ivan_b28

Hi all of you! I’ll do a bit of an introduction since this is my new post even though I’ve been around here for a while. I began reading here after I started looking for new wheels, soon I head about this guy called Emilio and learnt the importance of running proper rim width for any given tyre (hell I used to run 225/45 on a 15x7!).

so I bought a set of 15x8 for the fronts and 15x9 for the rears. Here’s where you might ask why the f*ck is this guy running staggered on a Miata. Well my dirty secret is that I don’t even have a Miata… but this is the only place I’ve seen quality talk about tire/wheel combos so thought this would be the only place I’d get good advice.
my car is a Toyota mr2 spyder with a 2zz-ge swap which I take to the track every time i can.

here’s the thing, I’m currently running a square 205/50 setup on my staggered wheels. Reason? Costs. First tire setup I bought for these new wheels were 205 and 225 nankang ar1 which worked pretty good, but since I’m in Spain and wide tire market for 15’ is almost non existent and I wanted a cheap alternative for a while I bought these nankang ns2r to have some fun.

how stretched do the rears look?




my car weights roughly 1000kgs and it’s on 8/10k springs. I always aim to be at 26psi (hot) while on track. Is this too low for this stretch? Possibilities of debeading? Can/should I try a bit lower?

thanks in advance for the answers!

sixshooter

iTrader: (12)

Tire looks good. The car should feel tighter and more accurate on the same tires with a little stretch.

We don't discriminate against MR Spyder owners here. We are enthusiasts first and track guys are welcome.

My car likes around 30psi hot for track tire pressures. 26 hot may be loose and sloppy with some brands and setups. Test and record the data to see what is best for your car, tires, and setup.


And welcome to the forum.

Gee Emm

Welcome! Photos or it didn't happen/doesn't exist! I've always had a soft spot for MR2s, almost bought one back in the day!! Have a cat for encouragement ...

Get a probe pyrometer, pencil, paper. Learn to take temperatures across the tyre tread. Experiment, cross check with lap times. Note that tyre temps will tell you a lot about suspension setup, that should be your priority, when hard driven you get pretty even temps - if you get uneven temps, learn what makes them differ - suspension settings and pressures being the two variables.

Regarding tyre choice, being EEC should facilitate cross-border imports? Must be good sources in France, Germany, probably elsewhere? But shipping from US or UK now is more difficult expensive?

ivan_b28

thanks for the answers and accepting the no-Miata ownership 🤣

So I’m assuming it’s a safe stretch and I shouldn’t worry about debeading. at what point would pressure be concerning and risk popping out the bead?

I should really get a tiré pyrometer and start taking notes to get the best out of my setup, but I might change it to something more compliant on bumpy surfaces. Main issue is… I’m on bc racing rm coilovers… so on flat track car works fine, but on bumpy tracks it’s a different story. I’m thinking about switching to lower spring rates or revalving them.

about tire market on EEC, yes I can buy anything easily but the problem is that tire market in Europe just doesn’t care about wide 15’ hahah.

these are the only options I have:
-nankang ar1 and cr-s on 225 and 245, but they are pretty expensive and I can’t afford a set of these every 3 track days
-yoko a052, same issue as above.
​​​​​​-Toyo r888r on 225, expensive for what they are, a tad cheaper than ar1.
-federal rs-rr 225 would be a great cheap alternative but it seems like federal is dying since stocks haven’t gone back up after a year or so…

just so you can compare, a full ar1 setup (205/225) costs 680€, a ns2r square 205 setup costs 250€. I prefer a worse tire and get more seat time.

pic of ar-1 rear tyre wear after 10h track time with -3.4º camber:


Photo of the car and some onboard action for those interested:

Gee Emm

Geeze that thing is loose in that first vid, not so bad in the second. Is that engine/gearbox heavier than original, or is it just overpowering the rear tyres? Fighting that will be costing you time, and the sliding won't be helping tyre wear. Crappy tyres won't be helping your rear end to stick either, there is a vicious circle there. In general, if it were my car I'd be looking at serious shock absorber tuning (my BCs were too stiff and wouldn't allow the rear end to work, they were moved on fast), springs and bushes - I hesitate to say more than look around for people making those cars go fast, and see what they are doing.

I haven't driven on the R888s for ages, currently finishing off a set of 215 AO50s (mediums),. I reckon I was getting about 8 events from the AO50s, and they hold their pace well. Bloody expensive here, but cheap performance if you follow. I don't know how the AO52s compare, but if your priority is seat time just buy the cheapest and thrash them to death. Note that the tyres you mention range from soft street to soft(ish) track tyres - the speed of that car suggests to me that R-specs would be the minimum, and you just have to swallow the cost - cheaping out on tyres is just going to cost you elsewhere, up to and including putting it in fence. On that same note, your personal safety gear could do with an upgrade too ...

If you are on a tight budget, you are going to have to prioritise tyres, suspension work and your safety gear, I know what I would do, but I am not you.

The photo above looks like you are running too much pressure, wearing in the centre, no obvious sign of camber/toe issues, though the scrubbed shoulder might suggest a bit more camber - but that is probably just the loose rear end. Given the car behaviour I'm thinking they are standing up well.

sixshooter

iTrader: (12)

I think the tire wear looks pretty even.

