How wide is too wide?

[Smokey228]

Okay, so this thread has nothing to do at all with mens genitalia. lol

Rather, its been brought up a few times before all over the place, but it would be nice to see a thread with a definitive answer and a few reliable peoples opinions...

But what i want to know, when do wide tires start to reduce handling... Is a 7" wheel with 235s going to handle better in my RA23 than a 8" with 235's? Will same 7" handle better than a 8 with 245 or 255's?

I read in the classic celica thread, that one of the guys saw better handling with a 6.5" or 7" with 225s than they did in a 8" with same tires. In some ways that makes sense i spose. But If that 8" had a 235 or a 245 (if you can fit it) than have advantages in the same car?

I done a quick google and found this, its directed at bikes, but i assume in some instances, can work for cars too?

The wide rear and narrow front
tires are the biggest setup problem in racing. In any turn, the
front tire describes a larger diameter circle than the rear even if
they're both the same width. As you increase throttle exiting the
turn, the powered rear tire (pointing straight ahead) tries to push
the front toward the outside of the turn. The fact that the contact
patch is on the inside edge of the tire means that the wider the tire
you put on the back, the smaller the radius of that circle becomes
and the more the push problem is exacerbated.

I hope im going in the right direction and that this thread makes sense.
Appreciate anyone's help and hopefully this makes a good thread some day

Cheers,
Jase

[Stefan]

Sounds a little back to front to me - fat tyre on 8" rim should 'handle better' than a 7" - less sidewall flex from balooning tyre. Of course, this depends on the profile too....

[clubagreenie]

It's going to come down to individual tyres. Each one will "bag" differently when fitted and weighted. Anything with a softer sidewall (theoretically) will get hotter due to having more flex but this will make it expand (grow) more and (should) correspondingly flex less (but we know this doesn't necessarily happen).
You could say that ideally it should be stretched as this will pull the beads out and triangulate the sidewalls. But thats covered in another thread.
Each makers idea of sizes differs too. Best bet would be to measure the actual cross section of the tread area, have the rim section this wide. This will place the bead directly under the outer edges and make the sidewalls square.

[oldeskewltoy]

Anyone a Tire Engineer???

Yes it is VERY true a smaller sectional width can and sometimes WILL handle better than a larger one!!!
Reasoning is ALL ABOUT tire temps and getting tires to optimal tempuretures.
vehicle mass, suspension type, aero, intended speeds, (and many other variables too) ALL play into proper tire choice.

Without your specifics I can't say... but to give you a bit of an idea....
I run: 87 AE86... 4AGE/112whp, custom springs(4.5 frt rate 3.0 rear ), Illuminas - I use a 205/50/15 Recent tires I've had are(current to oldest):Kumho SPT, Yokahama ES100, Kumho 712, Bridgestone RE71.

All these tires are street... all are in the higher end (NOT the highest). I run 95% street with one or two track days a year(no drifting). I really enjoy carving up back mountain roads...... so tires ARE IMPORTANT.

[pisso001]

Yeah but what size wheels do you use with those tires... ^^^

[river]

Hi,

Tyres like most things are a compromise on grip, handling, flex, wear factor, etc. Also, what may be great for dry weather could be woeful on wet conditions.

A wider tyre is more prone to aquaplane than a tyre that is not so wide.... given all other conditions being equal.

Tyres are just one part.... albiet and important part... of the road-running gear of a vehicle. You will need to make sure you have a good suspension set-up, sway-bars etc or money spent in good tryes is not going to be money well spent.

seeyuzz
river

[Norbie]

IMO you'd be struggling to fit a tyre that's "too wide" in an RA23. I had 225's on the back of mine at one point, which is hardly massive, and from memory it was scraping the guards a bit.

While everyone says a wide tyre is more prone to aquaplaning, I've never had this problem even with 255's on my Supra - its roadholding in the wet is quite good. I suspect this has a lot more to do with the quality of the tyre than its width.

