Camber conundrum

[cliff.b]

13 minutes ago, NonMember said:

It's probably true and has very little to do with the rear suspension's peculiarities. Nearly all road cars are deliberately set up to understeer, because a non-expert driver is far more likely to react appropriately to understeer than oversteer.

Yes, that makes sense, I suppose.

[Pete Lewis]

many cars are set up incorrectly as they dont follow the static height requirement for many of the specification triumph list

thats the nutshell of 150 lbs on EACH seat to set the suspn to its running average height 

Pete

[cliff.b]

1 hour ago, Pete Lewis said:

many cars are set up incorrectly as they dont follow the static height requirement for many of the specification triumph list

thats the nutshell of 150 lbs on EACH seat to set the suspn to its running average height 

Pete

Yes, I've heard that previously but the figure given in the Haines manual (2 to 4deg positive) specifically says with no occupants.

Do you know if the camber spec is different to this if loaded like you have said?

[Pete Lewis]

wsm says   2deg Pos  static laden does not specifiy spitfire  in the wsm for herald > vitesse6 spit 4 to lll

vit/GT6 has some unladen specs  3,1/4 deg pos unladen   and   2 +-1/2 deg static laden 

so 1.5 to 2.5 deg laden seems the ball park 

Pete

 

 

[cliff.b]

25 minutes ago, Pete Lewis said:

wsm says   2deg Pos  static laden does not specifiy spitfire  in the wsm for herald > vitesse6 spit 4 to lll

vit/GT6 has some unladen specs  3,1/4 deg pos unladen   and   2 +-1/2 deg static laden 

so 1.5 to 2.5 deg laden seems the ball park 

Pete

 

 

Ok, many thanks.

I think the only way to decide if I should remove these spacers is to try it and then see how the car feels.

But having inspected all the front suspension components I think I will replace the bushes and some of the bolts before too long, so probably would make sense to try it then. 

[johny]

My MK1 Vitesse always felt as if the back end wanted to come dangerously out of line especially on roundabouts in the wet so I increased rear toe-in removing two tie bar spacers each side and installed a half inch lowering block (alright I know I shouldnt have done two things at once, ooops and Ive change the tyres as well) and it feels a lot better. I'll have to see how tyre wear goes and maybe put back a spacer each side....

[Nick Jones]

5 hours ago, Pete Lewis said:

for normal driving i feel those spacers need removing any work will need the Toe checking after any twiddling 

Why? Depends what the camber actually is!

Given that positive camber has never been the best news for cornering grip and that tyre technology has moved on a bit since the factory set those figures, I would suggest that for normal road use you want 0.25 - 0.5 degrees negative camber. Bit more negative if you like to throw it around.

For caster, go with the factory settings  (3-4 deg iirc) and toe at 1-3mm toe in measured at the tyre tread. Parallel setting sharpens the turn-in a little but wears the inside edges of the tyres a bit quicker and can make it a bit wriggly under heavy braking.

Don't be afraid to experiment a little. Tyre pressures make a big difference too and the original Triumph specs are odd….

Nick

[cliff.b]

34 minutes ago, johny said:

My MK1 Vitesse always felt as if the back end wanted to come dangerously out of line especially on roundabouts in the wet so I increased rear toe-in removing two tie bar spacers each side and installed a half inch lowering block (alright I know I shouldnt have done two things at once, ooops and Ive change the tyres as well) and it feels a lot better. I'll have to see how tyre wear goes and maybe put back a spacer each side....

My car felt a bit scary when I first got it on the road last year, but the feeling of instability at the back was cured by changing from slight toe out to slight toe in. The steering was massively improved by replacing the front tyres which were a lower profile than the rear ones, giving a nose down stance, (I think this may have reduced the effective caster angle). Finally, I found several loose suspension bolts and experimented with tyre pressures.

Now, apart from needing to concentrate on steering if a road has a poor surface, it mostly feels steady as a rock, runs and brakes straight "hands off" and corners very well.

Maybe I should leave well alone 🤔

[cliff.b]

1 hour ago, Nick Jones said:

Why? Depends what the camber actually is!

Given that positive camber has never been the best news for cornering grip and that tyre technology has moved on a bit since the factory set those figures, I would suggest that for normal road use you want 0.25 - 0.5 degrees negative camber. Bit more negative if you like to throw it around.

For caster, go with the factory settings  (3-4 deg iirc) and toe at 1-3mm toe in measured at the tyre tread. Parallel setting sharpens the turn-in a little but wears the inside edges of the tyres a bit quicker and can make it a bit wriggly under heavy braking.

Don't be afraid to experiment a little. Tyre pressures make a big difference too and the original Triumph specs are odd….

Nick

As a rough measurement using a spirit level and a rule, the top of the rims are leaning in approx 1/4 inch compared to the bottom of the 13" rims which, if my calculations are correct, gives somewhere in the region of 1.5deg negative camber.

[johny]

2 hours ago, cliff.b said:

My car felt a bit scary when I first got it on the road last year, but the feeling of instability at the back was cured by changing from slight toe out to slight toe in. The steering was massively improved by replacing the front tyres which were a lower profile than the rear ones, giving a nose down stance, (I think this may have reduced the effective caster angle). Finally, I found several loose suspension bolts and experimented with tyre pressures.

Now, apart from needing to concentrate on steering if a road has a poor surface, it mostly feels steady as a rock, runs and brakes straight "hands off" and corners very well.

Maybe I should leave well alone 🤔

How many spacers did you remove to get toe-in at the rear? And yes if tyre wear is acceptable and theres no other problems it sounds like you have a good set up...

[cliff.b]

38 minutes ago, johny said:

How many spacers did you remove to get toe-in at the rear? And yes if tyre wear is acceptable and theres no other problems it sounds like you have a good set up...

I measured the toe with 2 x2m lengths of straight wood & then swapped sides to eliminate anything that wasn't true. I can't remember the exact amount but the distance between the wood in front of the wheels was a few mm more than behind the wheels, so I assumed I had slight toe out.

Removed one shim and then the measurement was less on the front of the wheel, so I assumed I had slight toe in.

[John Harris]

I have adjustable front wishbones, so run about 1/2 degree of negative camber. This will be fine for road use and for a wish bone suspension will keep the tyre in better contact with the road as it comes under load when cornering. Even with longer shimming bolts I am not sure I would shim all the way to negative camber, you are transmitting a lot of force through the distance of the wishbone end, through the shims to the chassis. From memory that's a lot of shims. 

The Castor angle on a Spitfire should be about 4.5 degrees, but these vary quite a bit due to manufacturing tolerance and can be quite different on either side. I have not been able to alter it by shimming. 

Less castor angle will make the steering lighter and have less return to centre after cornering, and will feel less stable in a straight line. More castor angle will solve for this, and keep more negative camber when cornering, but means heavier steering - hence power steering on modern cars.

As said previously, when setting up a car such as my 1500 spitfire, I did it with weight - 120 kg - in the vehicle ( two people ), a full petrol tank. I also have adjustable trailing arms, so no shimming, and can be adjusted along with the wishbones whilst on an alignment system. ( plus lowering block to set the rear camber angle correctly )

I have an MGB V8 which I have also put negative camber into the front suspension - 1/2 degree achieved by offset bushes. On it I have increased the castor from 7 to 11 degrees by putting wedge shims into the front cross member to maintain more negative camber when cornering, but have added electric steering to compensate. The offset bushing method may work on a Spitfire too, but some calculations would be required first. If they would then better than shimming but not as good as adjustable wishbones.