Tyre stagger (or not???), same tyres (or not)

[roger]

Just to add to discussion, I have a question that I don't remember seeing covered before.

You have 16" alloys on front, 17" on back.
If you get, on the Rear Toyo T1R Proxes - 215/40/17 (reinforced).
You then get, on the Front Toyo T1R Proxes - 195/50/16 (not reinforced).
(sizes don't necessarily go together and are just an example)

That 'reinforced' means the side walls are reinforced (i.e. stiffer)? You're buying the same tyre, brand and model... Surely though, the front and rear's won't be the same and what you're saying about being a mismatched make would cause a problem in this case (as I know people always saying on here Toyos are 'squidgy' - but I've not noticed mine being soft, which are reinforced)?

Unless somebody has a good answer - I guess this is an ideal question for Toyo technical support via their website.

[markiii]

strictly speaking you shouldn;t mix reinforced and non reinforced either

but then you get into the discussion about how much more weight is over the rears, so I tend to worry less about that

[ChrisGB]

Now before you mention it tread patteren only really comes into it when mother nature comes out to play.

Wrong. Tread pattern makes a difference to the working slip angle of a tyre wet or dry. It affects both the angle to which the tyre has to turn to produce a given turn radius, its resistance to loss of straight line and lateral traction and the distribution of contact patch forces. Oh, and the basic force per unit area.

Tyre compounds differ by either being soft or hard, the softer the compound the better the grip generated, but this come at a price as the tyre will not last as long. harder compounds work the oposite way, less grip but will last longer.

Wrong. Tyre compounds produce grip in two ways. Surface adhesion (chemical) and surface keying (mechanical). The softness of a compound will generally give an idea of adhesion and keying, but the nature of the compound can affect grip in several ways. Take two soft compounds, one carbon black filler, one fumed silica filler. To measure with a durometer they may be identical. However, the fumed silica filled tyre will be able to conform to the road surface more quickly increasing its level of keying without incurring as much wear. This increases wet grip over a significantly softer carbon black filled tyre compound. So if you put a carbon black filled tyre on the rear and harder silica filled on the front, you could get very wild oversteer when it rains.

It goes much further than this of course. Compounds will have different grip over different surfaces, so a tyre may make good grip on one surface, not so good on another. If the ones at the other end do not behave the same, then the situation is a recipe for problems wet or dry.

And further still, construction. One carcass may be completely different to the other, changing say rolling resistance or working slip angle of contact patch geometry. Add this to the compound and tread differences and only an idiot could claim that mixing tyres on any car is anything less than a dim thing to do. That many get away with it in their front drive mush boxes is lucky. Doing it on a mid engined sports car is asking for trouble.

now running different compounds front to back can cause grief or in some cases where the driver wants the back of the car to slide can prove to be benefical.

In drift club possibly, but for a road car?

in both of these cases tyre compound only has a noticeable effect when you put the car under pressure.

You may find you put your car under pressure when you don't think you have. It is easy on mismatched tyres to find yourself very sideways in any engine / driven wheels layout. In an MR2, this is a bad thing and being the best driver in the world will not save you. I watched Andy Walsh driving a 968 Clubsport on mismatched tyres on a wet handling day and he was unable to hold the rear end slide once it got going with a perfectly balanced car and the space of a whole airfield to play on. On public roads, the car would be lethal if it got away.

so to bring to close unless your a complete T**T and try to be michael schumacher on public roads then it is your fault for not taking peoples advice. however if you like your car then you will not be driving your car fast enough i.e. braking the speed limits then tyre compund has little to no effect. so dont worry about which manufacture you want to go with, unless your going to be doing a track day or the T**T. And in case  of the T**T you dont deserve the car.

It really does not take much to overstep the mark and find out the hard way. I have had a Ford Fiesta at 90 deg to the intended path on mismatched tyres and I was just pottering. All it needs is for the rears to be slipping a tiny percentage easier than the fronts to completely unbalance a car. Speed limits have nothing to do with it. Even the most conscientious of drivers will sometimes have the car moving about a little and this is not normally a problem, but on mismatched tyres on a mid engined car, it increases the risk of a little shimmy turning into an accident by a very significant factor. It also generally makes the car much less enjoyable to drive anyway, so ruining the whole point of having a car like the '2.

