Gt-6+ Front Bump Steer Fix, In Detail?

[triumphlux]

You managed to fit 6 mm spacer under the rack in a 6 cylinder car !?

And it looks you still have lots of space between sump and steering rack.

 

I need to recheck this on my Vitesse but as far as I remember there is no space left at all .....

 

Did the same mod on my Spitfre and it definitely helped reduce bump steer.

 

Interesting car btw

[Nick Jones]

Yeah...... on mine I had to put spacers under the engine mounts to stop the sump sitting on the rack.

 

Nick

[Mark]

I recently put spacers under the engine mounts on my vitesse to give a bit more clearance. I checked on my untouched GT6 and it already had them fitted so it must have left the factory the way.

 

Mark

[Richard/SIA]

I've obtained a set of pre-65 Pinto/Mustang front spindles which are similar to Cortina but reasonably available in the U.S..

The steering arms are just a tad longer than GT6 so may help with bump steer at the expense of slightly slower steering.

Swapping to a Spitfire rack should speed it back up.

Due to my V6 engine placement I cannot move the rack rearward.

Not sure if moving it up will help with the new spindles, have to run it all through Speed-Wiz for some answers.

[TIMSGT6 X 5]

Moving the rack backwards or forwards is futile, in fact dangerous - as you may have found out!

 

The criterion for minimising bump steer is to ensure that the relationships in HEIGHT of the inner and outer suspension arm  and steering track rod joints are the same.

 

See the diagram below.  A.B and C,D are the outer and inner, upper and lower suspension joints respectively.     X and Y are the track rod end and knuckle joints.

The ratio of the distances BX/AX should be the same as DY/CY.

 

BUMP-STEER DIAGRAM.jpg

 

JOhn

That is the best succinct explanation I have seen John, clears up what has eluded me for some time, thanks.

[Nick Jones]

I think that moving the rack back is meant to help the Ackerman situation (not good as standard) but has other less welcome consequences as well.

 

Nick

[DaveNotSoSideways]

I raised the rack about 4mm, and raised the trackrod ends (rose joints) a few mm too, according to the measurements that reduced any bumpsteer to a minimum. I made the spacers for the trackrod ends (rosejoints) bespoke for each side as each side needed a different setting.

[Richard/SIA]

Should bring this up to date a bit.

Engine and trans areas of the chassis are now fully welded.

Not pretty but stronger than original.

Mounts are fully welded in.

Dummy engine in place so that I may work on the suspension and steering.

 

Front suspension towers are modified and boxed over to make room for a modified steering rack and column, also a remote oil filter adapter which goes on the front of the engine like a Rover v8.

Got a set of early Ford Pinto front spindles and rotors to use with custom A arms I still need to make.

They are very similar to pre-strut Cortina with ball joints top and bottom.

Will be buying alloy calipers.

The Pinto spindles have slightly longer steering links which should help with the ackerman issue.

 

Crank and alternator pulleys are most likely to be custom made on my CNC's.

 

Seems a shop move is imminent as the expense of the current shop is crippling the parts budget.

Was fine when I had a partner in it but he ran afoul of the local paint shop who threatened him with a formal complaint so I've been on my own for a year.

I will certainly miss the extra space but I suppose this will make my build more relevant to all you guys working in tiny garden sheds.