Anyone running 18x8" rims... [Archive]

bacarl

10-14-2008, 12:00 PM

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

10-14-2008, 01:23 PM

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

10-14-2008, 01:23 PM

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

10-14-2008, 01:33 PM

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

10-15-2008, 01:02 AM

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

10-15-2008, 02:26 AM

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

Are the cars stated aligned properly?

bacarl

10-15-2008, 08:34 AM

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

Silver Ecstasy

10-15-2008, 08:50 AM

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

10-15-2008, 02:22 PM

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

10-15-2008, 02:33 PM

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

10-15-2008, 03:43 PM

lol i have 18x8's no noticable difference

AutoXRacer

10-15-2008, 03:43 PM

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

10-15-2008, 03:51 PM

... 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

10-16-2008, 12:26 AM

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

10-16-2008, 05:25 PM

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

10-16-2008, 05:29 PM

might be the tires =)

lowpro35

10-16-2008, 05:47 PM

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

10-16-2008, 06:38 PM

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

10-16-2008, 06:48 PM

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

10-17-2008, 09:57 AM

bacarl

10-17-2008, 10:25 AM

Yeah I thought of that too. People are getting up there with these cars, 300-350whp and I'm the only one complaining! haha This is a fast car, but it gets so twitchy under power over rough stuff that it can't be driven fast sometimes :(

My buddy and I dialed in ~0.15* of total front toe-in last night, and it actually did help. Typically toe-in increases stability and decreases steering response, which is what I want. The car was toe'd out before, so this made a difference. The true test will be a particular strip of freeway that I drive on to work come Monday.

bacarl

10-17-2008, 10:28 AM

Silver Ecstasy

10-17-2008, 11:06 AM

The true test will be a particular strip of freeway that I drive on to work come Monday.

If you're talking about i275 between i96W and i96E, it won't make a difference. Thank John Carlo Construction for that. They won the bid through the state to produce a low grade grooved cement. It'll hold up better than asphalt and won't develop huge dips where water sits and people hydroplane, but in the dry your tires will follow the grooves uncontrollably.

mazdaspeedster3

10-17-2008, 11:13 AM

And Mike they gave a lifetime warranty on that job.

Silver Ecstasy

10-17-2008, 11:40 AM

It definitely is holding up really good. I personally don't have any complaints with the grooves, but any aftermarket tire i've ever ran hits those grooves.

They need to re-pave i275 south of i96 east. From all the weight put on those roads, water just sits in those grooves and you hydroplane from one end of the freeway to the other.

ThreeEdgedSword

10-17-2008, 12:12 PM

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

Going by tire companies' specs, 8" wide is about as small as they recommend, but you're probably right about them ballooning out. Wonder if 225/45s would be more stretched out on RX8 wheels enough to solve the rubbing issues they're known to have.

Either that or I'll just have to get over being OCD and go with the 235/40's - if I'm changing tire sizes I'd just rather be slightly oversized rather than undersized.

Mid_Life_Crisis

10-17-2008, 04:01 PM

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.

My offset is 52, which centers the tires pretty much in the stock position (equal increase inside and outside) which I believe should have the minimum effect on steering geometry. What pressure are you running in your tires? If they are the reinforced variety, Falken recommends 5 or 6 psi over the stock pressures. Not sure how much difference that would make regarding what you are experiencing, but it is something to check.
Not at all surprised that torque steer feels heavier. With the increased traction, instead of the tires spinning, they bite down and haul the car, so you get torque steer. Of course, my wheel/tire combo weight ended up about the same as stock, which may also make a difference.

bacarl

10-20-2008, 04:57 PM

If you're talking about i275 between i96W and i96E, it won't make a difference.
Ha, I know what you're talking about with 275. But the road I'm talking about is Southfield Fwy north of Dearborn. The grooves don't bother me as much as the bumps and patches on Southfield that literally throw the car off course.

... What pressure are you running in your tires? If they are the reinforced variety, Falken recommends 5 or 6 psi over the stock pressures. ...
I've been running stock pressures (34F 32R) on the street. I remember seeing your posts about reinforced Falkens so I tried running ~40psi for a while but the ride suffers too much. I haven't actually been able to determine for sure if my FK452's are reinforced or not.

I agree about the grip worsening torque steer. Some torque steer isn't a problem, but my real issue here is that if the car goes over a bump or asphalt patch under power, it jerks violently in the direction of the bump.

bacarl

10-20-2008, 04:58 PM

If any of you Michigan guys are at the fun run on Saturday I would love to ride around with one of you for a while and see how your cars handle compared to mine...

Quiksilver05

10-21-2008, 04:04 PM

Hmmm I have the rota Torques in 18x8 48 offset. Im gonna get them put on sometime this month so I'll see if there is any difference as well. Anyone know if I can just use up the stock tires on the rota 18x8 without any problems??

strytnyne

10-21-2008, 05:27 PM

im using oem tires with my torques no problem, very mild stretch, just no rim protection at all haha

bacarl

10-21-2008, 09:12 PM

You'll have to let me know if your ride quality or anything suffers with those, QuikSilver. But strytnyne said he's fine with that set-up...

I've autocrossed with a guy running 18x8 Torques and he says his ride sucks too but he's got 235/40 Azenis.

