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Tom Fremont

Rear Toe-in

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My driver has 0.30 degrees of toe in on the LR. The shop which found it doesn't shim anymore so it's up to me. It's supposed to be 0-1/16" toe in, and the shop showed a spec of 0.12 degree toe in.

Any clue what the addition / subtraction of a single shim is good for? Opinions on inboard vs. outboard bracket? Adding vs. subtracting?

Thanks in advance,

Tom

 

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Tom,  if the tyre isnt shouldering I'd leave it as is. The book spec would be for rubber bushes, while aftermarket PU will be nearer zero toe to be correct. Also if the tyre shop measured toe using the front wheels as reference best check the front track is not larger than the rear - I think on the 6 it is.  Peter

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When I was adjusting mine I have a note "1 shim equates to 2.5 mm alignment change at rim"

Jerry

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Thanks, gents. 

Check my math, please: I get ~ 1/8" per degree using the 15" diameter of the rim. ( I don't know which diameter the spec refers to, rim or tyre. There is a nearly 2X factor between them. ) Using Jerry's 0.1" ~ 2.5mm means  one shim would move it too much and give me toe-out, and Pete's counsel applies.

I should add I saw excessive wear on the inside tread of the fronts, which were both at 0.12 degree toe-in, right on the minimum spec at the shop. Bushings are rubber fore and aft. Rear tread wear looks OK both sides.

Tom  

Edited by Tom Fremont

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Tom, Inside wear suggests too much toe-out. So the fronts need more toe-in to correct, If one tyre only had  shouldered it usually points to a bush failure on that side. Peter

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Hello Tom

I think I am right in saying that in the USA toe in is measured at front and back of the tyres whereas here in the UK we measure toe in at the rims of the wheel itself. A DIY way of checking is to stretch two thin pieces of string each side of the car so they are parallel  to each other and at a height at the centre of the hubs. Adjust the position of the strings so they are equidistant from each rear hub and equidistant from each front hub (and still parallel to each other). You can then measure from the rims of the wheels (not the tyres) to check toe in or out. Stick to the original spec in inches. I have between 0 and 1/8 inch toe in at the front. Never really understood using the tyres as the reference points because depends on tyre make, type and inflation. The only thing to watch out for using rims is any in/out movement of the rims as you rotate the wheels caused by slightly out of true wheel rims. Take a few measurements in that case. 

I managed to buy some classic optical wheel alignment gauges from a garage that was closing down but they are not that easy to use. I calibrate them in the parallel position with two lengths of copper pipe that are cut exactly the same before using them. They have pins that have to touch the rims and you measure off the alignment using the mirror system. On eBay the Dunlop type are around £200 and there are modern Sealey ones at twice the price. My bargain was £20  for the Dunlop style optical wheel alignment gauges and £20 for the Sealey type GA44 drive on alignment gauges. The only thing I had to make for the drive on types were small wooden ramps for all 4 wheels so the car sat level.

I agree with Peter that inside wear means too much toe out. I always do my own toe in since one garage misheard 0 to 1/8 inch toe in and adjusted fronts to one inch toe in. That managed to wear out the fronts in no time and the handling was very strange as well.

Keith

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I did the rears by eye with a straightedge across the tyre and lined up with the sills. Never had to repeat it as the Silentbloc bushes dont distort. Fronts I did with a DIY trammel bar. Again the nylatron.stainless bushes dont distort so it was a one-off job.

Peter

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Hi Tom,

WSM info for a TR6 (check if this alos applies for the TR5/250):
The TR6 WSM, section 64.25.17 indicates a required toe-in of 0-1/32" (per wheel). It does not say if this is measured across the rim or the tyre, I assumed the rim. 

1/32" toe-in equals 0,11 degrees, which is close to what your shop indicated (0,12 degrees toe-in), again, measured at the rim. So your LR wheel currently has too much toe-in with 0,30 degrees.

If you are using mm, be carefull: the conversion to mm in the WSM is not correct. 1/32" equals  0,794 mm (not 0,313 mm).

 

I then checked the math (stand to be corrected): 

If I recall correct, the shims are 1/16" (1,59 mm) thick. If this is correct, one shim changes toe-in by 0,264 degrees.

