Caterham Tyre Choice
Discussion
Hi All,
I'm sure this must have been discussed before but I couldn't find it so apologies if this is repetitious.
I am a fairly new owner of a Caterham Roadsport but with quite a lot of Supersport spec and the VVC engine. Love the car on the road but struggling a bit on track with balance. Specifically I find the car quite "understeer-y" and hard to turn in unless I trail brake heavily. I am wondering if the standard Avon CR500 tyres may be the issue. I have seen good comments on the ZZRs but I'm not really keen to have a tyre that is so compromised in the wet.
So, is this a general issue or something that sounds specific to my car and if it's general, has anyone found tyre choice can make a big difference and if so, what tyres should I be considering?
Any help greatly apprecaited,
Cheers.
Andy
I'm sure this must have been discussed before but I couldn't find it so apologies if this is repetitious.
I am a fairly new owner of a Caterham Roadsport but with quite a lot of Supersport spec and the VVC engine. Love the car on the road but struggling a bit on track with balance. Specifically I find the car quite "understeer-y" and hard to turn in unless I trail brake heavily. I am wondering if the standard Avon CR500 tyres may be the issue. I have seen good comments on the ZZRs but I'm not really keen to have a tyre that is so compromised in the wet.
So, is this a general issue or something that sounds specific to my car and if it's general, has anyone found tyre choice can make a big difference and if so, what tyres should I be considering?
Any help greatly apprecaited,
Cheers.
Andy
I'd stick with the CR500's and get the car's geometry set up properly for you. The CR500's are designed for the Caterham and work really well as a good all rounder for the road and also in the wet for the track. Do you have an LSD on the car? If the car is really understeery (is that a word 
) its possible the LSD is not set up correctly. My money is on the car's geometry and tyre pressures though (start at 18 psi cold all round)
) its possible the LSD is not set up correctly. My money is on the car's geometry and tyre pressures though (start at 18 psi cold all round)Hello Andy, welcome.
As above, setup.
CR500's are a great all round tyre, and where specificaly designed for the Seven.
The ARB settings can have a significant effect on the oversteer/understeer caracteristics of your car.
You need to look at what colour bushes you have on your front ARB mounts. This will denote what size it is.
Sounds like you could use a softer front ARB, or, you could try stiffening up the rear. There are three settings for the rear. Have a look and see which hole the droplinks are in.
Personaly I would check the ride height first, and make sure you have set up with 10-15mm of rake between front and rear.
Set the front wishbones horizontal, and measure from below the chssis rail at the rear wishbone mount.
Then measure from below the chassis rail at the rear just in front of the rear wheel arch. You should have 10-15mm more here.
You could take it and get it set up y a professional outfit, which would give you a good starting point to experiment from.
Whatever you do, write it down in a little book, and note the effects.
Hope this helps.
Good luck with your new toy!
As above, setup.
CR500's are a great all round tyre, and where specificaly designed for the Seven.
The ARB settings can have a significant effect on the oversteer/understeer caracteristics of your car.
You need to look at what colour bushes you have on your front ARB mounts. This will denote what size it is.
Sounds like you could use a softer front ARB, or, you could try stiffening up the rear. There are three settings for the rear. Have a look and see which hole the droplinks are in.
Personaly I would check the ride height first, and make sure you have set up with 10-15mm of rake between front and rear.
Set the front wishbones horizontal, and measure from below the chssis rail at the rear wishbone mount.
Then measure from below the chassis rail at the rear just in front of the rear wheel arch. You should have 10-15mm more here.
You could take it and get it set up y a professional outfit, which would give you a good starting point to experiment from.
Whatever you do, write it down in a little book, and note the effects.
Hope this helps.
Good luck with your new toy!
Dear All,
Thanks for the very useful feedback. I will follow up on the geometry issues and post the outcome.
Tango7: I was interested by your point on an LSD. The car doesn't currently have one and I have been considering this too and for the sake of traction on exit was thinking of having one fitted. However, I had thought that poor turn-in was unlikely to be caused by the lack of an LSD as I had thought that the LSD would only have an effect when under power rather than on a trailing throttle. Do you think that is right or am I missing something on this point?
Thanks again,
Andy
Thanks for the very useful feedback. I will follow up on the geometry issues and post the outcome.
Tango7: I was interested by your point on an LSD. The car doesn't currently have one and I have been considering this too and for the sake of traction on exit was thinking of having one fitted. However, I had thought that poor turn-in was unlikely to be caused by the lack of an LSD as I had thought that the LSD would only have an effect when under power rather than on a trailing throttle. Do you think that is right or am I missing something on this point?
