy on a webboard that "doesn't care to look into it anymore".
09-06-2007 | 07:39 PM
#26
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From: Calabasas
Originally Posted by Fishbulb
That's great. Put together a bold claim without any supporting rationale, and say that you don't care to look into it anymore when questioned.
Micheline, Bridgestone, Pirelli, to name a few, have made high quality tires for an awfully long time. If one of them came up with a tire that magically got 3mpg better than the competing tire type from another top brand, it would be an absolute miracle of invention.
Something that you'd hear from a top source, not some guy on a webboard that "doesn't care to look into it anymore".
Micheline, Bridgestone, Pirelli, to name a few, have made high quality tires for an awfully long time. If one of them came up with a tire that magically got 3mpg better than the competing tire type from another top brand, it would be an absolute miracle of invention.
Something that you'd hear from a top source, not some guy on a webboard that "doesn't care to look into it anymore".
DROPS IN MPG!
READ THE TIRE REVIEWS
READ AROUND
DROPS IN MPG
I HAVE HAD THESE TIRES ON MY CAR OEM BEFORE
DROPS IN MPG WHEN MOVED TO A DIFFERENT BRAND.
09-06-2007 | 09:12 PM
#27
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From: Baton Rouge
Sorry bud, I was just reading on the TSX board that someone's mpg decreased w/ new tires. People frequently talk about it, but another posted quickly replied the oem michelins have low rolling resistance. It kind of makes sense, the michelins don't stick very well to anything. Maybe stickier tires= more rolling resistance. I was doing research because I will switch to the pole positions soon and thought the decrease in mpg is because of 1) more aggressive driving or 2)slightly heavier tires than oem. It could be a combo of all three, who knows? Bur rolling resistance is definitely a factor.
09-07-2007 | 12:52 PM
#28
haole kama'a-ina
Joined: Jan 2007
Posts: 593
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From: south of here
There is a difference in rolling resistance between the Grand Touring category (like the OEM Michelin and) the High Performance category, (like the Goodyear Eagle RS-A).
The compounds in the Michelin MXM4 are blended for low rolling resistance and long wear. This also reduces grip; the tire squeals easily under lateral load.
Acura chose the tire because they have to meet CAFE standards, but it underserves the RDX chassis. A High Performance-All Season or Ultra High Performance-Summer tire would do the car justice.
See this from Tire Rack:
I don't bother with the government's fuel economy numbers; I find Consumer Reports more accurate so....
Using Consumer Reports RDX economy of 18 average and 25 highway, a HP or UHP tire should reduce economy to about 17.5 average and 23.75 highway.
That is not the often stated 3 mpg though, it represents only .5 mpg average and 1.25 mpg highway. Perhaps, once people get a grippier tire they drive harder.
The compounds in the Michelin MXM4 are blended for low rolling resistance and long wear. This also reduces grip; the tire squeals easily under lateral load.
Acura chose the tire because they have to meet CAFE standards, but it underserves the RDX chassis. A High Performance-All Season or Ultra High Performance-Summer tire would do the car justice.
See this from Tire Rack:
In the United States, vehicle manufacturers are required to maintain an average fuel economy for the "fleet" of new vehicles they sell each year. Currently, the government Corporate Average Fuel Economy (CAFE) mandate is 27.5 miles per gallon (mpg) for cars and 20.7 mpg for light trucks (includes minivans, vans, and most pickup trucks and Sport Utility Vehicles).
A tire's rolling resistance does affect fuel economy. For that matter, CAFE is so important to most vehicle manufacturers that they demand their suppliers develop low rolling resistance tires to be used as Original Equipment on their new vehicles. In order to meet these demands, these tires are often designed with a priority on reducing weight and rolling resistance and are molded with slightly thinner sidewalls, shallower tread depths and use low rolling resistance constructions and tread compounds.
A vehicle's fuel economy is the direct result of its total resistance to movement. This includes overcoming inertia (Newton's Law), driveline friction, road grades, tire rolling resistance and air drag.
During stop-and-go city driving, it's estimated that overcoming inertia is responsible for about 35% of the vehicle's resistance. Driveline friction is about 45%; air drag is about 5% and tire rolling resistance is about 15%.
