Aftemarket wheels and tires for roadracing

[JPDsupra]

Which are the most lightweight wheels available on the market. There are some carbon fiber wheels from Dymag which weigh 14lbs but ive heard there are lighter wheels on the market?

[pwpanas]

Originally Posted by JPDsupra

Which are the most lightweight wheels available on the market. There are some carbon fiber wheels from Dymag which weigh 14lbs but ive heard there are lighter wheels on the market?

As strange as this sounds, and for what it's worth, I'd recommend that you should not use weight as your primary criteria for rim selection. Imho, rim width is far more important, for an MKIV Toyota Supra Turbo (especially one that has been, or will soon be, upgraded). As you know, the Mkiv Supra Turbo, generally speaking, is a high-horsepower rwd vehicle, and the wheels that need to be on this type of vehicle need to be appropriate for that design. The widest rim that will fit on the oem Mkiv Supra body (jza80), without modification, and with the correct offset, is 11.5" wide. This will allow you to run 315s, which will actually have a chance of 'hooking up' all of that horsepower. If you go and (for example) put some skinny 9" wide rims on the car, you'll just sit there and spin, even at modest 'bpu' horsepower levels. In other words, lighter rims can make you slower (not faster) if they're an inappropriate width. Now, the trouble is that if you limit your wheel/rim brand/model selections to those you can get in an 11.5" width, you'll find it to be somewhat limited. A few of the brands I'm aware of that do come in that width are Fikse, Forgeline, Kinesis, CCW, and HRE. Although I personally have no experience with "Dymag" carbon-fiber rims, it's probably unlikely that they come in an 11.5" width...

Of course, after you do find a few choices for 11.5" width rims, with the correct offsets for the jza80, and rims strong enough for your application, weight can & should be one of the criteria that you use to select among them. Just mho fwiw, and ymmv...

[JPDsupra]

thanx but i know the thing about width and traction and how skinny tires can make you slow but i was just wonderin what were the most lightweigt rims

[pwpanas]

Originally Posted by JPDsupra

thanx but i know the thing about width and traction and how skinny tires can make you slow but i was just wonderin what were the most lightweigt rims

Fwiw, I've heard that magnesium wheels are among the lightest, although generally not ideal for street use. Apparently the magnesium alloy, although very light, also tends to be brittle and will (for example) break/crack rather than bend if you hit a pothole too hard.
http://www.buywheelstoday.com/images_products/1279.jpg

Unfortunately, I doubt that these Enkei magnesium rims (or any ultra-light magnesium rims) are available in the correct width/offset combo for the jza80 chassis.

Update: I've heard that Forgeline and iForged also have ultralightweight magnesium rims. Since I know Forgeline does make an 11.5" wide rim, this might be an optimal choice for overall performance (if their magnesium alloy rim is available in that width).

[Bolarbag]

Massive can of worms here, but from what I've been told and learnt over the last few years is wide rims and wide tyres do not guarantee the power getting put down on the road

The car has got to stick close to stock offsets, widths and similar rolling radius' as possible for optimum handling

Simply the R&D of Toyota can't be matched for this car and chasis, regardless of power output, obviously there will be slight le-way where you may change one aspect which will in turn affect another suspension wise - but it would be that small that you would barely notice a difference to your track times or your feel

Slapping 11.5inch wheels - guaranteeing a 315minimum fitament is not the way you want to go if your looking to keep the stock handling - which tweaked properly is very very good

In Drag cases its completely different - go as wide as you can with a very soft spring rate rear and you will knock seconds off your 1/4mile but street driving will not be anything like the optimum with a setup like that

I used to want as wide a wheels as poss - I have now went from 19-18's to try to stick with stock offsets and RR's they car feels much more planted now and I get more grip even with a narrower tyre

The minimum tyre width b.t.w will be stock - 255 iirc - best go with stock U.S wheel width 9.5inch and a 265 or 275tyre

With a good setup Lexus GS300 Sport Rims will do also as they have a stock offset and come in anything up to a 10.5inch wheel, however the suspension will need setup for optimum handling and grip especially the wider you go

On the front you want to keep it staggered - 8.5inch wide wheel for optimum turn in anything wider you begin to tramline, theres pretty much no benefit to running wider on the front on the sup

Check out the car Bible its a very interesting read and something you dont want to believe at first - especially regarding contact patch - it defies rational logic Car maintenance : Everything you need to know about wheels and tyres.