Thanks again,
Andy
Andy,
Poor turn in initially? Raise the back of the car 5mm, or drop front (dependant on the current ride height setting).
Next, toe out slightly.
If you find that it pushes on through / out of corners, play with the roll bars. I tend to end up with front full stiff, and rear 1 from stuiffest, with a reasonable amout of rake on the car - I'd offer settings, but have ended up with a different setup for each Caterham I've tracked (mostly because the measuring point I used changed as the chassis changed 2001 - 2005 - 2009.
Getting the set up right is great fun though, esp since most of it can be done in just a few minutes.
All of the aboe is, of course presuming your tyre pressures are set right - if the balance changes significantly from start - end of a session, they might not be.
Good luck with the learning curve, it's steep at first but loads of fun.
Gump
Poor turn in initially? Raise the back of the car 5mm, or drop front (dependant on the current ride height setting).
Next, toe out slightly.
If you find that it pushes on through / out of corners, play with the roll bars. I tend to end up with front full stiff, and rear 1 from stuiffest, with a reasonable amout of rake on the car - I'd offer settings, but have ended up with a different setup for each Caterham I've tracked (mostly because the measuring point I used changed as the chassis changed 2001 - 2005 - 2009.
Getting the set up right is great fun though, esp since most of it can be done in just a few minutes.
All of the aboe is, of course presuming your tyre pressures are set right - if the balance changes significantly from start - end of a session, they might not be.
Good luck with the learning curve, it's steep at first but loads of fun.
Gump
Great advice above on rake, toe and roll bars.
LSD will not affect turn in unless you are trying to turn in and powering on hard and whilst there is grip it would push, until breaking traction and you would get oversteer.
LSD's are great not only in getting the power down out of corners but also stabilizing the rear of the car under trail braking. I found I could brake later and harder and of course get on the gas much earlier and get traction and that helped lower laptimes.
In the wet an LSD make snap power oversteer much more progressive and controllable, fish tailing was a thing of the past. Again essential for good progress.
LSD will not affect turn in unless you are trying to turn in and powering on hard and whilst there is grip it would push, until breaking traction and you would get oversteer.
LSD's are great not only in getting the power down out of corners but also stabilizing the rear of the car under trail braking. I found I could brake later and harder and of course get on the gas much earlier and get traction and that helped lower laptimes.
In the wet an LSD make snap power oversteer much more progressive and controllable, fish tailing was a thing of the past. Again essential for good progress.
Unless you're an heroic big hairy racer type, with love and hate tattooed across your knuckles and spend more time on the rumble strips than the black parts of the track, I'd recommend the ATB. It gets the job done smoothly and consistently and doesn't ruin the turn in behaviour.
My money is on ADC's motor having armfulls of toe in and no rake.
My money is on ADC's motor having armfulls of toe in and no rake.
Guys, I am now at the risk of trying to sound the clever kid on a forum. Experts - please correct me where wrong =)
To the 2 posters above, at the risk of sounding like a total knob end (teaching granny to suck eggs) etc, I'm going to go through the way I set up a 7 as an ex- kart racer, car pit skivvy, and keen track day ameteaur. It won't be the best way to get to the end result, but it's simple, understandable, and above all - very satisfying to know you set your car up yourself, rather than paying somone else to do so. It is also for a K series, wide track narrow body car.
Starting point:
Set front ride height for wishbones level (seems to give good sump height). Set FR 1mm higher than FL (RHD)
Set rear ride height to be approx 15mm rake, I always leave it flat because we're 2's up easily as much as solo driver.
Set toe according to spec (slightly in)
Set front and rear ARB's to middle.
Do first session, get a feel for the car. Try to look for _overall_ behaviour - front vs rear.
If you want more turn in, raise the back. If you want more rear end, drop the back. I always leave front set because it is dictated for me by bumpy roads full of catseyes.
If you're changing the ride height, do 5mm at a time. It seems to be approx 3 full turns of the rear damper, but it's visible when you do it. i always use a caliper rather than turns, because invariably I lose count.
Once you have the car better (go past ideal, it's fun and a good learning experience), time for roll bars.
For rol bars, you need to be concious of how the car is moving mid corner. If the car pushes wide on exit, it can be one of several things:
Rear end too soft: back goes all "squidgey", you feel loading from rear outside - front goes light - pushes on - stiffen rear ARB.
