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First Autocross with the "new" Caterham


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Wish I was at the point I could start blaming the car! Yesterday I managed to induce understeer, oversteer and at least one no-steer 4 wheel slide! I have found that the Caterham will tolerate more braking that I anticipated before it gets upset and that the speed of steering inputs is critical. When I get it right the car dances on the edge of traction well. I'm running factory alignment settings with just a hint of front toe in and equal front weights. Tires are 7 year old (I know...) 205/45-16 Toyo Proxes. Once I get consistent I'll get some new tires, seems they don't wear on the Caterham, not heavy enough... Sure is fun autocrossing these things.

 

Andy

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Wish I was at the point I could start blaming the car! Yesterday I managed to induce understeer, oversteer and at least one no-steer 4 wheel slide! I have found that the Caterham will tolerate more braking that I anticipated before it gets upset and that the speed of steering inputs is critical. When I get it right the car dances on the edge of traction well. I'm running factory alignment settings with just a hint of front toe in and equal front weights. Tires are 7 year old (I know...) 205/45-16 Toyo Proxes. Once I get consistent I'll get some new tires, seems they don't wear on the Caterham, not heavy enough... Sure is fun autocrossing these things.

 

Andy

 

It really is fun autocrossing these things isn't it? My season has ended with fall/winter weather having moved in but even after 20 years I still get sad when it ends.

 

I might suggest that one of the things hurting your consistency is the old tires. It's very hard to drive around having old tires. Do yourself a favor and get some new tires (yes.....7 years is old) and your driving will improve to match the new grip. Worth every cent.

 

dave

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I used to auto cross a Caterham back in Ontario in a previous lifetime... I found the biggest difference I made was switching to 13” wheels and Hoosier Street legal auto cross tires.. super soft and sticky but still theoretically street legal.... even on a Caterham they only lasted for o e season of auto cross, but certainly helped to make up for my lack of driving ability ;-)

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Dave and Clarko,

You guys going to provide me with support if I order a set? They should work in light rain, right :) !

 

https://www.tirerack.com/tires/tires.jsp?tireMake=Hoosier&tireModel=A7&partnum=045ZR6A7&vehicleSearch=false&fromCompare1=yes

 

Must work on justification/rationalization strategy... Clarko says they'll last a year... Want maximum grip for safety... It doesn't really rain in N. California any more... They'll be quieter... There's more rubber to distribute the wear... Those "five-dash circumferentially oriented grooves" are tread...

 

 

Andy

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Dave,

Here's my notes from when we set it up:

Front Toe: .18deg .17deg in (EDIT: .04deg in .04deg in, bad notes!?!?)

Front Camber: -1.2deg

Front Caster: 5.8deg 5.9deg

 

Rear Thrust Angle: 0deg

Rear Camber: -1.5deg

 

Essentially just factory settings with a bit less toe and more measured caster. I say "measured" because we started with factory shims and then matched it side to side. I was not terribly worried about the reading as long as it was in the ballpark and matched. I played with the toe a bit since it was pretty goofy when I purchased the car and I wanted to find how it drove at a variety of settings. This worked well for normal driving. I have not felt the need to play with toe-out for the autoX. I will say too much toe-in makes these things miserable!

 

Corner Weights, full tank, 1303lbs.

LF 313, RF 318

LR 327, RR 345

 

FARB 5/8"

RARB std. one hole from full soft

 

TP 16psi.

 

The car is an '03 SV.

 

If you have any comments or suggestions I'm all ears.

 

Andy

Edited by ashyers
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Dave,

Here's my notes from when we set it up:

Front Toe: .18deg .17deg in

Front Camber: -1.2deg

Front Caster: 5.8deg 5.9deg

 

Rear Thrust Angle: 0deg

Rear Camber: -1.5deg

 

Essentially just factory settings with a bit less toe and more measured caster. I say "measured" because we started with factory shims and then matched it side to side. I was not terribly worried about the reading as long as it was in the ballpark and matched. I played with the toe a bit since it was pretty goofy when I purchased the car and I wanted to find how it drove at a variety of settings. This worked well for normal driving. I have not felt the need to play with toe-out for the autoX. I will say too much toe-in makes these things miserable!

 

Corner Weights, full tank, 1303lbs.

LF 313, RF 318

LR 327, RR 345

 

FARB 5/8"

RARB std. one hole from full soft

 

TP 16psi.

 

The car is an '03 SV.

 

If you have any comments or suggestions I'm all ears.

