IS300h

I've been driving my '18 IS300h for almost 3 months now and it's been an absolute pleasure so far. The only thing that bothers me is the noise level coming from the batteries' cooling fan next to the right hand side back seat. Usually this is not a problem for me though as I have the radio on most of the time, but if you have other people in the car it's quite embarrassing for a new car in this price range tbh. Of course it's not on all the time, but quite regularly though. Probably the dealer will say the noise level is normal, but I'm just curious about anybody else's experience on this? Wy does the fan need to cause a whistling sound? The HVAC blower fan doesn't whistle, so why does this cooling fan need to?

Good point, e.g. road noise was better on the RT2 and overall a slightly more comfortable tyre due to the softer compound. In hindsight I should have read more reviews on the RT2's, also considering my slightly more aggressive driving style. Still, I really didn't see this one coming, especially not from Dunlop, but as you say, their poor marketing definitely didn't help either.. The key thing I learned is that at least on the rear axle I need a stiff XL sidewall, especially in cars with a heavy boot. Who knows, I might be able to get away with placing the RT2's in the front, if not I'll be putting them up for sale... :-)

I think we're gonna have to agree to disagree on the tyres, I think the pictures speak for themselves. I'm not saying I have perfect handling now with the 225's, but just by changing to the Potenzas the handling improved beyond what I imagined possible, especially as this improvement was only linked to the tyre compound / sidewall stiffness, nothing else. They are the same size, same PSI (which at 36psi I don't think are under-inflated). I do agree with you that at lower speeds the RT2's performed quite well, but from around 65~70mp/h (depending on how sharp the corner of course) it indeed became a whole different story. For my next set of rear tyres, I'll get some 245s as probably everyone here agrees with you that the "potential ABS problem" story from the dealer is a lie.

I had actually originally planned to run staggered 17"s with 245s in the rear. But this was strongly discouraged by my dealer as I would get problems with the ABS system... Honestly, this still sounds incredible to me so I'll see if I can get some more info on that, not just from the dealer. Fact remains though that the tyres in my case made an extraordinary difference, I'm still trying to get my head around how a company like Dunlop can make such bad "performance" tyres. One thing I will also try though is to slightly increase the pressure on the rear tyres, just to see if it'll have a noticeable effect.

Sorry to have kept you guys waiting, but I finally got around to replacing the rear tyres... Problem is now solved! I'm now running on Bridgestone Potenza's (S001) which have pretty much the stiffest sidewall you can get (needless to say my tyre specialist wasn't a big fan of them..) Of course road noise has slightly increased (compound is also a bit harder), but I'll take that any day over such kind of poor handling on the Dunlop RT2's.. I'm going to write a complaint mail to Dunlop as these tyres are a complete joke, really unbelievable! I'll attach some pictures below so you can see for yourself. They should not be called Sportmaxx as these tyres have nothing to do with performance whatsoever. I kept my front tyres on the car just to make sure they were not the problem by the way. @Chris111: Your sidewalls are a bit lower (40) and maybe the DOT is also a bit older which might affect the compound (?) Next time you replace your RT2's, let me know if you can also make the sidewalls look like mine in the below pictures when they're off the car. Somehow I doubt it though as you don't consider them to have a soft sidewall. I have to say I still notice the extra weight in the boot of course which is inevitably affecting the handling, but with the Potenza's I can now at least keep the rear under control at 80+mp/h corners.

Thanks again to all for your helpful suggestions. I had a closer look at the compound of the tyres today and the sidewalls of RT2's in the rear have a really soft feel to them, much much softer than the sidewalls on the SP Sportmaxx in the front. (PSI is the same front & rear). I'll take the car to a tyre specialist this weekend and get their opinion on this, I'm still really suspecting those soft RT2's, so most likely I'll be replacing those very soon and let you guys know. Afterwards, I'll also replace the front tyres (if still needed) in order to pinpoint the rootcause. I really doubt it could be anything else as the car is brand new... (I'm also doubting the problem will disappear if I would put the 16's back on as these have a 55 sidewall and are only 205 wide, and unfortunately the tyres are not mounted anymore as I was going to sell them separately...) I also asked the Lexus dealer about mounting 245-45-17 in the rear, but they told me that by doing so I would get problems with the ABS system. (Anyone heard that one before? ) @ Chris111 : What tyre size did you have on your GS for the RT2's?

Thanks for everyone's feedback, much appreciated. I'm starting to suspect it may be the (new) Dunlop RT2 tyres... After reading several reviews, I found that other people have similar problems with these tyres: http://www.sciroccocentral.co.uk/forum/viewtopic.php?t=24059 Some of the comments are e.g.: "I've had the Dunlop sport maxx rt 2 - for about 1 week, took them off. They are a pretty soft tyre (although I had non XL version), and too soft a sidewall. Although were a very quiet and smooth tyre. When pushing hard they frightened the **** out of me as the car suddenly snapped as I cornered fast and almost entered a spin. They just did not inspire confidence when cornering hard, felt wallowy and not in control - and seem to suddenly fall off a cliff in an uncontrolled fashion rather than just gradual understeer." ...Which is pretty much what I'm experiencing. Feels indeed almost like driving hard on winter tyres with the softer compound... Looks like I'm gonna have to replace the tyres.. Anyone have any suggestions on this? Good Year Eagle F1 Assymetric perhaps? (I've always had those on my BMWs). If this would be really the case, then this would be unbelievable for an A brand like Dunlop, and why would they call it "sportmaxx"...

It's the CO2 friendly business edition which came with the smaller 16" wheels. However, I put on 17" wheels myself immediately after taking delivery of the car as 17" was not a dealer possible option due to the CO2 emission and the conformity certificate for the business edition. (In order to have 17" wheels I would have had to pay an additional 9k euro to upgrade to the Executive version... So I have 225-45-17 both in the front and rear running at 2.5 bar (I believe 36psi) as mentioned in the owner's manual. Of course I also had to transfer the TPMS sensors and afterwards I had to hold the TPMS reset button (hidden under the steering column) for 3 secs in order to clear the tyre pressure warning light. I have new tyres in the rear, but the ones in the front only have about 5mm left (slightly more worn on the sides) as I bought a used set of wheels (OEM lexus though, in perfect condition). Rear is Dunlop Sport Maxx RT2 (weight index 94) Front is Dunlop SP Sport Maxx (weight index 91) Could the tyres really have such a huge influence on the handling? It's a brand new car, only has 200miles on it now...

Hi everyone, I've just put my first couple hundred miles on a new IS300h, but is it normal that this car feels as if it's all over the place when going through (motorway) bends at high speed? Is it due to the extra weight in the boot? Before this car I've always had (rwd) BMWs, and never had any issues with high speed cornering. At lower speeds (below 60mp/h) the suspension feels perfect and the car really sticks to the road, but from 70~80mp/h the car feels really "swirly" and the tiniest steering corrections (only in a bend) make you feel as if you're driving a boat. Braking at higher speeds in a corner is also definitely something you'd want to avoid (which was never a problem in any other rwd vehicle I've driven). If you do, it feels as if the boot wants to overtake the rest of the car... Thanks for sharing your experience...