Okay, I got all setup for what I though was going to be an awesome ride heat-cycling my BFG Comp R1's today before my autocross this weekend, and instead, it almost turned into a horror show!

Help! I am not quite sure what might be wrong, through I'm leaning toward poor balancing.

My BFG's are 275/40/R18's. I forgot to get them heat cycled when I ordered them, so I was going to do it myself today. (drive 100mi or so, then let'm rest)

After getting them all on (and learning that, damn, after losing that 1" in tire height, I can't get the jack out from under the truck, lol, remeber boards next time!), I got all set to cruise on the nice-long-straightaway highways we've got around here for 50mi, then turn around and come back. Since NJ is like 90% asphalt as far as land space goes, the roads by me tend to be pretty good (they have this rotating paving period)... BUT, everything went to hell.

As soon as I got up to speed (60+) the handling went out the window and the truck became VERY unstable, it was trying to dart to the left, to the right, wiggling around a bit...It scared the sh*t out of me...It was so bad I thought maybe I forgot to tighten some lugnuts or something and a rim was about to fall off, so I pulled over, got out the torque wrench and gave everything a once over again, nope all tight.

Get back on the road, and again once I got to 55-60mph the truck was all darty again, I practically turned white-knucled from holding the steering wheel so tight...after ditching off of the nice 4-lane wide interstate (you can't do less then 70mph there without impededing traffic at night) to a smaller state highway, I finished off my cruise on a road where the speedlimit was 40-55...I didn't really feel any problems at those speeds.

So, what can be the cause of this? I strapped my Pirelli's back on when I got home and did some fast blasts...solid as a rock, so it ain't the truck or alignment.

Is it:

1. Bad speed balancing done by tire shop?
2. My inexpereince with this level of sticky tire and the effect slight road bumps have on them?
3. I am the proud owner of four new but bad BFG R1's?

I have the SmarTire pressure monitoring system installed on these wheels, it is a piece that straps on the rim. So that had to be accounted for when the wheels were balanced. (it works great too, cool little thing).

Help! Where should I look? Should I go find a real performance tire shop and get my wheels rebalanced? If I don't find out by Sat morning, I won't be racing this weekend.

Daniel

 

Daniel

I'm thinking # 2. Not much tread on the R1's, which is good for auto-x, but not for a good ride. What kinda pressure you running(40)? I've got the R1's in 295/35/18 and felt the same thing on the street, but they work good around the cones. I noticed this years ago when I went from DOT's in supersport to slicks in superbike. I don't think you will notice it at the track.

Mike

 

Pawn...something you can check. Jack the truck back up and put a jack stand in front of the tire about a 1/8" away from the tread. Spin the tire and see if the distance stays the same, if not the tires are out of round and need to be "trued" [some tire stores can true tires] or in your case replaced. Good Luck I forgot, the smart tire thing, I had them on my Vette, remember something about where they needed to be place on the rim. Like 180 degrees from the valve stem or something. Doubt if that's it but worth checking out.

 

That is called match mounting. When you buy a new tire there is a paint mark or 'dot' on the side wall. The tire installer is supposed to line up that 'dot' to the valve stem.

 

The SmarTire manual says it should be about 1" counterclockwise of the valve stem, which is where I put mine.

I'm really surprised that it would be the grip of the tires on the road that was giving me the feelings I had, at this point, I'd be nervous taking these out on a real road track with out they felt...of course AutoCross wouldn't be an issue, you rarely get near 60mph anyway...but anything high speed? gah, I would definately want a slow lap to try it at first.

KGM - I already have them dismounted, but, even though I'm not sure, I don't get the "feeling" that they roll well when I was putting them back into the garage, they just feel wobbly, but I'll have to check again this afternoon after work.

Also, they are the BGF gForce T/A R1's, not comp's, I was tired.

I was really surprised at how bad the handling felt, I thought it would be a tight gripping rocket ride, since these are "road race" tires...

I also have not had a seperate alignment done yet...the treadwear on my F1's and my Pirelli's has always been even and the truck felt solid, so I havn't gotten it aligned yet...so I don't have a cam-bolt setup yet or anything (still have the OEM-plates).

