Camber settings - technical advise request

[Neophyte]

This a bit a long post, apologies but hopefully of interest to more than just me

So I read all of http://cliotrophy.co.uk/forum/viewtopic ... 74&start=0
very interesting, noting the follwing

According to the dealer's data sheet the front settings are:
Camber: Negative 0.17' +/- 30'
Toe-out :0.25' +/- 17'
Mine came with 0.40' negative and 0.10' toe-out. For track work I intend to convert to 2.00' negative and probably 0.20' toe-out. .. I know someone who has recently taken his car to a Clio Challenge specialist, where the front was changed to the settings that I mention above and they also used shims to adjust the back to 1.30' negative (although mine seems to be at that already, c/w 0.20' toe-in) and his is stunned by the extra front end grip. .. FYI the Challenge cars run over 3.30' f & r, which fits in with michelin's recommendations for touring cars,

Will be very interested in any feedback

..
At the front 2.00 negative may aggravate tyre wear a bit, but as when you are leaning on it, there will be a tendency to wear the outside, more camber will tend to compensate. My road car is very nose heavy diesel and at 1.30' (my modifed setting) has very even wear, running at 0.00 toe.

I would certainly go for 1.30 - 2.00 and 0.00 - 0.20' toe-out. You can adjust by using proprietory camber bolts - although I will probably extend the upper of the two bolts holes in the strut where it is connected to the hub carrier by 2 mm, as I am more comfortable with maintaining the effective diameter of the bolts. Camber bolts have the effect of reducing the operative diameter from 14 mm to 12mm. One of our analytical engineers ran a check and reckoned that to maintain the clamping load, this does move it quite a lot further up the tensile failure curve. ..

I am considering going for the 12mm bolts (-2 deg, 0.00 toe-out) but am now thinking about increased risk of failure.. If I go the 12mm bolt route, then it fails, going back to 14mm is not possible right?

Done a bit of calling around to see about solving this camber issue, and Aurok Ltd were able to give me advice on this and suggest a solution.

They have done camber set-ups for quite a few R'sport Clio's now, and have advised me to change the front camber to -2.00 degrees, but to leave the back alone.

Car is booked in for Thursday, so if everything goes well, I should have my new 'optimised' front suspension geometry for the Trophy's first trackday this Saturday. Aurok estimated the work, which includes the camber bolts and 4 wheel alignment, at £100 which seems pretty reasonable. I'll post back my feedback about the company and the work later on in the week.

Olis was increased bolt failure risk a concern for you? How have you found your car on track since?

then I read all of this
http://cliotrophy.co.uk/forum/viewtopic.php?t=91

The problem is that they need a very high clamping load - recommended 170 NM in the Clio Challenge Manual and I am not sure whether the 12mm's are then still in their safe working range. Will have to check with my technical colleagues at work.

George K Did you get a chance to obtain any input from you colleagues re 170NM torque? Have you decided how you will proceed with your hill climbing camber set up work?

I was thinking of visiting http://www.markfish.co.uk who seemed to know his stuff when I spoke to him, anyone had experience?

Any and all input most gratefully received

 

[OliS]

Hello mate!

Camber bolt failure is not a concern for me anymore, the guys who sorted the camber on my car were adamant that the std bolts would be fine. I am only running -2.00 degrees on the front, which is not actually that extreme, the rears were left alone as they came from the factory with -1.70 degrees with is a bit more than I would have liked, but as they matched and the fact that using shims to adjust the rear would have tripled the cost and time that it took to get my car sorted, I thought it best to leave it alone for now.

The difference in drive from getting the camber sorted is immense, everything feels more planted especially through corners, and the car just seems to drive alot straighter - it is easier to put the car exactly where I want on the road. I've only done one trackday since getting the camber sorted, and the car performed very truthfully, the steering and cornering performance was excellent.

