Wheel alignment settings

[Smithy77]

Hi all!

 

I'm having my first set of tyres fitted to the Seven this weekend (13R Toyo R888 @ £73.47/tyre from Mike Stokes Motorsport - highly recommended!!), and while I'm at it I thought I would get the wheel alignment checked/adjusted.

 

Being new to Caterhams, and knowing that it's hard to find two identical spec cars, I wasn't sure if there was a defined set of setting for all Caterhams, or if people ran different settings depending on car spec and/or intended use? I'd be after the setting for front and rear.

 

For what it's worth my car is a 2004 S3 1.6 K ex-acedemey now running at approx. 155bhp, 6x13 superlight wheels with 185/60R13 R888s all round (Yoko A048s coming off). The previous owner had it flat floored about 2 years ago, but he was probably 2-3 stone heavier than me. I use it predominantly on the road but will do 1-3 track days a year.

 

Thanks for listening

[Dr Slotter]

If it was flatfloored for someone significantly larger than you, I would consider doing it again for you. I'm sure someone can suggest someone appropriate near you.

 

Some of the racers with experience of cars similar to yours will be along shortly with some more details, but in general for a bit of track work I think 15-30 seconds of toe-out (vs. more neutral or a touch of toe-in for road) and 10-15mm of rake is the typical starting point.

 

 

[Smithy77]

Thanks Doc!

 

Does it make any difference whether you get wheel alignment or flat flooring done first? Or is it best to have it all done by one guy at the same time? I'm guessing if you have to do one before they other you would want to have it flat floored first as the ride height effects wheel alignment...

 

When you say 'rake', do you mean caster angle? You also mention 10-15mm - I thought all wheel alignment is measured in degrees??

 

Edited by - Smiffy7 on 27 Aug 2014 15:13:54

[Jonathan Kay]

Difference in ride height between front and back. You also need to decide what clearance you want under the sump.

 

Jonathan

[Smithy77]

of course..... RAKE!!! One of those moments you ask something which you later you realise you already knew!! My mind was solely thinking wheel alignment which is my excuse - what a numpty! Millimetres of course make sense here...

 

Jonathan, I could decide on ride height but I've no prior experience to know where to start or what's suitable for my requirements. I've done some reading of the archives but it appears settings vary. I was hoping for some suggestions on overall set-up on wheel alignment and ride heights to suit my needs.

[Jonathan Kay]

Quoting Smiffy7: 

of course..... RAKE!!! One of those moments you ask something which you later you realise you already knew!!

Progress!

 

;-)

 

Jonathan

[Richard Price]

Quoting Smiffy7: 

Does it make any difference whether you get wheel alignment or flat flooring done first?

 

There is little point in having the tracking set, and then having the car "flat floored".

 

Quite what is entailed in "flat flooring" a car depends on whether you're working to a price or a quality...

'not sure how often rear tacking or camber is checked, but I've often found cars with bent dedion tubes or miss matched dedion ears...

Sorting out a misaligned rear is much trickier than sorting out the front, but no less crucial.

At the front, ride height, camber and toe are closely related, and adjustment of one frequently affects another...

 

Unless you're going somewhere that know what they are doing, then they are unlikely to be able to look at much other than toe.

 

If just adjusting front toe, I'd aim for parallel toe.

[Grubbster]

Pop it over to Tom New and have a chat about how you want to use the car and let him set it up for you. Tom will advise best but roughly it sounds like you'd want 15 mm rake, 1 to 1.5 degree negative camber on the front and parallel toe (after ride height setting and corner weighting).

 

 

Edited by - Grubbster on 27 Aug 2014 18:13:04

[7 wonders of the world]

If your doing alignment properly you ought to be checking / setting the rear first then the front, after all other areas have been set all of which need to be check / adjusted with the car ballasted to the desired weight.

[chris956]

... and be sat in it or the equivalent weight at least whilst its done. I was surprised how much it all changed whilst on the corner weights with me in and then out of it. Then of course it all goes up the pictures when you take a passenger

[oldbutnotslow]

As you are probably aware you can really only set the rear toe if you have either watts linkage or adjustable radius arms. It can be done in other ways but its a heck of a lot of farting about.

I agree with Grubster

15 mm rake, 1.5 degree negative camber on the front and parallel toe (after ride height setting and corner weighting.

