Is this is a dumb idea?

[1JZGTE]

Probably

 

Now, I have a Soarer 1JZ-GTE, but I guess any effect wouldn't be too dissimilar on a Soop, so I'm gonna fire away...

 

Would I achieve any gains at all whatsoever, of any description, by having Supra OEM 17s on rear and Supra OEM 16s on the front?

What would having 17s on the rear and 16s on the front do to:

 

(a) handling

(b) steering

© braking

 

etc.?

 

Edited June 8, 2009 by 1JZGTE
'Cos I completely ballsed it up! (see edit history)

[j1mb0b1]

I would say it was a Dumb idea it would be very bad for handling would nock the geo out !!!

[1JZGTE]

Hmmmm....ok. I have seen a couple RWD cars that run bigger rims (as well as wider) or the rear vs. front and a lot them are street cars.

 

*scratches his head*

 

???

[JamieP]

Cant see it having a huge effect but id guess it would be better with the stock 16's.

[bigbloodyturbo]

Mr2's seem to do this quite a lot but I dont know what it would do to a supra, for starters you'd have no room for decent brakes.

[bodilx6]

Kind of a complicated quetion me thinks and you would need the geo specialists answers to get reliable answers to your three questions.

But if you really wanna do it, and mainly drive your car in a regular and orderly fashion. My best guess is that it wouldnt give you any problems as long as you make sure to get the geo set up properly afterwards.

But in any case, it wont be as good as a standard setup but my guess is that you will never notice.

[Wez]

You would normally put smaller wheels on the rear to give you more tire wall, bigger at the front to allow for larger brakes. Some Road racers in the US run 18" up front and 17" at the rear.

[heckler]

You would normally put smaller wheels on the rear to give you more tire wall, bigger at the front to allow for larger brakes. Some Road racers in the US run 18" up front and 17" at the rear.

 

and TVR's griff/chimera ran 15's on the front and 16's on the back, but then again, that TVR for you

[Alex]

Lotus tend to put smaller fronts on to rears.

 

The smaller front is for a reduction in unsprung mass and ride comfort.

[Wez]

and TVR's griff/chimera ran 15's on the front and 16's on the back, but then again, that TVR for you

 

Lotus tend to put smaller fronts on to rears.

 

Learn something new everyday

[bodilx6]

Well, lots of high prices exotics today run 18's front and 19's rear or even 19/20. Think Koenigsegg, a few ferraris (as far as I recall) and some of the more crazy italians.

[1JZGTE]

 

The smaller front is for a reduction in unsprung mass and ride comfort.

 

That's what I was thinking....wher's Chris Wilson when you need an opinion?

 

[little num]

why have you got some 17"'s to try this with lol.

[benkei]

My MR2 has 16's on the rear and 15's on the front... Can't really tell THAT much of a difference tbh.

[martini]

Lotus tend to put smaller fronts on to rears.

 

The smaller front is for a reduction in unsprung mass and ride comfort.

 

But with the VX220 same sizes were used for aesthetics I heard.

[Guigsy]

But with the VX220 same sizes were used for aesthetics I heard.

 

but thats vauxhall

[1JZGTE]

why have you got some 17"'s to try this with lol.

 

 

Lol.

 

I am wondering whether I should get a front pair of 16s to go with the rear 17s mate

 

[Chris Wilson]

This (plagiarised) info may help a bit:

 

Are big wheels with low-profile tyres just a styling fad or marketing gimmick? In some market sectors they have become that, but this is a styling fad with some basis in engineering.

 

Actually, the trend to very low tyre aspect ratios began in racing. Low-profile tyres are still used in racing, where they are allowed: Trans-Am cars, touring saloons

and other production-based road racing cars, autocross cars, sports racing cars. Tall sidewalls are only seen where the rules limit wheel diameter, and on the driven wheels in drag racing.

 

 

 

Thirty-five years ago, there were no street tyres below a 60% aspect ratio. If you wanted the low-profile look that the racing cars had, you had to buy racing tyres. People sometimes ran racing tyres on the street, although of course that was illegal. But that was the only way to get racy-looking tyres with stiff sidewalls and sticky tread rubber. Car shows were full of display-only vehicles with race tyres. The reason we now see low profiles on the street, and tall profiles in F1, is that street tyre technology has belatedly caught up with discoveries originally made in racing, while racing rules have restricted F1 cars, and some other classes as well, to anachronistic wheel sizes.

