Confusion over Harrison wheel offsets

[sambo]

As if wheel offsets weren't enough of a mystery, I relate to you the following... I've ordered a Harrison chassis/body kit with R32 Skyline IRS. That's Nissan/Ford rear stud pattern and Commodore/GMH front, no problems there.

The following numbers relate to the maximum distance from the bolt up face to the outside of the rim, or frontside offset as I have read elsewhere. Assume 17" wheels, 8" front and 9.5" rears...

Warwick Harrison informs me that I need 95/135mm front/rear.

Doug Pearce, who has worked on several Harrisons down here, says 75/100mm front/rear.

Pasquale Piccioli, maker of Millaz wheels and who has supplied several sets of custom sets for Harrison kits, says 80/135mm.

So from 3 knowledgeable people we have a variance on the front of 20mm and 35mm on the rear. These are not small numbers!!

Can anyone with Harrison experience shed some light on this for me please? Millaz seems like the safest option, since he allows you to pre-fit the wheels prior to final welding. However, his price is around $3500 (unpainted), whereas I'm seeing them advertised in the States for $1500 USD. It would have to be at least $1000 less to import them, even after adding freight and GST. Of course there's the risk of getting the wrong offset.

Thanks in advance,
Paul

[Tenrocca]

Hey Paul - I cant say for sure on the Harrison - but different manufacturers may state front space differently - ie. CR states 2.5" front space front and back, but that is to tyre bead - that would account for 0.5" of difference at least.

I measured and test fitted temp and borrowed wheels many times, and bugged just about everyone who had their wheels already, and a lot who didnt, before deciding on an offset I was confident would fit and sit out as far as possible. Ended up going 0.5" larger front space front and back then recommended. So you may find whatever the recommendation may be, there may be room to move one way or another.

One thing I did - after setting the camber "around about right", jacked the car up, took the shock\spring off and lowered and rased the car to check chearance over full suspension travel, and lock to lock on the front.

I have ordered an american racing wheel, I didnt end up going a hallibrand - another style. They make a hallibrand in the offsets you should need, and the price should be similar - worked out at $1750 US including spinners and nuts\valve stems and shipping.

http://www.americanracing.com/wheels...lloy&section=V

Cheers

[sambo]

Yeah I've spoken to OzWheels who distribute the American Racing Cobra series wheels and they said they can't get close to the offsets for the Harrison, even if they reversed the rim.

Thanks, I'll be sure to test clearances with the springs/shocks off - nice tip!

[400TT]

Well that's weird. Doug Pearce should know and so should Warwick.

When Warwick gave you those front space measurement, he would have had to give you the rim sizes as well. As all that changes obviously as the rim size is changed.

Also keep in mind that when talking backspace or front space, that rims are actually measured from inside to outside tyre bead. So if you measure them from inside edge to outside edge they are 1" wider. So if Warwick spec'd for 8" front & 9.5" rear, he would have used 9" front rim measurement & 10.5" rear rim measurement. You need to add 1" to you wheel width measurements if using backspace or front space. Does that make sense.

[Tenrocca]

Originally Posted by sambo

Yeah I've spoken to OzWheels who distribute the American Racing Cobra series wheels and they said they can't get close to the offsets for the Harrison, even if they reversed the rim.

yeah Sorry - They might get close on the back, but no where near it on the front Im afraid (I knew there was a reason I changed style )

Cheers.

[sambo]

Sorry, but what's tyre bead?

[Beejay]

Nice price Andrew!

Now I am interested. What size did you order? I wonder how much extra the polished rims are??

Ben

Originally Posted by Tenrocca

Hey Paul - I cant say for sure on the Harrison - but different manufacturers may state front space differently - ie. CR states 2.5" front space front and back, but that is to tyre bead - that would account for 0.5" of difference at least.

