I'm considering going 16" x 7" front ET31 and 17" x 8" ET38 lightweight wheels for my track wheels.
My theory is shorter sidewall tyres for less deflection and wider tyres for less understeer.
Would this be madness for an MR2?
It's purely a track car so not concerned about loss of ride comfort etc
The famous Jap techno pro mrs runs this set up for track, needs the rear arches rolling though. From memory he uses 245 rear and 225 front.
https://youtu.be/RbjSVa242hc
16/17 is a good track setup if you have a bit more power to be able to push you out of corners.
Also a slightly higher top speed of course with bigger wheels.
Quote from: shnazzle on June 1, 2019, 07:18
Also a slightly higher top speed of course with bigger wheels.
Not with lower sidewall.
15/16 v 16/17
Anyone run both setups and have some feedback?
Quote from: Petrus on June 1, 2019, 09:00
Quote from: shnazzle on June 1, 2019, 07:18
Also a slightly higher top speed of course with bigger wheels.
Not with lower sidewall.
I know very little about tyre technology but I am aware that F1 cars do not run with rubber band like tyres, quite the opposite, with relatively high sidewalls. My thinking is that there is likely a reason for that.
What tracks do you do?
You'd only really benefit with bigger wheels at open, high speed tracks like Silverstone. At tighter, lower speed tracks bigger wheels will be a disadvantage as rotational force will be higher therefore changes in direction will be affected as will braking and acceleration not to mention the additional unsprung weight of the bigger wheels.
Quote from: Joesson on June 1, 2019, 10:59
I know very little about tyre technology but I am aware that F1 cars do not run with rubber band like tyres, quite the opposite, with relatively high sidewalls. My thinking is that there is likely a reason for that.
The F1 current rules require 13" wheels. Proposed rules would move that to a more modern 18" wheel
Quote from: JB21 on June 1, 2019, 11:16
What tracks do you do?
You'd only really benefit with bigger wheels at open, high speed tracks like Silverstone. At tighter, lower speed tracks bigger wheels will be a disadvantage as rotational force will be higher therefore changes in direction will be affected as will braking and acceleration not to mention the additional unsprung weight of the bigger wheels.
Mostly Anglesey and Castle Combe so not really wide open fast tracks.
Not convinced about the bigger wheels by any means but it was something on the radar.
Quote from: Joesson on June 1, 2019, 10:59
I know very little about tyre technology but I am aware that F1 cars do not run with rubber band like tyres, quite the opposite, with relatively high sidewalls. My thinking is that there is likely a reason for that.
There is.
Just think what the huge leap in functionality the invention of the neumatic tyre was.
The air chamber is a progressive spring ánd allows for more compliance.
Lower sidewalls mean less air chamber at a weight penalty with increased directional stability as only advantage.
For track use, where neither the air spring nor the compliance are an issue, the extra stabilty can be advantageous if the wheel weight can be kept in check.
It is highly informative to look at superslowmo of an F1 tyre over the curbstones.
Well you should pick tires before choosing wheels. What tires do you plan to run.
I use to run 15 front and 17 rear wheels mainly because back then 15inch tires were limited to 225inch width. Now that 15 inch tires are available in wider widths I'm back to 15s with 225 front 2445 rear.
The best article about choosing proper tires and wheels that I have come across is this one.
https://motoiq.com/how-to-properly-select-and-size-tires-for-performance/ (https://motoiq.com/how-to-properly-select-and-size-tires-for-performance/)
Quote from: silversprint on June 1, 2019, 20:14
Well you should pick tires before choosing wheels. What tires do you plan to run.
I use to run 15 front and 17 rear wheels mainly because back then 15inch tires were limited to 225inch width. Now that 15 inch tires are available in wider widths I'm back to 15s with 225 front 2445 rear
Do you need spacers to fit 245 at the rear? What offset and width wheels do you run?
I'm on 15s all round but feel I need more width as 195 front and 225 rear seems skittish.
Just to add to the equation, is there any particular need to go for a bigger diameter wheel on the rear?
I understand about the need to have a stagger in tyre size but any benefit to 16/17 v 16/16 with a wider rear wheel?
Quote from: JB21 on June 2, 2019, 10:35
Quote from: silversprint on June 1, 2019, 20:14
Well you should pick tires before choosing wheels. What tires do you plan to run.
