28x10.5 Tire

**Stephen Ertel** · 11-27-2012, 03:59 PM

Can we get a dialogue going on setting up a 28x10.5 tire, stiffwall Hoosier or those running tubes would be most helpful. Running best 60' with... LCA bottom hole, TA bottom hole, Pinion -2, Rear SA shock 7, Fronts 2-4, Tire PSI 11.25-11.5 HOT immediately after run, set 11ish before burnout depending on tire temps.

I cannot get this tire to hook at anything higher than 11.5. It turns the tire coming off the transbrake maybe 1/2 rotation as opposed to a dead hook when the 60' times are best, but going up to 12 it will slow down 1-2 hundredths, and lose another 2-3 going to 12.5. Video shows the initial hit is quite good, with a tendency to bounce at lower tire PSI when it really dead hooks. But more tire PSI results in immediate spin and a corresponding .5 mph gain on top. Is it as simple as getting a good DA shock in the rear so I can control the compression (bounce) while letting it really slam the tire with a loose rebound and being able to raise the tire psi into the 12-13 range where I know there is some ET/MPH lurking? I see this problem getting worse when I throw the direct port at it next year, planning on going up to 28 jets...

**BIG CAT** · 11-27-2012, 05:59 PM

ok. let get a little more info and see what we come up with.

what gear?
launch rpm? 2 step?
are you spraying it? at the hit? progressive controller?
weight?
what transmission?
tubes/no tubes?

also keep in mind dead hooking is not necessarily a good thing. when you start making a good amount of power you need the tire to slip a little or it will wad up and go into shake.

here is a clip from sgmp. it shook so bad the needle came off the speedo. i run 28x10.5w's. tire psi ranges from 14.5 to 16.5 depending on the track.

**Badhawk** · 11-27-2012, 06:23 PM

What shock you running now ? I'm running Qa1's front and rear and my car likes full loose on the front and just the opposite out back full stiff.

**BIG CAT** · 11-27-2012, 06:35 PM

Also what were the weather conditions and post some time slips and videos if you have them.

**joelster** · 11-27-2012, 08:10 PM

I have an issue with my car not hooking at all and after talking with a few racers they all seem to think that my rims are partially to blame. Are you running a 15x8 or a 15x10 wheel? I run a 15x8 and a 27x11.50 tire. By choking the tire down to a 8" rim, i'm not getting the proper contact patch that I should be getting. I have to run my tires way underinflated compared to other people in order to get them to stick a little. Anything over 12lbs, and i'm thinking that the contact patch shrinks side-to-side.

**Stephen Ertel** · 11-27-2012, 11:32 PM

Originally Posted by BIG CAT

ok. let get a little more info and see what we come up with.

what gear?
launch rpm? 2 step?
are you spraying it? at the hit? progressive controller?
weight?
what transmission?
tubes/no tubes?

also keep in mind dead hooking is not necessarily a good thing. when you start making a good amount of power you need the tire to slip a little or it will wad up and go into shake.

here is a clip from sgmp. it shook so bad the needle came off the speedo. i run 28x10.5w's. tire psi ranges from 14.5 to 16.5 depending on the track.

4.71 gear
4000 2 step, will go 5300 on the brake
TH400 8" Converter
N/A
3300 pounds-ish. haven't weighed car
Stiffwall no tubes

Originally Posted by Badhawk

What shock you running now ? I'm running Qa1's front and rear and my car likes full loose on the front and just the opposite out back full stiff.

QA1 "R" up front, routinely goes .02-.03 quicker on 2-3 clicks depending on track conditions rather than running full soft.
Single QA1s out back on 7. Seems to like about a 4-5 on extension (but bounces BAD) and probably wants a 9 or 10 on compression if I had a DA.

Originally Posted by BIG CAT

Also what were the weather conditions and post some time slips and videos if you have them.

DA was 4200 in this video but it's the best I've got to demonstrate the issue I'm having at launch. Went 1.49 60' and 11.00 at 121.5. Front was full soft with rear on 6. You can definitely see the tire pick up speed after the tire bounces back into the wheelwell, and also the front end immediately drops.

Originally Posted by joelster

I have an issue with my car not hooking at all and after talking with a few racers they all seem to think that my rims are partially to blame. Are you running a 15x8 or a 15x10 wheel? I run a 15x8 and a 27x11.50 tire. By choking the tire down to a 8" rim, i'm not getting the proper contact patch that I should be getting. I have to run my tires way underinflated compared to other people in order to get them to stick a little. Anything over 12lbs, and i'm thinking that the contact patch shrinks side-to-side.

Running 15x10 wheels. I agree that you're hurting your contact patch on the 8 inchers, and also it makes the sidewall more flexible! I feel like I'm running mine WAY soft as well

**Tony Shepherd** · 11-28-2012, 12:55 PM

What torque arm are you running? Have you tried to lower the IC (instant center)?

**Stephen Ertel** · 11-28-2012, 04:10 PM

Running a UMI torque arm. Probably would benefit from a madman/burkhart type. Lowered to bottom hole (from top) on TA mount to lower IC which seemed to help a little but not alot. LCA in bottom hole, but as you can see the car is pretty low and there's not much angle to them.

**Badhawk** · 11-28-2012, 06:20 PM

Looks like it hooks at first then unloads and starts to spin. I would do one quick check on the torque arm bolts to see if they have loosed at all because it will cause the tires to unload after launch this I know. I also think that tire pressure is to low. What is your tire pressure starting point at the track ? I have ran slicks and radials both and never had to run that low on pressure. My car on radials well prepped track hooks on 17 - 18 psi . You could also try raising the front of the car 1in.

**Stephen Ertel** · 11-28-2012, 06:49 PM

Yea front of the car is pretty low

I started the season in the 13psi range and couldn't go faster than 1.52, it would just spin at the initial hit. At that point we started dropping tire pressure 1/2 psi until it hooked at about 11.5 psi. Next outing from watching vids we went out with TA dropped to get rid of the unloading. Went about .01 quicker to the 60', but optimal tire pressure dropped to about 11.25. Again this is hot right after I make a pass. If I'm setting pressure in the staging lanes we're talking 10.75-11.25 depending on how hot the tires are and how long of a burnout I plan on doing. Hell I've made a pass at 10.5 hot and it didn't slow down in the 60', still bounced, and only slowed down .3 mph or so on the top end.