 

Is this a bad thing? Not necessarily, although it is a bit odd. If you are running a racing series, it makes economic sense to restrict any technological progress that would require competitors to replace equipment or require manufacturers to retool. If you are trying to keep speeds down and keep fields full, why would you permit anything that raises both speeds and costs? As long as the cars go fast enough and make enough noise to put on a good show, that's enough, isn't it?

 

Certainly it is if you are openly promoting budget racing, with technologically restricted cars. But if you are billing your series as the premier class in motorsports; if you are charging an arm and a leg for tickets; if everybody knows the expense to compete is ridiculous but this is part of the draw – then it becomes harder to defend Draconian restrictions on tyres and wheels. And if you are still trying to justify the show as an exercise in "improving the breed", that really does get rather awkward. Wide, low-profile tyres are the main street-applicable technological advancement that racing can claim to have originated during the last forty years.

 

Are they really an advancement? The questioner appears to have some doubt.

 

I say yes, they are an advancement, although they are something of a mixed blessing and have become a customizing fad.

 

Making the sidewall shorter and the wheel diameter bigger has two, or perhaps three, advantages. First, it makes the sidewall stiffer. Second, it makes room for bigger brakes. And, if we don't use all the extra room for bigger brakes, we can get more air through the wheel. If we shape the mudguards properly, that lets us extract more air from under the car through the wheel wells. This not only helps brake cooling, but also aids lift reduction/downforce creation. This assumes, of course, that the car has mudguards.

 

Are stiffer sidewalls always better? I think we can say that for racing and for high performance applications, we want as much lateral stiffness as we can get. There is some penalty in directional stability, because the car will have more tendency to "tramline", or follow edges in the road surface that nearly parallel the vehicle's direction of travel. But a performance-oriented driver will generally put up with this to get more responsiveness and greater cornering power. Greater lateral stiffness helps keep the tread flat to the road and prevent the tyre from rolling under and concentrating load on the outside shoulder of the tread.

 

 

 

Greater vertical stiffness is more of a mixed blessing, and a more complex issue. The tyre is to some extent a secondary suspension system, acting in series with the main suspension system. In stiffly sprung winged formula and sports racing cars, tyre compliance may be as much as half of the total: the suspension may be as stiff as the tire sidewalls.

 

Considered as a suspension system, a set of tyres is very good in some respects, and horrible in others. For unsprung weight, it's unbeatable. The only unsprung components are the contact patch and some material near it. It has no camber change in ride. On the other hand, it has no camber recovery in roll, and it is seriously underdamped.

 

We might be tempted to decide that we could accept a very high vertical stiffness from the tyre, i.e. a very high tyre spring rate, and get our compliance from the suspension proper, where we can get camber recovery in roll and control the damping properties.

 

However, there is one other factor: the tyre's vertical spring rate is inextricably related to the contact patch size, and the contact patch size is related to the amount of grip we have. As the tyre spring rate approaches infinity, the contact patch length and area approach zero. If the spring rate were truly infinitely large, the contact patch would be a line of zero width front to back, and the contact area would be zero.

 

The original objective of radial tyres was to have greater vertical compliance and a longer contact patch, while still keeping the contact patch flat to the road in cornering.

 

Theoretical considerations aside, for most purposes practical considerations limit our sidewall height. We have to have enough distance between the rim and the ground so that we don't damage the rim on pavement slab edges and potholes. One of the features that has made today's short sidewalls possible has been the development of sidewall designs with a meaty region near the rim flange that protects the rim against both curb scuffs and pothole damage. This is combined with a flexible zone closer to the tread shoulder that provides vertical compliance, albeit over a smaller range than with traditional construction.

 

It is important to note that sidewall height is not the sole determinant of sidewall properties. It is quite possible to put a big, strong bead stiffener in a tall sidewall, and make it act like a short sidewall. It will weigh a bit more, and the brake size will suffer, but the car will corner about the same as would with a short sidewall. I am told that most "radial" racing tyres are not actually radials at all anyway. The main plies are actually not as close to 90 degrees as physically possible. They are more like 70 or 80 degrees – closer to radial than a true bias-ply or the bias-belted street tyres we saw in the '70's, but not truly radial. In other words, relatively stiff construction is still favoured where cornering performance is paramount, and therefore the trend toward short sidewalls for performance tires is fundamentally sound.

Edited June 9, 2009 by Chris Wilson (see edit history)

[1JZGTE]

Thanks Chris, interesting stuff