BF Goodrich R1 size question

[paradocs98]

My Nitto NT01s are pretty much done at this point, and I'm thinking of trying the BF Goodrich R1 for next track season. I had been using a Nitto 275/35-18 square setup on my dedicated 18x10" track wheels, but I see that a lot of people who run the BFG R1 do a staggered 265/35-18 and 285/30-18 setup instead of 275/35-18 square.

mastek tells me he thinks the main advantage of a square setup is the ability to rotate tires and increase useful tread life. I've certainly heard this argument before, but I'm curious as to why Turner Motorsport recommends the 275/35-18 square setup on their site instead of the staggered fitment others are using. I like the idea of a fatter front for turn-in and braking, but I do have some concerns about the BFG R1's front fitment in a 275 on our cars. While the specs on the Nitto and BFG websites show an identical section width of 10.9" for a 275/35-18 on a 9.5" wheel, others have posted pictures here showing how much wider the BFG runs compared to Nittos and other brands. Has anyone here tried the BFG R1 in a 275/35-18 square setup? Any other thoughts either way?

Thanks in advance, and thanks for your comments, mastek.

[Richbot]

Bigger front tires don't really help braking and turn-in, they actually hurt it some, but they do help mid-corner and track-out grip. A wider contact patch doesn't change lateral direction as easily as a narrower one. Similarly, a contact patch with a "longer" shape tends to resist longitudinal forces better. Like everything there's no free lunch and the tradeoff for more grip in the corner is a little less steering response and a little worse braking grip. It seems counterintuitive but when you change the tire size all you're really changing is the shape of the contact patch, assuming you're running roughly the same tire pressure and dynamic corner weights don't change drastically. Some cars like ours need it, some cars like 911's and whatnot don't because they don't carry much weight up there. No reason you can't run a 275 with a much wider rear, there's room. The only worthwhile reason for running a square setup IMO is tire rotation and it's not a bad reason at all, but I think it sacrifices some performance against, say, a 285/315 or 275/295 setup if you compensate for the balance changes.

In any case, the only way to go faster is getting the balance right for each individual setup and then finding out which one the stopwatch says is better. IMO One of the reasons square setups are so popular is because this car and BMW's in general tend to understeer with the stock setup so you bolt on more neutral balance when you bolt on a square setup.

To answer your question, I think you'd be happy with the staggered R1's as long as you compensate for the balance changes. They're going to be quite a bit grippier which will add to the sensation of a "tight" setup.

If it were me I'd just run the 285/30-18's all around, the next size up is the 335/30-18 which is probably too big without some serious finagling. I'm going to do a fairly comprehensive study of Hoosier fitment in the rear of this thing this winter and I'll post my results, the purple crack is somewhat similar to the R1 in terms of fitment

[paradocs98]

Wow. Thanks for a very informative reply. I've run the square Nitto setup all season and have been happy with it. I ran my daily driver 255/275 Michelin Super Sport setup at Watkins Glen a couple of months ago when it was cool and foggy and it showed me just how much better the car handles on the track with the 275/35-18 NT01s. I had naturally assumed that the better feel of braking and turn-in with my track tires was due in large part to the wider front section width, but based on what you're saying regarding contact patch shape, the track tires are probably better mostly because of stickier compound/tread design.

The 285/30-18 BFG R1 square setup is an interesting thought--has anyone run that tire in that size on the front without rubbing issues?

[von_zoom]

This season I ran with a square set up, BFG R1s, 275/35/18 on APEX 18X10 rims. True to expectations, the car will understeer if push hard into a tight turn, so expect a slight opening of the wheel, or brush of the break to get the front to turn. Otherwise, I felt the car accepted the tires very well. They did begin to go away after six events, but will stick if you give them time to heat up.
vz

Edit, please change six events to six days, or 18 heat cycles.
vz

[Richbot]

Originally Posted by paradocs98

Wow. Thanks for a very informative reply. I've run the square Nitto setup all season and have been happy with it. I ran my daily driver 255/275 Michelin Super Sport setup at Watkins Glen a couple of months ago when it was cool and foggy and it showed me just how much better the car handles on the track with the 275/35-18 NT01s. I had naturally assumed that the better feel of braking and turn-in with my track tires was due in large part to the wider front section width, but based on what you're saying regarding contact patch shape, the track tires are probably better mostly because of stickier compound/tread design.

The 285/30-18 BFG R1 square setup is an interesting thought--has anyone run that tire in that size on the front without rubbing issues?

R tires, even relatively mild ones like the NT01's, are in a whole other league from the PSS. Easy to forget that it's an apples to kumquats comparison when you're driving the same car and it's suddenly worlds better after one change. The NT01's are probably a lot stiffer as well, I only have personal experience with the R888 (they're very similarly constructed, from the same parent company) and they were stiffer than any street tire I've used.

