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Spitfire on bad road surfaces


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14 minutes ago, cliff.b said:

I also raised the straight edge higher and measured gap to front sill edge (see pic). This was approx 5mm on NS and 10mm on OS, which is the side with more shimming. So I guess that would make sense. I'm thinking I should be reducing the shims on the offside?

IMG_20210421_140558_044.jpg

2nd pic showing gap to sill

IMG_20210421_140609_544.jpg

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3 hours ago, clive said:

Try taking a shim from each side. But check the front wheels too. 

Is there a defined figure for how much 1 shim will affect the toe and if not, any educated guesses?

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so you have some rear wheel toe out and a tad of centre 

use clives figures toe out at the rear makes it have very mind of its own 

did you have some load on the seats  ...it makes a good few mm difference in readings 

its looking like the thick shim side  wants reducing 

the trick is keeping the wheel centre line parallel to the car and getting the toe in/zero right at the same time 

but a little home work shows you can get a good result without spending a  fortune to make it wrong 

 

Pete

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21 hours ago, Pete Lewis said:

so you have some rear wheel toe out and a tad of centre 

use clives figures toe out at the rear makes it have very mind of its own 

did you have some load on the seats  ...it makes a good few mm difference in readings 

its looking like the thick shim side  wants reducing 

the trick is keeping the wheel centre line parallel to the car and getting the toe in/zero right at the same time 

but a little home work shows you can get a good result without spending a  fortune to make it wrong 

 

Pete

Well today I have removed one shim from the offside and also tightened all the bolts to the correct torque on both sides. Some of these were not very tight at all so I will be going around the entire car.

I now want to test it but unfortunately can't do so because I decided to change the brake shoes at the same time and have found so many issues. Most of these dealt with but a stripped thread on an adjuster (not seized and looks quite recent) has led to s new one being ordered. So testing will have to wait.

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one mistake often seen is the trailing shoe fitted upside down

the  rectangular hole for the  handbrake lever is top(has to be ) on the leading shoe but must be opposite, at the bottom on the rearward trailing shoe 

while youre in there have a quick look this does mess up with rear brake efficiency.

and on adjusters  as a basic start point you should disconnect the handbrake cable  (Just one side) then really  lock up hard both sides adjusters 

now reconnect the handbrake to just take the pin , this makes sure the cable is not holding the shoes away from the cylinder piston

once all reconnected  de adjust the drums to just be free then its set up for life 

Pete

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24 minutes ago, Pete Lewis said:

one mistake often seen is the trailing shoe fitted upside down

the  rectangular hole for the  handbrake lever is top(has to be ) on the leading shoe but must be opposite, at the bottom on the rearward trailing shoe 

while youre in there have a quick look this does mess up with rear brake efficiency.

and on adjusters  as a basic start point you should disconnect the handbrake cable  (Just one side) then really  lock up hard both sides adjusters 

now reconnect the handbrake to just take the pin , this makes sure the cable is not holding the shoes away from the cylinder piston

once all reconnected  de adjust the drums to just be free then its set up for life 

Pete

Yes, the shoes on both hubs were fitted incorrectly, like you explained. However, I don't think it would really have made much difference as neither brake cylinder was sliding so the incorrectly fitted shoe was probably not being used. The back plate had been painted both sides & the cylinders were jammed solid.

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18 minutes ago, Pete Lewis said:

dont you just love previous owners 

Pete

It's strange. This car has had what appears to me to be a good standard of restoration in many areas but a lack of attention to detail in others. But fortunately those are the sort of things that I can fix.

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To take a step back; there are 8 points of adjustment on a Spitfire suspension; Namely: left and right rear radius arms, shims (2), front and rear of lower front wishbones, shims (4), track rod ends, threads (2). That's leaving aside the steering rack itself.

If the car has been reassembled by persons unknown then it's quite possible that nothing has been set correctly, a lot of unknowns. And another unknown on POs restoration is how well the chassis was checked for true or whether it was just thought to 'look ok'. That a PO would fit the brake shoes incorrectly does less than inspire confidence in anything else!

Hopefully adjusting the rear toe in will produce a good result. But if not then it may be necessary to look at the suspension and steering geometry in its entirety - possibly involving laser alignment (££s). On the rear the camber may need to be considered; This is not separately adjustable but deviation may indicate bush wear or spring weakness/failure. On the front is there any evidence that the camber and castor have been correctly attended to? The inner ends of the lower wishbones would be shimmed according to requirement. The Spit 1500 ops manual implies that castor is not adjustable separately but the GT6 manual says it is (which it is!).

