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Discussion Starter #1
Hi guys,

I am building my MR2 as a streetable track car with roughly 280 hp. The wheels I have for it are 16x7. Based on the driving characteristics of the mid engine layout, I'm trying to figure out what the best tire size setup would be for track racing. I'm stuck between running a square stance 205/45/16 or running 225's in the rear with 205's in the front. Since this car is known for snap oversteer which I'm not sure how bad it is, my assumptions are that running a staggered stance would help with handling sudden weight transfer with squatting. Trying to go for a balanced and predictable feel. Any experience or input is welcome! Thanks
 

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280hp sounds like a very fun car! I'm jealous!

I had quite a handful with only 130hp on my 1991 MR2 with about 2000 on-track miles from lapping sessions. My students were amazed at how fast we caught up to Porsche Boxsters, STI's and race-prepped spec-miatas under braking and corners even though they all blew past us in the straight.

I don't know your knowledge or skill level, but one thing you may want to consider is working backwards from what you want to achieve on track. Are you going for ultimate lap-times, top speed, just fun with high-G cornering with mostly street use? The front vs rear wideness aspect is but one tuning factor among many when prepping your car. When I had 16" Nissan ZX300 wheels on my MR2 for a few seasons I used the cheapest auto-x style tire available at the time. I went as wide as possible without rubbing at full suspension compression with stock (not lowered!!!) springs and moderately rolled fenders in the rear. That ended up being 215/45/16 F 245/45/16 R Hankook RS-2s. The wheels were 8" in the rear and 7" in the front which supported the tire sidewalls very well. I then moved on to 17" Nissan 350Z wheels as tire choices dwindled in the 16" sizes and ended up with 215/40/17 F 245/40/17 R.

With 16x7 in front and rear I suspect you won't get much real-world difference in the width of the contact patch front vs rear. 205 front and 215 or 225 rear ought to be a good starting point. But it would probably be better to go with the top choice rubber in a non-optimal front to rear size ratio and dial in handling via alignment and tire pressures than go for a lesser choice of rubber just to get some arbitrary F/R ratio.

P.S. Don't fear snap oversteer - its a bit of a myth. You can get any car to oversteer given a particular set of inputs. All inputs should be firm, deliberate, but minimal to avoid shenanigans on track - it takes practice practice practice. Whatever $$$ you spend on parts upgrading your car, plan to spend 2X-5X that for track time learning how to master your technique. Its the only way to get true value from your investment. Wider rear tires and a dialed-in alignment does lessen the learning curve though.
 

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Get the Wilhelm Racing geometry correction kit - this will get rid of the snap oversteer. Also consider disconnecting the rear sway bar. I am on the above mods along with fortune auto coilovers and godspeed front sway bar (rear disconnected) and I've NEVER experienced snap over steer on a square setup (215/45/16 azenis). I took it to the track and was passing miatas, s2ks and even a turbo FRS in the turns with stock engine - handling was neutral with slight understeer at entrance and very controllable slight oversteer at the limit. I also go to canyons regularly and never lose traction. People who tune their 2s without correcting suspension geometry will never reach the limits of the car.
 

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P.S. Don't fear snap oversteer - its a bit of a myth. You can get any car to oversteer given a particular set of inputs. All inputs should be firm, deliberate, but minimal to avoid shenanigans on track - it takes practice practice practice. Whatever $$$ you spend on parts upgrading your car, plan to spend 2X-5X that for track time learning how to master your technique. Its the only way to get true value from your investment. Wider rear tires and a dialed-in alignment does lessen the learning curve though.
Yes and no. It's a bit of a myth that the car will spin for no reason. But there are underlying mechanical and physical reasons WHY these cars are a little tricky to drive at the limit, and some of them can be corrected.

Get the Wilhelm Racing geometry correction kit - this will get rid of the snap oversteer. Also consider disconnecting the rear sway bar. I am on the above mods along with fortune auto coilovers and godspeed front sway bar (rear disconnected) and I've NEVER experienced snap over steer on a square setup (215/50/17 azenis). I took it to the track and was passing miatas, s2ks and even a turbo FRS in the turns with stock engine - handling was neutral with slight understeer at entrance and very controllable slight oversteer at the limit. I also go to canyons regularly and never lose traction. People who tune their 2s without correcting suspension geometry will never reach the limits of the car.
Thanks! Glad you are enjoying it.
 