ShadyD1 is running the 285 Hoosier in a square setup but he wasn't able to tell me what his offsets were off the top of his head, maybe PM him?

[Merked M3]

Here are the largest front wheels/tires and tires I have seen (on the forum at least):

Originally Posted by wwjd15

ar: 11 E92

Wheels w/ Offsets: Volks TE37SL - (F) (R) 18x10.5 et20
Spacers: None
Tires / Miles: Hankook RS3 - (F) (R) 285/35/18; New Tires
Suspension: Moton CS with camber plates
EDC Setting: none
Alignment: (F) -2 (R) -1.6 camber 1/16" toe
Fender Modifications: (F) None (R) None
Rubbing?: none.

And that fits with no rubbing on a 285/35 RS3 vs a 285/30 R888 that will most likely be wider and more square than the RS3s, so they are probabbly quite similar in fitment.

I have a set of shaved 275/35/18 (classic size) RA-1s that I need to run through this season, and would like to do the same thing and upgrade to 285 for the next (front) tire.

[NRBRNG]

Originally Posted by von_zoom

This season I ran with a square set up, BFG R1s, 275/35/18 on APEX 18X10 rims. True to expectations, the car will understeer if push hard into a tight turn, so expect a slight opening of the wheel, or brush of the break to get the front to turn. Otherwise, I felt the car accepted the tires very well. They did begin to go away after six events, but will stick if you give them time to heat up.
vz

Edit, please change six events to six days, or 18 heat cycles.
vz

I also ran the BFG R1's this season. Slightly different set up due to needing the front clearance running Clubsports: APEX 18X9.5F and 10.5R with 265/35F and 285/30R. No rubbing, good turn in if the above two points are used. The grip has been fantastic for first 5 days (20 cycles), great for the last 2 days but times went down by 1-1.5 secs. I am quitting while ahead and ordering the same R1's for next year. Couldn't be happier. Now for brake ducts...MT

[von_zoom]

I will also be repeating with my set up next season, and will order BFG R1 275X35X18 soon (Christmas Gift). FYI should anyone be interested, I will sell my existing BFGs - $200 plus shipping. Will post pics etc later. PM if interested.
vz

[paradocs98]

Thanks for the replies, everyone. Very helpful. Spring can't come soon enough.

[CSBM5]

Here's a pic I took a few years back of a 265/35-18 R1 next to a 275/35-18 NT-01, both on 9.5" wheels. The 265 R1 was about equal to the section width of the 275 NT-01 when measured; however, the R1 sidewall to tread face profile is different from most all other tires out there. Note how it carries its section width out to the tread face while most tires have some curvature from maximum section width to the tread face.

I've used 275/35-18 R1s also (E39 M5), but they created some clearance issues where no other 275 R-comp I've used on that car ever did (Hoosier A6, NT-01).

Just an FYI post...sounds like the 275 R1 will clear ok on the M3.

Cheers,
Chuck

[paradocs98]

Thanks, Chuck. That picture really dramatically shows the difference in shoulder shape and how, despite the official numbers on the manufacturer websites, a 265 BFG R1 is the same section width as a 275 Nitto NT01.

[sawzall]

Factoring in regular rotation on a square set of BFG R1, how many track days would one be able to get out of a set?

I've been running NT05 and have about 5 track days on mine, with maybe 1-2 days left in them.

[von_zoom]

There are many factors which will determine when your tires are toast. Long tracks, like VIR, are kinder to heat cycles than a short track with many turns which require a lot of brakes. At VIR, with the E92, I try and change every 3 to 5 events mainly to have the best grip as soon as possible once on the track. After 5 events, if I would be patient, the tires will heat up, and in two or three laps will be gripping fine. I instruct, and mostly have students riding with me when on the track, and there fore want the best out of the tires as early as possilbe. Unless you run over something, I would think that it will take some time to ware them out - unalbe to estimate when that would be. I have seen them corded, but never experienced that.
vz

[turbo8765]

Originally Posted by Richbot

Bigger front tires don't really help braking

Can you recommend another source that would confirm this cause it's really, really hard to believe.

More contact patch=more grip. So you're saying that the larger tire deforms so much, and more than the smaller tire, that the net result is a smaller contact patch with the larger tire??

[Richbot]

It's counterintuitive and it's only true in an "all other things being equal" scenario, but it's true. In the real world, you more often than not get better performance and lower lap times with the wider tire. But it's important to understand how much of that is due to the width and how much is due to the zillion other things that influence how the tires interact with the pavement. Believe it or not. Start here http://insideracingtechnology.com/bookorder.htm

You need to read what I wrote again if you think that's what I'm saying

[HT1000]

Only objective testing can tell for a specific application.

[Richbot]

Originally Posted by HT1000

Only objective testing can tell for a specific application.

Ex-actly. You can geek out about it on the internet for weeks on end and never accomplish what you can with a few sets of wheels and tires, a stopwatch, and a few hours at a test day