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TR4a- Front alignment settings


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Folks, I just wanted to confirm the front end alignment numbers for a TR4a, based on what’s in the shop manual, as some parts of the TR4a supplement say to reference the TR4 section.

Camber: 2 degrees positive (page 4-101) 

Toe-in: Here the manual is a bit confusing. On page 4-101 it says “1/8 inch (normal tires) or 1/16 inch (Michelin X or Goodyear DFS)”. However on page 4-211 it just says 1/16 inch toe-in. 

The manual also says to place 150 lbs of weight on the seats during alignment. Is this necessary, or was that a requirement due to tire construction at the time? 

BTW - if it makes a difference, I’m running 165/80 R15 radials.


Thanks 

Jim

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Hi Jim.

on the 4A I thought the camber was nearer to 1/2 degree Negative

 

The 150lb is correct.   without the weight the car will rise and encourage the wheels to go more positive camber.

If you set the camber to 0 degrees without the weight then it will go a little more negative when driving.

Roger

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I hate to disagree with John, but, in order to run in a straight line without the need for constant correction, toe-in is required.

Modern laser kit doesn't know about 1/16" toe-in, so 20 minutes of arc is what's required (that's 1/3rd of a degree).

Ian Cornish

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Ian, the 1/16 toe-in matches what the TR4a supplement says in the manual. Though John recommended zero toe-in, he did mention to err to toe-in. So maybe I’ll start with 1/16 toe-in and see how it tracks.

Thanks

Jim

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  • 1 month later...
On 23 May 2019 at 8:41 PM, Tr4aJim said:

Ian, the 1/16 toe-in matches what the TR4a supplement says in the manual. Though John recommended zero toe-in, he did mention to err to toe-in. So maybe I’ll start with 1/16 toe-in and see how it tracks.

Thanks

Jim

How did you get on with that setting Jim? I am about to get my 4A checked but when the suspension was polybushed a few years ago I seem to remember we put in a little adverse camber with the shims. I guess the alignment should stay the same (1/16 toe in)?

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Are the toe in figures per wheel or combined? The handbook doesn't state so I've always gone with just a little bit of toe in - The old fashioned kit I used to borrow used to have a dial on it for wheel size that converted the toe in/out to inches - the modern one just does degrees so I've tended to just go for a tiny bit of toe in which seems to work.

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Folks, sorry, I had intended to post the alignment results but it completely slipped my mind.

Here are the results the alignment shop gave me. The first is with a 150lb person in the driver seat and the passenger seat empty. The second is with a 160lb person in the passenger seat as well (the shop owner said when he hires a tech, the first question he asks them is how much they weigh :D).

Afterwards I was very pleased with how the car handled. The steering felt a bit “lighter” than previous, and there was little to no bump steer, even over our winter ravaged roads.

BTW - Regarding bump steer: Mick had sent me a procedure for checking bump steer, but it involves removing the springs. So I will attempt that once driving season is over. I also sent an email to Richard Brunning at Bad Obsession Motor Sports (Project Binky) regarding their procedure for checking bump steer (episode 11), but he said their procedure relied on the car being level.

Oh, I run 165/80/15 tires.

Cheers

Jim

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Edited by Tr4aJim
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Andy - the toe-in figure is for the pair of wheels, whether 1/16" or 20 minutes of arc (modern laser kit).

I cannot imagine any way in which it would be possible to measure other than between the two wheels.

I'm glad I have a crude old TR4 - setting up an IRS car appears to be a nightmare!

Ian Cornish

Edited by ianc
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On 23 May 2019 at 9:10 AM, ianc said:

I hate to disagree with John, but, in order to run in a straight line without the need for constant correction, toe-in is required.

Modern laser kit doesn't know about 1/16" toe-in, so 20 minutes of arc is what's required (that's 1/3rd of a degree).

Ian Cornish

What is the equivalent Ian of 1/16 in mm? My laser machine is reading the toe in mm & the camber/caster figures in decrees & minutes.

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Thanks Ian & Hamish.

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  • 3 years later...

Having just changed my outer track rod ends, I have checked the tracking using my new Gunson trackrite

 https://www.gunson.co.uk/product/G4008/Trakrite-Wheel-Alignment-Gauge

I get a reading of 0.5° toe in both sides. After much research on here, & else where, I now know that if TOE is specified in inches (or millimeters) then it refers to the total for both wheels. If however it is specified in degrees, then it is for one wheel.

So, for example, 1/16" toe in would translate to 0.125° (7.5 minutes) for a 15" diameter wheel.

sin 0.125° * 15"( diameter of wheel) * 2 (both wheels) * 16 (for 16ths on an inch) = 1.047  i.e near as dam it 1/16"

I see this is in disagreement with Ian's figures above, but that is how I see it.

 Therefore I need to adjust my tracking !

Bob

Edited by Lebro
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On 7/1/2019 at 8:06 PM, ianc said:

Andy - the toe-in figure is for the pair of wheels, whether 1/16" or 20 minutes of arc (modern laser kit).

I cannot imagine any way in which it would be possible to measure other than between the two wheels.

I'm glad I have a crude old TR4 - setting up an IRS car appears to be a nightmare!

Ian Cornish

I appreciate 1/16 of an inch is the total toe in but is the 20' of arc the relative angle between each wheel and parallel or the angle between the 2 wheels?

The old tracking kit I used to borrow had a simple dial/lever which you put in the wheel size and it gave the toe in figure the measured angle. The one I have now just gives the angle.

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