Hard, uncompliant shocks will make the tire bounce across uneven surfaces instead of remaining in contact.

ivan_b28

yeah it's pretty loose, asphalt in that track is ruined, and its also bumpy which my bc coilovers cant deal with properly. the engine/gearbox is not heavier than original, but its got 50hp more. I'm running 192hp na at high rpm, i dont think tires on that vid were overpowered (225 nankang ar1), im sure its a shock issue.

anyways, main reason i do trackdays is for pure fun and extracting the most out of what i have, and if what i currently have is cheap tires and shocks then so be it, ill try my best with that and have fun.

unfortunately buying better coilovers is not an option since budget doesn't allow it (monthly income isn't that big here! hahah). most i can do is finding someone who would do a proper revalve, or try with softer springs in order to run less shock stiffness (atm i have to run them stiff, otherwise rebound wouldnt control the springs and i'd bounce everywhere, the issue with this is that bump also goes stiffer, which you dont want in these situations).

i must say i disagree a lot with this: "cheaping out on tyres is just going to cost you elsewhere, up to and including putting it in fence"
losing control on an R compound is less predictable, and in the event of an accident you'll be going at a higher speed. with less grippy tires theres more time to think and if you spin out you'll be going slower than you'd be with grippier tires. it's also more fun to be on the edge personally.
i also dont tow the car to the track, it's street driven, so most grip available in this situation would be provided by nankang ar1 or a052, there's nothing more in UE market (no hoosier for example or toyo RR).
I agree with my personal safety gear though, but bear in mind that modifying cars in spain is way harder than in the US (too many legal problems)

Gee Emm

Good points.

Dual-duty is a set of compromises, by necessity. I understand your restrictions, my car is dual duty and we have similar here, compounded by annual checks of the car for rego. If your fun is catching slides, so be it, cheap tyres and stiff shocks are going to deliver that. Regarding rebuilding BCs to tame them, I can't remember if I looked into it or just bailed and went with something I knew worked, but I'd suggest being careful about who you trust to rebuild them, and not being the pioneer. Problem is that all(?) shocks at 'affordable' price level are single adjustable, you can't adjust bounce and rebound separately leading to the issue you describe, so you are going to be stuck with that fixed ratio in any revalving of the BCs. Before you spend money on the BCs, you need to assure yourself it will get you a better result than what you are dealing with now.

The AR1s are (were?) popular here, fast, cheapish, and held their performance well, almost as well as the Yokis - what killed them in the higher level competitions was that they were marked with 'for racing pruposes' (or something similar), therefore treated as full racing tyres. The AO50s R888s etc are DOT tyres and acceptable in competitions requiring 'street tyres', even though they are race construction/compounds essentially street legal race tyres. If you can run them, the AR1s would be a good choice.

I hope you keep us updated on how you go developing the car, it is a bit outside the usual box here but more interesting for that!

ETA: Please keep posting those videos!

emilio700

iTrader: (3)

Everything comes down to tire temps, regardless of tread to wheel width ratio.

https://www.949racing.com/supermiata...ire-pyrometer/

HTH

ivan_b28

@Gee Emm
dual duty has its difficulties as you say hahah.
what you mention about the bc’s having the same issue after a revalve might be true tbh… Idk if I should just go a bit lower on spring rates, tried them before but not on this bumpy track, that’s why I switched to the ones I have now which give me the balance I like (tried 6/10, 6,8 and 8/10 which I have now, with different rear sway bar combinations, now it’s deleted btw).

where are you from? Ar1s are not considered cheapish here, they are they go to tire for people with good budgets hahah. How much do they cost in 225/45 r15 over there? And the other brands? Here it’s 177€ for one of them.

i upload videos after every track day so don’t worry hahaha, glad you liked them.

ivan_b28

this is so many info, gonna need a calm afternoon and paper and pen to take notes if I want to try anything like this.

There’s something that puts me off about doing these kind of things in track days though, and it’s that I only do around 5 to 7 per year, so idk if it would be worth it to do considering the lack of consistency. If I could do a track day per month then it would be a different story.

by the way, I wasn’t really asking for optimal tire pressures, I was asking what pressure is dangerous when it comes to debead risk. I’ve heard that anything under 28 psi starts to be concerning, so I though that it would be even worse with a stretched tire. Does this make any sense or it’s safe to go lower? Where would the limit be?

Gee Emm

Its in my profile, I'm in Australia, car is registered in NSW and we have annual rego checks before renewal. many restrictions on modifications, but if you can find a friendly rego inspection station you can get away with a lot, just don'r rub their noses in it.

I never priced AR1s, but they were popular amongst a certain constituency - I was prepared to throw money at the AO50s to get an edge. Things may be different next time though.

rascal

Last time I looked, AR1s were around AUD$250 per tyre, A050s are around AUD$400 per tyre for similar size..

Nitto NT01s used to be a great value tyre, $170 per corner and consistent all the way to the cords. But A050s are almost 2 seconds quicker per lap now which is hard to overcome.

highroller101

My local club owner runs in the scca pro series and several other televised championship series. Last year the club members asked for a brief class on setup, the hot topic was tire pressure and I learned something that I’ve used ever since with fantastic results. Best place to start with tire tuning is 1psi/100lbs of car weight. And it works for weight split as well. For example Miata is almost neutral and my car weighs 1951. So I set my tires cold at 19psi. I tune balance from there. My dad runs a Porsche 911, 30/70 split, 2200lbs he runs cold (22baseline X (.3/.5) (bias difference from neutral) 14/31 (22x(.7/.5))
this has worked out great for us as starting points. You should expect 6-8psi growth if you are a decent driver.
as far as stretch goes - if you ever watched the force required to break a bead once seated, I think you would rest easy.
fwiw, I race a 1375 lb bugeye sprite, I shoot for 24psi hot, 16/15psi cold. On bias ply tires.