View Full Version : Eccentric topmounts set for most caster
Anyone know how much caster is achievable using eccentric topmounts from the likes of Compbrake?
I currently have them set "in and back" but pondering modding the turret to gain as much caster as possible, then setting up the camber using camber bolts.
Just wondering how much will be gained by butchering the turrets before I do anything!
i think you should be studying olly's (trackdaynova?) thread for the bit about making new bottom arms to move the hub forward to get the same result
Was reading his earlier actually, in relation to running the topmounts upside down (which I'm not keen on doing) and filing out the turret top for more adjustment (in his case camber but same applies for me). Like this but backwards and not inwards:
http://i136.photobucket.com/albums/q161/neocapture/nc1132.jpg
I've been pondering ways of modifying the tie bar to make caster adjustable but I'm a bit out of my depth here tbh.
Aftermarket setups seem to use rosejoints on the lower arm which don't look too kind for country road bashing, which my car racks up most of its miles doing. Unless it'd be possible to slot the holes in the lower arm and reweld washers to get the hub further forward on standard stuff?
Coul you shorten your tie bars?
making the tie rods adjustable would be relatively easy, you could even make a turnbuckle (hollow bar & lh & rh threads) on the main bar.
you could simply place a strong piece of steel with 4 holes in between the ball joint & tie bar to move the hub forwards, in a bolt in way.
how much extra castor are you trying to get?
Aiming for the build manual's 4 degrees, I'm going to buy one of those camber/caster gauges discussed in the other thread to measure how much I have currently but it's not far off standard I don't think.
garyc I have thought about having some machined off the tiebar where it slots through the front bracket, could always shim it if too much was taken off?
All just pondering at the moment lol
novarally
30-12-11, 08:38 PM
Aiming for the build manual's 4 degrees, I'm going to buy one of those camber/caster gauges discussed in the other thread to measure how much I have currently but it's not far off standard I don't think.
garyc I have thought about having some machined off the tiebar where it slots through the front bracket, could always shim it if too much was taken off?
All just pondering at the moment lol
We did just this on my Mk.1 Fiesta rally car (about 25 years ago now), machined the shoulder of the tie bar back so we could pull the wheel forwards.
Cool, sounds like it could be an option cheers Colin.
Wonder how much someone would want to make a full on threaded setup like this:
http://img.photobucket.com/albums/v321/bennh/Crap/23.jpg
aren't they chopped down track rods welded in there?
Looks like the turnbuckle setup you were talking about? Male RH/LH threaded bar and female parts on the tiebar for on-car adjustment?
Iirc Dewis on Vauxsport and Mig made the tie bar shorter by increasing the threaded part by 15mm to pull the wheel forward
On a Nova? Dewismotorsport?
Edit, found it. On a Corsa coupled with adjusted top mounts:
http://www.migweb.co.uk/forums/projects-restorations/416510-dewismotorsports-c20let-corsa-gsi-9.html
Looks like the turnbuckle setup you were talking about? Male RH/LH threaded bar and female parts on the tiebar for on-car adjustment?
yes, but it also looks very similar to mk3 astra track rods..
http://img499.imageshack.us/img499/7831/driverssarm4fv.jpg
Iirc its on his white Corsa
MARTIN KELSON
31-12-11, 12:22 AM
James (Jonlem) on here does rose jointed adjustable track rods & tie bars.
The adjustable top mounts as they sit inside the front turret your restricted in the amount of adjustment you can actually get.
I did see recently a rally nova Colin had for sale / breaking with the top mount located on top of the turret.
This is something I have thought about & presume there is a reason why more don't do this.
I would have thought if you strengthen the turret then there is no main reason why you can't do this.
Any thoughts on this appreciated??
Martin
My honest opinion on eccentric top mounts is that they're waste of time.
I would go for adjustable tie bar and bottom arm setup
MARTIN KELSON
31-12-11, 11:13 AM
http://i285.photobucket.com/albums/ll66/hillclimbescort/0132.jpg
Just found the picture from Colins for sale thread.
Top mounts like this i was on about.
May get more adjustability going down this route.
Martin
What is to stop you running them upside down? Serious question.
Martin I guess running them like that is putting the weight on two M8 bolts rather than the whole strut top area.