I do feel that despite the dampers being very firm on the Trophy, the springs could be a little stiffer as I feel that the Trophy would benefit from less roll, however I would be worried about loosing some of the Trophy's awesome bumpy B-road handling ability by fitting stiffer springs. Was really interested in 7Mat's thread the other day about having his Trophy lowered, may well have to have a conversation with Mark myself in the near future, and if I did change the springs I would probably change the camber settings again at that point, less rear camber, maybe more front...

 

[donkey]

I've been doing some development work on this, this very day! I was at Goodwood today, not the worlds twistiest circuit - but using a standard clio trophy and changing the camber and toe settings I was able to get an immense improvement in turn in. Probably most importantly increasing the camber prevents the tyres trying to roll off the edges of the wheels. I work using tyre temperatures to tell me how the tyres are working, I was able get really consistent temperatures across the face of the tyre with no hot spots on the edges, and even after 8 sessions no feathering or excessive overheating occurring.

Using camber bolts is a standard and accepted practice, although a smaller diameter they are usually of a higher tensile strength - at least 10.9. The torque figures are usually given on the packet and vary from manufacturer to manufacturer. The only other way to do it is to use adjustable top mounts ( you can adjust castor too then) or to bravely start opening up the top hole in the damper.

Upsides, more consistent and even tyre use (and therefore wear on track), the front end has much more point.

Downsides, you will wear the inner edges quicker on the road, there is more noticable torque steer and pull from odd road cambers, errr thats about it, it could be argued that theoretically braking and traction could be impaired but I have not found this in practice.

*WARNING BLATANT PLUG ALERT*


The clio is my car, I do this thing for a living, I usually work on racecars and dedicated trackcars but couldn't resist fiddling

I'm happy I've got a very good trackday set up if anyone wants any help

www.racecardoctor.com



* PLUG OVER*


For what its worth, very impressed with the clio - its B road body control is seriously impressive

 

[Neophyte]

Hello mate!

Camber bolt failure is not a concern for me anymore, the guys who sorted the camber on my car were adamant that the std bolts would be fine. I am only running -2.00 degrees on the front, which is not actually that extreme, the rears were left alone as they came from the factory with -1.70 degrees with is a bit more than I would have liked, but as they matched and the fact that using shims to adjust the rear would have tripled the cost and time that it took to get my car sorted, I thought it best to leave it alone for now.

The difference in drive from getting the camber sorted is immense, everything feels more planted especially through corners, and the car just seems to drive alot straighter - it is easier to put the car exactly where I want on the road. I've only done one trackday since getting the camber sorted, and the car performed very truthfully, the steering and cornering performance was excellent.

I do feel that despite the dampers being very firm on the Trophy, the springs could be a little stiffer as I feel that the Trophy would benefit from less roll, however I would be worried about loosing some of the Trophy's awesome bumpy B-road handling ability by fitting stiffer springs. Was really interested in 7Mat's thread the other day about having his Trophy lowered, may well have to have a conversation with Mark myself in the near future, and if I did change the springs I would probably change the camber settings again at that point, less rear camber, maybe more front...

Most interesting, thank you. I have now also read http://cliotrophy.co.uk/forum/viewtopic ... highlight=
the thread you mentioned which I had missed
It has me thinking about brake mods whilst I am up seeing Mark about camber adjustment. I can see this getting expensive

..Using camber bolts is a standard and accepted practice, although a smaller diameter they are usually of a higher tensile strength - at least 10.9. The torque figures are usually given on the packet and vary from manufacturer to manufacturer. The only other way to do it is to use adjustable top mounts ( you can adjust castor too then) or to bravely start opening up the top hole in the damper.

Upsides, more consistent and even tyre use (and therefore wear on track), the front end has much more point.

Downsides, you will wear the inner edges quicker on the road, there is more noticable torque steer and pull from odd road cambers, errr thats about it, it could be argued that theoretically braking and traction could be impaired but I have not found this in practice.

Donkey, thanks very informative

 

[George K]

I eventaully decided to use different bolts - 12 mm diameter instead of 14, and went for aircraft grade 12.9 bolts with a Spiralock lock nut. For M12 x 1.75 they recommend 180 NM, which provides more than enough clamping load.

