I picked up a set of 205/50-15 BFG R1s for a pretty good price. The TT class I'll be running in limits me to that width for that kind of compound. BFG recommends that size tire be mounted on a 5.5-7.5" wheel, and I had them put on my 8" wheels, thinking they wouldn't be great, but should work. I've seen a number of other 205 tires on 8" wheels (old Azenis) and they fit fine, despite falling outside the recommended wheel width.

WELL. They are kind of stretched looking. To quote Sander, "I'm not gonna lie. They'll work for drifting."

I have a set of heavier, uglier, stupider wheels that are 6.5" wide that apparently will fit them better, but I'd really rather use the 8" if possible to keep weight down.

Pic courtesy of Sander:


And the BFG spec page: http://www.bfgoodrichtires.com/specs...e-r1/3824.html

And for comparison's sake, Hoosier's R6 spec page: http://www.tirerack.com/tires/Spec.j...irePageLocQty=

They look similar enough by the numbers that I assumed it would work. It is a monstrous difference in actuality. Different tire bead construction or something? Hell if I know...

 

For street use, I'd consider stepping outside of the manufacturers recommendations a minor risk, due to the inherent nature of legally mandated safety margins.

For a race tire, intended to be used under race conditions, I can't image going outside of the manufacturer's listed wheel width as a good idea.

Perhaps it's time to simply buy some new wheels?

 

coming from a autox stand point, i don't see why this would hurt for racing. wouldn't this help in actuality? think about side wall flex? you technically would have less, right? wouldn't have to worry about your side walls rolling over. plus, wouldn't you be running less air?

 

call emilio at 949 he will tell you that this is the only way to go. and i believe him as the turn in response is way better and you are getting full width out of that tire.

 

to quote emilio from another forum in regards to tire stretch...

"The change to contact patch area for a given static load is a minor effect if you're only changing say, 1". The benefit is that the casing is better supported by a wider wheel and will achieve more even loading of contact patch surface area. If you are making a huge wheel width change, say 225 on a 6" to 9" wheel, then yes, the static contact patch is greater with the wider wheel. Of note, the patch shape changes, becoming wider which itself, improves lateral acceleration for a given total surface area.

Lateral acceleration is only produced when one or both sidewalls are under tension. You turn the wheel, the contact patch lags behind as the sidewall winds up and tensions. With a wheel tire combo that allows the casing to roll back and forth or the tread area to twist relative to the wheel centerline, you have some lag time before there is a change in the vehicle's lateral acceleration. Widen the wheel to the point that both inner and outer sidewalls are always in optimum tension and you reduce the time needed for any steering input to effect a change in lateral acceleration. So quicker and more linear response turning in, making corrections mid turn, throttle inputs, etc.

The greater air volume from using a wider wheel allows lower air pressure to carry a given load. This lower air pressure allows the tread and sidewall to more easily conform to irregularities in the pavement, which increases grip.
The spring rate of the tire is also slightly lowered. This lower tire spring rate can be good or bad, depending if the tuner has compensated for it with in tuning everything else. The combination of spring rate and more deformable casing can allow a properly tuned suspension to reduce contact patch load area variation. That's the tiny little fluctuations in loading on any given part of the contact patch. Ideally, you want the contact patch loading always right at optimum to achieve maximum grip. In exaggerated terms, that's skipping across the pavement or smoothly rolling/sliding."

 

no problem with that at all.

 

Tire manufacturers produce specs for wheel widths on which each model and size tire they make is approved for mounting. The reason they do this is that, when mounted on a tire whose width is outside this range (wider or narrower), excessive heat and stress can build up in the sidewalls, and this can lead to things like popping the bead, tire failure, etc. (Incidentally, this is why we don't allow posts about using tires on unapproved widths in the Wheel and Tire forum, where most posters are less knowledgeable about risks than the racers are here.)

Obviously, it's up to you to understand this information and decide whether or not you want to use an unapproved tire width. You'll want to take into account the upsides (being able to use wheels or tires you have sitting around, or saving a few bucks on a different tire size, and possibly - but possibly not - turning faster times) and downsides (the possibility of tire failure and its consequences in lost track time and/or not finishing, possibly going off the track with results that may be catastrophic on a racetrack but no big deal in autocross).