So to bring to a close, mixing tyres on the MR2 because a person was not aware of the potential for problems is unfortunate, but doing it knowing the possible outcome is just being a twat.

(I know I can say it because David Cameron said it on the radio  s:wink: :wink: s:wink:  )

Chris

[Anonymous]

Thanks Chris, excellent info and a very good read  s:wink: :wink: s:wink:  

Unfortunately there will always be owners/drivers of our fantastic car who just will not listen to those in the know,
or take heed from the vast amount of experience (when it comes to the MR2 roadster) from the members on this forum.

A sad fact but true.

[Anonymous]

Well, i notice rbuckingham has not responded to either myself or to those who have had far superior knowledge on the subject than myself and have been able to explain why you should never mix tyres.

Although rbuckingham is right about one thing, he is in his own words he is a t**t. that does not deserve the car.

[Wabbitkilla]

Maybe he's sharing his superiority on tw**ter?

Hopefully he's duly taken note and doing the right thing.

[SimonC_Here]

Maybe he's sharing his superiority on tw**ter?

Hopefully he's duly taken note and doing the right thing.

It would need 3 *'s to be a tweet!

[Anonymous]

So would I be correct in assuming that it is more dangerous to have mis-matched front/rear than it is to be running on 215-55-15s all round?  

And does anybody know where I can get a pair of 205 Bridgestones?  Or is it a case of biting the bullet and changing all 4 corners.

[markiii]

So would I be correct in assuming that it is more dangerous to have mis-matched front/rear than it is to be running on 215-55-15s all round?  

And does anybody know where I can get a pair of 205 Bridgestones?  Or is it a case of biting the bullet and changing all 4 corners.

nope both equally stupid

[Anonymous]

Thought so   s:roll: :roll: s:roll:

[uktotty]

i found the roadster handles better with the same tyre width on all four corners.


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[ChrisGB]

It gets complicated. With stock sizes on stock wheels, you get the manufacturers recommended stagger. If you upsize a little, you pinch the tyre at the rim a little, so a 225/45R16 on the read on a stock rim will not give you quite the 10mm extra width you expect as the rim is not the optimum width for the tyre. Combine this with an increase on the front to 195/50R15 where the rim is closer to optimum and you actually remove a little of the understeer, but not so much that the car is unstable.

Add in non stock wheel sizes and you are into a world of different possibilities. Very large diameter rims with a wide section could make the car more camber sensitive and it could end up running on the inner edges most of the time making predicting the handling complete guesswork.

Chris

[Anonymous]

That's it!  I've sourced a pair of REO40 Bridgestones for my back end.  
If I crash and burn now it's all your faults   s:lol: :lol: s:lol:    s:bounce: :bounce: s:bounce:  
Refer also to the 'Tyre' thread on 'Performance Related'.    s:scared: :scared: s:scared:

[Anonymous]

i dont even think i got a chance to read threads like these before mixed tyres (imo) raped my 2   s:cry: :cry: s:cry:

[loadswine]

Great shame mate. There are sadly quite a few of them now, some quite heated. The best way of approaching this is to try and absorb as much as you can before you become an actual owner, then you have a better chance. Not always the way things work out though. Sorry for the loss of your 2 though matey.

[AllanE]

Thought I'd give my two-penn'orth... Are you sitting comfortably?

It's easy to give out crass generalisations that can by ripped to shreds when it gets to the details, such as "DON'T USE MISMATCHED TYRES!"
What does "mismatched" mean?
I expect most will agree that "mismatched" means not of the same manufacturer, type and with no stagger.
OK, the common Toyo T1R has a different construction front to rear (sidewall reinforcement) - mismatched? No.
Another set of tyres with either a 10mm or 30mm 'stagger'?
Not necessarily - measure the actual contact patch on YOUR wheels, with YOUR suspension settings and YOUR pressures; the difference may be much higher or lower than the sizes suggest.

The grip is dependant on the coefficient of friction and force pushing the tyre to road:
Change the longitudinal or lateral G, you change the grip.
Change the compound, you change the grip.
Change the tyre or wheel size, you change the grip.
Change the temperature (ambient or tyre), you change the grip.
Change pressure(s), you change the grip.
Change the road (surface), you change the grip.
Change the weather, you change the grip.
Change toe or camber, you change the grip.
Whether you would even notice any of these changes will depend on your empathy with the car and your state of mind.

