[bianchi2]

this is getting a wee bit tiring..first my set up..front springs 750# rear springs 125# front shocks 'koni' rear 'spica'( but they have been tested, still in good shape) wheels/tyres.. 205/50/16 set at 30 rear and 32 front.i would tell you the tire make, but it is cold outside and rainy,( at least to n.cal. standards. and after a whole day on the dealership lot..i am cold and tired.. stock sway bars. it works great in the dry.. but once it rains, like it has been doing here in n.cal for the past 3 weeks..if i take off like it is dry( not flooring it, just an ave take off) she will spin her back wheels( fun at first, but now..)and she will loose grip in tight corners, the fronts won't bite in a tight corner . i drive her very carefully in the rain..no suddin movement on the steering wheel or throttle...i have modifided the head as in jim k. book 80% just not the valves..so she is up in power, mostly tq...i can lay ( old school terms here) rubber even with the wide tyres on in the dry for quite a distance..but she is a handfull to drive in the rain..i know some of you folks here run a set up close to mine. at least the tyre size..do you have the same problems? thanks for any help..

 

[azmaynard]

Sounds like old tires to me. As tires age they harden and exhibit the qualities you mention. Also newer tires have much improved rubber compounds that work better in the wet.
Maynard

 

[bianchi2]

new tyres,, about 9 months old...

 

[azmaynard]

Could it be the tires sat for a long time before you bought them? If not, please let us know the brand so others can share their experiences with them. It is highly unlikely that a bit of head work would turn a Spider into a tire shredding beast.
Maynard

 

[bianchi2]

hankook k-106 tyres..i also did some other work to the car

 

[Zunige]

I don't know what the approach was to upgrade this car, but perhaps by comparing against steps taken in another approach that yields good results, it may be possible to gain some insight and go from there.

A stock '84 Spider has a soft suspension (soft springs, SPICA shocks), sway bars in the front and rear, 14"x6" light alloy wheels (12 lbs. each), and touring type "H rated" tires. It yields a "soft" ride, and the nose dives when one breaks hard, but the handling in a straight line or through a corner, in dry conditions or in heavy rain, is "balanced".

Typically, the first handling upgrade is to replace the wheels and tires. (This yields the biggest "bang for the buck".) Going to a 16" wheel, with modern tires should yield a noticeable improvement. It's really hard to imagine that anyone can go wrong with this upgrade, unless different size tires where used. For example, if the rear tires were wider than the front tires, this yield an under steering car. This would be very noticeable to a driver and can be easily corrected before going to the next upgrade.

The next upgrade would be to stiffen the suspension. There are many proven sets sold by suppliers, and there are also combinations that racers use. One can't go wrong with the sets, as these are the result of several evolutions and the R&D to achieve the required balance has been tested with real cars. (The work done by W&D to develop their street and race springs is a good example.) One can also buy springs independently and fit them to the car, as some of the racers do. However, they typically go through several combinations before achieving the balance they are looking for, unless they are following someone else's proven combination for the specific car. (Lets' remember that there are not so insignificant weight differences between Spiders of different generations.) Bottom line, the springs must achieve a balance between the front and rear of the vehicle.

The next upgrade would be roll bars, which are helpful for cornering, but don't have an effect when going in a straight line. Again here, there are several combinations. Some call for a larger rear bar only, some call for no rear bar, some call for a larger front bar. Bottom line, the purpose is to maintain a balance, working with the springs. (In this case, the car has the stock roll bars, and of course, these have no effect on straight line driving...)

Last, small adjustments to the tire pressure do make a difference, but these are refinements. The stock set-up for the '84 calls for the front tires to have 2 lbs. less pressure than the rear tires. Doing the opposite does change the handling of the car, but it is hard to imagine that it can cause the rear wheels to spin. Whatever is wrong, is only accentuated when there is less friction, as in the case of rain. It is hard to imagine that a modern street tire that is 9 months old would have issues in the rain.

If it were me, I'd see if I could find a friend with a similar Spider and then I'd drive both cars. Then, I'd swap the wheels between the cars. If this doesn't change anything, then the problem is likely in the balance between the front and rear springs.

Best regards,

 

[bianchi2]

thanks Zunige..i will take my fronts down to 28 psi in the front sunday moring, will keep the rears at 30 psi.. they are 32 front and 30 rear now..as for spring rate.. what is the coomon ratio front to rear..some suppyers are i think 1200 front and 180 rear.. but i ahve seen other rates.. so a ratio front to rear would be nice..thanks agian

 

[Alfapaulic]

wet

I would also experiment with the rear tire pressure. 30# seems like alot.

 

[aikendrum105]

Hi Bianchi - just for ref, I run the duetto (on 14" steel 1750 wheels and Michelin Energy XM1 185/70 tires ) at 32PSI front, 28PSI rear (as the rear is so much lighter than the front)

If I run the rears up to 32, they definitely become more skittish in the wet.

 

[Jonathan]

When competing with other types of car we would typically lower tyre pressure within reason in the wet but not going so low as to allow the tread pattern to close up and be less effective at clearing standing water. On a 550kg Caterham, running 185 width tyres I'd drop from 20psi to 17 psi.

We would also soften the adjustable anti-roll bars (sway bars) to the softest setting. Stiffening things up is not the way to go in the wet.

Different tyre brands give major differences in wet/dry performance - a great tyre in the dry may well be useless in the wet.

Jonathan

 

[John Gallagher]

My guess is the tire compound...too hard.