I use to run 15 front and 17 rear wheels mainly because back then 15inch tires were limited to 225inch width. Now that 15 inch tires are available in wider widths I'm back to 15s with 225 front 2445 rear
Do you need spacers to fit 245 at the rear? What offset and width wheels do you run?
I'm on 15s all round but feel I need more width as 195 front and 225 rear seems skittish.
Usually we run 15x9 +35mm wheels with 225 front and 245 rear. The 245/40/15 is a short tire and not too hard to fit. Usually track cars run at least -2 degrees of camber on the rear anyway. Spacers are not needed you actually have more room on the inside than the outside. The only issue may be the ears on the lower mounts of some coilovers such as BC might rub the inside of some wheels. YOu can just grind down the ears few mm and it will fit fine.
Quote from: JB21 on June 2, 2019, 10:35
Quote from: silversprint on June 1, 2019, 20:14
Well you should pick tires before choosing wheels. What tires do you plan to run.
I use to run 15 front and 17 rear wheels mainly because back then 15inch tires were limited to 225inch width. Now that 15 inch tires are available in wider widths I'm back to 15s with 225 front 2445 rear
Do you need spacers to fit 245 at the rear? What offset and width wheels do you run?
I'm on 15s all round but feel I need more width as 195 front and 225 rear seems skittish.
Just shouldn't feel skittish with 225 on the rears.
If you keep going bigger you just kill the feel.
Are you sure it's not tyres or suspension setup?
I've never run bigger than 215 and that's was with considerably more power than stock.
My current beast is shod in PFL 185\205 AD08R and I would describe it as lively rather than skittish and that's with a supercharged V6.
Quote from: Dudi on June 2, 2019, 14:18
Just to add to the equation, is there any particular need to go for a bigger diameter wheel on the rear?
I understand about the need to have a stagger in tyre size but any benefit to 16/17 v 16/16 with a wider rear wheel?
Any insight on this?
Quote from: JB21 on June 2, 2019, 10:35
Quote from: silversprint on June 1, 2019, 20:14
Well you should pick tires before choosing wheels. What tires do you plan to run.
I use to run 15 front and 17 rear wheels mainly because back then 15inch tires were limited to 225inch width. Now that 15 inch tires are available in wider widths I'm back to 15s with 225 front 2445 rear
Do you need spacers to fit 245 at the rear? What offset and width wheels do you run?
I'm on 15s all round but feel I need more width as 195 front and 225 rear seems skittish.
Skittish, suggests something is wrong.
And unlikely to be tyre size.
Quote from: Dudi on June 2, 2019, 21:52
Quote from: Dudi on June 2, 2019, 14:18
Just to add to the equation, is there any particular need to go for a bigger diameter wheel on the rear?
I understand about the need to have a stagger in tyre size but any benefit to 16/17 v 16/16 with a wider rear wheel?
Any insight on this?
The larger diameter vs the front equals a lower section equals less oversteer. This is why Toyota went 15-16 for the FL. Whether you want that for the track is a question of preference and setup.
I reckon you're over thinking it.
16/17 for longer flat track, less deflection, but go for very light alloys if on stock power.
15/16 for fast road.
Tommyzoom used 15/15 I believe, and methinks he does rather well :)
Lotus Elise does 16/17.
Follow what the other track boys do. A lot of it is preference. Just don't do 17/17, in my opinion
Quote from: Petrus on June 2, 2019, 22:56
Quote from: Dudi on June 2, 2019, 21:52
Quote from: Dudi on June 2, 2019, 14:18
Just to add to the equation, is there any particular need to go for a bigger diameter wheel on the rear?
I understand about the need to have a stagger in tyre size but any benefit to 16/17 v 16/16 with a wider rear wheel?
Any insight on this?
The larger diameter vs the front equals a lower section equals less oversteer. This is why Toyota went 15-16 for the FL. Whether you want that for the track is a question of preference and setup.
Er... really? So all being equal going up a wheel size but keeping the same width, you say it would have more grip?
Quote from: 1979scotte on June 2, 2019, 19:32
Quote from: JB21 on June 2, 2019, 10:35
Quote from: silversprint on June 1, 2019, 20:14
Well you should pick tires before choosing wheels. What tires do you plan to run.
