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I was out in the country for the weekend and had some Saturday night tire drama - not the rear one with the nail in it but right front. Topped it off with my Slime compressor, then it was low again this morning. Topped it off again and two miles later it was still telling me to adjust air pressure saying LF was 35 and RF 34. My compressor's analog gauge said I had both over 40, but I hate that gauge, as it requires the filler hose to be screwed on like 10-12 turns, then I fear I'm losing air as I screw it off. So I went to a gas station with a coin-op compressor that allows you to set the target pressure digitally and it shuts off when you reach it. Checked it with my trusty OG stick gauge before filling and the fronts were both closer to 35 lbs, so I set for 40 and filled both. TPMS said both were then 42, but, "close enough" I thought. Drove a short distance to a lunch place and RF dropped to 41, so I thought for sure I'd be screwed after lunch, but both fronts said 42 as we left so I figured I was safe to make the 50 mile trip home. Along the way home, LF increased to 45-46 (doing about 75mph in high 70's temperature) but RF stayed at 42-43 (rears had been equal at 40 but LR went up to 44 while RR only hit 43). I had so many tire and TPMS issues with my last car that I get crazy tire anxiety. Looking forward to tomorrow (well, sort of) so my local tire guy can take a look. I wonder if he can even repair a run-flat, if it needs it.....
Temperature makes a lot of difference (hence always check pressures on cold tyres). Even a very short trip will heat the rubber enough to make a difference.
I had a off road set up ( Land-cruiser 200) with a heavy off-road caravan (with the same wheels as the Landcruiser) for travelling in the Australian outback. I had a fancy 6 wheel TPMS system with temperature display, memory etc. The tyre near the exhaust was always hotter and higher pressure - tyres on the sunny side were always hotter (thus more pressure) etc.
Even while standing in the garage, the pressures on my SL tyres change depending on ambient temperature.
I even found an app for my phone that shows correct pressure dependant on ambient temperature, expected highest and lowest etc......yes obsessive.....
I suggest you inflate & check your tyres when they are cold and then forget about them (~ once a month check, depending on your mileage) unless the TPMS comes up with a low pressure warning. I used to obscess and try and get all my 6 tyres perfect and it is impossible because of all the other environmental variables. I don't think the TPMS in the SL is the most accurate system around and is more useful to give you a general indication......
Last edited by rorywquin; Jun 3, 2019 at 05:40 AM.
I raced cars for years;IMO the most fun you can ever have with your clothes on. But the point is that even between sessions we were all obsessed with tire pressures, factoring in ambient temps, track temps, etc. But I ended that all when I went to nitrogen in my tires; temp fluctuations were minimal at the most extreme temps on track. Today, my SL550, my E350, my son's Elantra, and my wife's Accord Hybrid all have nitrogen as the inflation gas. Less fluctuation in pressure, and for some reason, very little distillation of volume over time. Consider that as the option of choice.
EDIT: wheel cracked in 3 places, got it welded for $150. I'm pretty sure I remember cracking it, and it was about a month ago. It took a month of driving - and hitting more bumps, manhole covers and potholes - for the cracks to open enough to lose air.
Curious how the welded wheel is holding up, also did you encounter any issues with balance on that tire / wheel? Thanks!
knock on (black ash) wood, so far so good. I've had wheels welded by this guy before but never three cracks in one wheel. My tire guy takes the tire off the wheel and brings the wheel to the welder; gets it back the next day, then remounts, rebalances etc. This is my first car with no spare, so that complicated things somewhat, like a 7 mile walk home, a couple of drives by to check on my car in his lot on a jack overnight and a ride back to get it a day later. I've read of many who ditch runflats for standard tires and a repair kit/compressor but I'm considering a space saver spare and no jack (let AAA do it).
well, the welded wheel did NOT hold up very well. after hitting a fairly minor road defect - nothing like the original, teeth-chattering pothole - I was losing air again within a couple of days. looked like one of the welds re-split, plus a new crack. this time I had a spare tire thanks to THIS THREAD, so at least I could drive while I had it rewelded for $80. the welder siad that the wheels seem especially soft to him, and he welds alloy wheels all the time, so I'm now wheel shopping for someinth stronger than simply "cast". I was considering Enkei Racing wheels from TireRack, which are "1pc. Tilt Cast w/Flow Forming" but now I'm looking at "ROTARY FORGED" Mandrus Stirlings at a local independantly owned chain of tire stores. I want 18's, and though I've been back and forth on this, I think I'm gonna stick with runflats, maybe switch to Bridgestone from Conti's. some confusion as to whether they're available in staggered widths for my offsets, but I'm considering using the same tire and wheel size on all 4 corners (as Streamliner is doing with his new wheels), which would allow me to rotate tires F/R. Here's the Stirling in Silver w/ Mirror Cut Face. If I do get them, I'm also not sure which center caps to get....
Forged wheels are usually the strongest and lightest, less unsprung weight.
Anyone know if the AMG wheels are cast or forged?
Originally Posted by Streamliner
Some are, others are not.
I'm guessing only the ones that say "forged" are forged, and they don't come in 18". I'm hesitant to stick with 19" wheels hoping that forged will be enough protection against bad roads. I guess I'm guessing that an 18" "rotary forged" Mandrus wheel is better protection than a 19" forged AMG wheel....
I think the black and silver tri star would compliment the look of your car. All look acceptable, but with your car color, that seems to enhance the look more IMO.
I think the black and silver tri star would compliment the look of your car. All look acceptable, but with your car color, that seems to enhance the look more IMO.
well, I can get the wheels in staggered widths, but they can't find rear RF tires for the 9-1/2" width. looks like I'm going 8-1/12" all around; at least I'll be able to rotate!
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Slideshow: A one-of-one U.S.-spec Mercedes-Benz SLR McLaren Roadster became even rarer after a factory-backed transformation at McLaren's headquarters.