And to answer the initial question - stick with forged rims as you can have a very light cast wheel but it could break pretty easily, Volk RE30's are only 6.8Kg's a rim (18inch)

[pwpanas]

Originally Posted by Bolarbag

Massive can of worms here, but from what I've been told and learnt over the last few years is wide rims and wide tyres do not guarantee the power getting put down on the road

The car has got to stick close to stock offsets, widths and similar rolling radius' as possible for optimum handling

Simply the R&D of Toyota can't be matched for this car and chasis, regardless of power output, obviously there will be slight le-way where you may change one aspect which will in turn affect another suspension wise - but it would be that small that you would barely notice a difference to your track times or your feel

Slapping 11.5inch wheels - guaranteeing a 315minimum fitament is not the way you want to go if your looking to keep the stock handling - which tweaked properly is very very good

In Drag cases its completely different - go as wide as you can with a very soft spring rate rear and you will knock seconds off your 1/4mile but street driving will not be anything like the optimum with a setup like that

I used to want as wide a wheels as poss - I have now went from 19-18's to try to stick with stock offsets and RR's they car feels much more planted now and I get more grip even with a narrower tyre

The minimum tyre width b.t.w will be stock - 255 iirc - best go with stock U.S wheel width 9.5inch and a 265 or 275tyre

With a good setup Lexus GS300 Sport Rims will do also as they have a stock offset and come in anything up to a 10.5inch wheel, however the suspension will need setup for optimum handling and grip especially the wider you go

On the front you want to keep it staggered - 8.5inch wide wheel for optimum turn in anything wider you begin to tramline, theres pretty much no benefit to running wider on the front on the sup

Check out the car Bible its a very interesting read and something you dont want to believe at first - especially regarding contact patch - it defies rational logic Car maintenance : Everything you need to know about wheels and tyres.

And to answer the initial question - stick with forged rims as you can have a very light cast wheel but it could break pretty easily, Volk RE30's are only 6.8Kg's a rim (18inch)

With stock-width rear tires (255s) on an APU Mkiv Supra Turbo (eg. 750rwhp+), the puppy will just spin/slide...you'll have almost zero control in the rear when boost hits. Please note that I actually agree with you, IF (and only if) you keep your Mkiv TT bone-stock, then the oem rims & offsets are ideal. But if you reengineer the driveline, you also have to reengineer other parts of car, like the rim widths (along with the alignment and suspension to match, of course). This is speaking from hard-learned evidence and the twisted scraps of metal that once-were beautiful Mkivs. Of course, the choice and the freedom to experiment is yours. Alternatively, if you want to go with what has been proven to work in a 750rwhp+ Mkiv, get some 11.5" width rims in the rear, with a tall profile (eg. 35s or 40s) tire, preferrably race rubber (assuming dry conditions), proportionally wide front rims&tires to match, and watch it grip and handle (on a roadrace course - not a dragstrip) after the upgrades. Don't and ... well let's just hope your car insurance AND your life insurance policies are both up to date.

Your post flies in the face of almost all roadrace modifications that are done, and wider tires do have more lateral grip for a given vertical load. For example, most modified Vettes and Vipers all run 335s all the way around. Porsches with flared fenders to accommodate extremely wide rubber is commonplace on roadrace tracks. Agreed oem handling is good, but my personal experience says wider is a LOT better. Despite all of this, I really do welcome you to prove otherwise. Put a 750rwhp+ Mkiv on the skidpad with oem rims&tires and g-meter, and post the results here. Then slap some 10s&275s up front and some 11.5s&315s in the rear, with proportionally similar sidewalls (i.e. don't put some super-low profile rubber on the rear), same brand/model/rating of the rubber too, and re-test. My money's on the retest with wider rims giving you a much higher G rating.

Here's a quote that might help:
"...when you look at lateral grip (side force) other factors start to matter. The tyre develops side force because of the slip angle between the tyre and the road. This slip angle means the tread is being pulled sideways by the road surface. At the front of the contact patch the deflection is relatively small. As you move back along the contact patch the deflection increases steadily. At some point, the sideways forces in the tyre exceed the friction between the tread and the road and the tread starts to slip relative to the road. When the tread is slipping like this it produces less grip on the road. Now imagine increasing the slip angle and imagine what effect this has on the side force. As the slip angle increases the sideways deflection builds up quicker so the front of the contact patch works harder. But more and more of the back of the contact patch is sliding and losing grip. At some point you reach a maximum point where more slip angle means less side force because you are losing more grip at the rear of the contact patch that you are gaining at the front. This is often referred to as 'breaking away' where you ask the tyre for more grip and end up getting less.

