GT6 MK3 tyres and front spoiler

[Keith Nock]

Hi The tyres on my GT6 are  due for changing not because of  wear but on age I fitted Minilight wheels with Pirelli P3000's 175/70/13 14 years ago, I don't do a lot of miles per year but want a premium brand tyre wear rate is not overly important but want a tyre which will grip well ,what would you recommend . The car is fitted with GAZ shocks all round and uprated front springs as will as a leaf spring I bought from jig saw racing .Next at high motor way speeds my GT6 late MK 3 swing spring ( non roto flex ) has a slight instability which not a major problem would the spoiler as fitted to later spitfires improve this I had a late spitfire 1500 for 25 years and never experienced any instability   

Your thoughts would be appreciated

Regards Keith

  

[Clive]

For great grip, especially in the wet, either Falken or Uniroyal. Both are excellent from personal experience. Both a bit soft, so wear a tad faster but by the sounds of it that won't be an issue.

Instabilty, it may be woth getting a proper 4 wheel alignment done, checking camber/castor as well as front and rear toe. https://alignmycar.co.uk/

A spoiler may help, but if teh suspension is not set up correctly it can cause instabilty and/or odd handling. 

My spitfire does have a spoiler, but the suspension is carefully setup and is perfectly stable even at very licence losing speeds (on German autobahns of course)

 

[Pete Lewis]

the biggets contributor to stability at speed is the rear wheel Toe 

some DIY work will give you a good clue 

 

[chrishawley]

Very much to your credit to change the tyres on the basis of age. I very nearly came a cropper in that respect ; running around on 2008 tyres which 'looked fine' untill I removed them to paint the wheels. On removal it was evident how frail they were. And deformed as well.

So before getting deeply involved in steering geometry it might be worth just seeing how the vehicle feels when freshly shod.

As for spoilers: I don't know of any firm evidence about these. But when introduced (on mid-run Mk4 Spit) it was the opinion at the time that they were significantly beneficial handling-wise. If yours is a late, non-roto, GT6 then by rights it would have had the spoiler in any case. So liitle to lose by giving a spoiler a go.

I had a hard time sorting out the 'twitchiness' on my GT6 (roto) after rebuild. Long story and more than one factor was involved; incorrect anti-roll bar, worn steering UJ, loose steering column, excessive tyre pressures and severely incorrect (too little) caster on left front suspension.  Thus handling issues may not just be about adjusting things but assessing all components of the  steering/suspension for wear or deterioration.

If the vehicle doesn't feel right at speed then there is the potential influence of modified spring rate and shock stiffness. And whether stiffer is actually better or not for the particular requirements.

A Hands Off test can be informative. On a straight, even, clear road lift hands (just) off the steering wheel at a modest speed (e.g. 50 mph).   Vehicle should 'hold it's own line' without wandering or deviating for a good distance (e.g half a mile). If immediate correction is need then something needs attention.

 

 

 

[Keith Nock]

Thanks for the suggestions 

I will try changing the tyres first and see how it handles With regard to the spoiler My car is a later 1973 car non roto flex and it did not come from the factory with a spoiler as when i bought it it came with the grill infills for the 1/4 valances which cant be fitted with the spoile  . It was quiet original when bought  but in need of a total rebuild which I did over three years I don't know  when the factory started fitting the spoilers on GT6's or if they have all been retrofitted buy owners over the years but may buy one and try that later also as you say it wouldn't be a bad idea to check the tracking and wheel alignment all good ideas and worth looking at thanks

Regards keith 

[Stratton Jimmer]

DUNLOP T 175/70R13 are really good on my Sixfire. I don't yet have them on the GT6 but that is my plan as pairs come up for replacement. The GT6 currently has a Chinese brand which seems OK but nowhere near as good as the Dunlops.

 

[2.5Pi1969]

I'm with Clive, Uniroyal RainExperts 175/70 13, brilliant tyres.

See how it is with thesw and if still wandering, align her.

Good luck.

[dougbgt6]

On 18/04/2022 at 20:26, chrishawley said:

If yours is a late, non-roto, GT6 then by rights it would have had the spoiler in any case. So liitle to lose by giving a spoiler a go.

Keith,

Mine has never had a spoiler, was it an extra?  I've always thought of them as bling, but as Chris says try it if you want.  

Doug

[Pete Lewis]

do asimple alingment check before you fit new tyres  so you dont scrub the new ones as soon as you have them fitted 

new tyres and spoilers wont correct basic geometry errors 

Pete

[Brooky]

Has it always been unstable at high speed, ie 14 years ago was it ok with new tyres? Is it only since the tyres have got older? If you change tyres first, check it for high speed again then go from there Id say, if its still same you know theres something else amiss. How are your bushes all round, is the steering rack tight etc etc good luck

[Keith Nock]

Hi Folks its been awhile but finally got around to doing the jobs . Fitted unroyal rain expert tyres as recommended ,also this winter rebuilt the entire front suspension new trunnions and vertical links had them on the shelf in spares draw so why not, put in new wheel bearings ,fitted better refurbished wishbones with new poly bushes, found the drop links to the anti roll bar were badly perished so fitted the uprated ones from Rimmer also fitted greasable trackrod ends( yes i did pre grease them thanks for the tip) and checked the tracking on the front and also fitted the  front spoiler. Took it for a short run and the front feels much better more planted and spot on will get a 4 wheel alignment done by the professionals next as i think the rear wheel alignment is slightly out.

keith

[ahebron]

When I was a lot younger and a bit lighter

On a metal road crossing a bridge with a bit too much speed I found the exit side to be a bit lower than the entry side.
This should not have been as big a surprise as I had minutes before driven over the bridge in the opposite direction.
The Spitfire MkIV with spoiler was not in contact with the road for little bit before the spoiler came down first into the gravel.
The spoiler scooped up stones from the surface and fired them under the bonnet denting it from the inside, a stone was also flung into the steering mechanism briefly locking it.
When the back end came down it snapped a couple of leaves in the spring.
For a while I had a Spitfire that could out corner many cars at speed including a half burnt Jensen Interceptor that I passed at 90 degrees to the direction of travel as the overtaking lane had a lot of loose metal on it.

All that because of a spoiler.
 

[Keith Nock]

I Had a spitfire 1500 for 25 years before the GT6 and never had a problem caused with having the spoiler

Regards Keith