Wheel offset and track width - what effect on handling?

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Evil_Fiz
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Location: Jacksonville, FL

Wheel offset and track width - what effect on handling?

Post by Evil_Fiz » Thu Jan 18, 2018 8:36 pm

What I have so far:
Per TireRack.com, factory wheels on a 1970 Karmann Ghia are 15 x 5.5/ET +17
CB performance drop spindles will push the wheels out 3/8" (10mm)
American Racing wheels: AR95T 17 x 7.5/ET +25
This wheel would put my wheel center line +2mm from the factory settings
I am not concerned with tire clearance since I will be reshaping the wheel arches to suit
I would like to run 215 or 225 40-17 tires
I have seen many recommendations to go with high + offset wheels to tuck the wheels in for clearance.

My questions:
- How does the high + offset affect bearing life? My thinking tells me that there will be less strain on the bearings due to lower leverage from an inboard wheel center line.
- How much impact will the narrowed track with imposed by +40ish - +50ish offset have on street handling? From what I have read wider track produces less leverage on the suspension when cornering. Wider is better.
- What is the prevailing opinion on American Racing wheels? The model listed above is all i have found so far that will keep the wheel center line close to the factory spec. a plus on these wheel is that I can get them drilled to suit.

Cheers, and thanks,
Emil

American Racing AR95T 17 x 7.5/ET +25
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GS guy
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Re: Wheel offset and track width - what effect on handling?

Post by GS guy » Thu Jan 18, 2018 9:52 pm

5.25" back-space (8.5" overall wheel width/2= 4.25"= 0 offset + 25mm (1") = 5.25") on that AR wheel might put it pretty close to the upper shock mount on the beam? Not sure on on a 17" diameter wheel though, I know 15's can get tight. Might have to adjust the steering stops too so it doesn't rub the sway bar/inner fender at full lock. The lower BJ gets pretty close on a 15" wheel too with the dropped spindles, with 17's it shouldn't be a problem. Easy way to check the clearance is to verify the back spacing on your existing wheels, and with one mounted take measurements off it and simulate the inner wheel & tire positions on your chassis and beam. From your specs above, that would be around 4" back spacing (stock). With the drop spindle track increase, that would mean the new wheel would only set in just under 5" from stock. Don't presume any measurements - do your own to make sure what you're working with.

Bruce2
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Joined: Sat Oct 13, 2001 3:01 am

Re: Wheel offset and track width - what effect on handling?

Post by Bruce2 » Fri Jan 19, 2018 3:38 am

Evil_Fiz wrote:
Thu Jan 18, 2018 8:36 pm
What I have so far:
Per TireRack.com, factory wheels on a 1970 Karmann Ghia are 15 x 5.5/ET +17
Stalled before you started! The Tire Rack is way wrong.
A 70 Ghia had 4x15" wheels. Not 5½, not 4½". And I think the offset was 46mm (or 41?) If Marc was aware of this topic he'd set us all straight.

How much do those 17" wheels weigh?

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Evil_Fiz
Posts: 26
Joined: Sat Aug 01, 2015 9:30 am
Location: Jacksonville, FL

Re: Wheel offset and track width - what effect on handling?

Post by Evil_Fiz » Fri Jan 19, 2018 4:33 pm

Bruce2 wrote:
Fri Jan 19, 2018 3:38 am
How much do those 17" wheels weigh?
No clue, I cant find weight information but It may not matter since it looks like the BS is not suitable for my application. I am not having any luck finding specs on the 1970 Ghia factory wheels. If anyone has a source please let me know.

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