A Spitfire should handle perfectly well and be perfectly stable under all usual driving situations. Steering should (by comparison to moderns) feel heavy at low speed and still quite firm even at speed.

I'm none to sure about the unequal mix of tyres. While probably not the root of the problem they don't help in sorting it out. With a set of Toyo 155/80s available for under £120 it might be worth replacing the tyres simply to eliminate this aspect from the equation.

I think I'd also add a thought about the centre-line of a vehicle: From the suspension's point of view the center line can be defined as the line perpendicular to the midpoint of the distance between the driving wheels. This may or may not correspond to the center line of the bodywork. Thus on a heavily restored vehicle body features such as sills/wheel arches may or may not provide very precise datum points for measurement. Or to put it another way; toe-in is more precisely defined by the relation of one wheel to the other rather than the relationship of each wheel to the bodywork.

I hope you get an easy resolution without recourse to more detailed investigation.

C

P.S. I'll have four 155s going spare soon. Rather old but still usable. £0. Near Hitchin

 

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3 hours ago, chrishawley said:

To take a step back; there are 8 points of adjustment on a Spitfire suspension; Namely: left and right rear radius arms, shims (2), front and rear of lower front wishbones, shims (4), track rod ends, threads (2). That's leaving aside the steering rack itself.

If the car has been reassembled by persons unknown then it's quite possible that nothing has been set correctly, a lot of unknowns. And another unknown on POs restoration is how well the chassis was checked for true or whether it was just thought to 'look ok'. That a PO would fit the brake shoes incorrectly does less than inspire confidence in anything else!

Hopefully adjusting the rear toe in will produce a good result. But if not then it may be necessary to look at the suspension and steering geometry in its entirety - possibly involving laser alignment (££s). On the rear the camber may need to be considered; This is not separately adjustable but deviation may indicate bush wear or spring weakness/failure. On the front is there any evidence that the camber and castor have been correctly attended to? The inner ends of the lower wishbones would be shimmed according to requirement. The Spit 1500 ops manual implies that castor is not adjustable separately but the GT6 manual says it is (which it is!).

A Spitfire should handle perfectly well and be perfectly stable under all usual driving situations. Steering should (by comparison to moderns) feel heavy at low speed and still quite firm even at speed.

I'm none to sure about the unequal mix of tyres. While probably not the root of the problem they don't help in sorting it out. With a set of Toyo 155/80s available for under £120 it might be worth replacing the tyres simply to eliminate this aspect from the equation.

I think I'd also add a thought about the centre-line of a vehicle: From the suspension's point of view the center line can be defined as the line perpendicular to the midpoint of the distance between the driving wheels. This may or may not correspond to the center line of the bodywork. Thus on a heavily restored vehicle body features such as sills/wheel arches may or may not provide very precise datum points for measurement. Or to put it another way; toe-in is more precisely defined by the relation of one wheel to the other rather than the relationship of each wheel to the bodywork.

I hope you get an easy resolution without recourse to more detailed investigation.

C

P.S. I'll have four 155s going spare soon. Rather old but still usable. £0. Near Hitchin

 

Many thanks for your thoughts Chris. As you say, there is s lot to consider. I have got the back wheels on the ground again now, after attending to the brakes and removing one shim from the offside. I also took the opportunity to check everything with my torque wrench and almost everything was under tightened, including the nuts that locate the radius arms & shims.

After a short drive to check brakes I tested the alignment as before and the OS measurement to the body had reduced by 5mm. However, on checking the NS, there now is no gap and the only changes I have made is tightening things. (Could that have compressed the shims enough to make this much difference). 

Anyway, I had considered that the body might not be centred so measured again using string under tension & comparing distance to wheel rims front & rear. On the OS, where the shim was removed, the front rims are approx 8.5mm inboard compared to the rear. As the track on the 1500 is 25mm less at the front I'm thinking that's 12.5mm a side so the OS rear wheel now has slight toe in (4mm over 2.1m wheelbase)

I repeated the same process with the nearside & the difference is only approx 2mm, suggesting greater toe in on that side.

I would appreciate a "sanity check" on the above to confirm if my thinking is sound or not.