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As far as the tires go, I would stick with a 1" wheel stagger, and a 20-30mm tire stagger. I personally wouldn't go less than an 8" front / 9" rear, with a 225-235 front and a 245-255 rear. But, plan on rolling the fenders in this case.

Exact tire choice depends on how serious you are, and if you want a streetable tire, or something that's more track only. I quite like my Maxxis RC1's, pretty grippy, reasonably cheap, and hold up very well. The Nitto NT01 is another good track day tire option.
 

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I actually have 16x7 wheels with 215/45/16 rt615s. Alex W do you think 225/45/16 would fit front and rear without rolling? I really like the square setup, I was able to grip as well or better than an 05 WRX on decent tires with this setup in the canyons this past weekend even though the azenis are almost three years old with very little loss of traction(some dirt caused some sliding for both of us but not uncontrollable). The WRX driver and I are both experienced with multiple track days so it's not skill level difference - what benefits would a staggered setup have vs a square setup using your geometry correcting kit? Seems like it would make the car understeer more, which I guess would benefit high horse power setups but my car is only pushing maybe 190-200 rwhp (I/e/boost). Thanks
 

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You can fit 225/45-16 up front. I did that at one point. Just barely clears the stock strut housings, and shouldn't be an issue on coilovers either. You do end up with the potential for rubbing at full lock on the inside rear corner as you go wider / larger diameter, but I don't recall having any issues with those sizes.

The stagger mostly comes down to weight distribution. In a purely theoretical sense, a car with 50/50 weight distribution should have equal tire width front and rear. With a rear weight bias, a little extra rear tire makes sense regardless of power level. Plus, the MR2 naturally fits larger rear tires than it does front tires. IE, you will max out the stock front fenders at about a 225 or 235, but the stock rears can easily take a 255. So my theory is, rather than reducing the rear tire size to match the front, maximize them both (within reason), and then fine tune the handling to maximize grip from both ends as well.

That said, if you like the current setup and don't find it to have any excess over steer, there isn't much reason to change it.
 

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Discussion Starter #8
280hp sounds like a very fun car! I'm jealous!

I had quite a handful with only 130hp on my 1991 MR2 with about 2000 on-track miles from lapping sessions. My students were amazed at how fast we caught up to Porsche Boxsters, STI's and race-prepped spec-miatas under braking and corners even though they all blew past us in the straight.

I don't know your knowledge or skill level, but one thing you may want to consider is working backwards from what you want to achieve on track. Are you going for ultimate lap-times, top speed, just fun with high-G cornering with mostly street use? The front vs rear wideness aspect is but one tuning factor among many when prepping your car. When I had 16" Nissan ZX300 wheels on my MR2 for a few seasons I used the cheapest auto-x style tire available at the time. I went as wide as possible without rubbing at full suspension compression with stock (not lowered!!!) springs and moderately rolled fenders in the rear. That ended up being 215/45/16 F 245/45/16 R Hankook RS-2s. The wheels were 8" in the rear and 7" in the front which supported the tire sidewalls very well. I then moved on to 17" Nissan 350Z wheels as tire choices dwindled in the 16" sizes and ended up with 215/40/17 F 245/40/17 R.

With 16x7 in front and rear I suspect you won't get much real-world difference in the width of the contact patch front vs rear. 205 front and 215 or 225 rear ought to be a good starting point. But it would probably be better to go with the top choice rubber in a non-optimal front to rear size ratio and dial in handling via alignment and tire pressures than go for a lesser choice of rubber just to get some arbitrary F/R ratio.