Around 145 mm height under the front chassis where the engine mounts are bolted on the N/S is reasonable for a road car.

 

The castor angle is the angle to which the steering pivot axis is tilted forward or rearward from vertical, as viewed from the side. Like the front forks on a bike.

 

If the pivot axis is tilted backward (that is, the top pivot is positioned farther rearward than the bottom pivot), then the caster is positive; if it's tilted forward, then the caster is negative.

 

Adjustment is somewhat crude on a 7 in that it is achieved by moving spacing washers to the lower wishbone mounting points

 

I run 0 - 4 on the rear mount which is maximum amount of castor that you can get but then again mine is a track car.

 

A standard set up would be 2-2 on the rear wishbone. If you change the castor you will need to have the track checked so do the messing first. I prefer a parallel setting although some will say a touch of toe out.

 

Toe out tends to make the car feel more wandery on the road but can help with turn in on some corners. More castor will help increase straight line stability at the expense of heavier steering.

 

If you get the toe set parallel as a starting point you can always try a bit of toe out and see how you like it. Noting the starting position will always allow you to recover the neutral position should it feel awful.

 

Sorry Smiffy I have never been a fan of 888's I much prefer 48's but that's just my personal preference! 😳

😬 😬 😬

 

 

[7 wonders of the world]

 

Neither a watts linkage or adjustable trailing arms will permit the adjustment of rear toe as the toe is set by the DD ears (tapered shims effectively) which also set the rear camber.

 

However these can be used to align the rear DD to a datum point perpendicular to the axis of the car.

 

 

[6speedmanual]

Quoting 7 wonders of the world: 

 

Neither a watts linkage or adjustable trailing arms will permit the adjustment of rear toe as the toe is set by the DD ears (tapered shims effectively) which also set the rear camber.

 

However these can be used to align the rear DD to a datum point perpendicular to the axis of the car.

 

 

Correct. Some alignment systems will quote thrust angle. This can be corrected with rear axle alignment.

 

Peter

[Smithy77]

Thanks for all the comments and suggestions! I have all I need to get it all set up correctly now.

 

@Grubbster - As it so happens, the car is with Tom New as I type having my first service on the car; thought I'd get him to do the first one for piece of mind. I shall have a word with him for sure. Do you know if he is able to do the full set up with flat flooring and corner weighting? As I mentioned in the OP the car is also booked into Mike Stokes Motorsport in Bournemouth on Saturday for tyres - has anyone had any experience with them? I'm not sure what equipment or experience they have with this sort of stuff, but as a motorsport orientated company est. over 30 years I would presume they would be able to do it too. I'll have a chat with both on the subject.

 

Regarding corner weighting, my understanding is that the four wheels are on separate scales and you play around with ballast weight/position until you have as close to 50/50 weight distribution as possible? Sounds fairly labour intensive..... does anyone consider corner weighting to be slightly overkill for a car that might see a track twice a year?

 

@oldbutnotslow - I decided to try the 888's firstly on account of price, and also the fact that I think they are a bit lighter and apparently do not suffer from tram-lining as much as A048s. I did A LOT of research on tyres and didn't find much negative towards the 888s, so I thought I'd give them a try.

 

Having thought some more about this, I may have to do some jobs over the winter that will affect wheel alignment etc, such as potentially removing the rear suspension to replace the propshaft oil seal on the gearbox. I'm therefore thinking maybe it's best to leave flat flooring and complete wheel alignment until spring. I can then just get the tracking checked with the new tyres in the mean time. Make sense?

 

Cheers all!

 

[Grubbster]

Glad you already found Tom, yes he can do the full setup for you (he can also rebuild engines or even complete 7's!). A lot of us locally use him, but he can get very busy so book in advance.

[Z3MCJez]

Full corner weighting is probably not necessary on a road car (and nobody carries ballast in a road car anyway - it's done through changing ride heights on the corners). However, getting it approximately right will make a big difference. Of course, if you sometimes carry a passenger, and sometimes don't, you'll have to compromise one of them completely (or both of them to some extent).

 

Anyway, properly done, full alignment check of all 4 wheels, following by shimming the rear to align the wheels and then a reset of camber, caster and toe could take 4 hours. But I suspect that you'd get close enough in a road car in an hour. So it should probably cost about £50-£60 in labour.

 

Jez