 

 

 

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Just to update, I have made a few measurements and I believe the body is slightly out of line with the chassis do clearly using the bodywork as a reference point isn't going to work. I will start again from scratch and attempt to get some more meaningful measurements.

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1 hour ago, Pete Lewis said:

can you cut a timber of a known length to locate off the main chassis rail ?? to get datum beyond the sill line to gauge against 

pete

Good idea Pete. I have been able to confirm that removing one O/S shim means that I have slight negative toe in now instead of positive, which if I have understood correctly is what I should be aiming for?

I now want to try and check alignment of both wheels with the chassis.

Hopefully I will get to play with it again sometime tomorrow. 

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I had a look at various books to get some more insight into this. Some points I picked up are:

 

‚ÄĘ Although alignment is best done in the laden condition Triumph did specify measurements for the kerb condition, namely: rear 1/32 to 3/32 in. toe in. Front 1/16 to 1/8th toe in.

 

‚ÄĘ The tolerance between ‚Äėright‚Äô and ‚Äėwrong‚Äô is 1/16th in. - pretty fine measurements

 

‚ÄĘ Haynes (for both gt6 and spit) says ‚Äėdon‚Äôt do this at home, specialist equipment required‚Äô.

 

‚ÄĘ Rear wheel alignment uses the front wheels as the datum.

 

So where to go from here? I would suggest that a way forward is to set the front toe in. The procedure is:

 

Set front wheel is straight ahead position. A U-shaped jig will now be required to pass under the car a measure the distance between the rear lip of the wheel (not the tyre). Measure this distance. Rotate wheel by 180 degrees. Then measure distance between the (now) leading edges of the wheels. This difference between the measurements is the toe in (or out). Adjust the track rods to bring the toe in to 1/16 to 1/8th. Track rods should be equalised for length (same number of free threads).

 

This should now give a datum condition for the front wheels.

 

Using a long straight edge and spacers it should now be possible to transpose this angle (off the straight ahead) to the rear wheels. If the rear wheels can be made to be in line with each corresponding front wheel then that gets to close to the correct adjustment. From there the rear wheel needs to have just a tad more toe out (maybe 1/32 each wheel)

 

The overall picture here is to get the front wheels right then adjust the rear wheels to them .

 

I hope the above makes sense but I can imagine others more experienced than myself may have better or quicker suggestions.

 

It’s a bit of guess why the measurements changed so much just with torquing things up. But one possibility is that if the bracket areas have been heavily painted then squeezing this up can make quite a difference. I get his impression that getting the final good result is going to involve careful assessment of the entire steering and suspension system.

 

Any help?

 

Cheers

C

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10 minutes ago, chrishawley said:

I had a look at various books to get some more insight into this. Some points I picked up are:

 

‚ÄĘ Although alignment is best done in the laden condition Triumph did specify measurements for the kerb condition, namely: rear 1/32 to 3/32 in. toe in. Front 1/16 to 1/8th toe in.

 

‚ÄĘ The tolerance between ‚Äėright‚Äô and ‚Äėwrong‚Äô is 1/16th in. - pretty fine measurements

 

‚ÄĘ Haynes (for both gt6 and spit) says ‚Äėdon‚Äôt do this at home, specialist equipment required‚Äô.

 

‚ÄĘ Rear wheel alignment uses the front wheels as the datum.

 

So where to go from here? I would suggest that a way forward is to set the front toe in. The procedure is:

 

Set front wheel is straight ahead position. A U-shaped jig will now be required to pass under the car a measure the distance between the rear lip of the wheel (not the tyre). Measure this distance. Rotate wheel by 180 degrees. Then measure distance between the (now) leading edges of the wheels. This difference between the measurements is the toe in (or out). Adjust the track rods to bring the toe in to 1/16 to 1/8th. Track rods should be equalised for length (same number of free threads).

 

This should now give a datum condition for the front wheels.

 

Using a long straight edge and spacers it should now be possible to transpose this angle (off the straight ahead) to the rear wheels. If the rear wheels can be made to be in line with each corresponding front wheel then that gets to close to the correct adjustment. From there the rear wheel needs to have just a tad more toe out (maybe 1/32 each wheel)

 

The overall picture here is to get the front wheels right then adjust the rear wheels to them .

 

I hope the above makes sense but I can imagine others more experienced than myself may have better or quicker suggestions.

