David Jenkins
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| posted on 11/7/03 at 07:47 AM |
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Wheel offsets (again)
I'm coming up to the time when I will buy a set of wheels, but one point keeps nagging (no, not the wife!)
My rear axle is out of an Escort, and designed for wheels with a 19mm offset.
My front uprights are off a Cortina, designed for an offset of around 38mm.
At present I have an old set of Capri Ghia alloys with something like 38mm offset, with spacers on the rear axle. I would prefer not to have the
spacers.
So should I buy 4 wheels with 19mm offset, knowing that the fronts will be wrong? Or should I buy 38mm offset, knowing that the back will have to have
spacers? Or should I buy 2 of 19mm and 2 of 38mm?
Help! 
David
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timf
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| posted on 11/7/03 at 08:02 AM |
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2 X 19
2 X 38
sounds the best idea to me
BTW have you had it running yet dave
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David Jenkins
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| posted on 11/7/03 at 09:09 AM |
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quote:
Originally posted by timf
2 X 19
2 X 38
sounds the best idea to me
BTW have you had it running yet dave
That's what I thought - trouble is, finding wheels available with both offsets (mind you, I think Minilites do both)
As for running - this weekend I'll be spinning it over to see if I can get oil pressure (without leaks!).
After that, it's working out how to plug a small hole in the plastic side piece of my radiator (don't ask!), then finding and fitting an
overflow/syphon tank.
Then - I try to start the engine! Scary, as I'm the one who put it together after the rebore. 
cheers,
David
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andyd
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| posted on 11/7/03 at 11:15 AM |
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David are you sure that Cortina offset is 38? The info I found was that Cortina was also ET19 same as Escort.
Stuart and I have certainly had ours made with that offset for both front and rear (Cortina rear axle as well as uprights). We got ours direct from
Compomotive for a total of £465.89 inc vat + delivery. That's for their MO model with 2x 7" x 15" for the rear and 2x 6" x
15" for the front. With Compomotive you can specify the PCD and offset you require as they are mostly custom made. They do take a will to
arrive but we are very happy with them. The rears certainly look the business and will pretty much fill the arches completely.
Andy
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David Jenkins
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| posted on 11/7/03 at 11:47 AM |
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quote:
Originally posted by andyd
David are you sure that Cortina offset is 38? The info I found was that Cortina was also ET19 same as Escort.
Not 100% sure - I'm in the office!
I know that I currently have Crapi wheels that require 20mm spacers to get the tyre clear of the swinging arms.
I'll have to double-check when I get home... 
David
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andyd
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| posted on 11/7/03 at 01:13 PM |
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I'll upload a picture of one of our rears for you to look at and let you know the distance between the inside edge of the tyre and the trailing
arms.
As we are using a Cortina axle we obviously have a bit more room than you do with an Escort one. Any idea how less less sticks out for the Escort one
'cause you should be able to work out how much offset you can get away with based on my measurement.
Andy
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Mark Allanson
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| posted on 11/7/03 at 05:57 PM |
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The offset for escorts and cortina's (and capri's for that matter) should be ET19. Changing this will affect the handling at the front and
strain the wheel bearings at the rear. It's not just a question of how the wheels fill the rear arches.
Take a look at Rorty's site for a good explanation
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andyd
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| posted on 12/7/03 at 10:12 AM |
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That's what I said diddle I?
That's certainly what I ordered from Compomotive in any case. They fit, they look good, they keep the chassis off the floor.
Andy
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David Jenkins
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| posted on 12/7/03 at 01:13 PM |
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quote:
Originally posted by Mark Allanson
The offset for escorts and cortina's (and capri's for that matter) should be ET19.
I had a look at my Crapi Ghia alloy wheels - they are marked ET28.5! These are bog-standard.
I do understand the importance of getting the correct offset - but it's irrelevant if I can't fit the wheel on the hub. I reckon
I'd need an offset of ET10 - 12 to clear everything (28.5 - 17mm spacer thickness)
rgds,
David
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Mark Allanson
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| posted on 12/7/03 at 05:53 PM |
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I just put my new wishbones on today, the line drawn between the upper and lower balljoints hits the floor inside the inner edge of the wheel. This
gives a scrub radius of about 75mm which seems a tad excessive to say the least. I have read that 25mm is optimal. I think we may all be a bit too
worried about the scrub radius thing if I am correct. I know that people have completed cars and used sierra wheel and the car has driven OK.
I am so keen to get everything exactly right on this build, but I may be taking everything as gospel when perhaps it ain't
Any comments, clarification?
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Rorty
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| posted on 13/7/03 at 04:34 AM |
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If you're going for anything like 75mm scrub radius on the front (asuming the tyres/rims will clear everything), you'll need to fit power
steering too!
It won't matter so much on the rear, asuming, again, there is sufficient clearance. You'll probably chew the bearings out rather rapidly
though.
What ever came as standard on your front/rear hubs, is what you should be fitting now. Simple as that, no scrub worries, and no bearing worries.
Sure some people fit all sorts, and don't know the difference, but they're the type that convince themselves it's all fantastic,
just because they made the modification, and to them it looks good.