So if you remove an 1/16" shim from the inner bracket (or add one at the outer bracket), your car's toe-in will reduce by 0,264 degrees, and your LR wheel will be 0,036 degrees "in" (0,30-0,264=0,036 degrees), which fits well within the WSM recommended toe-in.

Measured at the standard 15"wheel rim  which measures 405 mm diameter at the curled edge where the alignment equipment is normally connected), this equals a change in toe-in of 1,87 mm or 0,0735", if you want to measure by yourselve with a wire.

 

Summary:
Removing or adding 1 mm of shim will change the toe-in by 0,166 degrees which equals 1,17 mm when measasured at the wheel rim (405 mm diameter).


Excel sheet:
I added my excel sheet so you (and others) can do the math yourselves.

 

Waldi

 

rear wheel toe-in adjustment TR6.xlsx

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For those not familiar with Excel, I added a screen print:

 

image.thumb.png.75e31cdcf21cef1221de0c04e781891e.png

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On 12/21/2019 at 1:20 PM, keith1948 said:

Hello Tom

I think I am right in saying that in the USA toe in is measured at front and back of the tyres whereas here in the UK we measure toe in at the rims of the wheel itself. A DIY way of checking is to stretch two thin pieces of string each side of the car so they are parallel  to each other and at a height at the centre of the hubs. Adjust the position of the strings so they are equidistant from each rear hub and equidistant from each front hub (and still parallel to each other). You can then measure from the rims of the wheels (not the tyres) to check toe in or out. Stick to the original spec in inches. I have between 0 and 1/8 inch toe in at the front. Never really understood using the tyres as the reference points because depends on tyre make, type and inflation. The only thing to watch out for using rims is any in/out movement of the rims as you rotate the wheels caused by slightly out of true wheel rims. Take a few measurements in that case. 

I managed to buy some classic optical wheel alignment gauges from a garage that was closing down but they are not that easy to use. I calibrate them in the parallel position with two lengths of copper pipe that are cut exactly the same before using them. They have pins that have to touch the rims and you measure off the alignment using the mirror system. On eBay the Dunlop type are around £200 and there are modern Sealey ones at twice the price. My bargain was £20  for the Dunlop style optical wheel alignment gauges and £20 for the Sealey type GA44 drive on alignment gauges. The only thing I had to make for the drive on types were small wooden ramps for all 4 wheels so the car sat level.

I agree with Peter that inside wear means too much toe out. I always do my own toe in since one garage misheard 0 to 1/8 inch toe in and adjusted fronts to one inch toe in. That managed to wear out the fronts in no time and the handling was very strange as well.

Keith

Hi Keith, not sure where your 1/8 front toe in figure came from but in the 4A wsm which I expect is the same as tr5/250 it gives 1/16 toe in front wheels and rear wheels. This usually means a total of 1/16 measured between the wheel rims on the centre line which is half the 1/8 you mention. This agrees with Waldi's comment of 1/32 for each wheel on the rear. 

Chris 

 

1577032526711_IMG_8132.JPG

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6 hours ago, ChrisR-4A said:

Hi Keith, not sure where your 1/8 front toe in figure came from but in the 4A wsm which I expect is the same as tr5/250 it gives 1/16 toe in front wheels and rear wheels. This usually means a total of 1/16 measured between the wheel rims on the centre line which is half the 1/8 you mention. This agrees with Waldi's comment of 1/32 for each wheel on the rear. 

Chris 

 

1577032526711_IMG_8132.JPG

Hello Chris

Yes I think I quoted the toe in for TR2/3/4 which seems to be 0 to 1/8th toe in. The 4A is 1/16th as you rightly say. Should have checked the figures!

Keith

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When I set up the rear toe on my TR250 25 years ago, I ended up with slight wear on the drivers side rear tyre after several thousand miles. Can't remember whether it was the inside or outside all these years later, but with an empty car it still checked out as ok.

I decided to ballast the drivers seat to approx my weight, and re measure. There was a slight change in toe on the drivers side (I nearly always drive solo), so I removed a shim to correct it and never experienced the wear problem again.

Neil

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