I use to run 15 front and 17 rear wheels mainly because back then 15inch tires were limited to 225inch width. Now that 15 inch tires are available in wider widths I'm back to 15s with 225 front 2445 rear
Do you need spacers to fit 245 at the rear? What offset and width wheels do you run?
I'm on 15s all round but feel I need more width as 195 front and 225 rear seems skittish.
Just shouldn't feel skittish with 225 on the rears.
If you keep going bigger you just kill the feel.
Are you sure it's not tyres or suspension setup?
I've never run bigger than 215 and that's was with considerably more power than stock.
My current beast is shod in PFL 185\205 AD08R and I would describe it as lively rather than skittish and that's with a supercharged V6.
Could be alignment as I've not had it done since buying the car, also could be the suspension setting. This is only on track mind.
Looking back the car was more skittish on 195 15 front/225 16 rear on NS2Rs v 195 15 front 225 15 rear on AR1's. Think this is due to the lower grip from the Nankangs with Miester Rs on full soft. Once i fitted the AR1s and upping the dampers it felt much better.
You can see the difference in my video below, lots more steering input required with the road tyres.
https://youtu.be/wWqJfY7Mu6M
Quote from: JB21 on June 3, 2019, 09:46
Quote from: 1979scotte on June 2, 2019, 19:32
Quote from: JB21 on June 2, 2019, 10:35
Quote from: silversprint on June 1, 2019, 20:14
Well you should pick tires before choosing wheels. What tires do you plan to run.
I use to run 15 front and 17 rear wheels mainly because back then 15inch tires were limited to 225inch width. Now that 15 inch tires are available in wider widths I'm back to 15s with 225 front 2445 rear
Do you need spacers to fit 245 at the rear? What offset and width wheels do you run?
I'm on 15s all round but feel I need more width as 195 front and 225 rear seems skittish.
Just shouldn't feel skittish with 225 on the rears.
If you keep going bigger you just kill the feel.
Are you sure it's not tyres or suspension setup?
I've never run bigger than 215 and that's was with considerably more power than stock.
My current beast is shod in PFL 185\205 AD08R and I would describe it as lively rather than skittish and that's with a supercharged V6.
Could be alignment as I've not had it done since buying the car, also could be the suspension setting. This is only on track mind.
Looking back the car was more skittish on 195 15 front/225 16 rear on NS2Rs v 195 15 front 225 15 rear on AR1's. Think this is due to the lower grip from the Nankangs with Miester Rs on full soft. Once i fitted the AR1s and upping the dampers it felt much better.
You can see the difference in my video below, lots more steering input required with the road tyres.
https://youtu.be/wWqJfY7Mu6M
Ah, you bought the Kaveney car? That had quite an unusual geo if I remember right? More front camber than rear?
Quote from: james_ly on June 3, 2019, 09:10
Er... really? So all being equal going up a wheel size but keeping the same width, you say it would have more grip?
That is NOT what I am writing.
Ceterus paribus, going up a size in diameter front and rear keeps the same balance Toyota intended with the FL largere rear rim; gives less sideways roll on the tyres because of lower sidewall; it does NOT give more grip.
If you just want more grip: Go the lightest rims in standard size possible, standard size, the best rubber you can afford.
Be aware that first and foremost it is the rubber that is the contact patch, what determains limits of adhesion.
Seccond come how the driver drives. Néxt is what is needed to compensate for the former. I myself per example deliberately stayed on El Cheapo rubber to discover how the car behaves; the lower grip lowering the speeds giving me more time to respond. When I had more or less learned hw to drive around the car´s peculiarities, I invested in lightweight rims in OEM size and AD08Rs and subsequently learning about the car again at the next level.
The moral of the above; it´s not in 16/17 ;)
Quote from: james_ly on June 3, 2019, 09:51
Quote from: JB21 on June 3, 2019, 09:46
Quote from: 1979scotte on June 2, 2019, 19:32
Quote from: JB21 on June 2, 2019, 10:35
Quote from: silversprint on June 1, 2019, 20:14
Well you should pick tires before choosing wheels. What tires do you plan to run.