And while they're at it, they should run their EFI motor on DERV....well it is still fuel, and it will fit in the tank!
[Edited on 13/7/03 by Rorty]
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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Spyderman
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| posted on 13/7/03 at 10:40 AM |
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Erm not quite Rorty!
If you go for a larger overall rolling radius then you will need to change the offset to compensate. Otherwise you could end up with either zero
offset or a larger offset, neither of which is really desirable!
Either way you need to know where the kingpin inclination intersects the ground, then get your wheels to suit.
You would probably be best trying to keep original scrub radius, but slight changes should not make too much diference as your car is a lot lighter.
Terry
Spyderman
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Mark Allanson
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| posted on 13/7/03 at 02:16 PM |
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Rorty, this is what I mean, everything is standard, ET19 wheels as per the Cortina, standard hub carrier, book(ish) wishbones.
If you draw the line through the balljoints, its going to hit the tarmac inside the wheel! It must have been how the Cortina was set up, but they only
had 1.5 degrees of castor probably to compensate for the (potentially) heavy steering.
Can anyone do a double check on their car just to make sure its not just me
 
Rescued attachment ScrubAngles.jpg
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Stu16v
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| posted on 13/7/03 at 08:48 PM |
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Mark, looking at the picture, the wheel has a lot of positive camber, which is making it look far worse.
HTH Stu.
Dont just build it.....make it!
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Mark Allanson
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| posted on 13/7/03 at 08:58 PM |
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Yes, I've noticed that too, look at the thickness of the balljoint lock nut - I am going to have to cut them in half or get ford ones.
Still the scrub radius looks extreem, don't you think?
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stephen_gusterson
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| posted on 13/7/03 at 10:07 PM |
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quote:
Originally posted by Mark Allanson
Yes, I've noticed that too, look at the thickness of the balljoint lock nut - I am going to have to cut them in half or get ford ones.
Still the scrub radius looks extreem, don't you think?
Mark
look at thread
Mistakes in Book
in chassis section
craigs setup looks same as yours.....
atb
steve
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Rorty
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| posted on 14/7/03 at 03:36 AM |
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Spyderman:
quote:
Erm not quite Rorty! If you go for a larger overall rolling radius then you will need to change the offset to compensate. Otherwise you could end up
with either zero offset or a larger offset...
I realise that, I should have suggested keeping all items/dimensions standard.
Obviously, if you are going for taller tyres/rims, then you should still strive for original scrub radius, for the reasons outlined before.
Mark Allanson:
quote:
Rorty, this is what I mean, everything is standard, ET19 wheels as per the Cortina, standard hub carrier, book(ish) wishbones.
Still the scrub radius looks extreem, don't you think?
Jeez! It looks huge! Well, I would be inclined to reduce the scrub from "standard" in that situation. It'll make your
steering a bit lighter too.
quote:
the balljoint lock nut - I am going to have to cut them in half or get ford ones.
Ask at your favourite local fastener supplier for "plain steel locknuts" or sometimes they're called "jam nuts". Either
way, they're about half the thickness of standard nuts.
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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jcduroc
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| posted on 14/7/03 at 11:35 AM |
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quote:
Originally posted by Stu16v
Mark, looking at the picture, the wheel has a lot of positive camber, which is making it look far worse.
HTH Stu.
...But in changing the camber angle the balljoints move along with the upright, hub, etc...
Just a thought
Joćo
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Stu16v
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| posted on 15/7/03 at 08:48 PM |
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quote:
...But in changing the camber angle the balljoints move along with the upright, hub, etc...
You are correct, but the centre of the tyre basically remains in the same place, so when the camber is altered, the top ball joint moves towards the
car, the bottom ball joint and the tyre contact patch remains (pretty much) constant. If a new line were then drawn through the ball joints to the
ground I am fairly confident that the scrub radius would be drastically reduced.
HTH Stu.
Dont just build it.....make it!
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Spyderman
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| posted on 15/7/03 at 11:11 PM |
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quote:
Originally posted by Stu16v
You are correct, but the centre of the tyre basically remains in the same place, so when the camber is altered, the top ball joint moves towards the
car, the bottom ball joint and the tyre contact patch remains (pretty much) constant. If a new line were then drawn through the ball joints to the
ground I am fairly confident that the scrub radius would be drastically reduced.
HTH Stu.
Not quite!
You would need to put in a lot of negative camber in order to move the scrub radius a decent amount. Then you loose grip on the heavily cambered tyre
and wear them out rapidly.
Bit of a catch 22!
Imagine what the camber would be like on the outside tyre when turning! There would be even less tread on the road and you would induce understeer.
Just a thought!
Terry
Spyderman
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Stu16v
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| posted on 16/7/03 at 05:12 PM |
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quote:
You would need to put in a lot of negative camber in order to move the scrub radius a decent amount. Then you loose grip on the heavily cambered tyre
and wear them out rapidly.
True, but getting rid of approx five deg. of positive camber is a lot in my book......
Looking at the picture, the top and bottom ball joint are virtually 'in line' with each other. So there is a lot to gain IMHO....
[Edited on 16/7/03 by Stu16v]
Dont just build it.....make it!
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