ned
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| posted on 28/8/03 at 11:39 AM |
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IRS & Wishbones - Track width dilema
I am now building a book based chassis, though am considering making it IRS. I have book wishbones and trailing arms, but am in a bit of a quandry.
(yes I know a beam axle would be the simplest!)
Can I buy MK Indy wishbones and fit them at the front of a book chassis to make the front upto the width of the standard sierra rear end? (Do the Indy
wishbones share/fit the suspension brackets as per the book?)
Or should I keep the book wishbones up front and get the sierra driveshafts shortened as Luego do on the Velocity?
Are there advantages to handling of having the wider sierra track?
(I presume Sierra standard width rear and book front would cause a very badly handling car!)
Any replies, experience, info, suggestions appreciated.
Ned.
beware, I've got yellow skin
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craig1410
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| posted on 28/8/03 at 12:04 PM |
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One thing to consider:
I think if you use MK front wishbones then you will have to use Sierra front uprights so if you were planning to use Cortina uprights then this may
swing it in favour of book wishbones.
Of course you could make longer "book" wishbones to increase track but may then have trouble getting springs and shockers off the shelf to
fit.
The option I took was to use a wider chassis along the lines of the McSorely 7+4 which is 4 inches wider than book and gives me a 56" track
(front) with book wishbones and I have a 57.8" track at the back with the unmodified sierra shafts and diff. I am running de-dion but this
shouldn't matter in terms of track widths.
Check my website for any further details or just ask.
Cheers,
Craig.
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ned
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| posted on 28/8/03 at 02:04 PM |
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Craig,
The +4 width chassis isn't something i'd thought of, though I already have a fully tacked and part properly welded chassis!
Are there difficulties or additional expense in getting +4" bodywork?
I tihnk I'd prefer to leave the chassis as is and go down either the mk wishbones or luego shafts approach.
Anyone know how much Luego charge to shorten the driveshafts?
Ned.
beware, I've got yellow skin
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JoelP
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| posted on 28/8/03 at 03:37 PM |
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I'm doing a standard width chassis with longer front wishbones (made today!), sure enough it looks like i'll have to stretch the
shockers....
i'm sure it'll all be OK! The actual cockpit is 50 inch outside to outside so at least theres plenty of room, but the wheels have half an
inch inside the side rails. neither here nor there i guess. i think it would have looked better with the wheels further out....
not sure about body work but can always worry about that later.
didnt realise MK bones were different sizes to the book, obvious when you think.
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Simon
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| posted on 28/8/03 at 03:43 PM |
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Ned,
GTS Tuning (dozracing) are developing +4 nosecones/scuttles, and hopefully bonnets.
He must be on holiday coz I've not had a reply to my email re progress.
I was going to make, but think cost and time wise, it'll save a packet by buying!
ATB
Simon
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pbura
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| posted on 28/8/03 at 04:12 PM |
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Ned,
A good thing about the wider track would be that the car would corner flatter. With the narrower track, you get more nimbleness. 6 of one, a half
dozen of the other 
Negatives of the wide wheelbase with the standard chassis are (possibly) poor coilover angles and lots of empty space in your rear fenders.
The easiest thing would be to get a Cortina axle. Besides that, if I were you, I would have the axle shafts shortened. Luego's Locost price
list says GBP45, quite a bargain if they do this for walk-ins.
BoL,
Pete
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blueshift
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| posted on 28/8/03 at 04:15 PM |
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Simon, you figured it was cheaper to buy ready-made bodywork than do your own fibreglassing?
I haven't looked into the prices yet but that is surprising..
Not sure what we're going to do yet about fitting the v8 under the bonnet.. different carbs, custom grp bonnet, alu bonnet with stuck-on bump
(ew) or what.
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craig1410
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| posted on 28/8/03 at 04:31 PM |
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Blueshift,
I think Simon (rightly) will be placing a price on his time in which case it is MUCH cheaper to buy than make fibreglass parts and the quality is
likely to be MUCH better too. Making moulds is only sensible if you intend to make more than one (more than 5 IMHO) or if you want to stick rigidly to
the DIY ethos. I think that even the raw materials alone (matting, resin, wood, fixings, brushes, rollers etc etc) will cost almost as much as the
finished product from most of the suppliers.
Anyway, I intend to buy my stuff from GTS as well once it becomes available. As for the bonnet bulge, I hope to modify the bonnet to incorporate a
removable bonnet bulge panel which can be changed to suit different sizes of bulge as I can't justify the expense of a Weber 500 setup just yet
and will have to stick with SU's to begin with.
Cheers,
Craig.
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Northy
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| posted on 28/8/03 at 05:48 PM |
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The Tiger Avon has a wider rear track compared to the front. 
Graham
Website under construction. Help greatfully received as I don't really know what I'm doing!
"If a man says something in the woods and there are no women there, is he still wrong?"
