"For driving more than 100 mph: + 6 psi"
 

That's what it says on the inside of my fuel tank flap about tire pressure, but I don't know how long the car would last going that fast.

3000 RPM = 67 MPH
3500 RMP = 78 MPH
4000 RPM = 90 MPH

Didn't get a chance to take it to 100 mph that day. This is with the stock rear end and 205's on it. The speedo seems to be correct based on mile markers and the lovely "your speed is XX" signs all over town.

Where do you think "red line" is? I'd be more concerned about other things than my tire pressure if cruising at 100 for sustained periods of time.

Peak horsepower is at about 4400 rpm, after which the torque will drop off substantially........so........it's unlikely that the engine will climb much above this level when pushing air at 100 mph or so.

As for the redline where the engine won't tolerate additional speed........that's more of an uncertainty. Brandon has run them over 5K without any consequences.

Speaking of Brandon, what's happened to him? I saw one of his old posts and he was not listed as being a "valid" member anymore.

He got mad at me and left.............:o

Hopefully I won't get in any trouble for saying this but he's still really active at the "other forum".

Nah.......no trouble at all. He's a moderator over there..........

Your speeds/rpms are almost exactly the same as mine with 205/70-14s, so hopefully they're both close to being accurate. That sticker must be the same on all W123s, my 240D even has one, and it would have to be dropped off a cliff to reach 100 mph. My 300D has touched 100 mph (4500 rpm), but not for long. I have driven at 85 mph for hours straight (literally) and have driven in the 90-95 mph range for minutes, but not hours. Surprisingly (to me), it still feels like it has something left at 90. I'd be curious to know what it would do, but I'm not inclined to push it that much with 326K miles.:o

I've only gotten up to 85 so far. At 80 my rpm's were about 3600.

I'm really impressed with the feel of the car at 85. My last car was a 5.0 Mustang and while it had no problem reaching the massive speeding ticket speeds, the windows would suck in and it would become harder to handle around 80-85. When I drive the Mercedes at that speed it feels like I could just as easily be going 40, except for the way the scenery is whizzing by.

Yup, that's what they were designed for.:)

.......and the roar from underneath the hood.;)

That's what the radio's for.:)

On my '95 I hit just short of 5000 rpms this morning - 110 mph.

It would have to be an aftermarket radio. The stock one isn't loud enough to drown that out........:D

Yep, I got the Sony head unit and 4 replacement speakers in the SD.........it'll drown out that roar with ease.

Actually, with the 2.88 and the larger tires, it's very quiet at 3K which translates to just about 70 mph.......about as fast as you can go around here.

If I ever need to replace my differential, I'll have to look into a 2.88 too.

Brian, Tom, how much do you think that would improve my mileage? :D