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Discussion Starter · #1 ·
Background on what I am trying to accomplish: I have done a couple autocross events with my MR2 since getting it late last year and I am at a point now where I understand the car and need grip to get faster! I did a little searching on here but saw so many varying responses for tire sizing that I wanted to put this out and just ask for people's recent experiences with fitment. Hopefully since this is a handling "upgrade" this forum is appropriate...

On to my question:
I am going to be keeping the stock wheels on my 2000 model. I believe these are 15x6 in the front and 15x6.5 in the rear. They have stock sized tires on at the moment I believe (how I purchased it) with 185/55R15 in the front and 205/50R15 in the rear. Good autocross tires do not come small enough to match that front stock sizing, so I am needing to squeeze a size or two larger on there. In doing that, to keep the stagger setup in proportion, I assume I should be stepping up the rear width with it as well (but maybe I am mistaken?). So does anyone have any experience and recommendations for sizing for this? The car will remain stock and I don't want any rubbing up front at full-lock while running a course.

I am specifically looking at Yokohama A052's or Falken RT660's. It looks like I can get the A052's in 195/55R15 or in 195/50R15 for the front but the RT660's would need to move up to 205/50R15's it seems to hit their minimum sizing that might squeeze onto that wheel.

Any thoughts or advice for me on getting good fitment on either of these? How would you size out the rears to match upsizing the front? Any other options that maybe I have overlooked? (no, I am not getting new wheels at the moment).

Thanks in advance!
 

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Discussion Starter · #5 ·
I've heard good things about the Dunlop Direzza ZIII. And I believe they are available in 195/50r15 front and 205/50r15 rear.
Thanks! I checked into those as well, my car actually was sold to me with the ZII's on the rear. The general advice for tires in the autocross world is that the ZIII's are too old and not competitive any longer unfortunately. The last car I was running at autocross had RE71R's on it and it seems like the RT660's are basically the same tire and preferred for most heavier cars. The A052's seem to be favorite amongst the light car crowd (Miata's) as they get heat in them very quickly and just grip after that. I do understand that I will probably burn through 2-3 rear sets of those for every front set, based on what I have read at least. So that's fun... :LOL:
 

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Discussion Starter · #6 ·
In case anyone is interested, and as a "bonus" for potentially helping me out... here's a video from my last event of my quickest run through my crummy dashcam (audio sucks). It was all I could do to keep this thing under control, the 740tw Yokohama tires on the front and the Direzza ZII's on the rear have almost zero grip when pushed to limits like this so it's a fine balancing act, even at only around 21psi in the rear on this run...
 

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Discussion Starter · #8 ·
If it's a 1ZZ car just go with the A052 in 195/50 all around. If you like a bit more grip in the rear or have more power go to the 205/50 rear it'll fit just fine.
Thanks for the reply! Yes, it's just a stock 1ZZ. It sounds like you'd suggest the 195/50's then for the front, and not the 195/55's? I assume the extra sidewall on the 195/55 would not have any positive effects then? I definitely want to stick with at least the 205's in the rear's, but if I step up 1 width size in the front should I also step up 1 width in the rear, just to keep things "balanced"?
 

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As it's a really short autocross, pre-heating the tires will help the most. If you buy 195 wide, buy one with "50" on sidewall, not 55. Smaller it is, quicker direction skipping it will be. Refreshed suspensions will help too. In all case, you will hit the stock car's limits.
 