Front end too soft:
Weight ends up on otside front. Inner front loses effectiveness - only 1 front wheel loaded = 1 contact patch = wash out understeer.
Front too stiff:
Front end feels "dead" - it's like it's not working, and the outer tyre never really digs in. Soften it off, and then advance as above.
Finally, we get to toe.
So, you have the mid coner grip. It no longer pushes on on exit (and hopefully can tuck in with a bit of right foot, depending on power / tyre ratio).. What about that all important initial bite / turn in?
Toe the car out slowly. Toe is a sensetive measure, and should always be done on each track rod equally. The "official" setting is slight toe in, but as you reduce this (and even go toe out), you increase "dartiness". Bear in mind toe does this at all moments - a toed out car is horrible to drive in a straight line. I say do this slowly, because at full braking, you by now have a car that is pitched down at the front, toed out (or less toe in), and on full pich forwrds during braking. If the front toe makes it jittery, think whats now happening piling into that left hander afte r the gooseneck on Cadwell - it's hairy.
IMO for all track day guys (like me), out right speed is secondary to being able to drive it the next day - leave the "get straight to the fastest setting" to the pros - they'll be faster anyways. My method is very heath robinson, but hopefully should never result in a change so drastic that you put it off - this is why the inpts are slow.
Happy playing
Gump
PS - never forget to sot pressures after every run - last time out, I was carrying so much more speed at Anglesey after 2 sessions I had to let 2 PSI out of the 'now more loaded' front left by 11.30. It started horribly understeery tho!..
To the 2 posters above, at the risk of sounding like a total knob end (teaching granny to suck eggs) etc, I'm going to go through the way I set up a 7 as an ex- kart racer, car pit skivvy, and keen track day ameteaur. It won't be the best way to get to the end result, but it's simple, understandable, and above all - very satisfying to know you set your car up yourself, rather than paying somone else to do so. It is also for a K series, wide track narrow body car.
Starting point:
Set front ride height for wishbones level (seems to give good sump height). Set FR 1mm higher than FL (RHD)
Set rear ride height to be approx 15mm rake, I always leave it flat because we're 2's up easily as much as solo driver.
Set toe according to spec (slightly in)
Set front and rear ARB's to middle.
Do first session, get a feel for the car. Try to look for _overall_ behaviour - front vs rear.
If you want more turn in, raise the back. If you want more rear end, drop the back. I always leave front set because it is dictated for me by bumpy roads full of catseyes.
If you're changing the ride height, do 5mm at a time. It seems to be approx 3 full turns of the rear damper, but it's visible when you do it. i always use a caliper rather than turns, because invariably I lose count.
Once you have the car better (go past ideal, it's fun and a good learning experience), time for roll bars.
For rol bars, you need to be concious of how the car is moving mid corner. If the car pushes wide on exit, it can be one of several things:
Rear end too soft: back goes all "squidgey", you feel loading from rear outside - front goes light - pushes on - stiffen rear ARB.
Front end too soft:
Weight ends up on otside front. Inner front loses effectiveness - only 1 front wheel loaded = 1 contact patch = wash out understeer.
Front too stiff:
Front end feels "dead" - it's like it's not working, and the outer tyre never really digs in. Soften it off, and then advance as above.
Finally, we get to toe.
So, you have the mid coner grip. It no longer pushes on on exit (and hopefully can tuck in with a bit of right foot, depending on power / tyre ratio).. What about that all important initial bite / turn in?
Toe the car out slowly. Toe is a sensetive measure, and should always be done on each track rod equally. The "official" setting is slight toe in, but as you reduce this (and even go toe out), you increase "dartiness". Bear in mind toe does this at all moments - a toed out car is horrible to drive in a straight line. I say do this slowly, because at full braking, you by now have a car that is pitched down at the front, toed out (or less toe in), and on full pich forwrds during braking. If the front toe makes it jittery, think whats now happening piling into that left hander afte r the gooseneck on Cadwell - it's hairy.
IMO for all track day guys (like me), out right speed is secondary to being able to drive it the next day - leave the "get straight to the fastest setting" to the pros - they'll be faster anyways. My method is very heath robinson, but hopefully should never result in a change so drastic that you put it off - this is why the inpts are slow.
Happy playing
Gump
PS - never forget to sot pressures after every run - last time out, I was carrying so much more speed at Anglesey after 2 sessions I had to let 2 PSI out of the 'now more loaded' front left by 11.30. It started horribly understeery tho!..
