I am looking at a set of brand new 19" tires they are 255-40-19, will a 255 tire fit up front on a 19 x 8 wheel and 255 on the rear on a 19 x9.5 wheel?

Lets just say I would be getting these wheels very cheap.

Buy a smaller set of fronts and you will have a spare set of rears when needed, 255 is a little big for the front when going 19's from my experience.

Can I mount a say 225/45/19 up front on a oem springs?

Yup! These are 225x45x19's in the front.

8eight

so are the 45 series a lot easier on the wheels than the 35's?

The rolling diameter of the tire and wheel offset are the two most important points.

I ran 265/35 18 tires on the front for about a year with no rub but it took an ET6 offset to get the wheel far enough out to not rub on the side of the strut. A 225 could and would rub with a high enough wheel offset which is why 3 series wheels don't work on an 8.

About 25.5" tire rolling diameter will just barely clear the bottom of the spring perch which it the truly immovable object in this case. The stock tire diameter is approximately 25". Spring changes do not affect this measurement.

Front to rear rolling diameter must match within 3% or the computers get confused and cause problems with the ABS and Traction Control.

Yup! These are 225x45x19's in the front.

I am amazed you have no rub issues! The clearance on my fronts right now is about 5mm or so running 225 50 17s (25.86in net diameter). Your net is nearly 27in!

I really wanted to run 225 40 19s to help cushion the wheels from damage versus the ideal 225/35 set up. Your post makes me feel much more confident about getting 225/40's and being able to clear the perch! Thanks so very much!

Are you running CSi stops?

8eight

so are the 45 series a lot easier on the wheels than the 35's?Yes, The more tire the better/Softer.

TerryY Front to rear rolling diameter must match within 3% or the computers get confused and cause problems with the ABS and Traction Control So true, I learned the expensive way...:(


Auraraptor Are you running CSi stops??Your welcome and Yes, I'm wearing Csi Bump stops and rear springs.

So true, I learned the expensive way...:(



Can you go into more detail? The reason being I am running 225 50 17 front and 255/40 19 rear ( comes to like a 4.5% difference F/R) until I can find another 19in wheel to complete my set. When I replace the front with 225/40 19, the difference will drop to 3.6%.

I reason I am using the 255 rubber is I had a it laying around with great tread as a take off from my 7; it is a really good summer tire, so didn't just want to throw it away. Irrespective, I was going to change the rear to a more appropriate 255/35 when the rears need changing.




Your welcome and Yes, I'm wearing Csi Bump stops and rear springs.

Do the perches raise the car any?

Also, how do you compensate for the now large change in the speedo reading?

Thanks for all the info!

245 35 19 will fit on the front as well as 275 30 19 on the rear. Remember the sidewall (35) is percent of the width so the wider the tire the bigger the sidewall for a given %. Like Terry said above the biggest obstacle is the spring perch above the tire. If you look in your wheel well you will see where the interference will be. I have even contemplated cutting a pie out of the perch and welding in a semi-circle piece of steel to buy enough room for the combo I am looking for. No matter what your ride heith is (spring combo(s) lowered or not the relationship between the perch and the tire stay the same (as Terry stated).

When fitting big wheels you have to be familiar with how Offsets work! I have 285 30 20's in the rear, The fenders go right over them when i mash the pedal. Nothing rubs...

When fitting big wheels you have to be familiar with how Offsets work! I have 285 30 20's in the rear, The fenders go right over them when i mash the pedal. Nothing rubs...

That is quite true...just an FYI, I run ET15 all around. My questions still stand though from my previous post.

Yes I realize the perch is a fixed compeneant relative to the wheel when traveling, the question is if the CSi perch adds any clearance over the OE unit.

I would say no, The csi suspension is very similar if not the same far as the perch, other than the springs being stiffer and slighly lower in height, The perch heights look the same, I see no difference in csi and standard perch clearances. The perch is fixed and needs wheels fitted for clearance/ Correct offset. The same wheels/Tires also fits both cars! If they are different, I don't see it. One thing i did notice when i experimented with CSi springs up front in a 91 850 is that they raised the car up a LOT! So there is a chance of the front perch being different in location, But i doubt it.

I would say no, The csi suspension is very similar if not the same far as the perch, other than the springs being stiffer and slighly lower in height, The perch heights look the same, I see no difference in csi and standard perch clearances. The perch is fixed and needs wheels fitted for clearance/ Correct offset. The same wheels/Tires also fits both cars! If they are different, I don't see it. One thing i did notice when i experimented with CSi springs up front in a 91 850 is that they raised the car up a LOT! So there is a chance of the front perch being different in location, But i doubt it.Hmm, quite interesting. I assume the actual engines weigh very close to each other, so your hypothesis has merit.

Thank you for the info!

Again, the curiosity is killing me, how do you compensate for the now large change in the speedo reading?

What change? 3:91 LSD in one, 4:10 LSD in the other!-) It wasn't a big change before i change the gearing either, But it's closer to the original readings with the larger gears.

Also going too wide can have an impact on suspension/bushes wear.