what's your alignment specs

[andrew7]

I fixxed my alignment today. I guess it settled and changed a little. Around 65mph it started to feel light and squirrelly. It's now 2 degrees camber and 5 degrees caster and about 1/8" toe in. The last could later be changed to a 1/16" but with these A048 13" tires I'm looking for stability. I figured I'd start heavy, had it up to 70 and it felt solid. I need to get the fronts tires balanced too. I started at 3 degrees caster and the car changed direction by a thought, talk about sensitive. I've been swapping 13" and 14" tires back and forth and each set has a different feel so it was hard to tell. I know each car/situation is different but what is everyone else running?

trying to keep this section active:)

 

I wonder if I can finish it for the rally:confused:

 

http://www.usa7s.com/aspnetforum/upload/585630236_7 photos 073.jpg

 

:jester: its already finished, just a pic from my build:jester:

[slngsht]

That's the way my car looks right now except it's missing the front aarms too :nonod:

 

-2 degrees seems really aggressive for camber. I corded my tires with -1.5 degrees in my vette, and backed it off

 

I plan to start at -1 degree with the Rotus when I get her back together.

[andrew7]

STOP playing on the computer and START building.

 

I'm not saying your not right, 2 degrees was a guess to start at but the vette weights 3 times MY 7 would it matter? I can't detect tire wear yet, seriously.

 

 

[slngsht]

I wish I could... I'll be home free in about a month, but in the mean time, I'm working on several projects at the same time (and obviously keeping an eye here).

[scannon]

Not a BEC but I had my Caterham SV into RMSCI for an alignment last week by Nathan and Ben. Here are the settings:

 

Front

Camber -1.5

Caster 5.0

Toe In +2mm

 

Rear

Camber -1.7

Toe In 0.0

 

These are almost identical settings to what I use on my Miata except I run a little more negative camber both front and rear. Never any problems with cording the inside edge of the tires.

 

[R1 Seven]

My car is setup with 5 degrees caster, -2.5 degrees camber, and 0 toe in the front. Initially I went with -1.5 camber in the the front and that was not enough. I may acutally go with -3.0 camber up front at some point but am worried that that will start to affect braking...this stuff is fun.

 

One note to Mazda's comment. Often times people are afraid to run a lot of negative camber because of wearing the inside edges of the tires. From what I have seen, the real culprit is the toe and not so much the camber. Ultmately, yes it will wear more on the inside than the outside, but accelerated and localized wear is usually the problem that gets everyone excited. Having the right toe setings will make a huge difference in the wear.

[slngsht]

I guess usage dictates alot of this too... my vette gets alot of highway cruising miles...

[R1 Seven]

I guess usage dictates alot of this too... my vette gets alot of highway cruising miles...

 

Probably does not help at all...

 

Miatas usually have a good bit of negative camber front and rear and are pretty easy on tires with a stock alignment.

 

I once had a Twin Turbo Toyota Supra that had a funky rear alignment from the factory. I don't remember exactly, but the ballpark was something like -2.5 camber and about 1.5 degrees of toe in. I figured that the tires would wear the insides terribly. Much to my surprise, they basically wore in a cone shape evenly all the way accross.

[andrew7]

I agree my toe-in is alot. The discussion dad and I had were the old bias ply tires wanted more toe-in and radials changed that from 0-1/16" toe-in. Skips are set to .080" according to Cat specs, while Jeffs running 0 toe and driving well over the 100mph range. My 13s are more sensitive and don't "follow the road" as well as my 14" tires. Maybe I'll turn a nut and bring it to a 1/16". The A048s are a good match for a 7 but a little hard core.

 

:shocked: :smash: what a goof, they came off a Ford Spec Racer, what did I expect.:willy:

[Davemk1]

This is very interesting. There seems to be a wide range of spec's out there. I run a Birkin and the camber and toe are adjustable but the caster is for the most part fixed. There are a few small washers that can be moved around to adjust caster but they have a very limited range.

 

For some reason the Birkins have HUGE amounts of caster. This is a mixed blessing. My car is very stable at speed and handles very nicely BUT with all that caster, once the steering is turned some the camber goes through the roof. For instance when the wheels are turned to the side only 10 degrees I gain 1.2* of camber. At 20* of steering angle I have 3.5* of camber!

 

Here is how my car is set up -

 

Camber -.3 degrees

Caster 9 degrees

Toe 1/16" toe OUT

These are set with drivers weight in the seat............your numbers will change by a good bit when you put your butt in the seat.

 

You can see I run very little camber but I have no trouble at all with the tire rolling over during hard cornering. In fact if I take tire temperatures right after an autocross run I'm still a bit warmer on the inside edge. I also run slight toe out for quicker turn in. It's still one finger on the wheel stable at 80 mph. One of the benefits of all that caster and so little camber is a full contact patch under straight line braking and initial turn in.

 

I'm not the expert on this but there are a few things I've learned. To optimize camber a tire temp gauge is a very good thing. I have an infrared temp gun that cost about $40. If, in your intended use of the car (autocross and road use for me), you get even tire temps across the full width of the front tires you're doing pretty well. The other thing I learned is how much your body weight being in the seat change things. In my car I gain .3 degrees of camber on the passenger side and lose .1 degree on the drivers side once my butt goes in the saddle. I use bags of wood pellet fuel to simulate my body weight so I can load it up and then make adjustments. The last thing I learned realized is that you can run less camber when you have higher caster. Maybe this is common knowledge but it was new to me.