Built 2L 8 Valve Vx Powered Avon
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Rob Lane
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| posted on 28/8/03 at 08:08 PM |
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My car is standard book chassis, standard Escort axle etc.
It has terrific turn in and excellent front grip but it is very easy to oversteer. (All 7's are anyway)
One or two guys i competed against had similar front track as myself but wider rear track and they always could hold the track better before
oversteer.
With a book chassis and the standard rear wings available, the rear axle is 50mm in from both outer sides of wings unless you use a Cortina or Crapi
axle.
Fitting one of the above axles with book wishbones means you have odd track anyway.
I've never actually measured a Sierra rear track but suspect it's close to a Cortina, Crapi one anyway.
Shortened driveshafts. Not sure what Luego do to them but ST cuts the driveshafts and fits sleeves which are then welded all round.
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stephen_gusterson
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| posted on 28/8/03 at 09:44 PM |
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quote:
Originally posted by blueshift
Simon, you figured it was cheaper to buy ready-made bodywork than do your own fibreglassing?
I haven't looked into the prices yet but that is surprising..
Not sure what we're going to do yet about fitting the v8 under the bonnet.. different carbs, custom grp bonnet, alu bonnet with stuck-on bump
(ew) or what.
take a look on the fibrelassing section of my website. It explains the hassle.
Unless the fibreglass is massively expensive, you would be nuts to make your own 'glass parts.
Getting an A1 surface, if you want self coloured parts, will be near impossible for a beginner on a first attempt.
atb
steve
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craig1410
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| posted on 28/8/03 at 10:08 PM |
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Rob,
The Sierra track (rear) is 57.8" which is what I have set mine to with full length driveshafts. You can adjust it a little bit when building
your IRS or De-dion setup but I thought it was best to stick with the original track width to ensure that my Lobro joints were correctly biased. My
front track is 56" so hopefully I will benefit from the extra stability and resistance to oversteer that you mentioned. Of course I want some
oversteer 
Cheers,
Craig.
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ned
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| posted on 29/8/03 at 09:02 AM |
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I have been offered a cortina axle for a reasonable sum, but think i'd rather do the extra work to get an IRS setup.
I also have some small offseted (ex-caterham) alloys which I think will pertrude from book rear arches and i don't fancy wide rear arches. As I
have a set of front wishbones and suspension bits and the fact that luego only appear to charge £45 I think i'll go with the shortened
driveshafts approach.
Though as always I may have changed my mind by the time it come down to it!
Ned.
beware, I've got yellow skin
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James
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| posted on 29/8/03 at 12:46 PM |
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quote:
Originally posted by ned
I have been offered a cortina axle for a reasonable sum, but think i'd rather do the extra work to get an IRS setup.
I also have some small offseted (ex-caterham) alloys which I think will pertrude from book rear arches and i don't fancy wide rear arches. As I
have a set of front wishbones and suspension bits and the fact that luego only appear to charge £45 I think i'll go with the shortened
driveshafts approach.
Though as always I may have changed my mind by the time it come down to it!
Ned.
Will they (Luego) give you dimensions on their rear wishbones tho? Or can you buy their rear wishbones alone? Having been through this myself
I'd recommend buying them if your definately going IRS.
To be honest though if I was you I'd use the Cortina axle (although make sure you get one with the ratios you want- ask Jasper!). If a live axle
is good enough for The IsonBlade and Hicost then it's good enough for you!
There's loads of hassle in changing to IRS once you've got a built chassis: suspension mounts need to change, wishbones need mounting
somehow, you need to make uprights, diff mounts... it goes on and on!
James
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ned
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| posted on 29/8/03 at 01:59 PM |
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James,
I've spoken to Jasper about his axle, it would be suitable gearing wise as with a type 9 and my engine would have a theoretical geared top speed
of 137mph.
Having checked MK's and Luego's site's it appears you can buy the IRS wishbones for around £200-300, luego do a Conversion Kit (4
rear Wishbones, 2 Hub Carriers, Diff Carrier) for £313!
Food for thought...
Ned.
beware, I've got yellow skin
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James
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| posted on 29/8/03 at 02:59 PM |
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quote:
Originally posted by ned
James,
I've spoken to Jasper about his axle, it would be suitable gearing wise as with a type 9 and my engine would have a theoretical geared top speed
of 137mph.
Having checked MK's and Luego's site's it appears you can buy the IRS wishbones for around £200-300, luego do a Conversion Kit (4
rear Wishbones, 2 Hub Carriers, Diff Carrier) for £313!
Food for thought...
Ned.
Are you saying that's cheap or expensive?
Anyway, my point is, is IRS really so great that it's worth the bother? Especially when you've already got an LA chassis?
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ned
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| posted on 29/8/03 at 03:32 PM |
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I don't know if IRS will be worth the bother, but it's in my opinion the way the job should be done properly. It also makes it easier to
change dif ratios and drop in an LSD at a later date.
