While I have not interest in actually testing it, why is the top speed on the '13 model listed as 159 MPH, but beginning in 2014, it's limited to 130?

 

Can't say why know, but I'm pretty sure my 2014 will go over 130 MPH.

 

The 2013 SL550 has a top speed of 159 mph (limited to 150), according to Car & Driver.

 

That's the part I don't understand. In 2013, the R231 was limited to 155 and beginning in 2014, it was changed to 130. I've been unable to find anything online giving the reason for the change.

 

In my experience, manufacturers electronically limit speed based on the speed rating of the tires that are installed even though the car is capable of higher speeds. 130mph corresponds to an H rated tire.

 

From TireRack:

Beginning in 1991, the speed symbol denoting a fixed maximum speed capability of new tires must be shown only in the speed rating portion of the tire's service description, such as 225/50R16 89S. The most common tire speed rating symbols, maximum speeds and typical applications are shown below:

L 75 mph 120 km/h Off-Road & Light Truck Tires
M 81 mph 130 km/h Temporary Spare Tires
N 87 mph 140km/h
P 93 mph 150 km/h
Q 99 mph 160 km/h Studless & Studdable Winter Tires
R 106 mph 170 km/h H.D. Light Truck Tires
S 112 mph 180 km/h Family Sedans & Vans
T 118 mph 190 km/h Family Sedans & Vans
U 124 mph 200 km/h
H 130 mph 210 km/h Sport Sedans & Coupes
V 149 mph 240 km/h Sport Sedans, Coupes & Sports Cars

When Z-speed rated tires were first introduced, they were thought to reflect the highest tire speed rating that would ever be required, in excess of 240 km/h or 149 mph. While Z-speed rated tires are capable of speeds in excess of 149 mph, how far above 149 mph was not identified. That ultimately caused the automotive industry to add W- and Y-speed ratings to identify the tires that meet the needs of vehicles that have extremely high top-speed capabilities.

W 168 mph 270 km/h Exotic Sports Cars
Y 186 mph 300 km/h Exotic Sports Cars

While a Z-speed rating still often appears in the tire size designation of these tires, such as 225/50ZR16 91W, the Z in the size signifies a maximum speed capability in excess of 149 mph, 240 km/h; the W in the service description indicates the tire's 168 mph, 270 km/h maximum speed.

225/50ZR16 in excess of 149 mph, 240 km/h
205/45ZR17 88W 168 mph, 270 km/h
285/35ZR19 99Y 186 mph, 300 km/h

When the Y-speed rating indicated in a service description is enclosed in parentheses, such as 285/35ZR19 (99Y), the top speed of the tire has been tested in excess of 186 mph, 300 km/h indicated by the service description as shown below:

285/35ZR19 99Y 186 mph, 300 km/h
285/35ZR19 (99Y) in excess of 186 mph, 300 km/h

As vehicles have increased their top speeds into Autobahn-only ranges, the tire speed ratings have evolved to better identify the tire's capability, allowing drivers to match the speed of their tires with the top speed of their vehicle.

 

So basically, they lowered the speed to 130 so they could put cheaper tires on the 2014 and later cars?

 

Probably. There may be other reasons such as crash testing, CAFE fuel economy certification, etc., but I'd guess that the tires are the main reason.

 

No, all SLs still use Y speed rated premium tires.

What is the source of the original post? There's no way SL63/65 AMGs limited to 130mph.

 

Exactly. Makes two of us. Need to know the source of the original post, unless OP is not in the US.

 

Got this from a review of the 2014 SL 550 on thecarconnection.com:
"Power's capped at a 6300-rpm redline, but most of it is available at 1600 rpm, giving the SL 550 extremely powerful acceleration. Mercedes pegs 0-60 mph times at 4.5 seconds, almost a second quicker than last year's edition, and top speed in this model is limited to 130 mph. Aug 18, 2014"

 

That is what I thought. FYI: 2013 and 2014 US market SL550 were identical. R231 SL550 is about 1sec 0-60 quicker than R230 was, but look at the article's date, while they clearly comparing, without explicitly stating R230 vs. R231. R231 cars are not limited to 130mph in the US. This is absurd. This as most other internet articles should be taken with a grain (or a rock) of salt.

EDIT: Just took a look at thecarconnection.com. They basically "state" (paraphrasing) that all SL550s are capped at 130 mph. Identical text for 2013 MY and 2014 MY. I am pretty sure all R231 SL550s are limited to 155 mph (they "wear" 186 mph tires).

 

OK, here's an interesting wrinkle: According to Mercedes my '14 SL 550 came standard with R rated 19 inch tires? They are only good to 106 MPH. Those tires were also on 2013 models. But in 2012, the standard tires were H rated and good to 130 MPH.

 

No, you are misreading sidewall marking. I.E: 255/35R19 (front Conti SSR 19" tires) or 255/35ZR19 does NOT mean "R" speed rating. R means Radial construction. The speed rating is immediately after the load index: 255/35R19 followed by 96Y, 285/30R19 followed 98Y. 96/98 is the load index. Y IS the tire's speed rating. Take a look at your sidewalls and look for markings as described above.

 

Thanks! I stand corrected. They are Y rated tires. That solves the issue. I do wonder how or why someone decided the speed was limited to 130? Strange.

 

I have had my 2014 SL550 faster than the stated speed limiter. The spedo stopped advancing at 160 mph, but the car went a bit faster. I took a pic of the spedo, but the tac pointer is not clearly visible so I can't work the math. I live in southern Nevada so there are LONG stretches of straight roads to play on.

 

That's badass. I'm sure everyone has daydreamed of doing this at some point!

 

Not everyone.

 

I’ve had mine up to 155mph on the Autobahn several times. It is a bit hair raising as it is not a nice quiet road as in the picture.

There is a lot of traffic on the Autobahn but worse still, is having to be very alert on the rearview mirror for the cars that are going faster and want to pass and me having to slowdown and find a gap in the slower traffic.

 

Lol Nice! 😀 👍

 

Wonder what happens if a roadrunner darts into the path of a car doing 160?

 

Wile E Coyote will finally get a meal 😀

 

Not hair raising, just fun At least when you are used to it...
We would open up to top speed whenever traffic allowed for it; 130mph used to be our cruise control speed

 

I always struggle with being at 155 then having to move over and find a place in slower traffic so that the really fast cars can get past.

I’ve also had the SL on a banked track (2 mile circle) & on the outer ring at 140mph (iirc) which is the speed at which you do not need to hold the steering on that track. Unnerving at that speed, hands off and only a couple of yards from the crash barrier flashing past. I did about an hour on it for peripheral vision training.

 

Hmmm. I would think that would be training for reciting the Lord's Prayer as fast as you can...