chikai

Looking to purchase some Sumitomo HTR+

I did a search for "Sumitomo HTR+" and my two hour research is so far inconclusive. The two tire sizes that I am considering are 215/50 (stock) or 235/45. Basically I want to know if it's worth going to the larger size.

From TireRack.com
215/50/17 - $393.44 shipped
235/45/17 - $446.90 shipped

Will I really feel $50+ worth of difference by going to the larger size? I believe in all there is a 3/4inch tread width difference between the two sizes.

All your help are belong to us...

peiqinglong

I would go 235/45/17, better grip and it's pretty close to "stock spec" as far as speedo. But then again it's gonna cost nano seconds on the 1/4 and I recall you mentioning how much your roads suck. Although with a 45 profile, you can lower your car more

Pappy

The wider the tire, the more horsepower it takes to move it. I recently bought some Yoko's and I'm very happy with the 215/50's. And....they have a raised area to help protect the wheels from hitting the curb.

edgalang

I would really focus on getting the one closest to the stock size. Although the stock size is 215/50-17, the real thing you should look at are the revs/mile to keep the spedometer in check.

Michelin Pilot HX MXM4 215/50VR17 = 819

Sumitomo HTR+ 215/50WR17 = 829
Sumitomo HTR+ 235/45WR17 = 823

Both Sumitomos are smaller in size...but at least the 235/45 won't be as bad as the 215/50.

Personally, I'm going to wait till I can get enough cash to get some affordable 18's and get the Sumitomos in 235/40WR18, which has a rev/mile value of 820.

DeLucCL-S

i have 235/45/ZR17's on my stock CLS rims and i do believe you can tell a difference in handling/response.

The wider tread also looks nice too..especially from the back end

good luck

peiqinglong

It's such a shame that Acura never put 235s to begin with on our cars. Our cars are big and should thus get something that looks "fitting" to it. The 328s and 330s can put like 245s on theirs like nothing and here we're straining for just 235.

lou_RENAMED

checked Michelin website and saw that my 235/45 have 811 rev @ 45 mph

stock has 819 rev @ 45 mph

Questions is why is the difference in revolutions so high while the overall diameter difference is .01.

Stock 215/50 overall diameter = 25.5

Pilot Sport A/S 235/45 17 = 25.6

EricL

Pappy,

You keep saying this and I explained that this IS incorrect. I've even mentioned that "common sense" would seem to make people think so.

The "deformation losses" are ACTUALY LOWER in a wider tire.

I didn't just "make this up." I've got a number of suspension and tire books and papers that mention this. In addition, there used to be an eco-tire site that clearly showed lower losses from a 235/45-17 vs. 215/50-17 of similar construction. They were interested in low-loss tires.

One of the major losses are due to "deformation." The longer front-to-rear contact patch of the 215/50-17 "deforms" the tire's sidewalls MORE a 235/45-17. If you look on Tire Rack or other pages and look at Plus +1, +2, +3 sizing, you will see that as the tire is widened and goes to a lower profile, the width increases at the expense of the front-to-rear contact patch. The additional width makes up for the lost front-to-rear area (contact patch).

It is common to increase the tire pressure for increased economy on longer freeway driving trips; you are reducing the front-to-rear contact patch and reduces sidewall deformation losses.

EricL

[
1. The diameter is "unloaded". The tire's diameter is measured without any load on it.

2. The loaded radius is a better measure of revs/mile. The construction of the tire and the profile of the tire will change the relationship between: loaded radius, revs/mile, and diameter.

Never use the unloaded diameter to compute or compare speedo differences.

Revs/mile and/or loaded radius should be used to compute speedo differences.

Remember, when a tire is sitting up in the air, it is like thinking of a fixed circle (made of steel) that rolls over a train track (think of a circle on a tangent plane). A "real" tire does not roll on the street like that. It has a significant front-to-rear flat section – where is contacts the road. That front-to-rear section, in contact with the road, keeps the car from sliding off the road; in conjunction with the side-to-side patch, the front-to-rear patch defines the total contact area between the tire and the road surface. Increasing the tire’s pressure will change the loaded radius and revs/mile. (Increasing the tire’s pressure reduces the front-to-rear contact patch; decreasing the tire’s pressure increases the front-to-rear patch and increases “drag.”)

frryy

You guys don't rub with 235's?

lou_RENAMED

thanks EricL which bring up my next question stock tire max weight is 1433 lbs.@35 psi as per Michelin's website

on my Pilot A/S 235/45 the max weight is 1433lbs. @51 psi as per Michelin's website

stock calculates to 40.94 per 1 psi so at 32 psi which is recommended by Acura max weight on each tire is 1310 lbs.

does that mean that since it takes 51 psi to reach 1433 lbs.that calculates to 28.10 per 1 psi .. so that means I need to be running close to 46.62 psi to have the same 1310. lbs as recommended by Acura.


Please let me know cause I have spoken to Tirerack and called Michelin directly and both parties responded to keep what Acura recommends 32 psi which calculates to 899.2 max lbs. per tire so should I be running 46 psi ....I am currently running 36 psi cold.

Thanks in advance Eeee!!

EricL

I’d leave the tires at the 36 PSI cold. You can watch the wear with a cheap calipers (they have “depth” gauge and you can watch the wear on the tires from inside to ouside. Take measurements at various points of each groove and see for yourself.

I’ve now seen a few manufacturers just suggest that the stock tire pressure is OK for the tires. (I did find two people at Toyo that told me that stock pressure should be ok. When I called an asked to speed to a senior engineer and mentioned that the car would be driven in track and street events, I got the 39/40 PSI recommendation that I got from my tire retailer and their distributor).

I would keep an eye on wear and traction. Keep an eye on them and if you don’t want to spring for a depth gauge, get a penny and a pencil and do some “informal” measurements on the front and rear (more weight on the front).

I would run the stock MXM4s at 35PSI anyway, so….

You are going to be making trade-offs between: wear, harshness, forward and braking traction, lateral traction, and load capacity issues

Have a look at the MXM4 pdf file on the Michelin site. If you look carefully, you will see that the pressure increases up to around 38 PSI (I forget) for “V-rated” tires being driven at 140+ MPH.

Don’t be afraid to “try out” some pressure variations and see how they behave with different pressures. Make sure you take the pressure reading dead cold and don’t go below 32PSI.

joeandcarol2

Can one compare relative load carrying ability by calculating the crossection of the tire (donut)?

for instance 215x50x17 gives 215x(215x0.5) = 23112.5

and 225x45x17 gives 225x(225x0.45) = 22781.25

By the way what do you do for a living?