Alignment changes with wheel/tire size

[utmorpheus]

Does the car need to be realigned with the change from stock to compensate for a different(in this case 195/50-15) wheel and tire? I thought that it would be a 'no' but after putting 6k miles on my RE-11a tires and going to rotate them front to back yesterday the outside edges of both front tires are SEVERELY worn compared to the inside edges. I can't see both fronts wheels having alignment that is that perfectly symmetrically out of spec. I do corner hard. All the time. The world is my autocross course, and I treat it as such. When I took it to have the alignment checked Firestone said they cannot attach the alignment hub to the wheels (Konig Helium) because the RE-11a stick out past the lip. They said to put the stockers back on to do the alignment.

I'm concerned that if the stockers are put back on, and the car is aligned, it's going to do the same thing to the evenly-worn rear tires once I swap back. So my two questions are 1) does tire/wheel size affect alignment or is it strictly suspension geometry changes that affect it and 2) does anyone have alignment specs they are willing to share that will reduce the heavy outer edge wear on the front tires from hard cornering?

Forgive me as I know nothing about suspension settings, alignment, etc. Haven't gotten to that level yet.

 

[okvol]

It shouldn't change the alignment, but you need to find a shop that can check it with the RE-11a's on the car. Or, do what I did: buy some Jeggs Toe Plates and set your toe-in yourself. You can get the kit for less that $80, cheaper than one alignment around here.

I put my toe just a little outside of 0 (1/16" difference toe-out). Shops will set it often much past this, and your tires will wear more. Those Bridgestones are low mileage and grip hard, and will show the wear quicker.

 

[utmorpheus]

It shouldn't change the alignment, but you need to find a shop that can check it with the RE-11a's on the car. Or, do what I did: buy some Jeggs Toe Plates and set your toe-in yourself. You can get the kit for less that $80, cheaper than one alignment around here.

I put my toe just a little outside of 0 (1/16" difference toe-out). Shops will set it often much past this, and your tires will wear more. Those Bridgestones are low mileage and grip hard, and will show the wear quicker.

Okay, can you put this into "I know nothing about alignment" terms for my brain? More specifically, what would be an acceptable change off stock values to reduce the wear I'm experiencing.

EDIT: Okay, after looking up terms, would I not want to add negative camber in the front? Or will putting a toe-out closer to 0 take care of the wear?

 

[jasyatz]

Please don't take this the wrong way. I'm all for teaching people how to do things on their cars, but alignment is not something you want to play with unless you have either, the right tools, the right knowledge or both. If you have enough skill, you don't need the best tools, but you do need an immense working knowledge of how a tiny adjustment can have huge effects on the handling of the vehicle. One wrong adjustment, and not only will the car have very poor handling characteristics, it could be dangerous.

Leave it to the professionals, or at least, the well trained amateurs.

In more simple terms, and to answer your question, it depends on your goals. A vehicle is a series of design compromises. Think of it as a see saw. On one end, you have ultimate handling. One the other is ride quality and durability. Somewhere in the middle is street performance. You have to determine where YOUR priorities lie on the scale and have the technician set up your vehicle as to what you want.

A no compromise alignment for Autocross or track days burns tires off the car in 1 to 2 years. But since tires change just about very year, this is an acceptable practice to value tires as a consumable. Whereas a street driven vehicle that never sees competition will get a very neutral alignment that improves safety, reliability and preserves tire wear and fuel mileage.

Somewhere in between there is you.

That being said.

-1.5 camber on a lowered street car gives relatively good handling characteristics, reasonable tire wear with a slight hit to highway manners but a massive increase in FUN! Keep your front toe around the zero neighborhood to minimize tire wear if that's a concern, or go 1/8" out if you really want the car to turn in well. This combination however WILL lead to an expenditure of cash on tires biannually.

Please don't stop asking questions, but good alignment techs can make an ok car great. Poor techs such as the ones at the chains and box stores can ruin a great car. Choose wisely.

 

[jasyatz]

After re reading your first post, I actually answered number 2 above. As for number 1, you can have the alignment done with the steelies on it. If your Firestone can't get their equipment to mount on the Heliums, chances are they are being lazy or don't have the right equipment or knowledge. The Re11s run wide, but there are "fingers" that they make for the aligner sensors to grab the rim edges on the outside for just this purpose.

I have a Hunter C111 in my home garage right now. I've aligned everything from mom and pop Camrys all the way up to Gt3s and NSXs. It's all in the time you want to spend to do it right. My equipment is not fancy, but if you've got less than a 19" rim, I can do your alignment. I could do 20's and up with another adapter on my sensors, but I choose not to buy it. I still have not turned down a customer/friend yet. after 20 years doing this. Unless your s*** is frozen or busted, I can make your car what you want it to be...

This is the type of guy you want touching your car. If your Firestone guy isn't willing to do this for you, you need to find another Firestone, or better yet, a small Mom and Pop shop with a cool car parked out front that belongs to the guy that will become your best friend when it comes to setting up your car. I worked for a dealership that allowed me to be that guy for a long time. New owner came in and prohibited me from being that guy anymore, so I left. I bought a machine and now I do it my way, the right way.

 

[eyeballs]

With h&r camber bolts I can get close to -2.0 degrees camber up front. I would try that with zero toe and see how you like it. And flip those tires around to get more use from them. I've personally gone (on another macpherson car) up to -2.5 degrees without seeing inner shoulder wear. And sit in the car when they align it for best results.

 

[flatlander937]

Few things:

If you drive like an ass everywhere... You will wear the outside edges in front. If you drive aggressive, you need a more aggressive alignment(namely more camber).

Rotate every 3k with stickyish tires at minimum. I rotate after every event. So like every 500-800mi for me. They have maybe a 15-20k life at best, you're not doing any favors by going longer distances between changes.

