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Proper Wheel Alignment

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Proper Wheel Alignment
#1
  This topic is about my 1973 Triumph GT6 MkIII
F1000RACER Avatar
F1000RACER Platinum Member Gary H
Alpine, CA, USA   USA
The subject of poor handling and proper wheel alignment came up in another thread. I thought I would share this with the forum on how I prefer to align my cars. I like to do it myself because I feel I know the cars better than an alignment guy would and frankly I do a better job at it than they do.

Corner weighting is optional, but it's like the icing on the cake to get the corners within a few pounds of each side.

Carroll Smith authored a series of books on race car engineering. He goes into details on alignment in his "Prepare To Win", great reading for those that care.

4 jack stands
bright colored fishing line 5-10 lbs test
Steel rule 1/32" / 1mm divisions
Angle finder (I have a fancy one but cheap ones work)
Some shims for the floor (make level to roll car onto)
8 foot length level or you can use a simple string bubble level
2 Plumb bobs (used to find centerline)

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OFRacer Avatar
OFRacer Mike H
Poughkeepsie, NY, USA   USA
One thing I do different is attach one end of each string to a short bungy cord. It make it easy to keep tension in the string so it doesn't droop.

mike h

F1000RACER Avatar
F1000RACER Platinum Member Gary H
Alpine, CA, USA   USA
In reply to # 1526567 by OFRacer One thing I do different is attach one end of each string to a short bungy cord. It make it easy to keep tension in the string so it doesn't droop.

mike h

Good idea from a fellow racer. Nice collection of cars I see on your home page pic. Are you a former SCCA guy turned Vintage racer?

Gary Hickman

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OFRacer Avatar
OFRacer Mike H
Poughkeepsie, NY, USA   USA
Yes, I started racing in F440 and moved to H-Production before I started running the Spitfire exclusively in vintage.



mike h



Edited 1 time(s). Last edit at 2018-04-16 04:28 PM by OFRacer.


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RiPe Richard Peetz
Sequim, WA, USA   USA
Hi,
I see that you are taking toe measurements from the wheel rim. I've seen that method used and folks measuring from the outer center of the tire circumference.

I assume the toe-in specs in the manuals are from the rim not the tire circumference, is that a correct assumption?

Of course converting inches toe-in to degrees toe-in would allow one to measure either way.

OFRacer Avatar
OFRacer Mike H
Poughkeepsie, NY, USA   USA
I like to use the rim for a couple of reasons:
1. It's a hard point, tires can bulge differently across the sidewall
2. It's flat, easier to get a more precise distance if the tape measure is square to to surface

If you're going to use the tire's surface as a measuring point, I'd recommend buying or making a set of toe plates so you'll have #1 and 2 from my above list.

mike h

TheZster Avatar
TheZster Steven Z
SAINT LOUIS, MO, USA   USA
1978 Triumph 1500 "BLK-BRY"
Just wondering....

I agree with the "measure from the rim." as tires tend to have all sorts of variations from spot to spot....

However... just wondering.... would it make sense to measure brake disc to brake disc. on the front.... wondering if that measurement would be more precise... On the other hand... we're measuring tire to tire toe in.... (where the rubber hits the road)..... so maybe rim to rim or rubber to rubber would be a better indicator.... ( to be adjusted if necessary on every tire change.)....

I'm NOT a tire/alignment guru by any stretch of the imagination...

Z

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Falkon Avatar
Falkon Al Martin
Appleton, WI, USA   USA
Doesn't the toe change when the wheels are hanging? I use a yardstick pencil and tape measure. Make marks on the floor F & R of tires. Measure distance between.

TheZster Avatar
TheZster Steven Z
SAINT LOUIS, MO, USA   USA
1978 Triumph 1500 "BLK-BRY"
In reply to # 1526789 by Falkon Doesn't the toe change when the wheels are hanging? I use a yardstick pencil and tape measure. Make marks on the floor F & R of tires. Measure distance between.

I would think so.... keeping mind... toe in... where rubber hits the road..... though I could be totally wrong.... Let's wait till a guru chimes in.... or better yet.... how about we both check out the archives... and not start a new "repeat" of multiple archived threads....

Z

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OFRacer Avatar
OFRacer Mike H
Poughkeepsie, NY, USA   USA
The wheels need to be loaded to get the proper measurements. Some people even have someone (or dead weight) in the driver's seat to get the car as close to driving conditions before they start.

mike

Manana Avatar
Manana Steve Wten
Thornhill, ON, Canada   CAN
In my mind using degrees is just so much easier to compare. Using inches always adds confusion for me; which part of the rim? (although I realize that is fairly insignificant), is it back to front or centre to front? Using a 15" rim changes things too. smiling smiley

I do things a little differently, still using string, extending the wheel angles in front (or back) of the car and then take measurements between them at two locations, then SOHCAHTOA it.

Although I'd never argue that tires can bulge differently, it' never been an issue for me.
One day I'll make a couple jigs that I can clamp to the rims.



Steve
http://stevew10.wix.com/spit16

14GPDJENGINEERING Avatar
Silver Spring, MD, USA   USA
Toe is normally defined as at the rim. I think you will find the frame etc in way of measuring between rotors.
Maybe a trammel bar would work. That is one alternative I made.
Scribe a a line on tire tread then measure with the bar.



Dennis smiling smiley

SpitfireBGT Avatar
SpitfireBGT Mike Soltez
Irwin, PA, USA   USA
I've been fighting a weird handling Spitfire since I lowered the front by an inch. I have Spax dampers with adjustable perches. I kept my stock springs. So when I lowered the car the lower wishbones gets closer to horizontal and effectively gets longer giving me more negative camber. I took shims out to get -1 degree camber and set the toe to 1/16" in at the wheel not tire using the string method. I broke the rule about changing more than 1 thing at a time by putting new 185/60 13 Federal SS-595 tires on my 6" wide alloys. The old tires were Yokohoma A008 in the same size.
The problem is that the car is very squirrely under braking. If I measured correctly I have about 4 degrees of castor with 6 shims in the rear and none in the front. Adding even more caster should help but I hate tweaking my trunions even more even if the wishbones will twist being an open channel. Adding more toe in will cause tire wear I would think.
Does anyone know the scrub radius of a stock suspension. I'm Thinking that my wider wheels have added too much positive scrub radius. It was annoying with the Yokies but intolerable now. When I did the frame off restoration I measured the frame based on the Bentley manual specs so it's not tweaked.

Any suggestions?



Aspiring Know It All

clshore Carter Shore
Beverly Hills, FL, USA   USA
Sounds to me like you may have rear alignment issues to resolve.

clshore Carter Shore
Beverly Hills, FL, USA   USA
For those who have an iPhone, there are free apps for accurately measuring angles and level.

I use iHandy Level, but there are others.

Or you can spend money on a fancy Camber angle Gage that works no better, but cannot make phone calls, your choice. winking smiley

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