chittybangbang
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| posted on 3/6/07 at 04:56 PM |
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Wide front track/suspension/steering?
I have a mk3 cortina and would like to use this as the donor for the running gear for my locost (I will still be using escort engine/gearbox).
As the rear axle is some 2" wider each side, I would like the front track to be the same (yes I know I could get away with it as countless
people have told me - but I would like the tracks to be the same).
If I were to just build custom wishbones which would push the swivel joints out a further 2", would there be any problems?
The two issues I can see are that the steering rack would be too short (assuming I use the escort rack) - is there an alternative rack that would fit
straight in that would perform as well as the escort rack (such as the cortina rack or a sierra rack) or alternatively could the escort rack be
extended by 4" without any loss in steering performance - which companies offer this service? (I had intended to fit a quick rack at this
point).
Finally, there are the front coilovers, is it simply a case of buying units which have an additional extended lengths (I wouls like the mounting
points on the chassis to remain in the same position.
Any help is welcome.
Cheers.
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britishtrident
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| posted on 3/6/07 at 05:21 PM |
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Not a case of getting away with the rear being wider than the front --- it just dosen't matter, I can list you lots of production cars with
really big difference in front and rear track both ways. Until aerodynamics became more important than suspension all F1 cars had much wider rear
tracks. In a corner unless a car is in an oversteer condition the front of the car always follows a wider radius than the front ---
The only application that benefits from having the same track is serious off road work in deep mud, sand or snow.
Most recent Locosts that aren't IRS use Cortina axles and the ones that are IRS use Sierra rear end parts which are the same width as the
Cortina.
You really want longer wishbones use an Escort rack with threaded extension to gain the 2" each side.
Although its is 4" wider don't be tempted to use the Cortina rack -- it is too wide and will give colossal bump steer, the Escort rack is
already too wide between the inner ball joints for the book chassis.
2nd hand Escort mk2 racks are getting hard to find -- you can get a narrowed Sierra rack or make a Mk2 Escort rack out of parts from a MK1 Escort rack
fitted with the track rods from your Cortina rack.
I will leave to someone else to tell you about the wider 4-4-2 chassis.
[Edited on 3/6/07 by britishtrident]
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ecosse
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| posted on 3/6/07 at 05:34 PM |
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As BT says you can (should) still use the escort rack, even if going wide track, either buy (most 7 makers will sell them off the shelf) or make a set
of track extensions to accomodate the extra width.
Most shock manufacturers will make shocks to what ever size you want (Gaz, Protech etc).
And as said you could choose to build to 442 or +4 size rather than staying with a book chassis, although it depends on whether you need/want the
extra tub width and like wide rear arches (or not), some do some don't.
Cheers
Alex
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blakep82
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| posted on 3/6/07 at 06:53 PM |
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if you're using cortina back axle, surely the cortina steering rack would be about the right width?
________________________
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don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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ecosse
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| posted on 3/6/07 at 07:13 PM |
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quote:
Originally posted by blakep82
if you're using cortina back axle, surely the cortina steering rack would be about the right width?
It would be the right width to connect up to the wheels for sure, but as the escort rack is already slightly too wide for the chassis, I would imagine
the cortina one would make for some horrific bump steer conditions 
Cheers
Alex
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higgsti
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| posted on 3/6/07 at 08:35 PM |
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my car has wide track suspension the benifit of this is a better turn in and turning circle .the rack is escort quick rack with rack extensions made
from ally by previous owner with raceleda uprights.
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907
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| posted on 3/6/07 at 09:08 PM |
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If I were to make longer wish bones then I would make them from stronger tube.
i.e. larger diameter / thicker wall, or both.
I believe that if longer shocks are used then they sit at a shallower angle so the springs need to be stiffer. (I think)
This is just my opinion so feel free to shoot me down.
Paul G
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MikeRJ
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| posted on 3/6/07 at 10:17 PM |
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quote:
Originally posted by blakep82
if you're using cortina back axle, surely the cortina steering rack would be about the right width?
The extra width in the Cortina rack is in the rack itself, rather than longer track rods. Longer wishbones do not require a longer rack to
compensate, simply longer track rods. A longer rack will introduce very bad bump steer.
Another problem with the Cortina rack is that on a book chassis the input shaft falls outside of the chassis, and even on a +4" rack the input
shaft is almost exactly inline with the FU chassis member.
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chittybangbang
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| posted on 7/6/07 at 09:58 PM |
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Thank you very much indeed for your replies, I have just read "build your own sports car on a budget" by chris gibbs and it is a very
impressive book indeed. In that the "Haynes Roadster" as it is called, uses a sierra back axle and a wide chassis. The car also uses an
escort rack with extensions screwed onto the steering rack - it gives CAD drawings of how to make them and also mentions that they are available from
MK engineering. Right, so on that bombshell, jobs a good un it'll work - front and rear track will match.
Three final questions though...
1) would the shallower angle of the coilovers created by the longer wishbones (remember that the coilovers would have to be longer and lean in more)
hamper the handling of the car at all.
2) I have been talking to a friend who has a spare LSD from a capri 2.8 special - could this fit into the cortina axle casing that I have?
3) The Gibbs book and one of those who replied, mention that the escort rack is a little too wide for the chassis and that it can be shortened by an
engineering company - do we know what would be the ideal reduction/size for the rack to be absolutely perfect for a 'book' chassis, if the
rack could be shortened and still incorporate a 'Quik Rack' reduced ratio, and finally - which companies would shorten this for me?
Kind regards,
Gareth.
[Edited on 7/6/07 by chittybangbang]
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ecosse
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| posted on 8/6/07 at 06:01 PM |
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Questions
1/ I'm no expert but, what it means is that you get a falling rate, i.e the more bump movement you have the easier it is to compress the shock,
so in effect it gets weaker under bump rather than stiffer (crap explanation sorry)
2/ Doubt it, but maybe someone else knows for sure
3/ You don't strictly need to shorten the rack to get rid of bump, but it will make it easier to do, try MK, MNR (and I'm sure many
others) for this, but just to complicate things, I'm using a standard rack (as are many others) with little or no bump steer evident!
Hope that helps some
Cheers
Alex
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