Personally, I prefer to play it safe, and not use tires on wheels with unapproved rim widths. For me, the downsides outweigh the upsides. Besides, I wouldn't want something to happen and then be left thinking to myself, "this happened because I did something really stupid and it's my own damn fault". But that's what I do with MY car. You can do what you want with YOUR car. Within any rules for your events and competition series, of course.

I also don't buy into the whole concept of "my buddy tried it and he didn't have problems so therefore it's okay to do". There are too many variables, and one of them is chance/luck. Let's say that there is a 10 percent chance of a tire popping the bead if you run a certain fitment. Most drivers won't pop the bead - but do you really want to run a 10 percent chance of doing so? Especially in a high-speed racetrack event? I sure wouldn't.

It's like this with a lot of risks we evaluate in track driving. Many of them have to do with the car - whether we have enough brake pad thickness, too many brake rotor cracks, safety equipment, etc. There are other risk factors, too - weather, fatigue, etc. And even if you play it safe on all of those other risks, all you need to do is to take one corner early, and overcorrect when you run out of room at the exit, and you can still get into plenty of trouble.

 

No problem. In racing world, usually you are regulated by the rulebook on what wheel width you can run.

However, if you are not regulated by the rule, run as wide wheels as you can get away with. Usually the wider the better up to a certain point. It will give you wider contact patch and less sidewall flex side to side. Just pay a lot of attention on the possibility of the sidewall touching asphalt.

 

wow good info .

 

If you decide to use it (which I think you should) report back on how it goes. I am thinking of running some very slight stretch and stepping slightly outside manufacturers recommendations with both street tyres and some R comps and I would be interested to see how yours perform.

 

I've been running Hoosier 225s on my 6" wide rims for several years now and pretty much all the front running drivers are doing the same (at least for most tracks). Also, if you measure the Hoosier 225s they are wider than most other tire manufacturer's version of a 225 tire.

You'll have absolutely no problem.

 

this TT bit seems like way more headache than its worth

 

Adam, keep in mind that stretching a tire would make it more likely to roll on the sidewall. Remember the good old trick that we use shoe polish on the sidewall to see if it rolled and touched the pavement? With a stretched tire it would more likely happen.

But in your case, you're only 0.5" over the range that might not be too bad. Just make sure you keep an eye on it and maybe go back to the shoe polish trick if you ever experienced any weird snapped under/oversteer.

 

I would like to point out, this comment was made in a sarcastic fashion. Thank you.

And, Personally I agree with Wai, I would be concerned more about sidewall contact to the ground, or "de-mounting" which has happened to me (not in a stretched tire scenario), and it was very scary.

 

Tell me about it

powerneedy, Ken is just expressing concern over a valid safety issue. While a lot of people (myself clearly included) do get a bit grey with the manufacturer recommendations, they are present for a reason, however odd the chance might be of failure occurring. When we've seen drift guys in here with 195 tires on a 10" wide wheel or whatever, they get **** for it. This is the same concept, but to a lesser degree. While I already understood all of what Ken said, I'm glad that he's there to at the very least inform noobs who may not know any better.

Wai, thanks for that suggestion, I'll make sure to do that.

All that being said, I am going to try it and see how it goes. At the very least, we'll have some solid data. At the very worst, the world has one less Civic in it

 

 

Somebody better get rid of this thread before Ken sees it, or somebody's going to die.

 

Too late. On both counts.

(I posted above, you know...)

 

1/2" wider then spec'd by the manufacturer is WAY better then 1/2" narrower then spec'd by the manufacturer. On a slightly too wide wheel, the tire is going to operate at a lower temperature overall (less slip angle needed to generate same grip), can be run at a lower pressure, and will give you much better feedback. The only real caveat is that you need to be careful when jumping the curbs as you may be more prone to pinch flats.

Also, the tire would be stretched a fair bit on a 7.5" wide wheel too. You've only increased the stretch by 1/4" on both sides. Everyone has known for a long time that Hoosiers benefit from wheels .5" to 1" wider then Hoosier recommends as well, and a Hoosier on the max spec width wheel is noticeably stretched.

If you want the REALLY correct answer, call the tech guys at BFG (the ones with the racing program, NOT the passenger tire guys) and see what they have to say. My money says they'll tell you to go for it too.

 

Nate, don't suppose you have a contact number or anything for those guys? I poked around on the BFG website but didn't turn anything up beyond general contact info.