Anyone running 18x8" rims...

[bacarl]

I'm curious if people are getting negative effects from their 18x8 wheels.

I have Rota P1's which are a 19lb 18x8+48mm wheel with 235/40R18 Falken FK452 tires. I installed this set-up over the summer and immediately noticed that the car torque steered worse and tramlined worse (tramlining is where the car wants to follow the shallow ruts in the road). Also the ride quality got much worse, to the point where a ~1" bump or frost heave can throw the car off course. I thought I could live with it but it's getting to the point that I'm really sick of it - it's literally dangerous and scary to get on it because the car is very twitchy and doesn't feel planted.

I thought it might be mainly the tires, but aaronc7 also has 235/40 FK452s and told me he noticed no change from stock. However he runs an 18x7.5" wheel. Saitech told me that his ride went to hell too when he installed his 18x8's (Rota Torques so I'm assuming a +48mm offset) and 235 Falken Azenis. So I'm wondering if the wheel is the culprit. I know a little about bump steer and scrub radius so I'm aware that those could affect things, I just didn't think it would be so noticable. I'm going to try dialing in a little toe-in to help with roll understeer and stability.

Just looking for some feedback to see if you guys have experienced this or have a fix in mind.

 

[Moultese]

Is your car properly aligned? You may want to add some camber if you feel your car is too much to handle. I would think that a wider wheel would make the car much more stable and feel more "planted."

 

[MikeHTally]

I'm thinking mine has changed in that manner as well. 18x8 RX8 wheels and Yokohama YK520s in 225/45. The car does feel less stable especially braking in turns. I've monkeyed a bit with tire pressures but without much change. Not sure if the torque steer is different, but it does seem like it tugs a bit more. As for any tramlining, the roads I use don't have much rutting.

This is an interesting question. Guess I could have my RE050s mounted on my stock wheels to see the result...

 

[mazdaspeedster3]

I am running those YK520's on my stockers, you sure you dont mean 225/40? It is my winter set up and I have no problems with them. My after markets are 8" rims with the stock tires on them (have the Spec2 waiting for spring) and dont have any problems with those either... Maybe it is the 235 tire size that is throwing it off?

 

[trdsw]

I think it has something to do with wheel weights. When I switched to my OZs hats about 7 lbs per corner I felt the car was more nimble but it also jarred a little more easily

 

[Leshok]

Wider wheel will have a lever arm effect, and also change scrub radius.

Are the cars stated aligned properly?

 

[bacarl]

I haven't checked my alignment recently - it was checked about a year ago by the dealer.

 

[Silver Ecstasy]

If you're fighting the ruts and grooves in the roads, it's the tires.

I know everyones going to say i'm crazy, but when manufacturers setup a car with a specific size of tire, they do for a reason. They arn't trying to go bare-minimum of what's acceptable. TireRack and every car magazine has done some type of article speaking on how everything is designed to work as best as it physically can in the wheel and tire, from the weight to the size etc. etc.

Think about it, our cars do quite a bit with those skinny 215's. They can haul in a straight line and corner with the best of them. On the streets, that's pretty good. Cobb on the other hand, tracks their car and runs 235 all the way around on a flat track surface.

I learned the hard way that with larger tires, they will start to individually get a mind of their own at times. My Trailblazer SS had 255 series 20 inchers, and they'd follow every groove or path cut out in the snow. All 4 wheels wanted to go in opposite or independent directions. I fought that thing in the snow bad.

Hence, I will be sticking to stock size when I replace my tires.

 

[Hot Shot]

I have Rota P1's as well with the OEM tires on them. I do notice a bit more torque steer and some wandering on the road. The torque steer I can understand with a slightly wider rim and in your case, tire. You have a larger contact patch and more grip, so it can be expected. As far as the wandering, I'd suggest an alignment as well. I'm getting a bit of the same, but am lowered on RM springs. I'm in need of an alignment.

 

[justanothermp5]

i have 17x7.5 on my p5 and those things make me feel like i have no control over the car on bumpy roads
the car just jerks all over the place, alignment is all good but the car pulls to the right no matter what

not sure but the only other thing is the tires so i have to get those replaced and ill see if that helps

 

[strytnyne]

lol i have 18x8's no noticable difference

 

[AutoXRacer]

I have 18x8 RX8 wheels with 225/40s with no issues...its actually my race set. I am increasing the size to 235/40 on my next set since the rim is too big/wide for the 225/40.

Seems like your car needs an alignment...

MS3 loose their front alignment quick...especially the factory setting.

 

[bacarl]

... everything is designed to work as best as it physically can in the wheel and tire, from the weight to the size etc. etc. ...

QFT.

More time and attention go into developing a suspension than most people can fathom. I know this because I help develop some of it. But sometimes things can be improved because we're more willing to spend more money on our cars than Mazda was, on things like mandrel bent downpipes and expensive air filters.

I do get pretty nervous messing with suspension geometry, for instance lowering a car messes up your shock travel and spring rates, and will probably make the car handle worse, even if it "feels" more planted. I got the +48mm wheel since it's close to stock offset, but apparently not close enough. The extra wheel & tire width only add to the havok.

The thing is, as cars are modded, settings can be adjusted to compensate. The key is just knowledge. I'm gonna try to pick some brains and get my situation improved.

i have 17x7.5 on my p5 and those things make me feel like i have no control over the car on bumpy roads
the car just jerks all over the place, alignment is all good but the car pulls to the right no matter what

That's what it feels like to me exactly.

Also, make sure your tire pressures are good if the car pulls for no apparent reason...

 

[Young Roids]

Ya I think it might be the offset. I got some enkeis that weigh 17lbs and are 48mm in a 7.5 width with stock tires and I notice the torque steer increased as well. Although for winter I have some 205/60/16 on 45mm offset and they don't seem to increase the torque steer so then again it might be the width.

 

[bacarl]

Offset affects something called scrub radius which can definitely make torque steer worse. I think I just under-estimated the effect of the 4mm of offset I took away.

What bugs me though is that tons of people run lower-offset wheels and don't seem to have a problem. So it makes me think it might be something specific with my set-up. Or even just my tires....

(dunno)

 

[strytnyne]

might be the tires =)

 

[lowpro35]

my g/f is runing tenzo dc 6 with 235/40 falken ziex 912's on cobb stage 2 and the car feels and handles amazing. it's quieter than the stock setup too in my opinion

i say it's your alignment + tires maybe

 

[ThreeEdgedSword]

Speaking of tires, does anyone know if would it be possible to get away with 245/40r18s on RX8 wheels w/ stock suspension (with or without eibach springs) without rubbing?

 

[lowpro35]

245s? i think those would probably be a little too big for the RX8 wheels. i think they might balloon up from fitting on the wheels. rubbing would probably be eminent

 

[Young Roids]

Offset affects something called scrub radius which can definitely make torque steer worse. I think I just under-estimated the effect of the 4mm of offset I took away.

What bugs me though is that tons of people run lower-offset wheels and don't seem to have a problem. So it makes me think it might be something specific with my set-up. Or even just my tires....

(dunno)

I think it's just that some people don't notice things as much as other people.