I measured and test fitted temp and borrowed wheels many times, and bugged just about everyone who had their wheels already, and a lot who didnt, before deciding on an offset I was confident would fit and sit out as far as possible. Ended up going 0.5" larger front space front and back then recommended. So you may find whatever the recommendation may be, there may be room to move one way or another.

One thing I did - after setting the camber "around about right", jacked the car up, took the shock\spring off and lowered and rased the car to check chearance over full suspension travel, and lock to lock on the front.

I have ordered an american racing wheel, I didnt end up going a hallibrand - another style. They make a hallibrand in the offsets you should need, and the price should be similar - worked out at $1750 US including spinners and nuts\valve stems and shipping.

http://www.americanracing.com/wheels...lloy&section=V

Cheers

[NASSTY]

Sambo,
Could be a couple of reasons for the more conservative front offsets by Doug Pearce (DP).

Firstly, Rim size. From what I've seen, a 15" rim with 295 rubber looks fatter than an 18" rim with the same size width tyre. The tyre wall, from what I've seen bulges out more than a lower profile wheel. So the 15" tyres look/are even wider. I'm using 18" wheels and when I compare my wheels with my mates 15" the rubber looks wider even though the tyre size for width is almost the same.

Secondly, Camber. The more camber the more the tyre will tuck under the body. What camber do Harrison’s use?

Thirdly, engineering. In VIC the engineers can be tough. Could be DP wants to factor this in so that the engineer won't ask for extended wheel arches!

Fourthly, DP may want to cover himself for any variances in parts or the Harrison kit itself. I don't own a Harrison so I don't know if this may even be an issue. As the builder it could be that he doesn't want to deal with angry customers whose wheels (for whatever reason) may not fit.

So Rim size, camber, engineering and part variances could be why.

For my kit I used the manufacturers specs and I've had no problems. I'd be giving DP a call and ask him exactly why he's used a different spec. It could even boil down to the look of the wheels inside the arches....

Hope that helps. I know I spent ages searching for the right wheels and tyres and in the end I was relieved when it all worked.

Cheers
(edited for typo's)

[Tenrocca]

Originally Posted by Beejay

Nice price Andrew!

Now I am interested. What size did you order? I wonder how much extra the polished rims are??

Ben

Now I did hand my credit card details to a dodgy man in back woods of Arizona, who had to call his wife "Erma" to "git me a pen" and write down the card numbers...but Im pretty sure they will show up in the priomised 7 year delivery time

Sizes.....
17 x 8 front (5.5 BS) and 17 x 9.5 (7 BS) rear. I dont think the polished centre wheels same style would be any more - maybe even less. The BS in 18's are a little more restictive though. 18 x 8 only goes to 5.25 BS and 18 x 10 gos to 7.25 - both would put the wheel too far out I think.

you might like the "hopster" as well - but again I dont think you could get it in 18's in the BS we need.

http://www.americanracing.com/wheels....asp?section=V

Cheers.

[sambo]

As I suspected there's just too many unknowns. I'll wait until I get the car and take some of my own measurements before I order the wheels... unless someone can personally vouch for specific offsets with a certain make/model (Halibrand style) with the standard Harrison with R32 and non-flared guards.

[400TT]

Tyre bead is what you call the edges of the tyre where it sits into the rim.

So if you measure a rim on the inside, where the tyre covers, on both inside edges, an 8" wide rim will measure 8". If you measure from far outside edges of the rim(the bit you scrape on the gutter), and 8" rim will measure 9". It's these outside edges that are used for back space and front space.

Personally I would buy rims last. That's what we have always done. There are always new styles coming out and you taste & requirements may change by the time you finish your build. Plus saves you having to store them safely.

Yep, it's a good idea to verify the offsets yourself and you may like your wheels sitting in/out a little further than what someone else does. It makes it a lot easier to measure wheel offsets etc if you can borrow some wheels that are close to what you want, so see if you can bribe someone local.

[hsv300]

Sambo I should have my harrison late next month and I am looking at similar wheels. I'm looking at using the Commodore rear end (If its done in time) or the RB32 will let you know.

cheers Greg

[sambo]

Thanks Craig - tyre bead isn't something I'd ever heard of before, makes sense though.

