Wheel Vibration

[G]

For the last few weeks I have had quite a bad vibration through the front wheels, first thoughts were I had lost a wheel weight or from reading various posts it seemed A048's are susceptible to vibrations after various heat cycles and track use.

 

The vibration gets more violent at speed, it was really quite bad at rockingham on smooth tarmac over 100 mph.

 

Anyway I have been playing around with a home made geo rig made up from wire and poles, I set the rig up around the car and after measuring up discovered toe in was fine on the back wheels but the front O/S wheel had 4mm toe out and front N/S 0.5mm toe out. I adjusted the O/S wheel back to match, took it for a quick spin and hey presto vibration gone.

 

Amazing how much feel you get through the steering on these cars, it feels awesome, very accurate again. I'm enjoying learning about setup and geometry and especially to try a few changes on track.

[mambosasa]

So, I have been thinking about this. I understand that the string method works very well and is being used by several MLOC members, however surely it's feasible to develop a laser based alignment rig? One that is pretty simple to hookup on the car and use?

 

Here is my thinking.

 

1. It cant be difficult to construct something that would hook onto the wheels with a measuring strip.

2. Use a laser pointer mounted on a wheel rig for the alignment. Pointers can be bought for sub 30 quid.

 

For those who know more how the DIY rigs work, I am sure that there could be a way of putting together something that is simple and cheap.

 

Thoughts?

 

Bis.

[mambosasa]

Perhaps with this rig for the reading and the laser pointer for the 'string"??

 

http://www.pegasusautoracing.com/productdetails.asp?RecID=4714

[Phil S1]

Hi G,

Glad you're enjoying learning about set up. Do you know what caused the alignment to be that far out? Have you hit a pothole or anything?

 

Bis,

I must admit, using lasers has crossed my mind before but I've never really pursued it. Measuring from strings always seems too time consuming to me because it deflects too easily, so I eventually changed my rig to use ally box section. It's still takes me ages though and I could imagine a laser set up would save alot more time but one thought would be, what's the tolerance on a 'cheap' laser?

I need to have a bit of a think about it.

[TheRon]

Other tools that could help are the 'Corbo' geo tool: http://bobvanm.brinkster.net/corbo.htm but it's not cheap.

 

I use a 'Gunson Trakrite' (which I'm sure used to be cheap but seems to be really expensive now !) which only gives you an overall toe-in or toe-out measurement but is very quick and easy to use, no set up, just hold steering wheel straight and drive over it.

 

I find it useful when replacing bits e.g. a toe link rod end on just one side - just measure overall toe before, change the part, measure after, adjust & measure until you get the same overall measurement as before you started.

[HABC]

For the last few weeks I have had quite a bad vibration through the front wheels, first thoughts were I had lost a wheel weight or from reading various posts it seemed A048's are susceptible to vibrations after various heat cycles and track use.

 

The vibration gets more violent at speed, it was really quite bad at rockingham on smooth tarmac over 100 mph.

 

Anyway I have been playing around with a home made geo rig made up from wire and poles, I set the rig up around the car and after measuring up discovered toe in was fine on the back wheels but the front O/S wheel had 4mm toe out and front N/S 0.5mm toe out. I adjusted the O/S wheel back to match, took it for a quick spin and hey presto vibration gone.

 

Amazing how much feel you get through the steering on these cars, it feels awesome, very accurate again. I'm enjoying learning about setup and geometry and especially to try a few changes on track.

 

It will get better soon, its just the post Xmas & new year DT's................................................

[jonamacg83]

The box method (whether string or otherwise) is perfectly adequate to get good results. You can use fishing line which allows you to get the 'string' very tight and rigid, though I think a full alloy box would be better.

 

Setting up the box can be time consuming the first time, but the trick is to be able to mount the end bars on the car consistently each time, whether it be by bolting them to the car or some kind of clamp arrangement, it makes it much much quicker. Though obviously you have to make some kind of modification to the car to allow that (mounting holes etc) but it is possible to do using the number plate mounting holes...

 

I can't see how using a laser would work as you would have to have a target (or a smoke machine) as you wouldn't be able to see the beams?

 

We have one of these:

 

http://cgi.ebay.co.uk/SEALEY-Laser-Wheel-Alignment-Gauge-GA50-/140432961995?pt=LH_DefaultDomain_3&hash=item20b274f1cb#ht_1734wt_905

 

However the fundamental problem is if one side is out and the other isn't, its difficult to get it right. You can drive forward to make sure you are aligned straight both sides, but then your steering wheel isn't correct. Its great for small adjustments at the track when everything is spot on and true but difficult to use otherwise.

 

Jonny

 

[Phil S1]

I guess it could be done something like this, apologies in advance if it ends up sounding like a load of gibberish :-

 

Start with ally box sections, secured by whatever means, across the front and rear of the car.

Initially run strings between the 2 ally box sections to create the normal 'box method' arrangement and centre the box by equalising the measurements to the wheel centres. (as normal so far).

A vertical datum line could be scribed on the ends of each box section in line with the string.

Make something along the lines of the 'Dream Stick' tool that Bis refers to but ideally also make it self supporting on the wheel.

The laser would be mounted horizontally on this as near to the wheel centre as practical. This would shine forwards (or backwards) to hit the ally box section, or a larger target attached to it.

You could measure from the string to the centre of the laser body at the wheel centre and then duplicate this dimension on the ally box section by measuring in from the previously scribed datum line. This line would represent where the beam should hit on nominal (for zero toe).

This could be repeated in a similar fashion at all four corners.

The tricky bit would then be marking further graduations on the box section to measure the amount of toe in or out. The laser is not on the true axis of rotation (the axis defined by the upper and lower balljoints) so an amount of trigonometry is going to be required in order to correlate what a say 1mm difference at the wheel rim would be as an offset from the nominal scribed line on the box section.

Another way round this might be if the 2 upper legs of the Dream Stick were adjustable for length such that the amount of toe could be preset on the stick and then the laser would always be aiming for the nominal scribe line.

Other problems are you'd probably want at least a pair of the sticks with lasers on and then there's the additional complication that the rear wheels are a larger diameter than the fronts so the legs of the tool might also need to adjustable for diameter as well as depth. Otherwise you could do with a tool specific for each corner which is getting a bit ott.

 

Let us know when you've made one Bis