So far they have been fine, and I have now done several events. Am running 2.00 negative and 10' toe out. No weaving under braking and really good in the wet, (very wet Wiscombe hillclimb) but still does not cure understeer round very tight hairpoins - as I said in the post on lowering, that is largely down to the driver (slower in is better), possibly track tyres and eventually a limited slip diff.

The car does roll quite a lot - have some surprising photos, and three wheels with the greatest of ease. Largely due to the very limited droop travel at the rear.

My biggest problem is the first application of the brakes, which at Wiscombe is just after a crest, so the car is light and then there is a narrow tightish right hander - the car pulls left and the brakes feel quite soggy. I would have thought that road pads would be OK on the first application, there is no way to warm them up before the run - EBC Greenstuff seem to have good initial bite. Sprints and hills are not fade critical.

 

[donkey]

you'll be fine with 12mm bolts, and they are top spec at 12.9. Did you use a plain shank or ones with a cam on?

The trophy is quite soft as soon as you put it on a track, but its a road car after all and has to cope with rough surfaces not found on track. You are spot on about rear droop - its really limited.

There isn't a lot of ackermann built into the steering so some toe out helps no end.

Are you getting understeer on turn in/apex/or on power application?

I've used 3 degree negative and found a benefit in slower corners, but you do tend to start to overheat in the inner edges - this might actually be an advantage on the short runs you do to get some heat into the tyres, running more toe out would help heat build up as well but you can only go so far before it slows you down and causes instability especially under braking.

Have fun getting faster!




www.racecardoctor.com

 

[George K]

I used plain shank bolts as I had calculated that they would provide the right amount of camber.

I do agree that it is quite soft in roll which is a problem, on the sprint circuit (Dunkeswell - which is bascially a go-kart track, but 7 metres wide, but not so much on the hillclimb - Wiscombe is a bit undulating and all cars favour a softer set-up).

The understeer is at all stages on 180 plus bends, they really are very tight. As I have said before this is probably as much donw ot my lack of skill as a problem with the car.

I had started with a bit less toe in case the camber aggravated straight line wandering - will try a bit more and will review more camber after a few more events. Presumably road tyres need more camber than track tyres because of softer sidewalls (am really limited for 205/45 x 16 to Kumho Ecsta V70A). Do you think lack of Ackermann is an issue, as I have even seen racing cars runing anti-ackermann - it seemed to be a bit of fashion type issue and most testing found it was down to driver preference. I would guess is depends on how much rear steer there is, as that will determine the position of the instantaneous cnenre of rotation? (Don't think that is BS!!?)

 

[Neophyte]

I eventaully decided to use different bolts - 12 mm diameter instead of 14, and went for aircraft grade 12.9 bolts with a Spiralock lock nut. For M12 x 1.75 they recommend 180 NM, which provides more than enough clamping load.

So far they have been fine...

GeorgeK I had hoped you might be able to contribute , most informative thanks.
Do you have the details on your bolts? (manufacturer/part #)

Much more of this of this type discussion risks even me actually having half a clue :shock:

you'll be fine with 12mm bolts, and they are top spec at 12.9. Did you use a plain shank or ones with a cam on?... There isn't a lot of ackermann built into the steering so some toe out helps no end.

Are you getting understeer on turn in/apex/or on power application?...

www.racecardoctor.com

Cheers donkey, again most informative. I know I asked for technical advise... But I had to Google your last post

Incase anyone else wondered about ackermann...