Overcoming inertia no longer plays an appreciable role in the vehicle's resistance during steady speed highway driving. For those conditions it is estimated that driveline friction is about 15%; air drag is about 60% and tire rolling resistance represent about 25%.
Now, lets explore a scenario where a High Performance replacement radial tire has a whopping 20% increase in rolling resistance over a low rolling resistance Original Equipment standard passenger radial. To calculate the potential change in mpg resulting from using the High Performance tires in place of the Original Equipment tires, we would multiply the tire's percentage of influence in the vehicle's overall resistance (15% in the city and 25% on the highway) times the High Performance tires' 20% increase in rolling resistance.
A tire's rolling resistance does affect fuel economy. For that matter, CAFE is so important to most vehicle manufacturers that they demand their suppliers develop low rolling resistance tires to be used as Original Equipment on their new vehicles. In order to meet these demands, these tires are often designed with a priority on reducing weight and rolling resistance and are molded with slightly thinner sidewalls, shallower tread depths and use low rolling resistance constructions and tread compounds.
A vehicle's fuel economy is the direct result of its total resistance to movement. This includes overcoming inertia (Newton's Law), driveline friction, road grades, tire rolling resistance and air drag.
During stop-and-go city driving, it's estimated that overcoming inertia is responsible for about 35% of the vehicle's resistance. Driveline friction is about 45%; air drag is about 5% and tire rolling resistance is about 15%.
Overcoming inertia no longer plays an appreciable role in the vehicle's resistance during steady speed highway driving. For those conditions it is estimated that driveline friction is about 15%; air drag is about 60% and tire rolling resistance represent about 25%.
Now, lets explore a scenario where a High Performance replacement radial tire has a whopping 20% increase in rolling resistance over a low rolling resistance Original Equipment standard passenger radial. To calculate the potential change in mpg resulting from using the High Performance tires in place of the Original Equipment tires, we would multiply the tire's percentage of influence in the vehicle's overall resistance (15% in the city and 25% on the highway) times the High Performance tires' 20% increase in rolling resistance.
Using Consumer Reports RDX economy of 18 average and 25 highway, a HP or UHP tire should reduce economy to about 17.5 average and 23.75 highway.
That is not the often stated 3 mpg though, it represents only .5 mpg average and 1.25 mpg highway. Perhaps, once people get a grippier tire they drive harder.
09-10-2007 | 08:49 AM
#31
3rd Gear
Joined: Jan 2006
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Agree with 737 Jock's assessment, i.e. a change of 0.5 to 1.25 mpg is a reasonable expectation of impact of switching from OEM low-rolling resistance tires to aftermarket tires.
From the Transportation Research Board report "Tires and Passenger Vehicle Fuel Economy"
http://onlinepubs.trb.org/onlinepubs/sr/sr286.pdf
"a 10 percent reduction in average rolling resistance... will lead to a 1 to 2 percent reduction in fuel consumption ". And looking at the data tables about actual tires (unfortunately not including current RDX tires), I'd guesstimate that a 10 to 20% change in rolling resistance is probably about all you're likely to experience, meaning a 1 to 4 percent increase in fuel consumption.
Also, something from the report that may help explain why some people perceive the difference to be larger:
"tread rubber changes permanently during the first 4,000 miles of use, resulting in lower rolling resistance" So, all else equal, brand new tires will have higher rolling resistance than old ones, meaning your fuel economy will go down temporarily even if you replace your old tires with exactly the same new ones.
From the Transportation Research Board report "Tires and Passenger Vehicle Fuel Economy"
http://onlinepubs.trb.org/onlinepubs/sr/sr286.pdf
"a 10 percent reduction in average rolling resistance... will lead to a 1 to 2 percent reduction in fuel consumption ". And looking at the data tables about actual tires (unfortunately not including current RDX tires), I'd guesstimate that a 10 to 20% change in rolling resistance is probably about all you're likely to experience, meaning a 1 to 4 percent increase in fuel consumption.
Also, something from the report that may help explain why some people perceive the difference to be larger:
"tread rubber changes permanently during the first 4,000 miles of use, resulting in lower rolling resistance" So, all else equal, brand new tires will have higher rolling resistance than old ones, meaning your fuel economy will go down temporarily even if you replace your old tires with exactly the same new ones.
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