Spring!

This years first drive! Still very chilly outside and the tyres never got temperature, but what a great feeling anyway! But why is that every spring you're about to wet your pants when you push the accelerator, but in the autumn all you can think of is how to make the car go faster?

I went by a scale: 600kg +/-10 kg with 1/4 tank of petrol and windscreen on.

I need a new battery! I couldn't start the car even if it was fully charged. No other problems found.

Front bump steer

There is plenty of information about bump steer to be found on the internet. Basically bump steer is when the toe alignment changes during bump, ie when the suspension compress.

Here is an article explaining how to correct bump steer on Caterhams. 

There are lots of different techniques to measure bump steer. I used a construction laser level which projects a line when you point it on a surface.

I jacked up the car, removed the wheels and disconnected the link to the dampers on the lower a-arm making it possible to raise (bump) the wheels by hand.

Then I put my laser level firmly on brake disc with one hand and pointed the laser to it to the wall in front of the car. When I raised the wheel with my other hand and watched how the line moved on the concrete floor. With zero bump steer the line should not move sideways. To  be more accurate you can reverse the level and look backwards. The movement (if any) should be the same backwards as forwards.

There are many other ways to measure bump steer. One is explained in the article above, another one of the more clever ways I've seen is by using a mirror to remove the camber-gain effect.

You adjust bump steer by adding or removing spacers under the steering rack. It turned out that I had quite a lot bump steer on the front right and I ended up by removing one big 4mm spacer. For me it was a bit of a pain to undo the steering rack clamps because the dampers is making it hard to access the hex bolts from above, but eventually I got it apart.

If you change the steering rack height, you have to reset the toe alignment! I aim for zero degrees front toe. Some say a bit of toe out won't hurt and will give the car better turn in.

Note to self: Never undo the rod-end-to-upright nut! It's a real pain to get back!

Cross-ply rear camber

Crossply tyres such as Avon ACB10 don't need as much negative camber as radial tyres, CR500, 888 etc.

On the CSR you adjust the rear camber by using spacers. But what happens if your bolts through the spacers are not long enough?

The wheels fall off!!! Well, almost. This is what happend to me at the "NGK"-turn at Knutstorp last spring. I'm glad I stayed on the track!


This is how the rear suspension looks like:

What happened was the threads on the two horizontal bolts ripped, which caused the two vertical bolts to rip as well.

So if you have a cross-ply set-up with a bit less negative camber, check that you have enough threads left on the horizontal bolts, and maybe replace them with something longer.

Brake fluid change

Replaced the brake fluid. Used the same fluid as last time - ATE Blue racing.
Because I accidentally got some air into the system I had to remove the rear callipers and shake them around to get all air out.

I use Pagid RS14 pads on the front, and RS4-2 on the rear by recommendations from Pagid technical support. It gives me a good balance, but next time I might try one step more aggressive on the rear.

The Pagid part numbers are 20349 for the front AP-racing 4 pot calliper and 1158 for the Audi (?) rear.

Thanks to Levin Racing for their patience.

Cracked clutch disc - engine out!

I always had troubles downshifting at high RPM. Always when trying to engage second gear when going into an hairpin I had to struggle until the revs dropped. My upshifts weren't that fast either, but within reason. After consulting lots of people I just couldn't diagnose what the problem was. Everything went smooth when standing still and at normal road driving.

One day I had enough and decided to take the engine out and investigate what the problem was.

Cracked clutch disc. At high RPMs the centrifugal force would make the loose part of the disc move outward and touch the clutch cover, making it not fully disengage.

So what I learned about taking the engine out was:

• Write down and take photos of all connectors and hoses, and where they should be.
• Take your time and have someone to help you!
• You need a crane.
• Be sure that you put the gearbox mount at the right way when the engine is going back in, or you have to take it out again (ask me how I know this).
• There is a way to get the engine out. The exhaust outlet is really in the way, but if you rotate the exhaust so the cat points upwards/forward there is enough room. Take your time to avoid any damage to the body panels. If your exhaust manifold is not welded together it will be much easier because it can be removed completely.
• You have to remove the steering rod.
• Engine oil and coolant will be all over the floor, be sure to drain as much as you can before disconnecting anything.
• You don't have to drain the engine oil if you take the gearbox out with the engine.
• The engine mounts are hard to put back. Small hands would help.

And what a change! The new clutch completely transformed the car. What a relief!

Differential support

There are reports on broken differential mounts on the CSRs, so I have mounted support brackets to avoid a future disaster.  Some say they're not necessary if you have steel spacers on the diff mount, but all race CSRs have support brackets mounted, it is even in the regulations, and if they're not necessary I wonder why it shouldn't be necessary on the road models which are used on the track with sticky tires.

Caterham sell support brackets for race CSRs. Unfortunately they don't fit the road version! The reason is that the race CSR has the differential mounted in the center but the road version has the diff a couple of centimeters to the right. MOG racing also have an adjustable diff support kit but take quite a lot of money for it. Others (Gunnars garage) weld mounts onto the frame and bolt the diff through there.

EDIT 2011-10-11: Caterham now have a road-version of the diff strut available!

The original - doesn't fit

I didn't want to modify the frame so I bought the race support brackets from Caterham and modified them. Since I don't have any tools nor the skills about welding I went to a local firm to and asked them to do the welding for me.

I took the Caterham support brackets and cut the ends off. I let the welder make a L-profile with some angle to the sides. They are bolted on the existing diff cover holes and the seatbelt mounts.

Fitment check, then back to the welder

Removed excessive metal with a grinder, and then some black paint.

In place!

New holes in the trunk-plate.

Thanks to Tyresö Svets.