nadidlab

I'm considering a used car purchase and trying to decide between an M3 convertible and and SC430. I managed to drive both models back to back over the same roads on the same day. They are both fine cars. The lexus is more luxrious with a more compliant ride and the BMW has more raw power and road feel. I was prepared to be faced by those differences. One thing that surprised me was something in the sc430 that seemed to me to be chassis flex. In driving on a high speed turn, the steering wheel, windshield frame, and wheels all felt like they were moving in different directions at the same time. It wasn't the smoothest road, but it wasn't like the surface of the moon either. The most unnerving feeling was a wobbling motion in the steering. It felt a bit like the tires were rolling back and forth on the sidewalls, wavering in the midlle of a constant turn. I don't think I was driving hard enough to be rolling onto the sidewalls. It was so noticeable that I was a little bit unsure of whether I was really in total control of the car's direction. In comparison, the M3 on the same curve at about the same or perhaps higher speed did not exhibit the same characteristics. I have a few questions:

1. Is this typical? I ask not to be impolite, but it shocked me a bit. I've driven a few convertibles: Miata, RX7, SL560 etc, and was surprised by the amount of flex I noticed, if that was what it was.

2. Could it be run flat tires causing uneasy steering? I found some info in the forums on this, but am not sure if the tires on the car I drove were run flats.

3. Could chasis flex be reduced with strut tower braces or other modifications?

I'm not necessarily looking for a hard core sports car, but I do want to feel confident and in control. I wasn't driving at terribly unreasonable speeds. Any help would be appreciated.

Nad

rominl

iTrader: (4)

welcome to clublexus!

yes, the lexus is definitely more "flexible" in pursuit of a better and more comfortable ride. the down side is body flex which i sometimes feel the same as you as well. especially when you drive the m3 which is so performance oriented. it's not surprising that the tires cause part of the problems too, those runflats have ZERO handling, you can easily slide on them (they hardly flex coz' they are sooo hard). strut tower bar does little to handling. get good coilovers and sway bars for the car and that will improve the handling tremendously

nadidlab

Thanks for your response.

Would adding stiffer springs, struts, and sway bars just make the chassis flex that much more evident?

tonydt1g3r

yes, big difference

rominl

iTrader: (4)

let's wait for lee (pearlpower) to comment, he's the guy

Pearlpower

iTrader: (2)

I do notice little chassis flex in the car. Some -yes-especially when going over bumps at angles. That stated I have had a couple of convertibles such as 968Cab and a Vette (C4). The 968 and SC430 are about on par with chassis flex with the C4 a distant last. I have been in a M3 Cab as well and did not notice much chassis flex but to be honest I was not paying that much attention to it as much as I was the lack of refinement, interior, etc.... I have yet to be in any convertible that does not exhibit some flex at the extremes yet the SC compares favorably with the ones I have been in. Most likely because I do not notice that much flex. Flex-yes-but not a Benz CLK flex.
There are several cross braces under the car that could be checked to ensure that 1) they are there and 2) all bolts are tight and none are bent as they tend to get hit by bumps or road debris.

nadidlab

Thanks to all.

Clarification for Tony:

when you say "yes big difference" do you mean yes you notice the flex more or yes big improvement in the amount of flex?

paul_k

If its more than 4 years old or 60,000 miles it may be suspension wear.The rear lower control arm bushes were shot on my Supra at about this mileage and this seems to be common on the GS 300 too. Handling was quite wooly and rocked from side to side on some surfaces.

I wonder if this is a general Toyota issue...


Paul

veilstylez

well as a previous M3 vert and a sc430 owner I will say...they are both completely diffenrent cars. M3 w/ SMG is a more sports car feel...you feel the road and WAY fun. But the SMG is very jerky sometimes you just want an regular auto tranny. The SC430 is more a luxury cruzer no sports feel like the M3, but VERY VERY comfortable. Will handle better with upgrades. If your looking looking for a sports car get the M3 but if your looking for comfort not really a sports car feel get the SC. Ill tell you sometimes I really miss the drive of an BMW that the SC doesnt have, that raw sports car feel with smg paddles on the PCH with the M3 exhaust note. My next will be a 997 S for sure. I sold my M3 for the SC so the choice is yours. Although it took about 2 months to get used to the bouncy crapy suspention on the SCs and I hated it, but now I just like the comfort of the SC for me. I think if i never had the M3 the SC would feel sporty to me but it just doesnt.

hipendicul

I had a 99 Mcoupe for my last car and that was supposed to be the stiffest car that BMW had produced at the time. What surprised me was that how the car kept getting more loose as time went on. Where as my 93 Mr2 was a T-top and didn't feel super stiff when I got it. But the Mr2 never loosened up more, where as the BMW did.. So even tho I feel quite a bit of chassis flex in the SC, its a Lexus and it probably won't get any worse. Besides, my interior squeeks very little and I have almost no rattles and the car handles like its on rails (Shocks made a huge difference).

Oh and with the top up, I feel about half of the chassis flex. The car feels pretty stiff to me as long as the top is up.

etzel

i don't think there's alot of flex in the sc considering that it's not calibrated to a an m3 like car. but i notice that with the top down the ride is much more compliant. the OP brings up a good point however regarding the effect of stiffer springs, braces, etc. i have an 05 with daizen sways and tein cst (edfc) and am considering more robust options. are there any to consider other than those already written up? does the stiffer setup adversely stress the car's current bracing?

Cruizing

The SC430 with the Daizen sways and the CSTs is pretty good. You can add the Toms braces though I suspect they won't add much. You should check the upper and lower arms. I just replaced the uppers as they were getting loose after 46000 k. Helped a lot. The run flats over rough pavement are non-compliant and contribute to the disjointed feel. I think the big difference between the M3 and the SC430 is the torque and low end acceleration that the 6 cyl has over the SC. Also it is very easy to find aftermarket parts and advice from experience for the M3 to modify if desired. For example there are probably less than 1/2 dozen SC430 in the world with FI but many M3s. But you do get a hard top convertable which is very nice. The other option is to wait for a M version of the new hard top convertable 3 series.