P.S. Don't fear snap oversteer - its a bit of a myth. You can get any car to oversteer given a particular set of inputs. All inputs should be firm, deliberate, but minimal to avoid shenanigans on track - it takes practice practice practice. Whatever $$$ you spend on parts upgrading your car, plan to spend 2X-5X that for track time learning how to master your technique. Its the only way to get true value from your investment. Wider rear tires and a dialed-in alignment does lessen the learning curve though.
That's great advice. I think it would be better to start with a good tire and hone in on my driving skills like you're saying. i've been to a few autocrosses and one track day with my daily and had some training at some test tracks for my job, but nothing too intensive. I did see the rear suspension geometry correction kit and read Alex's writeup on it. What type of differences have you seen with it?
 

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Discussion Starter #9
Get the Wilhelm Racing geometry correction kit - this will get rid of the snap oversteer. Also consider disconnecting the rear sway bar. I am on the above mods along with fortune auto coilovers and godspeed front sway bar (rear disconnected) and I've NEVER experienced snap over steer on a square setup (215/45/16 azenis). I took it to the track and was passing miatas, s2ks and even a turbo FRS in the turns with stock engine - handling was neutral with slight understeer at entrance and very controllable slight oversteer at the limit. I also go to canyons regularly and never lose traction. People who tune their 2s without correcting suspension geometry will never reach the limits of the car.
That's interesting. I'll have to play around with suspension and get a feel for both with sway bar and without. Thanks for the advice
 

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Thanks for the input. I will probably go staggered at one point but I just found out the RT615+ only come in 215/45/16 and 225/50/16 - 50s would be too tall correct? They're my favorite street tire by far (ran around 3 sets on multiple cars so far) so I may just end up staying with square 215/45/16. Your explanation for a staggered setup does make sense though - maybe when I get more funds saved Ill get an extra set of track tires with a staggered setup because more tire is desirable; another benefit of the square setup is being able to rotate tires. Thanks again.
You can fit 225/45-16 up front. I did that at one point. Just barely clears the stock strut housings, and shouldn't be an issue on coilovers either. You do end up with the potential for rubbing at full lock on the inside rear corner as you go wider / larger diameter, but I don't recall having any issues with those sizes.

The stagger mostly comes down to weight distribution. In a purely theoretical sense, a car with 50/50 weight distribution should have equal tire width front and rear. With a rear weight bias, a little extra rear tire makes sense regardless of power level. Plus, the MR2 naturally fits larger rear tires than it does front tires. IE, you will max out the stock front fenders at about a 225 or 235, but the stock rears can easily take a 255. So my theory is, rather than reducing the rear tire size to match the front, maximize them both (within reason), and then fine tune the handling to maximize grip from both ends as well.

That said, if you like the current setup and don't find it to have any excess over steer, there isn't much reason to change it.
 

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That's interesting. I'll have to play around with suspension and get a feel for both with sway bar and without. Thanks for the advice
Yeah and get Alex's geometry correction kit for sure - your car will just grip and grip. Even with azenis I was getting tail happy in the canyons just from boosting a little, after installing the kit the difference in stability is huge.
 

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Discussion Starter #12 (Edited)
Went back to this thread and read the responses again. Finally finished the 4th gen swap and am extremely excited to get on track next month.

Here is what tire setup I decided on and why:

Street setup:
-R32 Skyline GTR Wheels 16x8
-1/2" wheel spacers in rear
-Firehawk Indy 500 205/45/16 square setup
*$360 all together

Track setup:
-Ray's Volk Racing 5 spoke
*17x9 rear, 17x8 front
*Not sure what they're called, older model
-Falken Azenis RT615K+
*245/45/17 Rear
*225/45/17 Front
*$540 all together

I went with a square stance for my daily driving duties for a few reasons. This gives me the ability to rotate my tires and prolong their use, I've used the Firehawk Indy 500 on other cars and think they're possibly the best bang-for-buck summer tires on the market, the tire size/diameter is extremely close to stock (0.6% difference) and I want to go for a stock look and feel on my daily setup.

I picked the Falken Azenis RT615K+ for a few reasons as well. After driving on the "skinny" Indy 500's and hooking up surprisingly well in turns and finding it difficult to even break traction when these are warmed up, I decided to not go for a autocross tire. I didn't realize how much of a myth this cars' handling downsides are, I found it extremely balanced. Anyway, this setup I really think will limit oversteer, hook up extremely well, and still leave me with a balanced setup and should last a couple track days/autocrosses. The Falkens are about $200 cheaper than the Potenza RE's which are the benchmark in extreme performance summers, again trying to go for best bang for buck. Again keep in mind my car is running about 300hp with the swap, so your MR2 may not need such a wide tire in the rear.

