I currently have the Bridgestone EL42 touring tires and am desperately looking for an upgrade. (They’re actually dangerous in the wet.)

I have looked over many tires and am looking to use the stock rims with a slightly wider/lower profile tire. I have been looking at 225/45/17 and 225/50/17 tires. The 50’s are only 1.6% smaller diameter and drop the car about 0.25”, the 45’s 5.1% smaller and drop the car 0.67”. For the 50 series I would not even bother getting the speedo recalibrated, for the 45 series I would either have the dealer do it or I would build a pulse rate converter (I’m an EE) to get the speedo back in line.

Anyway, after looking at the available options, reading numerous reviews and making sure that the load rating of candidates was greater than the stock 1433 pounds, I came up with the following choices:

Yokahama AVS ES 100 225/45-WR17 (1477# rating) ~$112
Goodyear Eagle F1 DS-G3 225/50-YR17 (1709# rating) ~$154
Toyo Proxes T1-S 225/45-ZR17 (#1477) ~$147
Kuhmo ECSTA KU19 225/45-YR17 (1477# rating) ~$101

All of these tire’s specifications list 7” wheels as a recommended width. (Although, for all of them, 7” is at the end of the recommended range). I have read many posts where folks are using 235/45-17, but this seems to be too large for an optimum contact patch as none of the above tires in that size are recommended for 7” wheels.

I am looking to maximize the product of dry grip and ride quality. I would greatly prefer a tire that stayed quiet throughout its life.

I would appreciate any feedback on these tires anyone can give me. If anyone knows the weights or details about the construction that would be very helpful.



Tom

Sedan 6MT, Sport and some other usless options
Searching for the value engineered suspension...

 

F1 GS-D3's: I have 11k miles on my set. still quiet, starting to lose some grip, but still way better than stock. new they are like drag radial, wet is wonderful--look awesome

drawback, 15-20k max life if driven hard, 25k if you baby them.

Better Life thru Chemistry
Black on Black 03.5 Sedan 6MT - Goodyear F1 GS-D3's 225/55/17, Custom Intake Tube, '03 "Z" Suspension, Magnaflow resonator, 6 Wire 4 Guage Grounding Kit

 

I am going for 235/45 R17 F1 GS-D3
Discount Tires recommend them and I will order from them soon.

 

good choice, when my warranty runs out so I can afford my odometer to be almost 10% higher than actual, I want to switch to 235/45's.

I am not too worried about the speedo being off but losing 10
% of the rest of my warranty with the tranny problems this car has had scares me. 235/45/17 is sooo much better for this car than 215/55 or even 225/50

Better Life thru Chemistry
Black on Black 03.5 Sedan 6MT - Goodyear F1 GS-D3's 225/55/17, Custom Intake Tube, '03 "Z" Suspension, Magnaflow resonator, 6 Wire 4 Guage Grounding Kit

 

The 235/45 tires are not that much smaller in diameter than the stock 215/55's, only 3.7% smaller. So you would lose very little warranty time. But the issue is that, for all of the 235/45 tires I researched (12+ on Tire Rack's site), the recommended minimum width wheel is 7-1/2". In a stiff sidewall tire I assume that the contact patch may be distorted (bowed outward) so the grip will be lower and you would be better off with the narrower tires (if we assume that the tire manufacturers know what they are talking about). That's why I was looking at the 225/45 size (5.1% smaller diameter).

Tom

Sedan 6MT, Sport and some other usless options
Searching for the value engineered suspension...

 

But then 225 is a very slight increase in width or the tire compare to 235. Thats why I am leaning towards the 235 more and it has a smaller difference in speed.

 

You’re right; it's a tradeoff like any other engineering decision. I don't know what would be better in terms of adhesion because the tire manufacturers don't supply curves of grip vs. wheel width, etc. but in the balance I would guess you would end up with slightly less grip with the 235s. And the the tire will weigh less. BTW, 225/45-17 is an extremely popular size so prices are more reasonable.

Outside of the speedo calibration (which I think the dealer can change for you) don't also forget that you will be increasing the effective gear ratio for more “effective torque” at the wheels by the diameter difference, so you will be getting a 5.1% increase in acceleration with the 225/45s. Few engine mods will do that for the time and money invested on new tires, especially if you were going to buy tires anyway. The center of gravity of the car would also be lowered by 0.67" reducing weight transfer, so overall it's more of a performance mod to go to the 225/45-17s. I have gone down in diameter with low profile tires on several vehicles, always with very positive results.