 

Andy

 

 

 

Cool - these are my random thoughts based on what ran on a Birkin years ago and what I've learned with my current Westfield -

 

- if you are running any kind of DOT radial tire (even something like a Hoosier A7) you could benefit from more camber all around. Those tires need a good bit, especially in front, for them to work as intended. If the car turns in well but then fades into understeer my first thought is front camber. I run a non-DOT bias ply tire and they need much different alignment....but if I were running 888's or A7's I'd set my car up with a good 2.5° in the front and maybe 2.0° camber in the rear and see how it goes.

 

- I see you measured the toe in degrees and off the top of my head I don't know how that translates to millimeters at the rim. That said I would not be running any toe-in in the front. I'd set it for 0 toe-in in front. Some will go with toe out (I use 1 mm toe out each side in the front) and it aides in quick turn-in but can make the car feel twitchy. But having toe-in in the front is a quick way to understeer.

 

- I don't see any toe numbers for the rear listed. I'd be looking at setting them at about 1-2mm toe in each side. This aides in high speed stability and helps tame snap oversteer in slaloms and transitions.

 

- I know nothing about your ARB's but I will say that in general you can take the rear one off and make a lamp out of it. If you are driving aggressively (as one needs to do to put down quick times) it will only hurt you in the snap oversteer department. You want to keep the front one as it helps keep the inside rear tire from lifting while cornering.

 

------------------------

 

So - as I recall you are having issues with understeer.....is that right? If so the car set up certainly could be a large factor in that. Your driving could also be a big factor. Tires don't grip unless they have weight on them and if you enter a corner and just fade off the gas and then turn it will understeer. One needs to brake hard to get a weight shift to the front to get those tires to bit. Charge into the corner, lift off the gas and hit the brake as fast as your foot will move and brake hard.....come off the brake and as you turn the wheel. With all that braking shifting weight forward it will not understeer even a little bit.

 

And...If you pass the apex of the turn and with the wheel still turned nail the gas it will probably understeer a lot. Getting onto the gas shifts weight rearward and off the front tires so they will push....while the rears have lots of weight and they will grip....and then you have understeer. If you'd done the above and braked hard and late into the turn and carried as much speed as possible you can start adding gas as you unwind the wheel and you won't make a big weight shift this way. The caveat here is if you have enough grunt you can give it the boot and get the car to rotate on the gas and point in the direction you want to go without much push. This feels fast but can be slow. Showboating is slow.

 

In the end you need to be aggressive to get the most out of it. At first you will do it wrong because you are human like the rest of us and this will result in silly moves like spinning. But you'll feel it and the car will respond with more practice.

 

I hope that makes the water clearer and not muddier.

 

dave

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Dave,

I think johncg was having understeer issues. I've likely got driver issues!

 

You and Croc's points about managing weight transfer on entry played out Sunday. I found I can brake much more aggressively and plant the nose of the car, it'll turn in.

 

Lots of camber huh? How was braking and tramlining at 2.5deg? I drive the car quite a bit and have not run those settings so I'm curious. Next time I have it on the pad I'll have to record the # of turns to 1.5, 2, 2.25 and 2.5 so I can play at the autoX. Hopefully it won't foul up the toe too much.

 

The total front toe works out to a hair over 1/8" (EDIT: .032", bad notes!?!?!?) in at the tire in the front. I could dial it to 0 easily enough and give it a try.

 

Adjusting rear toe will involve some shimming, so that's a bit of a pain. Right now it's a hair less than 1/8" in total.

 

RARB is easy, pull off and less weight!

 

I really appreciate the feedback. It is helpful for determining a direction to go. Ultimately I'm not out for the fast time of the day, I just enjoy improving my driving and tinkering with the car. I guess I need to be careful of tuning to the old tires...I can't buy another set! Hopefully the balance will not change radically.

 

Andy

Edited by ashyers
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Right you are - I must have been thinking of the other guy with the understeer. Sorry about that.

 

You are right on - weight shift is everything. Good on you for getting the feel for that! The attached photo show how much grip one can get with weight shift....the weight has shifted to the rear allowing it to hang on tight. Just look at the sidewall flex on that rear tire. It's working very hard.

 

I've not found tramlining to be a real issue on the road when using lots of camber. Toe out can make it feel funny but camber has never been an issue for me.

 

Unfortunately it seems very unlikely that you can make major changes in camber up front without messing with the toe a lot. Dues to the geometry of most front suspension and the Ackerman effect any changes in camber typically result in large toe changes. So I'd say that you might need to pick a camber setting and then set the toe to that.

 

Speaking of front toe-in....1/8" is a good bit - I suspect too much. I'll bet if you back that off to 1/16" - 0" toe in that it would feel better on the road and solo course. Front toe tends to make them feel a bit numb and you're no doubt leaving some of the fun on the table.

 

Having 1/8" toe-in in the rear is a great place to start.