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Discussion Starter · #12 ·
As it's a really short autocross, pre-heating the tires will help the most. If you buy 195 wide, buy one with "50" on sidewall, not 55. Smaller it is, quicker direction skipping it will be. Refreshed suspensions will help too. In all case, you will hit the stock car's limits.
Great, thanks so much! I assumed the shorter sidewall would be better based on what I had seen too. So far the suspension seems "good enough" and the grip was the main problem at-hand. Once I have the grip sorted out I am sure I will find other faults that need attention, as you mentioned :LOL: On my last autocross car I fell deep into the STX category, "correcting" one thing after another and upgrading and upgrading... so I am trying to be "good" and dial things back a bit and stay in Street for now (y) Once I put the RE71R's on there I started breaking things, so grip will definitely show faults! If I upgrade beyond Street in even just one part then I have to go all-in to keep up. Heck, I just paid more for rubber brake hose replacements than I probably could have spent on stainless braided hoses, all just to stay in Street :rolleyes: gotta love SCCA rules... but yeah, I did all the normal maintenance things to make it reliable enough (plugs, fluids, etc.) and upgraded the pads to EBC Greenstuff with just some O'Reilly's blank rotors, and new EBC DOT4 fluid for now, and what a crazy diffference that made for braking! This car is pretty impressive with just some refreshed stock\stock+ parts really! The stock 1ZZ has plenty of power on these short autocross courses too, and I had more than double the horsepower in my last autocross vehicle and still feel that way! Also, I have another Spyder at these events that is in a 1ZZ with a turbo and good tires and I am so far at least keeping up... after 2 events we are 1:1 and just tenths of a second off of each other. I figure if I get some good rubber I can outrun him ;) I need to offer a car swap at the next event to see what we run in each other's cars...
 

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... if I step up 1 width size in the front should I also step up 1 width in the rear, just to keep things "balanced"?
The stagger is to keep the car stable. That is maybe not a concern for autocross, because you are not going in a straight line for very long, and not reaching very high speeds. If you are doing performance driving on the street, the OE stagger is a good idea. You don't want to spin the car on a public road.
 

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Discussion Starter · #14 ·
The stagger is to keep the car stable. That is maybe not a concern for autocross, because you are not going in a straight line for very long, and not reaching very high speeds. If you are doing performance driving on the street, the OE stagger is a good idea. You don't want to spin the car on a public road.
Thanks! That was my assumption on the stagger from what I had been reading too, nice to get confirmation! I think I'd want to keep it then because I do plan to drive this car to the events and also on some back roads for fun on occasion and I don't need to end up in a ditch ;)
 

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Discussion Starter · #15 ·
A new question that has come to me to ask based on these other answers: Does anyone have experience with a tire size being put on the front stock wheels that rubbed when turning or hitting bumps? (assuming stock suspension and ride height, etc.)
 

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You'd need to go a lot larger than 195/50 on the front for it to rub especially at stock ride height. Also if your plan is to stay in street class I believe you can run a sing adjustable antiroll bar. So you could do a rear bar and then use the adjustment to fine tune the balance with the staggered setup. Even adjust at the track for more lively handling during autox only.
 

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Discussion Starter · #17 ·
You'd need to go a lot larger than 195/50 on the front for it to rub especially at stock ride height. Also if your plan is to stay in street class I believe you can run a sing adjustable antiroll bar. So you could do a rear bar and then use the adjustment to fine tune the balance with the staggered setup. Even adjust at the track for more lively handling during autox only.
Thanks so much for the advice! I hadn't considered an adjustable rear bar actually... I was planning to stick a larger one on the front eventually but I like your idea, that makes a lot of sense (y)

I think I'll end up with the 195/50's on the front then and just keep the 205/50 sizing on the rear for now. Depending on how that feels I can always up the rears to 215's at some point after I burn through this initial set. I really do appreciate everyone's advice and input! I feel a lot better about placing the order now!
 

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Ok, so auto-crossing and then club racing (Merlyn MK11, C production Europa) … a few years ago in the 1970’s I had an understanding of tuning suspensions that said tighten up the roll resistance (more swaybar) on the end of the car you want to come around (more yaw), opposite of the end you want to stick better. Then I read up on a number posts on this forum by experienced MR2 autocrossers in stock class (allowing 1 swaybar upgrade only) saying beef up the front bar despite the fact it understeers bone stock already. Rationale being the front struts wont move enough to offset front body roll tire pickup even with high static camber so you have to take out the roll to keep the tires flat; and, yes it will push worse but stick better at higher cornering speed so just drive it that way. Seems strange but???
 
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