Tyres are not 'designed' for a car, they are developed and tested.

A few observations so far:

Nelix:
"On top of all that, a sharp eyed insurance valuator may notice that your set up is outside oem specs thus rendering your insurance null and void."
- Fortunately not in the UK, maybe in litigation-mad USA. Who even knows what OEM tolerances are?

"The percieved wisdom of the knowledgeable members of this forum and spyderchat in the states, both of which are dedicated to the roadster, is that you never mix tyres."
- Hmmm, perception to rule by a non-nominated spokesperson...

"Although rbuckingham is right about one thing, he is in his own words he is a t**t. that does not deserve the car. But of course, as a new owner with 28 posts, you know better."
- I have no problems with people attacking an opinion, but attacking the person is a bit off.
- How F****ing arrogant is it to slate a person because he/she is 'new' - He/she may be far better qualified to comment than you - don't do it - it devalues both you and your comments.
Just realised, by definition, I'm new!

"You do not know what you will encounter on any drive, weather conditions, road surfaces, emergencies that may require you to make sudden changes in speed, direction etc. So your argument that driving carefully and legally means that mixed tyres are ok, is piffle."
- Equally, you would not know that when something happens, when you were distracted, on a wet night on an unknown road that a "mismatch" in tyres would not be a benefit.

To assume a car had an accident because it had "mismatched" tyres is both naive and dangerous, just as stupid as the 'speed kills' slogan.

rbuckingham:
"everyone should do what they want not told!"
- Dead right! - Everyone should have the right to make their own decision, rightly or wrongly; I don't like blue cars, but I don't take exception to those that do!

"the tyre will grip until you put it past its elastic limit."
No - don't get lost in the detail.

roger
"If we believe this, why aren't we all running on remoulds at £10 a corner? as long as they are all the same."
- Because we can't get remoulds for £10 a corner? - I suspect you're missing the point.
I might have a great handling car with "mismatched" tyres - different manufacturers, same advertised sizes - the horror! - but they could be Kumho slicks on the front and Michelin on the rear that have a contact patch 20mm wider.
See? Missing the point.

Personally I prefer understeer - does that mean I like my car to slide it's front around every bend at 20mph in the dry?
No, it means that I prefer the front end to have less ultimate grip than the rear as I have more options in doing something about it, especially in a car with a low polar moment - generally higher limit, but when exceeded, more difficult to recover.
I can do this with mismatched tyres - I actually have "mismatched" tyres.
They are different manufacturers (from different continents), front to rear.
I have had the ABS working in the dry, on a smooth, straight, non-dusty road with warm tyres and understeer pushing round a roundabout.
I have had the rear fishtailing for a good hunderd yards on a cold, wet Sunday morning exiting a roundabout.
Hah! Mismatched tyres must be the cause!
What if the front  tyres had more, or less grip, would that have made a difference? I doubt it very much.
Am I happy with these tyres?
No, I think the rear Goodyears are crap, because they slide too easily in the wet.

Bottom line, I suppose, is that if you drive beyond any limits that are beyond you, the car or the conditions, something nasty is going to happen.
Even when changing to what you believe are identical tyres, recognise that a deeper tread and release compound have just changed one of those limits.

"Mismatched" tyres are just one (or four) of those limits.

[Anonymous]

rbuckingham:
"everyone should do what they want not told!"
- Dead right! - Everyone should have the right to make their own decision, rightly or wrongly;

Erm no, that is why we have laws.  s:roll: :roll: s:roll:  

Run mismatched tyres if you want.

[Wabbitkilla]

Matching tyres all round (with stagger) makes the vehicle behaviour more predictable ... end of.
Especially for someone who is unfamiliar with the vehicles handling and characteristics.

If you have got to the point where you are ultimately familiar with the handling of the car, then experiment.
If you are a professional racing driver and have the skill & experience required to "play" with mismatched tyres, then feel free to.
If you have money to throw away and want to then feel free to use mismatched tyres.
Just try it somewhere where you're not going to hit anything solid in all eather condition.

But....
You ARE less likely to have an upset of costly circumstances with matched tyres, if you hit me because you don't have any of the above i WILL brain you   s:wink: :wink: s:wink:

[Anonymous]

But....
You ARE less likely to have an upset of costly circumstances with matched tyres, if you hit me because you don't have any of the above i WILL brain you   s:wink: :wink: s:wink:

Good luck in finding an area to aim at Nic, will require pinpoint accuracy.  s:lol: :lol: s:lol:

[Jaik]

Stuff

You're juggling with fire. It's fairly safe if you know what you're doing, but you'd never recommend it to someone who doesn't.

