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Front End Alignment.

Discussion in '"Stock" Alpine' started by Mike O'D, Jul 28, 2020.

  1. Mike O'D

    Mike O'D Gold Level Sponsor

    The manual calls for a toe in of 1/8" which goes on to say that is equivalent to 17' of angle between the wheels. 17' of angle is .2833 degrees. A tire would have to have a diameter over 25" to have 1/8" be equal to .2833 degrees and you would have to be measuring from the very outside edges. Stock tires are about 23" diameter. These numbers don't seem to match up. Thoughts?

    All steering angles and dimensions MUST be checked with the car on gap gauges according to the manual. Anyone ever take their car to a shop for alignment where they put it on gap gauges?

    Thanks.

    Mike
     
  2. Bill Blue

    Bill Blue Platinum Level Sponsor

    Thoughts? I don't think I have ever seen an Alpine manual that specifies the tread as the measuring point.
    Bill
     
  3. Mike O'D

    Mike O'D Gold Level Sponsor

    Bill,

    I am trying to figure out how they equate 1/8" of toe-in to 17' of angle. Angle is a fixed dimension, no matter how long something is. A 1/8" difference from the back of something to the front of something will make a huge difference in angle depending on how far apart the measurements are. Let's say you use the fat part of the tire for your measurement. The distance across the tire at the fat part is about 17". 1/8" across 17" is 25' of angle (.4213 degrees). 1/8" across 25" is around the 17' the manual is specifying.

    The Alpine manual doesn't say where to measure the 1/8" from - hence the question. And why doesn't it match the angle they call out.

    Mike
     
  4. Limey

    Limey Diamond Level Sponsor

    I Don't think it matters which bit? As long as the first reading was at dead ahead and the second measurement is of the exact same spot but by the specified angle difference. Could be wrong of course...
     
  5. Mike O'D

    Mike O'D Gold Level Sponsor

    Limey,

    If you could work with the angle that would be exactly right. If you are working with a dimension, eg. 1/8" from front to back, then it makes a big difference how far apart the measurements are. It also bothers my engineering brain that the angle and dimension doesn't work out for the normal size Alpine wheels.

    No comments on the gap gauges? Have any of you guys had your front ends aligned? How did the shop do it? Don't know, don't care - it seems fine? I would be more than shocked if a shop (in recent times) used gap gauges, or had any idea what they were, yet the manual says "MUST" use.

    Thanks for any input - inquiring minds want to know!

    Mike
     
  6. husky drvr

    husky drvr Gold Level Sponsor

    Mike,

    Two observations from checking WSM 124.

    1> WSM doesn't specify a different toe in spec for 13 inch Alpine wheels or 15 inch Rapier wheels.

    2> WSM has an illustration showing use of their specified tool checking toe in on the sidewall bulge of the tires.

    Finally> the WSM specs were given for BIAS-PLY tires - radials generally don't like to use as much toe in, if any. Probably the best suggestion is to use the least amount of toe in consistent with stable tracking when driving.
     
  7. Limey

    Limey Diamond Level Sponsor

    Hi Mike,

    I have always been very unhappy with my steering and I am pretty sure it is because I have not had it set up as the workshop book. I am going to make the spacers then take it to my local that does 4 wheel alignment. I'm sure they steered better when new than mine does now even though I replaced the same shims etc
    Oliver
     
  8. Barry

    Barry Platinum Level Sponsor



    Mike,

    I don't see any point in worrying about whether toe-in is specified as some tiny angle or as 1/8" or exactly where the 1/8" is measured. My definition of toe-in is the difference in lateral distance between the tire center-lines (or some other readily identifiable point) at the front / back of the front tires at stub-axle height. If you have a different definition, that's fine. What matters is that the front wheels / tires are pointed slightly inward at the front when the car is on a flat / level surface and is not moving. The front tire wear pattern will show if the toe-in is correct (or not).

    All the "gap gauges" do is set the front and rear ride heights to the factory specifications. I can't imagine any typical alignment shop having gap gauges for a 50 year old British sports car and, in any case, I think it makes a lot more sense to align the front suspension at typical operating ride height (normal driver weight, 1/2 typical passenger weight, 1/2 tank of fuel, etc.).

    I would set the toe-in at 1/8", the camber at negative 0.5 to 1.0 degrees and the castor at the maximum positive value that can be achieved on both sides without messing up the camber.

    JMO and it may not be worth anything.
     
  9. Bill Blue

    Bill Blue Platinum Level Sponsor

    Barry, why negative camber? I have long been of the opinion the exact numbers (within reason) are not nearly as important as those numbers being the same, side to side.
    Bill
     
  10. husky drvr

    husky drvr Gold Level Sponsor

    Oliver,

    I haven't followed what you accomplished while restoring your Sunbeam so this this thread might not actually be of any help.

    http://forum.sunbeamalpine.org/index.php?posts/192198/

    HTH,
     
  11. Barry

    Barry Platinum Level Sponsor


    Bill,

    I agree that equal is more important (within reason) than absolute values, but I think negative 0.5 to 1.0 front camber is a good target.

    The WSM's call for 1/4 to 3/4 degree of positive camber, but given the Series Alpines low roll resistance and lack of negative camber gain, I think a little negative camber is a good idea for a road car with modern tires.

    Again, JMO & YMMV.
     
    Last edited: Jul 30, 2020
  12. Tom H

    Tom H Platinum Level Sponsor

    Mike, 1/8 " of toe in on a 23 in diameter tire yields an angle of .311 degrees, or about 18.5'. I think that's close enough. I think Husky drvr's observation from WSM 124 explains it. Thanks for putting me through the exercise of sines, degrees, radians and minutes. It's been a while since I last used any of those terms!

    Tom
     
  13. Mike O'D

    Mike O'D Gold Level Sponsor

    Lots of great discussions - thanks to everyone. Some background: Car is completely re-built including every component of the front end. I took careful measurements of everything and put it back together accordingly. I have no idea how the car drove prior to me owning it, because I received it as a non-runner, rusty broken down basket case. Much to my amazement, from the very first drive is handles great and tracks straight as an arrow down the road. I have put about 1000 miles on the car since re-build. I recently noticed that the outside edge of the right front tire had more wear than the left side. So, before I ruin a tire, I thought I should look at getting an alignment - then I read the manual.... Oh, and keep in mind that in order to have the car sit on the gap gauges, the manual says you will need to load approximately 300 lbs of weight on to the front jack points.

    Tom - glad you enjoyed the math! I cheat these days. I do a quick sketch in Solidworks, and it gives me all the dimensions I need.

    Mike
     
  14. alpine_64

    alpine_64 Donation Time

    Mike if the outside edge is feathering you may have to much toe in. When you turn into a corner does it turn in sharply but feel a bit snapy behind?
     
  15. Mike O'D

    Mike O'D Gold Level Sponsor

    Michael - I haven't noticed anything odd with the steering, but I have only driven a couple of other Alpines and only for a very short drive. It could easily have too much toe in. It also could have too much camber. I'm going to see what I can do to get it checked out. Thanks.
     

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