And last: check out my how to for checking and setting toe at home. Heed Jeff's warnings but set to zero toe and you'll be good.

 

[utmorpheus]

I was so used to the absurdly even wear of the Miata running Star Specs, that I was just used to rotating the tires with my oil changes. I can see that is not the case with the 2. I think my best bet is going to be picking up some camber bolts and hunting down an alignment tech that knows what they're doing-which is harder than it sounds in my area. Too bad you're all the way in Jersey, Jeff, I could use some schooling on how these changes translate to real world handling. No matter how much I read on the subject it doesn't seem to click until I can feel the affects.

 

[jasyatz]

I was so used to the absurdly even wear of the Miata running Star Specs, that I was just used to rotating the tires with my oil changes. I can see that is not the case with the 2. I think my best bet is going to be picking up some camber bolts and hunting down an alignment tech that knows what they're doing-which is harder than it sounds in my area. Too bad you're all the way in Jersey, Jeff, I could use some schooling on how these changes translate to real world handling. No matter how much I read on the subject it doesn't seem to click until I can feel the affects.

I actually recommend people come and hang out when we do their cars. Sure I have ballast to out in the seat, but it's better when they get involved. They get to "feel the love" that goes into getting it just right. Chances are, you have a guy like this close to you. You need to ask around at local track days and Autocross events. There's one in every town.

 

[eyeballs]

Realize due to the differences in suspension design between the 2 and the miata, the 2 actually looses camber during cornering which is why you may need to run more than you had on the miata. A larger front sway bar will help with dynamic camber loss as well. The downside is the negative camber and the front bar make it harder to put power down since there is less available straight line grip.

 

[jasyatz]

Yup.. you hit it right on the head. That's the balance I'm trying to find. Stiff enough, but not too stiff. You need a bit of roll to get the tires to hook up square, but not too much that it lifts the inside tire, and kills off corner acceleration.

 

[utmorpheus]

I never set the alignment of the Miata. I just handed the shop FM's specs and said do it. Haven't changed it since - or really driven it for that matter.

If the car looses camber when cornering I would offset that by introducing a more negative camber angle? Is this possible stock or are the camber bolts needed to get this level of change? I don't want to add too much to the car because I'm not sure if I'm going to still own it in a couple months. I may sell it off for a Mazdaspeed 6 or turbo Miata. (or Honda NM4, so sexy)

 

[jasyatz]

Not possible stock, but depending on wheel width and offset, can get more camber with bolts. I rubbed the strut housings with bolts on the 225/45 Hankooks. But around -2.0 seems to be a happy number for cornering grip and wheel spin mitigation.

Fast Mikes alignment specs are pretty much perfect for an ES Miata. I liked to got max camber up front and then add -0.8 to the rear for perfect balance. 1/16" in for a street car toe in the rear and an 1/8" out up front.

 

[Zach@DDMWorks]

Sorry to be overly detailed, but you don't always loose camber with a mcpherson front end. It all depends on the angle between the LCA mounts and the mounts for the upright. If the angle is <90 degrees you gain camber. If it is >90 then you loose. Now where does the car stand when at different ride heights I haven't looked into that. Also it doesn't gain as much as a good double wishbone.

Also yea if you change tires your alignment should not change, but if something was off you might notice it more with better tires. Partially because better tires will wear faster, and if there is any loading from toe or camber it will be higher since the tires grip more and have stiffer sidewalls so they will have more grip/scrub with a small slip angle.

 

[jasyatz]

Sorry to be overly detailed, but you don't always loose camber with a mcpherson front end. It all depends on the angle between the LCA mounts and the mounts for the upright. If the angle is 90 then you loose. Now where does the car stand when at different ride heights I haven't looked into that. Also it doesn't gain as much as a good double wishbone.

Also yea if you change tires your alignment should not change, but if something was off you might notice it more with better tires. Partially because better tires will wear faster, and if there is any loading from toe or camber it will be higher since the tires grip more and have stiffer sidewalls so they will have more grip/scrub with a small slip angle.

Details are good! What was the motion ratio you (or was it Tony) calculated for the front of our cars? One of you had a crazy spreadsheet going into specific detail regarding ideal spring weight, motio ration and unsprung weight at the front corners. I went with my gut based upon event results and "feel" from the bottom seat cushion on the left seat.

 

[eyeballs]

Sorry to be overly detailed, but you don't always loose camber with a mcpherson front end. It all depends on the angle between the LCA mounts and the mounts for the upright. If the angle is <90 degrees you gain camber. If it is >90 then you loose. Now where does the car stand when at different ride heights I haven't looked into that. Also it doesn't gain as much as a good double wishbone.

Aha! Thank you. I remember reading about that before and even saw a nice diagram explaining it but can't remember where. A good example of why you build your suspension, and I buy something someone else built.

 

[Zach@DDMWorks]

Tony has one and I have a big one with 8-9 different cars on it. The front is like 0.98 or something. Just the effect of the angle of the shock. Also there is a big one available online. I forget how to find it. I have it saved somewhere as well. My sheet is simpler and get you 98% of the way there.

 

[flatlander937]

Ignore rear spring rate and motion ratio. The motion ratio is correct for the shock, not spring. IIRC its like a .97 m/r at the spring. The rear spring rate is really a 450 spring, adjusted to be on the same motion ratio a shock since the calculator assumes they're on the same point.

Google Autocross to Win to find the site.

 

[jasyatz]

Thanks. now I remember having that chat with you. Same conversation, 3 different places.

 

[Traum]

Google Autocross to Win to find the site.

Here you go -- Autocross to Win

http://farnorthracing.com/autocross_secrets.html