Author Topic: Wheels?  (Read 2563 times)

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Offline Rocky

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Wheels?
« on: September 10, 2007, 02:47:46 AM »
Hello everybody,

does anybody knows is it possible to put 13x8J in the front and in the rear? I know that rear wheels can be 8J, but do they fit in the front?

I have a chance to buy these:

BWA 13x8J Made in Italy
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They are 19.1cm wide.

Thanks for help

Offline bibito

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Re: Wheels?
« Reply #1 on: September 10, 2007, 09:26:09 AM »
That would depend on the offset /ET/ of the wheels, and what kind of rear fenders you are planning to use.
I'm using 9J in the rear with 220/54 tire - no problems
Cheers,Lubo

Offline Rocky

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Re: Wheels?
« Reply #2 on: September 10, 2007, 11:42:49 AM »
Thanks Bibito. But my question is for the front wheels. Will they fit in the front? By the way, I think that the offset is 28mm but will have to check.

p.s. Bibito could you post some pics of your car? I would realy like to see those 9J in the back. What do you drive in the front?

Offline bibito

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Re: Wheels?
« Reply #3 on: September 10, 2007, 06:26:21 PM »
The 8J I'm using infront have offset 22, they might not clear the front brakes as I will be using zastava calipers which hold thicker pads/will use a small spacer/, also lowering the front with more tha 5cm.,might also be a problem. I will post pics. when the car is out of the workshop, as for the moment I don't have the tires on.
Cheers,Lubo

Offline Rocky

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Re: Wheels?
« Reply #4 on: September 10, 2007, 09:19:36 PM »
The 8J I'm using infront have offset 22, they might not clear the front brakes as I will be using zastava calipers which hold thicker pads/will use a small spacer/, also lowering the front with more tha 5cm.,might also be a problem. I will post pics. when the car is out of the workshop, as for the moment I don't have the tires on.
Cheers,Lubo

Thanks mate. Looking forward to see your pics. If you need some parts of Zastava, I am from Serbia and I could supply you with those parts.

Offline Pantdino

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Re: Wheels?
« Reply #5 on: September 12, 2007, 05:16:23 AM »
Rocky,

What kind of front wheel cutouts do you have?  The TCR cars had such big cutouts I'm sure very wide wheels would fit there. 
If you know what the offset is and what kind of tires you would have on them, you could make an "imaginary" wheel and tire to see if it would fit.

Jim

Offline Rocky

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Re: Wheels?
« Reply #6 on: September 12, 2007, 11:22:52 AM »
@Pantdino Thanks on advice. I will be having custom made cutouts for wheels like on Abarth 1000tcr and I am thinking of tyre 175/50 R13 to use. I think that will work.

New question: Is tyre R13 175/50 the best to fit on this size of wheel?

Offline Pantdino

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Re: Wheels?
« Reply #7 on: September 13, 2007, 05:57:36 AM »
according to tirerack.com a 175/50-13 tire should go on a 5-6" rim.
My 1995 BMW M3 runs 235/40-17 tires on 7.5" rims from the factory.
I have 185/60-13 tires on 5" rims in front and 6" (152mm) rims in back on my 850TC replica and the back ones look about right, while the front tire sidewalls look a bit bulged, like the wheel is a bit narrow. 

Are you sure the wheels are 19.1cm wide?  8 x 25.4= 203mm by my calculation.
A rule of thumb I read is that for racing cars the tire should be about the same width as the wheel, but it seems on most production cars the tires are wider.

I have seen photos of Abarths where the tire seemed to be stretched quite a lot to fit on the wider wheel, so it seems to be commonly done.
You may want to find a tire in that size and pull the bead out to that width to see how it looks.

Jim

Offline Paul vander Heyden

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Re: Wheels?
« Reply #8 on: October 07, 2007, 12:41:16 AM »
Hi Rocky,

I guess the first question I would have is why you would want to put 8" wide rims on the front of a 1000TC?  Even the factory did not bother with that.

I see two problems.  First there is a clearance problem with almost any such wide wheel, both with respect to tire diameter but also fouling the inner fender on full-lock.  Second, perhaps more importantly, a wheel with that kind of offset will really upset the scrub radius of the steering and overload the outer wheel bearing.

A standard wheel is offset such that the center of the wheel is roughly midway between the location of the two bearings on the axle.  This maintains an acceptable scrub radius taking into account Ackerman characteristics and also distributes the load between the two bearings.  If you move the center of the wheel outboard, in relation to the center between the two bearing on the axle, you are altering the scrub radius and putting additional stresses on the outer wheel bearing.  A discussion of scrub radius effects is probably too detailed to get into here, but the bearing load issue is easier to understand.  There are many good publications on Ackerman and steering design.

Bigger wheels mean bigger tires.  If these are "modern" tires then they are likely to have more grip and adhesion as well.  After all we are all hot-rodders at heart.  Of the two bearings, the outer one is the smaller of the two.  Now we are going to load it up with a bigger wheel, hung outboard, and with a much stickier tire. OUCH !!  Remember that the Fiat 600 was designed around bias-ply tires, mounted on a 4.5 inch wide wheel, not high performance radial tires on an 8" wheel.

Of course we want our cars to "look good and aggressive", and there is nothing wrong with that.  But it should be done in a engineering sensitive way.  If you are going to use wider wheels, try and maintain equal amount of offset to the inside and outside.  There is a reason why the TCR had such large wheel openings!!

From a competition perspective anything more than a 7" wide wheel in the front is probably counter productive.  Even then, you better have a lot of horsepower to move that wide tire down the road.  The same goes for the rear.  I have found that a good combination, even for a car with over 100 HP, is 7" in the rear and 6" in the front.  This is a good compromise between  adhesion and frontal footprint.

Hope this helps.

Regards,

Paul Vanderheijden
Scuderia Topolino