 

It’s a bit of guess why the measurements changed so much just with torquing things up. But one possibility is that if the bracket areas have been heavily painted then squeezing this up can make quite a difference. I get his impression that getting the final good result is going to involve careful assessment of the entire steering and suspension system.

 

Any help?

 

Cheers

C

Absolutely helpful. My only previous experience with car suspension has been replacing parts that needed it, so a bit of a learning curve. But already now know significantly more than I did last week.

And regarding the tolerance for the rear toe, as it is set by shimming, rather than being infinitely adjustable, I guess you can only get it as near as the optimum number of shims will allow. Before removing the O/S shim, I held straight edges tightly against each rear wheel with bungees between both sides just ahead and behind the wheels. I then measured the distance between either end of the 6ft straight edges and the measurement towards the front of the car was 4mm greater. So slight toe out? After removing the single O/S shim the measurement is now 4mm less at the front than the rear, or a total difference of 8mm. I presume removing or adding more shims would make a similar difference.

What I don't know is how this amount of change measured over 6ft would equate to actual toe measured as intended at the wheel?  

 

 

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one advantage of parallel   zero toe  then there is no trigonometry involved  

a trakrite  form places like amazon is worth its weight in gold  shows the side slip you are making / resolving  single handed in less than 5 mins for around £50

dont get too paranoid  this is siple stuff not rocket science

if you want to centre the fronts just tape measure wheel to chassis 

then worry if the chassis is straight 

you just need some understanding of simple 1/6" accuracy 

its side slip that affects handling and rips off rubber when its excessive 

all the other faffing around on a 50 year old machine is paranoia thats not going to solve the basic problem 

bump steer and weave is down to basic errors dont get  misguided ideas as  the car has no idea what road camber it has to deal with 

or you end up resurfacing all the roads as well 

get the basics correct and drive with a smile , youre not in a F1 200mph car   

Pete

Pete

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I thought that I would have a go a this rear tracking stuff..

(CliffB, sorry to breach your copyright - the cheques in the post)

IMG_20210421_134253_772.jpg

It appeared to be really simple and straight forward.....

521392461_RearTracking01.thumb.jpg.92cc964f23c1a1e67889f6db110d3f31.jpg

But it has all gone wrong somewhere......

...maybe I need bigger bricks (apologies to Calendar Girls).....

....or to stop getting my timber from Bodgit & Quick

 

 

***STOOOPID BOY***

You got to have a laugh these days!!!

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24 minutes ago, Badwolf said:

I thought that I would have a go a this rear tracking stuff..

(CliffB, sorry to breach your copyright - the cheques in the post)

IMG_20210421_134253_772.jpg

It appeared to be really simple and straight forward.....

521392461_RearTracking01.thumb.jpg.92cc964f23c1a1e67889f6db110d3f31.jpg

But it has all gone wrong somewhere......

...maybe I need bigger bricks (apologies to Calendar Girls).....

....or to stop getting my timber from Bodgit & Quick

 

 

***STOOOPID BOY***

You got to have a laugh these days!!!

Lol

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Ok, after a bit more checking I have been out for a test drive this afternoon and everything feels so much better ūüĎć. The car drives & pulls up¬† straight "hands off", so I presume everything must be reasonably aligned. I drove again where I had the problem originally and while I could definitely feel that the surface wasn't good, there was none of that lack of control that I felt before.

Has removing the shim made the difference or tightening all the things that should be tight but weren't tight enough? I really don't know but I'm going to drive it now and see what other issues crop up ūüôĄ.¬†

Many thanks for all assistance given.

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Glad you've got a workable result and that it's proved relatively simple. That seems to tally with the theoretical considerations --- doing a bit of maths on your measurements the effect of removing the shim is (approx.) to shift the rear track from 1/32th (ish) toe out to 1/32th (ish) toe in for the kerb condition. So that's in range by the specs.

Cheers

C

 

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1 hour ago, chrishawley said:

Glad you've got a workable result and that it's proved relatively simple. That seems to tally with the theoretical considerations --- doing a bit of maths on your measurements the effect of removing the shim is (approx.) to shift the rear track from 1/32th (ish) toe out to 1/32th (ish) toe in for the kerb condition. So that's in range by the specs.

Cheers

C

 

That's interesting as based on your calculations the total change in toe is 1/16th of an inch and I think you said that is the tolerance for adjustment. So I guess it could make sense that one shim would move things by the same amount.

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