The ATB diff is horrific in a seven - just plain nasty. If you want to have fun, get a proper diff. Don't buy a diff to try and help you go quicker or anything though - it's a very marginal performance gain in all but experienced hands. Properly good fun for d!cking about at roundabouts and T-junctions though. I miss having a road seven :-(
Jonny
BaT
Jonny
BaT
Well although in the specs. here
http://www.rsperformance.co.uk/levante_technicalsp...
it says LSD, I am informed by someone close to Russel Savory that the Levante has a Quaiffe TBD.
He apparently tried a plate type diff, as it was specified by the customer.
After taking the car for a spin, he brought it straight back, and swopped it to back to the TBD. At least that is what I was told.
Although that is an extreme. It's a personal choice TBD or LSD. They both have their + and - points.
I recon if you're going to track/hilclimb, Plate diff.
For road, TBD.
Either way, I wouldn't have a Caterham with an open diff.
http://www.rsperformance.co.uk/levante_technicalsp...
it says LSD, I am informed by someone close to Russel Savory that the Levante has a Quaiffe TBD.
He apparently tried a plate type diff, as it was specified by the customer.
After taking the car for a spin, he brought it straight back, and swopped it to back to the TBD. At least that is what I was told.
Although that is an extreme. It's a personal choice TBD or LSD. They both have their + and - points.
I recon if you're going to track/hilclimb, Plate diff.
For road, TBD.
Either way, I wouldn't have a Caterham with an open diff.
Thanks for all the input on this. I now have another question and one bit of confusion:
1. Question: Despite Some Gump's fantastic advice above and strong suggestion to DIY rather than get someone else to prep the car, given my worklife and inclination to get the car "sorted" first before I start making further incremental changes, I am thinking of getting someone to have a first go at the setup. Would anyone recommend a good specialist in the south Oxfordshire / Berkshire area?
2. Confusion: From the posts so far, there seem to be two camps on which diff to get, split pretty equally between the gear type quaife offering or the plate type. More people appear to have said that the plate type offers a more progressive experience but others have suggested it's more for committed racers only but not sure why. Any views on the relevant pros and cons and finally any views of the relative noise generated by the different kinds - This is, after all, mainly a road car so deafening noise from the rear axle doesn't seem like a good plan.
Thanks again,
Andy
1. Question: Despite Some Gump's fantastic advice above and strong suggestion to DIY rather than get someone else to prep the car, given my worklife and inclination to get the car "sorted" first before I start making further incremental changes, I am thinking of getting someone to have a first go at the setup. Would anyone recommend a good specialist in the south Oxfordshire / Berkshire area?
2. Confusion: From the posts so far, there seem to be two camps on which diff to get, split pretty equally between the gear type quaife offering or the plate type. More people appear to have said that the plate type offers a more progressive experience but others have suggested it's more for committed racers only but not sure why. Any views on the relevant pros and cons and finally any views of the relative noise generated by the different kinds - This is, after all, mainly a road car so deafening noise from the rear axle doesn't seem like a good plan.
Thanks again,
Andy
A plate diff. (LSD) needs to be set up correctly. It will fully lock.
A TBD works with gears and never fully locks, much nicer for a road car, but no good for track work, as it doesn't like kerb hopping.
You don't "need" one, but without it you'll be spinning away your power on the inside wheel.
It's also great fun with a TBD/LSD sliding the car around roundabouts on the throttle!
Interesting article on LSD's on Angus's website here.
http://www.mycaterham.com/66828/117416.html
and an explaination of the Quaife website here
http://www.quaife.co.uk/differentials
I chose the Quaife for myself, and they are very good to deal with.
I bought the whole unit with a brand new case. I think it was about 800 quid.
I think just the diff. is half that. But You'll have to get someone to fit it into your case, unless you understand the mysteries of what goes on in there! You can buy online too.
A TBD works with gears and never fully locks, much nicer for a road car, but no good for track work, as it doesn't like kerb hopping.
You don't "need" one, but without it you'll be spinning away your power on the inside wheel.
It's also great fun with a TBD/LSD sliding the car around roundabouts on the throttle!
Interesting article on LSD's on Angus's website here.
http://www.mycaterham.com/66828/117416.html
and an explaination of the Quaife website here
http://www.quaife.co.uk/differentials
I chose the Quaife for myself, and they are very good to deal with.
I bought the whole unit with a brand new case. I think it was about 800 quid.
I think just the diff. is half that. But You'll have to get someone to fit it into your case, unless you understand the mysteries of what goes on in there! You can buy online too.
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