I use to run 15 front and 17 rear wheels mainly because back then 15inch tires were limited to 225inch width. Now that 15 inch tires are available in wider widths I'm back to 15s with 225 front 2445 rear
Do you need spacers to fit 245 at the rear? What offset and width wheels do you run?
I'm on 15s all round but feel I need more width as 195 front and 225 rear seems skittish.
Just shouldn't feel skittish with 225 on the rears.
If you keep going bigger you just kill the feel.
Are you sure it's not tyres or suspension setup?
I've never run bigger than 215 and that's was with considerably more power than stock.
My current beast is shod in PFL 185\205 AD08R and I would describe it as lively rather than skittish and that's with a supercharged V6.
Could be alignment as I've not had it done since buying the car, also could be the suspension setting. This is only on track mind.
Looking back the car was more skittish on 195 15 front/225 16 rear on NS2Rs v 195 15 front 225 15 rear on AR1's. Think this is due to the lower grip from the Nankangs with Miester Rs on full soft. Once i fitted the AR1s and upping the dampers it felt much better.
You can see the difference in my video below, lots more steering input required with the road tyres.
https://youtu.be/wWqJfY7Mu6M
Ah, you bought the Kaveney car? That had quite an unusual geo if I remember right? More front camber than rear?
-2.5 degs allround but its toeing in a lot at the rear, 3mm total I think. Needs going on a Hunter Hawkeye to get it bang in though. I'll be going -2.5 degs front, -3 degs rear. Square front toe and a smidge of toe in at the rear.
Quote from: JB21 on June 3, 2019, 09:46
https://youtu.be/wWqJfY7Mu6M
The second part seems to be less initial understeer.
How are you adjusting to rwd going ínto corners? The weight transfer and entry point needs be different on the MR than on most hot hatches. Not much sense in chasing the set up when you are adjusting your driving to the car or you´l end up chasing your own tail no?!
Reading my earlier answer back I think I may clarify:
with all things the same, the size of front vs rear tyre sets the drift angles of those tyres for that given car.
Change the resp. widths or section hight and this balance shifts noticebly. Departing from the OEM base line there is not really a better or worse, nor more/less grip concering the respective front/rear tyre dimensions; more a personal preference/driving style.
Quote from: Petrus on June 3, 2019, 10:58
Quote from: JB21 on June 3, 2019, 09:46
https://youtu.be/wWqJfY7Mu6M
The second part seems to be less initial understeer.
How are you adjusting to rwd going ínto corners? The weight transfer and entry point needs be different on the MR than on most hot hatches. Not much sense in chasing the set up when you are adjusting your driving to the car or you´l end up chasing your own tail no?!
Yeah adjusting to the MR layout has been a challenge so far. With front crawlers you can just throw them in hot and if it starts to go wrong then mash the throttle to drag you out again.
I'm just being patient with the MR layout trying different lines in and out, braking techniques, trying to learn oversteer in a controlled environment etc. Still got lots to learn but it definitely takes more skill and balls to drive fast.
Back at Blyton again in a few weeks to hone it further, then to my home track of Oulton which will be the real test.
From the video the car setup looks good, going pretty much where you point it. You look pretty comfortable with it IMO
Tire diameter is a consideration when going up in tires. You never want to raise the car with a strut suspension with taller wheels/tires, then try to bring it back down with the suspension. The rear suspension on this car is already somewhat compromised. Angling the control arms up just makes it worse. Ideal setup would ride height as low as possible and suspension geometry correct.
However sometimes you can go up a wheels size because a better lower profile tire is available. The ride height doesn't change because of the lower profile.
Never use random alignment numbers from the internet. Tire size, corner weights, spring rates, swaybar, Aero, all affect alignment. Learn to use a tire temperature probe and dial in your own suspension.
Camber isn't for changing handling. It's for maximizing contact patch.
I have never had to run more camber on the rear of my car. It's not right or wrong. It's just what give the correct tire temperatures on my car.
Quote from: silversprint on June 3, 2019, 17:15
Camber isn't for changing handling. It's for maximizing contact patch.
I have never had to run more camber on the rear of my car. It's not right or wrong. It's just what give the correct tire temperatures on my car.
Tyre temp on a given car is almost exclusively dependent on driving style. As such there is indeed no golden rule fitting all. Nevertheless it is véry helpful to have a well argumented point of departure.