The vast majority of people don't truly understand how various tyre combinations (compounds, sizes, pressures etc) will affect the handling and the easiest way to make sure they have a reasonably predictable and safe car is to make sure they have matched, staggered tyres with the right pressures. It's easy knowledge to pass on and covers the key areas where people could get it wrong.

[OlberJ]

Okay, staggered am sold on.

I've got 7.5J 16's and i'll be going 205 front and 225 rear.

What sidewall should i be going for, 45/50/55/60? It'll be the T1-R's for now. From the flexing point of view am thinking as low as possible?

[Jaik]

Generally you'll want to aim to keep the tyre circumference close to stock. Go here to compare stock tyre sizes with what you want to fit. The front and back may well be different.

[OlberJ]

Running off of 185 and 205 50/15's (early wheels and tyres) am gonna have to go for :

205/45/16 on fronts and 225/40/16's on the rear.

T1-R's work out about £240 all in which ain't too bad.

[ChrisGB]

The grip is dependant on the coefficient of friction and force pushing the tyre to road:

Change the longitudinal or lateral G, you change the grip.

You change the balance of lateral to longitudinal traction. It is the way a driver drives the car "on the throttle". Total grip remains similar.

Change the compound, you change the grip.

Very true. Change the compound so that one end of the car has a different one to the other and you change the grip level and slip angle required differently at each end.

Change the tyre or wheel size, you change the grip.

This is why aftermarket wheels or non OEM tyre sizes on a car like the MR2 require careful consideration and some trial and error to get right. I run 195/50R15 fronts and 225/45R16 rears and the understeer at the limit is reduced a little.

Change the temperature (ambient or tyre), you change the grip.

True and if your front / rear compounds and carcasses are different, they can change by different amounts for the same change in temperature.

Change pressure(s), you change the grip.

Which is why the manufacturer gives you pressure settings and you check them regularly. You specifically change the contact patch size and shape. Again, if carcass is different front to rear, pressure changes will have potential to change inconsistently.

Change the road (surface), you change the grip.

And if you have different tyres on front to rear, you may change the grip by different amounts front and rear, not necessarily the same way or by the same amount for each surface change
 

Change the weather, you change the grip.

And as before, by different amounts and at different rates at each end if front / rear tyres are different.

Change toe or camber, you change the grip.

Which is why manufacturers have a setup and tolerances.

Whether you would even notice any of these changes will depend on your empathy with the car and your state of mind.

And the severity of the reaction to the changes in the given conditions. I think many would not notice a little increase in wet understeer, or a little loss of stability under braking, but I reckon even the least observant driver would notice that they are sitting in a hedge when they expected to be driving along the road.

Personally I prefer understeer - does that mean I like my car to slide it's front around every bend at 20mph in the dry?
No, it means that I prefer the front end to have less ultimate grip than the rear as I have more options in doing something about it, especially in a car with a low polar moment - generally higher limit, but when exceeded, more difficult to recover.

The MR2 is set up for mild understeer if you have a set of matching tyres at the manufacturers recommended size and pressure. You can have more understeer by having less grip at the front or more at the rear if you want to introduce some or all those other variables you listed above.

I can do this with mismatched tyres - I actually have "mismatched" tyres.

I am sure you are finding the balance just fine and to your tastes, with your specific setup, but regardless, I would still strongly recommend to anyone with a finely balanced car that the matching of tyres and the correct stagger where specified, is a safer and better option than mixing tyres. Mixing tyres can lead to inconsistent balance of the car and at the very least, could ruin the OEM balance.

Also, although seen as safe, high speed understeer is a loss of control requiring correction, if this is needed, you have to be able to correct it. With the stock setup, correction of understeer at 70mph is relatively easy if you don't get off the gas too far. With more oversteer, perhaps you would need to be further off the gas still, introducing the possibility of a spin.

Want safe predictable handling over all surfaces at all speeds, match tyres. Want the potential for inconsistent balance and behaviour, mix tyres. Simples.

Chris

[Anonymous]

Nicely put Chris.