 

One thing about alignment - most alignment shops will charge you real money and you may, or may not, get what you want. It's not rocket surgery if you have basic tools. One tool you can make for small money is a string box. I made one for my Westie using electrical conduit and the two sections bolt directly to the car. The conduit has shallow hacksaw slots on each end to hold the string in place. I can bolt it on and check alignment in less than 5 minutes. It takes more time to put the ballast in the driver's seat (worthless without this on a light car) than it does to set up the bars. There's no reason to pay for an alignment when you can do it at home with tools that cost less than $20. Want to make a change for the weekend's solo event?....no problem. It becomes so fast and easy that you can tweak and learn and get very quick and cheap feedback.

 

I hope that helps.

 

dave

 

 

 

Dave,

I think johncg was having understeer issues. I've likely got driver issues!

 

You and Croc's points about managing weight transfer on entry played out Sunday. I found I can brake much more aggressively and plant the nose of the car, it'll turn in.

 

Lots of camber huh? How was braking and tramlining at 2.5deg? I drive the car quite a bit and have not run those settings so I'm curious. Next time I have it on the pad I'll have to record the # of turns to 1.5, 2, 2.25 and 2.5 so I can play at the autoX. Hopefully it won't foul up the toe too much.

 

The total front toe works out to a hair over 1/8" in at the tire in the front. I could dial it to 0 easily enough and give it a try.

 

Adjusting rear toe will involve some shimming, so that's a bit of a pain. Right now it's a hair less than 1/8" in total.

 

RARB is easy, pull off and less weight!

 

I really appreciate the feedback. It is helpful for determining a direction to go. Ultimately I'm not out for the fast time of the day, I just enjoy improving my driving and tinkering with the car. I guess I need to be careful of tuning to the old tires...I can't buy another set! Hopefully the balance will not change radically.

 

Andy

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DSC_9073.jpg

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Dave,

HOLY CRAP is that a bunch of tire!!!!!! I agree that outside rear is working :) ! That's a great photo, pretty informative about the setup's behavior.

 

Per your advice I think I'll try this:

 

Front toe: 0 to a RCH in, just enough to keep it on the "in" side of 0 so it doesn't dither.

 

Front camber: I'll play with camber. Per my notes it changes .25deg/turn so I'll measure toe before and after camber changes and then figure out how many flats I need to add/subtract get the toe sorted out.

 

* Disconnect RARB (edit, forgot!)

 

Alignments I have covered. I'm to picky/cheap to shop it out and I've done a few. The toe bar setup you made looks like it works well. Where did you anchor it to the chassis? It's great that you don't need to pull the nose.

 

Andy

Edited by ashyers
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Dave,

HOLY CRAP is that a bunch of tire!!!!!! I agree that outside rear is working :) ! That's a great photo, pretty informative about the setup's behavior.

 

Per your advice I think I'll try this:

 

Front toe: 0 to a RCH in, just enough to keep it on the "in" side of 0 so it doesn't dither.

 

Front camber: I'll play with camber. Per my notes it changes .25deg/turn so I'll measure toe before and after camber changes and then figure out how many flats I need to add/subtract get the toe sorted out.

 

Alignments I have covered. I'm to picky/cheap to shop it out and I've done a few. The toe bar setup you made looks like it works well. Where did you anchor it to the chassis? It's great that you don't need to pull the nose.

 

Andy

 

Cool - I wouldn't worry about maintaining a small amount of toe-in....there's no tipping point that happens when you cross from toe-in to toe-out. In fact when the car moves up and down with weight shift the toe changes anyway. And unless you have solid suspension bushings they deflect when you hit the brakes to change the toe. So toe is kind of all over the place and there's nothing sacred about it.

 

I have rivnuts that are mounted in the nose to support my front splitter and i just take these out and the string box bolts into those inserts. In the rear the bar affixes to the top of my rear diffuser.

 

 

Dave

DSC_0107.jpg

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  • 2 weeks later...

Dave,

Just edited the posts above. I put the car back on the pad yesterday and found out my notes were from one of our first iterations of toe changes. The setting is actually .04deg/side or .032" total in, so not far from what you're recommending.

 

Andy

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Dave,

I'm trying your suggestions.

Front Toe: 0deg

Front Camber:-2deg

RARB: Disconnected

 

I'm not going to an AutoX until the 14th, but the difference is apparent on the street. 0 toe makes steering slightly vague on center, but frees things up a bit, and the feel is good. There were no issues with tramlining on the freeway. The lack of the RARB was apparent when zipping to work this morning and rounding a bumpy turn I take daily. Less skip, more grip. I'll have to check the tires after the AutoX and see how the camber has affected wear. I didn't go the full 2.5deg. I wanted to try 2deg first.

 

Andy

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