Quiksilver05

10-22-2008, 07:56 PM

Saitech

10-23-2008, 04:29 PM

You'll have to let me know if your ride quality or
I've autocrossed with a guy running 18x8 Torques and he says his ride sucks too but he's got 235/40 Azenis.

Close...245/40. :D Ya, the ride quality is crap compared to the stockers. I did not run the stock tires on 18x8 so I can't comment on that.

There is also significant amount of howling and tire noise once you get close to the wear bars on the azenis.

bacarl

10-23-2008, 04:44 PM

Hey, thanks for chimin' in man!

Do you ever run your Azenis on the street? Notice any of the weird twitchy stuff I'm talking about?

See you this weekend on Belle Isle...?

AutoXRacer

10-23-2008, 06:08 PM

Close...245/40. :D Ya, the ride quality is crap compared to the stockers. I did not run the stock tires on 18x8 so I can't comment on that.

There is also significant amount of howling and tire noise once you get close to the wear bars on the azenis.

Performance tires are always noisy, especially close to wear bars... I think the Azenis are the noisiest...

I'm running 18x8 RX8 wheels and the ride quality is not as soft as stock, but better in terms of firmness...though I am running 225/40/18; I'll be upgrading to 235/40 which will increase sidewall height slightly

Saitech

10-24-2008, 12:24 AM

Hey, thanks for chimin' in man!

Do you ever run your Azenis on the street? Notice any of the weird twitchy stuff I'm talking about?

See you this weekend on Belle Isle...?

Ya, I def do. I thought it was the wider rims but my friend who is running on 215 azenis on 7 in wide rims noticed the same too. So I am guessin it's the stiff sidewall on the azenis.

Wish I could come out to belle isle, 4 exams next week. (notcool)

Btw, I was classed in CMT last time per request. I think we technically belong in CMT, not BMT. But if you want a trophy, do BMT.

Saitech

10-24-2008, 12:28 AM

Performance tires are always noisy, especially close to wear bars... I think the Azenis are the noisiest...

I'm running 18x8 RX8 wheels and the ride quality is not as soft as stock, but better in terms of firmness...though I am running 225/40/18; I'll be upgrading to 235/40 which will increase sidewall height slightly

Yea, i agree, I stopped daily driving on azenis after a couple months, just too noisy and stiff. I plan on having a dedicated set of rims and tires next season. I have all winter to decide tire and size.

jon619

10-24-2008, 12:47 AM

I'm running 18x8 RX8 wheels and the ride quality is not as soft as stock, but better in terms of firmness...though I am running 225/40/18; I'll be upgrading to 235/40 which will increase sidewall height slightly

Actually, it'll reduce sidewall height slightly. I plan on doing the 235/40/18s as well as soon as I burn off my stock tires.

215/45-18 3.8" 12.8" 25.6" 80.5" 787/mi 60MPH 10000mi N/A
235/40-18 3.7" 12.7" 25.4" 79.8" 794/mi 61MPH 10085mi -0.8%

AutoXRacer

10-24-2008, 07:59 AM

Actually, it'll reduce sidewall height slightly. I plan on doing the 235/40/18s as well as soon as I burn off my stock tires.

215/45-18 3.8" 12.8" 25.6" 80.5" 787/mi 60MPH 10000mi N/A
235/40-18 3.7" 12.7" 25.4" 79.8" 794/mi 61MPH 10085mi -0.8%

I was comparing them to the 225/40/18...the 235/40/18 should be slightly taller...

bacarl

10-24-2008, 03:12 PM

... Btw, I was classed in CMT last time per request. I think we technically belong in CMT, not BMT. But if you want a trophy, do BMT.
Judging by your times at the last event we were at, you could trophy in BMT no problem!

Yea, i agree, I stopped daily driving on azenis after a couple months, just too noisy and stiff. I plan on having a dedicated set of rims and tires next season. I have all winter to decide tire and size.
I think I'll be in the same boat. I can't drive on these the way they are.

Aren't the Azenis already your dedicated set? Or are you gonna put DD tires on the Rotas and pick up a whole new set for racing?

Saitech

10-24-2008, 04:44 PM

Aren't the Azenis already your dedicated set? Or are you gonna put DD tires on the Rotas and pick up a whole new set for racing?

I am selling the 18x8 torques and picking up 17x9 rpf1s (16lbs). Shorten my gearing so I can use 2nd and 3rd, not to mention some extra rubber.

I'll stay with stock rims for DD, I might paint them a darker color over winter so I don't have to clean the brake dust so often.

In CMT, it's an eye opener when you get beat by a N/A neon and a civic by over a second consistently. They are my benchmark, sadly. lol

bacarl

10-24-2008, 04:54 PM

Well if it's the Grape and that white hatch, those cars aren't slouches. Neither are the drivers, I don't think, esp the Grape's.

bacarl

10-24-2008, 04:54 PM

I thought that Civic ran R-comps?

Saitech

10-24-2008, 06:21 PM

I thought that Civic ran R-comps?

Civic in CMT is the orange/rust/primer, very good driver. I think the co driver is a natl trophy winner. The grape is fast and completely dialed in, very good driver too.

The civic runs on a set of season old bridgestone re01rs, they look like rcomps b/c they are so worn, lol.

If I can't beat them next year, I might as well quit.