[rms]

An observation
While road tyres are going lower and lower in sidewall height ( I don't mean aspect ratio), race and road legal slicks are going the other way.

Shouldn't that make you wonder about 35/45 series tyres ?

[oldeskewltoy]

Yeah but what size wheels do you use with those tires... ^^^

Me?????

I use 15" Mark II Supra wheels -15x6 10 offset

[Stefan]

Me?????

I use 15" Mark II Supra wheels -15x6 10 offset

I believe those wheels are +20, not +10. All Mk2 Supra wheels have the same backspacing IIRC:

14x5.5 = +27
14x7.0 = +8
15x6.0= +20 ?

[lexsmaz]

If you are just driving around the street you will not notice a lot, BUT if you do any track work it is a biggie, years ago i ran a RX3 which was lowered, etc. got some 205 / 60 tyres but could not afford bigger rims at the time so ran from memory 5.5 '' rims with the tyres, took it around Winton, experienced a lot of understeer, increasing tyre pressure heaps didnt really help, ( i used to run up near 40 psi ) .. few months later went back to Winton same tyre now with a 7 '' rim a lot less understeer, & from memory picked up around 2 seconds a lap, NO other changes were done to the car ...

[oldeskewltoy]

I believe those wheels are +20, not +10. All Mk2 Supra wheels have the same backspacing IIRC:

14x5.5 = +27
14x7.0 = +8
15x6.0= +20 ?

I stand corrected... 20mm is the offset

[RObErT_RaTh]

I stand corrected... 20mm is the offset

Also they may look like the Mk2 supra pattern but I assure you they came from a soarer

[SillyCarS]

i had yokohama 760s on a 14x7.5" hotwire rim and it was sick

edit: wait i think thats from rim edge right over the top to the other rim edge, someone pls correct me i think im wrong



dont forget tyre pressure

another thing that im gunna have to do now cos of my brake upgrades is go to a larger rim, im looking into what widths we can get away with by stretching tyres onto rims

pro 16x8's and 16x9's with stretched tyres on them, particularly at the front. the 270 on the 7.5" rim only scrubbed a bit, so a 225 on an 8" should be ok

i think when the discussion is finished and when we have gone ahead with it we should all collate a wheel fitment page for classic celicas that includes diff widths, front brakes and etc.

there are a few examples i really like, like ogoor with the 17's, or grim boys with 18's (from memory) but i'll prob end up going with some of these 16's that are on special

http://www.otomoto.com.au/showroom.htm

[Soarer21]

An observation
While road tyres are going lower and lower in sidewall height ( I don't mean aspect ratio), race and road legal slicks are going the other way.

Shouldn't that make you wonder about 35/45 series tyres ?

Since when? Classes with controlled tyres have rules limiting the profiles they can run. Go check out the tyres used on cars in the BTCC or German... Most run 18 or 19n slicks with stuff-all sidewall.
Less sidewall, less flex. Less flex, easier it is to tune the suspension and get the cars to handle.


Now you've all taken this off topic. What the guy was asking was a given tyre width on a certain rim width. Not what aqua planes, or how big you can fit under a certain car.
Generally speaking, from my own experience I run a rim no less then 1in under the width of the tyre. That means 8in tyre (205) on a minimum 7in rim.
As an example of race combo's the V8's run a 280 width tyre on an 11in rim
My own race car I was running 265-625-17 on 10in, 300-640-17 on 12in and will be looking in the future at running a 330-680-18 on 13in

And all of which generally will mean nothing if you havent got the right alignment.
If you're car is running an alignment setting meant for stock wheels and you bolt some big wheels and tyres on it then it could well find some aspects of steering/handling are negatively affected. Unfortunately most guys will ALWAYS do things half-arsed. If you are going to fit decent size wheels and tyres, make sure the car is aligned to suit, and that DOES NOT mean to factory specs so the local tyrebarn is not the guy to see. Go find a genuine suspension specialist with race experience preferred and get them to make adjustments as they see fit and then try it. Every car is different, and doing it right will payoff in a nicer car to drive with improved handling