v_therussian

This past Saturday I've went to a meet in the Pocono Mountains and really drove my car.

I did two things before the drive that I have not done previously:

1. I put on non-RFT Contis on my rear wheels

2. I over-inflated the fronts to 34psi


Let me start with the non-RFTs. In a nutshell, I have no idea why I didn't do this sooner - the non-RFT tires in the back did not make my car handle any worse. As a matter of fact, their compound is flexible, compared to the RFTs, which made the rear stick to the asphalt more, actually. Now, my only testing equipment was my brain, so I can't provide any figures as to whether there's an actual difference. But I can tell you that the car does handle better with at least the rear wheels being non-RFT.

Ride quality discussion is really unnessesary, as everyone knows that RFTs are spine-killers, but I should note that the non-RFTs are MUCH-MUCH-WAAAAAAY MUCH better. They are the missing link in the stock e60 configuration IMO - that's how much I like these. And also, mind you these are not really "performance" Contis - I just bougtht a couple of Contis off craigslist especially for this run, but I think they're staying and my RFTs will have to hang out in the garage for the time being.

Which brings me to my next point - over-inflating the RFTs. I overpumped the fronts for better traction on the drive, but it actually rendered a better ride. The reason why it works that way is actually painfully simple: since RFTs have 3x as stiff sidewalls, when the RFTs are under-inflated, they ride a lot stiffer than regular tires. But when you overpump the RFT a littlle, their contact patches - which is the softer part of the tire - rely less on the sidewalls, because the contact patches "buldge out from underneath" the sidewalls more.

*excuse my amateur terminology in some places - do feel free to correct me - whether you feel I'm mistaken conceptually or linguistically

PS I like running the RFTs in front still - I feel that its a great compromise between RFT and non-RFT.

BMRMEUP

That's interesting. I've been considering stiffer swaybars and/or coilovers for my car, and thought perhaps just changing out the back swaybar would reduce the roll without altering how the car handles bumps in the road. You've got just the opposite here, stiffer on the front. Hmmmm... obviously have more reading to do. Do you have issues with body roll with your xi, or have you done some suspension mods like C and Dr.Lev?

v_therussian

My suspension and rims are totally stock. My rear suspension is almost all new though - in February my car was hit while it was parked during a snow storm and about 80% of the rear suspension parts actually were replaced with new.

That said, I do have to say the car does roll more than an "i" car, naturally. Though I've yet to break traction on this car - RFTs or not, my car just refuses to misbehave. But I'm not entirely convinced that Xi has worse handling, actually - after running the twisties and being able to just about keep up with the 550s, I have to attribute that mostly to the suspension and AWD. I'm not sure how the sway bars affect the handling - I'd imagine, if you don't go on negative camber turns in wet weather, you'll only know of the positive sides. But that added stability in turns means also that you'll break traction on your tires sooner when the weight and acceleration forces overpower the traction. As opposed to a softer suspension, where the car will sway, but the rubber will stick longer.

All depends on what you want. I personally probably would get the sway bars and lower mine - if I weren't selling it.

BMRMEUP

Mine also holds the road very well, so it's more an issue of comfort I guess. My understanding of how a swaybar functions is that it holds the wheel in contact with the road. A stiffer swaybar on the front would compromise some of the independence of the wheels, the stiffer it is, the more it would function like a straight axle over bumps.

Anyway, thanks for the input. Sorry to derail your thread.

Back to the topic of runflats vs. non-runflats..........

sdg1871

You probably would not want to lower a car much if you were going back on Snow Hill Road given that we have one front bumper scrape on a non-lowered 550i Sport (not me!).

v_therussian

I would NOT know who that scraped bumper belongs to but what a dumbass

CWS530

I've never owned RFTs, but I've driven on them numerous times. They suck. I have a spare and an AAA card.