Greg - cheers. I considered that C'dore IRS from Warwick but couldn't justify the extra thousands in order to get deeper dish and better diff choices. What are the other advantages?

[macloft]

Hi Sambo
Warwick has recently changed the geometry of his front suspension. This also could be a factor in the differences you are getting. Put your info back to Warwick and see what he says. He currently has a car in his shop being set up I am sure he could use this to demonstrate to you wheel/tyre size issues using pictures sent via email or post if need be.
Bruce

[Beejay]

I will wait until I see yours Andrew!!

It is a bugger about the backspacing on 18's, that is what I was looking at.

Ben

[WKB]

Sambo,
I have Millaz wheels and below is a copy of an email Pasquale sent to me to confirm the spacings

"Dear Warren , progress , we have set specs up for castings , the wheel
centres and spinners will go in for casting on Monday , rear set at
125mm / front set at 80mm , thank you kind regards Pasquale ."

If are going to buy your from the states be aware that the rear brake calipers exceeds bolt up face by 16mm. This can be a problem.
I was going to go 85/130, but went conserative to be sure they fitted.

If you go to http://cobrakits.com.au/ and look at "Peter's" car. I think this car has 85/130 spacings.

Warren

[NASSTY]

Originally Posted by hsv300

I'm looking at using the Commodore rear end (If its done in time) or the RB32 will let you know.

cheers Greg

Not getting too far off topic I hope, but what commodore rear end does the Harrison now use? There was nothing about them on their website, yet.

Thanks

[400TT]

Originally Posted by NASSTY

but what commodore rear end does the Harrison now use?
Thanks

Here is the info straight from the horses mouth. (Harrison is still offering Skyline Independent & Ford or Commodore Live Axle offerings.)

Fabricated Independent

This rear-end is supplied for buyers wanting a premium rear-end with the capability for deep offset wheels or deep offset pin-drive wheels.

Features:

• Reduction in both sprung & unsprung weight.
• CNC machined aluminium uprights
• Fabricated tubular A arms
• Fabricated CV joints
• Option of Commodore or Ford 9” diff centre.
• Commodore rotors & callipers.

[07cob]

Originally Posted by sambo

As I suspected there's just too many unknowns. I'll wait until I get the car and take some of my own measurements before I order the wheels... unless someone can personally vouch for specific offsets with a certain make/model (Halibrand style) with the standard Harrison with R32 and non-flared guards.

Paul

I have had wheels on order from Pasquae at Millaz for sometime and have just (last weekend) had them in Warwick's workshop for a test fitting. The figures Warwick are quoting you (135R/90F) are the distance from the bolt up face to the outermost point on the tyre. As Craig pointed out, these will not necessarily be the offsets for any given wheel size. The actual offsets will depend on these figures as well as the tyre size - in particular how much *bulge* you choose to run with. If you run 15" rims, the tyre might *bulge* (say) 30mm, while if you run 18's, it may only be 5mm. In these cases, you might order 105R/60F in the 15's or 130R/85F in the 18's, to allow for the *bulge*.

I am using 16" rims and have gone with a 10mm *bulge factor* so have 125R/80F offsets on the Millaz wheels. I do have some photos of the wheels on the car that is currently in Warwick's workshop that I will post tomorrow.

There are further issues around the camber set on the suspension. I checked all mine unsprung and reckon (after looking at other Cobras with the same wheels) that I could go another 10mm on the rears, but I really won't know this until I stick some rubber on the rims and I don't want to take the risk. If you can wait until I get some tyres (probably a month or two), I will do 354 measurements and send them off to you!!

Hope this helps

GeoF

[sambo]

Thanks for clearing that up Geof. I'm months away from purchasing wheels so it would be great to see pictures of yours first - measurements too, excellent. Did you consider Trigo wheels and do you know whether they fit?