Fold down back seats?

[IS350jet]

Originally Posted by Bichon If we were talking about a convertible, I'd agree with your assessment. But if Volvo, famous for the strength of their passenger compartment, and BMW, known for their superb driving dynamics can engineer split folding rear seats into their sedans without compromising the attributes they are most famous for, so can Lexus. Solving problems like this are what engineers are paid for. I agree, to an extent, but there is a difference between passenger compartment safety and body rigidity. Also, almost all European car manufacturers use a lot of "High Strength Alloy Steel" (HSAS) in their construction. Jap. cars use it too but not nearly to the extent that Europeans do. This is not as much for safety as it is for body strength. I wish Japanese carmakers would make better/more use of HSAS.

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[tqlla3k]

For BMW, the split fold rear seats are a part of the cold weather package.

As for the reason behind the non folding seats on the IS, I would assume its for chasis strength, reduced body roll, and sound insulation.

Other cars that have the split folds may still have a strong chassis.... but it would be even stronger if they re-enforced the area behind the seats.

[PGSberg]

The Acura TL is in the same boat. The rear seats don't fold. It is a structural cross member issue. Check the vehicle weights on cars that have fold down rears. I think they are higher because of the engineering involved to retain strength. The flip downs also limit suspension design. I would have liked them too but since my wife drives a '03 4Runner Sport, I have all of the carry capacity I need. It's one of those things that doesn't seem important when you drive off of the lot but niggles at you for the life of the car.

[Evitzee]

Lexus has been clear on their reasons for not putting fold down seats on their sedans ...... noise. It is their reasoning that their clients prize quietness over the occasional need to haul a pair of skis. They believe split seats compromise quietness and are another source of potential rattles. You can argue whether it does or not, but look at Lexus' customer base and Lexus' success. Their view is 'we must be doing something right'.

[TimboIS]

I prefer the non-folding rear seats. If I wanted them, I'd have bought an RX.

[MrMut]

They would be nice, but i would only use them once in a blue moon... Not a huge deal to me personally.

[phatboyc]

Originally Posted by Bichon

If we were talking about a convertible, I'd agree with your assessment.

But if Volvo, famous for the strength of their passenger compartment, and BMW, known for their superb driving dynamics can engineer split folding rear seats into their sedans without compromising the attributes they are most famous for, so can Lexus. Solving problems like this are what engineers are paid for.

My thoughts exactly.

[G35TOIS350]

yeah one big complaint i have is no fold down back seat. really sucks

[t3abag]

I found some comparison's on cars with and without folding back seats, to be more specific, i found it on the E46 sedan.

BMW E46 Sedan (w/o folding seats) 18,000 Nm/deg
BMW E46 Sedan (w/folding seats) 13,000 Nm/deg

That would equal to a 5,000 Nm/deg less structural rigidity just from the folding seats alone. If you want maximum torsional rigidity, you want a short car (that's probably why the Mini does so well), with small doors, hardtop, no sunroof, not a hatchback and have no folding rear seats. If you want even more stiffness, you can add bracing (strut tower, upper and/or lower), seam welding, and a roll cage.


All things being equal a stiffer chassis will result in better handling because under tight cornering loads, the suspension points do not change as much, which gives the tires a more optimal geometry and contact patch on the road.

You can stiffen the chassis by adding more reinforcements (hence weight) but then you get into the tradeoff of weight affecting the handling, especially if it is at a higher center of gravity like in the roof, or upper pillars.

[Reyngel]

Originally Posted by Evitzee

Lexus has been clear on their reasons for not putting fold down seats on their sedans ...... noise. It is their reasoning that their clients prize quietness over the occasional need to haul a pair of skis. They believe split seats compromise quietness and are another source of potential rattles. You can argue whether it does or not, but look at Lexus' customer base and Lexus' success. Their view is 'we must be doing something right'.

But that doesn't explain why they don't at least offer it as an option for those who would rather have convenience over a very mild difference in sound deadening.

[t3abag]

Originally Posted by Evitzee

Lexus has been clear on their reasons for not putting fold down seats on their sedans ...... noise. It is their reasoning that their clients prize quietness over the occasional need to haul a pair of skis. They believe split seats compromise quietness and are another source of potential rattles. You can argue whether it does or not, but look at Lexus' customer base and Lexus' success. Their view is 'we must be doing something right'.

Noise is not a real reason to why they don't have folding seats. THere are many ways the sound goes through. If you look at the over head behind the back seats, it is fully meshed and sound easily goes through there. I even took out my stock subwoofer so i can get more "sound" into the cabin from the subs. As i stated in my above post. It is a trade off between rigidity and weight. Just refer to my post two up.

[lobuxracer]

Originally Posted by IS350jet

I agree, to an extent, but there is a difference between passenger compartment safety and body rigidity. Also, almost all European car manufacturers use a lot of "High Strength Alloy Steel" (HSAS) in their construction. Jap. cars use it too but not nearly to the extent that Europeans do. This is not as much for safety as it is for body strength. I wish Japanese carmakers would make better/more use of HSAS.

Here's where the ISx50 uses HSAS sheet:

[t3abag]

Originally Posted by tqlla3k

For BMW, the split fold rear seats are a part of the cold weather package.

As for the reason behind the non folding seats on the IS, I would assume its for chasis strength, reduced body roll, and sound insulation.

Other cars that have the split folds may still have a strong chassis.... but it would be even stronger if they re-enforced the area behind the seats.

BMW, folding seats are an option.

[Larrym9681]

My wife's MB CLK has a folding rear seat and it is quieter than the IS. Maybe the rigidity factor, I don't know.

Aloha