50 vs 45
 

I have four 17 x 7.5 rims to be delivered shortly. The big question is 225-45-17 tires or 225-50-17 tires. I know i'm looking at the height of the tires, but what would most of you recommend. I do have Koni struts with Ground Contrrol Springs on the car.....

THANKS

OKAY it's a done deal 225-45-17 plus they cost less :-) ...these are going at a good price...FALKEN TIRE 225/45/17 ZIEX ZE-512 but i would like to stay with the Yokohama Avids, decisions decisions........

225-45-17!!!
It's only 0.11" taller than stock.
A 225-50-17 would be 1 full inch taller and harder on your transmission!;)

yep... he is right

Tom

Ditto
-Bill (now SVreXersized!)

Making room in the signature??

Tom

Ah, he's still deciding on Wally or Bought not Billt!:D I'd think a nice 3 SVXs and not one is faster than a $500 parts car that Dave and Ben have.:eek:

Oh, I think it's going to be much faster...;) (I just won't be able to use the stock hood....)

http://www.subaru-svx.net/photos/fil...Ride/43130.jpg

-Bill

Question
 

Don't take this a nitpicking, it is a very legitimate question. How is a taller tire "harder" on our transmissions? I don't claim to be a super mechanic, but the logic or mechanical apects of this escape me.

I suppose more tire/wheel weight could require more transmission effort, but I don't see how size alone can unless the rotation of the portion of the tire further out on the radius causes the problem. If it is the weight, then we have not been addressing this issue in ALL wheel tire mods.

Anyway I would like to hear some experts opinions on this theory.

Lee

Great Bill is "thinking" again:eek: . It would still loose to a $2000 Jag no matter what engine you put in there, plus you'll need to work on the handling big time from what Paul told us.

Always thinking, my friend;)

I talked with Paul alot this morning when he dropped the 'reX off and he noted that the suspension might be too stiff. I might just be swapping suspension assemblies around between cars :cool:

Paul also mentioned that he strongly believed that the car would get into the 12s. He felt that he was traction-limited, thus only able to do 4 wheel burn outs:eek:

-Bill

a taller tire decreases the final ratio of the drivetrain. this decrease means there will be lower RPMS at speed. This means less flow from the AT oil pump and thuse the fluid not being able to circulate and cool as quickly. The reason the SVX auto overheats and dies is in part due to the 3.545 gear ratio selected for this car. Granted, it may be great for gas mileage BUT it also reduces the flow of the ATF throughout the system and allows temperatures to rise more easily. Thus overheating the transmission and destroying the viscosity of the ATF thus leading to transmission failure. Also, more load is needed to attain the acceleration that the car had before... It all coincides with the ratio found due to tire and differential selection. This is why the 4.44 swap is recomended for people who don't even want to race, becuase of the better ratio the flow of ATF is increased thus prolonging the life of the transmission....phew that was long winded

Tom

With the tire being taller, the car travels farther for the same number of rotations. Engine and driveshaft.
In this case about 4%.
It might not sound like much, but it does put more strain on the friction materials, and even the gears.
With a heavy, tall geared car like the SVX I would recomend against it.

If your car was differently geared, like 4.44s, it would not be a problem since you have a 37% lower ratio in first, 31% in second, and 25% in third and fourth.:)

The tire and wheel weight also comes into play.
The less rotational mass the quicker accelerating and decelerating.
If you went from stock wheels and tires that weighed about 40#s, up to the same diameter heavy wheel and tire like some Lexus or Mustang wheels out there that weighed say 48#s, you would feel the differance on your first drive.

What He said!:)
I ran the Subaru Select Moniter on a repainted SVX yesterday, and his trans temp went up to 208°f on a 53°f (as I remember:o ) day!:eek:
And his SVX has a factory rebuilt trans with only a few thousand miles on it since it's rebuild!
The reason I mention the fact the car was repainted is that when they repainted the car they painted the AC condenser with overspray!
Paint can work as an insulator!
Heat can kill a trans.

The transmission distributes the available unaltered engine power/torque regardless of wheel size. The wheel size in affect fixes, sets or alters, the absolute final drive ratio, with no alteration in respect of the forces transmitted via the transmission.

The only aspect for consideration is a possible change in the ratios selected for a particular duty or circumstance. This aspect would involve marginal tolerances, which are beyond consideration. What is more there is also the operation of the torque converter to consider, as this "smoothes" the application of power in all gears.

It can not be truly conceived that larger diameter tyres (within reason that is), will be "harder" on the transmission. In point of fact on a long run, the wear factor will be reduced as a result of a taller effective overall ratio.