Easier to service/interchange other components if ever necessary too.
Is £313 + vat (£370) a reasonable amount for 4x rear irs wishbones, uprights and dif cage? I can't see the material costs are anywhere near as
much if i was to do it myself, its just the labour and design aspects i guess.
Ned.
beware, I've got yellow skin
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craig1410
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| posted on 29/8/03 at 07:12 PM |
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Ned,
Are you aware of the de-dion kit which GTS Racing are planning to release. It gives you many of the advantages of IRS with the simplicity of live axle
and can be made to any width.
In particular it uses the Sierra diff for ease of ratio/LSD options and requires hardly any modifications to the "book" chassis. It should
also give better straight line traction than either IRS or Live axle and will cope better on bumps than Live.
Cornering wheel geometry should be as good as Live axle (ie. perpendicular to the road) but with lower unsprung weight which should be better.
Speak to Stu16V about his own "practical" experience of de-dion as I can only talk theoretically at present. If Cateringvan use de-dion
and Dax use it then it can't be bad IMHO. Check my website if you want to see some detail but remember that I built my own de-dion kit which
hopefully GTS will supply in a ready to drop in state.
One other thing to point out is that most people agree that Live axle is the lightest option so if weight is a big issue for you (BEC for example)
then live axle is probably best. Be aware that the Cortina axle is 4" wider than escort whilst the Capri is about 2.5" wider than the
escort.
HTH,
Craig.
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pbura
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| posted on 30/8/03 at 02:58 AM |
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I haven't seen a Cortina since about 1967, so I think of it as a smaller car, didn't know it was almost as big a beastie as the Sierra.
Would an Escort axle be possible? They look very nice and light.
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craig1410
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| posted on 30/8/03 at 08:57 AM |
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Yes, I think it was originally quite small but later models (the ones that I know from childhood) are much bigger and chunkier. I saw a
"W" reg one yesterday in fact.
Cheers,
Craig.
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blueshift
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| posted on 30/8/03 at 12:40 PM |
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We have a mk IV sitting on our drive waiting to be killed; trust me, they're big.
Thanks for the responses about grp, we'll reconsider the best way to cross that bridge a bit later, I think.
[Edited on 30/8/03 by blueshift]
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carcentric
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 posted on 30/8/03 at 04:08 PM |
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Thinking it through
One of the early posts in this thread suggested widening the chassis and using standard suspension from there outward to increase front track.
Wouldn't doing that require:
- longer tie rods (hubs farther from steering rack),
- longer swaybar/antirollbar (greater hub-to-hub distance, and
- longer or relocated brake lines (greater hub to frame distance.)?
I can't think of any other non-bodywork items that would have to be changed as a result of widening the frame - have I missed some?
The longer tie rods wouldn't change the steering geometry, would it? Maybe some at full lock?
M D "Doc" Nugent
http://www.carcentric.com
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craig1410
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| posted on 30/8/03 at 04:45 PM |
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Carcentric,
I think you mean track rods not tie-rods but yes they would have to be lengthened. More commonly it seems, people just use the Sierra rack and shorten
it to suit. This is what MK do for the Indy so it's not a problem really.
An anti-roll bar would need to be lengthened but I'm not aware of many people using anti-roll bars on Locost's unless they are planning to
race them. You might be able to use a standard bar and use some form of bespoke linkage to suit the extra width. It is only 2 inches either side after
all.
Brake lines should not present any problems. Yes you will need a little bit more on the solid pipes but these are made to suit normally anyway. The
flexible hoses will have exactly the same distance to the chassis as they would with a standard width chassis if you think about it.
The way I think about this extra width stuff is: Does the component traverse the centreline of the car? If it does then it will possibly be affected.
If it doesn't (such as a front cycle wing or flexible brake hose) then it will work fine as with the standard chassis.
HTH,
Craig.
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jcduroc
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| posted on 30/8/03 at 08:22 PM |
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quote:
Originally posted by craig1410
... and I have a 57.8" track at the back with the unmodified sierra shafts and diff.
Craig
Do you measure track from tyre CL contact ptach to the other?
Is it drum or disc brakes?
In either case which is the distance between mounting flanges?
Cheers
Joćo Matoso
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jcduroc
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| posted on 30/8/03 at 08:29 PM |
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quote:
Originally posted by ned
Are there advantages to handling of having the wider sierra track?
(I presume Sierra standard width rear and book front would cause a very badly handling car!)
Any replies, experience, info, suggestions appreciated.
Ned.
Hi Ned
Wigth transfer in turns in inversily proportional to the track.
This does not not mean that you'll have automatically less body roll but that, with the same springs, you'll have less body roll!... (Do I
make myself clear?)
Briefly, within reasonable limits, the wider the track the better.
Cheers
Joćo Matoso
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