Big Tread for 951

[Kirby2]

I have bumped the horsepower on my 951, now I am looking to get it on the ground.
Question: the tire gurus say that a 245/45 - 16 will fit the 8" rear rim. Has anyone put that much rubber in the rear of a 951 successfully?

[andrewgoh]

The original PO installed Bridgestone Potenza RE730 tires (225/50R16 front and 245/45R16 rears) in my 951. You can see pics of the tires on my website link below.

The tires give the 951 a nice low profile and wide stance, but the rear Potenzas do give out a progressive louder hum as speed picks up.

[ronin]

hmmm, those tires don't look like 245s. could the rear shot (april) be of the old tire?

[andrewgoh]

Originally posted by ronin
hmmm, those tires don't look like 245s. could the rear shot (april) be of the old tire?

Ronin...I bought the car in March...still using the original tires that came with the car which the PO installed (it's my weekend driver and I don't drive it much). To confirm...I just went down and checked it......the rear tires are "245/45ZR16" and not "245/45R16".

Does anyone know if there is a real dimensional difference with the "ZR" versus "R" rating?

I checked the Bridgestone website, and here's what I found on the dimensions of the 245/45R16:

* Diameter 24.6"
* Width 9.6"
* Static load radius 11.3"
* RPM 847

There was no info in the site on ""245/45ZR16". Perhaps the additional "Z" denotes the "Z" speed rating.

On an additional note:
The standard tire for the 951 is 225/50R16. I plugged the data for the tire size, and compared it against the data for the 245/45R16. The 245/45R16 will show a 1.77% slower difference in the speedo.

I'll try and take more pics later this afternoon and post it here.

[ronin]

Originally posted by andrewgoh
I plugged the data for the tire size, and compared it against the data for the 245/45R16. The 245/45R16 will show a 1.77% slower difference in the speedo.

that's not a bad thing as the speedo is quite optimistic anyways. as for the tire size, I thought about it and figured 2 cm aren't going to make that much of a visual difference anyway so I guess that's about right. did you notice much difference in handling/performance?

[andrewgoh]

Ronin,

The RE730s were pretty noisy. The 245s in the rear made driving a little more challenging especially when driving in poor roads with deep grooves in them. The wider tires tend to follow the profiles of the grooves, and sometimes it feels like I am driving a boat.

But the wide track makes it fun when doing corners!

Andrew

[ronin]

I'm not too worried about the pavement grooves. overall handling is where it's at. looks to me like I'm going to try the 245s next time I get a new set of tires

[JAXTURBO]

I've been running 245/45ZR16's in the rear and 225/50ZR16 up front for years. Make sure you find someone skilled enough to perform a good 4 wheel alignment... otherwise you'll get uneven wear. The only drawback as mentioned earlier is noise at speed. Dunlops were noisiest, but very predictable and sticky. At the opposite end of the scale are BFG's. A bit quieter, and not as stick, but lets loose without much warning.

[ronin]

Originally posted by JAXTURBO
...but lets loose without much warning.

well that ain't good

[Kirby2]

I'm Thinking Yokohama EVS ES100s, they have a tread patch about .3 inch wider than most for the comparable size and seem to test well.

[1.2gees]

Just as a note, "track" is measured from the midpoint of the (theoretical) contact patch, putting wider tires on the car does not change the track.

I've had 245s in the rear w/out a problem. I get slight rubbing on a full tank on 225s w/about 1.5 inches total wider track, when driving very hard. I will trim the fender some when I go to 245s. A bit of toe in and negative camber will also help in reducing the rubbing.
Ahmet

[ronin]

what did you do to change the track? spacers?

[1.2gees]

Yeap. I can't remember if I have the weltmeisters or the stock (early) 944 na rear spacers on it now. The welts were 3/4inch a piece so that would've been 1.5 inches total. I cannot remember off hand what the na spacers were, so don't quote me on that.
Ahmet

[ronin]

hmmm. that gives me an idea. how readily available are the na spacers? and how much?

[1.2gees]

Well, I got the weltmeister spacers I mentioned above as a part of a trade from Carter (a member here), back when I had my NA. When I sold the car I kept one set of spacers, I believe they were the NA spacers. Anyway, they're usually fairly cheap from junk yards, or stuff like e-bay, but I've seen them fetch as much as $50 (and as low as $5-7). However, you really ought to go to longer studs when you do this. Handling improvement is noticable, with less understeer. Theoretically it should help ride a bit as well, but no noticable improvement there.

Replacing studs took a while on my then 180+k northern mile turbo, but not too hard.
Ahmet

[ronin]

o.k. that was weird. (and frustrating) wrote a long-winded reply and hit submit. server came back with page unavailable so hit refresh and it shot me to my last post on a totally different thread!!

anyway. I think the spacers will solve my dilemma. I wanted to replace my wheels with the wider 928 versions (same wheel) but couldn't find them. I wanted to fill out the wheelwell a bit more and get the handling improvement you mentioned. so for now I'll get the NAs as I don't want to deal with the rubbing issue. btw: what size tires did you run on the Weltmeister spacers?

[1.2gees]

I had the weltmeisters on the 944 na, they were only about 1/3inch wider per side (guessing). That car's had everything from a 195 to a 255 in the rear...

The turbo has had slight rubbing w/the 225s and the spacers in the back w/new (bilstein sport) shocks, but only when driving VERY hard. For example hitting full boost in 2nd coming out of a turn, and hitting a bump on the outside tire w/a full tank of gas and a passanger. Before the shocks, it rubbed fairly often however. I don't think 245s will be much of a broblem w/just a little trimming of the fender lip.

The spacers really do fill the fenderwells nicely. That and the handling difference was the reason why I did it.
Ahmet

[Kirby2]

This gets more interesting. What struts did you run with the Bilstein sport shocks on your turbo, since Bilstein does not make a front strut for the turbo? I've always been leery of mixing manifacturers on suspension parts.

[1.2gees]

I've got Konis up front. I did not want to mix them, and would've gone Bilstein all around, but as you know that's not an option.
Ahmet

[1.2gees]

How much power are you making, and do you have an LSD? Any other suspension mods?
Ahmet