Tyre wear issues

[SteveP]

Hope you can help explain what is going on with my 1990 Dedion xflow with regards to tyre wear.

 

I have noticed that the both of the front tyres are wearing unevenly, with the outside wearing slightly more than the inside (by about 0.5mm). Also each of the tread blocks have a slight ridge on the inside of the block. The offside tyre has worn less (about 1mm) than the nearside.

 

At the back, the offside has worn about 2mm more on the inside than the out and the nearside tyre is even across the tyre.

 

From what I can tell, and by eye only, the car has a negative camber and appears to toe out quite a lot

 

Does this simply point to bad tracking or something else?

 

The tyres are S-02s (I got them part worn) but the same thing has happened to my other set of front tyres (Michelins)

 

I've done a couple of sessions up Harewood Hill, but apart from that normal road use nothing too extreme.

 

I'm just about to replace the fronts with S-03s and I don't want the same thing to happen

 

Thanks

SteveP

[Dave H]

Sounds like your tracking is out. I have mine set up with 20 mins toe IN, which is what Caterham recommended many years ago (1986 Live Axle XFlow).

Did have period where I was wearing the same side of both fronts, but that was because I was using the car for work regularly, and the route included a couple of fast roundaboutsteeth.gif

 

Dave H

[Graham Sewell]

Sounds as if you do more high speed right hand bends than left handers. THe slight feathering, from what little I understand is because you are nearing the limit of adhesion and pulling the block out of true slightly. Similarly, as you go around the corner, the car will lean on the outside edge of the outside tyre causing more wear.

 

Cheers,

 

Graham

 

Low tech luddite - xflow and proud!

[SteveP]

Thanks for the advice so far, I have a couple of follow up questions prior to visiting an alignment centre this weekend:

 

1) Is the camber angle adjustable on all Caterhams? How many degrees negative is recommended?

 

2) Is the castor angle adjustable on the front? What should it be?

 

2) Is the toe / camber adjustable on the rear (Dedion) without having to change / machine the ears. Again what should it be?

 

I'm running S-03s on the front, S-02s on the back and am looking to remove some of the twitchiness in a straight line and make the car more neutral (although I do run a quick rack)

 

As you've probably guessed, I don't have an owner's manual or any idea of "best" setup, apart from front toe that I'll get set to parallel as a start.

 

Thanks

SteveP

 

 

[Dave H]

The Tow-in on the front is the only adjustment on the Classic. The DeDion should be adjustable in all direction on the front. Not sure about the rears.

As with so many things on the Seven, the settings are down to personal choice. I would give the factory a ring and ask what they use as a standard setup, and start from there.

 

Dave H

[Graham Perry]

Not so sure the Caster is adjustable on 1990 cars. Tried to move mine only to discover that the rear lower mounting is an exact fit so couldn't do the trick of moving the spacing washers about like you can on later cars.

 

Toe and Camber are adjustable on rear, by using thin washers /shims between the de-dion and the ear. However, its not recomended for high stress usage as in motorsport, as the ears have been known to crack. Having said that I have run mine with thin washers for 10 years now to true up the camber and it has been fine.

[Paul Turner]

Steve

 

I think 1990 was the year when Caterham changed the front suspension on the de-dion, you may or may not have the camber adjustable top wishbones and caster adjustable bottoms. A quick look should identify if the top wishbone is one piece with an adjustable track rod end on the end of it, the caster adjustable bottom wisbone has a 1/2" bolt fixing at the front and rear. The rear suspension is only adjustable by fitting different ears (the brave fit shims but personally I would not). I have the manual for a 92 x-flow chassis at home, if you have the 90 onwards type chassis I could e-mail you the recommended settings, let me know.

 

Paul

[SteveP]

Paul,

 

Having checked, it looks like I don't have adjustable top or bottom wishbones, so I guess that I'm just stuck with the way it is. That's OK, a couple of things less to worry about (and blame when I can't get the car around the corners in the optimum way smile.gif

 

I'm going to leave the rear well alone.

 

Thanks for all the replies

SteveP