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The mkiv Supra Owners Club

Wheel size for best handling top secret wide kit


lucasl
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Ive been considering getting the top secret wide body so that i can fit wider wheels to the car, with this extra width what would be the best wheel size for performance, the car is going to be used primarly on the track.

 

I read an article on the top secret car it said the wheel size was 18" 9.5 front and 10.5 rear using 12mm wheel spacers, it didnt mention the offsets though.

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Ok yes thats true, but the older gt supra's were fairly similar to the road going version, Im talking suspension wise as they still used double a arms with top strut suspension, the new ones use inboard push rod if i remember right.

 

Im at least looking for 18" wheels so i can fit a decent size brake behind it.

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Without a complete redesign of the suspension (which the race cars had, in abundance) you will build a car that handles like a dog and eats hub bearings. It may even be dangerous. Wide body kits are for car shows and parking up outside the wine bar, unless you keep stock (ish) width and offset rims under them, which will obviously look very odd indeed. Even a GTR Skyline, compared to a GTS-t, has a totally different rear subframe, driveshafts, hub bearings and geo, and the rear track increase is very small... Don't buy a wide body kit is my advice, if you want a car to use in anger.

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ok my knowledge of suspension set up and re design is very limited, i dont want to argue i just wanna learn.

So doesnt having a wider track give better handling due to less weight force on the wheels/tyres, cant this be acheved by having wider wheels and or spacers and the suspension set up correctly. Wouldnt having the front wheels at zero offset reduce the scrub radius, therefore even keeping standard size wheels with zero offset would make the need for wider fenders?

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So doesnt having a wider track give better handling due to less weight force on the wheels/tyres, cant this be acheved by having wider wheels and or spacers and the suspension set up correctly.

 

The suspension geometry was designed to work with the standard size/offset wheels, increasing the diameter, width and reducing offset of the wheels will compromise the handling badly.

 

Spacers are also not a good idea, have a read of these articles.

 

http://planetsoarer.com/offset/studs.htm

http://planetsoarer.com/offset/offset.htm

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Yes true modifying susension and changing wheels will change and compromise things, ie. changing to stiffer springs and thicker antiroll bars will give you better camber control in a turn by reducing the roll angle, thus hopefully being able to keep the tyre at zero camber on its greatest contact patch making it corner faster, doing this though will compromise ride comfort. This is true with almost all modifications.

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Im not planning on running stock suspension at all, i just think that getting some wider wheels with different to stock offsets will improve traction and cornering ability with correctly set up suspension.

 

Maybe his question would be best answered by telling him how much said after market racing suspension setup is going to cost him.

 

Ohlins suspension setup £3500 to £4000 installing spherical bearing mounts of good quality i guess £500 to £1000. Adjustable control arms all round not sure £1000, antiroll bars would probably make them up to required stiffness.

 

Or depending on what youre suggesting, fabricating a complete new suspension setup with custom made control arms, relocating mounts etc, id go for pushrod suspension, and all the other stuff thats needed that im not entirely sure about.

 

Asking a friend who builds racecars to help me set it up priceless.

 

why how much would you say it costs smartass.

 

 

lol just kidding

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The problem is you need a bizarre wheel offset as the stock suspension wasn't designed to handle a very wide wheel rim, nearly all the offset has to go outboard, and the hub bearings won't like it one bit, quite apart from the fact the kinematics of the stock suspension are totally wrong for such a wheel and tyre width. It just won't work properly, and to make it work will cost a fortune.

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I understand that the hub bearings have a shorter lifespan with the deep dish big offset wheels but doesnt keeping the offset around the 0 mark mean that they are not affected as much. therefore putting a wheel on the rear thats is say 10.5 that would be actually be 11.5 across the flanges, so zero offset would be 5.75 so i would have 5.75 inches to cover from the hub to the side of the car. (does anyone know off hand the measurement from the hub to the side of the car)

 

With adjustable coilovers and adjustable control arms could it not be set up to work well, what would you say would need to be done to the suspension to get a good result.

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I understand that the hub bearings have a shorter lifespan with the deep dish big offset wheels but doesnt keeping the offset around the 0 mark mean that they are not affected as much.

 

I don't get what you mean by 0 offset. The stock offset is 50.

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Guest steve77964

ihave the topsecret gt300 widebody kit on my car...

i have the workmeister s1 wheels

18's with 10j front and 11j rear... i don't have spacers either!

handling is alright...not as good as when i had my standard rx-7...

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I understand that the hub bearings have a shorter lifespan with the deep dish big offset wheels but doesnt keeping the offset around the 0 mark mean that they are not affected as much. therefore putting a wheel on the rear thats is say 10.5 that would be actually be 11.5 across the flanges, so zero offset would be 5.75 so i would have 5.75 inches to cover from the hub to the side of the car. (does anyone know off hand the measurement from the hub to the side of the car)

 

You can't move the inner rim lip more than a few mm inboard, the suspension is in the way, you have to put the majority of extra rim width OUT board, which ruins the kinematicas and overloads the hub bearins severely.

 

 

With adjustable coilovers and adjustable control arms could it not be set up to work well, what would you say would need to be done to the suspension to get a good result.

 

No it couldn't, you would need to redesign the whole suspension and its pick up points. Cost wise buying a Ferrari 360 would make more sense ;)

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The suspension geometry was designed to work with the standard size/offset wheels, increasing the diameter, width and reducing offset of the wheels will compromise the handling badly.

 

Spacers are also not a good idea, have a read of these articles.

 

http://planetsoarer.com/offset/studs.htm

http://planetsoarer.com/offset/offset.htm

 

WOW! I never realised that simple fact about studs. I always assumed they just held the wheel, I never thought about what supported the weight. I'm going to check for spigot rings tonight.

 

I wonder what proportion of us are chancing it without?

 

What wheels do come with spigot rings though? I've never even heard of them before.

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There is +50 mm offset on standard supra rear wheels

9 width wheels are 10in flange to flange

which is 254mm

wheel centre will be 127mm

 

so 127mm with the 50mm offset will be

177mm meaning the distance from the hub to the rear wheel lip will be 6.96 inches.

 

so putting an 11.5inch rim on the rear would clear the suspension if it has 5.75in hub to inner wheel edge.

 

But i understand that the suspension geometry is not designed for wheels like that and from what i can tell its not possible to get a good setup on the standard supra suspension geometry with wider wheels. ok so i give up :( [sAD][/sAD]

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