"Toe and Ackermann angles cannot be discussed separately. A turning car requires the inside and outside tires to follow arcs of different radii. The inside tire must follow a smaller arc, so it really must point inwards a bit more to avoid scrubbing across the pavement. Both toe and Ackermann point the tires in slightly different directions, but Ackermann does this through the geometry of the steering arms to affect the change in proportion to steering angle; toe is static. Both are used to balance the straight line stability, initial turn-in response and mid corner behavior. Like caster offset, toe angle can be used to stabilize the car in a straight line while using Ackermann to transition into proper geometry for cornering. Race cars tend to need less Ackermann to corner well, due to the high slip angles of the tires moving the instant center of the turn much farther forward. In the rear, virtually all cars are set up with zero or slight toe-in for stability and/or some further toe-in action under cornering loads to generate mild understeer at the limit. Toe-out in the rear geometry must be avoided at all costs, or you end up with a frighteningly unstable car"

[Clipped from http://www.drivingsports.com/a/template ... z=7&page=2]

 

[George K]

The bolts are Unbrako socket heads - should be available from any reputable supplier - much more difficult was finding the nuts - we used Speciality Fasteners who are based in Totnes in Devon - they should be able to supply the bolts as well - just make sure that they are 12.9 spec. I also made up some 5 mm thick washers so as to spread the laod more evenly across the 14 mm hole in the strut.

Your notes on Ackermann are interesting and generally quite a good guide. The problem is that the rea greometry can be more complex and does have a knock on effect on the front. Also very modest amounts of rear toe out can be used with great success - but if you get it wrong the car can be a total nightmare. As a generalisation you need toe-in at the rear on fast sweeping type bends, but if dealing only with tight low speed corners then a tad of toe-out can help. There certainly is an argument for going to parallel at the rear - after all that is what most live axles run! Then the toe-in is to allow for toe change from bush distortion etc. Not sure that my somewhat ageing reactions are up to this extra challenge!

 

[donkey]

http://www.smithees-racetech.com.au/ackerman.html


all you wanted to know about ackermann

the summary is: nobody really knows for sure, lots of theories, there is a fashion element, with anti ackermann being mainly used in the 1960s, depends a lot on tyres

slow corners are always going to be about being patient on the throttle in a FWD car - you have to imagine the traction circle - you are canted well over maximum lateral grip, as soon as you apply throttle or brake its going to go outside the circle, rob front end grip - hey preston understeer

are these 180s so tight you can use the handbrake?

 

[FunkyMunky]

ok..... to drag up an old thread again on a much discussed topic.....

how will the handling of the car be affected if you run more than -2 degrees of camber at the rear without making an adjustment to the front of the car which based on previous posts i have read tends to run at somewhere roundabout -1 degrees?

 

[Cue]

nice one gaz, i'm all confused again having read Donkey's and George's posts again.......

i'm stil getting my head around -2 camber at the front....

 

[FunkyMunky]

anyone for anyone fancy answering this question?!

 

[George K]

The rear is not heavily laden, so the only object of rear camber is to compensate for roll rather than sidewall distortion. If anything I would tend to run less camber so as to encourage the back end to move out more readily - not that I am that brave or skilfull when driving between trees and walls. Similarly quite a lot of rear toe-in is intended to make the car user friendly. As I have said before I would leave the rear settings well alone unless they are miles out from factory settings.

 

[FunkyMunky]

The rear is not heavily laden, so the only object of rear camber is to compensate for roll rather than sidewall distortion. If anything I would tend to run less camber so as to encourage the back end to move out more readily - not that I am that brave or skilfull when driving between trees and walls. Similarly quite a lot of rear toe-in is intended to make the car user friendly. As I have said before I would leave the rear settings well alone unless they are miles out from factory settings.

sounds quite user friendly for female drivers then too :wink:

thanks for the response George - knew you'd know!!

 

[George K]

Gareth - is that to presuade female drivers that the Trophy is a good idea or that you are safe in it (driving of course)? Have to be careful about lcomments on ady drivers - one of the most competitve at Wiscombe is a genuinely charming lady in an Elan.

BTW it is a whole separate topic, but I eventually understood the merits of the Honda Prelude's rear steering system - which did seem to work very well - probably too expensive, but then for a short time they fitted an active diff to the JDM Prelude. In summary the AWS was the equivalent of increasing rear toe-in in high speed corners