Instability at speed
Discussion
Hello.
My Caterham '98 which has been upgraded with a R400 engine, failed its MOT a few weeks back. It required new tyres at the back, some Nankangs were put on the back replacing some yokohamas, the structure needed a bit of welding, and all driveshaft boots were replaced.
Since I got the car back it feels pretty unstable once I'm over about 50 mph. Basically, the cars seems to drift and it feels like I don't have proper control of the steering.
I'm going to ring the garage on Monday, which is a decent garage but not a Caterham specialist, but I was just wondering if there is anything worth checking or trying meantime?
Cheers
Andy
My Caterham '98 which has been upgraded with a R400 engine, failed its MOT a few weeks back. It required new tyres at the back, some Nankangs were put on the back replacing some yokohamas, the structure needed a bit of welding, and all driveshaft boots were replaced.
Since I got the car back it feels pretty unstable once I'm over about 50 mph. Basically, the cars seems to drift and it feels like I don't have proper control of the steering.
I'm going to ring the garage on Monday, which is a decent garage but not a Caterham specialist, but I was just wondering if there is anything worth checking or trying meantime?
Cheers
Andy
I've heard of this problem ,ad it turned out the wheel nuts were loose, so check those first!
However, it worries me that you said "the structure needed a bit of welding". If you mean they had to weld some chassis tubes due to corrosion, I can't see how they could do a proper job without removing at least some of the aluminium skin. If they didn't do that, it is possible other tubes are affected by corrosion and remain undiscovered, or they might have distorted the tubes they have welded. Modern cars have plenty of extra metal around suspension points, and a bit of welding doesn't do much harm, but if it was my car I'd take it to a specialist to get the chassis checked over fully before driving it hard
However, it worries me that you said "the structure needed a bit of welding". If you mean they had to weld some chassis tubes due to corrosion, I can't see how they could do a proper job without removing at least some of the aluminium skin. If they didn't do that, it is possible other tubes are affected by corrosion and remain undiscovered, or they might have distorted the tubes they have welded. Modern cars have plenty of extra metal around suspension points, and a bit of welding doesn't do much harm, but if it was my car I'd take it to a specialist to get the chassis checked over fully before driving it hard
Thanks for your thoughts.
Yes it was corrosion "within 30 cm of the body mountings offside rear".
I use the car everyday but could pop it to a garage with greater expertise in Caterhams which is about 45 mins or so away.
It sailed through the MOT last year which I organised with a chap who has lots of experience with Lotus and Caterhams so I was probably too confident and casual this year putting the car to a generalist.
Yes it was corrosion "within 30 cm of the body mountings offside rear".
I use the car everyday but could pop it to a garage with greater expertise in Caterhams which is about 45 mins or so away.
It sailed through the MOT last year which I organised with a chap who has lots of experience with Lotus and Caterhams so I was probably too confident and casual this year putting the car to a generalist.
framerateuk said:
Aside from the tyre choice and pressures, once you've got those sorted I'd suggest getting a geo setup. Made a world of difference to my car. Especially over bumpy roads.
Hi Framerteuk, My Car is in with Andy at Qmech getting new suspension fitted after He found one of My rear shocks had a large crack in it, He is going geo the car also, really looking forward to see if big difference?
Thanks again.
I checked the tyre pressures and all were sitting at 21 psi except the driver side front which was at 16. I've equalised them all to 18 psi. The new cheaper tyres at the back are definitely reversed but they don't seem to be directional as far as I can tell.
I can't just swap over the wheels as I'd hoped myself as the Yokos are directional and the wheels are weighted differently, in fact the weight seems to be missing from the passengers front wheel.
I think as advised I need some decent tyres on the back and then need to get the car along for a geo set up. I've sent an email to George Polly to ask for a recommended replacement for the Yokos A021Rs. Probably should have done that in the first place...
I checked the tyre pressures and all were sitting at 21 psi except the driver side front which was at 16. I've equalised them all to 18 psi. The new cheaper tyres at the back are definitely reversed but they don't seem to be directional as far as I can tell.
I can't just swap over the wheels as I'd hoped myself as the Yokos are directional and the wheels are weighted differently, in fact the weight seems to be missing from the passengers front wheel.
I think as advised I need some decent tyres on the back and then need to get the car along for a geo set up. I've sent an email to George Polly to ask for a recommended replacement for the Yokos A021Rs. Probably should have done that in the first place...
Nankangs 
Are they the modern equivalent of Michelin pileups?
Surprised a 1998 car would have enough corrosion in rear basket to require welding. Has it been rear-ended in the past?
Rear pressures are still too high. Should be 18 cold. On dodgy tyres such as these, I'd even see if they could work at 16.
They are designed to work with cars that are much heavier than a Caterham, so stiff sidewalls and operating temperatures that mean they'll never warm up will manifest themselves as a 'loose' rear end. As per the Pilots that people used to fit to Caterhams years ago.
Aren't 888s the recommended tyre now?
Are they the modern equivalent of Michelin pileups?
Surprised a 1998 car would have enough corrosion in rear basket to require welding. Has it been rear-ended in the past?
Rear pressures are still too high. Should be 18 cold. On dodgy tyres such as these, I'd even see if they could work at 16.
They are designed to work with cars that are much heavier than a Caterham, so stiff sidewalls and operating temperatures that mean they'll never warm up will manifest themselves as a 'loose' rear end. As per the Pilots that people used to fit to Caterhams years ago.
Aren't 888s the recommended tyre now?
Was it the dedion tube that was welded? Thats the most likely thing to fail and it should be replaced as its probably all sorts of shapes. What area are you as your man probably knows more about euroboxes than caterhams especially with that choice of tyre on a 400 hp/ton car
Edited by elan_fan on Sunday 17th April 18:42
Bit surprised a non-specialist garage thought it was okay to simply weld up a 7 chassis... I can't think off the top of my head of a location where you could do that "within 30cm" of something that didn't require considerable disassembly?
Yes and tyres/tyre pressures sound dangerously wrong- why would a garage fit and fill tyres without knowing the requirements? Think I would avoid them like the plague from now on!
Yes and tyres/tyre pressures sound dangerously wrong- why would a garage fit and fill tyres without knowing the requirements? Think I would avoid them like the plague from now on!
EVS777 said:
Hi Framerteuk,
My Car is in with Andy at Qmech getting new suspension fitted after He found one of My rear shocks had a large crack in it, He is going geo the car also, really looking forward to see if big difference?
Andy did a cracking job of mine. It was great for trackdays but just bounced all over the place on the road. It's now far more stable and it really gives me a lot more confidence when I'm not on new tarmac. My Car is in with Andy at Qmech getting new suspension fitted after He found one of My rear shocks had a large crack in it, He is going geo the car also, really looking forward to see if big difference?
You'll be surprised how much of a difference it makes. Given that last time in Llandow I had catastrophic understeer which turned into snap oversteer just because my tyre pressures were 3psi too high - a full geo setup will make a heck of a difference.
It'll feel a bit different at first though so it might take a bit of getting used to! Getting my first trackday of the year in at Abingdon next month so I'll see how different it is on track too.
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