Daniel

 

99 SVT...I was talking about his SmarTire things. Pawn try to find a tire shop that can balance on the truck. Much better way to go.

 

Pawn
I use those tires for road racing, and at 125 mph they are as steady as a rock. And this is at Nelson Ledges which may be the least smooth track in the country. One time when I was putting the BFGs on my truck I noticed a small wheel balancing tab had fallen off. The tires still didn't give me any problems even though one was a little out of balance (based on the missing balancing tab). I don't know what your problem is, but I don't think its your inexperience with road race tires. It could be the balancing, but I',m guessing bad tires. Are you sure your wheels are good?
Tom

 

I laughed when I read your post not because it was funny but because I had the same problem yesterday at the track. But mine got squirely at about 110 mph.

Although there could be other causes. Investigate ALL of them - mine are balanced and have been tested on other tracks, so I had less variables to deal with.

1. Crank up the front shock setting to 11.
2. Check your tire pressures. Although they specify 44 psi max, I set mine to 32.5 psi at Laguna Seca (mounted tire pressures, out of the sun on a warm day), and I had excellent grip and no problems. Yesterday, I set the pressure to 40 psi, same conditions and the grip was horrible and the front end jumped all over the placed at 110+. After 2 sessions and mulitple pit stops to air down the tires, I ended up with a cold, mounted tire pressure of 34.5 front, 34 rear. The hot tire pressure ends up between 40.5 and 43 depending on the tire. For instance, the front passenger was 43, front driver 42.5, rears 40.5.

3. The track was also repaved last month and did cause some this and the suspension setup and tires will give feedback that you normally don't feel.

Regarding the pressures, you will probably want to do the autoX with them higher because you won't have the opportunity to heat them up like I do my first two or three laps (about 5 - 9 miles). The best way to check the tire pressure is to buy a temperature reading gun from summit for about $80. After running the tires, check the temperature across the tire. If the pressures are correct, the temp will be even across the surface.

Hope this helps!

Regarding the pressures, what do the rest of you guys run them at?

Spike

 

The SmarTire system showed my pressure to be even across all four (42lbs, except front right was 41lbs). ... I didn't try dropping the pressure to see how they handled... Cold, they're about 40lbs... While running, it showed ambient tire temp of 66-67 degrees in the front and 74-77 in the rear (when doing straight-aways).

I guess I've got a bunch of things to check out. I need to find a tire place near me that has one of those HAL Roadmaster thinigies, have them check if my tires are round...and I guess I should finally go get an alignment and a cambolt kit... The stock plates have held the tires well so far, but it can be out of spec a little that would show up on those tires.

I do like how sticky they are though. I -thought- I picked a highway that would be mostly smooth (though it is a truck route) because its paved alot, but then again, it isn't a race track. lol...

Daniel

 

I run mine at 34 lbs. I haven't experimented around with the pressure because I never had a traction problem at 34 lbs, so I thought, why change it?

 

Pawn:
See Care & Feeding of the BFG's...R1 . The key sentence is "The g-Force T/A R1 will work well on most cars with inflation pressures between 40 and 45 psi ("cold" inflation pressures for autocross use and "hot" inflation pressures for racing use).

Tom:
32 - 34.5 psi is about the best range I've found. And as you pointed out, why change it! I can now say that 36 psi is too much!

Spike

 

Spike, yeah, thats where I was at, 40ish cold, 42 driving.

Daniel

 

Don't take this wrong because I'm not doubting you, but a 2 psi rise doesn't seem correct. It could rise 2 psi just by sitting in the sun, let alone heating them up on the road. Mine rose 6 psi on one slow warm-up lap, and more after that.

Spike

 

Mmm, dunno what to tell ya... I was only doing between 40-50mph, and there were traffic lights, so it wasn't a straight higher speed run...maybe I didn't make enough heat to raise it more?

Daniel

 

Just a thought:
Send me an email at george@spikeengineering.com and I'll send back my cell phone number. Maybe a quick conversation will help.

Spike