Help! Do we need camber bolts on the front?

[oliie]

To all the guys who've had their alignment done...

Did you need camber bolts on the front wheels?

I am about to have mine dialled in with about 2.2 degrees of front camber but I am not too sure how much camber the front can adjusted utilising the stock suspension geometry. I understand that with the stock bolts a max of around 1.7 degrees can be dialled in.

Any ideas greatly appreciated as I need to order the H&R bolts in advance of getting the work done...

Cheers
O.

 

[OliS]

Aurok told me they dialled in-2.0 degrees using the std camber bolts :?

Wigstar told me he had the same experience at Northampton Motorsport when he went there recently, they also could not dial in enough camber using the std bolts.

Whilst my Trophy was at Aurok, I asked if the std camber bolts could be used to dial in -2.0 degrees and they said it all depended on how much movement they could generate, and the alignement of the suspenson when they took the car in. In the same sentance they also said that if the std bolts could not be used, then they did have some bolts left over from the Clio Cup championship that they could use.

I'll give them a call tomorrow and see what I can find out.

 

[George K]

When I did mine there was virtually no scope for adjustment with the original bolts. - other than by slotting the the hub carrier flange holes. Rather than use after market camber bolts, I had calculated that going to an aircraft spec 12mm bolt (standard is 14 mm) for the top of the two bolts should give the right amount of camber change and take enough torque to give the correct clamping load - so far so good. I did need to use a special locking nut (spiralock if I remember correctly) as normal nylocs are not up to the job, and there was not a k-nut ot suit.
'Camber bolts' should be OK, but just cost much more than raiding the stores!

 

[Steve]

George, What do you do? If you don't mind me asking. My guess is you're an engineer.

 

[oliie]

Thanks guys. I think the H&R bolts are £34. Unfortunately I don't have the technical knowledge to ensure the workshop utilise the appropriate 'off the shelf' bolts and associated locking nuts so I may go with the H&R bolts to be safe.

I will direct Andrew from Yozza here to see what he thinks (he is commissioning the good work for me in addition to the brake upgrade )

As a FYI... I am aiming for around -2.0 degrees camber on the front with around 25' toe out. Hopefully the rears are already at roughly -1.5 degrees.

Cheers
O.

 

[OliS]

Just got off the phone with the guys at Aurok, and they have informed me that you can dial in the required camber using the std camber bolts, but the top camber bolt has to have some material machined away from the shoulder of the bolt to allow the adjustment. This is apparently what they have done with my car, and the other road going 182's that they have set up.

They do the machining using a precision tool, and don't recommend that you have this work done by anyone who is not familar with this proceedure due to the potential for bolt failure if too much material is machined away. They base their measurements on the bolts supplied for the Clio Cup Championship, which if the customer prefers can either be sourced through Rsport in Wimbledon, or directly from Aurok.

 

[Cue]

George, What do you do? If you don't mind me asking. My guess is you're an engineer.

lol, aye that'd be mine n'all

 

[oliie]

Oli - thanks for checking this out =D>

I was actually booked in to Aurok on Friday but unfortunately now need to head to Yozza instead for the brakes (and then I am heading to the 'ring on Saturday so I will be out of time). Therefore will now do the alignment up north while I am there.

To play safe I may go for the H&R bolts - unless Yozza think otherwise. I will ask Andrew what he thinks

Thanks again...

O.

 

[George K]

Just to confuse you all, I actually work as an accountant, but originally qualified as a mechanical engineer and have worked in motor racing for most of my life. As a sideline I used to do some engineering on touring cars, and not being too proud too learn used to lean on my F1 designer friends for advice.

The finanical side is all very well, but needing some sanity and light relief I try to keep involved in some technical projects - the Trophy is it for now, as time is very limited. These days It is very helpful to be able to wander down to the design office and ask someone to run the numbers on, for example, different bolt options. Still need to know what questions to ask - the trick is to try to understand the basic principles; in suspension these are inevitably quite complex.

For instance it should be able to calculate the theoretical toe in/out from the scrub radius and camber - but for a fwd car there are power on and power off considerations - I have yet to meet anyone who is prepared to admit to a programme which can do this - not even the major industry simulations seem to give consistent results. Hence why there is so much debate on the best settings!