 

Fun stuff.

 

Dave

 

So I must apologize...........I just now noticed this post was in the Bike engined department. My Birkin is doe not ahve a bike engine. I just got excited about the geometry stuff.

[andrew7]

Hi Dave,

Glad to have you here. I know I could have put this over in the Tech section but I'm trying to keep this section active.

 

Your the second person I've heard about using a temp gun for camber adjustments. One question, How do you get a tenth of a degree? Mine only goes to 1 degree. Mine broke and I need another so I might upgrade.

 

I've heard because our cars are so light there is not enough weight to push the wheels back to center hence, caster is 5-10 degrees. I've been "sorting the suspension", last summer after the build about 40mph felt shakey. I added more caster and camber then up to 65mph started to feel loose. I made some adjustments and ran up to 70mph and it felt solid. Its a "nice- day" driver so I'm taking my time making changes. My 2 sets of wheels have a completely different feel. The 14" wheels felt stable at 65 but I was white-knuckle with the 13".

[Davemk1]

Hi Andrew,

 

I'll try to answer your question.

 

I try to determine if the tires are working properly with a temp sensor. It reads in whole degrees F. In the perfect world the tire would have an even temp across the tread surface after a given autocross run. This of course shows how the tire is being "worked" and where the pressure and stresses are.

 

I then make camber adjustments (based on tire temps across the width of the tread) and measure those with a digital protractor which reads in 1/10 degree of angle.

 

The tire temp deal is also VERY good for getting the air pressure right. Too high and the middle of the thread is hotter than the outside. Too low and the outside edges will read hotter than the middle.

 

I run Goodyear slicks front and rear.........7" front and 8" rear. I've got it so the tire temps in back are good to within 1*F across the width of the tread. In front I still run a bit hotter on the inside edge. As I recall it's about 5*F hotter inside than outside. I'd like to experiment with even less camber to try to even that out. I was running up to 1.5* camber up front and was getting a 15 degree F ( or more depending on how turny the course was) difference from outside to inside (inside being way hot). This was showing how little work the outside of the tire was doing. I in effect was using 4" wide tires up front. Not good.

 

Dinner time.

 

Dave

[andrew7]

Ya know Dave, ignorance IS bliss. I got the front tires spun balenced and its a lot better, the car feels great. You got me checking with string, levels, gages and nothings right. The rearend is twisted and shifted. My toe-in changes to toe-out on acceleration I dropped some air out of my front air shocks and my alignment changed. I just wanted to soften the ride. I might just make sure there is air in the tires and drive it, be stupid about it the whole thing and not care.:crazy:

 

I took an hour long ride today and finally got the speedo to match the gps. The wind was blowing hard today, a truck threw up several chunks of rubber, about the size of you fist and almost broke the windshield. The ride was still a blast, I am still amazed at the handling of these little cars. :hurray:

[Davemk1]

Hey Andrew,

 

I hope your lack of ignorance is better than bliss.

 

But I hear you.

 

Are your rear control are adjustable so you can set the trust angle?

 

Dave

 

 

[andrew7]

No, I was going with simple first. 4 identical trailing arms with poly bushings. I will take 2 and weld in heim joints this winter. I knew the bolts and bushing would have slop in them and that would cause some floating around with the rearend. I started thinking about accelerating and how the front lifts so I was checking that. I measured toe and it was changing from "cruise to takeoff".

I know this may sound stupid, but the car is driving great, it handles very well and the tires aren't shredding off. Should I really be concerned with a perfect alignment? If I was racing and going for every last hundredth of a second I can understand. I was thinking how much better could it get and would it matter.

I will slowly improve it but I'm more concerned with driving it. I'm sure you guys are shaking your heads and can't believe a leaf spring and air shocks could work for a 7 front suspension but it does.

[Davemk1]

Cool,

 

I think the most important thing is that the car be safe to you and others. If that's taken care of then the next most important thing is that you are having fun driving it. It sure sounds like you've got that nailed.

 

Enjoy the ride!

 

Dave

[andrew7]

I did an 85 mile ride today after changing alignment again and the ride was good. Saturday, I was at Carlisle and looking at a record setting Busa-Rush right hand driver, its caster was measured in inches. It looked like 30 degrees and the other cars there had steeper angles as well. I was thinking with the light weight of being a BEC, about 250 lbs per wheel maybe the caster should be higher. I made it 8 degrees.

I had a measurement discrepency, the ball joint mounts measured 4 degrees but checking the rim they were 1 degree. The reason is during my build I used a drill press instead of a mill and the mounts were not all identical. So I have 1 degree camber now. I then lessen the toe and its now 1/16 total in. The car drives dead straight at 65 and handles the curves by thought, its getting closer to perfection.

[slngsht]

Cool Andrew.

 

As soon as my final bolt hardware comes in, I'm going to take an initial crack at the setup. The high caster idea seems to make alot of sense.