Then again, if your just going for the bad a$$ wide tire look...


Tom

Sedan 6MT, Sport and some other usless options
Searching for the value engineered suspension...

 

"you will be getting a 5.1% increase in acceleration with the 225/45s." ???

Acceleration vs multipled torque is a cube function so essentially a good approximation is the cube root of the effective gear change [tire diameter change] also you must correct gross size down to effective rolling radius.........expect about <1% real difference.
Also 3% more rpms means 2-3% more fuel consumption per hour.

 

I happen to be running the GS-D3s in 235/45R17 now. I had the GS-Ds and had to replace them. My first size request was the 225/55s. None to be found in the area. I was riding on 2 tires with sidewall damage (no idea how it happened, lots of construction in my area, though). Guys at the GY place suggest 235/45s. I say the rim is too narrow. Of course they don't believe that I know my own rim width, so they look it up. They see I'm right, but insist the 7.5 WILL work on the 7. I know they're selling me tires AND I need the car for a trip to SC the next day, so I let them talk me into it. Grip is night and day. No pull through most puddles in the wet. Bulge is not bad. Grip is amazing. Dealer cannot recal the speedo (so they say), but say the ABS and VDC should not be affected by the smaller diameter. 500 miles on them already. Takes about 5 minutes to ride the flat spots out of them in the morning, though.

 

What do you mean by take 5 minutes to run the flat spot out of them?

I know 225/45 is a pretty good size but if I remember correctly, it doesnt have the proper load rating compare to the OEM tires.

 

I have the 235/45s on the stock rims. Seems a little rough ride in the morning when I leave the house. Road has a new surface, so I assume it's a little flat spotting while it's parked in the garage overnight. Rides smooth as silk after a few minutes, though.

 

You're may be correct about the cube function, if we are talking about time to distance where the reflected inertia of car is roughly equal to the inertia of the motor. My assumption assumes the rotational inertia of the drivetrain is zero compared to the reflected inertia of the car's translation. I could plug all of this in to a tangential drive calculator we have at work (we make servo drives) if I knew the gear ratio's. Do you know where I could get this data? It's not in the owners manual is it in the service manual (I have one on order). Do you know these numbers?
Anyway, if the car inertia and wind drag dominates, as I expect it would, the acceleration (time to speed) would be roughly proportional to the tire diameter change. This also means that you have to shift earlier, but we do have 6 gears! So the 1/4 mile would probably be improved.

Tom

Sedan 6MT, Sport and some other usless options
Searching for the value engineered suspension...

 

Lots of experiments conducted on diff gear [and tire gear] changes for 30 years have shown that the cubed function works in the real work quite well..
For example: the 3.538 1st AT tranny gear x 3.357 diff gear is 11.877 torque multiplication.............assuming 220 lb/ft at tire road interface and 12/12.5=0.96 = .....11.877 x 0.96 x 220 =2,508 lb/ft /2tires or 1254 lb/ft per tire.
Going to a 24" tire [12/12=1.0] =2613/2=1306.5 lb/ft.

Calculate the acceleration with 1254 vs 1307 lb/ft ~~~1.6%

You must consider that a more than 4% change might require an extra shift in say the quarter mile and you might lose more time during the shift than you gained by the acceleration improvement. This is critical in the G35 case as it is possible to complete the quarter mile in 3rd gear [AT] at redline.........playing with increased gearing will require a time losing shift but the G35 wil be faster to 90 mph just not in quarter mile.

Same problem with 6 speed since the diff is already increased to 3.538 and you complete the quarter near the end of 4th gear.

The engineers worked hard to get every last 0.01 sec in the quarter from gearing.........cause that's what sell the young buyer.

 

Many don't, but the ones in my post that started this thread were selected because they had load ratings higher than stock.

Tom

Sedan 6MT, Sport and some other usless options
Searching for the value engineered suspension...

 

I just got quoted $530 with install and balancing for 235/50-17 Toyo Proxes TPT, seems like a great tire according to reviews and only changes circumference by 0.03%.

***04 G35s 5AT/Sport***
***04 Volvo XC90 T6***