Fab 8

I will be getting a set of GSD3s to replace my 040s. As the GSD3 doesn't come in 225/45/18, I'm now looking at these 2 sizes - 235/40/18 or 245/40/18. I know the 245/40 gives a diameter pretty close to stock, but I'm not sure how the handling will be affected. Grip will be higher, but will the handling be less precise? 235/40 may be better for handling but overall diameter will be smaller (may be good for acceleration and bad for fuel economy though).

Or is there no noticeable difference in getting either of these 2 sizes??

RX4life

i have 225/35 and they can get really uncomfortable on bumpy roads...and the fact that i have to go up to 51 PSI doesnt help either...

you basically have to prioritze whats important to you...for daily driving the difference will be minimal between the 2...

id go with 235/40 but thats me..

dannobre

iTrader: (3)

245-40-18's are really common to run on the stock rims...they are about as wide as you want to go on 8" rims. They seem to be the best compromise for the stock wheels
They don't cause any suspension or rubbing issues and they max out the grip...

From a fitament standpoint the 245-40's are closer to the stock dia (.99% error) than the 235-40 ( 2.2% error)

Cost may also be a factor...the 235's may be a bit cheaper...and if you don't track the car at all it won't matter...

coldnoodle

245/40/18 is prob. a closer fit than 235. Did you lower your 8, if not, shouldn't be any problem.

Spin9k

Noticeable difference? Probably not, the 235 will give you 2.2% better acceleration, lower your speed in gears the same, may also weigh less, but they should also improve trasient handling because of a stiffer / shorter / straighter sidewall vs. 245 on the 8"rim, same tire. Same tire is important as tire brands/models vary greatly in how stiff the sidewalls are engineered to be (comfort vs performance).,

The 10mm nominal difference in tread width is only 3/8", but then again check the actual GSD3 width as tires vary a lot in actual tread width between brands with the same nominal size.

TeamRX8

iTrader: (25)

fwiw, 2.2% lower gearing doesn't equal 2.2% better acceleration, maybe you didn't intend for it to read that way

Spin9k

Ok maybe I exaggerated...how about a 'wee bit' faster with smaller tires...hard to calculate considering differing tire weights, rotating mass, tire adhesion, shift points, torque & hp curves, etc.

army_rx8

i'd just go with the 245/40/18's i have a seton my car (toyo proxis t1-s) and i didn't notice a difference at all in the way the car drives..other than it grips teh road much much much much much better.....did i mention it grips the road better?

mikeschaefer

yea but look what you were coming from, worn out re040s :P

I'm not saying I'm not going with 245/40 as a replacement, though

army_rx8

^haha good point the re040's are pretty craptastic next to some t1-s's or tr-1's ..or anythign else in that performance range. i know some people put on 255's all around on the stock rims...that doesn't seem to smart to me...the largest size you can "safely" put on an 18x8jj rim is 245.....minimum is like 215 or something. so if it's just as safe as the 225's why not go wider on a better tire..more grip is better. only down side is the are a lill more exspensive. but not that much

Fab 8

Thanks for all the comments. I just went with the 235/40/18 - my choice was made easier as the tyreshop did not have 245/40/18 in stock for the GSD3. Anyway, I thought the 235 looks like it is about the max width you can go - wonder if the 245 would make the rims look "over-tyred"?

First impressions on the way home was the much quieter ride. Suddenly, I hear a lot more of the engine! Pretty good so far.

V22Guy

Good Reading.

I just installed a set of 245/40R18 Toyo Proxes 4 tires this week. They feel more "solid" than my previous kuhmos and I have not experienced any rubbing in the few hundred miles I have put on them.

Fab 8

Quick update after driving a few hundred miles - the slightly smaller diameter didnt change the cruising rpms, and it feels a wee bit faster on acceleration (although thats in my mind, I am sure!). These tyres are excellent - quiet, very grippy, and doesn't screech until near limit. Highly recommended!

Feras

iTrader: (1)

i have the same set as you and i love em, if you do any high performance driving though make sure your tire pressure and alignment is correct or else you'll get sphagetti strands on the v's of the tire tread.

Jeromie

ok question... if i lower the 8, wat is the biggest size tire i can fit!?

BigOLundh

iTrader: (1)

I know you're new here, and i don't want to come off sounding rude, but...
Quick answer - do a search or start a new thread.

-hS

dannobre

iTrader: (3)

It depends on what wheels Some have gone as wide as 285-35-18....

I have 275-35-18 Falken Azenis on 9.5 wheels. No rubbing

yiksing

Care to clarify why 255 is no good?

dannobre

iTrader: (3)

Tires have a rim width that is recommended for that tire...going outside that will cause compromises in handling and safety.

245 is the largest tire recommended for the stock 8" rims. That's not to say that you can't go wider for specific reasons as long as you understand the compromises ......Autocrossers sometimes will run 275's on stock wheels for competition....but they won't drive them everyday on the street

Docj78

Apparently, I'm not understanding metric tire sizing, but how is it that 245/40's are closer to stock diameter than 235/40's???. BTW, I don't mean to post the 235 vs. 245 question in multiple threads--still getting familar with this site...

G-ReX

It's because the stock tires have an aspect ratio of 45 and the replacements are 40. Tire size calculators help with the actual numbers.