Setting front suspension

[Dave Nichols]

Gentlemen,
The front end on my mid-1970's Caterham S3 looks a tad high to me. Just in front of the rear wheel, the chassis measures 6 inches off the ground. At the front of the car it is 8 inches off the ground. What is normal and how do I adjust the front end to drop it a tad?

--Dave

[Doug Liedblad]

Dave

That seems a bit high. What size wheels and tires do you have? My front is ~7.5" on 14" wheels 195/60R14. That's just behind the front lower A arm mounting point.

Generally the front should be lower than the rear. Could someone have mixed up the front to rear shocks??? I don't know if this is possible just a wild thought.

Do you have adjustable spring platforms? A couple of big jam nuts and a threaded part on the shock so you can change the spring preload.

A first approximation is also that the lower front A arm should be parallel to the ground.

The adjustable springs were an option so you might see them without.

Coil over.jpg

[GWise]

It also could be that your rear springs are sagging. If you don't have coilovers, you could purchase some spring spacers for the rear.

[Doug Liedblad]

Dave

Can you post some photos of the front shocks and springs?

I can't see much detail in your earlier pictures.

Thanks.

Doug

[Dave Nichols]

I sent an e-mail to Caterham USA and British Sports Cars in San Luis Obispo to see what they say. For some reason I can't seem to post am image here.

[sevenhead]

"Hopefully your suspension is not set up like this as in up on the tippy toes. Looks like it would if the engine is out but I see air cleaners in the picture.
Otherwise your springs are waaay too long."

I posted this comment elsewhere and attached one of your pictures. You appear to have Spax dampers (I can see the slotted adjuster)....
WAIT A MINUTE! The lower A-Arms are upside down! They are handed and the right one is on the left and the left one is on the right. The lower damper pickup should be below the axis of the trunnion pickup tab. Here is a page out of the Weale book (everyone should own a copy) and a picture of my car taken some time ago to give you a visual.
This is easily corrected. You won't need to mess with the upper link or upright. I would be very cautious removing the damper assembly because of the unusual forces that are being applied to it. Make sure to have a jack under the upright. It should handle a helluva lot better after sorting this out!
This assembly error does give me pause..... I would have a chat with the previous owner.
Let me know if you need anything else.
Good luck.
Lee

[GWise]

Nice call sevenhead. That would explain why the tie rods looks so awkward. I wonder how much bump steer you have!

[Dave Nichols]

You hit it right on the head Sevenhead (no pun intended). That is exactly what it looks like. Sounds like an easy fix but it does make we wonder what else I might find. It is especially funny if you think it has been this way for 34,000 miles! SHEESH!

--Dave

[Dave Nichols]

Well, the car is sitting right as it should, six inches off the deck front and back, nice and low and looks great! It is a much more nimble drive as well. I'll post pictures next week.

[GWise]

If you haven't already, make sure to align the front end. You will probably be, if anything, toe out.

[Doug Liedblad]

If possible the rear should be a bit higher than the front. With you in it.

[magnusfeuer]

13mm to be exact, as measured just in front of the rear wings and mid front suspension.

[Doug Liedblad]

I thought it was supposed to be 15.5mm??

[magnusfeuer]

You are right:

http://www.californiacaterhamclub.com/resources/AssemblyGuide.pdf

Section 3 page 5:

"Cars fitted with adjustable damper platforms should be set to have a ride height of a minimum 75 mm under the sump with driver and passenger aboard. The rear of the car should then be adjusted to be approximately 15 mm higher than the front. "

More rake gives more oversteer, although I'd look at the standard culprits before using rake to change that behavior.

/Magnus F.

[Doug Liedblad]

You mean I'm right? Or at least close. I just added the .5 mm to start an argument.