Hi everyone,


I own a RX8 2007 and when i drive it even on slow speed over little bumps, the steering and tyres tends to move and shift by itself on right and left. I can feel the pressure of steering struggling to maintain balance on little bumpy roads. On little faster speeds like 80 to km/hr , the car seems to float over the small bumps

The car move fine on straight roads

Can anyone guide me which part to check, whether it is due to the tyres? because i got my suspension tested and it came all clear. OR this behaviour of RX8 is normal?

 

When it comes down to ride quality issues, it generally is from suspension, tires, or alignment. Suspension will most of the time be felt in vertical travel, such as being too bouncy or "punching" hard during the strut traveling up and down. Suspension is probably not the issue here. An easy test would be to get a tape measure (being very precise) and measure across the car, from the front and back of each tire. It is easiest to do this from the front and back of the contact patches. I have a hunch your car is toed out, meaning the tires are pointing slightly outward. Small differences in toe can greatly affect your steering. In this case, you may need an alignment. Long periods of abnormal toe will wear the tires unevenly as well. However, this would be exacerbated at high speeds.

We may need a bit more information to diagnose the problem. Does it turn funny? When was your last alignment? Install any suspension parts recently?

 

My description of measuring was just bad, hes a picture to explain better.http://robrobinette.com/images/S2000...ent/toe-in.jpg

 

Yes, i changed the bushes of upper suspension arms of both sides. and yes i did the proper alignment from both front and rear, they were faced outwards but that issue was sorted out. Also i have installed new tyres. I suspect that the bushes i put in both of the upper suspension arms are not proper so thats why its creating a problem otherwise everything seems perfect here

 

and yes it turns a little funny when the road is little bumpy, otherwise on straight road turn, the turning is normal

 

Considering your alignment, tires, and suspension all check out as ok, I would be willing to chalk the difference up to feeling. Between the new tires, proper alignment, and new bushings the road probably feels different when a decent amount of force is put to it. Is this feeling strong or is it more of a "hey, this feels slightly different than before"?

As for the turning, how is it turning funny? More oversteer or understeer? More wobbly or stiffer?

I cannot guarantee anything, but your car is probably fine.

 

A little wobbly, i guess on little bumpy road turns and even on straight road bumps

 

RX8 pearl red,

You seem to be describing "tramlining" where the tires pick up a angle on the pavement and pull the steering.

I aligned my low mileage 2007 RX8 with slight tow out in front, and all the neg camber I could get which wasn't much over -1.5 deg left and right.

After that it has done the grab the steering right and left thing a lot.

I track my car so I like the instant turning it has and more balanced handling.

Also, the tires seem to wear more evenly than before so it's a win for me.

You should check tire wear with a tread depth gauge often and keep records to see what tires wear more and if they.

If the wear is out of range, just get another alignment, but you can probably just measure the toe in or out of fronts and change slightly to where you like it.

 

I think you got my problem while describing me tramlining. There is no wear on the tires as the tires are new. Now what do i have to tell the alignment guy? tell him to slightly tow out in front or tow in?

 

different question.. Do you have the factory wheels and tires on the car? It can make a big difference, sometimes good, sometimes bad.

 

Not factory tires but tires are same in measurements mentioned in the owners manual

 

Can't be his tires, they are new. But I do agree it sounds exactly like toe out behaves. Was the alignment done on factory spec? A common misconception is that 0 toe is neutral, however factory toe is set to toe in slightly. When I got my alignment done by a friend, he gave me a little spec sheet describing the old and new specs. Want to post a picture of that up for us to see? It will look something like this.

 

thanks a lot. i will show these images to my alignment guy for sure

 

Also can anyone guide me for the right tire pressure on front and rear tires?

 

Recommended is 32 psi cold front and back. You can tweak it from there if you want more understeer or oversteer. More rear pressure = more oversteer. But careful that you're not solving suspension problems with tire pressure. Set it at the recommended and see how it behaves from there.

Be careful that you don't have seized alignment bolts. With age they can seize and prevent a proper alignment. I would hope that your mechanic would point these things out, but you never know.

 

Seems normal to me....not sure what you're getting at.

Sorry

 

Can you please describe which comment seems normal to you?

 

The tire pressure on my mazda RX8 written on side of the door panel is 32 psi both front. and 32 psi in one rear and 39 psi in another rear. Don't know why 39 psi in only one tire.. anybody have an idea about it?

 

That is news to me. Maybe the little spare is the higher number. Mine are all blank. It is less than helpful.

32 all the way around is what I do. Then check tire wear occasionally.

 

Okay.. thanks, Can you send me some pics for the correct rear and front wheel alignment toe and camber settings, so that i can avoid tramlining and funny steering movements on little bumps?

My suspension and tires checked out all okay, so i guess here in my country, i need the measurements to show to my alignment guy to do a good job otherwise they will treat my car as same as Honda and corolla

Also let me know that measurement shows above in this thread are accurate enough to handle this issue... thanks

 

The 39 has to be a misprinted label.

 

i also think that.. thanks

 

It's not a misprinted label. You're reading it wrong. It has two ratings for two different loads. One for 3 passengers and another for 4 passengers plus luggage (I can't remember exactly). For the 3 passenger set up, it's 32psi in all 4 tires. For the 4 passenger+luggage setup, it's 32psi for the front tires and 39psi for the rear tires.

It doesn't denote the tire pressures of individual tires. It shows the front tire pressures together and rear tire pressures together. That's where you got it wrong

Heres a picture of the tire load sticker on my Mazda 3, as the sticker on my RX-8 is all Japanese and weird lol. The psi ratings are different (because it's a different car) but it should've give you the idea.

 

Yeah Alright.. Got the idea now.. thanks Aston.. but i really need a good alignment settings for front and rear so that my car dont fell wobbly at little bumpy roads. All the suspension checked out OK. But i have to tell my alignment guy how to do the proper alignment as there is no expert of RX8 here and you have to tell them yourself

 

Don't most alignment shops have the factory settings for every vehicle? I did the alignment on my 3 and the guy working there just selected the car's make, model and year on the alignment computer and the stock alignment showed up.

I don't have the stock alignment settings for the RX-8. Maybe another member can help you. I seem to be suffering from the same issue as you are. The steering wheel tugs from side to side when going over bumps, specially when reversing over bumps. No idea why.