Sorry, got a bit carried away there!

 

[Steve]

Not at all, you carry on, you lucky so-and-so being involved with motorsport most of your life, must make the accountancy seem a bit mundane. Hobbies are the way forward!

What can you tell me about the Trophy's Ackerman? I realise that some cars don't have any - which is why they make an awful noise turning sharply in multi-storey car parks. It would be interesting to know how this is set-up on our car and how changes to it would affect the handling characterisitcs.

 

[George K]

Steve, thanks for you kind words. Ackermann is one of those multi-dimensional problems to which there does not seem to be any hard and fast answer. The theoretical solution, with simple line projections intersecting along the line of the back ‘axle’, applies in an ideal world without any tyre slip angles. When you factor in that these can reach as much as 5 degrees before loss of adhesion, and will be vastly different for the heavily loaded outside front wheel and the inside wheel, let alone the rear wheels of a FWD car, you can see how quickly the model breaks down.

There was a thread in which the donkey and I seemed to agree that in motor racing there seem to be fads, which have varied from conventional, to zero or even negative Ackermann – I can not remember any hard and fast conclusion – in which case one tends to revert the norm.

All I can say is that if good handling (grip and feel) means that it squeals in a car park – so be it!! I do not have any idea about the set up on the Clio, and to some extent am not worried, because on most corners the amount of lock used is relatively small and so the consequent effect of Ackermann is minimal. When going to the limit in slower/tighter corners, the inside front wheel is lightly loaded and therefore will only generate a small cornering force whatever you do.

 

[Steve]

Thanks George, I read somewhere about negative ackerman, where there is so much slip on the outside front that a narrower radius (or rather a wider on the inside) helps cornering. Bizarre!

Did you get your Trophy set-up at race car doctor? I e-mailed donkey, because they are near me in Lewes but I'm yet to receive a reply. What camber/toe have you set your car to, or is it a secret? Looking at the suspension turrets on the 1.2 Clio yesterday, I noticed the non-existent castor compared with the Trophy, why do they not use more castor on ordinary cars, surely the slight cost increase (if any) would be outweighed by the improved handling? BMW have a very aggressive castor on their front wheels, easy because there's no drive going to them, but how would even more start to upset a FWD car?

As you say, where tyres or any deformable objects are involved, the physics get very complicated, very quickly.

 

[George K]

Steve, I did a quick sketch last night and could see an argument for negative ackerman in some cases, but it does weird (nasty and illogical) things to the theoretical instantaneous centre of rotation.

I do my own set ups, having treated myself to a set of dunlop tracking gauges and a digital camber gauge - still use string for the four wheel alignment - limiting factor is the flatness of the garage floor! If the track of the car is equal front and rear it can be done without the tracking gauges and you can make your own camber gauge with a spirt level and some bits of wood! The results are surprisingly good, if a bit fiddly.

Castor on FWDis another black art, as you have trail under power-off or braking, as in a RWD car, but pull when the power is on, so it would seem that negative castor would be best. However there are other factors such as contact patch deformation and scrub radius. If I remember correctly the Trophy runs about 2.0 degrees (I checked mine and it was as per 'book') which is quite modest - this could be because it seems to have a small scrub radius; other cars run up to 4.30, and I have seen as much as 6.0 on some FWD racers; but as ever those other factors will probably explain the differences. A Clio 1.2 will not have the power to generate any significant torque steer and so can focus on different priorities.

No secrets about my settings - have not the opportunity to do enough track testing in Devon to experiment. Front is 2.00 negative and 10' toe-out (which is how mine was delivered), the back is standard (1.45' negative and 20' toe-in, which seems fine for a driver of my limited abilities - the very brave would run a tad of toe-out and less camber). Am now running soft tyres for hill-climbs and will get a bit more of an idea of wear patterns to see if any changes would make sense - if you do track days a tyre temperature gauge is the best way to check cambers.

Regards

 

[Cue]

right - about to get my suspension set-up (wheel alignment )....

taking personal preference out - what are the best settings :?: camber, etc

 

[George K]

Cue - front 2.0 negative and 0 - 0.20" toe out.
Rear seems fine as quoted for standard.

 

[Cue]

nice, thanks George.