Is300H Ground Clearance & Steep Driveways

sc489 · March 5, 2015

One issue before I buy an IS300H is that I frequently visit my father some distance away who has a steep 15' section of driveway about 1 in 3 incline descending down to his garage (see photo).

I'm concerned that the lowish ground clearance of the IS300H at 5.3" may be a problem where the incline changes at the top of the drive. Where is the lowest point beneath the car? If it is near the wheels (e.g. engine sump), then this is probably OK but it may be a problem if the lowest point is midway between the wheels. Does anyone know the ground clearance midway between the wheels? I guess the lowest point would be the exhaust or propshaft?

Also, are there likely to be any problems with the hybrid drive in reversing from cold up the steep incline out of the driveway? I assume the engine will cut in to assist if required?

DJP · March 6, 2015

No idea about the clearance issue but the engine will cut in as soon as it's required, and that will be almost immediately.

In any given situation as soon as the vehicle is asked to deliver more power than the motors can supply, or if the Battery charge drops to 20%, the petrol engine will cut in.

The game is to try and max the time running on electric whilst using the regenerate braking to recharge.

Sent from my Iphone using Lexus OC

Rabbers · March 6, 2015

The 300h's low ground clearance has stopped me using a public underground car-park I previously frequented, the

angles at the points of access to flat areas being too acute. Although so slight as to be barely perceptible, scraping

occurred towards the rear in the neighbourhood of the exhaust - and this despite a practically empty boot and no

passengers in the back seats. As a matter of fact this should not have happened at all, the recommended minimum

clearance for vehicles using this particular car-park being posted as 115mm, which might worry the owners of some

supercars but not the 300h with its declared 120mm.

As regards reversing up steep gradients, I frequently do this in all kinds of weather and on different surfaces and the

300h performs admirably, the engine coming on virtually simultaneously with the first twitch of your right foot upon

reverse being selected.

Bratman91 · March 7, 2015

I don't have experience of going down a slope but going up a steep drive scraped mine directly under the front bumper which seems to be lower than the previous generations of IS250 which gave me no problems.

Rabbers · March 8, 2015

Anybody coming to the 300h from a previous-generation 250 like Michael and myself would be well advised to keep

the lower ground clearance in mind. I also used to have no problems with a 250 in situations like that of the car-park

mentioned in my post. This is not to say, however, that knowledge of declared clearances and the consequent risk

is necessarily helpful if, as is almost invariably the case, one is already committed to negotiating an unrecognized and

unavoidable obstacle when faced with it for the first (and hopefully the last) time.

The difference between the declared 135mm (= 5.3 inches) clearance for the 300h and the 145mm (=5.7 inches) for

the 250 is certainly quite significant in that it can mean getting a scrape or not. The 120mm clearance I misleadingly

mentioned in my post as being that declared by Lexus for the 300h was in fact a figure estimated by my trusty Lexus

mechanic as being more realistic if factors such as load, accessories, tyre wear, braking speed and suddenness etc.,

are taken into account.

zippyone · March 11, 2015

I thought that I would have problems accessing my garage, so on the day that I had an IS300 for a test drive, I took it home to try it for size, as part of that test.

When I leave the road I have a 90° right turn to negotiate, then a short straight, at the end of the straight is another 90° turn, but to the left. The left turn is on a slope that has a right camber, then it is a straight run into the garage. I put the car in the garage front ways and in reverse also tried turning it about in my parking area. It went well.

I now only reverse into my garage, keeping an old mattress against the back wall just in case of errors. My CT could not cope with the slope in the slightest of icy weather, or snow. On the two occasions the IS has been used in such conditions it coped admirably. I rarely park along the road when out, I park underneath the supermarkets or in underground car parks, but like Renato, I have to keep an eye on the angle at the bottom of the gradients, gets close sometimes.

Regards.

Michael.

sc489 · March 11, 2015

Thanks for your help.

It seems reversing up the drive I mentioned will be no problem but the change in slope might be a problem. The only way to resolve this is to try driving in and out of the drive (carefully). Lexus customer service and my local Lexus Centre have put me in touch with the Lexus Centre 300 miles away near to the drive I need to try - the latter Lexus Centre has offered to loan me an IS300H for another test drive when I next visit. Excellent customer service!

sc489 · April 23, 2015

I worked out the breakover angle of the IS 300H at only 11 degrees is unlikely to handle the steep drive. That's a shame since it would have been my first choice for a new car. I've noted a trend in modern car design to stretch the wheelbase with no compensating increase in ground clearance. Mercedes quoted a ground clearance of 92mm and a breakover angle of only 7.4 degrees for the Mercedes C200 which is the worst of any car I've considered.My current 2006 Honda Accord has a breakover angle of 13.7 degrees by comparison.

I'll probably need to consider a SUV style car. The Lexus NX 300H is a possibility but there are reports of extremely poor consumption compared to the IS 300H.

Car designers take note - a breakover angle of at least 13.5 degrees would be useful for steep drives and difficult car parks.