So one of the things that happens with Hoosiers a lot is that the tire has more grip on the track than it does on the bead surface, meaning that it rotates a bit on the rim when in use. Here's a photo -- the arrow on the sidewall pointed at the valve stem when the tire was first mounted:
It happens most on the first or second heat cycle, and (surprisingly) more on the rears than on the fronts (tires have been rotated X-pattern in that photo, so it used to be on the left rear). They also move opposite directions at the two ends of the car, brakes vs throttle. Obviously this hurts the balance, in some cases by a lot. The set I was using at the track yesterday were really bad (after 4 heat cycles) -- there was a mobile tire guy there who rebalanced them for me, he said that one of them was 9 ounces out of balance before he took the old weights off.
One band-aid fix is to mount them with minimal amounts (ideally none) of tire lube, but finding shops willing to do that is hard and even if you do it still moves, just not as much. The newer Apex wheels have a knurled bead mounting surfaces which helps more, but they're not cheap and it doesn't fix the older sets I already own.
I have heard someone suggest sandblasting the bead mounting surface. Has anyone here done that? Does it work? I don't own a sand blaster or have space to store one -- any suggestions on what kind of shop to look for to do this kind of work?
Bead blasting will work for keeping the tires from spinning. On my last set of BBS three pieces they had blasted a textured surface which stopped the shifting dead. I was running a 19x15 with a 355 width around 800hp to the wheel.
Any chance it is when you are running lower pressures and its only shifting when cold, or only shifting when hot and the tire expands. Under load with aero?
buzzboy
UltraDork
8/26/24 5:55 p.m.
I know old drag racers would do rim screws but I guess that doesn't work with tubeless tires huh?
Many racing wheels have knurled beat seat areas to help with this issue. My Finspeeds do, as do my new 6ULS.
In reply to buzzboy :
I mounted a set of tires on braid rally wheels that had pointy ended screws with threads in the rim that when tightened poke into the bead. They're tubeless. Neat setup but i could see galvanic corrosion making the screws a bear if you don't put something on them. They call it their beadlock b system.
buzzboy said:
I know old drag racers would do rim screws but I guess that doesn't work with tubeless tires huh?
Drag racers still do it, at about 6 to 12 screws per bead surface. You can buy drill guides from places like Summit.
It works just fine with tubeless tires, because the screws don't go all the way through the tire. They'd hole a tube if they did. But you HAVE to do it with tubes, because if the tire spins on the rim with a tube, you rip the valve stem out.
I knew some lazy racers who went tubeless on their drag slicks just to avoid the hassles of rim screws. Drag slicks are somewhat air-porous so this meant having to reinflate them every weekend.
Andy Hollis said:
Many racing wheels have knurled beat seat areas to help with this issue. My Finspeeds do, as do my new 6ULS.
The newer Apex forged ones do, but that's a lot of money to replace six sets of wheels. :)
wearymicrobe said:
Bead blasting will work for keeping the tires from spinning. On my last set of BBS three pieces they had blasted a textured surface which stopped the shifting dead. I was running a 19x15 with a 355 width around 800hp to the wheel.
Any chance it is when you are running lower pressures and its only shifting when cold, or only shifting when hot and the tire expands. Under load with aero?
They shift the most on the first heat cycle. That's when they have the most grip, but it's also a session that always starts cold (typically 22-24 psi, aiming for 31-32 hot). Later sessions it still moves, only not as much -- of the ~120 degrees in that photo above, probably 100-110 degrees on the first heat cycle with most of the rest on the second one. A typical race weekend is stickers for Saturday qualifying, and by Sunday race (4th heat cycle) they're shaking a lot. The car has aero, yes, although not crazy amounts of it (NASA ST4 car)
On your BBS did you do the bead blasting yourself, or was it something BBS did as a part of the manufacturing process?
Andy Hollis said:
Many racing wheels have knurled beat seat areas to help with this issue. My Finspeeds do, as do my new 6ULS.
And your FM Kogekis :)
Shouldn't be too hard to find someone in the local automotive community with a bead blaster to texture up the bead seat. Heck, you could probably do the same with some coarse sandpaper. I've done it on control arms to keep alignment cams from slipping as well.
Pete. (l33t FS) said:
Drag slicks are somewhat air-porous so this meant having to reinflate them every weekend.
Hoosier R7s are a bit like that too. :)
codrus (Forum Supporter) said:
wearymicrobe said:
Bead blasting will work for keeping the tires from spinning. On my last set of BBS three pieces they had blasted a textured surface which stopped the shifting dead. I was running a 19x15 with a 355 width around 800hp to the wheel.
Any chance it is when you are running lower pressures and its only shifting when cold, or only shifting when hot and the tire expands. Under load with aero?
They shift the most on the first heat cycle. That's when they have the most grip, but it's also a session that always starts cold (typically 22-24 psi, aiming for 31-32 hot). Later sessions it still moves, only not as much -- of the ~120 degrees in that photo above, probably 100-110 degrees on the first heat cycle with most of the rest on the second one. A typical race weekend is stickers for Saturday qualifying, and by Sunday race (4th heat cycle) they're shaking a lot. The car has aero, yes, although not crazy amounts of it (NASA ST4 car)
On your BBS did you do the bead blasting yourself, or was it something BBS did as a part of the manufacturing process?
When I had new barrels made it was an option and I selected it because it was recommended if I was going to mount slicks. I typically a "street" tire around 200 tw
In reply to Lof8 - Andy :
I'd wonder how the balance beads would work with all the G loads on the track. I'd think they would have a hard time settling into the right spot vs a commuter that is driving at a steady state most of the time.