Again, thanks for the advice everyone
 

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I plan to try 225’s up front next...but I ran 215/245 and had no complaints on over steer... but once I added 255’s, the car’s oversteer was even less... so the wider in back the better.. as for the fronts I don’t get much under steer at all, but moving to a 225 is more of a fitment quest
 

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An earlier poster mentioned unhooking the rear sway - how does this affect the car's handling?
It improves rear grip, but you do have to have reasonably stiff springs for it to work or you will probably just end up with too much body roll.
 

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It improves rear grip, but you do have to have reasonably stiff springs for it to work or you will probably just end up with too much body roll.
Ya that’s exactly what happens... then to correct like you said, gotta really stiffen things up... my car would skip and I hated it... I run the suspension on the softest setting... I don’t like that To tight chassis suspension feel...
 

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Ya that’s exactly what happens... then to correct like you said, gotta really stiffen things up... my car would skip and I hated it... I run the suspension on the softest setting... I don’t like that chassis suspension feel...
What kind of dampers?

I run my dampers pretty soft as well, it's usually faster in my experience. And easier to drive. But you need spring rate to keep the car off the bump stops and to keep body roll under control.
 

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What kind of dampers?

I run my dampers pretty soft as well, it's usually faster in my experience. And easier to drive. But you need spring rate to keep the car off the bump stops and to keep body roll under control.
I have BC’s with Swift 180/375lbs, 7” Long.. ya the too stiff thing isn’t for me either... BC’s aren’t the best, but with the springs it’s not bad... I’m not slammed either so that helps
 

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I also noticed a slight improvement in rear tire grip by not having a rear sway bar. But IMO, there are more negatives than positives. The almost negligible grip improvement isn't worth not only the extra body roll, but what also felt like a slight twist in the body/frame on low to mid speed quick adjustments - like in slalom type conditions or abrupt lane changes. The steering was tons easier w/ 2 sway bars and the car felt much better balanced despite having less grip in the rear - 4 wheel drifts were very easy to do as well and the car was just a lot funner to drive - and that's more important to me. The added rear grip just wasn't worth losing all of that driveability.

As for track tires: For what it's worth, on an SW20 I've never had better track times than 225/50-15 (15x7) and 245/45-16 (16x8.5) on lightweight Kosei K1 wheels. It was confidence inspiring and also surprisingly stable at triple digit speeds. That was a magical combo that's damn near impossible to put together today, I definitely miss the option of swapping to it.

 

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Discussion Starter #20
I also noticed a slight improvement in rear tire grip by not having a rear sway bar. But IMO, there are more negatives than positives. The almost negligible grip improvement isn't worth not only the extra body roll, but what also felt like a slight twist in the body/frame on low to mid speed quick adjustments - like in slalom type conditions or abrupt lane changes. The steering was tons easier w/ 2 sway bars and the car felt much better balanced despite having less grip in the rear - 4 wheel drifts were very easy to do as well and the car was just a lot funner to drive - and that's more important to me. The added rear grip just wasn't worth losing all of that driveability.

As for track tires: For what it's worth, on an SW20 I've never had better track times than 225/50-15 (15x7) and 245/45-16 (16x8.5) on lightweight Kosei K1 wheels. It was confidence inspiring and also surprisingly stable at triple digit speeds. That was a magical combo that's damn near impossible to put together today, I definitely miss the option of swapping to it.

Very nice. I feel like I'd prefer to keep the sway bars as well. One question that I thought of too after reading this is that I wonder if there are also any adverse effects by going with a larger tire diameter. If we compare our setups we have the same tire widths however your tire diameter is 23.86" front and 24.68" rear while mine is a bit bigger with 24.97" front 25.68" rear. I'm wondering if there is a noticeable loss in wheel torque or anything
 
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