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The mkiv Supra Owners Club

Ideal wheel size for track


binfieldx

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What are the Ideal wheel sizes for track? I'm thinking about going with something like an 18". I've got 19s currently and they definitely feel too big, too much roll around corners.

 

The thing is with my supra, it's got wide arches so I can fit much wider wheels than normal. I can't really find anything in an 18" thats bigger than 10.5j. I thought I might be able to run a comp like 18x9.5j fronts and 18x11j rears? Is there any need to run any bigger than 10.5 for track or is it better just sticking some spacers on to fill the gap.

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What do you mean by too much roll round the corners ?

 

What suspension do you have ?

 

I had 9.5 x 19 front and 11.5 x 19 rear and it was great on the track,

 

Suspension was Bilsteins with Eibach pro sport springs and TRD anti roll bars, it had also had all new

suspension arms fitted with a proper geometry set up done at Centre gravity

Edited by Dnk (see edit history)
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I've got Tein super streets I believe. Not sure if its my current tyres or 19" wheels but I heard 18" was the ideal size?

 

If i go around corners fast it feels, I'm not sure I suppose. Unstable? Not sure if that's just me being a panzy or what but it feels like it's gonna slide alot if I do it too quickly.

 

Was watching this aswell which was quite interesting - https://www.youtube.com/watch?v=o6Glkf4jwkM

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I've got front and rear Cusco strut bars but that's it. The wheels are on nangkangs at the moment which I know aren't amazing..

 

I'd try putting some premiem tyres on rather than budgets, its amazing what a difference they make, however a set of good tyres will set you back a fair bit so if you are undecided if you should go smaller diameter i'd make up my mind about that before spending the cash

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Semi slick track tyres need a LOT of camber to work properly, and a lot of camber on the road will cause terribly uneven tyre wear and tramlining. The hardest set ups are where someone wants a raod car that works well on track too. A pure track car, or a pure road car are dead simple, compromises are, well, compromises, and you need to decide where your priorities lie. My GTS-t is a brilliant track car, and a real joy, with even tyre wear and sublime handling. On the road it's a total dog and would wear the insides of the tyres out in less than 5000 miles, assuming you haven't shaken your fillings out first. Plus all the rod ends and spherical bearings need maintenance, some of them are £150 plus a pop.

 

There's no point in buying lightweight, correct fitment forged rims and mounting Nankang or other ditch finders on them. Tyres are your only contact with terra firma, so even the best set up car will be useless on cheap rubber. If you want the best semi slicks nothing comes close to Michelin Pilot Sport Cups (CUPS being the operative word). But they are expensive...

 

 

As a colleague of mine proclaims on a sign in his office, beneath which a black gallery of broken rods, collapsed pistons and bent valves sit. "Speed costs, how fast can *YOU* afford to go" :)

 

I like MKIV's on 16 inch rims if it's a wet track, 17 inch if it's dry. Many will disagree, but they are not good on very low profile tyres and dire on 19 inch rims, due to the need for ultra low profile rubber. The suspension design is relatively crude compared to modern multi link suspension designed from the get go for low profile rubber, which in itself is something of a fashion statement on road cars.

 

Tyres, rims, good dampers and a proper LSD are the starting point for good track work. Geo is totally different for track and road, although a fair compromise can be achieved. If you are using it more on the road than the track relatively soft progressive rate springs are needed. most "kit suspension" is on far too stiff a spring rate. Once you start using spring rates and damper stiffness to keep incorrect tyre size and wheel offsets off the arches you are into kidding yourself territory and the car is already a dog through desperately poor choices of aftermarket parts.

 

 

The *FIRST* thing a race car designer will want to know is what rim and tyre size / type will it run on. the car is then designed around them.

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Very interesting post Chris, thanks for that. My arches were widened and big 19s slapped on the car with rubbish tyres and a Tein suspension. I can only assume with that they were going for a show can only kind of thing. On the roads it's really really rough and bumpy so I guess I should be looking at my suspension and tyres with the current wheels that are on.

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I would strongly advise you do not take the car on a track if the wheels have spacers fitted, unless hub centric, using properly heat treated rolled thread suds, and of VERY VERY moderate thickness. The loadings they impose are vast. The correct way to fill boxed arches is by moving the inner wishbone pivots outboard, and having rims with offsets that minimise hub bearing loadings. I have seen some very nasty failures when the loading from riding kerbs and general track loads are imposed on spacered wheels.

 

I remember a rear stub axle failure on my race Elan, at Lodge at Oulton, which didn't end at all well. Caught for posterity by a guy in the crowd.

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My only problem with 18s is I can't find any reasonably priced wheels they go more than 10J. I was looking at Rota but the 18s only go up to 10J and I got wide arches so I dont want to run them with spacers. My current 19s are 10.5 and still has a small amount of gap from the arch

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