The longer the contact patch is, the more gradually this break away occurs. If you shorten the contact patch, the break away occurs more abruptly but you get more absolute grip at the peak. This is because there is less variation in sideways distortion between the front and back of the contact patch, more of the contact patch reaches maximum grip and starts to slide at the same point. Having a shorter contact patch also means you get less self-aligning torque so there is less feedback through the steering about how close the tyres are to breaking away.

When you fit wider tyres, what you're doing is making the contact patch wider and shorter for the same tyre pressure. This means you get a more abrupt breakaway but more grip right on the limit. The disadvantage is more expensive tyres, more tramlining and steering kickback, more wind and rolling resistance and noise, less grip in slippery conditions, a more abrupt breakaway to catch out the unwary driver and less warning through the steering about how close the tyres are to breaking away. "

Lastly, consider a couple of things:
1) The contact patch actually isn't the same with narrow vs. wide, since the steel belts in the radial change the shape of the contact patch.
2) Wider rims & tires means a wider wheelbase...which in turn adds noticeably to the lateral stability (you can actually feel a difference, through the first hard corner you turn after running wider rims).

Again, imho, wider is always better.

[Bolarbag]

Ok I was hoping I was wrong in all honesty - my post above is what my thinking has been directed to after a few years as logical thinking has always been wider tyres on wider, approriate wheels = more grip

I'm the first to admit, I have knowledge in almost all aspects of the car apart from suspension and handling - I just havent done much research on it as I have been busy speccing my engine,fueling,management e.t.c

I have always wondered how/why in the UK people run close to stock widths whereas in the U.S you guys seem to run 10s upfront and 11.5's rear

We have pretty much two supras in the UK that run Timeattack, they run 10.5up rear and 9 at the front, they dont particularly run fast times - well in comparison to the 4wheel drives and the ubber responsive GT2's, their my benchmark

So I'm currently speccing my wheel sizes and offsets to suit my Brembo BBK's front and rear, you recommend 10 at the front and 11.5rear on a stock body?

I will be running a super responsive 600bhp and around 550ft/lb of torque with speed dependant boost so I can get the grip down

Wont the wider tyres in the front give me a less responsive turn in - you have to bare in mind that the tracks in the UK are like 100th of the size of the ones in the U.S - i.e my local track I should get round in 58secs, there are a few bigger ones but not longer than 3mins e.t.c however I do intend to go to the Nurburgring this autumn

[pwpanas]

Originally Posted by Bolarbag

...So I'm currently speccing my wheel sizes and offsets to suit my Brembo BBK's front and rear, you recommend 10 at the front and 11.5rear on a stock body?

Yes. Be sure to check the rim diameter you need to clear the brakes. Next, check the sizes of the tires that you plan to purchase and use. You may not be able to get near-optimal 275s or 285s in the front, and 315s in the rear. Maybe you'll end up with 265s up front, and 295s or 305s in the rear instead. Also have one or two back-up tire brands/models in case the company stops producing your first choice. Lastly, get the rim widths to match the rubber you'll be running. When you come close to your decision, please feel free to post here, and we'll provide feedback.

Originally Posted by Bolarbag

...Wont the wider tyres in the front give me a less responsive turn in - you have to bare in mind that the tracks in the UK are like 100th of the size of the ones in the U.S - i.e my local track I should get round in 58secs, there are a few bigger ones but not longer than 3mins e.t.c however I do intend to go to the Nurburgring this autumn

Low profile, wide front tires will give you a MUCH more responsive turn-in. You'll be shocked when you switch from oem 235s to 275s or so up front. Of course, it'll be a bit harder on your power steering, so be sure to follow proper maintenance, and use good fluid (eg Redline Power Steering Fluid).

Hypothetically, if you widened the back tires, and kept the oem front tires the same width, it'd push in the corners (i.e. turn-in would be less responsive). That's why you have to upgrade both the front and the back widths simultaneously and proportionally.

Please post any follow-up questions you have...and good luck with it - please keep us informed!

[95mkiv]

I'm running ccw classic 18X10F and 18X11.5R on mine and they are pretty light specially comparing them to stock 17" factory chrome wheels.

[RZ-rix]

I'm looking for a new set of rims because my older work rims have a offset of +47 on the front which wont probably clear a big brake upgrade package, so does anyone here have any sugestions on what offset is possible for larger calipers such as the brembo or stop tech brakes?