Mark nothing is technically stopping you from doing that, that's what Trackdaynova did, I personally don't fancy the weight of the car being sat on a circlip in a machined bit of alloy though?
I thought if I chopped the turret "lip" out it'd give me more backwards adjustment, however this thread has made me look into tiebar mods before doing that so my turrets may survive for now lol
MARTIN KELSON
31-12-11, 02:25 PM
Weight of car wont sit on circlip as that is under the bearing.
Agree on weight of car on the threads in the top mounts, but that can easily be sorted by either drilling & tapping larger bolts or drilling right though & having a nut welded inside the turret to screw into.
Ford boys run them on top so must be possible.
I personally don't fancy the weight of the car being sat on a circlip in a machined bit of alloy though?
Best not check out your piston rings then :p
My main worry with simply pulling the hub forward is this is impossible if everything is fully constrained as it should be, so you're putting a huge pretension on the polybushes and restricting movement. Adjustable tiebars/turnbuckles work fine but do have the disadvantage of concentrating the stress around the bolt, doubtful it will actually snap as it should be in tension or compression the whole time because of the way they work, but it may flex more around that area, since the 100% tension/compression is theoretical and not totally mirrored by the way it actually works. The standard bottom arms and tiebars aren't the best setup imaginable so you can kill 2 birds with one stone looking in that area.
chambers1984
31-12-11, 02:35 PM
use corsa bottom sure there 10mm wider. that should give you near 4deg your after and then adjust the topmount to get bang on.
use corsa bottom sure there 10mm wider. that should give you near 4deg your after and then adjust the topmount to get bang on.
He's after caster, not camber, which is changed by moving the hub at 90 degrees to the track width/where you're thinking, i.e along the wheelbase, or back and forward, not out and in.
chambers1984
31-12-11, 02:48 PM
sorry my fault did not read it right.
Best not check out your piston rings then :p
My main worry with simply pulling the hub forward is this is impossible if everything is fully constrained as it should be, so you're putting a huge pretension on the polybushes and restricting movement. Adjustable tiebars/turnbuckles work fine but do have the disadvantage of concentrating the stress around the bolt, doubtful it will actually snap as it should be in tension or compression the whole time because of the way they work, but it may flex more around that area, since the 100% tension/compression is theoretical and not totally mirrored by the way it actually works. The standard bottom arms and tiebars aren't the best setup imaginable so you can kill 2 birds with one stone looking in that area.
considering the amount of miles worth of abuse the std setup takes... every pothole & bump is trying to pull the bottom arm & tie bar off the car, i think time has also proven this method of increasing caster to work fine.
considering the amount of miles worth of abuse the std setup takes... every pothole & bump is trying to pull the bottom arm & tie bar off the car, i think time has also proven this method of increasing caster to work fine.
I assume you're referencing the pulling the hub forwards? It's not really a matter of taking abuse or actually working, no doubt it will, but the last thing I'd want to do while trying to improve performance is restrict the movement of suspension components.
personally, i'd say the best way is to fabricate new arms & tie bars, but its an awful lot of work....and i think trying to get an extra couple of degrees caster on the struts isn't going to restrict the rest of it too much.
IIRC my lower arms don't actually look straight in their current position, I think my lowered tiebar brackets (thus straightening it) will have actually given it some negative caster? So bringing it forward slightly may actually straighten the bush.
Fabricated arms and tiebars do look like the ideal solution, but will it be too unkind on a road-going car?
Weight of car wont sit on circlip as that is under the bearing..
Weight on circlip was in response to the suggestion of running them upside down.
My struts actually protrude so far through the topmounts I've had to cut away the inner bonnet skin, mounting them on top would probably make them go through the top layer too lol
nova ian
31-12-11, 05:03 PM
I remember when I helped Olly fit & setup his Rose jointed setup. The setup he had before the fully rosejointed one was adjustable in a fashion and he decided to get rid as using a standard bottom arm and bush didn't really allow any movement due to the nature of how it mounts, so any caster gained by shortening the tie bar just put major stress on the mounting point and caused it to eat bushes like Xmas chocolates!! It deffo needs a spherical bearing on the bottom arm in my opinion other wise it's pointless. This can still be done modding the standard arms, and I know alot on the stockrod and Grassing guys have the thread lengthen on the tie bars to gain more caster as you will see at the autosport show ;)
Hope that makes sense dude
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